Talks by dfhdhdhdhjr

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									                     Beam-beam: Experimental Status
                                W. Kozanecki, CEA-Saclay




         Introduction: PEP-II collision parameters & recent performance

         Interplay between e- - cloud & beam-beam issues

         Beam-beam limit studies

         Summary




W. Kozanecki                                                   PEP-II MAC Review, 9-11 Oct 03
J. Seeman, Jun 03
                               PEP-II Collision Parameters

     IP Parameter                              Design        Peak performance (Jun 03)

     C-M energy (GeV) (e+: 3.1 ; e-: 9.0)       10.58                   10.58
     Crossing angle (mrad)                       0.0                    < 1.0
     Luminosity (x 1033/cm2/s)                  3.00                    6.57

     Number of bunches                          1658                    1034
     LER current (mA, e+)                       2146                    1550
     HER current (mA, e-)                        750                    1175
     LER/HER current ratio                      2.9/1                   1.3/1

     by*/bx* (cm/cm)                          1.5 / 50            1.2 / 40+, 1.2 / 28-
     Emittance (nm-rad) (y/x)                 1.5 / 49            1.8 / 30+, 1.8 / 49-
     IP rms beam size sy/sx (mm)              4.7 / 157                 4.6 / 113

     LER tunes (x/y)                         38.64 / 36.57          38.52 / 36.57
     HER tunes (x/y)                         24.62 / 23.64          24.52 / 23.62
     Beam-beam parameter (vertical +/-)         0.03                0.082 / 0.040
     Beam-beam parameter (horizontal +/-)       0.03                0.109 / 0.040

 W. Kozanecki                                                           PEP-II MAC Review, 9-11 Oct 03
                                          Typical recent performance (May-Jun 03)




                                                                 Specific luminosity (mb-1mA-2b-2)
Luminosity (mb-1)




                                     I+ x I- (mA-2)                                                  I+ x I- (mA-2)




                        Near ½ integer (n+x/y ~ 0.52/0.57)

                             e- y-size    with  e+ current
                             e+ x-size  with  e- current
                             Total luminosity: some tune-shift saturation, but potential for more L
                             Specific luminosity scales (primarily) with e+ current

          W. Kozanecki                                                                                                PEP-II MAC Review, 9-11 Oct 03
F.-J. Decker,
   et. al.,        Interplay between e- - cloud & beam-beam issues
PAC’01, ‘03




       Bunch-by-bunch luminosity versus position           Standard luminosity pattern in spring 2003
      along the whole train. Pattern: ‘by-4’ (8.4 ns            Pattern: ‘by-3’ (6.3 ns spacing)
     spacing) with 7 additional big gaps, July 2000.
                                                         Mini-trains of 10 and 11 bunches are
    The first bunches of each mini-train have a
                                                         alternating. There is an ion gap of about 3%.
    high luminosity, which drops to 40 % of its
                                                         In this pattern each mini-train has constant
    initial value at the end of the longest train. The
                                                         luminosity (except for bunches 1+3). Solenoids
    long gaps clear the electron cloud, which
                                                         now cover most of the beam pipe in all
    slowly builds up again over along the mini-
                                                         straights and arcs.
    train. Solenoids had been installed in part of
    the straights only.
  W. Kozanecki                                                                        PEP-II MAC Review, 9-11 Oct 03
               Interplay between e- - cloud & beam-beam issues: impact

              Bunch pattern optimization: maximize Ibunch , taking into account
                   total-current budget (RF power, beam-heating problems)
                                                                          -
                   minitrain spacing (larger minigaps => better e cloud suppression)
                                                                      -
                   minitrain length (shorter minitrains => less e cloud buildup)
                   # of minitrains (fewer minitrains => fewer ‘fragile’ bunches)
                   need for current ramps at start of train (and/or minitrains)


              The severity of electron-cloud effects (for a fixed bunch pattern)
               has been steadily decreasing over the years
                   Low-field (25-35 G) solenoids now cover most of the accessible beam-
                    pipe sections. This system was upgraded this summer ( up to 3x
                    higher field in the straights + cover remaining short sections)
                   Vacuum-pipe scrubbing appears to have played a significant role
                             –
                   Some e cloud effects are no longer apparent
                         single-beam e+ blowup at high I+ no longer observed (but what once I+  ?)
                   In typical recent running, only 1st (few) bucket(s) in each minitrain
                    affected by electron cloud (if any)

W. Kozanecki                                                                             PEP-II MAC Review, 9-11 Oct 03
F.-J. Decker, et.
  al.,PAC’ 03           Interplay between e- - cloud & beam-beam issues:
                                   towards higher luminosities

                   Impact of e- cloud may be more severe once higher currents force
                    the use of a denser pattern (‘by-2’)


                                                          e- cloud




         Pattern: ‘by-2’ (4.2 ns spacing), long trains                  Pattern: ‘by-2’ (4.2 ns spacing), short trains
                           (Feb 03)                                                 [2-4-2-4.-..] (Apr 03)
                                                                     The first buckets of the duplets have the same
    20-25% luminosity loss after the first 5-10 bunches              high L, while the L of the second ones drops about
    in each train                                                    50% over 320 ns. It remains constant for several
                                                                     hundred ns, then slowly grows to nearly 75%
                                                                     before it starts dropping again.
  W. Kozanecki                                                                                     PEP-II MAC Review, 9-11 Oct 03
                                    Beam-beam limit studies



              Experimental procedure
                   Fix one beam current (typically similar to physics conditions)
                   Vary the current of the other beam from 0 to maximum possible;
                    at each setting, optimize luminosity on tunes
                   Measure L/bunch, specific luminosity Lsp, individual beam sizes s-x,y in-
                    & out-of-collision




              Diagnostics
                   Fast luminosity monitor (e+e-  e+e- g)
                   Horizontal beam sizes: synchrotron-light monitor (SLM)
                   Vertical beam sizes: SR-light interferometer




W. Kozanecki                                                                      PEP-II MAC Review, 9-11 Oct 03
                                                                                                                                                                                                                                  W.K., PEP-II
                                                                                                                                                                                                                                  Performance
                                HER b-b limit @ high e- current: I- =625 mA, I+ = 100-1400 mA, 597 bunches                                                                                                                      Workshop, Dec 00


                                  3.0
                                                                 Specific luminosity
                                                                                                                   Collisions:                                                          e+ horizontal beam size
                                                                                                                                                              2.5
                                                                                         -
                                                                                         I ~ 625 mA              LEB blowup in                                              Colliding
                                  2.5                                                      ~ 1.05 mA/b
                                                                                                                   both x & y                                               No electron beam
      L_sp (E30 mA^- 2 b^- 1)




                                  2.0
                                                                                                                  (N.B.: y blowup




                                                                                                                                     sigma_x (mm)
                                  1.5
                                                                                                                   instrumental?)
                                                                                                                                                              2.0

                                  1.0


                                  0.5
                                                                LSP drops by ~ 25-30%                              Single-beam:
                                  0.0
                                                                                                                   LEB blowup                                 1.5
                                        0.00        0.50           1.00         1.50         2.00        2.50        minimal                                        0                       500               1000                   1500
                                                             LER bunch current ( mA/b)                                                                                                         LER current (mA)



    • LEB blowup in collision >> single-beam blowup, by an amount that depends on its own current => LSP drops!
    • HER:SLM x & y size in collision flat with I+

                                                                   HER SLM x-widt h                                                                                                                      -
                                                                                                                                                                                                HER SLM y widt h
                                  1.50                                                                                                                        0.70
                                                                                         -                                                                                     Coll iding                                -
                                                Coll iding                               I ~ 625 mA                                                                                                                      I ~ 625 mA
                                                                                           ~ 1.05 mA/b                                                        0.65                                                         ~ 1.05 mA/b
                                  1.40
           SLM RMS widt h ( mm)




                                                                                                                                       SLM RMS widt h ( mm)
                                                                                                                  No indication                               0.60


                                  1.30                                                                           of b-b induced                               0.55

                                                                                                                  HER blowup
                                                                                                                                                              0.50
                                  1.20                                                                          (in this data set)
                                                                                                                                                              0.45


                                  1.10                                                                                                                        0.40
                                         0.00         0.50       1.00       1.50             2.00        2.50                                                           0                      500                1000                   1500
                                                          LER bunch current ( mA/b)                                                                                                             LER current ( mA)


W. Kozanecki                                                                                                                                                                                                   PEP-II MAC Review, 9-11 Oct 03
                                LER b-b limit @ high e+ current: I+ =1070 mA, I- =200-630 mA, 597 bunches

                                                                                                                                                          +
                                                             Specific luminosity                                                                         e horizontal beam size
                                3.0                                                                                       3.00
                                           Coll iding
                                                               +
                                                              I ~ 90 mA                                                              I+ ~ 1070 mA
                                2.5                                                                                       2.75         ~ 1.8 mA/b




                                                                                               SLM RMS width (mm)
      L_sp (E30 mA^- 2 b^- 1)




                                2.0                                                                                       2.50


                                1.5                                                                                       2.25


                                1.0                                                                                       2.00


                                0.5       +
                                          I ~ 1070 mA              LSP drops by < 5%                                      1.75
                                                                                                                                             I+ ~ 90 mA
                                            ~ 1.8 mA/b                                                                                                                                          Colliding
                                0.0                                                                                       1.50
                                      0          0.2        0.4      0.6       0.8   1   1.2                                     0           0.2         0.4     0.6     0.8        1           1.2         1.4
                                                         HER bunch current (mA/b)                                                                          HER bunch current (mA/b)



           • LER:SLM x & y size in collision >> single-beam, flat with electron current (not “naive” b-b!)
           • HER: I- dep. of x, y SLM size in collision, consistent with single-beam behavior (flat)
                                                                                                                                                               LER SLM x- widt h
                                                                                                                          3.00
                                                                                                                                         +
                                                                                                                                         I = 90 mA
                                LER b-b limit @ low e+ current: I+ = 90 mA,                                               2.75


                                       I- = 20-750 mA, 829 bunches

                                                                                                   SLM RMS widt h ( mm)
                                                                                                                          2.50                                                              +
                                                                                                                                                                                   High I

                                                                                                                          2.25


                                                                                                                          2.00


                                                                                                                          1.75


                                                                                                                          1.50
                                                                                                                                     0             0.2        0.4        0.6        0.8               1           1.2
                                                                                                                                                          HER bunch current ( mA/b)

W. Kozanecki                                                                                                                                                                   PEP-II MAC Review, 9-11 Oct 03
           Typical current-dependence of specific luminosity & beam sizes, Jan-Apr 03                                                                              6 Feb 03 data


                                                     I- vs. I+                                                                        Specific luminosity vs. I+
                        900
                                                                                                                 3.9
                        800
                                                                                                                 3.7
                        700
     HER current (mA)




                                                                                             Spec . luminosity
                                                                                                                 3.5
                        600
                        500                                                                                      3.3
                        400
                                                                                                                 3.1
                        300
                                                                                                                 2.9
                        200

                        100                                                                                      2.7

                         0                                                                                       2.5
                              0    200   400   600      800      1000   1200   1400   1600                             0    200      400   600    800    1000    1200    1400    1600
                                               LER current (mA)                                                                            LER current (mA)




                                         Horizontal beam size (SLM)                                                              Vertical beam size (interferometer)
                        2.5                                                                                      0.6
                                  LER                                                                                      LER
                                  HER                                                                            0.5       HER
                        2.0




                                                                                             sigma-y (mm)
    sigma-x (mm)




                                                                                                                 0.4
                        1.5
                                                                                                                 0.3
                        1.0
                                                                                                                 0.2

                        0.5
                                                                                                                 0.1


                        0.0                                                                                      0.0
                              0    200   400   600      800      1000   1200   1400   1600                             0    200     400    600   800    1000    1200    1400    1600
                                               LER current (mA)                                                                            LER current (mA)

W. Kozanecki                                                                                                                                              PEP-II MAC Review, 9-11 Oct 03
                   Wandering in tune space...
                  LER
                         Apr 03:
                              nx = .64
                              ny = .56
                        since May 1, 2003:
                              nx = .52
                              ny = .57



               The values quoted here are nominal, unshifted tunes


                  HER
                         Apr 03:
                              nx = .57
                              ny = .64
                        since May 1, 2003:
                              nx = .52
                              ny = .62


W. Kozanecki                                      PEP-II MAC Review, 9-11 Oct 03
                      “Before” ½ integer vs. “after”: LER beam sizes


               LER x-size (28 Apr)                   LER x-size (2 May)

                                                         + 50-60 % wrt
                                                        sx ( single-beam)


                                                                                       +8%
                                         +11 %




                     LER current (e+) [mA]                  HER current (e+) [mA]


               LER y-size (28 Apr)                   LER y-size (2 May)




                                         +7 %                                        + 12 %




W. Kozanecki         LER current (e+) [mA]                  HER current (e+) [mA]Review, 9-11 Oct 03
                                                                         PEP-II MAC
               “Before” ½ integer vs. “after”: HER beam sizes & Luminosity

                HER y-size (28 Apr)                   HER y-size (2 May)




                                                                                       + 39 %



                       LER current (e+) [mA]                  LER current (e+) [mA]


                                                      L/bunch (2 May)

                 L/bunch (28 Apr)




W. Kozanecki
               Product of bunch currents [(mA2/b)2]   Product of bunch currents [(mA2/b)2] Oct 03
                                                                            PEP-II MAC Review, 9-11
Spec. luminosity [1030 cm-2 s-1 mA-2/b]
                                                                                                   Original tunes (n+x/y ~ 0.64/0.56)
                                                                             LSP (2 May 03)
                                                                                                        e- size ~ independent of e+
                                                                                Msrd: - 25 %             current

                                                                                                         e+ size ~  with  e+ current
                                                                                Predctd: -25%
                                                                                                     
                                                                                                         (mostly x: proximity to 2/3?)


                                                                                                   Near ½ integer (n+x/y ~ 0.52/0.57)

                                                           LER current (e+) [mA]                        e- size  with  e+ current
                                                                                                        e+ size  with  e- current
                                                  Luminosity/bunch                                      Specific luminosity
                                  cm- 2s-1 b-1)




                                                    (2 May 03)
                                                                                                              scales (primarily) with
                                                                                                               e+ current
                                  (1030




                                                                                                              => HEB the ‘weaker’ beam
                                                                                                               (at that time...)
                                     L / bunch




                                                                                                        Total luminosity
                                                                                                              some tune-shift saturation
                                                                                                               (prob. HEB), but potential for
                                                                                                               more luminosity!
 W. Kozanecki
                                                       Ibunch(e-) x Ibunch(e+) [(mA/b)2]                                    PEP-II MAC Review, 9-11 Oct 03
                                                                                                        M. Baak, Sep 03
     Dynamic-b effect?

         Measurement of luminous-region size by BaBar (dimuons & Bhabha’s)
                                             1/sL = sqrt (1/s+2 + 1/s-2)

              Reduction of horizontal spot size from ~ 100 mm to ~ 70 mm.
              No changes observed in longitudinal spot size.



                                before April 28th                            after April 28th

                                                                               nx ~ 0.5

                                                                      (skipped these runs)




W. Kozanecki                                                                                    PEP-II MAC Review, 9-11 Oct 03
  Old tunes
               Tune spectra in collision       nx ~ 0.5 (June 03)




                                       ?
                         n+x

                         n+y



                         n-x


                         n-y
W. Kozanecki                               PEP-II MAC Review, 9-11 Oct 03
         y-tunes in collision, vs. e- bunch current (LEB trickle, 12 Jun 03)


                                                     LEB x-size




                  LER y-tune: b-b tune shift!                                 + 64 % wrt
                                                                           sx ( single-beam)
                 Dn+ ~ .004 for 0.81 < I- < 1.07 A

                  HER bunch current (e-) [mA/b]         HER bunch current (e-) [mA/b]




               HER y-tune: not fully
                    compensated


                 HER bunch current (e-) [mA/b]
W. Kozanecki                                                               PEP-II MAC Review, 9-11 Oct 03
               Determination of beam-beam parameters
                   from luminosity & spot-size data




W. Kozanecki                                           PEP-II MAC Review, 9-11 Oct 03
               “Measured” beam-beam parameters




W. Kozanecki                                     PEP-II MAC Review, 9-11 Oct 03
J. Seeman, Aug 03
                    Beam-beam performance summary




W. Kozanecki                                        PEP-II MAC Review, 9-11 Oct 03
                                                 Summary (I)

              Electron-cloud effects have been minimized by a combination of
               scrubbing, solenoid-suppression, and bunch-pattern optimization

              Luminosity (& background!) optimization relies on a delicate
               balance between the currents, tunes, beam-beam parameters and
               e-cloud effects as these parameters vary along each bunch train.

              Current-dependence of the spot sizes in collision (@ nx ~ 0.5)
                   LEB (HEB) sizes depend only on e- (e+) current
                   sy(e-) grows by 30-70% wrt the e- single-beam size
                         30-40% is more typical of recent (stable) running : mostly ‘spontaneous’ ?
                   sx(e+) grows by a factors of 1.5 to > 2 wrt the e+ single-beam size
                         50-60% is more typical of recent (stable) running: ‘spontaneous’ or effective
                          optimum?
                   offline analysis of luminous region size (using dimuons & Bhabh’as)
                         corroborates the expected reduction in IP x-spot size (  simulation?)
                         ...but the observed variations of IP spot size are not always consistent with
                          the measured current-dependence of individual e+ and e- beam sizes

W. Kozanecki                                                                               PEP-II MAC Review, 9-11 Oct 03
                                                  Summary (II)

              Beam-beam parameter measurements
                   some tune measurements in collision are difficult (esp. LER nx)
                   extracting x (or limits thereon) from L and s(SL)+,- x,y promising, but...
                         it needs better control of SLM/interferometer systematics
                         it would greatly benefit from the ability to ‘translate’ SL sizes into IP sizes
                         the interpretation/analysis is complicated by dynamic-b effects.
                         1 measurement of vertical LEB beam-beam tune-shift vs. HER current! but
                          interpretation not straightforward..
                         can we gain more from such parasitic monitoring?


              New diagnostics being commissioned
                   gated cameras in HER & LER
                   on-line measurements of IP positions & spot sizes by BaBar
                   gated tune monitor

              PEP-II has recently achieved, near the ½ integer, beam-beam
               parameters xx/ xy of about .109 / .082 (.040 / .040) in the LER (HER)


W. Kozanecki                                                                                   PEP-II MAC Review, 9-11 Oct 03
               Spare slides




W. Kozanecki                  PEP-II MAC Review, 9-11 Oct 03
              In contrast to ‘classical’ single-ring collider,


                   e+x,y  e-x,y (and b+x,y  b-x,y only) => s+x,y  s-x,y


                   interpreting luminosity in terms of x requires additional
                    knowledge and/or assumptions on individual IP spot sizes


                   energy-transparency conditions
                    x+x,y = x-x,y <===> I+b E+ = I-b E-
                      (provided b           = b x,y , e         = e x,y , n             = n x,y...)
                                  +             -     +            -          +             -
                                      x,y                 x,y                     x,y

                         largely violated in PEP-II
                                                                                                      +   –
                         best performance repeatedly achieved with I / I ~ 1.3
                          (more typically 1.7 – 2, not 2.9!)




W. Kozanecki                                                                                                  PEP-II MAC Review, 9-11 Oct 03
                        Typical performance since Run 4 startup




                                            Specific luminosity (mb-1mA-2b-2)
 Luminosity (mb-1)




                     I+ x I- (mA-2)                                             I+ x I- (mA-2)




W. Kozanecki                                                                                     PEP-II MAC Review, 9-11 Oct 03
                    Interplay between e- - cloud & beam-beam issues (2)

              At high I +, e- cloud strength varies along minitrain =>
                     +
                   e beam size varies (long range + within train) => Luminosity varies



                                                                              Gated-camera measurements
                                                                               (2001 data, 4-by-22 pattern)


                                                                                R. Holtzapple, PEP-II Performance
                                                                                       Workshop, Jan 2002




                     -                                            -
                   e beam-beam tune-shift varies (=> e beam size may vary ??)
                   tunes optimized on the average only =>
                            slight L loss
                            ‘raining’ buckets (rapid loss of charge, background spikes, flip-flop)
                            electron-cloud enhanced beam-beam blowup of the e+ beam

W. Kozanecki                                                                                      PEP-II MAC Review, 9-11 Oct 03
R. Holtzapple, et. al., SLAC-PUB-9238
             (2001 data)                Beam-beam flip-flop


                                                       Near the top of a fill:
                                                            Several LER bunches have
                                                             reduced beam size (~30%
                                                             reduction in beam size)
                                                            Several bunches - typically near
                                                             the head of the train - have ~ ½
                                                             L
                                                            2 states of low-luminosity
                                                             bunches: they have either
                                                             reduced LER current or reduced
                                                             LER beam size
                                                                  Ib+ = low; Ib- = average
                                                                  Ib+, Ib- = average; sx, y+ = small.
                                                                   Small LER bunches + low L
                                                                   implies transverse blow-up of
                                                                   the e- beam, since bunch
                                                                   currents are not particularly low
                                                                   for these.



  W. Kozanecki                                                                      PEP-II MAC Review, 9-11 Oct 03
               Beam-beam flip-flop (2)


                                Single Bunch Transition
                                 to low-luminosity state
                                     Initially at average beam size
                                     Luminosity dropped when rings
                                      were filled
                                     The bunch experiences a
                                      sudden change in
                                      luminosity/beam size
                                     This bunch went from one
                                      unstable state (low luminosity /
                                      small x, y) to the other unstable
                                      state (short lifetime)
                                           Transition between states is
                                            fast (~0.5 sec.)
                                           Horizontal beam size oscillation
                                            accompanies the transition




W. Kozanecki                                               PEP-II MAC Review, 9-11 Oct 03
                                   Beam-beam flip-flop (c’td)

                                               Possible Explanation of Beam Size Flip-
                                                Flop Dynamics
                                                    The LER bunches at the front of the train
                                                     have a smaller transverse beam size
                                                     (lower electron cloud density). These
                                                     small (strong) LER bunches blow-up the
                                                     HER bunches.
                                                    The resulting tune shift for the these LER
    Start of the store (high I): L/bunch
                                                     bunches is smaller than “normal”, and as
 (almost) uniform throughout each train.
                                                     a result, they have a horizontal tune
                                                     located near a resonance which gives
                                                     them a shorter lifetime.
                                                    The LER bunches lose charge. Eventually
                                                     the HER becomes strong enough to flop
                                                     itself, and the LER bunch, back to
                                                     “normal” size.
                                                    To confirm this theory, a 2nd gated
                                                     camera has been installed in the HER
                                                     and is being commissioned.
End of the store (low I): single-bunch L
                                  st
W. dropouts are prevalent in the 1 few
   Kozanecki                                                                     PEP-II MAC Review, 9-11 Oct 03
                  trains
W. Kozanecki   PEP-II MAC Review, 9-11 Oct 03
                   HER b-b limit (continued)                                                                                          By-5 - 1/50th, 597 bunches , b*y = 1.25, July 00

                                                                                                                 Collisions:                                                                    -
                                                                                                                                                                                       LER SLM y width
                                                             LER SLM x- widt h
                                    3.00
                                                                                        -
                                                                                                               LEB blowup in                                  0.76
                                                                                                                                                                                                                    -
                                               Coll iding                               I ~ 625 mA                                                                       Coll iding                             I ~ 625 mA
                                    2.75       Separ ated                                 ~ 1.05 mA/b
                                                                                                                 both x & y                                              Separ ated                               ~ 1.05 mA/b
                                                                                                                                                              0.72
                                               No HER                                                                                                                    No HER
                                                                                                                (N.B.: y blowup
       SLM RMS widt h ( mm)




                                                                                                                                       SLM RMS widt h ( mm)
                                    2.50
                                                                                                                instrumental??)                               0.68
                                    2.25
                                                                                                                                                              0.64
                                    2.00
                                                                                                               Single-beam or                                 0.60
                                    1.75
                                                                                                                 separated:
                                    1.50                                                                        LEB blowup                                    0.56
                                           0                500                1000                     1500                                                         0                500                1000                   1500
                                                             LER current ( mA)                                    minimal                                                              LER current ( mA)



    • LEB blowup in collision >> single-beam blowup, by an amount that depends on its own current => LSP drops!
    • LEB blowup with both beams present but out of collision, is similar to single-beam blowup

                                                              HER SLM x-widt h                                                                                                                  -
                                                                                                                                                                                       HER SLM y widt h
                                    1.50                                                                                                                      0.70
                                               Coll iding                               -                                                                                Coll iding                             -
                                                                                        I ~ 625 mA                                                                                                              I ~ 625 mA
                                                                                          ~ 1.05 mA/b                                                         0.65                                                ~ 1.05 mA/b
                                    1.40
             SLM RMS widt h ( mm)




                                                                                                                 No indication


                                                                                                                                    SLM RMS widt h ( mm)
                                                                                                                                                              0.60

                                    1.30
                                                                                                                of b-b induced                                0.55
                                                                                                                 HER blowup
                                                                                                                                                              0.50
                                    1.20
                                                                                                               (in this data set)
                                                                                                                                                              0.45

                                    1.10                                                                                                                      0.40
                                           0                500                  1000                   1500                                                         0                500                1000                   1500
                                                             LER current ( mA)                                                                                                         LER current ( mA)


W. Kozanecki                                                                                                                                                                                         PEP-II MAC Review, 9-11 Oct 03
                              LER b-b limit @ low e+ current: I+ = 90 mA, I- = 20-750 mA, 829 bunches

                                                         Luminosit y/bunch                                                                                         Specific luminosity
                               0.25                                                                                                 3.0
                                                                                                                                                                                                    +
                                                                                                                                                                                                    I = 90 mA
                                                                                                                                    2.5
                                0.2




                                                                                                          L_sp (E30 mA^- 2 b^- 1)
        L/bunch ( E30/bunch)




                                                                                                                                    2.0
                               0.15

                                                                                                                                    1.5
                                0.1
                                                                                                                                                              LSP drops by ~ 10-15%
                                                                                                                                    1.0

                               0.05
                                                                                                                                    0.5

                                  0                                                                                                 0.0
                                      0        0.02      0.04       0.06        0.08         0.1   0.12                                    0            0.2       0.4         0.6                  0.8           1
                                                  ( I+/b) * (I-/b) ( mA^2/bunch)                                                                         HER bunch current (mA/bunch)



                                          • LER: definite, but moderate, increase in both x,y SLM sizes with electron current (as expected)
                                          • HER: I- dep. of x, y SLM size in collision, consistent with single-beam behavior

                                                            LER SLM x- widt h                                                                                                -
                                                                                                                                                                    LER SLM y width
                               3.00                                                                                                 0.76
                                           +                                                                                                       +                                           +
                                           I = 90 mA                                                                                               I = 90 mA                          High I
                               2.75
                                                                                                                                    0.72
       SLM RMS widt h ( mm)




                                                                                                          SLM RMS widt h ( mm)
                               2.50                                                      +
                                                                                High I
                                                                                                                                    0.68
                               2.25

                                                                                                                                    0.64
                               2.00


                               1.75                                                                                                 0.60


                               1.50                                                                                                 0.56
                                      0         0.2        0.4       0.6           0.8        1     1.2                                        0        0.2       0.4      0.6        0.8                1      1.2
                                                       HER bunch current ( mA/b)                                                                               HER bunch current ( mA/b)


W. Kozanecki                                                                                                                                                                     PEP-II MAC Review, 9-11 Oct 03
                                LER b-b limit @high e+ current: I+ =1070 mA, I- =200-630 mA, 597 bunches

                                                                                 Specific luminosity                                                                                 +
                                                                                                                                                                                 e horizontal beam size
                                           3.0
                                                           Coll iding                                                                                3.00
                                                                                   +
                                                                                  I ~ 90 mA                                                                     I+ ~ 1070 mA
                                           2.5
                                                                                                                                                     2.75         ~ 1.8 mA/b




                                                                                                                             SLM RMS width (mm)
      L_sp (E30 mA^- 2 b^- 1)




                                           2.0
                                                                                                                                                     2.50

                                           1.5                                                                                                       2.25

                                           1.0                                                                                                       2.00


                                           0.5         +
                                                       I ~ 1070 mA                       LSP drops by < 5%                                           1.75
                                                         ~ 1.8 mA/b                                                                                                   I+ ~ 90 mA
                                                                                                                                                                                                                     Colliding
                                           0.0                                                                                                       1.50
                                                   0             0.2            0.4      0.6       0.8        1       1.2                                   0        0.2             0.4     0.6     0.8        1    1.2         1.4
                                                                             HER bunch current (mA/b)                                                                                  HER bunch current (mA/b)



           • LER:SLM x & y size in collision >> separated, but both are flat with electron current (not “naive” b-b!)
           • HER: I- dep. of x, y SLM size in collision, consistent with single-beam behavior (flat)

                                                                                    LER SLM x- widt h                                                                                               -
                                                                                                                                                                                           LER SLM y width
                                                3.00                                                                                                 0.76
                                                              Coll iding                                                                                            Coll iding
                                                2.75          Separ ated                                                                                            Separ ated
                                                                                                                                                     0.72
                                                             +
                                                            I ~ 1070 mA
                         SLM RMS widt h ( mm)




                                                                                                                              SLM RMS widt h ( mm)
                                                2.50          ~ 1.8 mA/b
                                                                                                                                                     0.68
                                                2.25
                                                                                                                                                     0.64
                                                2.00


                                                1.75                                                                                                 0.60                                                           +
                                                                       +
                                                                                                                                                                                 +
                                                                                                                                                                             I ~ 90 mA                              I ~ 1070 mA
                                                                   I ~ 90 mA
                                                                                                                                                                                                                      ~ 1.8 mA/b
                                                1.50                                                                                                 0.56
                                                       0               0.2         0.4        0.6       0.8       1    1.2                                      0          0.2          0.4      0.6        0.8            1           1.2
                                                                              HER bunch current ( mA/b)                                                                              HER bunch current ( mA/b)
W. Kozanecki                                                                                                                                                                                              PEP-II MAC Review, 9-11 Oct 03
                     Comparison of individual beam sizes with luminous-region measurements                                                                           6 Feb 03 data


                               Horizontal size of luminous region (BBR+ CapSy)                                                Vert. size of lum. region (L_sp + CapSy)
                     120
                                 sig_xL(B)                                                                         5.00
                                 CapSX/2                                                                                      sig_yL(Lsp)
                     110                                                                                           4.75




                                                                                         sig_yL (L_sp) (microns)
                                                                                                                              CapSY/2
  sig_xL (microns)




                                                                                                                   4.50
                     100
                                                                                                                   4.25
                     90                                                                                            4.00

                                                                                                                   3.75
                     80
                                                                                                                   3.50
                     70
                                                                                                                   3.25

                     60                                                                                            3.00
                       100            350      600        850      1100    1350   1600                                 100          350     600      850      1100     1350      1600
                                                 LER current (mA)                                                                             LER current (mA)




                                             Horizontal beam size (SLM)                                                            Vertical beam size (interferometer)
                      2.5                                                                                          0.6
                                LER                                                                                          LER
                                HER                                                                                0.5       HER
                      2.0


                                                                                         sigma-y (mm)
      sigma-x (mm)




                                                                                                                   0.4
                      1.5
                                                                                                                   0.3
                      1.0
                                                                                                                   0.2

                      0.5
                                                                                                                   0.1


                      0.0                                                                                          0.0
                         100          350      600         850      1100   1350   1600                                100          350      600      850     1100      1350      1600
                                                     LER current (mA)                                                                         LER current (mA)
W. Kozanecki                                                                                                                                                PEP-II MAC Review, 9-11 Oct 03
      Very little HEB current-dependence of either LER or HER spot size
      LEB current-dependence : for 1.1 < I+ < 1.85 A,
              LER             x-size:      + 20%
                               y-      :    + 10-15 %
              HER             x-size:      + 6% (but: large spread)
                               y-      :    + 10% (but: large spread; may be consistent with ~0)
              Lsp                     :    - 30% (measured)
                                       :    - 21% (predicted from spot size variations)



                                                        Lsp


                                                                          Lsp =2.9 predicted from
                                                                           HER/LER beam size
                                                                             relative variation




         5 Apr 03 data


W. Kozanecki             LER bunch current (mA/bunch)                                      PEP-II MAC Review, 9-11 Oct 03
                    Specific luminosity vs. beam currents


               I+                                                      LSP

                                                              Msrd: - 25 %
                                                              Predctd: -25%




                              I- (mA)                                   I+ (mA)

                                                                          LSP




W. Kozanecki
                                                                    I- (mA)
                                                            PEP-II MAC Review, 9-11 Oct 03
                            LEB size vs beam currents


               LER x-size                       LER y-size




               LER x-size                       LER y-size




                                +8%
                                                                        + 12 %




W. Kozanecki                                                 PEP-II MAC Review, 9-11 Oct 03
                        “Before” ½ integer vs. “after”: LER beam sizes


               LER x-size (28 Apr)                     LER x-size (2 May)




                                                                                         +8%
                                      +11
                                       %




               LER y-size (28 Apr)                     LER y-size (2 May)




                                     +7 %                                              + 12 %




W. Kozanecki                                                                PEP-II MAC Review, 9-11 Oct 03
         y-tunes in collision, vs. e- bunch current (LEB trickle, 12 Jun 03)




                  LER y-tune: b-b tune shift!
                                                     LER y-tune knob
                 Dn+ ~ .004 for 0.81 < I- < 1.07 A

                  HER bunch current (e-) [mA/b]        HER bunch current (e-) [mA/b]




                                                     HER y-tune knob




               HER y-tune: not fully
                    compensated


                 HER bunch current (e-) [mA/b]         HER bunch current (e-) [mA/b]
W. Kozanecki                                                               PEP-II MAC Review, 9-11 Oct 03
                                                          M. Baak, Sep 03
         Luminous spot sizes
          vs. beam currents


     •         No apparent
               dependence of the
               horizontal luminous     after April 28th
               size on LER or HER         nx ~ 0.5
               currents




     •         No apparent
               dependence of the
               longitudinal luminous
               size on LER current.




W. Kozanecki                                    PEP-II MAC Review, 9-11 Oct 03
                                               Current-dependence of measured SL spot sizes
                                                      LER X spot size                                                                           LER Y spot size
                        2.5                                                                                        0.34


                                                                                                                   0.33
                         2

                                                                                                                   0.32
     Spot size (mm)




                                                                                                  Spot size (mm)
                        1.5

                                                                                                                   0.31

                         1
                                                                                                                    0.3

                        0.5
                                                                                    LER_Sx                         0.29                                                         LER_Sy
                                                                                    sLx_f                                                                                       sLy_f
                         0                                                                                         0.28
                              0.8             0.9              1             1.1            1.2                           0.8            0.9           1             1.1                1.2
                                                    HER bunch current (mA/b)                                                                HER bunch current (mA/b)




                                                      HER X spot size                                                                           HER Y spot size
                        0.64                                                                                        0.4
                                     HER_Sx                                                                                     HER_Sy
                        0.63         sHx_f                                                                                      sHy_f
                                                                                                                   0.35
                        0.62


                                                                                                  Spot size (mm)
       Spot size (mm)




                                                                                                                    0.3
                        0.61

                         0.6
                                                                                                                   0.25

                        0.59
                                                                                                                    0.2
                        0.58

                        0.57                                                                                       0.15
                               1.1             1.3             1.5            1.7           1.9                           1.1            1.3             1.5            1.7              1.9
                                                     LER bunch current (mA/b)                                                                  LER bunch current (mA/b)
W. Kozanecki                                                                                                                                                      PEP-II MAC Review, 9-11 Oct 03
               Current-dependence of estimated IP spot sizes




W. Kozanecki                                               PEP-II MAC Review, 9-11 Oct 03
               Comparison of fitted & measured L & LSP




W. Kozanecki                                             PEP-II MAC Review, 9-11 Oct 03
                                                                               But it does not always work so well...
                                                                  HER X spot size                                                                                             HER X spot size
                                 0.65                                                                                                            0.65
                                                 HER_Sx                                                                                                          HER_Sx
                                 0.64            sHx_f                                                                                           0.64            sHx_f


                                 0.63                                                                                                            0.63
        Spot size (mm)




                                                                                                                      Spot size (mm)
                                 0.62                                                                                                            0.62

                                 0.61                                                                                                            0.61

                                  0.6                                                                                                              0.6

                                 0.59                                                                                                            0.59

                                 0.58                                                                                                            0.58
                                           0.8             1       1.2         1.4       1.6       1.8           2                                         0.8           1     1.2         1.4        1.6       1.8           2
                                                                  LER bunch current (mA/b)                                                                                   LER bunch current (mA/b)


                                                                      3 May                                                                                                    5-6 Jun
                                                                 Specific luminosity                                                                                         Specific luminosity
                                 4.5                                                                                                             4.5
                                                                                                       L_SP
                                 4.3                                                                                                             4.3
                                                                                                       L_sp_c
                                 4.1                                                                                                             4.1




                                                                                                                      L_sp (1 0^30 b^-1 mA^-2)
      L_sp (10 ^30 b^-1 mA^-2)




                                 3.9                                                                                                             3.9

                                 3.7                                                                                                             3.7

                                 3.5                                                                                                             3.5

                                 3.3                                                                                                             3.3

                                 3.1                                                                                                             3.1

                                 2.9                                                                                                             2.9
                                                                                                                                                                                                                    L_SP
                                 2.7                                                                                                             2.7
                                                                                                                                                                                                                    L_sp_c
                                 2.5                                                                                                             2.5
                                       0                 10000      20000        30000         40000          50000                                    0             10000      20000        30000          40000          50000
                                                                         Time (sec)                                                                                                  Time (sec)
W. Kozanecki                                                                                                                                                                                      PEP-II MAC Review, 9-11 Oct 03

								
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