Beam Transport Target Systems

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					              Beam Transport & Target Systems

                        BTS Success
                          Novosibirsk
                           24/5/2005 18:15
                              300 A




P.-R Kettle             MEG Review July 2005    1
                           Beam Line & Target Status
 Topics to be Addressed:

 •    Beam Transport System
              (i) Degrader / BTS optimization
              (ii) Layout - fixed

 • Beam Line Components Status
     * (i) Separator- undergoing HV-conditioning
     * (ii) Beam Transport Solenoid BTS – being commissioned E5
              (iii)   Vacuum System (beam line + BTS)- being assembled
              (iii)   Cryogenic Transfer Lines LN2 LHe – installed

 •     He-Bag & Target Systems

 •     Schedule 2005

 •     Summary + Critical Points


P.-R Kettle                          MEG Review July 2005                2
              Beam Transport System
                     Status




P.-R Kettle           MEG Review July 2005   3
                            Beam Transport System
                                                        As previously reported
                                                        Beam Line Commissioning
                                                        2004 concluded with
                                                        phase space measurements
                                                        In vacuum up to the
                                                        INJECTION into the BTS
                                                            (without BTS !!!)

Using real data    SIMULATE Phase Space & Back-Track to Triplet II
                   Forward-Track with Fringe Field of BTS + COBRA up to Target in COBRA
                                       using GEANT




                                                                          “waist”



Input Data to GEANT to study
Degrader/Target + BTS/COBRA layout

 P.-R Kettle                          MEG Review July 2005                                 4
                                               Degrader + BTS/COBRA Optimization
Studied:
1.                       BTS/COBRA Distance vs. Degrader segmentation & Bfield
                             (Cryo.-Cryo. Gap): minimum (200 mm),                                       intermediate(300 mm),                                     maximum(400 mm)
2.                       BTS/COBRA Polarity (+/+), (-/+) radial de-focussing/focussing

                             Beam Sigma at COBRA Focus vs. BTS Bfield & Gap
                                                                                                                            Beam Sigma at COBRA Focus vs. BTS Bfield
                  18.0                                                                                                                    Normal Gap
                  17.0
                                         Max. B+ve                                                                19.0
                  16.0
                                                                                                                  18.0                                                                DDDD
Beam Sigma [mm]




                  15.0                                                                                            17.0                                                                DDD+W




                                                                                                Beam Sigma [mm]
                                                                                                                  16.0                                                                DD+W+D
                  14.0           Gap
                                                                                                                  15.0
                                 
                                                                                                                                                                                      D+W+DD
                  13.0                                              M aximum (-/+) DDD+W                          14.0                                                                W+DDD
                                                                    Intermediate DDD+W                            13.0
                  12.0
                                                                    M inimum DDD+W                                12.0
                                                                    M aximum (+/+) DDD+W
                  11.0
                                               Max. B-ve                                                          11.0

                  10.0                                                                                            10.0
                      -3.8      -3.7    -3.6     -3.5      -3.4   -3.3      -3.2         -3.1                            -3.9   -3.8   -3.7   -3.6   -3.5       -3.4   -3.3   -3.2   -3.1      -3

                                                BTS Bfield [kG]                                                                                      BTS Bfield [kG]




• Weak Gap dependence (4%)                                                 • Gap 400 mm                                                • strong degrader segmentation
• strong polarity dependence                                               • -/+ Polarity                                                 dependence (25%)
                    (15%)                                                  • Degrader BTS

                  P.-R Kettle                                                      MEG Review July 2005                                                                                             5
               Beam Transport System Layout




                                                                    Distances Fixed: Platform + COBRA
                                                                     surveyed into Zone
                    Trip I         Trip II
                                                     COBRA
              ASC            Sep                             Y




                                                             X
                                              BTS




P.-R Kettle                                  MEG Review July 2005                                  6
              Beam Line Component
                    Status




P.-R Kettle          MEG Review July 2005   7
                         Component Status: Separator
                MEG Vertical Separator
Delayed by ~ 8 weeks:                                         Beam
• due to HV feed-through problems – now solved                Upstream
• HV (+ve) supply changed to (–ve) one - technical            Side
     HV-electrode on top, want e+ deflected down
!!!      HV Conditioning Tests in front of E5     !!!
            expected ready for beam time

                 Properties                                               2371 mm
                Vmax 200kV
                Dplates 19cm
                Leff    70cm




April 2005                          May 2005                  June 2005

  P.-R Kettle                          MEG Review July 2005                         8
                         Component Status BTS
                        Beam Transport Solenoid BTS
              Schedule delayed by ~ 7 weeks:
              • 5 weeks delay during manufacture
              • 2 weeks transportation (papers stolen at Russian border)
                               nevertheless
                !!! Novosibirsk Crew did a “Very Good Job”       !!!
                            BTS arrived PSI 8th July

    Coil Manufacture - epoxying                 Performance Tests – Novosibirsk
                                                                Novosibirsk Crew




End March 2005                                   End May 2005

P.-R Kettle                        MEG Review July 2005                            9
                  BTS Performance Tests - Novosibirsk
       Performance Tests                                        Flexible Cryogenic Design via:
 BINP Novosibirsk 21-29th May 2005                              • dedicated transfer lines (PSI)
Tested:                                                         • dewar operation (BINP)
• maximum Design Current (300 A)                                • both (emergency)
• Quench Detection / Protection Systems
 (fast switch 30 ms + 0.7 Shunt Resistor 90% power load)
• Linearity Response (max. dev. ~ 0.4%)
• LHe Consumption Rate (3.6 l/hr)
• Magnetic Field Measurements




    0.7 Shunt Resistor        All measurements &
                                  tests successful
                                      except
                               Bfield measurements
                               which were influenced
                                        by
                               steel support structure




  P.-R Kettle                            MEG Review July 2005                                10
                     Results BTS Performance Tests - Novosibirsk
                    Coils:                                                                                                        Main Specifications
                    • double layer                                                                                                     LCryo                    2810 mm
                    •    cable dia. 1.23 mm                                                                                            DBore                     380 mm
                    •    1865 / 1980 windings                                                                                          DCoil                    469.5 / 466.2 mm
                    •    40% NiTi
                                                                                                                                       LCoil                    2630 mm
                    •    RRR ~ 100
                                                                                                                                       BMax                       <0.55 T
                                                                                                                                       Imax                     300 amps
                  BTOT deviates from expected
                                                                                                                                       LMax                        0.98 H
                  due to Steel support structure
                                                                                                                                       EStored                      44 kJ
                  !!! Needs to be re-measured at PSI !!!
                          “Acceptance Tests”                                                         Linearity (B vs. I) better 0.4% up to 300 A
                                Field Map BTS Test 200A Btot vs. Z                                                                           Component Field Linearity
                  4000
                                                                                                                      8000

                  3500                                                                                                                 y = 18.539x + 8.8368                                   Bx
                                                                                                                      6000
                                                                                                                                              R2 = 1                                          By
                  3000                                                     Theoretical                                4000
                                                                                                                                                                                              Bz
Bfield Btot [G]




                  2500                                                     Measured
                                                                                                     BTS Bfield [G]   2000                                                                    Bsum

                  2000                                                                                                                                                                        Linear
                                                                                                                         0
                                                                                                                                                                                              (Bz)
                                                                                                                              0   50            100             150        200    250   300   Linear 350
                  1500
                                                                                                                      -2000                                                                   (Bsum)

                  1000
                                                                                                                      -4000
                                                                                                                                             y = -18.538x - 8.7679
                  500
                                                                                                                      -6000                            R2 = 1
                    0
                    -600        -100            400                 900                  1400                         -8000

                                        Axial Position wrt Cryostat [mm]                                                                                        BTS Current [A]




          P.-R Kettle                                                                      MEG Review July 2005                                                                                      11
                            BTS Preparations PSI
        Preparations for BTS Installation in E5
                                                               Valve Chamber
• cryogenic lines for LHe & LN2 ready for connection
• valve chamber ready for mounting on BTS                      Couples BTS to
• power supply tested & ready                                  LHe transfer Line
                                                                  contains
                                                               Joule-Thompson
                                                               Valves for control


                                                                            LHe Transfer
Refrigerator unit
                                                                            Line
Above E5


   LHe line




                                                           LHe Transfer Line




  P.-R Kettle                       MEG Review July 2005                                   12
                                        BTS arrival PSI
          8th July 2005                      BTS arrival PSI                    14th July 2005
                                              *** 8th July ***                       E5
               “ On route PSI”
                                           Acceptance Tests
                ~ 6500 km
              Novosibirsk - PSI        • assembly / survey                     Valve
                                       • vacuum / leak tests                 chamber
                                       • cryogenic installation 
                                                                                                 LN2
                                       • electrical installation 
                                       • cool-down
                                       • quench detection /
                                              protection tests
                                       • Bfield measurements


                                            !!! Problems !!!
                                     • welding joint tower / cryostat
                                          damaged in transport
                                           Re-welded OK
                                     • cryogenic connection valve-
                                       chamber / LHe transfer line
                                     not compatible
                                           To workshops                *** Dmitry Reports: 18th July
                                                                        11:00 coil superconducting
                                      Use dewar system LHe              20:00 *** 283A reached ***
                   “ On route E5”                                             (nominal ~ 200A)


P.-R Kettle                                 MEG Review July 2005                                 13
              He-Bag & Target System
                    Status




P.-R Kettle           MEG Review July 2005   14
                         He-Bag / Target System - General

                         (I) Desired Beam Characteristics

•      transport maximum number µ+ to the target (vacuum / He, large ΔP)
•      maximize µ+ stopping-rate in the target (small ΔP, vacuum /He)
•      minimize beam spot size & multiple scattering (vacuum / He, degrader close to target)
•      minimize background from decays or Bremsstrahlung (degrader far from away, vacuum / He)

                          (II) Desired Target Requirements

•     depolarizing target (isotropic e+, non-metal)
•     minimum target size (low-Z)
•     minimize material traversed by decay e+ &  (slanted target)
•     minimize generation of annihilation photons (large X0, low-Z e.g. CH2)



                                                                              
                                   Consequences:
                       • vacuum window interface to COBRA
                       • He-atmosphere inside COBRA
                       • slanted, non-metallic, low-Z, large X0 target



    P.-R Kettle                             MEG Review July 2005                            15
                                         COBRA-Environment
                               (III) COBRA Environment Requirements
                   • thin vacuum window at entrance COBRA (190µ Mylar)
                   • safety measures against vacuum window rupture (safety seals !!!)
                   • must maintain DC & TC dimensions & insertion concepts
                   • stringent constant differential He-pressure between DCs & COBRA (~few µb)
                   • no He-leakage to TC PMs (N2-Bag)
                   • frequent / less frequent access to Downstream side for calibration
                               & monitoring purposes ( e.g. Cockroft-Walton, - CEX)
                   • possibility to exchange targets ( LiF, LH2, CH2 etc.)

                                                                                                 End
                       Consequences                        Vacuum              COBRA
                                                                                                 Cap
1.    Thin beam line Vacuum Window                         window                                DS
2.    COBRA End-Cap Flanges + HE-seals (US,DS)
3.    Target Insertion Tube & support                                         Target System
       system (separate He-environment) (TISS)
4.    Target System (TS)
                              
 *** PSI staged Engineering Design Project                                    Target Insertion
     started – design & construction ***                                          tube
 (i)US-flange, (ii) DS-flange, (iii) TISS, (iv) TS
– design & Construction ready – Feb. 2006                      End
                                                               Cap
                                                               US
     P.-R Kettle                                  MEG Review July 2005                           16
                  End-Cap Flanges & He-Bag seals
                 Engineering Design Concept Upstream End-Cap

                                     Design
COBRA                           Allows open
                                access to TCs +
                                   withdrawal
                                without affecting
                                He-environment         COBRA
                                                       cryostat
                                 Mounting
                         Beam   1.  N2-Bag                                   US
                                2.  TC-rails                               End-Cap
                                3.  End-Cap +
                                    He-Bag
                                                                           Flange
                                4. TCs
                                5. Beam pipe
                                    with BTS                      He-Bag
                                6. Couple He-
                                    Bag rings to
                                   vac. window


                                 He-Bag
                                composition         He-Bag
                                                    inner
        N2-Bag    Beam           Sandwich           sealing Rupture        Insertion
                  pipe          CH2/EVAL/CH2        rings   Seals            TCs


P.-R Kettle                     MEG Review July 2005                           17
                                                                                                                                      Target Optics - momentum
Goal: maximize stop-density (min. target size)                                                                                                                                              Momentum-Spectrum:
Question: optimum beam momentum?                                                                                                                                                         Data:
Answer: 28.2 MeV/c                                                                                                                                                                       whole Beam Line optimized for each data
                                                                                                                                                                                         point + 2-D Scan for each point !!!
                                                                            Muon Range-Momentum Dependence CH2
                                                                                                                                                            + range vs. P
                                                                                                                                                                                         Theory:
                                                               1400.0
                                                                                                                                                        (fixed P/P~ 7.7% FWHM)          -Kinematic Edge (29.79 MeV/c)
                                                                                       R= 0.0108 P3.4752           P3.5
                                                               1200.0
                                                                                                                                                                                         Theoretical func. P3.5 folded with
                                 Muon Range in CH2 [microns]




                                                                                           rho 2 = 1
                                                                                                                                                        • straggling ~11 %
                                                               1000.0

                                                                                                                                                        • characteristic P3.5
                                                                                                                                                                                         Gaussian ΔP/P + Const. Cloud µ+
                                                                800.0

                                                                                                                           Range R [m icrons]
                                                                                                                                                                                         contribution  Fitted to data
                                                                600.0                                                      SigR [m icrons]


                                                                400.0
                                                                                   straggling ~ 11%
                                                                200.0


                                                                  0.0
                                                                     25.5          26.0        26.5         27.0        27.5          28.0      28.5
                                                                                                M uon M omentum [M eV/]



                                                                    Muon Stopping Rate vs. Momentum (400 micron Tg)

                                               1.050

                                                                            Rel.  stops
 Norm. Relative Muon Stopping Rate




                                               1.000


                                               0.950
                                                                                                                                                           + Stopping Rate vs. P
                                                                                                                                      Norm.
                                               0.900
                                                                                                                                                         (fixed P/P~ 7.7% FWHM
                                               0.850
                                                                                                                                      -stops
                                                                                                                                                         fixed 400 CH2 target)                  2/dof = 0.94
                                                                                                                                                         • as p > relative stop rate <
                                                                                                                                                                                                 Pcent = (28.16  0.02) MeV/c
                                               0.800
                                                                            P3.5                                   Muon Stopping Fraction

                                                                                                                   P**3.5 Rate Dep.                                                              P/P = (7.7  0.3) % FWHM
                                               0.750
                                                                                                                                                         • as p > beam rate >
                                                                                                                                                                                                 Pbeam = (28.2  0.9) MeV/c
                                                                                                                   Rel. Muon Stopping Rate

                                               0.700                                                               Pow er (Rel. Muon
                                                                                                                   Stopping Rate)
                                                                 25.50         26.00         26.50         27.00
                                                                                              Muon Momentum MeV/c
                                                                                                                   Pow27.50
                                                                                                                   Fraction)
                                                                                                                                    28.00
                                                                                                                       er (Muon Stopping        28.50
                                                                                                                                                            Optimal Stop Rate
                                                                                                                                                             at P~28.2 MeV/c

                                P.-R Kettle                                                                                                                MEG Review July 2005                                               18
                                    Target Optics - degrader
                    Many solutions studied – 2 main categories
                                                                            Single Node
                                                                               SNM
                    DMN                                                                           BTS
                                       (1) DNM – Solution
                            COBRA         (190 Mylar Window)               Double Node
        BTS
                                       • BTS / COBRA unlike                    DNM
                                         polarities
                                       • BBTS = -3.55 kG                                           P ~ 4.2 MeV/c
   Beam envelope (cm)
                                       • degrader 480 CH2 at                                              P ~ 2 MeV/c
                                         centre BTS                                               P ~ 4.5 MeV/c
                                           beam  ~ 12.5 mm

                                             Transmission
                                               Efficiency                          Momentum Profile (MeV/c)
                                               • TBTS+Deg = 98%
              BTS             COBRA        • TBTS+deg+COBRA = 88%
                                             • TSep+TII+Clli = 86.5%
                                                                                    TBTS ~ 98%       TBTS+COBRA~ 88%
  Beam divergence (mrad)              Expected Stopping Rate                                        3% decays
                                                                                                     9% straggling
                                            R = 9.6·107 +/s
                                               at 1.8mA 4cm Tg
                                                                                 Transmission
                                                                                 Efficiency (%)
                                       (1.7·108   +/s   at 1.8mA 6cm Tg)




P.-R Kettle                                   MEG Review July 2005                                               19
                                 Target Optics – degrader cont.
                 (2) SNM Solutions ( no degrader in BTS)
                                     (125 Mylar Window)
• either combine Degrader + Target (asymmetric stop distribution)
• or move degrader slightly upstream of target (e.g. use as end-wall of target insertion tube)


           COBRA Spot size vs BBTS
                                                                Conclusions SNM (no BTS degrader)
                                                     • Combined Soln: gives  ~ 10 mm for 125 Mylar Window
                                                       with 190  Mylar  ~ 11.5 mm
                                                     • no straggling loss only 3% decay loss
                                                            Expected Rate R ~ 1.06·108 +/s at 1.8mA 4 cm Tg.
                                                     • BUT annihilation radiation potential worse - needs to be simulated
       SNM       DNM
                                     DNM
      unlike               SNM                       • Upstream Soln: gives similar results to DNM  ~ 12.5 mm
      polarity                       like polarity   • annihilation radiation potential worse - needs to be simulated
                                                                  
                                                      beam                             upstream Deg. 15 cm
                                                                        target
       Combined Tg + Deg
                                                                        e+
                                                        degrader
                                                                  
                                                     beam
                                                                        target
                                                                        e+


  P.-R Kettle                                         MEG Review July 2005                                              20
                                    Target & Insertion Tube
Target Geometry ( for beam  = 10mm)
LPROJ = 150.4 mm,  = 21.8°, a = 60.3 mm, LTRUE = 161.9 mm
material: CH2 + Rohacell / Mylar
Slanted Target must be thicker – multiple scattering loss                       LTRUE
on downstream-side !!!
Target Simulation underway:
• check of optimum angle                                               LPROJ
• dependence on target thickness (multiple scattering,
   background, acceptance, timing, resolution)
• material considerations
• decay particle hit distributions on end-cap materials &
  associated background acceptance




  P.-R Kettle                                    MEG Review July 2005            21
                           Target & Insertion Tube + survey
Target Insertion Tube & Support System (TISS)

Material:
• Rohacell (PMI) closed cell foam, maybe + EVAL foil?
  wall thickness probably 2 mm Rohacell 31
• length ~ 1500 mm
• dia. ~150 mm
•  Weight ~ 51 g
• simulations concerning background from
  e+ interactions in TISS underway


                                                                        Target Insertion Tube

Survey aspects:
• target plane determined outside wrt. survey markers
   on rohacell support rings (laser tracker)                           -target
• possible temporary thin cross-wires on support rings                 system
   for axial + radial alignment (break afterwards)
• radial adjustment made with TISS end-flange
                                                                                   Flange
• axial position set by TISS (self-positioning)
                                                                                   lateral +
                                                                                   vertical
                                                                                   move-
                                                                                   ment




  P.-R Kettle                                   MEG Review July 2005                            22
                                          Schedule 2005
  Changes 2005: (compared to previous schedule)            Critical Path
• Separator schedule + 8 weeks                           • Commissioning Part 1 too short for BTS/COBRA
• BTS Schedule + 7 weeks                                 phase space measurements  Dec. Part 2
• COBRA end-cap + target design + manufacture extended   • final Target measurements  first beam 2006




  P.-R Kettle                                 MEG Review July 2005                                        23
                          Summary + Critical Path


Summary:
• beam transport system up to COBRA defined
• COBRA + Platform surveyed into position
• All beam transport elements now manufactured
• MEG Separator being conditioned
• BTS successfully tested in Novosibirsk & delivered PSI (8th July)
• BTS reached current of 283A during commissioning at PSI (18th July)
• All cryogenic lines installed to zone
• all vacuum system available
• engineering project for COBRA end-caps + target Insertion & support system underway
  manufacture to be completed Feb. 2006



 Critical Points:
 • COBRA phase space measurement delayed until Dec. 2005 (delays Separator + BTS)
 • Final measurements with target delayed until first beam 2006




P.-R Kettle                          MEG Review July 2005                               24
                              -Beam Results (re-cap)

First - Beam Studies with MEG Beam:                                 Provisional Results
                                                                    - Integral Spot Rates MHz
                                                             for 1,8mA Proton Current & 4cm Target E
for calibration purposes in the experiment
-p→0n, -p→n                                              Normalized to Momentum Slit Settings:
55 → 83 MeV s and 129 MeV s                                  FS41L/R 250/280 FS43L/R 240/220


Data taken from:

• P-spectrum measurements 25-33 MeV/c
  s detected above 30 MeV/c (pulse-ht. + RF tof)
• dedicated - runs at 56 MeV/c & 103 MeV/c
  56 MeV/c interesting since max. momentum
  that can be transported to COBRA with
  good optics SNM in BTS
• dedicated CEX run at 112 MeV/c

                                                                                                     e-

                                                                                                     μ-
                   56 MeV/c R = 7.6  ·106   -/s
                                                slits open
                                         5 -/s slits70/70
                            R = 7.2 ·10
                                                                                                     -


 P.-R Kettle                                 MEG Review July 2005                                    25

				
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