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					         Overview of Beam Instrumentations for
         High-Power Operation of the Spallation
                    Neutron Source


                                  Saeed Assadi for SNS B.I. Group
                               Beam Instrumentation Group Leaser
                                                      SNS/ORNL




Managed by UT-Battelle
for the Department of Energy
OUTLINE


 Overview of Beam Instruments
 SCL Laser Profile Monitor Project
 Recent results
 Challenge
 Future plan




2   Managed by UT-Battelle
    for the Department of Energy   WGF01- HB2008 8/26/2008
                The Spallation Neutron Source




3   Managed by UT-Battelle
    for the Department of Energy   WGF01- HB2008 8/26/2008
     SNS Accelerator Complex
               Front-End:                               Accumulator Ring:
     Produce a 1-msec                                  Compress 1 msec long
                                                         pulse to 700 nsec                                    Extraction
      long, chopped,                                                                  Injection
         H- beam                                                                                  RF

                                            1 GeV LINAC                                                         Liquid Hg
                                                                           1000 MeV
                                                                                                                  Target
                 2.5 MeV            87 MeV 186 MeV       387 MeV                                       RTBT
Ion Source                                                                             HEBT

                RFQ          DTL         CCL    SRF, b=0.61      SRF, b=0.81




                                        Chopper system
                      945 ns              makes gaps
                                                              mini-pulse
     Current




                                                                               Accumulation            700 nsec
                                                                                                       Pulse
                                          1 ms macro-pulse
 4   Managed by UT-Battelle
     for the Department of Energy                        WGF01- HB2008 8/26/2008
Interceptive Beam Instrumentation
Systems

           Operational
                                                                           IDump            RING
                                                                       2 Wire          2 Wire-deleted
                                              MEBT                     2 IDump Video
                                     5 Wires
                                     D-box emittance
                                     D-box beam stop                                                      Edump
                                                                      CCL                                  1 Wire
                                     D-box aperture              8 Wire , 4BSM,
                                     1 fast faraday cup          1 Faraday Cup
                                     1 faraday/beam stop
                                     D-box video                                                                   RTBT
                                                                                                              5 WireScanners
                                                                                                                  1 Harp
                                                                                                               1 RTBT Video
                                                                                                               Target Video
                               DTL
                     5 Wire                                                 SCL              HEBT
                     5 Faraday Cup                                                      5 Wire Scanners
                                                                                             2 BSM

                                                   CCL/SCL                                                    LDump
                                                   Transition                                                 1 Wire
                                                     1 Wire




5   Managed by UT-Battelle
    for the Department of Energy                           WGF01- HB2008 8/26/2008
Non-Interceptive Beam Instrumentation Systems
                                                                    IDump
                                                                1 Position                         RING
                                                                1 Current           2 Electron Profile Scanner
                                            MEBT                2 BLM               5 Electron Det. 12 FBLM
     Operational                   2 Thermal Neutron                                1 Beam in Gap Monitor
                                   3 PMT Neutron                                    1 Tune, 84 BLMs, 4 NDs
                                   D-box Mode-lock laser                            2 Transverse feedback system
    Not Operating                  2 Beam-Gap Monitor
                                   [ChuMPS]
                                   6 BPMs                                CCL                                 EDump
                                   2 BCMs                             8 Neutron,                          4 BLM, 1 BCM
                                   1 Mode-lock laser                  2 Thermal
                                                                       48 Loss
                                                                                                                       RTBT
                                                                                                                   1 Movable
                                                                                                                   Harp
                                                                                                                   3 FBLM
                                                                                                                   26 BPMs
                                                                                                                   26 BLMs
                    DTL
      2 Beam-Gap Monitor                                                  SCL                   HEBT
      [ChuMPS]                                                     32 Position 86         29 Position
      3 Diff BCM Monitor                                           Loss                   1 Laser Beam in-
      6 Thermal and 12 PMT Neutron                                 9 Laser Wire           gap
      6 Current, 12 BLMs                                           1 Laser Wire           1 Laser emittance       LDump
                                                  CCL/SCL          24 PMT Neutron
                                                  Transition                              sys                  2 Loss
                                             2 Position                                   48 BLMs, 4FBLM       1 Wire ,1
                                             1 Loss 1 Current                                                  BCM
                                                                                                               5 position



6   Managed by UT-Battelle
    for the Department of Energy                      WGF01- HB2008 8/26/2008
         Quick History and Facts about SNS

    The SNS is a short-pulse neutron source, driven by a 1.4 MW
    proton accelerator [ presently at .54 MW].

    SNS will be the world’s leading facility for neutron scattering
    research with peak neutron flux ~20–100x ILL, Grenoble

    SNS construction project, a collaboration of six US DOE labs, was
    funded through DOE-BES at a cost of 1.4 B$

    SNS will have 8x beam power of ISIS, the
    world’s leading pulsed source user facility,
    Stepping stone to other high power facilities,
    expected to achieve 1.4 MW in two years.

7   Managed by UT-Battelle
    for the Department of Energy   WGF01- HB2008 8/26/2008
Motivation to Add &/or Modify More Beam
Instruments

 Improve reliability
 Improve user friendliness – i.e. automation,
  additional features –
 Support, diagnose “unexpected” events – i.e.
  Spark detectors, LEBT and RFQ RGAs
 Accelerator Physics requests – Laser
  emittance system.
 Allow “parasitic” studies; IPM, electron
  profile monitor. Different types of BLMs.


8   Managed by UT-Battelle
    for the Department of Energy   WGF01- HB2008 8/26/2008
Continue: Motivation to Add &/or Modify More
Beam Instruments
 60 Hz Beam Accounting [Never was in the plan]
 Low Energy Beam Loss Measurements , WGF4- A.
  Zhukov’s talk
 Differential Current Measurements in DTL/CCL
 High Power Operations.– e/p Instabilities, use of
  digital active transverse feedback system for the
  Ring. WG F- (wed) – Craig Deibele’s talk
 Ring Electron Profile Monitor, BINP collaboration
  with SNS, initial results by W. Blokland in this talk.
 Computation of Space-Charge Effects in Allison Scanner
  and Its Application to the Measurement of Emittance by
  Timofey Gorlov

9   Managed by UT-Battelle
    for the Department of Energy   WGF01- HB2008 8/26/2008
      ORNL-SNS Laser Diagnostic Activities
          1)       MEBT Mode-lock laser initially in 1-D – 9/2004
          2)       SCL Nd:YAG 1064 nm Laser, 9-station – 9/2005
          3)       Laser Stripping test Nd:YAG, 3ed harmonic -- 8/2005
          4)       Working on making SCL Laser system turn-key -- to present



                                  SCL Laser Profile
                                  Monitors, 9-stations
   MEBT 3-D Laser
   Profile Monitor


                                             4M     4H        1D




                                                                           Laser Striping
                                                     Laser Emittance       Experiment


10 Managed by UT-Battelle
   for the Department of Energy             WGF01- HB2008 8/26/2008
   What does the Laser do? Photo-neutralization

                  hn                      H-                          H0 + e

       Requirements
           • High peak power
           • Small spot size
           • Transverse scan
           • Temporal stability
           • Detection



                                  Ibeam   12ns


      -H-
                                                                           time

        Cross-section is well known therefore stripping efficiency calculation is a matter of
        algebraic manipulation

11 Managed by UT-Battelle
   for the Department of Energy                  WGF01- HB2008 8/26/2008
Principle of Laser Wire, direct electron
current measurement at SNS.

                                  Photodetachment

                                                                S
                         H-       hn
                                                    H0                H0

                                                         e
                                             N

                                                                Faraday Cup

           • Detected electron number is proportional to the ion density


12 Managed by UT-Battelle
   for the Department of Energy             WGF01- HB2008 8/26/2008
Redundant Lasers are available for the
SCL.
                                                         Laser Room



      • High pulse energy
      • Small spot size
      • Single wavelength
      • Pointing stability
      • Temporal stability

                                                        Q-switched Nd:YAG laser
                                                        l = 1.06 mm
                                  Requirements:         frep = 30 Hz, Tw = 7 ns
                                                        Ep = 50 – 200 mJ
                                                        Injection seeded
                                                        Timing synchronized to SCL
13 Managed by UT-Battelle
   for the Department of Energy               WGF01- HB2008 8/26/2008
Layout of the SCL Laser Wire System
                                      LR Laser room                      Camera

                                           Laser wire station            Mirror                      LR

                                      32 Cryomodule number               Power meter

                            1     2    3   4     5              12 13 14 15    17              32


                        250 m                  227 m                   160 m                  25 m


                                                                                       Ring



                                                                                                      Target


                          MEBT DTL CCL                      SCL


                                                • 4 LW from 200 MeV
                                                • 4 LW from 450 MeV
                                                • 1 LW at 1 GeV
14 Managed by UT-Battelle
   for the Department of Energy                            WGF01- HB2008 8/26/2008
SCL Laser Transport Line


                                  Q-switched
                                  Nd:YAG laser
                                  1064 nm
                                  30 Hz
                                  7 ns
                                  Up to 1.5 J
                                  Injection seeded




15 Managed by UT-Battelle
   for the Department of Energy                      WGF01- HB2008 8/26/2008
Schematic of Laser Wire Station Optics
                                   From
                                   LTL

                  Flip-Mirror               Mirror

                                                            H-scan




                                                Lens
                                                                            Beam Dump
                                  V-scan                                      Photodiode
                                                                      Ion
                                                                     Beam



16 Managed by UT-Battelle
   for the Department of Energy            WGF01- HB2008 8/26/2008
      Top-Level Software Controls all Stations and
      collects Data.
                 Profile Measurement                         LW Station Diagnostics




        User specifies station, axis, scanning        User monitors laser beam position, lens
        range/step/ave. number, controls              focus, electron collector output raw
        timing, and data acquisition                  signal


17 Managed by UT-Battelle
   for the Department of Energy        WGF01- HB2008 8/26/2008
Effects of LW Magnet Current
                                                   Magnet Current (A)
               0       1          2   3   4    5    6     7    8                        9        10       11       12        13       14
                                                                                                                                           LW Station 02



                                                                                                                                           LW Station 15




                                                                                                                                           LW Station 32


                                                                                        14

                              Falling edge cut                                          12
                                                                   Magnet Current (A)
                              Rising edge cut                                           10

                                                                                        8
                              Normal profile
                                                                                        6

                                                                                        4

                                                                                        2

                                                                                        0
                                                                                             0        2        4         6        8         10
                                                                                                           Laser Wire Station #

18 Managed by UT-Battelle
   for the Department of Energy                         WGF01- HB2008 8/26/2008
One challenge that is solved Effects of
LW Magnet Current
                                            Vertical Beam Profile Measurement at LW32
       Detector Output (100 mV/div)




                                                                                               Magnet
                                                                                               Current
                                                                                                 (A)
                                                                                                   12.9
                                                                                                   12.4
                                                                                                   11.9
                                                                                                   11.4
                                                                                                   10.9
                                                                                                   10.4
                                                                                                    9.9
                                                                                                    9.4
                                                                                                    8.9
                                                                                                    8.4
                                                                                                    7.9
                                                                                                    7.4



                                      14   16     18     20        22         24    26   28   30
                                                          Vertical Position (mm)
19 Managed by UT-Battelle
   for the Department of Energy                           WGF01- HB2008 8/26/2008
   Advantage of Laser is to be able to scan the entire Macro-pulse.



                                  Mini-pulse #1    #100        #200         #300




20 Managed by UT-Battelle
   for the Department of Energy                   WGF01- HB2008 8/26/2008
                   Beam Profile Measurements
             0.6                                                              0.3

             0.5                                                                                                                    LW1
             0.4                                                              0.2
Signal (V)




                                                                 Signal (V)
             0.3

             0.2                                                              0.1

             0.1

              0                                                                0
                   10    15            20         25        30                      10   15        20           25        30   35
             0.4                  Position (mm)                               0.5                   Position (mm)

                                                                              0.4
                                                                                                                                    LW5
             0.3
Signal (V)




                                                                 Signal (V)
                                                                              0.3
             0.2
                                                                              0.2

             0.1
                                                                              0.1

              0                                                                0
                   10    15            20         25        30                      10        15         20          25        30
             0.7                                                              0.8
                                  Position (mm)                                                     Position (mm)
             0.6                                                              0.7                                                   LW9
                                                                              0.6
             0.5
Signal (V)




                                                                 Signal (V)




                                                                              0.5
             0.4
                                                                              0.4
             0.3
                                                                              0.3
             0.2                                                              0.2
             0.1                                                              0.1
              0                                                                0
                   15    20            25         30        35                      10        15         20          25        30
                                  Position (mm)                                                     Position (mm)
21 Managed by UT-Battelle
   for the Department of Energy                        WGF01- HB2008 8/26/2008
Realistic Laser Beam with respect to H-
            Laser beam shifts on the lens
            surface

                                        Laser beam
                                                              Ion beam




                                    S
                                                         f



            Laser beam shifts + Ion beam
            shifts from waist

                                                              Yd
                                        Laser beam
                                                                     Ion beam
                                    S




                                                         f




22 Managed by UT-Battelle
   for the Department of Energy     WGF01- HB2008 8/26/2008
Challenge! Experimental Measurements
                                                                                                         Yd
                                                                                             Laser
                                                                                             beam             Ion
                                                                                                              beam




                                                                                         S
                              Measured profile as a function of lens position at LW14V

                                               Yd=0     Yd=5mm      Yd=10mm                          f

                   0.5


                   0.4
   Amplitude (V)




                   0.3


                   0.2


                   0.1


                    0
                         18          20         22          24          26         28         30
                                                         Position

                                     Why do we get poor profiles in this case
23 Managed by UT-Battelle
   for the Department of Energy                             WGF01- HB2008 8/26/2008
Current Laser Wire Box
                                                              f2.75


                                                     3.5                               5




                                              3.25
                                                                                                  4                       12




                                       13.5




                                                                                                               6.5
                                                                                               f2-3/8




                                                                                                                                    11.5
                                              3.25


                       5.75
                                                                    14                                         2.75

           rear                     front




                                                                                                                      1
                                                                                 f2-3/8
                                                     4.5




                                                                                                                      f2.5




                                                                                                                             7.25
                                                                                                 f2.5
                              3.5                             6.5
                                                                                2.75

                                                                                           1
                                                     12




                                                                                                        6.75




                                                                         11.5
24 Managed by UT-Battelle
   for the Department of Energy                            WGF01- HB2008 8/26/2008
Revised Laser Wire Box Design to Bring Larger
Travel Range     f2.75


                                                3.5                            5




                                         3.25
                                                                                          4                       12


                                  13.5




                                                                                                       6.5
                                                                                       f2-3/8




                                                                                                                            11.5
                                         3.25




                                                            14                                         2.75




                                                                                                              1
                                                                         f2-3/8
                                                4.5




                                                                                                              f2.5




                                                                                                                     7.25
                                                                                         f2.5
                                                      6.5               2.75



                                                                                   1
                                                12




                                                                                                6.75




                                                                 11.5

25 Managed by UT-Battelle
   for the Department of Energy                       WGF01- HB2008 8/26/2008
SUMMARY of Laser Profile Monitor

                   Profiles have been measured at all 9 stations
                   Operational parameters have been
                    investigated and optimized
                   Software platform has been improved
                   Issues of radiation and stability are looked
                    into and solutions are provided
                   Future plan
                           – Secure system reliability
                           – Optimize/document operational procedure
                           – Identify technical problems and work on solutions




26 Managed by UT-Battelle
   for the Department of Energy           WGF01- HB2008 8/26/2008
   Electron beam Transverse Profile Monitor
                                  Layout of the proposed EBP for SNS
                                      Accumulator Ring by BINP
                                                                               Phosphor
                                                                                screen
                                               Quadrupole
      Deflector                                   lens

                                                                               MCP



                                                                                           Photo
                                                                                          camera



                      Electron
                                               Proton
                        Gun
                                               beam
                                         750                             600

27 Managed by UT-Battelle
   for the Department of Energy                WGF01- HB2008 8/26/2008
 Collaboration on Design and Construction of Electron Beam Profile Monitor
 Between SNS-ORNL and BINP, Novosibirsk, Russia has started

                                                                                                 Probe beam:
                                          Simulation
                                                                                                 Energy=75keV,
                                                                                                 Scan.-parallel,
                                                                                                 3rd ,4th quads -
               Alexander Starostenko
                                                                                                 ON
                                       1,2


                                         1                                                       Proton beam:

                                       0,8
                                                                                                 Energy=1GeV
                                                                                                 Np=1*1013
                                       0,6

                                                              Blue line – theoretical profile,   Transverse size
                                       0,4
                                                                                                 r=1.5cm
                                                              Magenta + square –
                                       0,2                    reconstructed profile              Round uniform
                                                                                                 transverse
                                         0
   -3            -2               -1          0   1       2         3
                                                                                                 distribution
                                       -0,2




28 Managed by UT-Battelle
   for the Department of Energy                        WGF01- HB2008 8/26/2008                        28
  Horizontal Profile after 500 turn, 8 Micro-Coulomb of charge in
 the Ring.




29 Managed by UT-Battelle
   for the Department of Energy   WGF01- HB2008 8/26/2008
    Vertical Profile after 500 turn, 8 Micro-Coulomb of
   charge in the Ring ---- Another useful tool!




30 Managed by UT-Battelle
   for the Department of Energy   WGF01- HB2008 8/26/2008
                                  Thanks




31 Managed by UT-Battelle
   for the Department of Energy   WGF01- HB2008 8/26/2008

				
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