Docstoc

ppt talk

Document Sample
ppt talk Powered By Docstoc
					                             Methods Beam Profile Measurements at
                                 High Current Hadron Accelerators
                                      Peter Forck and Andreas Peters
                        Gesellschaft für Schwerionenforschung, Darmstadt

                                            ICFA-HB2004, Bensheim
   The determination of transverse profiles is required for:
        Save operation of a facility
        Commissioning of an accelerator
        Comparison to numerical models
   Outline of the talk:
   1.    Comments on destructive methods
   2.    Beam Induced Fluorescence (BIF) detection
   3.    Ionization profile monitor (IPM) equivalent to Residual Gas Monitor (RGM)
         (not discussed here: photo-detachment for H- beam  laser wire scanner)

   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                   Intersecting technology: Linear wire scanner

                                                                                  Example: CERN type
   A wire C or SiC with Ø100 m is scanned through
   the beam, detection with secondary particles
   (low-Z material low energy loss)
   Problem: Heating of the wire
     full beam can not be monitored
       restriction in current or time
   Advantage: high resolution,
   large dynamic range, halo detection possible
   Disadvantages: meas. at different times,
   intersecting


   Halo detection:
   Wire at beam center
   Plates at beam edges
   Example: Los Alamos
   (D. Gilpatrick et al.)

   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                         Intersecting technology: Flying Wire

                                                                  Example: CERN type
  Can be used at synchrotrons
  Advantage:
   high resolution
   large dynamic range
   halo detection possible

  Disadvantages:
   measurement at different
  time
   intersecting




   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                          Intersecting technology: SEM-Grid


   Example: GSI-LINAC type with 16x16 wire, spaced by 1 mm




                                                                                                      20 mm:




     Advantage: large dynamic range, profile at one time stamp
     Disadvantages: limited spatial resolution at about 0.5 mm, intersecting
   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                   Intersecting technology: Scintillation Screen


   Example: GSI-type with Al2O3 ‘Cromolux’ (used for slow extraction):




    Advantage: simple technique, direct method, full 2-dim image
    Disadvantages: very limited dynamic range (given by the material), intersecting

   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                                  Residual Gas Fluorescence

   For high power accelerator non-intersecting methods required!
   Realizations at Los Alamos, Saclay, CERN, UNI-Frankfurt, GSI, COSY ….
   Physics of fluorescence for N 2 residual gas:
   • Due to the beam’s energy loss, the residual gas molecules are excited
   • Decay of N2+ levels generate light, wavelength range 390 nm <  < 470 nm.
   Lifetime about  = 60 ns.
                                      N2 Spectrum at LANL (D. Gilpatrick et al.)
                                      for p at MeV energy and 5*10 -5 mbar
                                                                             Fluorescence of 200 keV p in N2 (1961)




                                                                 In addition: 1 to 25 GeV at CERN PS and SPS.
   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                       Image Intensifier used at GSI-LINAC

       Technical realization of image intensifier at GSI:
       • Photo cathode: photon-to-electron conversion, 25 to 30 % efficiency
       •Two step MCP (25 mm diameter): 106 fold amplification
       • P 46 phosphor: electron-to-photon conversion, 300 ns decay, 530 nm wavelength
       • Minifying taper coupling to CCD chip (1/2’’): 7% transmission
       • Digital camera (Basler A302fs): Firewire interface




   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                                 Test Setup at GSI-LINAC

                      Example: Test setup at GSI-LINAC:
                                                                                Advantage of digital camera:
                                                                                • no loss of quality due to cable
                                                                                • versatile trigger
                                                                                • variable exposure time
                                                                                In preparation at GSI:
                                                                                • compact installation
                                                                                  with 120 mm insertion
                                                                                • real time data acquisition
                                                                                  FireWire-interface
                                                                                  running RT-LabVIEW




   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                               Typical Result at GSI-LINAC


                                                                     Example at GSI-LINAC:
                                                                     4.7 MeV/u U28+ beam
                                                                     I=0.7 emA, corresp. to 10 9 particle
                                                                     One Single macro pulse of 200 s
                                                                     Vacuum pressure: p=10-5 mbar (N2)
                                                                     Features:
                                                                     • Non-intersecting
                                                                     • Single photon counting
                                                                     • High resolution (here 0.3 mm/pixel),
                                                                      can easily be matched to application
                                                                     • Variability by binning and averaging
                                                                     • Low background
                                                                     • Reliable method, as proven by
                                                                      comparison to standard methods
   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                          Application of Fluorescence Method

  Variation during the macro pulse detectable:                   Statistical behavior:
  Switching of image intensifier within 100 ns                   ‘Offline’ optimization
   Time window during macro-pulse                               statistics  integration time  resolution




   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                                       BIF at Synchrotrons

                                               Example: CERN SPS and PSB,PS (R. Jung, M. Plum et al.)
                                               • Photon yield scales with Bethe-Bloch energy loss
                                               d determined for p from 100 MeV to 450 GeV
                                               • N2: ΔE of 3.6 keV equals to one optical photon
                                                   Lifetime  = 58 ± 0.3 ns at 25 GeV
                                                   (fluorescence decay excited by  5 ns long bunches)
                                               • Xe: ΔE of 46 keV equals to one optical photon)
                                                   Lifetime  = 59 ± 1 ns at 25 GeV
                                                              Comparison to wire scanner at SPS




   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                              Comparison for different Gases

   Choice of fluorescence gas:
   • High fluorescence yield at optical wave-length
   • Short lifetime of excited level
                                                  Example: Ion source 100 keV, 100 mA protons
   • Good vacuum pumping
                                                  P. Ausset et al. (Saclay)
   Results:
    Profile is independent of gas
                                                          Profiles from
    N2 is well suited                                    different gasses
   Care:
   • Long life can lead to broadening
     due to the beam space charge
   • Light emitted by ions
     e.g. p beam recombined H
     emission of Balmer-series




   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                                  Ionization Profile Monitor


   Detection of ionization products from
   beam-residual gas interaction
   Advantage: All products are detected
                  ‘4π-geometry’
   BIF: Solid angle only ΔΩ  10-4
   Signal generation of IPM:
   • Secondary electrons/ions are
     accelerated by E-field (E500 V/cm)
     toward MCP-Phosphor.
   • MCP acts as an amplifier (106 amp.)
   High resolution mode:
    CCD readout, resolution 100 μm
      Time resolution 10 ms (frame rate)
   Fast readout mode (turn-by-turn):
    Array of 100 photo-diodes or PM
    spatial resolution 1 mm
    Time resolution 100 ns
     500 turn data storage required


   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                             Realization at GSI-Synchrotron

                                                                     Electric field electrodes, 175x175 mm2




                                                             MCP detector (active area 100x30 mm 2
                                                            63 wire readout, wires spaced by 2.1 mm

                                                            300 mm flange

   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                                Technical challenges for IPM


   • Electric field for secondary ion/electron acceleration
         large homogeneity required to receive an undistorted image
         complex vacuum installation
   • Magnet field with 0.1 T required with large clearance (up to 40 cm)
   • MCP: large dynamic range required due to low/high current operation, MCP switching
   • Anode technology with wire readout behind MCP:
       Advantage: mechanically compact, fast readout (turn-by-turn), radiation hardness
       Disadvantage: limited resolution (wire spacing 1 mm), image current interference
   • Anode technology with Phosphor screen behind MCP:
       Advantage: high resolution by CCD camera, ‘industrial’ data acquisition
       Disadvantage: complex fast readout (photomultiplier or diode array),
                            radiation hardness (digital electronics close to beam pipe)




   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                  Magnetic field required for GSI-parameters

  Ion detection: for intense beams
      broadening due to space charge
  Electron detection:
  Magnetic field required for guiding
  the e- toward the MCP.
  Main effects:  ExB-drift
                     3-dim start velocity
              rcyl < 0.1 mm if B  0.1 T


                                             Parameter:                                              Parameter:
                                                 +
                                             - H2 Detection                                          - e - Detection
                                             - 10 9 U73+                                             - 10 9 U73+
                                             - lBunch = 25 m                                         - l Bunch = 25 m
                                             - drift = 5 cm                                          - drift = 5 c m
                                             - E = 50 V / mm                                         - E = 50 V / mm
                                                                                                     - B = 100 mT




   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                                            Magnet design

  A magnetic field is required to guide the electrons:
  Maximum image distortion:          Example: RHIC-type permanent magnet (R. Connolly et al.)
  5% of beam width  about ΔB/B < 3% Field strength : B=0.14 mT
    (particle tracking required)     Pole clearance 12 cm, length 30 cm in beam direction
  Realization:
   Permanent magnets
   Electro-magnets
  Challenge:
   Large clearance of  400 mm
  and compact design required




   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                                       Detection of Cooling


    Example: Cooling of Xe47+ beam at GSI to enlarge the accelerated current.
    Important for the right setting of e-cooler and injection parameters.




   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
           Injection matching measured on a turn-by-turn basis

                                                       Example: CERN-SPS (C. Fischer et al.):
   Injection has to be well aligned                    Anode-technology:
                                                        Phosphor + Photomultiplier, 1.2 mm resolution
   to prevent emittance blow-up
    Turn–by-turn measurement

     Example: orientation mis-match


                                                              mis-matched



                                                                             100                       200 turns




                                                               matched


                                                                               100                     200 turns
   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                           Beam blow-up by resonance crossing

                                                             Example: Resonance crossing at GSI-SIS
  High current stetting at SIS:
  1010 Kr36+ ions
     injected with QH=4.15
  For slow extraction QH=4.31
  Blow-up during
        resonance crossing
  Important measurements
        for any manipulations




   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                         Coupling resonances for beam rotation


     Example: Wanted vertical-horizontal emittance
     exchange by skew quadrupoles
     Within 10 ms the beam is                                    hor.                          hor.

     rotated by 900 in real space!




   Monitoring of wanted manipulation to
   reach the space charge limit !
                                                              vert.                           vert.
    turn-by-turn readout also
      required during the cycle!
        (MCP switching necessary)




   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,
                                                Conclusion

  Non-intersecting methods required due to large beam current required !
  Beam Induced Fluorescence BIF:
     Advantage:          Simple mechanics (nothing installed in the vacuum), compact installation
                         high resolution possible, limited by optics
                         commercial hardware and data acquisition system
     Disadvantage:  low signal strength due to solid angle ΔΩ  10-4 and 10% detection eff.
                         local pressure bump required
     Application:        Mainly at LINACs
  Ionization Profile Monitor IPM:
     Advantage:          large signal strength, 4π geometry
                         high resolution possible down to 100 μm, limited by MCP
     Disadvantage:  complex installation inside vacuum
                         compact magnet with large homogeneity required
                         no commercial hardware and data acquisition system available
     Application:        Mainly at synchrotrons
  Thanks to all colleagues for discussion, results and pictures.

   Peter Forck (GSI), ICFA-HB 2004                                          Methods of transverse profile measurement
L. Groening, Sept. 15th,,2003 A dedicated proton accelerator for p-physics at the future GSI facilities
GSI-Palaver, Dec. 10th 2003,

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:11
posted:10/1/2011
language:English
pages:22