Progress on photon collider hardware

1
Progress on photon collider hardware

• Jeff Gronberg
• International Workshop on Linear Colliders
• Jeju Island, South Korea
• August 26th 30th ,2002

This work was performed under the auspices of the
U.S. Department of Energy by the University of
California, Lawrence Livermore National
Laboratory under Contract No. W-7405-Eng-48.
2
Outline

• Beam dump window design
• MERCURY laser begins commissioning
• Interferometric alignment system test bench
• Proposal for a photon collider testbed at SLC

3
Compton Photons are the primary heat load on the
beam dump window

• Total power 4.3watts x (plate thickness, mm)2
• 7.11 mm radius beam spot, 2mm thick copper window
• 11 C temperature rise, effective stress a factor
  of 7 away from failure, no problem

4
MERCURY laser uses helium gas flow cooling for
high average power operation with minimal
wavefront distortion
Gas cooled head and vanes
5
MERCURY commissioning has begunOne amplifier
head with 4 of 7 crystals installed

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16
14
12
1 Hz operation
Output Energy (J)
10

8
6
3.3 Hz operation
4
2
0
40
60
80
100
Shot

• Single head operation with 4 crystals
• Producing 15 Joule pulses at 1 Hz
• Fabrication of remaining crystals and full power,
  two head (100J _at_ 10 Hz) operation within the next
  year
• Optimization of beam quality once full system is
  operational

6
Interferometric Alignment System Testbed Under
Construction

• Half-scale prototype of optics / alignment system
  is currently under construction
• Optics fabricated, currently being coated
• Alignment system being assembled
• Operation in September 2002

7
gg Engineering Test Facility at SLCRevive SLC
and install beampipe with opticsto produce gg
luminosity
Beam Energy DR g?x,y (m-rad) FF g?x,y (m-rad) ?x
/ ?y ? z ?x,y N?
30 GeV 1100 / 50 1600 / 160 8 / 0.1 mm 0.1 1.0
mm 1500/55nm 6.0E9
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Compton backscattering at 30 GeVwith a low power
laser
Comparison of CAIN with a simple PANDORA
parameterization. Laser pulse of 0.1 Joule

• 0.1 Joule laser pulses produce measurable gg
  luminosity
• 25 of incoming electrons Compton scatter
• Maximum photon energy 1/3 of incoming electron
  energy
• Electron energy cuts off at 20 GeV
• Low energy tail from multiple scatters
• The gg, eg and ee events can be separated solely
  with their kinematic information
• Identify two hit events in the calorimeter
• No tracking required
• Run 1 day for a spectrum

9
Full test of Optics / IP packaging and
operational issues

• Many operational issues with the IR beampipe
• Can the optics alignment be maintained during
  installation?
• Do the optics need active cooling?
• Will this interfere with the final focus magnet
  stabilization?
• Can the conversion rate be reliably achieved?

Primary focus system
Reverse focus system
Outer carbon fiber tube
Strongbacks
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Proposal for the Photon Collider testbed is being
written

• Required hardware is defined.
• Cost and schedule are being developed.
• Experimental run plan is to demonstrate reliable
  production of gg luminosity and measure the
  energy spectrum.
• A workshop on this proposal will be held at SLAC,
  November 21-23, 2002

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Conclusions

• MERCURY laser commissioning is going well
• Full power and repetition rate within a year
• Optimization of wavefront quality will be done
  once full power operation is routine
• Half-scale optics have been purchased and a
  demonstration of the alignment system will be
  done in September, 2002
• Proposal for a photon collider demonstration at
  SLC is under development.
• Collaborators welcome.
• Workshop at SLAC November 21-23, 2002