1. X-band Linac (NLC) based g-g collider
drhgfdjhngngfmhgmghmghjmghfmf
X-band Linac (NLC) based g-g collider
Kwang-Je Kim
Argonne National Lab
U of Chicago
April 23-26, Jinchun Yuan Hotel, Tsinghua University, Beijing

2. A second Region for Gamma-gamma, gamma-electron and electron-electron collisions Appendix B of the NLC ZDR report (May, 1996)
BINP: V. Telnov
Hiroshima U: T. Takahashi
KEK: K. Yokoya
LBNL: S. Chattopadhyay, W. Fawley, K.-J. Kim, H. Murayama, M. Ronan, A. Sessler, M. Xie, A. Zholents
LLNL: T. Houck, D. Klem, M. Perry, K. Van Bibber, G. Westenskow
SLAC: P. Chen, D. Helm, J. Irwin, J. Spencer, A. Weidemann
U of Rochester: D. Meyerhofer

3. Gamma Gamma Second Interaction Region at NLC
Energy: ECM=500 GeV
Pulse format: 90 bunches separated by 1.4 ns, 180 Hz16.2 kHz
X-band linac

4. Compton Back-scattered Gammas at CP are focused onto IP
CP and IP separated by b=gsx ~ 5 mm to dilute low energy gamma’s
Luminosity ~ 1033 cm-2 s-1 for 10% BW

5. Basic parameters
Use n=1
Avoid gamma and laser photons produce e+e-  x =4.8  lL ~ 1 m
For converting most electrons:
q=scNL/S ~ 1, S ~ lL ZR ~ lL t/c
Ng=1- e-q ~ 66%
With correct helicity A~ 1J, I ~ 1018 W/cm2
Avoid Large intensity lower fundamental energy, also produce higher harmonics

6. Analytic approach for optimizing Compton conversion efficiency
Scattering frequency
Can derive
Assuming Gaussian distribution, this simplifies the optimization

7. Simulation codes to include many physical processes at CP and IP
Linear and nonlinear Compton scattering
Linear and non linear B-W
Propagation from CP to IP
External magnetic field to sweep or plasma lens to over-focuss low energy e
IP:
Beam disruptions (e+-with opposing beam
Beamstrahlung with and coherent pair production
Incoherent processes
Beam propagation from IP to exit line
Several codes
Horton-Smith, Ohgaki and Yokoya, Telnov, Yokoya (ABEL & KEIN), Fawley (BERT),..
Spectral luminosity (Yokoya)

8. Electron- and Laser Beam-parameters

9. Ideas to reduce laser power
Multiple pass with
Reflecting optics
Double confocal resonator

10. Laser path after FF

11. Double pass Mirror Arrangement in gamma gamma interaction region
15: parallel beam transport from entrance
Focus to the left CP by 6, diffract to 7, then to 8
Mirror 6 has a small hole
911: parallel beam transport
Reflection by 11, back transport 107
Focus on the right CP, transport out to 1
¼ plate for polarization control

12. Solid state laser concept for gamma gamma built on 1 kW unit cells
All cells are powered by a single phase-stabilized oscillator
“Power will be feasible in a couple of years”

13. FEL approach for IR power
Psat ~ r E I
A=Psat t ~ 1 J
r ~1% t ~2 ps  E=50 GeV!! ( undulator magnet for 1 m will be difficult)
t ~1 ns  E=100 MeV  reasonable
Need an induction linac
Success at LLNL, ETA & ATA
Chirping requirement: Dw/w = 3x10-4
May well be within the FEL gain BW
May also manipulate induction linac

14. FEL scheme using pulse stretching and compression

15. Gamma gamma induction driver & other Induction linacs

16. FEL Parameters

17. In 1996 a Gamma gamma was a paper exercise
Laser power
Higg’s was also “imaginary”
The case for a Gamma Gamma may be stronger now
An FEL option for laser power?