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

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

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

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

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

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

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)

Electron- and Laser Beam-parameters

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

Laser path after FF

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

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” --1996

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

FEL scheme using pulse stretching and compression

Gamma gamma induction driver & other Induction linacs

FEL Parameters

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?