Proposal for Japan-US collaboration on New Test Facility for Novel Accelerator R&D (FACET at KEK)

1. Proposal for Japan-US collaboration onNew Test Facility for Novel Accelerator R&D (FACET at KEK) M. Yoshida, K. Nakajima, M. Sato, S. Matsumoto, M. Nozaki, S. Yamaguchi Novel Accelerator Promotion Office in KEK

2. Japan-US collaboration for me • Development of klystrons and other electron tubes.(Mitsubishi / Toshiba)Technologies are based on Japan-US collaboration. • Concerning to beam driven accelerator region,U.S. has many experiences for more than 10 years.We have to learn more about this region. => ILC after burner etc. New concept IOT for ERL DRFS klystron / L-band 40 MW etc.

3. FACET at SLAC 0.4 ps 1.19 GeV σz= 5.5mm=18 ps εx,y=50 x 5 mm・mrad 23 GeV, 3nC σz=14μm=50 fs σx,y = 10 μm β ～ 1 m At FFTB experiment : Gradient : PWFA(>30GV/m), DWA(>16GV/m). Total acceleration voltage : > a few GeV. We are discussing with Dr. Mark Hogan.

4. FACET at KEK 8 GeV LINAC from 1998 Install Photocathode RF-Gun ps modulated laser Experimental Area 40 TW laser sz=1 ps, q > 5nC, εx,y < 20 mm・mrad BCS Total length ~400m => 9 GeV e- 9 GeV, 5nC σx,y = 35μｍ (β～1m) e+ 4 GeV, 5nCfrom damping ring e+ Damping Ring (under construction)

5. Target for FACET in KEK • Continuous novel accelerator facility until Super-KEKB shutdown ～2025 ? • Short pulse laser complex facility : Laser modulated photo cathode RF-Gun and LWFA injector for femtosecond witness beam. • User facility for University etc. ～100 fs electron bunch LWFA fs witness bunch DWA (or PWFA)

6. Ex. DWA DWA experiment is just started using another low energy fs beam. Single-wall DWA: ×Transformer Ratio(～3) Multi-wall or photonic DWA with multi femtosecond bunch: Laser modulated micro bunch structure Higher Transformer ratio + For microwave: Klystron : 350 kV Accelerator : 35 MV/m => transformer ratio = 100

7. 8 GeV LINAC Third Switch Yard Damping ring (under construction) KEKB (continuous inj.) 8 GeV LINAC Gun AR (2 inj./day) PF (top up) Third Switch Yard

8. Beam diagnostic station &FACET at KEK LINAC Beam damp Pulse bend for PF Experimental Area (beam damp) ～2014 : no injection to KEKB ↓ 2014～ : beam switch for KEKB/PF & Beam Damp

9. Key technologies • Laser plasma injector • The witness beam. • Sub-fs beam. • Fast beam switch (completed) • Event system • Pulse bend • RF-Gun (will be installed soon) • Velocity bunching DAW => high charge & low emittance • Modulated laser => micro bunch structure. • X-band for harmonic compensation and bunch compression. • Also use for Beam Diagnostic Station for LINAC Upgrade : Bunch Length / Sliced Emittance

10. Laser Plasma Injector LWFA injector for femtosecond witness beam • Stacked capillary • 40 TW laser is enough for self-injection • Upgrade existing TW laser Discharged by YAG laser

11. Fast beam switch Beam Damp Mode Damp • 50 Hz Event System (completed) • Pulse Bend (installed) FACET New beam line is required Experimental Area KEKB e+ KEKB e-

12. Velocity bunching DAW RF-Gun + Laser modulation Micro bunch structure 1/4 Transient Angle Linear velocity bunching will be expected to generate higher charge bunch > 10nC

13. X-band • Harmonic compensation (suppress second term) • Bunch compression • Nextef : => • 3 PPM klystrons. • 150 MW

14. Summary • FACET at KEK is considered to construct the beam driven and short laser complex facility, it has some different aspects compared with FACET at SLAC. • KEK 8 GeV LINAC has unique ability for novel accelerator test facility except for SLAC in the world. • It is expected to become a good complementary project to FACET at SLAC.