1. Proposal for Japan-US collaboration on New 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 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 0.4 ps 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 BCS Install Photocathode RF-Gun  z =1 ps, q > 5nC, εx,y < 20 mm ・ mrad Total length ~400m => 9 GeV 8 GeV LINAC from 1998 e + Damping Ring (under construction) e- 9 GeV, 5nC σx,y = 35μ ｍ (β ～ 1m) e+ 4 GeV, 5nC from damping ring Experimental Area ps modulated laser 40 TW laser

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

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

8. Experimental Area (beam damp) Beam diagnostic station & FACET at KEK LINAC Beam damp Pulse bend for PF ～ 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 Stacked capillary 40 TW laser is enough for self-injection –Upgrade existing TW laser Discharged by YAG laser LWFA injector for femtosecond witness beam

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

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

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.