Proposal for JapanUS collaboration on New Test Facility

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

Japan-US collaboration for me • Development of klystrons and other electron tubes. (Mitsubishi / Toshiba) Technologies are based on Japan-US collaboration. New concept IOT for ERL DRFS klystron / L-band 40 MW etc. • 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.

FACET at SLAC 0. 4 ps 1. 19 Ge. V σz= 5. 5 mm=18 ps εx, y=50 x 5 mm・mrad 23 Ge. V, 3 n. C σz=14μm=50 fs σx, y = 10 μm β～ 1 m At FFTB experiment : Gradient : PWFA(>30 GV/m), DWA(>16 GV/m). Total acceleration voltage : > a few Ge. V. We are discussing with Dr. Mark Hogan.

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

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 femtosecond witness beam. • User facility for University etc. LWFA ～ 100 fs electron bunch fs witness bunch DWA (or PWFA)

Ex. 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 k. V Accelerator : 35 MV/m => transformer ratio = 100

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

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

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

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

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

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 > 10 n. C

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

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 Ge. V 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.