ATF Status December/2002 H. Hayano

1. ISG9 at KEK 12/10/2002 ATF Status December/2002H. Hayano Multibunch photo-cathode RF-gun Multibunch emittance Instrumentation developments Plans for spring 2003 run

2. ATF Introduction E=1.28GeV Ne=1x1010 e-/bunch 1 ~ 20 bunches Rep=1.5Hz X emit=2.5E-6( at 0 intensity) Y emit=2.5E-8( at 0 intensity)

3. Single Bunch emittance • ex = 2.0x10-9 ( exn = 5.0x10-6) • ey = 2.1x10-11(eyn = 5.3x10-8) at 9x109 intensity

4. Multibunch photo-cathode RF gun • For better MB injection into DR generation of high quality multibunch low emittance, low energy spread, high & flat intensity • Combination of BNL-cavity and Cs2Te cathode enough operation experience in CTF & TTF • New laser system; 20 bunch, 2.8ns spacing, 266nm Nd:YVO4 (1064nm) 357MHz mode-lock laser + amplifier • Load-lock system for Cs2Te cathode block extra cathode blocks and evaporation chamber • KEK built gun-cavity precise machining and blazing by KEK machine center

5. RF-gun cavity & cathode block

6. Multibunch photo-cathode RF-gun

7. Gun cavity, Load-lock & Laser system

8. RF gun beam at 80MeV • Beam Intensity ~1x1010/bunch • Normalized Emittance ey= 28x10-6 rad.m • Bunch length sz= 6.4 ~ 7.9 ps • Energy spread dE/E = 4.9% full-width • Q.E. of CsTe cathode 16% initial, 2~3% with RF ON & constant over a week

9. multibunch beam in DR 3 bunch 19 bunch Wall current monitor Beam intensity

10. Multibunch emittance • Beam intensity in DR 0.3~ 0.5x1010 e-, 19 bunch, 2.8ns spacing with 0.78Hz repetition limited by max. beam power of radiation safety • Monitors of MB emittance MB (or projected) Laser-wire Projected SR interference monitor, X-ray SR monitor MB (or projected) wire scanner: (EXT-line coupling problem) • Problem of MB emittance big energy fluctuation ( coupled bunch longitudinal oscillation )

11. New Laser wire : X & Y scan X profile Two wire chamber Y profile

12. Emittance by Laser wire 1% y/x emittance ratio

15. X-ray SR profiles X profile Y profile 39.27 +/- 0.53 [μm] 7.30 +/- 0.12 [μm] After subtracting dispersion effect xXSR = 1.8 x10-9, yXSR= 1.1 x10-11 ( ~ 3 x109 bunch intensity)

16. MB energy fluctuation

17. MB longitudinal oscillation

18. Candidates of impedance source • DR cavity HOM no response for temp., tuner, Vc, feedback, direct RF feedback, no enhanced signal from HOM pickup • Kicker ceramic insulation temp. rise with beam, HFSS calculation suggestion • Other source? tune exciter electrode?

19. New instrumentation developments • ODR beam size monitor observation of Diffraction Radiation in visible light new slit target was installed. • New clip-circuit for DR BPM single shot 3µm resolution circuit • Beam tilt detection by cavity-BPM study was started (SLAC) • nm resolution cavity-BPM 3 cavity BPM setup was started • Multibunch BPM circuit test continuing (SLAC) circuit under fabrication (KEK)

22. Plans for Autumn-Spring 2003 run • Run by multibunch photo-cathode RF gun smooth multibunch operation from 1 bunch to 20 bunches with high intensity and low beam loss • MB emittance study emittance was confirmed by Laser Wire. Longitudinal oscillation was observed. need to fix them by identifying the source. • DR re-alignment & Beam Based Alignment using new coming BPM circuit (Jan. 2003), more precise orbit control will be possible. • EXT line coupling study search of coupling source (EXT kicker?) • Instrumentation developments LW, XSR monitor, ODR monitor, cavity-BPM, multibunch BPM, etc end