SERA

1. PHIN SERA Summary of the LAL activity in the work package 4 of the JRA2 2-5 December 2008 G. Bienvenu, M. Desmons, M. Joré, B. Mercier, J. Prevost, C. Prevost, R. Roux LA L, IN2P3-CNRS, Université Paris-Sud, France 1- Construction of 2 photo-injectors: one for CTF3 and one for LAL 2- Upgrade of the NEPAL test beamline at LAL

2. frequency HF (GHZ) 2.99855 PHIN Power HF (MW) 30 SERA Beam energy (MeV) 5 – 6 Current (A) 3.51 Charge/bunch (nC) 2.33 Duration of the train (µs) 1.548 Total extracted charge (µC) 5.43 Bunch length, FWHM (ps) 10 Energy spread rms (%) < 2 Normalised emittance (pmmmrad) < 25 Residual pressure (mbar) 2.10-10 Specifications of the gun 1 Gun type 4 used in CTF2 as a start point 2 Symmetrical overcoupling (beamloading) 3 No tuners 4 Coils for emittance compensation 5 Improve the vacuum: critical issue CERN measurements with the CTF2 experiment

3. PHIN SERA 1- Construction of the CTF3 photo-injector 2004: simulations of the RF design and of the beam dynamics => technical drawings • Hole coupling: • overcoupled • symmetrical HFSS Elliptical irises to reduce Surface electrical field Racetrack shape of the coupling cell Fr = 3.0 GHz Rs = 6 MW Q = 14530 P = 10 MW (vacuum) P = 30 MW with beam Injection during the rise time

4. slaser(mm) 0.6 0.8 1 1.4 2.8 Losses (%) 1 0.3 0.3 0 0 PHIN SERA ex (pmmmrad) 13.5 16 17.6 19.6 21.0 5.45 19.6 3.2 3.56 0.36 E (MeV) ex(pmmmrad) sx (mm) sz (ps) sg /g (%) FWHMl (ps) 11 9.6 9 8.4 sg/g (%) 0.5 0.4 0.4 0.36 0.41 7.9 Beam dynamics with PARMELA Q = 2.33 nC Fopt = 35 ° ERF = 85 MV/m set by beamloading! Emittance minimum: coils on the gun To get better, square shape of the laser => e < 10 pmmmrad possible

5. PHIN SERA 1.10-6 Pressure (Pa) Without holes 1.10-7 With holes 1.10-8 2 4 6 8 10 12 Distance (cm) Vacuum Goal:  10-10 in the first cell for a long photo-cathode lifetime Monte-Carlo simulations of the residual pressure Useless above 40 l/s Envelop around the gun coated with NEG 42 holes drilled in the gun walls

6. PHIN SERA 1- Construction of the CTF3 photo-injector Complete photo-injector with: -Gun -Coils -mechanics -Vacuum system

7. PHIN SERA 1- Construction of the CTF3 photo-injector • end of 2005: RF prototype of the gun received • iterations between RF measurements and mechanical adjustments • finished in 02/2006 • Definitive model ordered in June 2006, cells at LAL in 10/2006 • Cells sent to CERN to be brazed, done in 12/2007 • Big leaks detected, attempts to repair => gun found unusable in 03/2008 • Decision to give to CERN the gun originally for LAL which was successfully brazed in 04/2008 • The gun is installed in the CTF2 area, commissioning in October 2008

8. PHIN SERA ! 2- Construction of a test beamline at LAL Goal: build a small machine to test RF guns at LAL in the NEPAL room E (MeV) Q (nC) Frep (Hz) < 10 < 2 5 Specifications: • In 2004, study of radiation safety showed the existing shielding is not sufficient • because legal threshold of radiation are lower than 20 years ago. But a supplementary shielding on the whole area is too expensive => • In 2005, new study with a reduced area of the accelerator: • - a roof of 1.4 m of concrete is required • In 2006, engineering study showed that the floor cannot support the load • discussion with the institute for the funding of the civil engineering • Beginning of the works in October 2006

9. PHIN SERA 2- Construction of a test beamline at LAL Layout of the accelerator area

10. PHIN SERA 2- Construction of a test beamline at LAL The civil engineering begun in October 2006 Holes are drilled in the floor, pillars are set-up, then a concrete floor is built End of civil engineering in March 2007

11. PHIN SERA 2- Construction of a test beamline at LAL Most of the beamline was installed in July 2008 AlphaX RF gun • 3 GHz • 2,6 cells • waveguide • coupling • compatible • with NEPAL beamline • Due to the lack of funds, no RF booster and no photo-cathode preparation chamber • Diagnostics: only 2 WCM and one Faraday cup in the straight way, screens next year

12. PHIN SERA 2- Construction of a test beamline at LAL Beam dynamics with PARMELA PHIN gun, 85 MV/m, sr (laser) = 1.4 mm, 10 ps, Q = 2.33 nC Output of PHIN gun alone : sx,y = 3.5 mm; e = 20.6 pmmmrad; sz = 3.5 ps, sg/g = 0.3 % Output of alphaX gun alone : sx,y = 3.9 mm; e = 19.2 pmmmrad; sz = 3.9 ps, sg/g = 0.6 %

13. PHIN SERA 2- Construction of a test beamline at LAL Other components 1) RF source modulator + klystron We reached up to -10 kV of the power supply => -170 kV in the transformer plateau of 3 µs but overshoot too big to increase the HV in the klystron =>will begin the operation with the half power: enough for one gun 2) Low level RF is ready: pilot + pre-amplifier

14. PHIN SERA ! 2- Construction of a test beamline at LAL 3) Laser, ND : YLF bought to the HighQ company l = 262 nm E = 90 µJ Dt = 10 ps Frep = 5 (100 Hz) One pulse Availability, not very high, lot of problems Several round-trips between LAL and Austria Temporal measurements with a streak camera (ARP) Laser pulse duration = 8 ps (FWHM)

15. PHIN SERA Summary PHIN photo-injector • The RF gun have been delivered to CERN and successfully commissioned. • The twin one for LAL is being machined in the LAL’s workshop, finished in June? NEPAL experimental hall • The upgrade of the NEPAL test stand is finished. • The start-up will be performed with the AlphaX gun. • The PHIN photo-injector will be tested at LAL in the second half of 2009.