THE CURRENT STATUS OF THE ALICE (ACCELERATORS AND LASERS IN COMBINED EXPERIMENTS ) FACILITY. C.Beard, R.Buckley, S.Buckley, P.Corlett, D.Dunning, P.Goudket, S.Hill, F.Jackson, S.Jamison, J.Jones, L.Jones, P.M c Intosh, J.M c Kenzie, K.Middleman, B.Militsyn, A.Moss, B.Muratori, J.Orrett, P.Phillips, Y.Saveliev, D.Scott, B.Shepherd, S.Smith, M.Surman, N.Thompson, A.Wheelhouse, P.Williams (STFC Daresbury Laboratory), D.Holder, P.Weightman (Liverpool Univ.), K.Harada (KEK) Abstract ALICE (Accelerators and Lasers In Combined Experiments), a 35 MeV energy recovery linac based light source, is being commissioned and developed as an experimental R&D facility for a wide range of projects that could employ synchronized ultra-short (<1ps) electron bunches and light pulses. A suit of light sources includes an IR FEL, Compton backscattering (CBS) X- ray source, high power THz source and a multi-TW femtosecond laser. The full energy recovery and coherently enhanced, due to shortness of the electron bunches, THz radiation have been already demonstrated on ALICE. Completion of the first phase of the CBS x- ray source experiment and first lasing of the IR FEL are expected before the end of 2009. Status of ALICE experimental facility and latest results on FEL, THz, and CBS development are reported in this paper. INTRODUCTION ALICE, formerly known as ERLP [1], is a new R&D facility currently being commissioned at Daresbury Laboratory. The accelerator is an energy recovery superconducting (SC) linac operating at the nominal beam energy of 35MeV. The high voltage DC photoelectron gun operates at nominal voltage of 350kV and bunch charge of 80pC. The bunch trains can be of variable length from a single bunch regime to 100μs with a bunch repetition frequency of 81.25MHz within the train. The train repetition frequency can also be varied from 1-20Hz. In addition to the accelerator, several light sources will be available for conducting a variety of R&D research, including pump-probe experiments. These are (i) an IR FEL with wavelength of ~4μm; (ii) a THz source with coherent enhancement of the radiation intensity due to sub-picosecond bunch lengths generated by ALICE; (iii) a Compton Backscattering (CBS) X-ray source with photon energy of 15 or 30keV depending on the collision angle between the photons and electrons. The CBS source is powered by a terawatt IR femtosecond laser that can also be used as a stand-alone light source for a variety of experiments. PRESENT STATUS Full energy recovery and demonstration of the coherently enhanced THz radiation were successfully achieved on ALICE by the beginning of 2009. The injector can now reliably deliver beams with bunch charges well in excess of 80pC and with the design bunch structure, i.e. 81.25MHz bunches in trains up to 100μs, repeating at 1-20Hz. However, due to a number of mostly technical problems, some of the other ALICE design parameters have not been achieved at present. The gun operating voltage of 350kV was initially used for gun commissioning [2] but, after several failures of the high voltage insulating ceramics [3], it was necessary to install a more robust but smaller inner diameter ceramic, which was loaned to us by Todd Smith at Stanford University, which reduced the maximum gun operating voltage to ~250kV. Furthermore, a field emitter on the GaAs cathode wafer located close to its centre necessitated a reduction of the gun voltage down to 230kV. This field emitter is likely to be responsible for a hole in the quantum efficiency map of the cathode. This hole becomes more pronounced towards the end of the cathode activation cycle but virtually disappears after the cathode re-caesiation (Fig.1). An improved 500kV ceramic insulator is currently being developed and manufactured in collaboration with Jefferson Laboratory and Cornell University that will restore the ALICE gun nominal voltage to 350kV. Figure 1: Typical QE maps at the end of the activation cycle before the re-caesiation (left) and after a full cathode activation including a heat cleaning treatment of the wafer (right). Due to excessive field emission from the main linac module, designed to bring the beam energy to 35MeV [3], the beam energy was reduced to 21MeV for the machine commissioning conducted to date. The corresponding beam energy after the injector was 4.8MeV to allow injection and extraction chicanes to operate correctly. Recent work on extensive SC linac cavity conditioning, improvements in the cryogenic system and optimisation of the linac operating parameters would allow ALICE to operate at a higher beam energy of 25-27MeV in an energy recovery mode and up to ~30MeV in a non- Proceedings of FEL2009, Liverpool, UK TUPC42 FEL Technology I : Accelerator 333