In a fixed-field alternating-gradient (FFAG) accelerator, eliminating pulsed magnet operation permits rapid acceleration to synchrotron energies, but with a much higher beam-pulse repetition rate. Conceived in the 1950s, FFAGs are enjoying renewed interest, fuelled by the need to rapidly accelerate unstable muons for future high-energy physics colliders. Until now a ‘scaling’ principle has been applied to avoid beam blow-up and loss. Removing this restriction produces a new breed of FFAG, a non-scaling variant, allowing powerful advances in machine characteristics. We report on the first non-scaling FFAG, in which orbits are compacted to within 10 mm in radius over an electron momentum range of 12–18 MeV/c. In this strictly linear-gradient FFAG, unstable beam regions are crossed, but acceleration via a novel serpentine channel is so rapid that no significant beam disruption is observed. This result has significant implications for future particle accelerators, particularly muon and high-intensity proton accelerators.

The ALICE accelerator, the first energy recovery machine in Europe, has recently demonstrated lasing of an infra-red free electron laser (IR-FEL). The current status of the machine and recent developments are described. These include: lasing of the IR-FEL, a programme of powerful coherent terahertz radiation research, electro-optic diagnostic techniques, development of high precision timing and distribution system, implementation of digital low level RF control. ALICE also serves as an injector for the EMMA non- scaling FFAG machine.

Progress made in ALICE (Accelerators and Lasers In Combined Experiments) commissioning and a summary of the latest experimental results are presented in this paper. After an extensive work on beam loading effects in SC RF linac (booster) and linac cavities conditioning, ALICE can now operate in full energy recovery mode at the bunch charge of 40pC, the beam energy of 30MeV and train lengths of up to 100us. This improved operation of the machine resulted in generation of coherently enhanced broadband THz radiation with the energy of several tens of uJ per pulse and in successful demonstration of the Compton Backscattering x-ray source experiment. The next steps in the ALICE scientific programme are commissioning of the IR FEL and start of the research on the first non-scaling FFAG accelerator EMMA. Results from both projects will be also reported.

The Muon Ionisation Cooling Experiment (MICE) is being constructed at Rutherford Appleton Laboratory in the UK. A muon beam will be cooled through a process of absorption using hydrogen absorbers then accelerated using 200MHz copper RF cavities. This paper describes the RF power source used to accelerate the muon beam, testing of the high voltage power supplies and amplifiers to date and progress on the RF distribution scheme to the accelerating cavities.

EMMA is a prototype non-scaling FFAG that requires a demanding RF system. Production for the final RF system is due for completion in Summer 09 and high power testing of initial hardware has taken place. This paper describes the high power verification tests using a similar IOT transmitter, a prototype waveguide section coupling to two RF cavities. In order to understand potential levels of control a digital phase control system was used to determine feasible values of control.

ALICE (Accelerators and Lasers in Combined Experiments) is a proof of concept energy recovery linac (ERL) accelerator, which incorporates two superconducting radio frequency (SRF) cryomodules each with two identical 9-cell cavities. The first cryomodule, the Booster provides the acceleration for the injected beam into the ERL section of the accelerator where the second module, the Linac accelerates the beam to its required energy. The conditioning of these SCRF cavities has previously been reported; this paper describes the experiences gained during the commissioning of ALICE.

ALICE (Accelerators and Lasers in Combined Experiments) is a 35 MeV energy recovery linac based light source. ALICE is being developed as an experimental test-bed for a broad suite of science and technology activities that make use of electron acceleration and ultra-short pulse laser techniques. ALICE utilises two super-conducting radio frequency (SRF) cryomodules, each with two identical 9-cell, 1.3 GHz cavities that are powered by 5 inductive output tubes (IOTs) from 3 different commercial suppliers. The experience gained in both commissioning these systems and ultimately operating for energy recovery is presented. Developments for a new ERL cryomodule upgrade for ALICE are also described.

The Energy Recovery Linac Prototype (ERLP) is being commissioned at Daresbury Laboratory (UK) to develop and demonstrate energy recovery to produce IRFEL radiation using SRF technology. The ERLP uses two identical Linac cryomodules, one as a booster cavity accelerating the beam to 8.35 MeV, the other as a linac module in the re-circulating loop with an energy gain of 26.5 MeV. Each module consists of two 9-cell cavities operating at a frequency of 1.3 GHz and at a temperature of 2 K. As there is no energy recovery in the booster it requires a peak power of 52 kW, whereas the linac module only requires 12 kW. The cryomodules are cooled to 2 K by a cryo-system consisting of a 4 K liquefier, 2 K recuperator with a JT valve and external vacuum pumps. In this paper we report our initial experiences in operating the SRF Linacs particularly with cryogenics and RF systems.

The Muon Ionisation Cooling Experiment (MICE) RF test stand is being assembled at Daresbury Laboratory. This will provide a test bed for power amplifiers to produce the 2MW 200MHz RF for the MICE experiment RF cavities. Initial design and proposed layout of the RF system are described.

The Energy Recovery Linac Prototype (ERLP) being constructed at Daresbury Laboratory will use an analogbased low level RF (LLRF) control system designed and built at FZR Rossendorf. Once the machine is operating, the testing and development of a digital LLRF feedback system will take place using the ERLP as a test bed.

Higher order mode (HOM) wakefields building up in the SCRF cavities are likely to be a major factor in 4GLS. A series of measurements of the HOMs of the SCRF cavities at the ELBE light source has been performed. The power extracted by the HOM couplers over a wide band- width (1.7GHz -2.9GHz) has been measured using a spectrum analyser, for various bunch trajectories through the cavities. Network analysers have also been used to determine the external Q of these modes. These meas- urements will be used to estimate the dominant modes which will require significant damping for 4GLS.