I. Ben-Zvi

The ALPI project at the Laboratori Nazionali di Legnaro

Abstract The project of a superconducting linac acting as booster of the LNL-XTU tandem is briefly discussed. Experience with lead plated quarter wave resonators is discussed together with the machine configuration.

The control and electronics of a superconducting booster module

Abstract The computer control system and the electronics hardware of the superconducting booster module recently installed at the Weizmann Institute of Science Pelletron accelerator laboratory are described. The resonators rf controllers and the control system software are described in detail.

A proposal for a tandem accelerator FEL experiment

Abstract A proposal for an FEL experiment, based on a tandem electrostatic accelerator, is presented. The proposed FEL is designed to operate at harmonic frequencies in a quasi-cw mode. An internal wiggler scheme is planned to be used, based upon a strong planar wiggler ( a w > 1), positioned in the high voltage terminal of a HVEC model EN tandem accelerator. The electron beam enters the wiggler at the natural injection angle ( a w / γ ). This approach provides a relatively simple and compact FEL system that will be used as a research tool for studying harmonic operation of FELs and investigating post-saturation laser dynamics and efficiency enhancement. The exceptional electron beam quality and long pulse characteristics of electrostatic accelerators give a special advantage to such an experimental scheme as a means for exploring the ultimate performance parameters of FELs.

Superconducting booster module using quarter wave resonators

Abstract A superconducting booster module has been recently installed at the Weizmann Institute of Science. The module consists of four β0 = 0.095 quarter wave resonators housed in a cylindrical vertical cryostat. Additional components of the system are a chopper buncher, control electronics and a helium refrigerator. The booster resonators have been operated continuously at a field gradient of 3 MV/m, providing a total accelerating voltage of 2 MeV/charge. Oxygen and carbon beams have been accelerated, and the module is being used in nuclear physics experiments.

Development of a tandem electrostatic accelerator quasi-cw FEL

Abstract The EN tandem electrostatic accelerator at the Weizmann Institute of Science has been converted into an electron accelerator with beam power recovery. We report on the design and performance of the accelerator as well as on a new approach to stable, long-pulse operation of this class of machines. The long-pulse model of operation offers interesting possibilities for the operation of free electron lasers, in particular the study of high-coherence, single-mode operation.

Design of a tandem accelerator free electron laser

Abstract The motivation for using a tandem electrostatic accelerator as an electron accelerator for a free electron laser (FEL) is presented. The adaptation of the HVEC EN tandem at the Weizmann Institute for this purpose, electron beam optics and nonlinear FEL computation relevant for this FEL realization are described. In the tandem configuration the terminal is held at a positive potential. The electron beam is accelerated from ground potential to the terminal in one beam tube and then decelerated down the other beam tube. The FEL wiggler and cavity are at the terminal. Due to the beam energy recovery this scheme produces a high power beam at the terminal with a small investment in electrical power.

Performance tests of a superconducting quarter wave resonator

Abstract The performance of a superconducting quarter wave resonator, suitable for heavy-ion linac use, has been tested. The resonator was built using the lead-plated copper scheme. Measured performance established the anticipated advantages of this structure in such an application. The Q value of 2 × 10 8 is independent of the average accelerating gradient up to 3 MV/m where the onset of field emission dominates the losses. Excellent short term frequency stability accounts for the fact that the resonator can be phase-locked with as little as 2 W of tuning power at 2.5 MV/m.

Current leads for HERA

Abstract Three prototypes of current leads (6500 A, 10 × 100 A and 4 × 100 A) for the HERA accelerator were designed, built and tested. The measured total cooling load of these current leads in the refrigerator mode of operation was 3.2, 3.9 and 2.4 W/kA, respectively. Subsequently, these current leads were produced in quantity by a commercial outfit and they are now in the process of assembly within the HERA cryogenic systems in DESY. The essential technical details and experimental results are described.

Superconducting linear accelerator cryostat

Abstract A large vertical cryostat for a superconducting linear accelerator using quarter wave resonators has been developed. The essential technical details, operational experience and performance are described.

Large diameter horizontal helium cryostats

Abstract The designs of two, large, horizontal helium cryostats with vapour cooled radiation shields (a gravitational wave detector cryostat and an accelerator cryostat) are described. The problems of cooling heavy inserts and large vertical indium seals with stainless steel fianges are discussed.