ADPF spoke cavity cryomodule concept

The Accelerator Driven Test Facility (ADTF) is being developed as a reactor concepts test bed for transmutation of nuclear waste. A 13.3 mA continuous-wave (CW) proton beam will be accelerated to 600 MeV and impinged on a spallation target. The subsequent neutron shower is used to create a nuclear reaction within a subcritical assembly of waste material that reduces the waste half-life from the order of 10{sup 5} years to 10{sup 2} years. Additionally, significant energy is produced that can be used to generate electrical power. The ADTF proton accelerator consists of room-temperature (RT) structures that accelerate the beam to 6.7-MeV and superconducting (SC) elements that boost the beam's energy to 600-MeV. Traditional SC elliptical cavities experience structural difficulties at low energies due to their geometry. Therefore, stiff-structured SC spoke cavities have been adopted for the energy range between 6.7 and 109 MeV. Elliptical cavities are used at the higher energies. This paper describes a multi-spoke-cavity cryomodule concept for ADTF

Design of a [Beta]=0.175 2-Gap Spoke Resonator

In this paper, we present the electromagnetic and structural design of a low-b superconducling spoke resonator for a beam-test in the Low Energy Demonstration Accelerator (LEDA). This test is part of the Advanced Accelerator Applications (AAA) project. Recently, the sole use of superconducting resonators from 6.7 MeV on has been approved for this project. The beam test will use the lowest- resonator from this accelerator design. The choices of the cavity dimensions are driven by its use imrnediately after the LEDA Radio-Frequency Quadrupole (RFQ). The frequency is 350 MHz, the lengt corresponds to a geometric p (Ps) of 0.175. Our design approach has been to carry out an integrated RF and mechanical design from the start. The final cavity is well understood in terms of IW: and mechanical properties. The RF properties, like Q, WQ, peak surface fields and acceleration efficiency are very reasonable for such a low- structure. 'The design also includes power coupler, vacuum and pick-up ports and lheir influences. The mechanical design added tuning sensitivities, tuning forces, stiffening schemes and the understanding of stresses under various load conditions. This presentation reflects changes in the coupling port and the beam aperture compared to a previously presented design

Status of the LANL Activities in the Field of RF Superconductivity.

Since the last workshop we have tested six b=0.64, 700 MHz, 5-cell elliptical superconducting cavities in collaboration with JLAB in vertical cryostats. All the cavities exceeded the requirements for Accelerator Production of Tritium (APT) (Q0 = 5 x 109 at Eacc = 5 MV/m) with ample margin. The low-field Q0 at 2 K was 2-3 x 1010 and the maximum accelerating field reached 12 MV/m, which corresponds to peak electric and magnetic fields of 41 MV/m and 835 Oe, respectively. Power couplers have also been tested in a test bench up to over 1 MW. Since the APT project has transitioned to Advanced Accelerator Applications (AAA) project, a new type of superconducting accelerating structure called spoke cavity emerged as an excellent candidate for the low energy sections between the RFQ and the elliptical cavities. We tested a b=0.29, 340 MHz, 2-gap spoke cavity on loan from Argonne National Laboratory. The results showed Q0 = 2 x 109 at low fields and a maximum accelerating field Eacc = 12.5 MV/m at 4 K. At 5 MV/m, the Q0 was 1.5 x 109. Encouraged by these results, we started fabricating some spoke cavities and are planning to test one of them in the beamline of LEDA (Low Energy Demonstration Accelerator) in the future