Superconducting RF Cavity Frequency and Field Distribution Sensitivity Simulation
Frequency and electromagnetic field distribution sensitivity of a superconducting RF (SRF) cavity are the fundamental phyical paramethers in cavity and tuner design. At low temperature, the frequency sensitivity can be obtained by measuring prototype cavity, but it is not easy to test the filed distribution sensitivity. This paper presents and describes a simulation method combining ANSYS and SUPERFISH to calculate the cavity frequency and field distribution variation due to cavity’s small deformation caused by mechanical force, radiation force, thermal expansion etc.. As an example, the simulation results of the frequency and field flatness sensitivity on the SNS cavities were confirmed by their test results.
ELLIPTICAL SRF CAVITY DESIGN FOR PEFP EXTENSION
To increase the beam energy up to 1 GeV by extending a PEFP 100-MeV proton linac, a study on the superconducting RF linac is underway. SRF technology is chosen due to its operational flexibility and lower beam loss, as well as its high accelerating performance and low operating cost. Preliminary study on the beam dynamics shows that two types of cavity with geometrical beta of 0.50 and 0.74 can cover the entire energy range from 100 MeV to 1 GeV. Assuming the achievable peak surface electric field to be 30 MV/m and 35 MV/m for medium and high beta cavity, respectively, we designed the sixcell elliptical cavities by optimizing the cavity parameters such as peak field ratio, inter-cell coupling and r/Q through the geometrical parameter sweep. The details of the SRF cavity design for PEFP extension will be presented.
The REX-ISOLDE project
The Radioactive Beam Experiment REX-ISOLDE [1–3] is a pilot experiment at ISOLDE (CERN) testing the new concept of post acceleration of radioactive ion beams by using charge breeding of the ions in a high charge state ion source and the efficient acceleration of the highly charged ions in a short LINAC using modern ion accelerator structures. In order to prepare the ions for the experiments singly charged radioactive ions from the on-line mass separator ISOLDE will be cooled and bunched in a Penning trap, charge bred in an electron beam ion source (EBIS) and finally accelerated in the LINAC. The LINAC consists of a radiofrequency quadrupole (RFQ) accelerator, which accelerates the ions up to 0.3 MeV/u, an interdigital H-type (IH) structure with a final energy between 1.1 and 1.2 MeV/u and three seven gap resonators, which allow the variation of the final energy. With an energy of the radioactive beams between 0.8 MeV/u and 2.2 MeV/u a wide range of experiments in the field of nuclear spectroscopy, astrophysics and solid state physics will be addressed by REX-ISOLDE.