Superconductive activities at COSY FZJ

Abstract

A shielded test facility has been constructed to allow RF tests of superconductive (sc) cavities. Measurements of sc cavities are possible up to 500 W in a frequency range from 80 MHz to 1 GHz. Additionally a 25 kW TV transmitter has been installed together with a high power circulator. The first sc experience has been made at a 5-cell 500 MHz, beta = 0.75 test cavity for the ESS. First quasi-static measurements using the 500 W broadband amplifier almost verified the design values of Q(sub 0) = 2 x 10(exp 9) and E(sub acc) greater than 5 MV/m. The tuning system of the cavity consists of a coarse system driven by a stepper motor and a piezoelectric fine tuner. The piezoelectric tuning system has been used to record the spectrum of mechanical resonances of the cavity. Furthermore, dynamical data of the Lorentz force detuning have been taken during pulsed-mode operation at a repetition rate of 50 Hz. First results of active compensation of the Lorentz force detuning, using the fast piezo frequency control system, are presented. A digital diagnostic tool has been added to measure the phase in the order of 0.1 deg which will be required for a fast digital control system. A vertical cryostat down to 2 K will be installed in the test area to perform studies for the planned multicell spoke-type, elliptical cavities and QWRs. The QWRs are proposed for the LINAC project, which will feed the Cooler Synchrotron COSY with protons and deuterons up to 50 MeV.