Field Emission Measure During cERL Main Linac Cryomodule High Power Test in KEK

A compact Energy Recovery Linac (cERL) is under construction at KEK in order to test the performance of the key components required for the future ERL project. The main linac L-band cavities were assembled and tested in the cryomodule under high power operation. During the test, information concerning field emission were gathered by using PIN diodes rings and NaI scintillator located at the cavities ends. With Si PIN diodes, it is possible to observe the radiation pattern produced by field emission, inferring the meridian where the emitter belongs. On the other hand, the bremsstrahlung spectra recorded with the scintillator allow estimation of the longitudinal emitter location. The data were analyzed by means of simulations, taking into account the cavities operating conditions and interactions between the accelerated electrons and the cavity surface. The resulting information are used to monitor the cavity performance and to deduce a possible emitter location.