Improvement of the energy resolution of a time-of-flight neutron spectrometer by using a high energy rf buncher

Abstract In order to improve the overall energy resolution of the time-of-flight (TOF) neutron spectrometer we have built a high energy (HE) rf buncher for the 7 MV HVEC tandem of Bruyeres-le-Châtel. To optimize the matching of the low energy and high energy bunchers, some modifications have been done on the existing facility. The HE buncher consists of a cylindrical mono-gap cavity, the diameter of which is 0.4 m and the length 1 m. The Q factor is 1.5 × 10 4 and the working frequency 162 MHz. In this paper we describe the overall installation and the feedback loops used to stabilize the frequency and the rf phase. Preliminary results show that the measured bunch compression is in agreement with the calculated values and the use of the phase feedback loop suppresses the transit time jitter in a very efficient way.