A COUPLED RFQ-IH CAVITY FOR THE NEUTRON SOURCE FRANZ

The Frankfurt Neutron Source at the Stern-GerlachZentrum (FRANZ) [1] delivers neutrons in the energy range from 1 to 300 keV at high intensities. The neutrons are produced using the the 7 Li(p, n) 7 Be reaction with 2 MeV protons. The linac accelerator cavities (Table 1) consist of a 4-rod-RFQ [2] coupled with an 8 gap interdigital H-type drift tube [3] section with a total cavity length of 2.3 m (Fig. 1). It accelerates the 120 keV beam to 2.03 MeV at a frequency of 175 MHz. The combined cavity will be powered by one RF amplifier to reduce investment and operation costs. The inductive power coupler will be located at the RFQ part. The coupling into the IH section is provided by direct inductive coupling within the cavity. The coupled RFQ-IH combination is investigated with CST-MWS-simulations [4] and by an RF model. The linac combination has to match the resonance frequency, flatness along the RFQ and the voltage ratio between both cavity sections. Beam operation will be cw (a few mA) and pulsed 250 kHz, 50 ns (up to 50 mA and beyond). The thermal cavity losses are about 200 kW and the cooling is the challenging topic.