Proton-Recoil Proportional Counter Tests at Treat

A methane filled proton-recoil proportional counter will be used as a fission neutron detector in the fastneutron hodoscope. To provide meaningful fuel-motion information the proportional counter should have: a linear response over a wide range of reactor powers (space charge effects are minimized); a good signal-to-background ratio (the number of high energy neutrons detected must be maximized relative to low energy neutrons, and the gamma ray sensitivity must be kept small); and a detector efficiency for fission neutrons above 1 MeV of approximately 1%. In addition, it is desirable that the detector and the associated amplifier/discriminator be capable of operating at counting rates in excess of 500 kHz. This paper reports on tests that were conducted on several proportional counters at the TREAT reactor. The goal of these tests was the determination of a set of counter parameters that would optimize fuel motion detection. The results show that a proton-recoil proportional counter with a methane gas pressure of 0.5 MPa, a counter diameter of 25.4 mm, an anode wire diameter of 0.0504 mm, and a length of 200 mm will be able to meet most of the hodoscope detector requirements.