A microcomputer-based instrument for the detection and analysis of precession motion : in a gas centrifuge machine

The Centrifuge Procession Analyzer (CPA) is a microcomputer-based instrument which detects precession motion in a gas centrifuge machine and calculates the amplitude and frequency of precession. The CPA consists of a printed circuit board which contains signal-conditioning circuitry and a 24-bit counter and an INTEL iSBC 80/24 single-board computer.

Precession motion is detected by monitoring a signal generated by a variable reluctance pick-up coil in the top of the centrifuge machine. This signal is called a Fidler signal. The initial Fidler signal triggers a counter which is clocked by a high-precision, 20.00Q000-MHZ, temperature-controlled, crystal oscillator. The contents of the counter are read by the computer and the counter reset after every ten Fidler signals. The speed of the centrifuge machine and the amplitude and frequency of precession are calculated and the results are displayed on a liquid crystal display on the front panel of the CPA.

The thesis contains results from data generated by a Fidler signal simulator and data taken when the centrifuge was operated under three test conditions:

1. Nitrogen gas during drive-up, steady state, and drive-down,

2. Xenon gas during slip test, steady state, and the addition of gas, and

3. No gas during steady state.

The qualitative results v/ere consistent with experience with centrifuge machines using UF₆ in that the amplitude of precession increased and the frequency of precession decreased during drive-up, drive-down and the slip check. The magnitude of the amplitude and frequency of precession were proportional to the molecular weight of the gases in steady state.