TIDE/PSI Description: PSI Gas Feed System

Reference: Moore, T.E., C. R. Chappell, M. O. Chandler, S. A. Fields, C. J. Pollock, D. L. Reasoner, D. T. Young, J. L. Burch, N. Eaker, J. H. Waite, Jr., D. J. McComas, J. E. Nordholt, M. F. Thomsen, J. J. Berthelier, and R. Robson, The Thermal Ion Dynamics Experiment and Plasma Source Instrument, Space Sci. Rev., 1995.

PSI Gas Feed System

The feed system consists of the storage tanks, valves, pressure regulators, flow impedance, and pressure transducers required to provide the source with a steady-state 0.5-sccm flow rate. Its overall layout is illustrated in Figure 10. The Xenon gas supply is contained in two pressure vessels located symmetrically on the spacecraft to maintain balance and provide gas flow over the anticipated range of temperature. The storage tanks are a pair of 4.8 liter, cylindrical high pressure vessels rated for 3100 psi. The tankage is fitted with high and low pressure transducers (to indicate the quantity of remaining expellant) and a manually operated fill valve. The nominal gas supply is 3.5 kg, or 600 standard liters, of Xenon, which is sufficient for 20,000 hr. of continuous operation at the specified flow rate. The valves and regulators reduce the pressure to 10 psi which is applied to the upstream side of a constant flow impedance plug to maintain a flow rate into the cathode of 0.5 std cm3/min., or 0.37 micro mole/s. Saturation ion current is 1.0 mA; hence, the maximum ion production efficiency is approximately 3%.

a larger version is available
Figure 10. PSI Gas Feed System block diagram.

The Xenon flows from the tank through a high-pressure valve to the pressure regulator. The pressure regulator reduces the Xenon pressure to a constant 10 psi. The 10 psi is applied to the upstream side of a constant flow impedance to maintain a steady state flow rate of 0.5 sccm. No low-pressure valve is provided to turn the flow to the plasma source on/off, so the high pressure valve must be turned off in advance of the desired shut down time so that the small volume of high pressure Xenon left downstream of the valve can be scavenged.

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Created: March 1996, Updated: August 2008

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