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[Snowden et al.1992],
et al.1993, Plucinsky
The PSPC rejection efficiency for particle events is very high, and leaves a residual count rate of only countss , countss cm keV or countss arcmin keV . About 77% of events originate in the detector while the remainder enter through the counter window. During typical conditions, the count rate of residual events is well correlated with the master veto rate. The master veto is the anticoincidence counter for the selection of accepted events.
The PSPC rejection efficiency for particle background events in the pulse height channel range 18-249 is well described by a power-law, a flat component, and an Al K line at 1.5 keV. Typically, the ratio between the power-law and the flat components remains constant to , while the relative Al K contribution increases with increasing master veto rate. The spatial distribution of counts with pulse heights >18 is uniform over the field of view except for a small radial gradient for the internally-produced component and shadowing of the externally-produced components (Al K line and flat continuum) by the window support structure. During observations in low gain mode the particle background can also be monitored by the count rate in channels 260-370, since essentially all of these events are produced by particles.