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5.2 Performance of the HRI


The ROSAT high-resolution imager HRI\ is very similar to the Einstein Observatory HRI   and is comprised of two cascaded microchannel plates (MCPs) with a crossed grid position readout system.

The detector performance can be characterized by such parameters as those listed in Table5.1. Two significant changes from the Einstein instrument that have affected the performance of the detector are: the substitution of CsI for MgF tex2html_wrap_inline17177 as the detector photocathode, and the introduction of a thin aluminum-coated plastic membrane (the ``electrostatic shield'') near the front MCP (in addition to the UV/Ion shield which is situated farther in front of the detector).


Field of View 38 arc minutes (square)
Spatial Resolution 1.7 arc seconds (FWHM)
Quantum Efficiency 30 percent at 1 keV
Window Transmission 75 percent at 1 keV
Background tex2html_wrap_inline17179 internal
(counts arcmin tex2html_wrap_inline17181 s tex2html_wrap_inline17183 ) tex2html_wrap_inline17185 external tex2html_wrap_inline17187
tex2html_wrap_inline17189 XRB tex2html_wrap_inline17191
tex2html_wrap_inline17193 Typical Total
Temporal Resolution 61 tex2html_wrap_inline17195 sec
Dead Time 0.36 to 1.35 msec
tex2html_wrap_inline17197 Depending upon orbital location. tex2html_wrap_inline17199 Depending upon viewing direction.
Table 5.1:  ROSAT HRI performance summary

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