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Exposure correction is performed by dividing the values in the input
data by an exposure time. CORRECT attempts to get an exposure time from
three sources, in order,
- The EFF_EXPOSURE component of the input dataset header
- The EXPOSURE_TIME component of the input dataset header
- From the user using the TEXP parameter
Dead time correction is only performed if a valid LIVE_TIME structure
is defined in the dataset. This contains 3 components, the ON, OFF and
DURATION. The first two list the start and stop times during which the
detector was exposed to a "source". The last component is the time for
which the detector would actually have been able to register a count.
DURATION(i) is generally less than OFF(i)-ON(i) for photon counting
detectors due to dead time in the counting electronics. CORRECT applies
dead time correction slightly differently depending on whether the
input dataset contains a time axis.
If no time axis is present, the sum of (OFF-ON)/DURATION provides a
dead time correction factor which is the same for every bin. The
presence of a time axis causes this correction to be applied in for
each time bin individually.
Web Master
Tue Oct 7 10:18:50 BST 1997