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XMM-Newton CCF Release Note
XMM-CCF-REL-219
EPIC PN FIFO over ow deadtime parameters
R. D. Saxton
5 July 2006
1 CCF components
Name of CCF VALDATE EVALDATE Blocks changed XSCS ag
XMM MISCDATA 0022.CCF 2000-01-01 MISCDATA NO
2 Changes
A set of parameters have been added which record the deadtime incurred when a FIFO
reset or over ow occurs in the PN camera. The deadtime is observing-mode-dependent
and the following values have been set:
FIFO_DEADTIME_FF=0.22s - dead time produced by a FIFO reset in FullFrame mode
FIFO_DEADTIME_EF=0.22s - dead time produced by a FIFO reset in ExtFF mode
FIFO_DEADTIME_LW=0.22s - dead time produced by a FIFO reset in LargeWindow mode
FIFO_DEADTIME_SW=0.10s - dead time produced by a FIFO reset in SmallWindow mode
FIFO_DEADTIME_TI=0.10s - dead time produced by a FIFO reset in Timing mode
FIFO_DEADTIME_BU=0.10s - dead time produced by a FIFO reset in Burst mode
3 Scientic Impact of this Update
These keywords are read by epframes and are necessary to correctly account for dead time
eects incurred when FIFO resets or over ows occur. The cumulative dead time due to
this eect can be signicant in the case of many resets, causing the exposure time to be
overestimated and hence source ux to be underestimated. epframes will use these values
to either write GTIs (if the exact times of such FIFO resets can be reconstructed) or to
reduce the FRACEXP values in the EXPOSUnn extensions.
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4 Estimated Scientic Quality
The initial values are rough estimates of the true dead time losses. Additional ground-
based calibrations are planned which will likely lead to revised values.
5 Test procedures and results
The new CCF le has been tested with the EPIC-pn pipeline and has been found to be
compatible with the SAS.
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