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XMM EPIC Cal-Ops Meeting
7 November 2001

Even Newer MOS modes since last meeting Tony Abbey - Leicester University Ed Serpell - ESOC Graphics by Ed and Steve


Bright Timing Mode
· Written to cope with bright objects - eg Crab · Allows detailed timing investigation by avoiding counting mode. · Compare pile up & spectral performance with normal timing mode to help with calibration. · Three ` flavours'of binning and discard: · Discard 9 rows, readout 1 row, cut 10:1, resolution 1.75ms · Discard 90 rows, bin 10 rows, cut 10:1, resolution 2.76ms · Discard 95 rows, bin 5 rows, cut 20:1, resolution 2.76ms · Compared with normal timing: · 100 rows and readout, no cut, resolution 1.75ms Bin · Tested on XMM on Crab during rev 333 - 3 October 2001


Crab - rev 333 - Bright timing mode tests
· Rev 0234 MOS1 - exposure id 0135730701- U009
Normal timing mode for comparison - excessive pile up and data rate

· MOS1 - exposure id 0137550801:
· U002 - 10:1 br. timing short exposure - peripheral CCDs active · U003 - 10:1 br. timing peripheral CCDs disabled · U004 - 10:1 compressed br. timing mode, peripherals disabled

· MOS2 - exposure id 0137550801:
· U003 - 90:10 br. timing - peripheral CCDs active for radiation monitoring. · U004 - 95:5 br. timing - peripheral CCDs active for radiation monitoring


Crab - rev 234 - Normal timing mode
MOS1 U009 Normal timing bin together100 rows Event rate 1300/s, bit rate 64kb/s Some low energy noise. Counting mode and FIFO full errors.


Crab - rev 333 - Bright timing mode
MOS1 U003 bright timing 10:1 event rate 3450/s, bit rate 17.5kb/s Low energy noise and missing rows - not yet understood. Counting mode and FT-coarse jump.


Crab - rev 333 - Bright timing mode
MOS1 U004 bright compressed timing 10:1 Low energy noise, but no missing rows. No counting mode or FTcoarse jump


Crab - rev 333 - Bright timing mode
MOS2 U003 bright timing 90:10 Outer CCDs active Event rate 3070/s, bit rate 14kb/s Low energy noise Counting mode and FT-coarse jump.


Crab - rev 333 - Bright timing mode
MOS2 U004 bright timing 95:5 Outer CCDs active Event rate 3350/s, bit rate 8kb/s Considerable low energy noise One counting mode glitch No FT-coarse jumps


Crab - rev 333 - Bright timing mode
Comparison of pile up and performance in the different modes by comparison of pattern fractions. Note that the pointing may have been a bit offset for the normal timing resulting in the left and right diaparity. Bright 95:5 nearly achieves the same ratios as normal mode, while dramatically reducing the data rates
Timing mode type Normal Bright 10:1 Bright 90:10 Bright 95:5 Monopixels Bipixels Left tripixels % % % 83.8 77.0 82.0 82.5 3.51 8.8 7.6 7.2 9.63 7.1 5.1 5.1 Right tripixels % 3.51 7.1 5.2 5.2


Crab - rev 333 - Bright timing mode
And finally, the next slide shows the Crab pulsar phases in 10:1 and 95:5 modes, showing it really works - thanks Ed! Further work is required to investigate some of the noises seen in these modes, but the 95:5 mode looks set to be a useful tool for looking at bright sources with the MOS cameras and achieving good time resolution without exceeding the telemetry bandwidth.


Crab - rev 333 - Bright timing mode