Detail Descriptions of Data Selections and Reductions

The Goal is to extract information on the HRC background when the detector is in the "stowed" position.

For our purposes the stowed position will be anytime that the SIM translation motor step position is greater than zero (TSCPOS > 0).

The detector MCP HV must be on and at the operational level

For the HRC-I, this means:

• MSID 2IMONST is ON (or 1)
• MSID 2IMTPAST is 77
• MSID 2IMBPAST is 89
• MSID 2IMHVLV is in the range 78-82
• MSID 2IMHBLV is in the range 85-88

Some values of Hrc S parameters changed in April 2012.

• MSID 2SPONST is ON (or 1)
• MSID 2SPTPAST is 90 before 2012 / 93 after 2012
• MSID 2SPBPAST is 102 before 2012 / 105 after 2012
• MSID 2SPHVLV is in the range 71-75 before 2012 / 71-73 after 2012
• MSID 2SPHBLV is in the range 78-82 before 2012 / 78-80 after 2012

The configuration of the HRC-I (or HRC-S) matters. Data from the SI_MODE = DEFAULT configuration are the data of interest. For more information on the HRC SI_MODEs (HRCMODE) see:

http://cxc.harvard.edu/contrib/juda/hrc_flight/macros/hrcmode.html

The DEFAULT configuration for each instrument has changed over time. Some of these changes are not expected to have an impact on the background (the WIDTH_THRESHOLD and RANGE_SWITCH_LEVEL parameters) but do have an impact on how the event data are processed.

The HRC-I has been operated in a non-DEFAULT configuration a few times, most notably when we are performing the ACIS undercover background. There can be times after these observations when the stowed background data would be collected in this configuration. these time intervals should not be included.

For the HRC-I the important configuration settings to satisfy are:

• TRIGGER_LEVEL 8 (has been set to other values)
  • Check via MSID 2LLDIALV in the range 130-132
• RANGE_SWITCH_LEVEL 90 or 115
  • Check via MSID 2RSRFALV in the range 171-173 (for 90) or 184-186 (for 115)
• ANTICO_ENABLE YES
  • Check via MSID 2SHLDAVR (part of SCIDPREN in hrcf*_hk0.fits) should be 1
• WIDTH_ENABLE NO
  • Check via MSID 2WDTHAVR (part of SCIDPREN in hrcf*_hk0.fits) should be 0
• WIDTH_THRESHOLD 2 or 3
  • Check via MSID 2WDTHAST value of 2 or 3
• ULD_ENABLE NO
  • Check via MSID 2ULDIAVR (part of SCIDPREN in hrcf*_hk0.fits) should be 0
• UPPER_LEVEL_DISC 255
  • Check via MSID 2ULDIALV in the range 254-255
• BLANK_ENABLE NONE
  • Check via MSID 2EBLKAVR and 2CBLKAVR (part of SCIDPREN in hrcf*_hk0.fits) should both be 0
• U_BLANK_HI 255
  • Check via MSID 2CBHUAST value of 255
• V_BLANK_HI 255
  • Check via MSID 2CBHVAST value of 255
• U_BLANK_LOW 0
  • Check via MSID 2CBLUAST value of 0
• V_BLANK_LOW 0
  • Check via MSID 2CBLVAST value of 0

For the HRC-S the important configuration settings to satisfy are:

• TRIGGER_LEVEL 8 (has been set to other values)
  • Check via MSID 2LLDIALV in the range 130-132
• RANGE_SWITCH_LEVEL 90 or 125
  • Check via MSID 2RSRFALV in the range 171-173 (for 90) or 189-191 (for 125)
• ANTICO_ENABLE NO
  • Check via MSID 2SHLDAVR (part of SCIDPREN in hrcf*_hk0.fits) should be 0
• WIDTH_ENABLE NO
  • Check via MSID 2WDTHAVR (part of SCIDPREN in hrcf*_hk0.fits) should be 0
• WIDTH_THRESHOLD 2 or 3
  • Check via MSID 2WDTHAST value of 2 or 3
• ULD_ENABLE NO
  • Check via MSID 2ULDIAVR (part of SCIDPREN in hrcf*_hk0.fits) should be 0
• UPPER_LEVEL_DISC 255
  • Check via MSID 2ULDIALV in the range 254-255
• BLANK_ENABLE EDGE
  • Check via MSID 2EBLKAVR and 2CBLKAVR (part of SCIDPREN in hrcf*_hk0.fits) should be 1 and 0, respectively
• U_BLANK_HI 74
  • Check via MSID 2CBHUAST value of 74
• V_BLANK_HI 255
  • Check via MSID 2CBHVAST value of 255
• U_BLANK_LOW 69
  • Check via MSID 2CBLUAST value of 69
• V_BLANK_LOW 0
  • Check via MSID 2CBLVAST value of 0

The third HRC "stowed" background to do is for the HRC-S high-precision timing configuration: For the HRC-S in the high-precision timing mode (HRCMODE S_TIMING) the important configuration settings to satisfy are:

• TRIGGER_LEVEL 21 (has been set to other values)
  • Check via MSID 2LLDIALV in the range 137-139
• RANGE_SWITCH_LEVEL 90 or 125
  • Check via MSID 2RSRFALV in the range 171-173 (for 90) or 189-191 (for 125)
• ANTICO_ENABLE NO
  • Check via MSID 2SHLDAVR (part of SCIDPREN in hrcf*_hk0.fits) should be 0
• WIDTH_ENABLE NO
  • Check via MSID 2WDTHAVR (part of SCIDPREN in hrcf*_hk0.fits) should be 0
• WIDTH_THRESHOLD 2 or 3
  • Check via MSID 2WDTHAST value of 2 or 3
• ULD_ENABLE NO
  • Check via MSID 2ULDIAVR (part of SCIDPREN in hrcf*_hk0.fits) should be 0
• UPPER_LEVEL_DISC 255
  • Check via MSID 2ULDIALV in the range 254-255
• BLANK_ENABLE NONE
  • Check via MSID 2EBLKAVR and 2CBLKAVR (part of SCIDPREN in hrcf*_hk0.fits) should both be 0
• U_BLANK_HI 255
  • Check via MSID 2CBHUAST value of 255
• V_BLANK_HI 255
  • Check via MSID 2CBHVAST value of 255
• U_BLANK_LOW 0
  • Check via MSID 2CBLUAST value of 0
• V_BLANK_LOW 0
  • Check via MSID 2CBLVAST value of 0
• SPECT_MODE IMAGING
  • Check via MSID 2SPMDASL (part of SCIDPREN in hrcf*_hk0.fits) should be 0

SCIDPREN has a C-style bit numbering:

The bit-mask filter SCIDPREN=0000xxxx000xxxxx requires the spare bits to be 0.

Given the time intervals when the SIM translation table has the HRC in the "stowed" position, the subset of times for which the HRC-I has the HV on and at the operational level and which satisfies the configuration settings can be found. Similar time intervals can be found for the HRC-S.

A complication in dealing with the HRC serial-digital housekeeping telemetry (the hrcf*_hk0.fits files) comes from "glitches". These can mark nominally good times as bad. There are three types of glitches:

• missing telemetry data
• HRC secondary-science FIFO resets that accompany all telemetry changes and detector configuration changes
• HRC secondary-science data corruption due to elevated temperature

In principle, the QUALITY bit-array flags the first type of glitch. The second can be at least partially identified by non-zero values to the spare bits in SCIDPREN. A bit-mask check of

SCIDPREN=0000xxxx000xxxxx

should remove some of these second type of glitch. The third type are harder to spot but I have had some success with using MSID 2SMTRATM (the selected motor temperature). Normally, there is no motor selected and the value floats to some arbitrary value. The corruption of the data stems from bytes in the secondary science FIFO getting duplicated and the two bytes preceding 2SMTRATM are spares that stay at a "high" value. A reading of 55-56 for 2SMTRATM indicates corrupted data. For more information on this data corruption see:

http://cxc.harvard.edu/contrib/juda/memos/anomaly/sec_sci/index.html

and

http://cxc.harvard.edu/contrib/juda/memos/anomaly/sec_sci/byte_shift.html

For each interval the secondary science rate data should be extracted and merged into a single file for the interval. From each of these interval files the mean, sigma, min, and max of the total (TLEVART) and valid (VLEVART) MCP rates should be determined and incorporated into a table. This will permit investigation of the time history of the background and any potential changes in the valid/total ratio. It will probably be necessary to iteratively clip the rates when calculating the statistics to avoid outliers.

Processing the event data from each interval will require specifying the values for the keyword RANGELEV to do the AMP_SF correction. While earlier I described using time to divide between when it is appropriate to use 90 or 115 the automatic way to do it is to set the value based on MSID 2RSRFALV, which should be essentially constant over the interval. The prescription for the value of RANGELEV is:

RANGELEV = (int)((mean(2RSRFALV) - 127) * 2 + 0.5)

It is also necessary to specify the value of the keyword WIDTHRES to obtain the best tap-ringing correction. Its value is determined by the value of MSID 2WDTHAST, which should be constant during the interval. Its prescription is:

WIDTHRES = (int)(mean(2WDTHAST) + 0.5)

To run hrc_process_events, we also set following parameters.

Hrc I uses a different gain file each year starting September of the year.

For HRC S, there is only one gain file.

A separate level 1 type event file should be made for each of the stowed-background intervals. These can later be merged into larger data sets based on time or other discriminators.

Last modified: Mon, 14 Jan 2019 16:33:18