Apply/Remove ACIS PHA Randomization

Overview

Last Update: 8 Feb 2008 - added deprecated thread message to Synopsis

Synopsis:

This thread has been deprecated and will be removed in the next CIAO release. Instead of running this thread, follow the Reprocessing Data to Create a New Level=2 Event File thread.

For some observations, the way PHA channels are converted to PI channels will cause an aliasing problem in the final binned spectra. Randomizing the PHA distribution alleviates this effects; see the Background Information section for details. Similarly, one could remove the randomization from a file that has already had it applied. Since half an ADU is much smaller than the energy resolution at all energies, disabling the PHA randomization should not significantly affect CCD spectra.

Purpose:

To generate a new level=2 event file with PHA randomization applied (or removed). Removing the PHA randomization should only be done by advanced users who know exactly what they are doing.

Read this thread if:

you are working with an ACIS observation and would like to apply or remove the randomization.

Related Links:

• Analysis Guide: ACIS Data Preparation

Parameters for /home/username/cxcds_param/acis_process_events.par


#--------------------------------------------------------------------------
#
#  acis_process_events.par- Parameter file for acis_process_events program
#
#--------------------------------------------------------------------------
        infile = acisf01838_000N002_evt1.fits   Input event file or stack
       outfile = acis_1838_new_evt1.fits Output event file name
    acaofffile = NONE             aspect offset file ( NONE | none | <filename>)
    (apply_cti = yes)             Apply CTI adjustment?
  (apply_tgain = yes)             Apply time-dependent gain adjustment?
(alignmentfile = )acaofffile -> NONE) sim/fam alignment file ( NONE | none | <filename>)
      (obsfile = NONE)            obs.par file for output file keywords ( NONE | none | <filename>)
      (geompar = geom)            Parameter file for Pixlib Geometry files
      (logfile = stdout)          debug log file ( STDOUT | stdout | <filename>)
    (gradefile = CALDB)           grade mapping file ( NONE | none | CALDB | <filename>)
     (gainfile = CALDB)           acis gain file ( NONE | none | CALDB | <filename>)
   (badpixfile = acis_1838_new_bpix1.fits) acis bad pixel file ( NONE | none | <filename>)
   (threshfile = CALDB)           split threshold file ( NONE | none | CALDB | <filename>)
      (ctifile = CALDB)           acis CTI file ( NONE | none | CALDB | <filename>)
    (tgainfile = CALDB)           gain adjustment file ( NONE | none | CALDB | <filename>)
     (eventdef = )stdlev1 -> {d:time,s:ccd_id,s:node_id,i:expno,s:chip,s:tdet,f:det,f:sky,s:phas,l:pha,l:pha_ro,
f:energy,l:pi,s:fltgrade,s:grade,x:status}) output format definition
   (doevtgrade = yes)             Determine event flight grade?
 (check_vf_pha = no)              Check very faint pixels?
(calc_cc_times = no)              Estimate the times of arrival for CC-mode observation?
        (trail = 0.027)           Trail fraction
     (spthresh = 13)              Default split threshold level (overridden by values in threshfile)
  (time_offset = 0)               Offset to add to event time field to synch w/ fam data
   (docentroid = no)              Determine pixel centroid for coord. conversion?
 (calculate_pi = yes)             perform pha->pi conversion? (requires gain file)
 (pi_bin_width = 14.6)            Width of Pi bin in eV
  (pi_num_bins = 1024)            Number of values to bin energy into
 (max_cti_iter = 15)              Maximum iterations for the CTI adjustment of each event
 (cti_converge = 0.1)             The convergence criterion for each CTI-adjusted pixel in adu
       (tstart = TSTART)          header key containing start/default time value
        (tstop = TSTOP)           header key containing time of last event
      (clobber = no)              Overwrite output event file if it already exists?
      (verbose = 0)               level of debug detail (0=none, 5=most)
         (stop = none)            end transformations at [chip,tdet,det,tan,sky,none]
     (instrume = acis)            axaf instrument- used for instrument parameter file
    (rand_seed = 1)               random seed (for pixlib), 0 = use time dependent seed
     (rand_pha = yes)             Randomize the pha value used in gain calculations
(rand_pix_size = 0.5)             pixel randomization width (-size..+size) 0=no randomization
      (stdlev1 = {d:time,s:ccd_id,s:node_id,i:expno,s:chip,s:tdet,f:det,f:sky,s:phas,l:pha,l:pha_ro,f:energy,
l:pi,s:fltgrade,s:grade,x:status}) TE faint modes event definition string
      (grdlev1 = {d:time,s:ccd_id,s:node_id,i:expno,s:chip,s:tdet,f:det,f:sky,l:pha,l:pha_ro,s:corn_pha,f:energy,
l:pi,s:fltgrade,s:grade,x:status}) TE graded event format definition string
       (cclev1 = {d:time,s:ccd_id,s:node_id,i:expno,s:chip,s:tdet,f:det,f:sky,f:sky_1d,s:phas,l:pha,l:pha_ro,
f:energy,l:pi,s:fltgrade,s:grade,x:status}) CC faint event format definition string
    (ccgrdlev1 = {d:time,s:ccd_id,s:node_id,i:expno,s:chip,s:tdet,f:det,f:sky,f:sky_1d,l:pha,l:pha_ro,s:corn_pha,
f:energy,l:pi,s:fltgrade,s:grade,x:status}) cc graded event format definition string
         (mode = ql)