NAME

phaz -- Perform a pulse height distribution analysis.

USAGE

phaz input eefile intphd difphd fitphd table

DESCRIPTION

This task does a pulse height analysis (PHA) of an input Goddard High Resolution Spectrograph (GHRS) PHA observation. The differential pulse height distribution for each diode is computed and fitted by a Gaussian distribution with a linear baseline. A threshold is computed for each diode using the center of the fitted Gaussian (CENT). If the center is at CENT, then the thresholds are set as follows:

	CENT*percent		main diode array
	CENT*percent+corner	corner diodes
	CENT*percent+focus	focus diodes
	ave*pcrad		radiation diodes

where percent, corner, focus, and pcrad are input parameters, and ave is the average of the thresholds for the main diode array.

Four output files are produced by phaz. Three of these are images containing the integral, differential, and fitted differential pulse height distributions. The names of these images are specified by the intphd, difphd, and fitphd parameters, respectively. The fourth file contains the results of the threshold analysis and is specified by the table parameter; this table contains results of the Gaussian distribution for each diode.

PARAMETERS

input [file name template]

Names of files containing the input PHA observation raw data. This data must be sorted in ascending threshold order. A PHA observation will normally have its data in separate groups of a single input file.

eefile [file name template]

Names of the extracted engineering trailer files corresponding to each file or group specified by input. This file contains the data for the 12 special diodes.

intphd = "intphd" [file name]

Name of the first output image, which will contain the integral pulse height distribution. This distribution will be a two-dimensional array of size (number of thresholds observed) x 512. Each row i of the image contains the integral pulse height distribution for the corresponding diode number i. For example, row 50 will contain the integral pulse height distribution for diode number 50.

difphd = "difphd" [file name]

Name of the second output image, which will contain the differential pulse height distribution. This image takes the same form as the image created for intphd.

fitphd = "fitphd" [file name]

Name of the third output image, which will contain the fitted differential pulse height distribution. This image takes the same form as that of intphd and difphd.

table = "phaz" [file name]

Name of the output table that will contain results of the threshold analysis. This table has 512 rows (one per diode) and the following columns:

     'DIODE'   - The diode number from 1 to 512 (integer).
     'AMP'     - The amplifier number as found in the 'chfile' table 
                 (integer).
     'CHANNEL' - Channel number (taken from the input channel
		 number file 'chfile') (integer).
     'CENTER'  - Center of the fitted Gaussian distribution
		 (i.e., the threshold) (double).
     'PEAK'    - Peak value of the fitted Gaussian (double).
     'SIGMA'   - Sigma of the fitted Gaussian (in threshold 
		 units) (double).
     'A0'      - Constant term of the linear baseline (double).
     'A1'      - Slope of the linear baseline (double).
     'FWHM'    - Full width-half-max of the fitted Gaussian
		 distribution (double).
     'THRESH'  - Computed threshold (double).
     'COUNTS'  - The count rate in the integrated PHA data at the 
                 choosen threshold (double).

(t= 30.0) [real, min=1.0, max=200.0]

Initial threshold level in input (i.e., the threshold level for the first group of the image).

(delt = 1.0) [real, min=1.0, max=200.0]

Step size for incrementing the threshold levels in input.

(percent = 50.0) [real]

Percentage of the center of the Gaussian distribution at which to set the threshold level.

(corner = 5.0) [real]

Threshold offset to be applied to corner diodes.

(focus = 0.0) [real]

Threshold offset to be applied to focus diodes.

(pcrad = 120.0) [real]

Percentage of the average threshold that is to be used as the threshold for radiation diodes.

(center = 80.0) [real, min=0.0, max=200.0]

Initial guess of the center of the Gaussian peaks used by the least squares fit routine.

(sigma = 5.0) [real, min=1.0, max=50.0]

Initial guess of Gaussian peaks.

(niter = 10) [integer, min=1, max=100]

Number of iterations of the least squares fit routine to perform.

(chfile = "hrs$templates/amp2diode.txt") [file name]

Name of the table containing amp and channel numbers for each diode. This information is copied to the output threshold file table, allowing the table to be sorted by amp and channel number.

EXAMPLES

1. Perform the pulse height analysis of the the images phadata and phaee using an initial threshold level of 20 and a step size of 2. The results will be placed in the output table ttab.

cl> phaz.t0 = 20
cl> phaz.delt = 2
cl> phaz phadata.hhh[*] phaee.hhh[*] intphd difphd fitphd ttab

BUGS

REFERENCES

Author: Jonathan Eisenhamer

HELP

For assistance using this or any other tasks, please contact help@stsci.edu or call the help desk at 410-338-1082.

SEE ALSO

pha_all, pha_center, pha_diode, pha_rms, pha_sig2rms, pha_summary, pha_text