Pulse Height Distributions

Below are the current calibration products for the HRC PHA.

The most recent products are:

v1.1 for the HRC-I (11/08/99 by A. Kenter and R. Kraft) - same as CalDB version
v1.1 for the HRC-S (11/08/99 by R. Kraft) - same as CalDB version

HRC-I

0.183 keV v1.1: Plot Data v1:Plot Data	0.277 keV v1.1: Plot Data v1:Plot Data	0.525 keV v1.1: Plot Data v1:Plot Data
0.850 keV v1.1: Plot Data v1:Plot Data	Gaussian Fits v1.1: Plot Data v1:Plot Data	1.487 keV v1.1: Plot Data v1:Plot Data
2.984 keV v1.1: Plot Data v1:Plot Data	4.511 keV v1.1: Plot Data v1:Plot Data	6.404 keV v1.1: Plot Data v1:Plot Data

The intrinsic energy resolution of both of the HRC detectors is generally limited. As the surrounding plots indicate the variations in the PHA distributions to different monochromatic sources are small. The distributions have been fit with single (v1) and double gaussians (v1.1; which has also been normalized). The centroids of the fits are included on each plot for direct comparison with each distribution. Colors have been used to emphasize the differences between energies.

Below 1.485 keV the instruments are the most sensitive to changes in energy, showing steeper declines in all cases. This is further emphasized with the Double Gaussian fits. Not evident from these plots are how the relative normalizations change with energy for the Double Gaussian fits.

On orbit with non-monochromatic sources the situation is in some respect simpler. The plot below shows the variation in the mean of the PHA distribution for the HRC-I(no gaussian fit) as various sources were observed during its the first observation phase. The bulk of the variation is due to location of the source on the detector, as can be seen from the LMC X1 data which was collected at three different times and positions. The high PHA mean data was collected at the center while the low means came in the corners

Since these observations were made the HRC-I has had its high voltage adjusted downward thus lowering its overall gain such that the center of the plate is at more desirable levels.

HRC-S

0.183 keV v1.1: Plot Data v1:Plot Data	0.277 keV v1.1: Plot Data v1:Plot Data	0.525 keV v1.1: Plot Data v1:Plot Data
0.850 keV v1.1: Plot Data v1:Plot Data	Gaussian Fits v1.1: Plot Data v1:Plot Data	1.487 keV v1.1: Plot Data v1:Plot Data
2.984 keV v1: Plot Data	4.511 keV v1.1: Plot Data v1:Plot Data	6.404 keV v1.1: Plot Data v1:Plot Data

Contact CXC Calibration (cxccal@cfa.harvard.edu) for further information

Last modified: 09/27/12

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