Spatial Characteristics of the HRC-I Quantum Efficiency

The HRC-I underwent flat field testing at the SAO MCP lab after XRCF testing. The data obtained has been analyzed by Charlie Wilton and Mike Juda, Their results can be found on Charlie's web page. They have shown that any deviations in the spatial characteristics of the efficiency are linear to first order. It is therefore appropriate to use the boxcar smoothed image for our analysis. The 128x128 fits image can be downloaded here (shift-clicking on the link will download the file). The surface plot is shown below.

Analysis

To compare the offaxis data to the spatial model, we first must renormalize the model to the one dimensional quantum efficiency curve discussed in our on-axis analysis, at each energy of interest. Then, at each energy of interest, we perform a coordinate transformation on the image centroid to determine its location in (u,v) space. The coordinate transformation is given as:

where (Z,Y) are given as (Z_pixel,Y_pixel) in block 128 coordinates. The rotation is a result of the (u,v) coordinates running along the edge of detector, while the (Z,Y) coordinates are along the long axes of the detector. This also results in a linear transformation of the Y axis by the 90.5 block 128 pixels.

For each energy, we simply compare the model efficiency versus the calculated efficiency from the XRCF measurements. We are only interested in the residuals (i.e. _xrcf - _model) for each position. Also note that in some cases, the residuals may be quite large. This is due to the fact that we are comparing our XRCF results to the flight model. This lends further evidence to the fact that the spatial characteristics of the detector qe have changed since XRCF. No effort has been made to either renormalize the offaxis qe to the flight settings, or compare the offaxis qe to a model of the spatial characteristics of the XRCF qe. This analysis is only to show that the off-center structure of the qe has changed quite dramatically. One may verify this by subtracting the XRCF flat field model from the Flight flat field model.

Results

The results are listed below, in order of energy.

• 0.108 keV
• 0.183 keV
• 0.277 keV
• 0.392 keV
• 0.784 keV
• 0.905 keV
• 1.176 keV
• 1.487 keV
• 1.810 keV
• 3.500 keV
• 4.960 keV
• 7.000 keV

Comments to CxcCal@cfa.harvard.edu

Last modified: 09/25/12

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