HESSI SHUTTER PARAMETERS
The purpose of this document is to summarize the as-built parameters of the HESSI shutters.
There are 'thin' and 'thick' shutters associated with each subcollimator. Each shutter was fabricated from an aluminum disk, which was machined by Tecomet to form 3 concentric circular subareas of different thicknesses. The shutter parameters are slightly different for each subcollimator due both to fabrication tolerances and due to different design parameters. (The differences were required in order to minimize any spatial coherence between the shutter geometry and the grids.) Nevertheless the overall goal was to have roughly similar transmissions for all subcollimators.
The primary objective of the shutter calibration was to determine the surface density of each subarea of each shutter. The calibration was based on 5 types of data.
Analysis of the calibration data yielded the individual shutter parameters (diameters and surface densities) shown in the table below. Also tabulated is the diameter of the graded-Z guard ring which defines the effective diameter of the front segment of each detector.
For each individual shutter, the diameters were converted to the fraction of available area corresponding to each subarea (3 per shutter). When both shutters are IN, there are effectively 5 subareas, whose fractional area and combined surface density was also calculated. The fractional area and surface density for each subarea, attenuator setting and subcollimator are tabulated in the boxed area in the 'Attenuator Parameter Table'. The boxed area was copied to a text file ( APT_yyyymmdd.txt where yyyymmdd is the version date) and is included in \ssw\hessi\dbase\spec_resp.
During data analysis, the latest version of the attenuator parameter table is used by the function, hsi_shutter_transmission, to calculate the attenuator transmission as a function of energy, subcollimator and attenuator state. This calculation uses log-log interpolation of the NIST tables for aluminum which are read by the function, read_mat_xcom.
Plots of shutter transmission as a function of energy are shown in Figures 1 and 2 for a typical subcollimator. (These plots are normalized so that both attenuators OUT would give 1 and so do not include the effect of blankets, etc. The dotted, dashed and dot-dashed lines correspond to THIN, THICK and THIN+THICK cases respectively.)
Corresponding plots of the effective radius (relative to the graded-Z ring) of the transmitting area is shown in Figure 3, which illustrates that at low energies, all the transmission is through the innermost area.
There are two approaches by which in-flight data can be used to confirm the shutter transmission. First, the continuity of semi-calibrated light curves when a shutter inserted or removed can be checked as a function of energy. Second, ratios of semi-calibrated spectra among detectors can be compared with and without attenuators, again as a function of energy. If significant anomalies are found, the in-flight data can be combined with prelaunch calibration data to improve the attenuator parameter table so that the updated calibration can be applied retroactively to the existing flare database.
HESSI ATTENUATOR
PARAMETER TABLE |
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1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
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Graded-Z
ring diameter |
mm |
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58.5 |
58.5 |
57.5 |
58.5 |
58.5 |
58.5 |
57.5 |
58.5 |
58.5 |
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Shutter
ID |
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A1-1 |
A2 |
A3 |
A4 |
A5-1 |
A6 |
A7-1 |
A8 |
A9-1 |
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Inner
diameter |
mm |
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1.716 |
1.716 |
1.716 |
1.716 |
1.940 |
1.716 |
2.050 |
1.940 |
3.360 |
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Middle
diameter |
mm |
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24.300 |
24.300 |
24.300 |
24.300 |
24.300 |
24.300 |
24.300 |
24.300 |
24.300 |
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Inner
surface density |
g/cm2 |
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0.0133 |
0.0135 |
0.0134 |
0.0127 |
0.0153 |
0.0133 |
0.0162 |
0.0156 |
0.0262 |
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Middle
surface density |
g/cm2 |
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0.177 |
0.179 |
0.178 |
0.178 |
0.154 |
0.179 |
0.153 |
0.151 |
0.166 |
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Outer
surface density |
g/cm2 |
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0.414 |
0.412 |
0.415 |
0.415 |
0.389 |
0.414 |
0.391 |
0.391 |
0.397 |
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Shutter
ID |
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B1-1 |
B2 |
B3 |
B1-3 |
B5 |
B6 |
B7 |
B8 |
B9-1 |
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Inner
diameter |
mm |
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6.743 |
6.743 |
6.743 |
6.743 |
6.743 |
6.743 |
6.743 |
6.743 |
6.15 |
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Middle
diameter |
mm |
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17.1 |
17.1 |
17.1 |
17.1 |
17.1 |
17.1 |
17.1 |
17.1 |
17.1 |
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Inner
surface density |
g/cm2 |
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0.0192 |
0.0191 |
0.0189 |
0.0188 |
0.0188 |
0.0187 |
0.0187 |
0.0185 |
0.0208 |
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Middle
surface density |
g/cm2 |
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0.261 |
0.260 |
0.257 |
0.262 |
0.262 |
0.257 |
0.262 |
0.256 |
0.260 |
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Outer
surface density |
g/cm2 |
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0.112 |
0.112 |
0.110 |
0.114 |
0.114 |
0.107 |
0.115 |
0.109 |
0.114 |
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Conversion
to ssw Attenuator parameter table format |
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LABEL |
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APT1-1 |
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VERSION-DATE |
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DESCRIPTION |
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GH:
Preflight CBE of shutter parameters, from XGCF data, nominal diameters,
25-apr-01 calib analysis, updated ring diam |
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fraction1 |
detector-middleB |
THIN |
0.9146 |
0.9146 |
0.9116 |
0.9146 |
0.9146 |
0.9146 |
0.9116 |
0.9146 |
0.9146 |
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fraction2 |
middleB-innerB |
THIN |
0.0722 |
0.0722 |
0.0747 |
0.0722 |
0.0722 |
0.0722 |
0.0747 |
0.0722 |
0.0744 |
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fraction3 |
innerB |
THIN |
0.01329 |
0.01329 |
0.01375 |
0.01329 |
0.01329 |
0.01329 |
0.01375 |
0.01329 |
0.01105 |
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fraction4 |
0 |
THIN |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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fraction5 |
0 |
THIN |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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Surf.Density1 |
outerB |
THIN |
0.1120 |
0.1119 |
0.1105 |
0.1140 |
0.1138 |
0.1068 |
0.1153 |
0.1088 |
0.1142 |
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Surf.Density2 |
middleB |
THIN |
0.2611 |
0.2596 |
0.2571 |
0.2621 |
0.2617 |
0.2567 |
0.2618 |
0.2564 |
0.2605 |
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Surf.Density3 |
innerB |
THIN |
0.0192 |
0.0191 |
0.0189 |
0.0188 |
0.0188 |
0.0187 |
0.0187 |
0.0185 |
0.0208 |
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Surf.Density4 |
0 |
THIN |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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Surf.Density5 |
0 |
THIN |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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fraction1 |
detector-middleA |
THICK |
0.8275 |
0.8275 |
0.8214 |
0.8275 |
0.8275 |
0.8275 |
0.8214 |
0.8275 |
0.8275 |
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fraction2 |
middleA-innerA |
THICK |
0.1717 |
0.1717 |
0.1777 |
0.1717 |
0.1714 |
0.1717 |
0.1773 |
0.1714 |
0.1692 |
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fraction3 |
innerA |
THICK |
0.000860 |
0.000860 |
0.000891 |
0.000860 |
0.001100 |
0.000860 |
0.001271 |
0.001100 |
0.003299 |
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fraction4 |
0 |
THICK |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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fraction5 |
0 |
THICK |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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Surf.Density1 |
outerA |
THICK |
0.4143 |
0.4125 |
0.4150 |
0.4150 |
0.3894 |
0.4137 |
0.3907 |
0.3908 |
0.3972 |
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Surf.Density2 |
middle
A |
THICK |
0.1770 |
0.1792 |
0.1775 |
0.1778 |
0.1542 |
0.1794 |
0.1534 |
0.1513 |
0.1656 |
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Surf.Density3 |
innerA |
THICK |
0.0133 |
0.0135 |
0.0134 |
0.0127 |
0.0153 |
0.0133 |
0.0162 |
0.0156 |
0.0262 |
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Surf.Density4 |
0 |
THICK |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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Surf.Density5 |
0 |
THICK |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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fraction1 |
detector-middleA |
THICK+THIN |
0.8275 |
0.8275 |
0.8214 |
0.8275 |
0.8275 |
0.8275 |
0.8214 |
0.8275 |
0.8275 |
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fraction2 |
middleA-middleB |
THICK+THIN |
0.0871 |
0.0871 |
0.0902 |
0.0871 |
0.0871 |
0.0871 |
0.0902 |
0.0871 |
0.0871 |
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fraction3 |
middleB-innerB |
THICK+THIN |
0.0722 |
0.0722 |
0.0747 |
0.0722 |
0.0722 |
0.0722 |
0.0747 |
0.0722 |
0.0744 |
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fraction4 |
innerB-innerA |
THICK+THIN |
0.01243 |
0.01243 |
0.01286 |
0.01243 |
0.01219 |
0.01243 |
0.01248 |
0.01219 |
0.00775 |
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fraction5 |
innerA |
THICK+THIN |
0.000860 |
0.000860 |
0.000891 |
0.000860 |
0.001100 |
0.000860 |
0.001271 |
0.001100 |
0.003299 |
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Surf.Density1 |
outerA+outerB |
THICK+THIN |
0.5263 |
0.5244 |
0.5254 |
0.5289 |
0.5032 |
0.5206 |
0.5060 |
0.4995 |
0.5114 |
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Surf.Density2 |
middleA+outerB |
THICK+THIN |
0.2890 |
0.2911 |
0.2880 |
0.2918 |
0.2680 |
0.2862 |
0.2687 |
0.2600 |
0.2798 |
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Surf.Density3 |
middleA+middleB |
THICK+THIN |
0.4381 |
0.4388 |
0.4346 |
0.4400 |
0.4159 |
0.4361 |
0.4151 |
0.4076 |
0.4261 |
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Surf.Density4 |
MiddleA+innerB |
THICK+THIN |
0.1963 |
0.1983 |
0.1964 |
0.1966 |
0.1730 |
0.1981 |
0.1721 |
0.1698 |
0.1863 |
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Surf.Density5 |
innerA+innerB |
THICK+THIN |
0.0326 |
0.0326 |
0.0323 |
0.0315 |
0.0340 |
0.0320 |
0.0350 |
0.0341 |
0.0470 |
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Comments: |
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Graded-Z
ring diameters corrected per DS memo. |
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APT1-1
is the current best estimate preflight version of the attenuator parameter
table. |
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Boxed area should be pasted
into a text file named 'label.txt' which is read by hsi_rd_shutter_parameters. |
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