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HESSI Nominal Grid Specifications
See also the
HESSI Grid Parameter Table by Gordon Hurford
All linear dimensions are in millimeters.
Collimator Length, L = 1,550 mm
Detector Diameter, D = 71 mm
Collimator # |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
Nominal FWHM Resolution (") |
2.26 |
3.92 |
6.79 |
11.8 |
20.4 |
35.3 |
61.1 |
105.8 |
183.2 |
Nominal
Orientation (°) |
202.57 |
157.57 |
202.58 |
157.54 |
224.94 |
135.01 |
45.04 |
0.08 |
90.0 |
Angular Pitch (") |
4.52 |
7.84 |
13.57 |
23.5 |
40.7 |
70.5 |
122.2 |
211.6 |
366.5 |
Pitch (mm) |
0.034 |
0.059 |
0.102 |
0.177 |
0.306 |
0.530 |
0.918 |
1.590 |
2.754 |
Manufacturer |
Tecomet |
Tecomet |
Tecomet |
Tecomet |
VBC |
VBC |
VBC |
VBC |
VBC |
Slit (mm) |
0.020 |
0.035 |
0.061 |
0.106 |
0.184 |
0.318 |
0.477 |
0.811 |
1.487 |
Slat (mm) |
0.014 |
0.024 |
0.041 |
0.071 |
0.122 |
0.212 |
0.441 |
0.779 |
1.267 |
Maximum fractional transmission |
0.60 |
0.60 |
0.60 |
0.60 |
0.60 |
0.60 |
0.52 |
0.51 |
0.54 |
Total collimator thickness (mm) |
1.2 |
2.1 |
3.6 |
6.2 |
10.7 |
18.6 |
6.2 |
6.2 |
30.0 |
Field of View (°) |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
1.0 |
4.4 |
7.5 |
2.8 |
High-Z Absorber |
Molybdenum |
Tungsten |
Tungsten |
Tungsten |
Tungsten |
Tungsten |
Tungsten |
Tungsten |
Tungsten |
Diameter (mm) |
90 |
90 |
90 |
90 |
90 |
90 |
90 |
90 |
90 |
Outer Diameter (mm) |
110 |
110 |
110 |
110 |
110 |
110 |
110 |
110 |
110 |
Rim width (mm) |
10 |
10 |
10 |
10 |
10 |
10 |
10 |
10 |
10 |
Rim Material |
Molybdenum |
Tungsten |
Tungsten |
Tungsten |
Aluminum |
Aluminum |
Aluminum |
Aluminum |
Aluminum |
Rim height |
1.2 |
2.1 |
3.6 |
6.2 |
20.7 |
28.6 |
16.2 |
16.2 |
40.0 |
Shape |
Round |
Round |
Round |
Round |
Square |
Square |
Square |
Square |
Square |
Mass (g) |
136 |
240 |
394 |
679 |
1006 |
1637 |
708 |
723 |
2700 |
Collimator # |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
Grid Imperfection (mm) |
0.0015 |
0.0025 |
0.004 |
0.005 |
0.006 |
0.008 |
0.012 |
0.017 |
0.025 |
Rel.Mod.Eff. (grids) |
0.922 |
0.928 |
0.938 |
0.968 |
0.985 |
0.991 |
0.993 |
0.995 |
0.997 |
Grid Matching {(1+m):1} |
0.005% |
0.010% |
0.020% |
0.025% |
0.030% |
0.045% |
0.070% |
0.10% |
0.15% |
Rel.Mod.Eff. (matching) |
0.987 |
0.982 |
0.976 |
0.988 |
0.994 |
0.996 |
0.996 |
0.998 |
0.998 |
Relative Twist (arcmin) |
0.333 |
0.5 |
0.6 |
1 |
1.6 |
2.5 |
4 |
6 |
10 |
Rel.Mod.Eff. (twist) |
0.949 |
0.962 |
0.982 |
0.983 |
0.986 |
0.988 |
0.990 |
0.993 |
0.993 |
RMS Rel.Aspect Error(arcsec) |
0.426 |
0.426 |
0.426 |
0.426 |
0.426 |
0.426 |
0.426 |
0.426 |
0.426 |
Rel.Mod.Eff. (aspect) |
0.823 |
0.941 |
0.980 |
0.993 |
0.998 |
0.999 |
1.000 |
1.000 |
1.000 |
Collimator # |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
Camber (mm) |
0.001 |
0.002 |
0.003 |
0.003 |
0.004 |
0.007 |
0.01 |
0.01 |
0.02 |
Camber Effect |
0.0147 |
0.0170 |
0.0147 |
0.0085 |
0.0065 |
0.0066 |
0.0054 |
0.0031 |
0.0036 |
Venetian Blinding (mm) |
0.002 |
0.003 |
0.007 |
0.01 |
0.015 |
0.02 |
0.02 |
0.02 |
0.04 |
Venetian Effect |
0.0588 |
0.0509 |
0.0686 |
0.0566 |
0.0490 |
0.0377 |
0.0218 |
0.0126 |
0.0145 |
Slit Width (mm) |
0.0015 |
0.004 |
0.007 |
0.01 |
0.015 |
0.02 |
0.02 |
0.02 |
0.04 |
Slit Width Effect |
0.0441 |
0.0679 |
0.0686 |
0.0566 |
0.0490 |
0.0377 |
0.0218 |
0.0126 |
0.0145 |
Tilt (arcmin) |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
6 |
Tilt Effect |
0.0616 |
0.0623 |
0.0616 |
0.0613 |
0.0611 |
0.0613 |
0.0118 |
0.0068 |
0.0190 |
Source Location (arcmin) |
8.5 |
8.5 |
8.5 |
8.5 |
8.5 |
8.5 |
8.5 |
8.5 |
8.5 |
Source Location Effect |
0.0873 |
0.0882 |
0.0873 |
0.0868 |
0.0865 |
0.0868 |
0.0167 |
0.0096 |
0.0269 |
Pointing Error (arcmin) |
4.00 |
4.00 |
4.00 |
4.00 |
4.00 |
4.00 |
4.00 |
4.00 |
4.00 |
Pointing Error Effect |
0.0411 |
0.0415 |
0.0411 |
0.0408 |
0.0407 |
0.0408 |
0.0079 |
0.0045 |
0.0127 |
Collimator # |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
RMS Change in Transmission |
0.14 |
0.14 |
0.15 |
0.14 |
0.13 |
0.13 |
0.04 |
0.02 |
0.04 |
Nominal Transmission |
0.6 |
0.6 |
0.6 |
0.6 |
0.6 |
0.6 |
0.52 |
0.51 |
0.54 |
Resulting Transmission |
0.46 |
0.46 |
0.45 |
0.46 |
0.47 |
0.47 |
0.48 |
0.49 |
0.50 |
Waveform Factor (Fw) |
0.987 |
0.981 |
0.975 |
0.985 |
0.989 |
0.993 |
0.997 |
0.999 |
1.000 |
Rel.Mod.Eff. (grids) |
0.922 |
0.928 |
0.938 |
0.968 |
0.985 |
0.991 |
0.993 |
0.995 |
0.997 |
Rel.Mod.Eff. (matching) |
0.987 |
0.982 |
0.976 |
0.988 |
0.994 |
0.996 |
0.996 |
0.998 |
0.998 |
Rel.Mod.Eff. (twist) |
0.949 |
0.962 |
0.982 |
0.983 |
0.986 |
0.988 |
0.990 |
0.993 |
0.993 |
Rel.Mod.Eff. (aspect) |
0.823 |
0.941 |
0.980 |
0.993 |
0.998 |
0.999 |
1.000 |
1.000 |
1.000 |
Waveform Factor (Fw) |
0.987 |
0.981 |
0.975 |
0.985 |
0.989 |
0.993 |
0.997 |
0.999 |
1.000 |
MODULATION EFFICIENCY |
70.1% |
80.9% |
85.9% |
91.9% |
95.2% |
96.8% |
97.6% |
98.4% |
98.8% |
FWHM Resolution (") |
2.26 |
3.92 |
6.79 |
11.76 |
20.36 |
35.27 |
61.08 |
105.80 |
183.24 |
Collimator # |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
Last Updated by: Merrick Berg, October 8th 1999
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