Science Requirements Document
Section 2 of 4
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The LET-B is a Voyager CRS spare LET with upgrading of the collimator. The cross section of the LET B telescope is illustrated in Figure 1. All detectors are silicon surface barrier devices. Signals from detectors LB1, LB2 and LB3 are analyzed, while LB4 is an anti-coincidence device. The geometry of LB1 and LB2 limits the viewing cone to 50° full angle. Detector areas and thickness are also given in Figure 1.
| LET B Detector Positions and Sizes | |||||||
|---|---|---|---|---|---|---|---|
| Item | height (cm) |
radius (cm) |
thickness (µm) |
pathlength (L1L2) |
material | thickness (µm equiv Si) |
area (cm2) |
| WA | 3.55 | 2.60 | 25 | 25.6 | Kapton | 20.0 | 21.237 |
| LB1 | 0 | 0.9456 | 32.06 | 32.84 | Si | 2.8092 | |
| LB2 | -4.08 | 0.9458 | 29.607 | 30.34 | Si | 2.8104 | |
| LB3 | -4.3 | 1.144 | 421.24 | 432.21 | Si | 4.1151 | |
| LB4 | -4.47 | 1.137 | 439.92 | 451.09 | Si | 450 | 4.0621 |
Figure 1
The LET-E is modified from the Voyager LET by substitution of two thick surface barrier detector (LE4 and LE5) for the existing L4 and by much heavier collimation and shielding.
The cross section of the telescope is shown in Figure 2. Detectors LE1, LE2 and LE3 are surface barrier devices; LE4 and LE5 are lithium drifted. Signals from all detectors are analyzed. LE1 and LE2 define a 50° viewing cone, while LE2 and LE5 define a 92° viewing cone in the wide angle mode. Detector areas and thicknesses are also given in Figure 2.
| LET E Detector Positions and Sizes | |||||||
|---|---|---|---|---|---|---|---|
| Item | height (cm) |
radius (cm) |
thickness (µm) |
pathlength (L1L2) |
material | thickness (µm equiv Si) |
area (cm2) |
| WA | 7.00 | 6.37 | 76 | 77.9 | Kapton | 60.0 | 127.48 |
| WB | 5.54 | 5.30 | 256.54 | 262.95 | Al | 289.5 | 88.247 |
| LE1 | 4.08 | 0.9489 | 30.41 | 31.16 | Si | 2.8288 | |
| LE2 | 0 | 0.9491 | 33.41 | 34.24 | Si | 2.8302 | |
| LE3 | -0.22 | 1.138 | 463.12 | 474.95 | Si | 4.0678 | |
| LE4 | -0.65 | 2.19 | 2000 | 2050 | Si | 15. | |
| dead | 53.2 | 54.5 | Si | ||||
| LE5 | -1.08 | 2.19 | 2000 | 2050 | Si | 15. | |
| dead | 54.9 | 56.3 | Si | ||||
Figure 2
| Table 2 -- Geometrical Factors | ||
|---|---|---|
| Items | Geom | half-angle |
| LB1,W | 3.02 | 45° |
| LB1,LB2 | 0.4293 | 24.87° |
| LE1,WA | 7.34 | 68° |
| LE2,WA | 4.006 | 46.27° |
| LE1,LE2 | 0.435 | 24.95° |
| LE2,LE3,LE4,WA | 4.006 | 46.27° |
| LE2,LE3,LE4,LE5,WA | 4.006 | 46.27° |