EPHIN - sensor unit
The EPHIN sensor is a multi-element array of solid state detectors with anticoincidence to measure energy spectra of electrons in the range 250 keV to > 8.7 MeV, and of hydrogen and helium isotopes in the range 4 MeV/n to > 53 MeV/n. The associated signal processing electronics is housed in a separate unit. The units are interconnected by 22 double screened cables. Together, the two units have envelope dimensions of 35.5 x 21.9 x 19.1 cm3. The total mass of EPHIN is 3.55 kg, the total power consumption is 1.85 W and the telemetry rate after onboard data compression is 172 bits per second. The sensor aperture points in the direction of the nominal interplanetary magnetic field at 1 AU, 45° west of the spacecraft Sun line.
Table 1 summarizes the scientific counting rate channels. Separation of particle species is provided by a set of thresholds also indicated in Table 1.
| Type | Name | Energy Range | M (1) | P (2) | Coincidence Condition (3) | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Table 1: EPHIN Coincidence Channels and Coincidence Conditions. (1) Multiplicity, (2) Priority Buffer Depth, (3) Segment index A and B detector not shown Note: (i) 33 coincidence countrates + 17 single detector countrates + 6 calibration/control channels A0n B0n C0 D0 E0 F0 (n=0...5), total of 56 counters and (ii) thresholds: A0n = 30 keV, B0n = 60 keV (n=0...5), A1 = 270 keV, A2 = 970 keV, A3 = 2.1 MeV, A4 = 5.3 MeV, C0 = 370 keV, D0 = 580 keV, E0 = 580 keV, F0 = 150 keV, G0 = 100 keV |
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| Electron | E150 | 0.25 - 0.70 MeV | 1 | 4 | A0 | ¬A1 | B0 | ¬C0 | ¬D0 | ¬E0 | ¬F0 | ¬G0 |
| E300 | 0.67 - 3.00 MeV | 1 | 4 | A0 | ¬A1 | B0 | C0 | ¬D0 | ¬E0 | ¬F0 | ¬G0 | |
| E1300 | 2.64 - 6.18 MeV | 1 | 4 | A0 | ¬A1 | B0 | C0 | D0 | ¬E0 | ¬F0 | ¬G0 | |
| E3000 | 4.80 - 10.4 MeV | 1 | 4 | A0 | ¬A1 | B0 | C0 | D0 | E0 | ¬F0 | ¬G0 | |
| Proton | P4 | 4.3 - 7.8 MeV | 3 | 4 | A1 | ¬A4 | B0 | ¬C0 | ¬D0 | ¬E0 | ¬F0 | ¬G0 |
| P8 | 7.8 - 25.0 MeV | 3 | 4 | A1 | ¬A3 | B0 | C0 | ¬D0 | ¬E0 | ¬F0 | ¬G0 | |
| P25 | 25.0 - 40.9 MeV | 3 | 4 | A1 | ¬A2 | B0 | C0 | D0 | ¬E0 | ¬F0 | ¬G0 | |
| P41 | 40.9 - 53.0 MeV | 3 | 4 | A1 | ¬A2 | B0 | C0 | D0 | E0 | ¬F0 | ¬G0 | |
| Helium | H4 | 4.3 - 7.8 MeV/N | 4 | 40 | A4 | B0 | ¬C0 | ¬D0 | ¬E0 | ¬F0 | ¬G0 | |
| H8 | 7.8 - 25.0 MeV/N | 4 | 16 | A3 | B0 | C0 | ¬D0 | ¬E0 | ¬F0 | ¬G0 | ||
| H25 | 25.0 - 40.9 MeV/N | 4 | 4 | A2 | B0 | C0 | D0 | ¬E0 | ¬F0 | ¬G0 | ||
| H41 | 40.9 - 53.0 MeV/N | 4 | 4 | A2 | B0 | C0 | D0 | E0 | ¬F0 | ¬G0 | ||
| Integral | INT | E > 8.70 MeV | 1 | 0 | A0 | B0 | C0 | D0 | E0 | F0 | ¬G0 | |
| P > 53.0 MeV | ||||||||||||
| H > 53.0 MeV/N | ||||||||||||
EPHIN sensor unit
- Figure 1: Schematic view of the EPHIN sensor
The heart of the EPHIN sensor head consists of a stack of five silicon detectors, surrounded by an anticoincidence shield of plastic scintillator and a sixth silicon detector to distinguish between absorption and penetration mode (see Fig. 1).
Two passivated ion-implanted detectors (A and B) define the 83° full width conical field of view with a geometric factor of 5.1 cm2 sr. Detectors A and B are divided into six segments. This coarse position sensing permits sufficient correction for path length variations (resulting from the large field of view) needed to resolve isotopes of hydrogen and helium. Another important advantage of segmentation is the capability to implement a commandable or self-adaptive geometric factor. On detection of high count rates in the centre segment A0 the logic will disable all but the inner circular segments of both detectors A and B, reducing the effective geometric factor by a factor of 24 to permit measurements of fluxes as high as 106 counts/(cm2 s sr) without significant dead time losses.
The lithium-drifted silicon detectors C, D and E stop electrons up to 10 MeV und hydrogen und helium nuclei up to 53 MeV/N. These large area detectors have thickness variations of less than 10μm and diffused lithium contact dead layers of less than 50μm silicon equivalent. The ion-implanted detector F will allow particles stopping in the telescope to be distinguished from penetrating particles. The fast plastic scintillation detector G, viewed by a 1 inch photomultiplier and used in anticoincidence, helps to reduce background. The whole stack is mounted in an aluminium housing, the aperture being covered by two thin foils. The inner titanium foil of 2 μm thickness ensures light tightness and closes the electrical shielding of the sensor while the outer aluminized kapton foil of 8 μm thickness is necessary for thermal control. The detector specifications are given in Table 2.
| Detector | A | B | C | D, E | F |
|---|---|---|---|---|---|
| Table 2: Detector Specifications | |||||
| Type | ion-implanted | ion-implanted | Lithium-drifted | Lithium-drifted | ion-implanted |
| Thickness/ μm | 150 +/- 10 | 300 +/- 15 | 3000 +/- 10 | 5000 +/- 10 | 700 +/- 15 |
| Active Area/ mm2 | 1130 | 1130 | 1500 | 1500 | 5000 |
| Number of segments | 6 | 6 | 1 | 1 | 1 |
| α-Res. keV FWHM | 36 | 36 | ≤ 150 | ≤ 150 | 80 |
| β-Res. keV FWHM | 12 | 12 | - | - | 70 |
More information about EPHIN
The EPHIN pages are based upon
R. Müller-Mellin et. al.
COSTEP - Comprehensive Suprathermal And Energetic Particle Analyser
Solar Physics 162: 483-504, 1995
