EPHIN (The E lectron P roton H elium IN strument)

Here is a collection of various EPHIN information, gathered from various documentation, e-mails, and web sites.

EPHIN Detectors

The EPHIN uses a stack of silicon detectors operating in multi-dE/dx versus E mode to determine particle species. Detectors A and B are segmented passivated ion-implanted silicon (PIPS) detectors. Detectors C, D, and E are lithium-drifted silicon detectors (Si(Li)) and stop electrons up to 10 MeV and protons or helium nuclei up to 53 MeV/nucleon. Detector F is an ion-implanted silicon detector that is used to determine whether a particle was stopped or is penetrating. This stack is encircled by detector G, a fast scintillator read-out by a photo-tube, which is used in anti-coincidence.
schematic of the EPHIN sensor
Chandra EPHIN sensor schematic (adapted from SOHO version at http://www.ieap.uni-kiel.de/et/ag-heber/costep/images/figures/ephin_sensor_fig1.gif). The Chandra version has a thicker aluminized Kapton foil (76 µm) than the SOHO version

EPHIN particle channels are defined by requiring coincidences in two or more of the detectors; all channels require a signal in both the A and B detectors. The segmentation of the A and B detectors allows for the reduction of the area solid-angle product by switching off the ring segments.

Coincidence Channel Definitions - "strike-through" = NOT on coincidence condition
Detector thresholds: A0 = 30 keV, A1 = 270 keV, A2 = 970 keV, A3 = 2.1 MeV, A4 = 5.3 MeV
B0 = 60 keV, C0 = 370 keV, D0 = 580 keV, E0 = 580 keV, F0 = 150 keV, G0 = 100 keV
TypeName Energy Range Multiplicity Priority Buffer Depth Coincidence Condition Geometric Factor
Large [Small] (cm2 sr)
ElectronE150 0.25 - 0.70 MeV 1 4 A0 A1 B0 C0 D0 E0 F0 G0 0.25 [0.01]
E300 0.67 - 3.0 MeV 1 4 A0 A1 B0 C0 D0 E0 F0 G0 1.78 [0.14]
E1300 2.64 - 6.18 MeV 1 4 A0 A1 B0 C0 D0 E0 F0 G0 2.01 [0.12]
E3000 4.80 - 10.4 MeV 1 4 A0 A1 B0 C0 D0 E0 F0 G0 1.58 [0.09]
ProtonP4 5.0 - 8.3 MeV 3 4 A1 A4 B0 C0 D0 E0 F0 G0 5.14 [0.18]
P8 8.3 - 25.0 MeV 3 4 A1 A3 B0 C0 D0 E0 F0 G0 5.14 [0.18]
P25 25.0 - 41.0 MeV 3 4 A1 A2 B0 C0 D0 E0 F0 G0 4.77 [0.18]
P41 41.0 - 53.0 MeV 3 4 A1 A2 B0 C0 D0 E0 F0 G0 3.80 [0.18]
HeliumH4 5.0 - 8.3 MeV/N 4 40 A4 B0 C0 D0 E0 F0 G0 5.14 [0.18]
H8 8.3 - 25.0 MeV/N 4 16 A3 B0 C0 D0 E0 F0 G0 5.14 [0.18]
H25 25.0 - 41.0 MeV/N 4 4 A2 B0 C0 D0 E0 F0 G0 4.77 [0.18]
H41 41.0 - 53.0 MeV/N 4 4 A2 B0 C0 D0 E0 F0 G0 3.80 [0.18]
IntegralINT e- > 8.7 MeV 1 0 A0 B0 C0 D0 E0 F0 G0 6.85 [0.36]
p+ > 53.0 MeV
He+ > 53.0 MeV/N

Calibrations

Energy resolution FWHM using electrons (133Ba, 207Bi)
and alphas (241Am)
Detector Type Thickness (µm) Resolution (keV) Rad. Source
A PIPS 150 13 133Ba
B PIPS 300 26 241Am
C Si(Li) 3000 43 207Bi
D Si(Li) 5000 43 207Bi
E Si(Li) 5000 41 207Bi

Dead layer measurement in Si(Li) detectors using 241Am 5.485 MeV alphas incident from the rear side
Detector Dead layerspec (µm) meas. alpha E (MeV) dead layer E loss (MeV) Dead layermeas (µm)
C 40 1.82 3.65 22
D 40 0.60 4.87 26
E 40 2.40 3.07 19

Energy resolution measured using µ-mesons
Detector Threshold (keV) Mean (keV) RMS (keV) Peak (keV) FWHM (keV)
A 30 52 23 41 21
B 60 106 43 86 37
C 359 1150 326 980 310
D 581 1890 485 1620 490
E 582 1150 377 970 350

Links

Last modified: Mon Feb 4 16:00:03 EST 2002

Dr. Michael Juda
Harvard-Smithsonian Center for Astrophysics
60 Garden Street, Mail Stop 70
Cambridge, MA 02138, USA
Ph.: (617) 495-7062
Fax: (617) 495-7356
E-mail: mjuda@cfa.harvard.edu