Low Energy Ion and Electron Instrument (LION)
LION Sensor
LION is a stack of semiconductor detectors to measure energetic particles. The
instrument consists of two sensor heads, each containing a double telescope,
which together provide the capability to measure particle spectra in the range
44 keV to 6 MeV for protons and 44 keV to 300 keV for electrons. A channel for
Z>1 particles, mainly alphas in the range 7-26 MeV, is also provided. Count
rates are accumulated with 15 s time resolution. One of the two LION sensors
consists of three ion-implanted silicon detectors arranged in a '2 in 1'
telescope configuration. Two square detectors form the dual front elements,
making back-to-back contact to the rectangular rear element. This rear element is
operated in anticoincidence to reduce background from penetrating particles. The
two square detectors view the same rectangular entrance aperture, providing a
total field of view of 60° x 40° and a total geometric factor 0.32 cm2
sr. Each of them, in combination with the common rectangular detector, forms a
distinct particle telescope, providing extended angular coverage for a minimum
weight penalty. The LION 2 sensor head employs a 'broom magnet', utilizing rare
earth NdFeB material to sweep electrons of energies up to at least 300 keV away
from both of the square detectors. In order to eliminate stray magnetic fields,
the magnet has a closed soft iron yoke. Higher energy electrons penetrate the
sqaure detector and trigger the rectangular one, thereby enabling their
separation from higher energy ions. The LION 1 sensor which is identical, except
that no broom magnet is included, measures the sum of electrons and protons,
thereby enabling the determination by subtraction of electron rates in the range
below 300 keV.
Both LION sensor heads and their associated electronics are packed into one
housing, having envelope dimensions 18.2 x 15.0 x 13.3 cm3. A sunshade
protects the sensor apertures from direct illumination and from stray light. The
entrance aperture points in the direction of the nominal interplanetary magnetic
field at 1 AU, 45° west of the spacecraft-sun line. The instrument has a total
power requirement of 0.9 W; a mass of 2.2 kg and requires a telemetry rate of 40
bits per second.
Taken from "THE SOHO MISSION" by Bernhard Fleck, Vicente Domingo and Arthur I.
Poland; Kluwer Academic Publishers
Download the Complete Instrument Description (ZIP-Format, 1.8 MB, taken from "The SOHO Mission")