As described in
Instrumentation and in
Stone et. al. (1977)
each of the Voyager space craft has four
low-energy telescopes (LETs); two double-ended high-energy telescopes (HETs);
and an electron telescope (TET). The telescopes are oriented at different viewing angles
to provide information on energetic particle streaming patterns.
The LET and HET A stopping analyses generally use the dE/dx-E
technique outlined for LET in
Cook (1981) and Cook et.al. (1984)
to measure the kinetic energy and the nuclear charge Z of individual incident nuclei.
Each HET and LET are composed of a stack
of cylindrical, solid-state detectors, the first two of
which are thinner than the subsequent detectors and spaced
apart from each other in order to establish
a field of view.
Three energy losses are recorded for each incident
particle, one each from the first two
detectors and the third represents the sum of the energy lost
in the remaining detectors (one in the case of LET),
except for the last detector,
which is used in anti-coincidence to identify
and eliminate penetrating
These three energy losses allow for two semi-independent determinations
of the nuclear Z of the particle to be determined, provided the particle
penetrates the first two detectors.
A consistency criterion is applied to these two determinations
of Z to eliminate background events, and the average
of the two Z determinations gives the estimated Z of the particle,
which is generally not an integer.
Using a model of the telescope, including
the thickness of any window and/or thermal blanket
material covering the entrance aperture and any
inactive thickness of the detectors, incident
energy per nucleon bins are mapped
to energy loss bins in the active thicknesses of the detectors.
HET penetating H and He consists of particles that trigger
detectors B1, B2, and C1.
Three pulse heights are returned for each event
in the form of channel numbers, which are approximately linearly related
to the energy losses in the detectors.
These pulse heights are from B1, C1, and C4+C3+C2 (C432).
For each C432 channel applicable to the species (proton or helium nucleus),
a response table contains
limits of B1 channels, limits of C1 channels, and the highest incident
energy that triggers this C432 channel.
If the B1 and C1 pulse heights of an event fall within the B1 and C1 limits,
respectively, for the C432 channel of a certain element, then this event is
identified as belonging to that element, and its incident energy lies
between the incident energy corresponding to the next lower C432 channel
and that corresponding to C432 of the event.
For the response tables the applicable range of incident energies, energy losses along a mean
trajectory through the telescope are computed using a range-energy relation.
From these energy losses, mean energy losses in B1 and C1 for C432 energy
losses corresponding to the C432 channel boundaries are located.
Representative samples of flight data are examined to estimate the spread
of B1 and C1 pulse heights about the mean values.
These estimates are used
to compute the limits on B1 and C1 for each C432 channel for each element.
The effect of nuclear interactions is accounted for in an approximate way.
First, for protons it is assumed that the effect of interactions is
For He, it is assumed there is an 11% reduction in He intensities
due to nuclear interactions and that correction
is accounted for by using different geometry factors
for H as compared to He.