The HETs and LETs are redundant and are designed to complement each other and to cover a broad range in energy, intensity, and charge spectra. Click the Space craft image to go to instrument webpage at the Jet Propulsion Labortory.
For particles which come to rest within this stack (4 - 70 MeV/ nucleon) three measurements are made: energy loss (dE/dx), total energy, and range. For particles which penetrate completely through the stack of solid state detectors three separate dE/dx measurements are made. This multiparameter analysis reduces the back-ground level of spurious events to a negligible level. Charge resolution for penetrating particles is possible up to about 200 MeV/nucleon. It is estimated that the absolute uncertainty in the helium flux is about 7% at 400 MeV and about 5% at energies below 200 MeV.
Element area thickness A1 --------- 8 cm**2 0.15 mm A2 --------- 8 cm**2 0.15 mm C1 xxxxxxxxx 9.5 cm**2 3 mm G1 | C2a xxxxxxxxx 9.5 cm**2 6 mm | C2b xxxxxxxxx | | C3a xxxxxxxxx 9.5 cm**2 6 mm | C3b xxxxxxxxx | | C4a xxxxxxxxx 9.5 cm**2 6 mm | C4b xxxxxxxxx _______ B2 // \\ 8 cm**2 2 mm curved B1 \\_______// 8 cm**2 2 mm curvedThe HET geometry factor varies from about .74 - 1.7 over the energy range covered by the telescope depending on whether the event is A Stopping, B Stopping, or Penetrating.
element mnemonic area thickness ***************** 3uM AL collimator light baffle L1 --------- 2.8 cm**2 surface barrier 35 uM L2 --------- 2.8 cm**2 surface barrier 35 uM L3 xxxxxxxxx 4.5 cm**2 surface barrier 450 uM L4 xxxxxxxxx 4.5 cm**2 surface barrier 450 uMThe LET geometry factor is nominally 0.440 cm2-steradian.
LET Thickness and Delta Z Corrections
D1 xxxxxxxxx D2 xxxxxxxxx .25 mm tungsten absorber D3 xxxxxxxxx .56 mm tungsten absorber D4 xxxxxxxxx 1.12 mm tungsten absorber D5 xxxxxxxxx 1.60 mm tungsten absorber D6 xxxxxxxxx 2.03 mm tungsten absorber D7 xxxxxxxxx 2.34 mm tungsten absorber D8 xxxxxxxxx Di detectors= 4.5 cm**2 Lithium drifted 3mm tungsten absorbers are 18.0 g/cm**3 where cm = centimeters mm = millimeter where uM = micrometer
TET geometry factor varies from about .66 - 3.12 depending upon depth of penetration into the Di stack.
D.E.Stillwell, W.D.Davis, R.M.Joyce, F.B.McDonald, J.H.Trainor, W.E.Althouse, A.C.Cummings, T.L.Garrard, E.C.Stone, and R.E.Vogt, "The Voyager Cosmic Ray Instrument", IEEE Transactions on Nuclear Science, Vol. 26, 1979, pp. 513
E. C. Stone, R. E. vogt, F. B. McDonald, B. J. Teegarden, J. H. Trainor, J. R. Jokipii, and W. R. Webber, "Cosmic Ray Investigation for the Voyager Missions: Energetic Particle Studies in the Outer heliosphere - and Beyond", Space Science Reviews, 21, 355-376, 1977.