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LEMMS 180 End Design Criteria (as agreed by Engineering Team Meeting)
(Tom Armstrong, 6/1/93)

  1. Optimize for clean coverage of proton spectrum from ~1 to >20 MeV.
  2. Obtain several electron channels, 1 - 10 MeV.
  3. Assume 100 ns time constants (pulse widths).
  4. Accept incidental x-ray responses to obtain (at least) upper limit fluxes.
  5. Specific, refined and optimized design parameters are needed ASAP.
  6. Weight and power constraints may dictate less complexity.
  7. Use ion implant detectors of least variety (in areas and thicknesses) possible (700 m).
  8. Consider reducing D1 from 300 m to 100 m to reduce sensitivity to electrons.
  9. Consider reducing foil thickness from 100 m (A1 equivalent) to lower proton threshold to ~1 MeV.

Radical suggestion: Optimize design of 180 end for 1 --> 30 MeV/nuc.

H, He, O (rate channels).
(High duty cycle but low sampling rate.)
1-2 MeV/nuc.
2-4 MeV/nuc.
4-8 MeV/nuc.
8-16 MeV/nuc.
16-32 MeV/nuc.


Comments on LEMMS 180 End Design for Cassini MIMI
(Tom Armstrong, 6/1/93)

  1. Saturn magnetosphere is very intense in electrons at 1 MeV and very weak in protons--there's a proton minimum 1 - 10 MeV.
  2. ESA0 (200 keV level in 300 m 20 mm2) singles, shielded like D1.  Was ~=104 c/sec at ~3 RS.
    PSB3 ~< 1 c/sec > 16 MeV proton.
    The electron background is a problem!
  3. Observing x-rays R < 10 RS is probably hopeless.  Is the x-ray source sufficiently intense to do it at 20 RS? GCR background is the worry here.
  4. Major unsettled question: Proton spectrum 1 - 20 MeV in inner magnetosphere; how deep is the minimum electron spectrum?  Do the Van Allen resonance features exist? Can MIMI 180 end settle these?
    *Coincidence essential.
    *Fast time constants ~< 30 ns?
    Anomalous components and H, He, O (1 - 20 MeV/nuc) (solar min. 1995, 2006!) should be strong and interesting at Saturn.

Steve J.

TPA (LEMMS high energy end)

Erhard

600 mm2 = A = pd2

d = (600/p)1/2 = 13.82 mm; r = 6.9 mm

300 mm2 = A = pd2; d = 9.77 mm; r = 4.88 mm

PLAN A PLAN B

PLAN C

Reduce conical angle and move detectors back for better definition.

Trial

PIPS - low current, low noise, cleanable, bakeable
Canbera semi-conductor have 700 m, 700 m, 300 m

Logic Protons Electrons
D1D2 x no
D1D2 x no
D1D2D3 no x
D1D2D3 x no
D1D2D3 x x?
D2D3 x x?
D2D3C x no?

Assume 10 minutes = 600 sec; 10 counts = 10/600 = 1/60 c/sec; ~10-2 c/sec.

1-10 MeV protons, J~10-1 (cm2 sec sr MeV)-1 * 10 MeV, J~1 (cm2 sec sr)

dW=dfd (cos f)

W=2p (1 - cos 22.5) = 0.39 ~0.4 sr.

G = AW = 6 0.4 = 2.4 cm2 sr (Kirsch, June 93)

Jthresh = 10-2 c/sec / 2.4 cm2 sr = 0.4 x 10-2 cm2 sr.

This could yield about a factor of 100 increased knowledge of proton flux.

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Updated 6/10/08, T. Hunt-Ward
tizby@ftecs.com