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November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber1
DLR
03 – RAD Sensor Head (RSH) Functional Overview
Robert F. Wimmer-Schweingruber, IEAP/CAU, Kiel, Germany
RAD Packaging Review
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber2
DLR
RAD Level 2 Science Requirements
RAD Science Requirements:
•RAD shall measure energetic charged particles (Z=1-26) with energies up to 100 MeV/nucleon.
•RAD shall measure neutral particles (neutrons and gamma-rays) with energies up to 100 MeV
•RAD shall measure energetic electrons with energies up to 10 MeV.
•RAD shall measure dose and LET spectra on the Martian surface.
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber3
DLR
• RAD shall measure energetic particles with an energy resolution sufficient to distinguish between major particle species (i.e. protons, He), low Z(i.e. p, He, Li ions), medium Z(i.e. C, N, O ions), and high Z (i.e. heavier nuclei up to Fe) particles.
• RAD shall measure energetic particles with time resolution sufficient to obtain time series observations over the course of the MSL baseline mission and to resolve spectra associated with solar particle events when they occur.
RAD Level 2 Science Requirements (cont’d)
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber4
DLR
Charged Particle Interaction with Matter
• Ionization• electron content important• heavy ions deliver more dE/dx
dE/dx ~ Zp
2 /E...
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber5
DLR
Summary of Measurement Requirements
A
CB
F
G
E
D
n
g
ion, electron• Charged particles (Z = 1–26)
up to 100 MeV/nuc
• Neutral particles (n, )
up to 100 MeV/nuc
• Electrons up to 10 MeV
• LET
• Species discrimination
• Time series
• Autonomous operation
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber6
DLR
RAD Sensor Head (RSH)n-Measurement Principle
Thus need transparent high-proton-content material
neutronscattered
recoilprotonneutron Charged proton
is easy to detectby induced scintillation.
E recoil
q90ᄚ0ᄚ
q
log s
log E [MeV]1 10
[barn]
1
105
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber7
DLR
n-Measurement Approach
Neutron Channel:
Conversion of neutrons to detectable protons using 30 g of high proton-content-scintillator (BC432(m))
Neutral particle detection requires efficient anti coincidence (AC)
MIPs energy deposit 2 MeV/g/cm2
→ use 12mm BC432(m)
Need ≥ 99.8 % efficiency,
no crosstalk, light tightness
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber8
DLR
n-Measurement Approach
Don't want high voltage in Martian atmosphere.
→ Read out light signal with PIN diodes.
Use same detectors as for charged-particle telescope.
→ Resolve very
small signal.
→ Need good
CSAs.
background
muon signal
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber9
DLR
g-Measurement Principles
Thus need transparent high-density material
Photo-effectCompton effect
Pair production
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber10
DLR
g-Measurement Implementation
MSL RAD CsI- crystal
CsI is a very efficient gdetector, moreover, 30 mm CsI stops 100 MeV protons and 200 MeV/nuc iron. Signal read out with PIN diodes.
Test diode(non flight)
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber11
DLR
n-g-Measurement Implementation
Keep CsI calorimeter (D) and
n-channel (E) close together and
inside telescopoe FOV for charged
particle measurements.
Stack must be inside efficient AC.
nSeparation of n and gby statistical method similar to a method also applied to SOHO data (Böhm et al., 2006)
gD
E
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber12
DLR
Statistical Separation of n and g-rays by Matrix Inversion
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber13
DLR
Measurement Implementation
Solar particle event measurement
requires maximization of geometric
factor:
FoV
Active Area
Particle discrimination FOV half-angle q60°
Simulations and other considerations:
q = 32.5 deg. Results in acceptable path-length variations.
CsI thickness 28 mm results in 100 MeV/nuc stopping power for most particles.
q
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber14
DLR
RSH SSD Geometry
• Three SSDs allow limited dE/dx
• close gaps in anti-coincidence A
BC
D
EF
B
C
D
F
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber15
DLR
**The RTG will induce a background to the neutron and g-ray channels, which will be characterized during cruise phase for improved background subtraction.
r a d ia t ion coun t r a te unce r ta in ty m ode l unce r ta in ty(pa r t ic le ) [%/6 m on ths ] (dos im e tr y)p 0 .25 0 .1 20%e 0 .02 0 .35 20%CN O 0.7 20%F e 3 20%n 20 - 200 0 .25 – 0 .75 100%dos im e tr y 25 0 .7 (pe r hou r ) -
[s -1]
5x10 -3
3x10 -4
*SPE count rates will be 10 – 1000x greater depending upon the flux and spectrum of the event.
Expected RAD Count Rates (GCR only)
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber16
DLR
RAD Performance: RTG background
Tl-208
2.614 MeV
Pu-238
0.766 MeV
S.E.
2.103 MeV
D.E.
1.592 MeV
Pu-238
0.154 MeV
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber17
DLR
RAD RSH Measurement Requirements Summary
Re q u ire m e n t s ta tu s p la n sc: PF , E Mt ,c: PF , E M
s,h (SOH O, Ulysse s ) c: PF , E MLE T c: PF , E Mspe cie s d iscr im ina t ion s ,h (SOH O) c: PF , E Mt im e se r ie s s ,h (SOH O) c: PF , E M
Cha rg e d p a r t ic le s< 10 0 M e V/n uc s ,h , t w . cosm . m u on sne u t r a l pa r t ic le s < 1 00 M e V/nuc s ,h (N e udos), te le ct ron s E < 10 M e V
s,h (Dos t e l/ISS)
c: calibration, h: heritage, s: simulation, t: tests
Requirements and Expected Performance
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber18
DLR
RSH Model philosophy
• Pathfinder unit built flight-like, but no qualification standard. For CAU-internal testing and process development purposes only.
• Engineering model: flight-quality model, qualification unit for all RSH qualification tests.
• Flight model: test only to acceptance level.
• Flight spare: same standards as flight model, use for full calibration (refurbished engineering model is currently only carried as a backup option)
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber19
DLR
RSH Overview Summary
•CsI energy/thermal response characterized•RSH modelling ongoing and assuring•Manufacturing ongoing•Pathfinder SSD delivery imminent •Flight SSD bonding to wait for Pathfinder•Thermal test chamber delivered•2 diploma theses completed
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber20
DLR
RSH Overview Summary
Backup Slides
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber21
DLR
RAD Sensor Head Overview
Institute for Experimental and Applied Physics (IEAP), Kiel University
Experience:• Helios, ISEE-2, Galileo, Ulysses, SOHO, STEREO• Dostel (ISS), Matroshka, EUTEFFacilities:• fully equipped machine shop, electronics shop• calibration facilitiesFunding:• Deutsches Zentrum für Luft- und Raumfahrt (DLR) (to 12/09)• German Science Foundation (DFG)Personnel:• experienced (state-funded) personnel in group (9) and machine shop (13) plus project-funded scientists and engineers
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber22
DLR
RAD Science Requirements
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber23
DLR
GCR Interactions with the Atmosphere
• Secondary production• Energy input
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber24
DLR
RSH Overview Summary
Planetocosmics:A GEANT 4 application for tracking particles in the
vicinity of a planet
particle propagation through the Planets atmosphere
Visualization of tracks incl. production of secondaries
Calculation of the energy depositions
Calculation of the fluxes of secondaries, e.g. neutrons
Calculation also in the presence of relic crustal magnetic field
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber25
DLR
Preliminary Simulations
Pfotzer Maximum atEarth is at about 20 km
Pfotzer Maximum on Mars is at surface level
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber26
DLR
n-Measurement Implementation
MIPs deposit very little energy in anti-coincidence.
Therefore, to reach high A/C efficiency,we need to understand:
• peak shape• background• energy deposit
Measured pure cosmic muon signal in BC-430 anti-
coincidence (A/C) material.low energy deposit
insert energy
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber27
DLR
n-Measurement Implementation
Background in detectors results in partial hiding of MIPS signal.
background
muon signal
High-efficiencyA/C triggeringon MIPs requires running into background toget all MIPs.
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber28
DLR
n-Measurement Implementation
measured efficiency curve
“100%” efficiencyat low E-channels
99.8% anticoincidence efficiency demonstrated
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber29
DLR
g-Measurement Implementation
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber30
DLR
g-Measurement Implementation
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber31
DLR
RAD Performance: RTG background
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber32
DLR
RAD Performance: RTG background
• RAD single detector count rates (estimation)
inner 2 segments45 counts/s7 counts/s60 keVPIN Photo-diode C
300 µm, 2.3 cm2
middle segment, anti-coinc.30 counts/s5 counts/s60 keVPIN Photo-diode C
300 µm, 1.5 cm2
outer 3 segments with BC430 cylinder
190 counts/s +
205 counts/s
30 counts/s +
2 counts/s
60 keVPIN Photo-diode C
300 µm, 10.1 cm2
inner segment35 counts/s6 counts/s60 keVPIN Photo-diode B
300 µm, 1.9 cm2
inner 2 segments45 counts/s7 counts/s60 keVPIN Photo-diode A
300 µm, 2.3 cm2
outer 4 segments, anti-coinc.210 counts/s35 counts/s60 keVPIN Photo-diode A
300 µm, 11.6 cm2
RemarkWith RPSWithout RPSThresholdDetector
November 30, December 1, 2006MSL RAD Sensor Head (RSH) peer review
03 – RAD Sensor Head (RSH) Overview
RAD – The Radiation Assessment Detector for MSL
Wimmer-Schweingruber33
DLR
RAD Performance: RTG background
• RAD single detector counting rates (estimation, continued)
worst case area
40.0 cm2
205 counts/s **2 counts/s **150 Nphoto-electronsBC430 Cylinder, anti-c.
50 mm high
worst case area
66.5 cm2
340 counts/s2 counts/s150 Nphoto-electronsBC430 Scintillator F
12 mm high
worst case area
20.4 cm2
105 counts/s1 counts/s150 Nphoto-electronsBC430 Scintillator E
18 mm high
worst case area
10.6 cm2
190 counts/s1 counts/s40 Nphoto-electrons*CsI Scintillator D
28 mm high
RemarkWith RPSWithout RPSThresholdDetector
* Threshold does not drive the design, somewhat arbitrary
** Counted in detector C (outer 3 segments)