CRaTER Pre-Ship Review
(PSR)
Instrument Calibration
Science Requirements Compliance
Justin C Kasper
Smithsonian Astrophysical Observatory
January 3, 2008
Cosmic RAy Telescope for the Effects of Radiation
Outline
• Calibration
– Relate the ADU of the Pulse Height Analysis to the original energy
deposited for each detector
– Models of energy deposition
– Description of Massachusetts General Hospital Proton Facility
– Example of MGH observations
– Description of calibration method
– Demonstration of success with EM
– Discussion of alternative methods for redundant confirmation of
calibration
• Requirements
– Review
– Results
– Details
Cosmic RAy Telescope for the Effects of Radiation
Relevant Documents
• Project Controlled
– ESMD-RLEP-0010 (Revision A effective November 30 2005)
– LRO Mission Requirements Document (MRD) – 431-RQMT-00004
– CRaTER Data ICD – 431-ICD-000104
• CRaTER Configuration Controlled Documents
–
–
–
–
–
–
32-01205
32-01206
32-01207
32-03010
32-05001
32-05002
Instrument Requirements Document
Performance and Environmental Verification Plan
Calibration Plan
CRaTER Digital Subsystem Functional Specification
Detector Specification Document
CRaTER Functional Instrument Description and Performance Verification Plan
Cosmic RAy Telescope for the Effects of Radiation
CRaTER Layout
Cosmic RAy Telescope for the Effects of Radiation
CRaTER Telescope Layout
Telescope in cross-section
A single
detector
(D5 for
EM)
A pair of thin
and thick
detectors
(D5 and D6
for EM)
Cosmic RAy Telescope for the Effects of Radiation
CRaTER Functional Diagram
Cosmic RAy Telescope for the Effects of Radiation
6
Response Function
• Calibration Requirement
– Relate ADU to Energy Deposited at 0.5% level
• Experience with EM and both FM
–
–
–
–
System is linear at 0.1% level
Noise level is less than 0.15%
Temperature dependence is less than 0.1%
Drift with time is less than 0.02%/month
• Sufficient Response Function
–
–
–
–
–
Ei = Gi * (Ci – Oi)
Ei is energy deposited [MeV]
Gi is gain [MeV/ADU]
Ci is PHA amplitude [ADU]
Oi is an offset [ADU]
Cosmic RAy Telescope for the Effects of Radiation
Energy Loss of Protons in Silicon
Observations of scattering
Simulations of energy deposit
Cosmic RAy Telescope for the Effects of Radiation
Signature of Spread Energy Protons in Detector Pair
Simulation (Units of MeV)
Observation (Units of ADU)
Cosmic RAy Telescope for the Effects of Radiation
MGH Beam Testing with EM
Cosmic RAy Telescope for the Effects of Radiation
Algorithm for Calibrating Instrument
Cosmic RAy Telescope for the Effects of Radiation
Observations and Simulations
Cosmic RAy Telescope for the Effects of Radiation
FM S/N 01 Calibration Parameters
(CRA0120071216130951L0 CRA0120071216133252L0 CRA0120071216135457L0)
Detector
D1
Var
Gain
Value
78.360688
Error
Units
0.13793621KeV/ADU
Offset
-0.45246847
D2
Gain
Offset
22.676271
-7.4135601
0.058317026KeV/ADU
0.56938238ADU
0.26
7.68
D3
Gain
81.768613
0.099649736KeV/ADU
0.12
D4
D5
D6
Offset
-0.19174824
Gain
Offset
Gain
22.58814
0.70068405
83.6859
Offset
-0.68360328
Gain
Offset
22.299163
3.2444374
0.096347427ADU
% Error
0.18
21.29
0.053966765ADU
28.14
0.040475074KeV/ADU
0.11857201ADU
0.17280925KeV/ADU
0.18
16.92
0.21
0.068337712 ADU
10.00
0.048207834 KeV/ADU
0.10117969ADU
Cosmic RAy Telescope for the Effects of Radiation
0.22
3.12
Calibration and Derived Parameters
Flight Model S/N 02
Flight Model S/N 01
(Selected for delivery to NASA)
D1
D3
D5
D2
D4
D6
D1
D3
D5
D2
D4
D6
-0.3 -0.5 -0.4
0.9 -2.2
0.9 -0.5 -0.2 -0.7 -7.4
0.7
3.2
Var Unit
Offset ADU
KeV/
Gain ADU
81.6 82.9 80.6 22.2 22.4 22.2 78.4 81.8 83.7 22.7
Min E KeV
435.5 453.5 436.0 90.8 162.5 91.5 427.3 424.5 475.6 281.5
MeV/
Max E um
334.1 339.6 330.2 91.0 92.0 90.9 321.0 334.9 342.8 93.1
Thick um
148 149 149 1000 1000 1000 152 147 148 933
Min KeV/
LET
um
2.9
3.0
2.9
0.1
0.2
0.1
2.8
2.9
3.2
0.3
Max MeV/
LET
um
2.3
2.3
2.2
0.1
0.1
0.1
2.1
2.3
2.3
0.1
Max/
Min #
24847 14028 24227
20289 21890 55148
Cosmic RAy Telescope for the Effects of Radiation
22.6
97.1
22.3
39.1
92.5
933
91.3
932
0.1
0.0
0.1
0.1
LET Range for Both Instruments
Flight Model
S/N 01
(Now flight
spare)
Flight Model
S/N 02
(Selected for
delivery to
NASA)
Cosmic RAy Telescope for the Effects of Radiation
Level 1 Requirements and Data Products
Level 1 Requirements
Level 1 Data Products
RLEP-LRO-M10
Provide Linear Energy Transfer
(LET) spectra of cosmic rays
(particularly above 10 MeV), most
critically important to the
engineering and modeling
communities to assure safe, longterm, human presence in space.
The LRO shall characterize the
deep space radiation environment
at energies in excess of 10 MeV in
lunar orbit, including neutron
albedo.
RLEP-LRO-M20
The LRO shall measure the
deposition of deep space
radiation on human equivalent
tissue while in the lunar orbit
environment.
Provide LET spectra behind
different amounts and types of areal
density, including tissue equivalent
plastic.
Cosmic RAy Telescope for the Effects of Radiation
16
Flow of Level 1 to Level 2 Requirements
Level 2 Instrument Requirements
RLEP-LRO-M10
Characterize deep
space radiation
environment
Level 1 Parent
Requirements
RLEP-LRO-M20
Radiation effects on
human equivalent
tissue
Measure the Linear Energy Transfer (LET) spectrum
01
Measure change in LET spectrum through Tissue
Equivalent Plastic (TEP)
02
Minimum pathlength through total TEP > 60 mm
03
Two asymmetric TEP components
1/3 and 2/3 total length
04
Minimum LET measurement 0.2 keV per micron
05
Maximum LET measurement 2 MeV per micron
06
Energy deposition resolution < 0.5% max energy
07
Minimum full telescope geometrical factor 0.1 cm2 sr
08
Cosmic RAy Telescope for the Effects of Radiation
Flow of Requirements
Level 2 Parent
Requirements
Level 3 Instrument Requirements
Thin and thick detector pairs 140 & 1000 μm
01
Minimum energy < 250 keV
02
Nominal instrument shielding > 1524 μm Al
03
Nadir and zenith field of view shielding < 762 μm
04
Telescope stack
05
Pathlength constraint < 10% for D1D6
06
Zenith field of view < 33o
07
Nadir field of view < 70o
08
05
Calibration system
09
06
Event selection
10
Maximum transmission rate > 1000 events/second
11
01
02
03
04
07
Cosmic RAy Telescope for the Effects of Radiation
Testing Validation Techniques with the CRaTER Prototype
• Berkeley National
Laboratory 88” Cyclotron
(Ions, 20 MeV/nuc)
• Massachusetts General
Hospital Proton Therapy
Center (0-300 MeV p)
• Brookhaven National
Laboratory (Gev/nuc Fe)
Minimum LET measurement 0.2 keV
per micron
MGH Proton Accelerator
Maximum LET measurement 2MeV
per micron
Energy deposition resolution < 0.5%
max energy
Cosmic RAy Telescope for the Effects of Radiation
Level 2 Requirements Verification Outline
Item
Requirement
CRaTER-L2-01 Measure the Linear Energy Transfer
(LET) spectrum
Quantity
Method
LET
A
CRaTER-L2-02 Measure change in LET spectrum
TEP
through Tissue Equivalent Plastic (TEP)
CRaTER-L2-03 Minimum pathlength through total TEP > 60 mm
I
CRaTER-L2-04 Two asymmetric TEP components
1/3 and 2/3
I
CRaTER-L2-05 Minimum LET measurement
< 0.25 keV per
micron
T
CRaTER-L2-06 Maximum LET measurement
T
CRaTER-L2-07 Energy deposition resolution
> 2 MeV per
micron
< 0.5% max energy
CRaTER-L2-08 Minimum D1D6 geometrical factor
> 0.1 cm sr
2
Cosmic RAy Telescope for the Effects of Radiation
A
T
I
Level 2
Verification
Item
CRaTER-L2-01
Requirement
Measure the Linear
Energy Transfer (LET)
spectrum
CRaTER-L2-02 Measure change in LET
spectrum through Tissue
Equivalent Plastic (TEP)
CRaTER-L2-03 Minimum pathlength
through total TEP
Quantity
LET
Method
A
TEP
S/N 2
S/N 1
Verified instrument measures LET using energetic particle
beams, radioactive sources, models
A MGH Beam Run September
MGH Beam Run December
80.946 mm as measured +/0.001 mm
> 60 mm
I
80.947 mm as measured +/0.001 mm
I
26.972 mm and 53.992 mm 26.979 mm and 53.967 mm
sections of TEP used, both sections of TEP used, both +/+/- 0.001 mm measured with
0.001 mm measured with
micrometer
micrometer
CRaTER-L2-04
Two asymmetric TEP
components
1/3 and 2/3
CRaTER-L2-05
Minimum LET
measurement
< 0.25 keV
per micron
T
2.9, 3.0, 2.9, 0.09, 0.16, 0.09
2.8, 2.8, 3.2, 0.3, 0.1, 0.04
CRaTER-L2-06
Maximum LET
measurement
> 2 MeV per
micron
T
2.2, 2.2, 2.2, 0.09, 0.09, 0.09
2.1, 2.2, 2.3, 0.09, 0.09, 0.09
CRaTER-L2-07
Energy deposition
resolution
< 0.5% max
energy
T
CRaTER-L2-08
Minimum D1D6
geometrical factor
> 0.1 cm sr
2
I
<0.1% electronics from external pulser, <0.06% detectors
using width of alpha source, <0.25% gain uncertainty from
beam calibrations at MGH
0.57 cm^2 sr derived from mechanical drawings
Cosmic RAy Telescope for the Effects of Radiation
Level 3 Requirements Verification Outline
Item
CRaTER-L3-01
Quantity
140 and 1000 microns
CRaTER-L3-05
Requirement
Thin and thick detector
pairs
Minimum energy
Nominal instrument
shielding
Nadir and zenith field of
view shielding
Telescope stack
CRaTER-L3-06
CRaTER-L3-07
CRaTER-L3-08
CRaTER-L3-09
CRaTER-L3-10
CRaTER-L3-11
CRaTER-L3-02
CRaTER-L3-03
CRaTER-L3-04
Method
I
< 250 keV
1524 microns Al
I
762 microns Al
I
Shield, D1D2, A1, D3D4,
A2, D5D6, shield
I
Pathlength constraint
Zenith field of view
Nadir field of view
Calibration system
Event selection
10% for D1D6
<34 degrees D1D4
<70 degrees D3D6
Variable rate and gain
64-bit mask
I
I
I
Maximum event
transmission rate
1,000 events/sec
Cosmic RAy Telescope for the Effects of Radiation
T
T
T
T
Level 3
Verification
Item
Requirement
Quantity
CRaTER-L3-01 Thin and thick 140 and 1000
detector pairs
microns
CRaTER-L3-02 Minimum
< 250 keV
energy
CRaTER-L3-03 Nominal
instrument
shielding
S/N 2
148, 149, 149, 1000, 1000, 1000
S/N 1
152, 147, 148, 933, 933, 932
T
435.4, 453.4, 436.0, 90.8, 162.4,
91.4
427.2, 424.52, 475.6, 281.4, 97.1,
39.1
1524 microns Al I
CRaTER-L3-04 Nadir and zenith 762 microns Al
field of view
shielding
CRaTER-L3-05 Telescope stack Shield, D1D2,
A1, D3D4, A2,
D5D6, shield
CRaTER-L3-06 Pathlength
10% for D1D6
constraint
CRaTER-L3-07 Zenith field of
view
CRaTER-L3-08 Nadir field of
view
CRaTER-L3-09 Calibration
system
CRaTER-L3-10 Event selection
Method
I
Verified by inspection of instrument and mechanical drawings
I
Measured to be 812.8 microns
zenith and 810.3 microns nadir
Measured to be 812.8 microns zenith
and 810.3 microns nadir
I
Verified by inspection of instrument and mechanical drawings
I
Using geometry of telescope and uniform distribution on sky < 5%
<34 degrees
I
D1D4
<70 degrees
I
D3D6
Variable rate and
gain
64-bit mask
33 degrees from mechanical drawing
69 degrees from mechanical drawing
T
Verified by use of the internal calibration system
T
Verified by testing in a beam and by using ambient cosmic ray muons
CRaTER-L3-11 Maximum event 1,200 events/sec
T
Verified using the internal pulser at 2 kHz and the MGH beam facility
transmission rate
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L2-01 Measure the LETSpectrum
• Requirement
–
The fundamental measurement of the CRaTER instrument shall be of the linear energy transfer
(LET) of charged energetic particles, defined as the mean energy absorbed (∆E) locally, per unit
path length (∆l), when the particle traverses a silicon solid-state detector.
MGH proton measurements
Simulation (Units of MeV)
Observation (Units of ADU)
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L2-02 Measure LET Spectrum after Passing through TEP
• Requirement
– The LET spectrum shall be measured before entering and after propagating though a
compound with radiation absorption properties similar to human tissue such as A-150
Human Tissue Equivalent Plastic (TEP).
Iron nuclei enter D3
Iron breaks
up within
first section
of TEP
Breakup of
iron into
fragments
after passing
through TEP
measured at
BNL with EM
Iron nuclei enter D1
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L2-03 Minimum Pathlength through total TEP
• Requirement
– The minimum pathlength through the total amount of TEP in the telescope shall be at least
60 mm.
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L2-04 Two asymmetric TEP components
• Requirement
– The TEP shall consist of two components of different length, 1/3 and 2/3 the total length of
the TEP. If the total TEP is 61 mm in length, then the TEP section closest to deep space will
have a length of approximately 54 mm and the second section of TEP will have a length of
approximately 27 mm.
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L2-05 Minimum LET measurement
• Requirement
– At each point in the telescope where the LET spectrum is to be observed, the minimum LET
measured shall be no greater than 0.25 keV/ micron in the Silicon.
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L2-06 Maximum LET measurement
• Requirement
– At each point in the telescope where the LET spectrum is to be observed, the maximum
LET measured shall be no less than 2 MeV/ micron in the Silicon.
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L2-07 Energy deposition resolution
• Requirement
– The pulse height analysis of the energy deposited in each detector shall have an energy
resolution better than 1/200 the maximum energy measured by that detector.
Upper limit on system noise
is less than 0.15% < 0.5%
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L2-08 Geometrical Factor
• Requirement
– The geometrical factor created by the first and last detectors shall be at least 0.1 cm2 sr.
1  2
2
G   2  r1  r6  z 2 
2 
r
1
2
 r2  z
2
  4r r
2 2
2
1
2
2



r1 = 1.75 cm
r2 = 1.75 cm
Z = 12.71 – 0.25 = 12.46 cm
G = 0.57 > 0.1 cm2 sr
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L3-01 Thin and thick detector pairs
• Requirement
– The telescope stack shall contain adjacent pairs of thin and thick Silicon detectors. The
thickness of the thin detectors will be approximately 140 microns and the thick detectors will
be approximately 1000 microns.
Thickness
D3
D5
D2
D4
D6
D1
D3
D5
D2
D4
D6
D008
E005
E006
E007
D010
D004
D005
E001
E008
E011
Detector S/N
D006
D1
FM S/N 2
D007
FM S/N 1
148 149 149 1000 1000 1000 152 147 148 933 933 932
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L3-02 Minimum Energy
• Requirement
– The Silicon detectors shall be capable of measuring a minimum energy deposition of 250
keV or lower.
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L3-03 Nominal instrument shielding
• Requirement
– The equivalent shielding of the CRaTER telescope outside of the zenith and nadir fields of
view shall be no less than 1524 microns (0.060 inches) of aluminum.
Verified by inspection of mechanical
drawings
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L3-04 Nadir and zenith field of view shielding
• Requirement
– The zenith and nadir fields of view of the telescope shall have no more than 762 microns
(0.030) of aluminum shielding.
EM built to 762 microns
FM S/N 2 end caps specified to be 0.030” +/- 0.002”, or 762 +/- 51 microns
Measured to be 812.8 microns zenith and 810.3 microns nadir
812 and 810 microns > 762 microns
Within the design tolerance of the mechanical drawing, but nonetheless is
slightly greater than the requirement specified. We have filed a Nonconforming Material Report (NMR).
The science team feels that this difference in thickness does not affect the
quality of the measurements made, since it is still sufficiently thin to allow
protons to enter the telescope over the desired energy range, as long as the
thickness is measured so it can be fed into the models.
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L3-05 Telescope stack
• Requirement
– The telescope shall consist of a stack of components labeled from the zenith side as zenith
shield (S1), the first pair of thin (D1) and thick (D2) detectors, the first TEP absorber (A1),
the second pair of thin (D3) and thick (D4) detectors, the second TEP absorber (A2), the
third pair of thin (D5) and thick (D6) detectors, and the final nadir shield (S2).
Verified by direct inspection
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L3-06 Full telescope pathlength constraint
• Requirement
– The root mean squared (RMS) uncertainty in the length of TEP traversed by a particle that
traverses the entire telescope axis shall be less than 10%.
RMS from Monte Carlo
is 0.78% < 10%
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L3-07 Zenith field of view
• Requirement
– The zenith field of view, defined as D2D5 coincident events incident from deep space using
the naming convention in CRaTER-L3-04, shall be less than 34 degrees full width.
By inspection 33 < 34 degrees
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L3-08 Nadir field of view
• Requirement
– The nadir field of view, defined as D4D5 coincident events incident from the lunar surface,
shall be less than 70 degrees full width.
By inspection, 69 < 70
degrees
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L3-09 Calibration system
• Requirement
–
The CRaTER electronics shall be capable of injecting calibration signals at with different
amplitudes and rates into the measurement chain.
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L3-10 Event selection
• Requirement
–
A command capability shall exist to allow specification of detector coincidences that will
be analyzed and sent to the spacecraft for transmission to the ground.
Shown that this works using proton beam at MGH
Cosmic RAy Telescope for the Effects of Radiation
CRaTER-L3-11 Maximum event rate
• Requirement
– CRaTER will be capable of transmitting primary science data, namely the energy deposited
in each of the detectors, on at least 1000 events per second.
Verified by exposure to
proton and iron beams, and
by running internal
calibration system at 2kHz
Cosmic RAy Telescope for the Effects of Radiation
Conclusions
• We have conducted multiple calibration activities for both flight models
– External pulse generator
– Radioactive sources
– Proton beam at MGH
• Absolute calibration of each detector
– Linear response
– Solve for gain and offsets for each detector by fitting to numerical
simulation
• Verification
– Performance requirements verified by inspection or testing
– Results from beam calibration propagated to determine minimum
energy, energy resolution, min and max LET
Cosmic RAy Telescope for the Effects of Radiation