CRaTER Pre-Ship Review (PSR) Instrument Calibration Science Requirements Compliance Justin C Kasper Smithsonian Astrophysical Observatory January 3, 2008
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
Project Controlled Relevant Documents 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 Instrument Requirements Document 32-01206 Performance and Environmental Verification Plan 32-01207 Calibration Plan 32-03010 CRaTER Digital Subsystem Functional Specification 32-05001 Detector Specification Document 32-05002 CRaTER Functional Instrument Description and Performance Verification Plan
CRaTER Layout
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)
CRaTER Functional Diagram 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 E i = G i * (C i O i ) E i is energy deposited [MeV] G i is gain [MeV/ADU] C i is PHA amplitude [ADU] O i is an offset [ADU]
Energy Loss of Protons in Silicon Observations of scattering Simulations of energy deposit
Signature of Spread Energy Protons in Detector Pair Simulation (Units of MeV) Observation (Units of ADU)
MGH Beam Testing with EM
Algorithm for Calibrating Instrument
Observations and Simulations
FM S/N 01 Calibration Parameters (CRA0120071216130951L0 CRA0120071216133252L0 CRA0120071216135457L0) Detector Var Value Error Units % Error D1 Gain 78.360688 0.13793621KeV/ADU 0.18 Offset -0.45246847 0.096347427ADU 21.29 D2 Gain 22.676271 0.058317026KeV/ADU 0.26 Offset -7.4135601 0.56938238ADU 7.68 D3 Gain 81.768613 0.099649736KeV/ADU 0.12 Offset -0.19174824 0.053966765ADU 28.14 D4 Gain 22.58814 0.040475074KeV/ADU 0.18 Offset 0.70068405 0.11857201ADU 16.92 D5 Gain 83.6859 0.17280925KeV/ADU 0.21 Offset -0.68360328 0.068337712ADU 10.00 D6 Gain 22.299163 0.048207834KeV/ADU 0.22 Offset 3.2444374 0.10117969ADU 3.12
Calibration and Derived Parameters Flight Model S/N 02 Flight Model S/N 01 (Selected for delivery to NASA) Var Unit D1 D3 D5 D2 D4 D6 D1 D3 D5 D2 D4 D6 Offset ADU -0.3-0.5-0.4 0.9-2.2 0.9-0.5-0.2-0.7-7.4 0.7 3.2 KeV/ Gain ADU 81.6 82.9 80.6 22.2 22.4 22.2 78.4 81.8 83.7 22.7 22.6 22.3 Min E KeV 435.5 453.5 436.0 90.8 162.5 91.5 427.3 424.5 475.6 281.5 97.1 39.1 MeV/ Max Eum 334.1 339.6 330.2 91.0 92.0 90.9 321.0 334.9 342.8 93.1 92.5 91.3 Thick um 148 149 149 1000 1000 1000 152 147 148 933 933 932 Min LET KeV/ um 2.9 3.0 2.9 0.1 0.2 0.1 2.8 2.9 3.2 0.3 0.1 0.0 Max LET MeV/ um 2.3 2.3 2.2 0.1 0.1 0.1 2.1 2.3 2.3 0.1 0.1 0.1 Max/ Min # 24847 14028 24227 20289 21890 55148
LET Range for Both Instruments Flight Model S/N 01 (Now flight spare) Flight Model S/N 02 (Selected for delivery to NASA)
Level 1 Requirements and Data Products Level 1 Requirements RLEP-LRO-M10 The LRO shall characterize the deep space radiation environment at energies in excess of 10 MeV in lunar orbit, including neutron albedo. Level 1 Data Products 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. 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. 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 Measure change in LET spectrum through Tissue Equivalent Plastic (TEP) Minimum pathlength through total TEP > 60 mm Two asymmetric TEP components 1/3 and 2/3 total length Minimum LET measurement 0.2 kev per micron Maximum LET measurement 2 MeV per micron Energy deposition resolution < 0.5% max energy Minimum full telescope geometrical factor 0.1 cm 2 sr 01 02 03 04 05 06 07 08
Level 2 Parent Requirements 01 02 03 04 05 06 07 Flow of Requirements Level 3 Instrument Requirements Thin and thick detector pairs 140 & 1000 µm Minimum energy < 250 kev Nominal instrument shielding > 1524 µm Al Nadir and zenith field of view shielding < 762 µm Telescope stack Pathlength constraint < 10% for D1D6 Zenith field of view < 33 o Nadir field of view < 70 o Calibration system Event selection Maximum transmission rate > 1000 events/second 01 02 03 04 05 06 07 08 09 10 11
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
Level 2 Requirements Verification Outline Item Requirement Quantity Method CRaTER-L2-01 Measure the Linear Energy Transfer LET (LET) spectrum CRaTER-L2-02 Measure change in LET spectrum throughtep Tissue Equivalent Plastic (TEP) CRaTER-L2-03 Minimum pathlength through total TEP > 60 mm I A A CRaTER-L2-04 Two asymmetric TEP components 1/3 and 2/3 I CRaTER-L2-05 Minimum LET measurement < 0.25 kev per micron CRaTER-L2-06 Maximum LET measurement > 2 MeV per T micron CRaTER-L2-07 Energy deposition resolution < 0.5% max energy T T CRaTER-L2-08 Minimum D1D6 geometrical factor > 0.1 cm 2 sr I
Level 2 Verification Item Requirement Quantity Method S/N 2 S/N 1 CRaTER-L2-01 Measure the Linear Energy Transfer (LET) spectrum LET A Verified instrument measures LET using energetic particle beams, radioactive sources, models CRaTER-L2-02 Measure change in LET spectrum through Tissue Equivalent Plastic (TEP) CRaTER-L2-03 Minimum pathlength through total TEP TEP A MGH Beam Run September MGH Beam Run December > 60 mm I 80.947 mm as measured +/- 0.001 mm 80.946 mm as measured +/- 0.001 mm CRaTER-L2-04 Two asymmetric TEP components 1/3 and 2/3 I 26.972 mm and 53.992 mm sections of TEP used, both +/- 0.001 mm measured with micrometer 26.979 mm and 53.967 mm sections of TEP used, both +/- 0.001 mm measured with micrometer 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 <0.1% electronics from external pulser, <0.06% detectors using width of alpha source, <0.25% gain uncertainty from beam calibrations at MGH CRaTER-L2-08 Minimum D1D6 geometrical factor > 0.1 cm 2 sr I 0.57 cm^2 sr derived from mechanical drawings
Level 3 Requirements Verification Outline Item Requirement Quantity Method CRaTER-L3-01 Thin and thick detector pairs 140 and 1000 microns I CRaTER-L3-02 Minimum energy < 250 kev T CRaTER-L3-03 Nominal instrument 1524 microns Al I shielding CRaTER-L3-04 Nadir and zenith field of 762 microns Al I view shielding CRaTER-L3-05 Telescope stack Shield, D1D2, A1, D3D4, A2, D5D6, shield I CRaTER-L3-06 Pathlength constraint 10% for D1D6 I CRaTER-L3-07 Zenith field of view <34 degrees D1D4 I CRaTER-L3-08 Nadir field of view <70 degrees D3D6 I CRaTER-L3-09 Calibration system Variable rate and gain T CRaTER-L3-10 Event selection 64-bit mask T CRaTER-L3-11 Maximum event transmission rate 1,000 events/sec T
Item Requirement Quantity Method S/N 2 S/N 1 CRaTER-L3-01 Thin and thick detector pairs 140 and 1000 microns I 148, 149, 149, 1000, 1000, 1000 152, 147, 148, 933, 933, 932 CRaTER-L3-02 Minimum energy < 250 kev 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 CRaTER-L3-03 Nominal instrument shielding CRaTER-L3-04 Nadir and zenith field of view shielding CRaTER-L3-05 Telescope stack Shield, D1D2, A1, D3D4, A2, D5D6, shield CRaTER-L3-06 Pathlength constraint 1524 microns Al I Verified by inspection of instrument and mechanical drawings 762 microns Al I Measured to be 812.8 microns zenith and 810.3 microns nadir I Level 3 Verification Measured to be 812.8 microns zenith and 810.3 microns nadir Verified by inspection of instrument and mechanical drawings 10% for D1D6 I Using geometry of telescope and uniform distribution on sky < 5% CRaTER-L3-07 Zenith field of <34 degrees I 33 degrees from mechanical drawing view D1D4 CRaTER-L3-08 Nadir field of view <70 degrees D3D6 I 69 degrees from mechanical drawing CRaTER-L3-09 Calibration Variable rate and T Verified by use of the internal calibration system system gain CRaTER-L3-10 Event selection 64-bit mask 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
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. Simulation (Units of MeV) MGH proton measurements Observation (Units of ADU)
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). Fragments pass through telescope 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
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.
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.
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.
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.
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%
Requirement 1 G = ( 2 CRaTER-L2-08 Geometrical Factor The geometrical factor created by the first and last detectors shall be at least 0.1 cm 2 sr. 2 & $ r % 2 1 + r 2 6 r1 = 1.75 cm r2 = 1.75 cm Z = 12.71 0.25 = 12.46 cm G = 0.57 > 0.1 cm 2 sr + z 2 ' ( ) 2 2 2 2 2 2 # r + r + z ' 4r r! " 1 2 1 2
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.
Requirement CRaTER-L3-02 Minimum Energy The Silicon detectors shall be capable of measuring a minimum energy deposition of 250 kev or lower.
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
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.
Requirement CRaTER-L3-05 Telescope stack 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
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%
Requirement CRaTER-L3-07 Zenith field of view 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
Requirement CRaTER-L3-08 Nadir field of view 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
Requirement CRaTER-L3-09 Calibration system The CRaTER electronics shall be capable of injecting calibration signals at with different amplitudes and rates into the measurement chain.
Requirement CRaTER-L3-10 Event selection 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
Requirement CRaTER-L3-11 Maximum event rate 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
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