CRa TER PreEnvironmental Review IPER Calibration Test Planning

CRa. TER Pre-Environmental Review (I-PER) Calibration Test Planning Justin C Kasper Smithsonian Astrophysical Observatory September 10 -11, 2007 Cosmic RAy Telescope for the Effects of Radiation

Outline • • • Objective of CRa. TER calibration – Relate the ADU of the Pulse Height Analysis to the original energy deposited for each detector Review results of testing with EM leading to calibration model – Sufficient to treat energy deposited as linear function of ADU from Pulse Height Analysis (PHA) – Linearity of external pulse generator – Noise of analog electronics (less than 2 ADU) – Stability of system over time (0. 06% variation of internal calibration over 4 months, no trend) – Temperature dependence Review physics of energy deposition in detectors – 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 Verification of Requirements – Level 2 and Level 3 – Detector specifications 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 – CRa. TER Data ICD – 431 -ICD-000104 • CRa. TER 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 CRa. TER Digital Subsystem Functional Specification Detector Specification Document CRa. TER Functional Instrument Description and Performance Verification Plan Cosmic RAy Telescope for the Effects of Radiation

CRa. TER Layout Cosmic RAy Telescope for the Effects of Radiation

CRa. TER Telescope Layout Telescope in cross-section A single detector (D 5 for EM) A pair of thin and thick detectors (D 5 and D 6 for EM) Cosmic RAy Telescope for the Effects of Radiation

Establishing Linearity using External Pulser The RMS residual from a simple linear relationship is less than 0. 1%. Cosmic RAy Telescope for the Effects of Radiation

Noise q. The width of the distribution is clearly a linear function of the amplitude of the pulses, or a fixed fraction of the amplitude. q. For these measurements the noise is approximately 0. 15% of the pulse amplitude. q. These measurements therefore an upper limit on the true noise level of the CRa. TER analog electronics. Cosmic RAy Telescope for the Effects of Radiation

Stability q. Center of a peak generated by the internal pulse generator from four internal calibration runs spaced over four months q. The instrument response remained steady at the 0. 06% level. Cosmic RAy Telescope for the Effects of Radiation

Temperature q. Response of EM D 1 measurement chain as a function of fixed external pulse generator amplitude for telescope temperatures ranging from 40 -45 C. q. Total change is 0. 1% and the noise level appears to increase slightly at lower temperatures. q. The temperature dependence may be described sufficiently with two linear functions and a breakpoint at 15 C. 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 Me. V) 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

Example of D 1 D 2 Observations at MGH Cosmic RAy Telescope for the Effects of Radiation

Algorithm for Calibrating Instrument Cosmic RAy Telescope for the Effects of Radiation

Demonstration of Best-Fit Parameter Value Units D 1 Gain 0. 0768051 Me. V/ADU D 1 Offset 1. 62984 ADU D 2 Gain 0. 0249125 Me. V/ADU D 2 Offset -4. 22239 ADU Beam Peak 19. 2745 Me. V Beam Width 25. 2324 Me. V Intensity 0. 118187 106 protons D 1 Spread 1. 58370 % D 2 Spread 4. 80770 % Cosmic RAy Telescope for the Effects of Radiation

Complementary Calibration Methods • Brookhaven National Laboratory – – • EM only (radiation, cleanliness, scheduling concerns) Verified stability at high rates of heavy ions Scattered silicon and iron beams Secondary fragmentation spectra Radioactive sources of alpha radiation – FM at Aerospace during integration • Calibrated charge injection – Use a stable and calibrated charge injector to insert known amplitude pulses after detectors – FM at Aerospace during integration – Equipment brought to MIT for measurements with full instrument Cosmic RAy Telescope for the Effects of Radiation

Tests at Aerospace Additional tests make use of calibrated external pulse generator and radioactive alpha sources Cosmic RAy Telescope for the Effects of Radiation

Level 2 Verification Item Requirement Quantity CRa. TER-L 2 -01 Measure the Linear LET Energy Transfer (LET) spectrum CRa. TER-L 2 -02 Measure change in LET TEP spectrum through Tissue Equivalent Plastic (TEP) CRa. TER-L 2 -03 Minimum pathlength > 60 mm through total TEP CRa. TER-L 2 -04 Two asymmetric TEP components 1/3 and 2/3 CRa. TER-L 2 -05 Minimum LET measurement < 0. 25 ke. V per micron CRa. TER-L 2 -06 Maximum LET measurement > 2 Me. V per micron CRa. TER-L 2 -07 Energy deposition resolution < 0. 5% max energy CRa. TER-L 2 -08 Minimum D 1 D 6 geometrical factor > 0. 1 cm 2 sr Method EM S/N 2 A Verified instrument measures Initial verification using LET using energetic particle radioactive alpha sources, beams, radioactive sources, cosmic ray muons, external and models internal pulser. Beam test soon A Measured spectra consistent with modeled energetic particle energy deposition MGH test next week I 80. 947 mm as measured +/- 81 mm total TEP used 0. 001 mm I 27 and 54 mm sections of 26. 980 mm and 53. 967 mm TEP sections of TEP used, both +/- 0. 001 mm measured with micrometer T 0. 089 Ke. V/micron typical D 2 0. 145 Ke. V/micron using determined at Aerospace with measured detector thickness radioactive source, beam test and calibration next week T D 1 2. 13 Me. V/micron using measured detector thicknesses and calibration MGH test next week T <0. 1% electronics from external pulser, <0. 06% Pulser test analysis in progress, detectors using width of electronics noise expected to alpha source decrease I 0. 57 cm^2 sr derived from mechanical drawings Cosmic RAy Telescope for the Effects of Radiation

Level 3 Verification Item Requirement CRa. TER-L 3 -01 Thin and thick detector pairs CRa. TER-L 3 -02 Minimum energy CRa. TER-L 3 -02 Nominal instrument shielding Quantity 140 and 1000 microns < 250 ke. V Method I T 1524 microns Al I CRa. TER-L 3 -03 Nadir and zenith 762 microns Al field of view shielding CRa. TER-L 3 -04 Telescope stack Shield, D 1 D 2, A 1, D 3 D 4, A 2, D 5 D 6, shield CRa. TER-L 3 -05 Pathlength 10% for D 1 D 6 constraint I CRa. TER-L 3 -06 Zenith field of view CRa. TER-L 3 -07 Nadir field of view CRa. TER-L 3 -08 Calibration system CRa. TER-L 3 -09 Event selection S/N 2 148, 149 219 ke. V using Alpha source MGH test next week Verified by inspection of instrument and mechanical drawings Designed to 762 microns Measured to be 812. 8 microns zenith and 810. 3 microns nadir I I T T CRa. TER-L 3 -10 Maximum event 1, 200 events/sec transmission rate T <34 degrees D 1 D 4 <70 degrees D 3 D 6 Variable rate and gain 64 -bit mask EM 148, 988, 988 microns as measured 140 ke. V as measured based on calibration Verified by inspection of instrument and mechanical drawings Verified by inspection of instrument and mechanical Verified by inspection of instrument drawings and mechanical drawings Using geometry of telescope and uniform distribution on sky < 5% 33 degrees from mechanical drawing 69 degrees from mechanical drawing Verified by use of the internal calibration system In process Verified by testing in a beam and by using ambient cosmic ray muons MGH beam test next week Verified using internal calibration operating at high rate and beam In process Cosmic RAy Telescope for the Effects of Radiation

Detectors Table 1. 1 of Detector Specification (32 -05001 Rev E) Cosmic RAy Telescope for the Effects of Radiation

Detector Verification Summary Cosmic RAy Telescope for the Effects of Radiation

Conclusions Cosmic RAy Telescope for the Effects of Radiation

CRa. TER-L 2 -01 Measure the LETSpectrum • Requirement – The fundamental measurement of the CRa. TER 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 Me. V) Observation (Units of ADU) Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 23

CRa. TER-L 2 -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). Breakup of iron into fragments after passing through TEP measured at BNL with EM Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 24

CRa. TER-L 2 -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. FM S/N 2 Short TEP: 26. 980 mm Long TEP: 53. 967 mm Total Length: 80. 947 mm as measured +/- 0. 001 mm Greater than 60 mm Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 25

CRa. TER-L 2 -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. FM S/N 2 Short TEP: 26. 980 mm Long TEP: 53. 967 mm 26. 98/(26. 98+53. 967) = 0. 333304508 = 1/3 Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 26

CRa. TER-L 2 -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 ke. V/ micron in the Silicon. From the EM Beam Calibration at MGH D 2 Gain 0. 0249125 Me. V/ADU D 2 Offset -4. 22239 ADU D 2 thickness 988 microns D 2 Min E 0. 143934709 Me. V D 2 Min LET 0. 145682904 Ke. V/micron 0. 14 Ke. V/micron < 0. 25 Ke. V/micron Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 27

CRa. TER-L 2 -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 Me. V/ micron in the Silicon. From the EM beam calibration at MGH D 1 Gain 0. 0768051 Me. V/ADU D 1 Offset 1. 62984 ADU D 1 Thickness 148 microns D 1 Max E 314. 7188696 Me. V D 1 Max LET 2. 126478849 Me. V/micron 2. 13 Me. V/micron > 2 Me. V/micron Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 28

CRa. TER-L 2 -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. Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 29

CRa. TER-L 2 -08 Geometrical Factor • Requirement – The geometrical factor created by the first and last detectors shall be at least 0. 1 cm 2 sr. Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 30

• CRa. TER-L 3 -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. • Rational – In order to cover the LET range required by CRa. TER-L 2 -04 and CRa. TER-L 2 -05 the detectors must operate over a dynamic range of > 35, 000. This is not practical for a single detector. The dynamic range may be covered instead using two detectors with different thicknesses. • Inspection – The detector provider will report the sizes of the thin and thick detectors pairs. Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 31

• CRa. TER-L 3 -02 Minimum Energy • Requirement – The Silicon detectors shall be capable of measuring a minimum energy deposition of 250 ke. V or lower. • Rationale – This will permit calibration and aliveness tests of the detectors and the integrated instrument with common ion beams and radiation sources. For the thin detectors, this minimum energy capability may require an additional operating mode. • Test – The CRa. TER silicon detectors are delivered from the provider, Micron Semiconductor Ltd, in boards with one thin and one thick detector. Before integration into the telescope stack, these boards will be taken to a beam facility and the minimum energy will be measured. Additionally, we demonstrated at BNL that an alpha source may be used to quickly place an upper limit on the thickness of any dead layers on the detectors. Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 32

• CRa. TER-L 3 -03 Nominal instrument shielding • Requirement – The equivalent shielding of the CRa. TER telescope outside of the zenith and nadir fields of view shall be no less than 1524 microns (0. 060 inches) of aluminum. • Rationale – Shielding on the sides of the telescope is needed to limit the flux of low energy particles – mainly protons - coming through the telescope at large angles of incidence. This will prevent protons with energies less than 15 Me. V from entering the telescope. • Inspection – Mechanical drawings of the instrument will be reviewed to visually gauge the range of shielding of the detectors. Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 33

• CRa. TER-L 3 -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. • Rationale – Reduce the flux of particles that pass through the telescope at acceptable angles of incidence but place a limit on the lowest energy particle that can enter the telescope. This is especially important during solar energetic particle events. The thickness of aluminum specified in this requirement would prevent protons of approximately 10 Me. V and lower from entering the telescope. This energy was selected by examining the energy spectrum of protons during solar energetic particle events and the resulting single detector event rates. • Inspection Cosmic RAy Telescope for the Effects of Radiation – The thickness of the nadir and zenith aluminum plates will be measured with a micrometer at 06/28/2005 a minimum of five locations. J. C. Kasper – CRa. TER PDR - Science 34

• CRa. TER-L 3 -05 Telescope stack • Requirement – The telescope shall consist of a stack of components labeled from the zenith side as zenith shield (S 1), the first pair of thin (D 1) and thick (D 2) detectors, the first TEP absorber (A 1), the second pair of thin (D 3) and thick (D 4) detectors, the second TEP absorber (A 2), the third pair of thin (D 5) and thick (D 6) detectors, and the final nadir shield (S 2). • Rationale – LET measurements will be made on either side of each piece of TEP to understand the evolution of the spectrum as is passes through matter. • Inspection – The detector boards will be designed so they can only be mounted in the correct orientation (thin detector in zenith or deep space direction). The assembly will be inspected to verify the stack configuration. Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 35

• CRa. TER-L 3 -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%. • Rationale – Particles with energies that exceed 100 Me. V penetrate the entire telescope stack and produce the most secondaries. These events will provide the most significant challenge to modelers and a well-constrained pathlength simplifies the problem. This is a sufficient accuracy for subsequent modeling efforts to reproduce the observed LET spectra based on direct measurements of the primary particle spectrum. • Inspection – The minimum and maximum pathlength through pairs of detectors is determined through Cosmic RAy Telescope for the Effects of Radiation review of the mechanical drawings. 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 36

• CRa. TER-L 3 -07 Zenith field of view • Requirement – The zenith field of view, defined as D 2 D 5 coincident events incident from deep space using the naming convention in CRa. TER-L 3 -04, shall be less than 34 degrees full width. • Rationale – This field of view, from which one derives a minimum detector radius and separation, leads to a sufficient geometrical factor while still limiting the uncertainty in the pathlength traveled by the incident particle. • Inspection – The zenith field of view will be determined by reviewing mechanical drawings of the telescope. Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 37

• CRa. TER-L 3 -08 Nadir field of view • Requirement – The nadir field of view, defined as D 4 D 5 coincident events incident from the lunar surface, shall be less than 70 degrees full width. • Rationale – The anticipated flux of particles reflected from the lunar surface is many orders of magnitude smaller than the incident flux of particles from space. It is felt that a larger geometrical factor, at the expense of a larger uncertainty in the pathlength, is a justified trade. • Inspection – The nadir field of view will be determined by reviewing mechanical drawings of the telescope. Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 38

• CRa. TER-L 3 -09 Calibration system • Requirement – The CRa. TER electronics shall be capable of injecting calibration signals at with different amplitudes and rates into the measurement chain. • Rationale – Verify instrument functionality without need for radiation sources. Identify changes in measurement chain response over time following launch. • Test – The pulse heights due to pulses from the calibration system will be compared with predictions derived from an analysis of the analog electronics. Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 39

• CRa. TER-L 3 -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. • Rationale – Allows for maximizing telemetry for events of interest. Allows for adjustments of coincidence definitions in the case of increased noise in any detector. • Test – An automated program will be used to activate the calibration system on all combinations of detectors (64) and to step through all possible detector coincidences (63) and record the events that are sent to the ground support equipment. The resulting data will be analyzed to verify that the coincidence system functions correctly. Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 40

• CRa. TER-L 3 -11 Maximum event rate • Requirement – CRa. TER will be capable of transmitting primary science data, namely the energy deposited in each of the detectors, on at least 1000 events per second. • Rationale – This rate will allow us to collect statistically significant samples of minor ions such as carbon, oxygen, and iron during periods of solar activity. • Test – The calibration system will be commanded into a mode such that the synthesized event rate exceeds the maximum rate the digital system is capable of passing through the 1553 interface and it will be verified that the first 1200 events are correctly transmitted. Cosmic RAy Telescope for the Effects of Radiation 06/28/2005 J. C. Kasper – CRa. TER PDR - Science 41