CPDS Instruments Aboard CPDS Instruments Aboard ISS K.T. Lee¹, J. Flanders², E. Semones², T. Shelfer², F. Riman³ (1) University of Houston, Calhoun Rd., Houston, TX 77204 (2) Lockheed Martin Operations, 1300 Hercules Suite 100, Houston, TX 77058 (3) Jacobs pSverdrup, 2224 Bay Area Blvd., Houston, TX 77058 slide 2 Introduction . CPDS – Charged Particle Directional Spectrometer . IV instrument is placed inside the USA Laboratory module of the ISS and it was activated on April 21, 2001 . EV instrument is mounted on the S0 truss of the ISS, and was activated in late April 2002 . Instruments are presently taking data which is used for operational radiation dose level indicators . Instruments are also capable of particle and energy identification . These data can provide information about the composition of the lower radiation belts, shielding provided by Earth's magnetosphere, and differences in the radiation environments inside and outside the ISS Slide 3 Image of ISS Slide 4 EV-CPDS Image of EV-CPDS Slide 5 IV-CPDS Image of IV-CPDS Slide 6 diagram of detector with labels: 68 degrees, 31 degrees, A1, PSD1, PSD2, A2, B1, B2, B3, B4, PSD3, A3, Spare, Spare, Flash mem, C Det, CPU, 1553B, Power diagram of detector with labels: A1 Det, PSD 1, PSD2, A2 Det, B1-B6 Dets, PSD 3, A3 Det, "C" Detector, 1553B heatsink, thermostat, filters & converters, 28B & 12V DC, power board, 1553B board, typ carduide/heatsink, CPU board, flash memeory, backplane Detector Details slide 7 Detector Details . A Detectors – Square Si detector, 30.0x30.0mm, 1.0mm thick – Top and bottom brass noise shield 5mil (0.127mm) thick . PSD Detectors – Square Si strip detector, 24.0x24.0mm, 0.300mm thick – 24 strips on top surface and 24 strips on bottom surface, perpendicular to each other . B Detectors – Cylindrical Lithium drifted Si detector, 58.4mm in diameter, 5mm thick . C Detector – Sapphire 50mm in diameter, and 10mm thick – Hamamatsu PMT Slide 8 CPDS Collected Data .Counter Data – Individual detector count rates for A1, A2, A3, B2, B4, B6 and C. – Number of events above detector threshold. – Written to file every minute. . Event Data (Requires Trigger, A1 A2 coincidence) – ADC value (delta E) from A, B, and C detectors. - ADC value (delta E) and strip location for up to two events for PSD detector plane. – Written to file every trigger. . Engineering Data – Board and detector temperatures, power consumption, etc. – Written to file every 30 minutes. slide 9 CPDS Capabilities . Minimum Proton A1 count energy of 20MeV. . Minimum Proton coincident energy of 30MeV. . Maximum stopping proton energy of ~95MeV . Low energy H and He ion separation (stopping particles) . Charged particle separation for minimum ionizing particles up to Z=11 . Energy spectrum for charges with Z<4. . Proton spectrum up to ~120MeV and Helium up to ~300MeV/n. slide 10 Stopping Particles Graph of Energy Deposited in A2 vs B1 MARIE detectors labels: A2 Deposited Energy (MeV), B1 Deposited Energy (MeV), Model Data, Helium4, Helium3, Tritons, Deuterons, Protons Slide 11 Protons graph of Energy Deposited in A2 vs B1 MARIE Detectors from Protons labels: A2 Deposited Energy (MeV), B1 Deposited Energy (MeV), Backward Moving Protons, Forward Moving Stopped Protons, Forward Moving Protons Slide 12 graph of Relative CNO Abundances Detected by ISS Instruments labels: Charge (Z), IV, EV2, EV3 slide 13 Current Work . A1 and A2 thresholds were changed last week. This will increase the number of hight energy protons that are triggered on. . Characterize the trigger threshold . Data corrections (time stamp) . ISS instrument comparison Slide 14 ISS Instruments LET Spectra graph of Differnt ISS instrument LET (in water) Spectra for mid-June 2005 labels: Differential Flux (particles/cm2 sr s keVmu), LET (keV/mu)10 squared, IV, EV2, EV3, TEPC Slide 15 Threshold Change graph of Comparison of Two Threshold Settings labels A1 Channel Number, Counts, Current Threshold, Original Threshold slide 16 Summary . The analysis of the CPDS instrument data (early 2002-present) has begun. . The LEO proton spectrum from 120MeV will be measured . The LEO He spectrum from 50-300MeV/n will be measured . Minimum ionizing He-Ne relative abundances will be determined. . The IV and oEV offer the unique simultaneous bservations inside and outsid the ISS. Slide 17 Slide 18 Calibration . Detector calibration done using proton FLUKA simulation and in flight proton data. . ADC offset determined bu B detector pedestals and A detector offset is equal to zero. . Scaling factors found by overlaying simulated and real data. Slide 19 Example Calibration 3 graphs with lables H, Simulation; H2, Data; H2, Data + Simulation Slide 20 Data Selection . Cut on time between successive events (required due to CPU limitations in early data). . Passes x squared fit, where x squared = 1/n * n sigma i = 0 (delta E to i sub c (E, Z, a0 - delta E to I sub m)squared, and n is the number of detectors that contain a signal. . The calculated energy loss, delta E to i sub c, is from the Bethe-Bloch equation. . Cut on E x Delta E for stopping particles or fitted energy range for penetrating particle. . Data selection cuts are optimized using a full Monte Carlo simulation. Slide 21 CPDS Analysis Plan flow chart with labels: Geometry, FLUKA, Source Spectrum (Badhwar-O’Neill), Reverse Calibration(MeV->ADC), CPDS Raw Data File, CPDS Algorithm Simulator, CPDS Analysis, Particle Detection Efficiency, Flux Calculation, Measured Particle Spectra, Particle and Energy ID, CPDS Analysis, CPDS Raw Data File, CPDS Instrument Slide 22 Possible Simulation Improvement . Test such a simulation algorithm for existing instruments . Useful for design and development of future instruments. flow chart with labels: FLUKA, Reverse Calibration(MeV->ADC), Simulate Electronics (SPICE), CCPDS Algorithm Simulator, CPDS Raw Data File Slide 23 Monte Carlo Simulation . FLUKA is used to simulate the expected energy losses in each detector. . The algorithm simulation includes all processes that are done for data acquisition. . Initial particle spectrum input is from updated Badhwar-O’Neill model (COSPAR 2004). . Particles of all 10MeV to 10GeV, with relative abundances according to Simpson (1983). Slide 24 Monte Carlo and Data Comparison graph of FLUKA MC Simulation Z< 15 with labels: B1 Detector ADC counts and B2 Detector ADC counts graph of MARIE 2002-2003 Raw Quiet Time Data with labels: B1 Detector ADC counts and B2 Detector ADC counts slide 25 Flux Calculation . Flux is calculated using phi = (N(E)/Gt delta E )* 1(/epsilon sub s* epsilon sub d) . G = Geometry factor (3.2 cm^2 sr for trigger) . Epsilon sub d = dead time correction . Epsilon sub s = Efficiency from MC . t = total detection time . Delta E = energy range . N(E) = number of particles passing selection requirements