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Preparing For a Medipix-Based Dosimeter Demonstration on the International Space Station

Preparing For a Medipix-Based Dosimeter Demonstration on the International Space Station. Lawrence Pinsky Physics Department University of Houston. Lawrence Pinsky 1* , Nicholas Stoffle 1,2 , Son Hoang 1 ,

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Preparing For a Medipix-Based Dosimeter Demonstration on the International Space Station

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  1. Preparing For a Medipix-Based Dosimeter Demonstration on the International Space Station Lawrence Pinsky Physics Department University of Houston ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  2. Lawrence Pinsky1*, Nicholas Stoffle1,2, Son Hoang1, Ricardo Vilalta1, Kerry Lee2, Neal Zapp2, Edward Semones2, Daniel Turecek3, Jan Jakubek3, Zdenek Vykydal3, Stanislav Pospisil3, Hisashi Kitamura4,, Yukio Uchihori4, Nakahiro Yasuda4 and Ondrej Ploc4 1Physics Department, University of Houston, Houston, Texas, USA 2NASA Johnson Space Center, Houston, Texas, USA 3Institute for Experimental and Applied Physics, Czech Technical University in Prague, Czech Republic 4Radiation Measurement Research Section, National Institute of Radiological Sciences, Chiba, Japan Medipix2 and Medipix3 are CERN-Based Collaborations… (IEAP-CTU-Prague and the University of Houston are Members ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  3. Hybrid Pixel Detector Detector and electronics readout are optimized separately ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  4. Hybrid Pixel Detector - Cross Section UH is currently working on epitaxial deposition techniques that will facilitate the creation of high efficiency Embedded-Neutron-Converter detectors ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  5. 65,536 Bump-Bonds on each unit… ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  6. TimePix Cell Schematic • Charge sensitive Preamp/Shaper w/ individual leakage current compensation • Discriminator with globally adjustable thresholds & individual 4-bit fine tuning offset • Individually settable test and mask bits for each pixel • External shutter activates the counter (can be as short as 10 ns, • but 100 ns is the practical limit) • 14-bit output register (11,810 decimal) • …with Overflow indication • Each pixel can have its mode • (ADC or TDC) set independently ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  7. TimePix Threshold Calibration Calibrates the 4-bit (16 level) Threshold Offsets for each pixel. The RED histogram is the distribution of noise turn-on points with all bits set to high. The BLUE histogram is the corresponding low setting. The BLACK histogram is the corrected result. Each channel is ~20 e-… ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  8. Time-Over-Threshold (“ADC”) Mode (P0=1,P1=0) “Shutter” Window 33 50 12 Clock Out Discriminator Output Analog Signals 2Ke- 4Ke- 2Ke- Threshold 10MHz Clock 100MHz Clock ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  9. TimePix and its TOT mode If the pulse shape is triangular then Time over Threshold is proportional to collected charge i.e. to energy. Due to limited bandwidth the pulse can be NEVER perfectly triangular. Non-linear TOT to energy dependence TOT Energy Energy Time Counter in each pixel can be used as Timer to measure detection time => TOF experiments, TPC detectors, … Wilkinson type ADC to measure energy of each particle detected. Calibration curve Threshold ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  10. Charge Clusters The electron-hole pairs liberated by traversing moving charges drifts in the bias voltage and also diffuses during the process, creating a multi-pixel cluster. TimePix Incident Particle “PIXELMAN” Image ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  11. Dosimetry in Space • Our approach is to try and Characterize the Radiation Field as precisely as possible as a function of time. • To do that, we need to assess the radiation environment in terms of the Charge AND Energy of the individual particles that are present. • …HOWEVER, because of the “Z2 effect” and the shape of the energy-loss curves, it is possible for different ions to have the same dE/dx in a thin detector… • Slow lower-Z particles seen in the dosimeter will not penetrate deeply into the body, and can be mimicked by higher-Z faster particles, which CAN penetrate deeply… • SO, again, “Our approach is to try and Characterize the Radiation Field as precisely as possible as a function of time.” ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  12. Measuring Charge AND Energy • If you know b then measuring the charge is reasonably simple because of the Z2 dependence. • In accelerator experiments the interaction fragments from the projectile particle is generally moving at close to the projectile’s original velocity, at least for forward fragments. • However, if you have no a priori velocity information, the problem is the BETHE-BLOCH Equation… (One can observe the behavior over a longer distance, or look for track structure differences…) All charge-1 particles. Higher charge particles are raised by the square of the charge at the same momenta ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  13. Also, dE/dx ≠ LET(High Energy d-Rays) • Because the number of d-rays produced per unit track length in the Air prior to entering the Si is much less than in the the Si… • …The highest energy d-rays carry away more energy from the Si than enters from the air. • HOWEVER—It is the High Energy d-rays that offer the prospect of telling the difference between the different particle velocities with the same dE/dx… TimePix Air d-Rays Incident Particle Si Si ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  14. FLUKA Medipix (TimePix)Heavy Ion Simulations Note the ~10% differences in the peak location, with the measurements being 10% lower than the simulations due to peak saturation effects… However, the widths are the same  The Saturation effects are common… ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  15. TimePix in the HIMAC Beams • Data have been taken at HIMAC in some dedicated and many parasitic runs… • Runs at a range of incident angles and with different detector settings are typically taken… • The primary beams were (MeV/A): • 1H (p) 160 • 4He 180 & 230 • 12C 230 • 14N 180 & 290 • 16O 100 & 230 • 20Ne 180, 430 & 600 • 28Si 400, 600 & 800 • 56Fe 500 ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  16. Examples of Individual (Normal Incidence) “Tracks” 100 MeV/A O 600 MeV/A Si 180 MeV/A Ne 800 MeV/A Si The high energy d-rays are clear in the higher energy tracks. These are not yet calibrated, and the study to be preformed is to explore the detailed resolution possible when all the information is included… The next goal is to be able to model these tracks in the FLUKA Monte Carlo code… ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  17. 800 MeV/A Si 85 degree Tracks • The tracks are from particles diving downward from left to right. • As they pass though the solder-bumps and into the underlying chip after leaving the Si detector layer. • Some of the high energy d-rays from the chip enter the overlying detector layer… ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  18. 16O @ 100 MeV/A—0° & 60° Averaged Cluster Shapes(Azimuthal & Polar Angle resolution ~ 1 Degree) 60° 0° ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  19. TimePix as an in- Flight Dosimeter 84°N Latitude ~ 180 ° Longitude @ Local Midnight at 35,000 ft Australia 100 Sec Integrated Image The Dose RATE is ~ 50 times the surface background rate (in Houston) w/o Neutron Corr. ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  20. M.D. Anderson Proton Therapy Center Scanning Beam Frame This 10 ms frame was taken in the high intensity scanning beam at the M.D. Anderson Proton Therapy Center in Houston, Texas. The fluence is > 108 protons/cm2s. The beam is centered near the lower right edge of the frame and is nominally 1 cm in diameter. The frame is ~1.4 cm across. At this fluence, the charge sensitive pre-amp shaping return feedback had to be minimized to reduce the total current draw on the Medipix chip to avoid a voltage sag that would have affected the chip’s overall functioning. Individual p tracks are visible in the core of the beam and in the beam’s halo… ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  21. NASA HyPRD—SDTOHybrid Pixel Radiation Dosimeter—Station Demonstration Test Objective • At the request of SRAG, We are currently preparing to fly several Timepix-based USB interfaced units (HyPRD’s) as an SDTO on the ISS possibly later this year… • The SDTO units are the size and weight of a typical “Memory Stick” Flash Drive. • There is also a Phase I SBIR that is producing a prototype stand-alone interface (Battery-Powered, Wireless, with local Analysis Capability and Readout with Alarms)—Phase II will hopefully begin this Fall Earlier Medipix2 USB Interface First ISS Flight Unit Prototype ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  22. SDTO ISS Flight Software(Via USB Interface) • The flight software will run on the existing ISS Lenovo laptops attached to the HyPRD unit the via a standard USB Type-A connector • It will have automatic frame-length and rate adjustment capability… • It will display cumulative (dose)and current (dose-rates) [NCRP-153] Dose-Equivalent locally on the laptop. • Full data frames will be downloaded to the ground for analysis in a Root-based software environment… ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  23. HyPRD Hardware Processing at CERN HyPRD Wire-bonds ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  24. LUCID – LangtonUltimate Cosmic ray Intensity DetectorTimePix’s First Space Mission—Educational Outreach(UK Satellite to be Launched Q1—2012) 1.4 cm • 5 TimePix Detectors (0.7 mm Al dome) • Sun-Synchronous Polar Orbit (98° @ 11:00) • Programmable Signal Processor for on-orbit data analysis… Velocity ISSRMP - Shanghai - L. Pinsky - 6/2/2011 Down

  25. LUCID • Educational Outreach • PI is Becky Parker from the Langton School in Canterbury, UK. • Data will be available in Daily downloads to High School groups worldwide via the Web… • Online analysis tools will be provided… • Correlations with surface Cosmic Ray Detectors deployed in schools worldwide is possible… • CERN@School • TimePix kits are being provided for laboratory use. ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  26. Medipix3 is Coming • Even more Rad-Hard! • Dual Circuit Capability in EACH Pixel. • Either and ADC and a TDC simultaneously in each pixel… • Or, two ADCs with sequential use for 0 dead-time (< 100 ns) • Or, two ADCs with different Pre-Amp scales or responses… • Linear and Log Pre-Amps Possible… • Eliminate Saturation Effects • Smaller Pixel Sizes Possible • 256 x 256 - 55mm  512 x 512 - 25 mm • Lower Noise • On-Chip Output Clustering & Charge Centering • On Chip charge-sharing for sub-pixel position resolution ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  27. ATLAS Area Neutron MonitorsDetectorConfiguration (IEAP-Prague) Medipix2 ASIC with 300µm Si sensor + USB interface Neutron conversion structures: LiF+50µm Al foil area 100µm Al foil area PE area PE+50µm Al foil area Uncovered area X-ray image of conversion layers LiF PE PE + Al Al Uncovered ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  28. Courtesy of Jan Jakubek & Zdenek Vykydal Neutron Efficiency Calibration X-ray image of conversion layers Thermal neutrons – 500s, 25meV PE / PE+Al cluster count ratio: 252Cf: 10.70 ± 0.04 AmBe: 5.18 ± 0.03 VDG: 2.51 ± 0.03 252Cf – 2000s, 2MeV (mean) AmBe – 2000s, 4MeV (mean) Van de Graaff – 1000s, 14MeV LiF PE PE + Al Al Uncovered Calibrated efficiency: Thermal: 1.41E-2 ± 7.11E-4 cm-2s-1 252Cf: 1.19E-3 ± 1.89E-5 cm-2s-1 AmBe: 2.86E-3 ± 5.46E-5 cm-2s-1 VDG: 7.23E-3 ± 5.81E-4 cm-2s-1 ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  29. Thank You for Your Attention ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  30. Backup Slides Daya Bay Application (4) Electron Measurements (1) Drift Cloud Structure (1) Using the Timepix Mode for Fission Fragments (3) The “Volcano Effect” (4) Solder Bumps (High Magnification) (1) Timepix Mode Schematic (1) 60 Degree Fe Tracks (1) ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  31. Background Radiation @ Daya Bay(An Underground Neutrino Oscillation Experiment Being Constructed Near Hong Kong This is an Integral of the sum of all pixels for the May 20, 2010 Hall 5 run: (83280 sec = 23.13 hours) The heavily ionizing tracks are from Radon-Chain Alphas… The plot has a high relative threshold to suppress the MIPs The Pattern Recognition analysis takes into account the shape and energy per pixel as well as the integral energy in the total track cluster… ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  32. 3 Prevalent Event Types in Daya Bay Hall 5 Penetrating Muon Total Cluster Energy < 120 Raw Counts (angle dependent) Alpha (Radon Chain) Total Cluster Energy > 1000 Raw Counts Electron (g Compton) ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  33. Hall 5 – May 20 – 23 hour Pixel Sum ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  34. Radon These atoms are typically left in an ionized state, and quickly adhere to the nearest surface or dust particle • Radon is produced in the 238U decay chain: • …226Ra (1602 y 4.87 MeV a) 222Rn (3.8d 5.59 MeV a)  • 218Po (3.1m 6.12 MeV a)  • 214Pb (26.8m 1.02 MeV b)  • 214Bi (19.9m 3.27 MeV b)  • 214Po (0.16ms 7.88 MeV a)  • 210Pb… • Summary5.59 + 6.12 + 7.88 MeV = 19.59 MeV a • ✚ 1.02 + 3.27 MeV = 4.29 MeV b • “Normal” Radon Backgrounds… • The sea-level atmosphere contains on the average of 150 222Rn atoms/ml. This causes ~100 Bq/m3 indoors, and ~10-20 Bq/m3 outdoors, with health limits ~ 230 Bq/m3 • 1 pCi/l = 37 Bq/m3 (1 Bq = 1 decay/s) • Given the ranges of a’s in air, the Medipix device in open air samples a volume of about 8-12 cm3 or ~ 10-5 m3 ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  35. 23 MeV e- Measurements @ IACwith the TimePix v. FLUKA FLUKA e- Primary e- All Clusters KeV ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  36. Charge Drift Cloud Image (241Am 5.5 MeV a) • Time of Arrival image from a 5.5 MeV a from an 241Am decay. • Common global threshold can be adjusted to get time (i.e. charge) contours through the drift cloud… • (Single Event) ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  37. Nuclear Fission MeasurementsUsing TimePix (TDC) Mode Radioactive fragments from 239Pu selected by mass separator LOHENGRIN (Grenoble) and deposited onto the Timepix surface. Reactor (ILL) Separator: E, B Fragments Neutrons Timepix Courtesy of Jan Jakubek Target ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  38. Test with 8He • Decay is slow => Timepix clock set to 2.5 kHz • To suppress the initial cluster from ion the delay of 25 us inserted 8He n b 120 ms b 810 ms a < ns delay 25 us 120+810 ms 120 ms 8He Trigger b b+a Courtesy of Jan Jakubek ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  39. Measured events: 8He decays (TDC Mode) Primary ion 2ndbeta decay 1st beta decay Alpha decay The other decay mode Courtesy of Jan Jakubek ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  40. The “Volcano” Effect • We see a dip in response for the highest charge deposition rates… • This may be due to detector saturation effects… • …Or to a plasma effect that causes high recombination rates… • So far we see this only in the Fe tracks… ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  41. Close Up of the “Partial” Event • The right-hand event is a “normal” iron event, which does show a clear “Volcano” Effect. The scale is so high that the d-rays are not visible. • The left-hand event is a “Partial-Event.” One that was partially cutoff by the “Shutter.” • Because the central hole essentially goes to zero, it would appear that this event occurred at the end of the Shutter window and was only the early part of the drift image… ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  42. 56Fe @ 500 MeV/A ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  43. Fe “Volcano” Event ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  44. Bumps on the readout side – close up ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  45. Timepix (“TDC”) Mode (P0=1,P1=1) open close “Shutter” Stop 17 164 Clock Start Discriminator Output Analog Signals 10MHz 100MHz ISSRMP - Shanghai - L. Pinsky - 6/2/2011

  46. 56Fe 60 degree Runs… ISSRMP - Shanghai - L. Pinsky - 6/2/2011

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