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

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Preparing For a Medipix-Based Dosimeter Demonstration on the

International Space Station

Lawrence PinskyLawrence Pinsky

Physics DepartmentPhysics Department

University of HoustonUniversity of Houston

ISSRMP - Shanghai - L. Pinsky - 6/2/2011

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

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Hybrid Pixel Detector Hybrid Pixel Detector

Detector and electronics readout are optimized separately


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Hybrid Pixel Detector - Cross SectionHybrid Pixel Detector - Cross Section

UH is currently working on epitaxial deposition techniques thatUH is currently working on epitaxial deposition techniques thatwill facilitate the creation of high efficiency Embedded-Neutron-Converter detectorswill facilitate the creation of high efficiency Embedded-Neutron-Converter detectors


65,536 Bump-Bonds on each unit…65,536 Bump-Bonds on each unit…

5ISSRMP - Shanghai - L. Pinsky - 6/2/2011

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• 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

TimePix Cell SchematicTimePix Cell Schematic


TimePix Threshold CalibrationTimePix Threshold Calibration

Calibrates the 4-bit (16 level) Threshold Offsets for each Calibrates the 4-bit (16 level) Threshold Offsets for each pixel. The RED histogram is the distribution of noise turn-on pixel. The RED histogram is the distribution of noise turn-on points with all bits set to high. The BLUE histogram is the points with all bits set to high. The BLUE histogram is the corresponding low setting. The BLACK histogram is the corresponding low setting. The BLACK histogram is the corrected result. Each channel is ~20 ecorrected result. Each channel is ~20 e--……


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Time-Over-Threshold (Time-Over-Threshold (““ADCADC””) Mode ) Mode (P0=1,P1=0)(P0=1,P1=0)

33 50 12

10MHz Clock10MHz Clock 100MHz Clock100MHz Clock

2Ke- 4Ke- 2Ke-

“Shutter” Window

Analog Signals

Threshold

Discriminator Output

Clock Out


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Energy

TO

TTimePix and its TOT modeTimePix and its TOT mode

If the pulse shape is triangular then If the pulse shape is triangular then Time over Threshold is proportional to Time over Threshold is proportional to collected charge i.e. to energy.collected charge i.e. to energy.

Due to limited bandwidth the pulse can Due to limited bandwidth the pulse can be NEVER perfectly triangular.be NEVER perfectly triangular.

Non-linear TOT to energy dependenceNon-linear TOT to energy dependence

Threshold

Time

En

erg

y

Calibrationcurve

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.


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Charge ClustersCharge Clusters

TimePix

IncidentParticle

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.

“PIXELMAN”Image


Dosimetry in SpaceDosimetry in Space

Our approach is to try and Our approach is to try and Characterize the Radiation Field Characterize the Radiation Field as as precisely as possible as a function of time.precisely as possible as a function of time.

To do that, we need to assess the radiation environment in terms To do that, we need to assess the radiation environment in terms of the of the ChargeCharge AND AND EnergyEnergy of the individual particles that are of the individual particles that are present.present.

……HOWEVER, because of the HOWEVER, because of the ““ZZ22 effect effect”” and the shape of the and the shape of the energy-loss curves, it is possible for different ions to have the energy-loss curves, it is possible for different ions to have the same dE/dx in a thin detector…same dE/dx in a thin detector…

Slow lower-Z particles seen in the dosimeter will not penetrate Slow lower-Z particles seen in the dosimeter will not penetrate deeply into the body, and can be mimicked by higher-Z faster deeply into the body, and can be mimicked by higher-Z faster particles, which CAN penetrate deeply…particles, which CAN penetrate deeply…

SO, again, SO, again, ““Our approach is to try and Our approach is to try and Characterize the Radiation Characterize the Radiation Field Field as precisely as possible as a function of time.as precisely as possible as a function of time.””

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Measuring Charge AND EnergyMeasuring Charge AND Energy If you know If you know then measuring then measuring

the charge is reasonably the charge is reasonably simple because of the Zsimple because of the Z22 dependence.dependence.

In accelerator experiments In accelerator experiments the interaction fragments the interaction fragments from the projectile particle is from the projectile particle is generally moving at close to generally moving at close to the projectilethe projectile’’s original s original velocity, at least for forward velocity, at least for forward fragments.fragments.

However, if you have no However, if you have no a a prioripriori velocity information, the velocity information, the problem is the problem is the BETHE-BLOCH BETHE-BLOCH EquationEquation… (One can observe … (One can observe the behavior over a longer the behavior over a longer distance, or look for distance, or look for track track structure differencesstructure differences…)…)

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All charge-1 particles.Higher charge particles are raised by the square of the charge at the same momenta


Also, dE/dx ≠ LETAlso, dE/dx ≠ LET(High Energy (High Energy -Rays)-Rays)

Because the number of Because the number of -rays -rays produced per unit track length produced per unit track length in the Air prior to entering the in the Air prior to entering the Si is much less than in the the Si is much less than in the the Si…Si…

……The highest energy The highest energy -rays -rays carry away more energy from carry away more energy from the Si than enters from the air.the Si than enters from the air.

HOWEVER—It is the High HOWEVER—It is the High Energy Energy -rays that offer the -rays that offer the prospect of telling the prospect of telling the difference between the difference between the different particle velocities different particle velocities with the same dE/dx…with the same dE/dx…

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TimePix

-RaysAir

IncidentParticle

SiSi


FLUKA Medipix (TimePix)Heavy Ion FLUKA Medipix (TimePix)Heavy Ion SimulationsSimulations

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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 SaturationSaturation effects are common…



TimePix in the HIMAC BeamsTimePix in the HIMAC Beams Data have been taken at Data have been taken at

HIMAC in some dedicated HIMAC in some dedicated and many parasitic runs…and many parasitic runs…

Runs at a range of Runs at a range of incident angles and with incident angles and with different detector settings different detector settings are typically taken…are typically taken…

The primary beams were The primary beams were (MeV/A):(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

Examples of Individual (Normal Incidence) Examples of Individual (Normal Incidence) ““TracksTracks””

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100 MeV/A O

800 MeV/A Si

600 MeV/A Si180 MeV/A Ne

The high energy -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…


800 MeV/A Si 85 degree Tracks800 MeV/A Si 85 degree Tracks

The tracks are from The tracks are from particles diving particles diving downward from left to downward from left to right.right.

As they pass though As they pass though the solder-bumps and the solder-bumps and into the underlying chip into the underlying chip after leaving the Si after leaving the Si detector layer.detector layer.

Some of the high Some of the high energy energy -rays from the -rays from the chip enter the overlying chip enter the overlying detector layer… detector layer…


1616O @ 100 MeV/A—0° & 60° Averaged Cluster ShapesO @ 100 MeV/A—0° & 60° Averaged Cluster Shapes (Azimuthal & Polar Angle resolution ~ 1 Degree)(Azimuthal & Polar Angle resolution ~ 1 Degree)

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0° 60°


TimePix as an in- Flight TimePix as an in- Flight DosimeterDosimeter

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84°N Latitude ~ 180 ° Longitude@ Local Midnight

at 35,000 ft

Australia

100 Sec Integrated ImageThe Dose RATE is ~ 50 times The Dose RATE is ~ 50 times the surface background rate the surface background rate (in Houston) w/o Neutron Corr.(in Houston) w/o Neutron Corr.ISSRMP - Shanghai - L. Pinsky - 6/2/2011

M.D. Anderson Proton Therapy M.D. Anderson Proton Therapy Center Scanning Beam FrameCenter Scanning Beam Frame

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This 10 s 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…


NASA NASA HyPRDHyPRD——SDTOSDTOHyHybrid brid PPixel ixel RRadiation adiation DDosimeter—osimeter—

SStation tation DDemonstration emonstration TTest est OObjectivebjective At the request of SRAG, We are At the request of SRAG, We are

currently preparing to fly currently preparing to fly several Timepix-based USB several Timepix-based USB interfaced units (HyPRD’s) as interfaced units (HyPRD’s) as an SDTO on the ISS possibly an SDTO on the ISS possibly later this year…later this year…

The SDTO units are the size The SDTO units are the size and weight of a typical and weight of a typical “Memory Stick” Flash Drive.“Memory Stick” Flash Drive.

There is also a Phase I SBIR There is also a Phase I SBIR that is producing a prototype that is producing a prototype stand-alone interface (stand-alone interface (Battery-Battery-Powered, Wireless, with local Powered, Wireless, with local Analysis Capability and Analysis Capability and Readout with AlarmsReadout with Alarms)—Phase II )—Phase II will hopefully begin this Fallwill hopefully begin this Fall


Earlier Medipix2 USB Interface

First ISS Flight Unit Prototype

SDTO ISS Flight SDTO ISS Flight SoftwareSoftware(Via USB (Via USB Interface)Interface)


The flight software will run on the existing ISS Lenovo laptops attached The flight software will run on the existing ISS Lenovo laptops attached to the HyPRD unit the via a standard to the HyPRD unit the via a standard USB Type-A connectorUSB Type-A connector

It will have It will have automatic frameautomatic frame--lengthlength and and raterate adjustment adjustment capability…… It will display It will display cumulative (dose)cumulative (dose) and and currentcurrent ( (dose-ratesdose-rates) ) [[NCRP-NCRP-

153153] ] Dose-EquivalentDose-Equivalent locally on the laptop. locally on the laptop. Full data frames will be downloaded to the ground for analysis in a Full data frames will be downloaded to the ground for analysis in a

Root-based software environmentRoot-based software environment……

HyPRD Hardware Processing at CERNHyPRD Hardware Processing at CERN


HyPRD

Wire-bonds

LUCIDLUCID – – LLangtonangton UUltimate ltimate CCosmic ray osmic ray IIntensity ntensity DDetectoretectorTimePixTimePix’’s First Space Mission—Educational Outreachs First Space Mission—Educational Outreach

(UK Satellite to be Launched Q1—2012)(UK Satellite to be Launched Q1—2012)

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Velocity

Down

5 TimePix Detectors (0.7 mm Al dome)5 TimePix Detectors (0.7 mm Al dome) Sun-Synchronous Polar Orbit (98° @ 11:00)Sun-Synchronous Polar Orbit (98° @ 11:00) Programmable Signal Processor forProgrammable Signal Processor for

on-orbit data analysis…on-orbit data analysis…

1.4 cm


LUCIDLUCID Educational OutreachEducational 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@SchoolCERN@School TimePix kits are being

provided for laboratory use.


Medipix3 is ComingMedipix3 is Coming

Even more Rad-Hard!Even more Rad-Hard! Dual Circuit Capability in EACH Pixel.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…Linear and Log Pre-Amps Possible… Eliminate Saturation Effects

Smaller Pixel Sizes PossibleSmaller Pixel Sizes Possible 256 x 256 - 55m 512 x 512 - 25 m

Lower NoiseLower Noise On-Chip Output Clustering & Charge CenteringOn-Chip Output Clustering & Charge Centering

On Chip charge-sharing for sub-pixel position resolution


ATLAS Area Neutron MonitorsATLAS Area Neutron MonitorsDetector Configuration (IEAP-Prague)Detector Configuration (IEAP-Prague)

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Medipix2 ASIC with 300µm Si sensor + USB interface

Neutron conversion structures:

1)LiF+50µm Al foil area

2)100µm Al foil area

3)PE area

4)PE+50µm Al foil area

5)Uncovered area

PE

PE + Al

Al

Uncovered

LiF

X-ray image of conversion layers

Neutron Efficiency CalibrationNeutron Efficiency Calibration

Calibrated efficiency:Calibrated efficiency:

Thermal: 1.41E-2 ± 7.11E-4 cmThermal: 1.41E-2 ± 7.11E-4 cm-2-2ss-1-1

252Cf: 1.19E-3 ± 1.89E-5 cm252Cf: 1.19E-3 ± 1.89E-5 cm-2-2ss-1-1

AmBe: 2.86E-3 ± 5.46E-5 cmAmBe: 2.86E-3 ± 5.46E-5 cm-2-2ss-1-1

VDG: 7.23E-3 ± 5.81E-4 cmVDG: 7.23E-3 ± 5.81E-4 cm-2-2ss-1-1


Thermal neutrons – 500s, 25meV

252Cf – 2000s, 2MeV (mean) AmBe – 2000s, 4MeV (mean)

PE

PE + Al

Al

Uncovered

LiF

X-ray image of conversion layers

Van de Graaff – 1000s, 14MeV

PE / PE+Al cluster count ratio:

252Cf: 10.70 ± 0.04

AmBe: 5.18 ± 0.03

VDG: 2.51 ± 0.03

Courtesy ofJan Jakubek& Zdenek Vykydal


Thank You for Your AttentionThank You for Your Attention

Backup SlidesBackup Slides

Daya Bay Application (4)Daya Bay Application (4) Electron Measurements (1)Electron Measurements (1) Drift Cloud Structure (1)Drift Cloud Structure (1) Using the Timepix Mode for Fission Fragments (3)Using the Timepix Mode for Fission Fragments (3) The “Volcano Effect” (4)The “Volcano Effect” (4) Solder Bumps (High Magnification) (1)Solder Bumps (High Magnification) (1) Timepix Mode Schematic (1)Timepix Mode Schematic (1) 60 Degree Fe Tracks (1)60 Degree Fe Tracks (1)


Background Radiation @ Daya Bay(An Background Radiation @ Daya Bay(An Underground Neutrino Oscillation Experiment Underground Neutrino Oscillation Experiment

Being Constructed Near Hong KongBeing Constructed Near Hong Kong

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This is an Integral of the sum of all pixels for the May 20, 2010 Hall 5 run:(83280 sec = 23.13 hours23.13 hours)

The Pattern Recognition analysis takes into account the shape and energy per pixel as well as the integral energy in the total track cluster…

The plot has a high relative threshold to suppress the MIPs

The heavily ionizing The heavily ionizing tracks are from Radon-tracks are from Radon-Chain Alphas…Chain Alphas…


3 Prevalent Event Types in Daya Bay Hall 53 Prevalent Event Types in Daya Bay Hall 5

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Penetrating Muon Total Cluster Energy< 120 Raw Counts (angle dependent)

Electron ( Compton)

Alpha (Radon Chain)Total Cluster Energy> 1000 Raw Counts


Hall 5 – May 20 – 23 hour Pixel SumHall 5 – May 20 – 23 hour Pixel Sum


RadonRadon

Radon is produced in the Radon is produced in the 238238UU decay chain: decay chain: …226Ra (1602 y 4.87 MeV ) 222Rn (3.8d 5.59 MeV ) 218Po (3.1m 6.12 MeV ) 214Pb (26.8m 1.02 MeV ) 214Bi (19.9m 3.27 MeV ) 214Po (0.16ms 7.88 MeV ) 210Pb… SummarySummary 5.59 + 6.12 + 7.88 MeV = 19.5919.59 MeV ✚ 1.02 + 3.27 MeV = 4.294.29 MeV

““NormalNormal”” Radon Backgrounds… 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 ’s in air, the Medipix device in open

air samples a volume of about 8-12 cm3 or ~ 10-5 m3


These atoms are typically left in an ionized state, and quickly adhere to the nearest surface or dust particle

23 MeV e23 MeV e-- Measurements @ IAC Measurements @ IACwith the TimePix v. FLUKAwith the TimePix v. FLUKA


All Clusters

Primary ePrimary e--

FLUKA e-

KeV

Charge Drift Cloud Image (Charge Drift Cloud Image (241241Am 5.5 MeV Am 5.5 MeV ))

Time of Arrival Time of Arrival image from a image from a 5.5 MeV 5.5 MeV from from an an 241241Am decay.Am decay.

Common global Common global threshold can threshold can be adjusted to be adjusted to get time (i.e. get time (i.e. charge) charge) contours contours through the drift through the drift cloud…cloud…

(Single Event)(Single Event)


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Nuclear Fission MeasurementsNuclear Fission MeasurementsUsing TimePix (TDC) ModeUsing TimePix (TDC) Mode

Radioactive fragments from 239Pu selected by mass separator LOHENGRIN (Grenoble) and deposited onto the Timepix surface.

Fragments

Separator: E, B

Neutrons

Tim

epix

Reactor (ILL)

Target

Courtesy ofJan Jakubek


38Courtesy ofJan Jakubek

Test with Test with 88HeHe8He

n120 ms

810 ms

< ns

1. Decay is slow => Timepix clock set to 2.5 kHz

2. To suppress the initial cluster from ion the delay of 25 us inserted

120 ms

120+810 ms

delay 25 us

8He

Tri

gg

er


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Courtesy ofJan Jakubek

Measured events: Measured events: 88He decays (TDC Mode)He decays (TDC Mode)

Alpha decay

2ndbeta decay

1st beta decay

Primary ion

The other decay mode


The The ““VolcanoVolcano”” Effect Effect

We see a dip in We see a dip in response for the response for the highest charge highest charge deposition rates…deposition rates…

This may be due to This may be due to detector saturation detector saturation effects…effects…

……Or to a plasma Or to a plasma effect that causes effect that causes high recombination high recombination rates…rates…

So far we see this So far we see this only in the Fe tracks…only in the Fe tracks…


Close Up of the Close Up of the ““PartialPartial”” Event Event

The right-hand event is a The right-hand event is a ““normalnormal”” iron event, which iron event, which does show a clear does show a clear ““VolcanoVolcano”” Effect. The scale is so high Effect. The scale is so high that the that the -rays are not visible.-rays are not visible.

The left-hand event is a The left-hand event is a ““Partial-Event.Partial-Event.”” One that was One that was partially cutoff by the partially cutoff by the ““Shutter.Shutter.””

Because the central hole Because the central hole essentially goes to zero, it essentially goes to zero, it would appear that this event would appear that this event occurred at the end of the occurred at the end of the Shutter window and was only Shutter window and was only the early part of the drift the early part of the drift image…image…


5656Fe @ 500 MeV/AFe @ 500 MeV/A


Fe Fe ““VolcanoVolcano”” Event Event



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Bumps on the readout side – close upBumps on the readout side – close up

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Timepix (Timepix (““TDCTDC””) Mode ) Mode (P0=1,P1=1)(P0=1,P1=1)

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10MHz10MHz 100MHz100MHz

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“Shutter”

open close

Analog Signals

Discriminator Output

Clock StartStop


5656Fe 60 degree Runs…Fe 60 degree Runs…

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Cluster volume distribution

Co

un

t

Volume [keV]

Vol AllVol OK

1.2e+0051e+005800006000040000200000

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10

8

6

4

2

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

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