Adding Dose Equivalent Scoring for Heavy Ions in FLUKA

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 1

Adding Dose Equivalent Scoring Adding Dose Equivalent Scoring for Heavy Ions in FLUKAfor Heavy Ions in FLUKA

Toni Empl & Lawrence PinskyToni Empl & Lawrence Pinsky

University of HoustonUniversity of Houston

Current NASA Funding Status• We have a specific grant from NASA/JSC to add Dose Dose

Equivalent Scoring Equivalent Scoring into FLUKA (to support Toni through July). Kerry Lee and Neal Zapp continue to use FLUKA for operational calculations.

• NASA is interested in having an “AdvancedAdvanced” FLUKA FLUKA CourseCourse at some point in the not too distant future.

• No word yet on possible extensions to validate codes for Light Fragments…

• Funding to add a “Medipix (Si Charge Cluster) SimulationMedipix (Si Charge Cluster) Simulation” to FLUKA is pending…

• Tom Wilson has a proposal in to fund the use of FLUKA to model Lunar habitats and potential Lunar-based experiments

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 2

Dose Equivalent for Heavy Ions

• Much of the effort has been done for protons and can be directly implemented for Heavy ions (We will use the NCRP 132 Q Factors)…

• Scoring at an interface is less problematic than within a volume, (except for neutrals).

• Principal Issues:– Neutrons (Multi-Group—Kerma)…– Double counting energetic -rays…

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 3

Neutron Issues• When a (multi-group) neutron is propagating in a

medium the Kerma is normally scored and the neutron’s group is changed.

• Scoring Dose Equivalent properly, one should propagate the neutron in detail and account for the energy deposits via any produced charged particles from interactions, much like a .

• This is problematic at surfaces.• Proposed Solution: Update Kerma tables in

FLUKA to account for the Oxygen in Water, using a water equivalent scoring.

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 4

LET∞ Issues & Double Counting

• The NCRP definition of Dose Equivalent for Heavy Ions employs an LET∞–based formula.

• If one uses the actual Net Energy Lost by the particle over its track-length in a volume to be scored, and in addition propagates the long range -rays does one count the deposition from them in addition to the energy lost by the primary, both when the d-ray remains entirely within that volume, and when it leaves the volume for an neighboring volume to be separately scored?

• The same issue occurs for gamma’s produced.

• A biological argument would be to score both…

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 5

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 6

Recent Efforts in the Development Recent Efforts in the Development of a TimePix-Based Active of a TimePix-Based Active Dosimeter for Use in theDosimeter for Use in the

Space Radiation EnvironmentSpace Radiation Environment

Lawrence PinskyLawrence Pinsky

(& Others)(& Others)

University of HoustonUniversity of Houston

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 7

A Report on the TimePix @ HIMACIn February, 2009

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 8

HIMAC @ NIRS in Japan

• HIMAC - (Heavy Ion Medical Accelerator Center) @ NIRS (National Institute for Radiological Sciences) in Chiba, Japan.

• Primarily a Cancer Therapy Center, but they give us free beam time

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 9

HIMAC Layout

Some “Standard” HIMAC Beams

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 10

The Numbers in BLACK are the dE/dx values in Si, and the “*” are Non-Standard Beams.The Numbers in RED are the maximum kinematically allowed -Ray energies.

Measuring Charge AND Energy• If you know 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…

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 11

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

Same dE/dx, BUT, Different Z

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 12

Remember, these dE/dx values are from the Bethe-Bloch Equation!

dE/dx vs. Energy Deposited

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 13

800 MeV/A Si800 MeV/A Si

600 MeV/A Si600 MeV/A Si

100 MeV/A O100 MeV/A O

180 MeV/A Ne180 MeV/A Ne

High Energy -Rays• Because the number of -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 -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…

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 14

TimePix

-RaysAir

IncidentParticle

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 15

TimePix in the HIMAC Beams

• Data were taken in a parasitic mode with Fe @ 500 MeV/A, N @ 290 & 180 MeV/A and Si @ 400 MeV/A

• The primary beams were:– Si @ 600 & 800 MeV/A,

– Ne at 180 MeV/A and

– O @ 100 MeV/A,

– all at Incident angles of 0, 15, 30, 45, 60& 90

• …With a TimePix clock of 20 MHz, IKRUM’s of 3, and with a Bias Voltages of 35V

Examples of Individual Tracks

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 16

100 MeV/A O

800 MeV/A Si

800 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…

The “Volcano” (Plasma) Effect• When the ionization creates a

charge density that exceeds the doping density it can overwhelm them dielectric capability in the Si detector layer.

• When that happens the charges “see” each other, and recombination increases considerably…

• Also, when the track is parallel with respect to the bias field the recombination opportunity is a maximum. This can create a “hole” or dip in the center of the circular drift image, making the “lego-plot” look like a volcano…

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 17

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 -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…

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 18

• Another view of the Volcano Event…

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 19

The Next Steps…

• The Chip has now been calibrated and absolute analyses in KeV are being started…

• …And, we will also complete the measurement program at HIMAC…

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 20

Using the TimePix to Measure Interaction Cross Sections…

• There are many heavy ion interaction cross sections that will be needed to verify the existing event generators used to predict doses in astronauts will take on future space missions…

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 21

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 22

Pixelman Frames from11B @ ~90 From Last Year

Image of Time of Arrival of Charge at the Chip…

• We can examine the nature of the drift of the charge cloud by using the TDC capability of the TimePix…

• See separate ABCDView Plot…

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 23

FLUKA Meeting--INFN-Milan April 28, 2009 – L. Pinsky

Adding Dose Equivalent Scoring and Recent Efforts in the Development of a TimePix-Based Active Dosimeter 24

Thank You for Your Attention