A%20Silicon%20Telescope%20For%20Nanodosimetry

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A Silicon Telescope For Nanodosimetry
Santa Cruz Institute for Particle Physics, UC
Santa Cruz in collaboration with the Department
of Radiation Medicine at Loma Linda University
Medical Center
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Nanodosimetry for Biomedical Applications -
Collaborators

• Loma Linda University Medical Center
• Reinhard Schulte George Coutrakon
• Vladimir Bashkirov Peter Koss
• Weizmann Institute of Science
• Amos Breskin Guy Garty
• Rachel Chechik Itzhak Orion
• Sergei Shchemelinin
• University of California, San Diego
• John F. Ward Jamie Milligan
• Joe Aguilera
• Santa Cruz Institute for Particle Physics
• (University Of California, Santa Cruz)
• Abe Seiden Wilko Kroeger
• Hartmut Sadrozinski Patrick Spradlin
• Robert P Johnson Brian Keeney

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Radiation Damage To DNA
Ionization event (formation of water radicals)
Light damage- reparable
Primary particle track
delta rays
e-
OH
Water radicals attack the DNA
Clustered damage- irreparable
The mean diffusion distance of OH radicals before
they react is only 2-3 nm
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Bethe-Bloch in ND
Linear Energy Transfer LET Radiation
damage in DNA occurs within 2-3nm
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Expanding the DNA
1nm solid
1 mm _at_ .001 atm.
1 m _at_ 1 atm.
X 1000
X 1000
Propane gas
DNA
Low pressure propane gas
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Nanodosimetry in Low-Pressure Propane
1 SSD is 0.4 Xo or 120keV LET at high energy
4 Silicon Detectors give position and LET, allow
trigger on any combination of planes
Eweak
electron
Incoming Proton
Low Pressure Gas
X-Y
Y-X
Vacuum
Ion
Estrong
Ion Counter
Aperture
NOT TO SCALE
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Integration of Silicon Modules and Nanodosimeter
VME CRATE
Localization of Protons 2 Silicon Strip Detector
(SSD) Modules
SSD Readout
PC W/ DAQ PCI Card
Ion Counter
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Time-Over-Threshold (TOT) Digitization of
Position and Energy with large Dynamic Range
TOT ? charge ? LET!
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TOT Spectrum - Effect of Charge Sharing in SMDs
13.5 GeV Spectrum
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TOT Spectra For Protons of Different Energies-An
absolute calibration of SSD
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Results
Proton energy MeV Mean TOT us RMS TOT us Charge Deposition 400um Si by Bethe-Bloch fC TOT expected us
13,500 7 1.4 5.3 6.5
250 12.3 2.6 13.5 13.7
39 53.4 6.4 54 55
27 70.4 7.5 67.5 69
24 78.3 8.5 76.5 78
22 84.4 9.8 81 82
17.6 105 11.5 99 101
9.5 108 15 189 105
7.4 109 21 243 105
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TOT and Resolution Measured TOT expected
through Bethe-Bloch

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Resolution
Energy Resolution LET Resolution /Slope of
TOT(E) Curve
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Conclusion

1. Silicon detectors provide information on position
   and energy or LET of primary particles for
   nanodosimetry
2. Silicon detectors have excellent spatial
   resolution (60 mm)
3. We can measure proton LET to 10-20 in each of 4
   planes
4. Given LET, we know energy to 20-25 in each plane
   through Bethe-Bloch from low energies up to 250
   MeV
5. Silicon Detectors allow flexible triggering on
   primary particles.