Overview of TEPC for high LET Radiation Monitoring in Complex Radiation Field

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Stewart Curtis
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Institute Chang Hwy Lim, Myungkook Moon Korea

1 Overview of TEPC for high LET Radiation Monitoring in Complex Radiation Field Uk-Won Nam, Jae Jin Lee, Jeonghyun Pyo, Bong-Kon Moon, Dae-Hee Lee, Youngsik Park Korea Astronomy and Space Science Institute Chang Hwy Lim, Myungkook Moon Korea Atomic Energy Research Institute Sunghwan Kim Cheongju University

2 Outline Introduction Characteristics of portable TEPC Calibration of portable TEPC Summary and Future Works

3 Introduction Background NASA proposed radiation monitoring in ISS as a NASA-Korean government cooperation program in KASI (Korea Astronomy Space and Science Institute) has been funded for developing a spherical type TEPC since Our goal Development and characterization of a portable TEPC which could monitor the radiation in ISS Requirements Measurable LET range: kev/um Mass: < 5kg Volume : < 6000 cm 3

4 Tissue Equivalent Proportional Counter Specification Measurable range: kev/um Detector wall A-150 sphere inner diameter : 30 mm Thickness : 5.0 mm TE Gas 55% C3H8, % CO % N2 Gas Pressure : 27.7 torr Site diameter : 2 µm Detector Housing SUS304 Housing diameter : 70 mm Thickness : 1.0 mm

5 TEPC chamber

6 Portable TEPC Volume : 2,624 cm 3 Weight : 1.8Kg

7 Charge Sensitive Pre amp.

8 Main Electronics Design High HIGH VOLTAGE Voltage DIGITAL PROCESSING BOARD Digital Processing DISP HV HV ADJ. HV MON +12V +6V GND -6V DISP_INTF 1553B_INTF 1553B D5V GND TEPC HV +6V GND -6V SIGNAL TEST PULSE GND TEMP c TEMP B TEMP E Analog Processing ANALOG PROCESSING AMPL IN P+6V PGND P-6V TEMP MON TEMP C TEMP B TEMP E TEST PULSER TP OUT POL COARSE FINE P/Z MON TEMP MON TP TRIG OSCILLOSCOPE OUT +6V GND -6V PULSE to DIGITAL CONV DPOL SPI_COARSE SPI_FINE SPI_PZ IN TEMP_MON TP_TRIG LLD ADJ. ULD ADJ. DAC_LLD DAC_ULD CONTROL SADC PEAK +6V GND -6V ADC_HV DAC_HV RS232 D+5V DGND DIGITAL PROCESSING DISP_INTF 1553B_INTF SADC#1 PEAK#1 SADC#2 PEAK#2 SADC#3 PEAK#3 SADC#4 PEAK#4 RS232#1 RS232#2 RS232#3 RS232#4 POWER +12V AGND -12V D5V DGND TCP/IP +28V GND D5V DGND

9 Electronic Board 9

10 Linearity of TEPC 1000 Y = X Data Curve Fitting 800 ADC channel TEST Input - Ramp Wave (mvpp)

11 Calibration of portable TEPC Channel calibration using alpha source Using Am MeV α source Range of Lineal Energy : 0.2 ~ 300 kev/μm Determine the calibration factor of TEPC using neutron source Using Cf-252 neutron source at KRISS Determine the calibration factor of the TEPC

12 (2) Channel Calibration of TEPC using 241 Am Microdosimetry Lineal Energy (y, kev/µm) = E / mean chord length(l) TEPC : mean chord length = 2d/3 Bias voltage : 950 V Peak channel of a particle 863 Satisfy measurement range : 0.2~300 kev/um Lineal Energy / MCA channel y E = Eα : LET of α particle in tissue equivalent material (86.5 kev/µm) I I Iα : Peak channel of α particle on MCA = Equation: y=y0 + (A/(w*sqrt(PI/2)))*exp(-2*((x-xc)/w)^2) y ±0.32 xc ±0.56 w ±1.26 A ±201.7 Peak (ch) Resolution of Channel (kev/um-ch) α α 3 2d kev / µ m ch Max. ch (kev/um) Counts Channel

13 Neutron Source at KRISS Cf-252 standard Neutron Source at KRISS (Korea Research Institute of Standards and Science) Neutron flux : cm -2 s -1 ( ) Dose rate : 53.9 msv/hr 50cm 6,00E+01 75cm 5,00E c m 4,00E+01 3,00E+01 2,00E+01 1,00E+01 0,00E+00 1,00E-09 1,00E-07 1,00E-05 1,00E-03 1,00E-01 1,00E+01

14 Calibration of TEPC using Cf-252 Process of Equivalent Dose Calibration

Neutron Beam Experiment using Cf-252 10 5 10 4 Counts 10 3 10 2

15 Neutron Beam Experiment using Cf Counts Channel Proton end point H k f = QD = k = h h max min f R = k QD f h h max min q( h) h n( h) dh q( h) h n( h) dh = µ Sv/R Measured Lineal Energy Spectrum of Cf-

16 Summary and Future Works The Engineering model of portable TEPC was designed and fabricated with A-150 ionization cavity, amplifier + preamp circuit, spectrometer, and HVPS. Portable TEPC have been characterized and calibrated by using Am-241 and Cf-252. We experimently confirmed that the TEPC was well operated below 100 kev/µm. Future Works Development of Qualification TEPC model Calibration in the range of high LET radiation in HIMAC We hope that the TEPC will Launch and dosimetry in ISS. More compact, lightweight and low power consumption for CubeSet application (TEPC + RadFET) Future Korean Lunar program (2020s) We are looking for more science applications

18 Proposed Missions of CubeSet Simulation of dose distribution after Solar Proton events ( ) using RBSP data Dose level is high between 1000 km and 3000km Space radiation dosage is rapidly increased near 1000 km Proposed Missions of CubeSet : Measurement of total dose & LET spectrum in orbit : Measurement of magnetic field of Earth 18

19 Thank you for your attention!

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