SCINTILLATION FIBER DETECTOR FOR DOSE VERIFICATION IN PROTON THERAPY

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1 SCINTILLATION FIBER DETECTOR FOR DOSE VERIFICATION IN PROTON THERAPY Suhyun Lee Nuclear Physics Lab. Korea University

2 CONTENTS Introduction Detector - Scintillation-fiber array - Electronics Beam Test Result Summary & Future Feb.. 1

by using multi-layered Real%dE/dz% absorber by%beam - Obtain Birks parameter kb and Quantify scintillator s

3 INTRODUCTION Motivation: - Development of dose verification detector for the therapeutic hadron beam (ex. several hundred MeV proton) Goal: - Two-dimensional beam measurement and fast response - Check the Bragg peak by using multi-layered Real%dE/dz% absorber by%beam - Obtain Birks parameter kb and Quantify scintillator s quenching effect by comparing MC (GEANT4) result and data Quenching) effect MC% (de/dz) data% (dl/dz) kb Feb.. 1 3

4 DETECTOR Two-dimensional array with channels ( array) double-clad scintillation fiber (Bicron BCF-6) mm, square-shaped - Light emission peak at 53 nm (green) - Small radiation-induced degradation ESR The array was designed for the physical match to the readout photodiodes Feb.. 1 4

efficiency at 53 nm: ~ 6 % Adjustable gain mode and charge-integration time Graphic

5 DETECTOR units of charge-integration mode DAQ Readout by using Si-Photodiodes (Hamamatsu S ) - 4 pieces of 18 channel diodes for a unit of DAQ - Quantum efficiency at 53 nm: ~ 6 % Adjustable gain mode and charge-integration time Graphic user interface Designed for the typical therapeutic hadron beam (~ MeV,.1 ~ 1 na) Feb.. 1 5

6 DAQ CHARACTERISTICS Common ground Power supply Multi-layered DAQ - Total 5 18 channels - USB. based communication - Data transport - Remote control Photodioes USB port no dead time btw points DAQ specification - Data acquisition in second (s) unit: 5 points/s - Data recorded in Binary codes conversion to the ASCII codes is possible - Dynamic range: 3.5 and 1.75 pc for high/low gain corresponding MAX. ADC: 18 (6,144) - Integration time:.1 ms for 1 point - Elapsed time for the 1 point measurement: 4 ms point point point point point 1 point (.5 ms 8): mean of 8 sampled data sample sample sample sample sample sample sample sample 1 sample ((.1 +.4)ms) t I processing time Feb.. 1 6

7 BEAM TEST Beam test by using MC5 cyclotron at KIRAMS (Feb. 1, 1) 45 MeV proton beam with several different beam current (.5, 1, and 1.5 na) Distance from beam exit to surface of Sc-fiber array: cm Calibration by using own spread-out beam Feb.. 1 7

8 BEAM TEST Absorber! Detect layer #1! Detect layer #! y-detector! x-detector! y-detector! x-detector!. g cm -.7 g cm g cm g cm g cm g cm g cm - Depth measured by y- detector #1 :.4447,.5637,.687,.817,.97, g cm - beam Depth measured by x- detector #1 :.6856,.8156,.956, , , g cm - Air gap ~ 6. cm! =.73 ~.7 g cm -! Air gap ~ 3. cm! =.386 ~.4 g cm -! Depth measured by y- detector # : 1.334, 1.453, 1.57, 1.691, 1.81, 1.99 g cm - Seven steps: ~ 6 mm thick PMMM! Depth measured by x- detector # : , , , 1.944,.3944, g cm - Total 4 set of beam data was obtained by using multi-layered absorber 5 time bins (1 s) per a set of data absorber : multi-layered PMMA plate ρ = ±.85 (g/cm 3 ) Feb.. 1 8

9 RESULT ADC cell /g) /g) de/dz (MeV cm dl/dz (cm Simulated data Responses (corrected) depth (g/cm ) The spatial responses of the detector measured at different absorber depths (z) Scintillation responses of the detector and the specific energy losses as a function of the depth in the absorber Feb.. 1 9

10 RESULT /g) de/dz (MeV cm 5 4 Simulated data Experimental data depth (g/cm ) Obtained S & kb from the fit processes - kb :.1596 beam fluctuation Feb.. 1 1

11 RESULT dl/de) -1 QE(R)=S 1.8 dl dz Hcm êgl Quenching factor (Cal. ) Quenching factor (Exp.) depth (g/cm ) de dz HMeV cm êgl Measured quenching factors and the fitted data obtained by using the kb value We got the relation between ADC counts and specific energy losses Feb

12 RESULT Absorber:3mm[Layer ] A.U dimensional beam verification from x and y detector 1 1 Cell(Y) Cell(X) Quenching factor is not applied to beam verification yet Feb.. 1 1

SUMMARY A detector for time-dependent dose verification was developed successfully - Detector characteristics: - D scintillation fiber array +

5 na): - Measured energy deposition in fiber array with 4 steps of absorber thickness Result: - Checked beam information by time - Checked Bragg

13 SUMMARY A detector for time-dependent dose verification was developed successfully - Detector characteristics: - D scintillation fiber array + charge-integration mode electronics - Beam test at KIRAMS (proton, 45 MeV, 1.5 na): - Measured energy deposition in fiber array with 4 steps of absorber thickness Result: - Checked beam information by time - Checked Bragg peak - 1st - order Birks kb parameter Obtained - Quantified scintillator s quenching effect by comparing MC and data Future - DAQ development is ongoing - Requires precise therapeutic beam for the test (MeV proton beam) Feb

14 THANK YOU!!

15 BACK UP

16 PEDESTAL LEVELS Pedestal[X ] 1 Pedestal[X ] ADC 1 ADC Pedestal[Y ] Cell Pedestal[Y ] Cell ADC 1 ADC Cell Cell Feb

17 CALIBRATION ADC 8 Calibration[X ] 1 ADC 9 Calibration[Y ] ADC Cell 3 1 Calibration[Y ] Cell Calibration factors - binned likelihood fit - - some of the factors may be incorrect Cell Feb

18 NORMALIZATION /g) /g) de/dz (MeV cm dl/dz (cm Simulated data Responses depth (g/cm ) /g) /g) de/dz (MeV cm dl/dz (cm Simulated data Responses (corrected) depth (g/cm ) Y1 : 1 X1 : Y : X : Feb

19 BIRK S COEFFICIENT Parameter space - S & kb S :.9588 kb :.1596 Feb

20 PHOTODIODE ARRAY Hamamatsu S ch photodiode array - ((.1 +.7).8) mm (square-shaped) for a pixel - Two possible voltage offset (High & Low gain) Feb.. 1

21 PHOTODIODE ARRAY Feb.. 1 1

22 DAQ CHARACTERISTICS Multi-layered (5 array per board) DAQ - Total 5 18 channels - USB. based communication - Don t use cable longer than 3 m length! - Reomte control required for the experiment Common ground Photodioes DAQ specification - Data acquisition in second (s) unit: 5 points/s - Data recorded in Binary codes conversion to the ASCII codes is possible - Dynamic range: 3.5 and 1.75 pc for high / low gain corresponding MAX. ADC: 18 (6,144) - Integration time:.1 ms for 1 point - Elapsed time for the 1 point measurement: 4 ms Power supply USB port Feb.. 1

23 DETECTOR point point point point point no dead time btw points 1 point (.5 ms 8): mean of 8 sampled data sample sample sample sample sample sample sample sample 1 sample ((.1 +.4)ms) t I processing time ADC charge relation: - ID = Q/tI = (ADC / 6,144) DR/tI where - ID = Measured current - Q = Accumulated charge during integration time (ti) - DR = Dynamic range (3.5 and 1.75 pc) - ti = Integration time (.1 ms for 1 point) # of points / # of array / # of ch (cell) / data!! 16/ 1 (1 st for x DAQ) / 18 (Max. ch) / 5,763! Feb.. 1 3! / 6 (1 st for y DAQ) / 18 (Max. ch) / 6,75!

24 ENERGY LOSS Feb.. 1 4

Recent Development and Study of Silicon Solid State Photomultiplier (MRS Avalanche Photodetector)

Recent Development and Study of Silicon Solid State Photomultiplier (MRS Avalanche Photodetector) Valeri Saveliev University of Obninsk, Russia Vienna Conference on Instrumentation Vienna, 20 February