PHITS calculation of the radiation field in HIMAC BIO Ondřej Ploc, Yukio Uchihori, Hisashi Kitamura, Lembit Sihver National Institute of Radiological Sciences, Chiba, Japan Nuclear Physics Institute, Prague, Czech Republic Chalmers University of Technology, Gothenburg, Sweden
Outline Introduction Beam-line description Depth-dose curves Beam profile Example of application Silicon detector calibration using only one heavy ion beam Fragments contribution LET spectra Conclusions 2
Introduction HIMAC - Heavy Ion Medical Accelerator in Chiba Three irradiation rooms for experiments: (i) General Physics, (ii) Biology (BIO), (iii) Medium energy http://www.nirs.go.jp/eng/research/charged_particle/index.shtml 3
Introduction HIMAC BIO is an irradiation room used for heavy ion experiments related to biology and physics Goals to provide detailed information about the components of the beam line at HIMAC BIO to express the exact beam composition via fragment contribution to absorbed dose calculated by PHITS at the location of irradiated samples To compare PHITS simulations with measurements using a semiconductor detector Liulin 4
HIMAC BIO Advantage: Bragg curve is well defined Broad parallel beam (φ 10cm) Flat beam profile Disadvantage: Fragments and secondary particles because beam goes through scatterer (different for different ions) and 6.7m of air Ion+nominal energy in MeV/u: He 150, C 135, C 290, C 400, Ne 400, Si 490, Fe 500 Measurements performed behind different thicknesses of PMMA filters 9 filters are available (in mm): 0.5, 1, 2, 4, 8, 16, 32, 64, 128 5
HIMAC BIO geometry used for PHITS calculations Synchrotron room 6
HIMAC BIO geometry used for PHITS calculations 7
HIMAC BIO geometry used for PHITS calculations Ring collimator Four leaf collimator (FLC) Al Range shifter Brass collimators Beam dump samples Wobbler magnets Beam profile monitor Beam exit Scatter filters 8
Beam exit HIMAC BIO, beam line Synchrotron room F-collimator Vacuum tube Ring collimator Vacuum tube 2 Main monitor + SEM Beam profile monitor Experimental room Four leaf collimator (FLC) Al Range shifter Brass collimators samples Wobbler magnets 1055 892 1172 Materials on the beam line Scatter filters 540 281 30.5 Dump Thickness / cm Water equivalent thickness / cm Air 668.8 0.8 Aluminum windows (11) 0.011 0.03 Scatter filters (Ta or Pb) Variable, depends on ion and energy Range shifter (PMMA) Variable 9
Scatter filters Scatter filters Ta Pb 1 2 3 4 5 6 7 8 Brass F-collimator φ out 16cm φ in 10cm Ion and energy / MeV/u Ta / mm Pb / mm Water eq. / mm He 150 mono 0.215 0 3.57 C 135 mono 0.215 0 3.57 C 290 mono 0.434 0 7.20 C 290 SOBP 0.649 0 10.77 C 400 mono 0.754 0 12.52 Ne 230 mono 0.539 0 8.95 Ne 400 mono 1.02 0 16.93 Si 490 mono 0.434 1.6 25.35 Fe 500 mono 0.215 1.6 21.72 Al holders 10
Scatter filters Configuration for Ne 400 MeV/u, all charged particles The density of energy distribution is visibly higher behind the scatter filters 11
Scatter filters Configuration for Ne 400 MeV/u, Oxygen ions only 12
Scatter filters Configuration for Ne 400 MeV/u, He only 13
Measured and calculated Bragg curves Measurement with Markus ionization chamber behind different thicknesses of PMMA filters absorbed dose / Gy 3.0E-04 2.5E-04 2.0E-04 1.5E-04 1.0E-04 5.0E-05 C290 mono PHITS calculation IC measurement Real energy(phits): 278.7 MeV/u 0.0E+00 0 20 40 60 80 100 120 140 Depth in PMMA [mm] Calculated Bragg curves fitted well to the measured ones => well designed geometry was confirmed 14
Range and beam energies in HIMAC BIO Ion Nominal energy / (MeV/u) Range in PMMA / cm Measured with IC Calculated with PHITS Beam energy in front of PMMA filters / (MeV/u) SRIM PHITS He 150 12.63 12.58 145.35 145.5 C 135 2.73 2.91 112.54 114.0 C 290 12.83 12.61 274.43 278.7 C 400 22.23 22.01 382.85 389.7 Ne 400 12.48 12.48 370.05 373.8 Si 490 11.88 11.77 445.68 447.0 Differences in range < 2 mm and in energies 2% 15
Beam profile Experiments: by Hisashi Kitamura 2003-2007 Markus ionization chamber He, C, Ne, Si, Ar, Fe, Kr, Xe Several energies, diameters, binary filters for each ion PHITS calculations: Scatterers as described above Wobbler magnets 2 dipole electromagnets to change the beam diameter in x and y axis Magnetic field intensity: 0.5 kg Radius of gap: 10cm 16
Beam profile 105% C 290 MeV/u 100% 95% 90% 85% IC PHITS 80% 75% -70-50 -30-10 10 30 50 70 x / mm PHITS simulation: transverse dose distribution at the front surface of water column 17
Liulin Energy deposition spectrometer Active volume: silicon diode (2 1 0.03 cm 3 ) Size: 98 65 25 mm 3 (MDU01&02) 103 103 47 mm 3 (MDU07) Absorbed dose calculation D 1 = m 256 Si N i i= 1 ε ε i is energy deposition i 18
Energy deposition calibration of Liulin Original method: Energy deposition ε i = i 81.3keV i ADC channel number 19
Comparison of two identical Liulins MDU 1 Front aluminum cover removed from both Liulins PE desk removed from MDU 1 MDU 2 180 160 140 C 400 MeV/u Beam: C 400 MeV/u PMMA: 0.0 mm 86.0 mm 178.5 mm 208.5 mm D / µgy 120 100 80 60 40 20 0 0 50 100 150 200 250 Thickness of PMMA filters / mm 20
Identical Liulins in C 400MeV/u Relative number of events 1.0E+00 1.0E-01 1.0E-02 1.0E-03 1.0E-04 1.0E-05 1.0E-06 Liulins in C 400MeV/u, 0mm of PMMA 79.5 84.0 4.5 MDU1 MDU2 0 50 100 150 200 250 ADC Channel number Relative number of events 1.0E+00 1.0E-01 1.0E-02 1.0E-03 1.0E-04 1.0E-05 1.0E-06 Liulins in C 400MeV/u, 86mm of PMMA 95.3 100.5 5.2 MDU1 MDU2 0 50 100 150 200 250 ADC Channel number 1.0E+00 Liulins in C 400MeV/u, 178.5mm of PMMA 1.0E+00 Liulins in C 400MeV/u, 208.5mm of PMMA Relative number of events 1.0E-01 1.0E-02 1.0E-03 1.0E-04 1.0E-05 146.5 7.8 154.3 MDU1 MDU2 Relative number of events 1.0E-01 1.0E-02 1.0E-03 1.0E-04 12.9 235.1 248.0 MDU1 MDU2 1.0E-06 0 50 100 150 200 250 ADC Channel number 1.0E-05 0 50 100 150 200 250 ADC Channel number 21
Recalibration of Liulin using PHITS 22
Recalibration of Liulin using PHITS Gaussian fits of all peaks (primary C, fragments) 0.0 mm 86.0 mm 175.5 mm 208.5 mm 23
Recalibration of Liulin using PHITS 300 MDU 1 (no Al, no PE) Energy deposition / MeV 250 MDU 2 (no Al) Energy deposition / MeV ADC channel number 250 200 150 100 50 linear fit y = 13.465x - 0.4254 ADC channel number 200 150 100 50 linear fit y = 12.713x + 0.2618 0 0 0 5 10 15 20 Energy deposition / MeV 0 5 10 15 20 Energy deposition / MeV 24
Comparison of two identical Liulins 1.0E+00 Liulins in C 400MeV/u, 0mm of PMMA 1.0E+00 Liulins in C 400MeV/u, 86mm of PMMA Relative number of events 1.0E-01 1.0E-02 1.0E-03 1.0E-04 1.0E-05 Primary C Pile-up MDU1 MDU2 Relative number of events 1.0E-01 1.0E-02 1.0E-03 1.0E-04 1.0E-05 MDU1 MDU2 1.0E-06 0 5 10 15 20 25 Energy deposition / MeV 1.0E-06 0 5 10 15 20 25 Energy deposition / MeV 1.0E+00 Liulins in C 400MeV/u, 178.5mm of PMMA 1.0E+00 Liulins in C 400MeV/u, 208.5mm of PMMA 1.0E-01 MDU1 1.0E-01 MDU1 Relative number of events 1.0E-02 1.0E-03 1.0E-04 1.0E-05 MDU2 Relative number of events 1.0E-02 1.0E-03 1.0E-04 MDU2 1.0E-06 0 5 10 15 20 25 Energy deposition / MeV 1.0E-05 0 5 10 15 20 25 Energy deposition / MeV 25
Comparison of Liulin spectra with PHITS 1.0E+00 Liulins in C 400MeV/u, no BF 1.0E+00 Liulins in C 400MeV/u, 86.0 mm 1.0E-01 1.0E-01 Relative number of events 1.0E-02 1.0E-03 1.0E-04 PHITS MDU2 Relative number of events 1.0E-02 1.0E-03 1.0E-04 PHITS MDU2 1.0E-05 1.0E+00 0 5 10 15 20 25 Energy deposition / MeV Liulins in C 400MeV/u, 178.5 mm 1.0E-05 1.0E+00 0 5 10 15 20 25 Energy deposition / MeV Liulins in C 400MeV/u, 208.5 mm 1.0E-01 1.0E-01 Relative number of events 1.0E-02 1.0E-03 1.0E-04 PHITS MDU2 Relative number of events 1.0E-02 1.0E-03 1.0E-04 PHITS MDU2 1.0E-05 0 5 10 15 20 25 Energy deposition / MeV 1.0E-05 0 5 10 15 20 25 Energy deposition / MeV 26
Liulin in Ne 400 MeV/u 180 160 Ne 400 MeV/u 1.0E+00 Liulin MDU2 in Ne 400MeV/u D / µgy 140 120 100 80 60 40 20 0 0 20 40 60 80 100 120 140 Thickness of PMMA filters / mm Relative number of events 1.0E-01 He 1.0E-02 Be 1.0E-03 1.0E-04 B C 0mm 1mm 51.5mm N O 0 5 10 15 20 25 Energy deposition / MeV F Ne 1.0E+00 Liulin in Ne 400MeV/u, 51.5mm of PMMA Relative number of events 1.0E-01 1.0E-02 1.0E-03 1.0E-04 1.0E-05 MDU2 PHITS 0 10 20 30 40 27 Energy deposition / MeV
Contribution of fragments to total dose at the sample location Absorbed dose contribution 100 10 1 0.1 1.68 1.28 0.93 0.0mm 26.5mm 90.5mm C 290MeV/u 4.61 2.67 2.08 1.95 1.51 1.05 0.88 1.02 0.55 0.55 0.37 0.28 0.26 0.28 0.17 0.10 0.07 0.07 97.9494.85 88.90 0.01 p d H He Li Be B C 28
Contribution of fragments to total dose at the sample location Absorbed dose contribution 100 10 1 0.1 0.0mm 51.5mm 94.5mm 1.12 1.31 1.32 1.57 1.56 2.33 0.56 0.62 0.27 0.20 0.15 0.05 0.05 0.03 Ne 400MeV/u 0.50 0.40 0.32 0.23 0.22 0.26 0.22 0.25 0.09 97.78 85.79 77.49 7.21 3.90 2.80 3.81 3.72 1.87 2.24 2.42 0.39 0.30 0.01 p d H He Li Be B C N O F Ne 29
Evaluation of LET spectra with Liulin L w = ksi / w L ε LSi = d d = 300µ m Si ρw ρ Si Ion Energy / (MeV/u) Water was used instead of Si-diode! k Si/w (Si to water conv. Coefficient) He 150 1.36 C 135 1.23 C 290 1.24 C 400 1.26 Ne 400 1.24 Liulin E dep and LET spectra calculated with PHITS, C 135 MeV/u 30
Conclusions Detail simulation of geometry of HIMAC BIO was developed Calibration of Liulin can be done using only one heavy ion beam Liulin is capable to detect fragments; the difference between measured and calculated energy deposition spectra in peaks can be important, more research on this topic is in process The contribution of fragments to total absorbed dose is high, from 2% to 23% depending on primary heavy ion, energy and thickness of PMMA filters Si to water conversion coefficient estimated using PHITS code differ depending on ion and energy (1.24 1.36) Further research on calculation of neutron contribution in the radiation field is needed 31
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