S. Agosteo (1,2), A. Fazzi (1,2),, M.V. Introini (1,2), A. Pola (1,2), E. Sagia (1,3), V. Varoli (1,2)

Transcription

1 S. Agosteo (1,), A. Fazzi (1,),, M.V. Introini (1,), A. Pola (1,), E. Sagia (1,3), V. Varoli (1,) 1 Politecnico di Milano, Dipartimento di Energia, Sezione di Ingegneria Nucleare, via Ponzio 3/3, 133 Milano, Italy Istituto Nazionale di Fisica Nucleare, Sezione di Milano, via Celoria 1, 133 Milano, Italy. 3 ARDENT initiative, funded by the European Union (call FP7-PEOPLE-11-ITN project number 919) Seoul, Korea - 7 October 13

2 Concept of silicon microdosimetry Si-devices can provide sensitive zones of the order of a micrometer Tissue-equivalent converter Silicon device Spectroscopy Chain Spectrum of the energy imparted per event in silicon Data Analysis Analytical corrections Microdosimetric spectrum in tissue 1. B. Rosenfeld, P. Bradley, I. Cornelius, G. Kaplan, B. Allen, J. Flanz, M. Goitein, A.V. Meerbeeck, J. Schubert, J. Bailey, Y. Tabkada, A. Maruashi, Y. Hayakawa, New silicon detector for microdosimetry applications in proton therapy, IEEE Trans. Nucl. Sci. 7() () Seoul, Korea - 7 October 13

3 Monolithic silicon telescope Segmented ΔE stage n + p +? E 1.9?m) ΔE stage p + E element 9 µm E stage E stage 5?m) n + ~ μm 5 µm E stage 1 µm Guard Sensitive area 1 mm 7 pixels in parallel Sensitive area.5 mm Seoul, Korea - 7 October 13 3

4 For deriving microdosimetric spectra comparable to those a acquired by a TEPC: Tissue equivalence for silicon Optimized tissue equivalence correction by measuring event by event the energy of the impinging particles. Shape equivalence The linear energy is calculated by the mean chord length. 1. S. Agosteo, P. Colautti, A. Fazzi, D. Moro and A. Pola, A Solid State Microdosimeter based on a Monolithic Silicon Telescope, Radiat. Prot. Dosim. 1, 3-3 ().. S. Agosteo, P.G. Fallica, A. Fazzi, M.V. Introini, A. Pola, G. Valvo, A Pixelated Silicon Telescope for Solid State Microdosimeter, Radiat. Meas., accepted for publication. Seoul, Korea - 7 October 13

5 Analytical procedure for tissue-equivalence correction Energy deposited along a track of length l by recoil-protons of energy E p in a tissue-equivalent E detector. Scaling factor : stopping powers ratio Seoul, Korea - 7 October 13 Energy & type of impinging particle 5

6 The procedure is based on chord length distributions The ΔE elements are cylinders of micrometric dimensions as the TEPCs By assuming a constant linear energy transfer L: By equating the dose-mean energy imparted per event for the two different shapes considered: Dimensions of E stages were scaled by a factor η the lineal energy y was calculated by considering an equivalent mean cord length equal to: l E, eq l E Seoul, Korea - 7 October 13

7 Counts per unit dose Counts per unit dose Energy deposited in the E stage (kev) Depth = 1 mm Dose =.3 Gy Irradiations with a MeV modulated proton beam at CATANA facility (LNS-INFN Catania) Depth dose curve (a.u.) depth in PMMA (mm) 1 Energy deposited in the E stage (kev) 1 Depth = 15.5 mm Dose =. Gy Energy deposited in the E stage (kev) Counts per unit dose Depth = mm Dose =.3 Gy Energy deposited in the E stage (kev) Energy deposited in the E stage (kev) Counts per unit dose Depthin = 1 deposited Energy themm E stage (MeV) Dose =. Gy Depth = 1.5 mm 1 Dose =. Gy Counts per unit dose Seoul, Korea - 7 October

8 silicon telescope 5.7 mm cylindrical TEPC 5.7 mm cylindrical TEPC 5.7 mm silicon telescope 7. mm cylindrical TEPC 7. mm cylindrical TEPC 7. mm silicon telescope 1.5 mm cylindrical TEPC 11. mm cylindrical TEPC 11. mm silicon telescope 1. mm cylindrical TEPC 1. mm cylindrical TEPC 1. mm Depth dose curve (a.u.) silicon telescope 1 mm cylindrical TEPC 1. mm cylindrical TEPC 1. mm Constant TE scaling factor depth in PMMA (mm) Seoul, Korea - 7 October 13

9 silicon telescope.5 mm cylindrical TEPC.1 mm cylindrical TEPC.1 mm silicon telescope 1. mm cylindrical TEPC 1. mm cylindrical TEPC 1. mm.... silicon telescope 1. mm cylindrical TEPC 1. mm cylindrical TEPC 1. mm silicon telescope 1. mm cylindrical TEPC 1. mm cylindrical TEPC 1. mm Depth dose curve (a.u.) depth in PMMA (mm) Seoul, Korea - 7 October 13 silicon telescope 1. mm cylindrical TEPC mm cylindrical TEPC mm Event-by-event TE correction 9

10 E-E scatter plots and lineal energy spectra B C FLUKA simulation Measurement position A 7.5 mm Counts per monitor unit 3.E B 7. mm Counts per monitor unit.e dose (a.u.) 1 1 A D E F G depth in PMMA (mm) A (7.5 mm PMMA) B (7. mm PMMA) C (7.5 mm PMMA) D (7.7 mm PMMA) H C 7.5 mm Counts per monitor unit.e D 7.7 mm Counts per monitor unit.e- 5.E- 9.E Seoul, Korea - 7 October y (kev/ m) 1

11 E-E scatter plots and lineal energy spectra C B FLUKA simulation Measurement position E G Analytical distributions H He Li Be B C Analytical distributions H He Li Be B C Counts per monitor unit.e- 7.5E E-.55E- 3.E- Counts per monitor unit 5.E-7.53E-5 5.5E E-5 1.E F H Analytical distributions Analytical distributions H He Li Be B C H He Li Be B C Counts per monitor unit 1.E-.575E-5 5.5E E-5 1.E- Counts per monitor unit.e- 1.31E-.5E- 3.77E- 5.E Seoul, Korea - 7 October 13 dose (a.u.) 1 1 A D E F G depth in PMMA (mm) E (mm PMMA) F (9mm PMMA) G (1mm PMMA) H (3mm PMMA) 11 H

12 Seoul, Korea - 7 October 13 Microbeam ~ 1.5μm spot size of 1MeV carbon ions Ion Beam Centre of University of Surrey (Guilford, UK) 1

13 BioQuart Project EURAMET and SPIRIT Project EU Seoul, Korea - 7 October 13 13

14 FLUKA simulations 1 C MeV/u in PMMA.. 1 cm 3.5 cm cm cm Seoul, Korea - 7 October

15 The silicon microdosimeters show interesting features for microdosimetry, but still there are some issues that should be shorted out: electronic noise (minimum detectable lineal energy); radiation hardness when exposed to high-intensity hadron beams. Further study Seoul, Korea - 7 October 13 15