SINGLE CRYSTAL CVD DIAMOND MEMBRANE MICRODOSIMETERS FOR HADRON THERAPY. ADAMAS2017 Zagreb 28/11/2017 Pomorski Michal

Transcription

1 SINGLE CRYSTAL CVD DIAMOND MEMBRANE MICRODOSIMETERS FOR HADRON THERAPY ADAMAS217 Zagreb 28/11/217 Pomorski Michal

2 INTERESTS FOR MICRODOSIMETRY COMMUNITY A slide from the opening lecture of MICROS th International Symposium on Microdosimetry By H.G. Menzel (5 th November 217) Microdosimetric community seems to be waiting for diamond based sensors! ADAMAS217 Zagreb 27/11/217 Pomorski Michal 2

3 OUTLINE 1) Introduction 2) Concept and fabrication 3) Charge transport with p, C microbeams a. micro SV definition b. charge collection efficiency c. radiation hardness 4) Preliminary LET for 1 MeV proton beam ADAMAS217 Zagreb 27/11/217 Pomorski Michal 3

4 HADRON THERAPY 12 hadron therapy centres worldwide (increasing); 1 patients treated; operating clinical proton therapy centres in France: Orsay, Nice, Caen; ARCHADE : first carbon therapy centre in France; an intense field of research activity including new methods of treatment (mini and microbeams, FLASH). ADAMAS217 Zagreb 27/11/217 Pomorski Michal 4

5 RADIATION QUALITY Double-strand DNA breaks same dose but different LET thus various biological effectivness single α-particle irradiation RBE (Relative Biological Effectiveness) of protons is uncertain : limits the efficiency of treatments; strong correlation between a microdosimetric quantity (i.e. spatial distribution of energy deposition by single particle at cellular level) and RBE : LET (linear energy transfer) and biological effects of charged particles in tissues are related; measurement of LET is difficult : today no detector is available in clinical routine. Simple dosimetry is not enough to assure radiation quality in hadron therapy ADAMAS217 Zagreb 27/11/217 Pomorski Michal 5

6 RADIATION QUALITY - MICRODOSIMETRY MICRODOSIMETRY is a methodology that involves the measurement or calculation of stochastic energy deposition distributions in a micron size sensitive volume (SV) within any arbitrary mixed radiation field. A concept of solid-state microdosimeter picture from Si-3DMiMic collaboration microdosimetry dosimetry at micron scale - single-particles (low charge), - ns to µs integration time (1^9 p/cm2), - pulse-height spectra, - SV from micro to nano size (3 µm cell, 1 µm cell nucleus, > 1 µm DNA size) - ms integration time - DC current or charge - macroscopic (mm) SV size ADAMAS217 Zagreb 27/11/217 Pomorski Michal 6

7 MICRODOSIMETRY IN HADRON THERAPY Tissue Equivalent Proportional Counter (TEPC) Silicon solid-state microdosimeters A. Rosenfeld, NIM a gold standard + sensitive (internal amplification) + tissue-equivalence, radiation hard - size (not really microscopic SV, wall effect) - rate issue - maintenance (gas flow) + compact device + multiple real µsvs + it s Si easy for micro-fabrication - tissue equivalence (?) - radiation hardness (?)? Can diamond join the advantages of both, and get rid of their pitfalls? ADAMAS217 Zagreb 27/11/217 Pomorski Michal 7

8 WHY DIAMOND? Large band-gap (5.5eV) semiconductor A solid-state ionization chamber (soon a proportional chamber(?)) more tissue equivalent (Z=6) and radiation hard (43 ev) + no leakage current and no need for p-n junction + fast drift velocity for e-h + low capacitance + high electrical breakdown (> 1 V/µm) + VIS light and temp. insensitivity - high ~13 e-h/ev lower signal - high density, excitons pulse height defect - it s diamond (for instance pls. forget 6 wafers) since 22 high purity electronic grade CVD diamond available commercially ADAMAS217 Zagreb 27/11/217 Pomorski Michal 8

9 MICRODOSIMETRY IN HADRON THERAPY existing diamond microdosimeters prototypes The idea 5.9 MeV Be microbeam CCE mapping Real device Pulse-height spectra commercial e6 EG sccvd diamond -not uniform CCE - not resolved spectra ADAMAS217 Zagreb 27/11/217 Pomorski Michal 9

10 MICRODOSIMETRY IN HADRON THERAPY existing diamond microdosimeters prototypes The idea 4 MeV C microbeam CCE mapping Real device Pulse-height V bias voltage lab grown sccvd diamond - problematic to create multiple µsvs ADAMAS217 Zagreb 27/11/217 Pomorski Michal 1

11 DIAMOND MEMBRANE MICRODOSIMETER CONCEPT sccvd diamond membrane Charge V 3-6 µm few mm p-i-m µsv m-i-m > 1 µm p-i-m m-i-m ADAMAS217 Zagreb 27/11/217 Pomorski Michal 11

12 DIAMOND MEMBRANE MICRODOSIMETER PROTOTYPES ElementSix electronic grade single crystal CVD diamond samples slicing polishing Ar/O plasma etching p+ CVD growth patterning + electrodes 3-5 µm 3-6 µm >1 µm read-out read-out 3 µm pixels (SV), 6 µm thick sccvd diamond membrane 3, 6 and 12 µm pixels (SV), 4 µm thick sccvd diamond membrane ADAMAS217 Zagreb 27/11/217 Pomorski Michal 12

13 CHARGE TRANSPORT CHARACTERIZATION IBIC Ion Microbeams energy loss [kev/µm ] MeV C 2.5 MeV p depth [µm] CS electronics 2.5 MeV proton 16.6 MeV carbon 1 µm FWHM ~ 1 µm FWHM preamp.: Amptek 25 CoolFet Shaping time.: 5 ns local DAQ ΔE + E configuration vacuum ion microbeam Si PIPS membrane ADAMAS217 Zagreb 27/11/217 Pomorski Michal 13

14 IBIC 2.5 MEV PROTON MICROBEAM STIM (Si downstream) diamond V *STIM scanning transmission ion microscopy ADAMAS217 Zagreb 27/11/217 Pomorski Michal 14

15 IBIC MEV PROTON MICROBEAM diamond V 12 1 pulse height % drop ~8 µm STIM (Si downstream) *STIM scanning transmission ion microscopy counts normalized to max 1,, full area inside pixel X [µm] pulse-height spectra ΔE ~25 kev (~41 kev/µm), pulse height [a.u.] ADAMAS217 Zagreb 27/11/217 Pomorski Michal 15

16 IBIC 16.6 MEV CARBON MICROBEAM STIM (Si downstream) diamond V µm SV 7 µm µm SV Si pulse height [a.u.] *STIM scanning transmission ion microscopy diamond pulse height [a.u.] ADAMAS217 Zagreb 27/11/217 Pomorski Michal 16

17 IBIC 16.6 MEV CARBON MICROBEAM m-i-m parasitic signal inverted polarity m-i-m signal B 1 counts 2 15 SV signal (p-i-m) adc channel Higher signals at the edges strain some areas with zero PH ADAMAS217 Zagreb 27/11/217 Pomorski Michal 17

18 IBIC 16.6 MEV CARBON MICROBEAM [µm] diamond V diamond pulse height [a.u.] [µm] STIM (Si downstream) 12 1 pulse-height spectra ΔE~8 MeV (2 kev/µm) 2 8 [µm] 3 4 counts *STIM scanning transmission ion microscopy ADC channel ADAMAS217 Zagreb 27/11/217 Pomorski Michal 18

19 CHARGE COLLECTION EFFICIENCY 16.6 MeV C (microbeam) ~5 MeV α ( 241 Am source) V/µm CCE~8% (C) Counts ,,2,4,6,8 signal amplitude [V] V +16V CCE ~1% ADC channel [a.u.] V/µm forward µsv p-i-m m-i-m.45 V/µm Voc ~ 1.8 V reverse bias voltage [V] ~1% V (.3 V/µm built-in) p, α ~8% V (.45 V/µm built-in) C solution: use of thinner membranes for high LET i.e. 1.8 V / 1 µm ~1% CCE ADAMAS217 Zagreb 27/11/217 Pomorski Michal 19

20 RADIATION HARDNESS CARBON MICROBEAM High flux C (16.6 MeV) microbeam continuous irradiation of one 3 x 3 µm µsv (all spectra V) counts x 1 12 C/cm pulse height [a.u.] normalized pulse height 1,,8,6,4,2, ~12% CCE drop after.64 x 1 12 C ions/cm 2,,2,4,6,8 1, fluence [1 12 C ions / cm 2 ] no change: Voc, spectrum shape, peak FWHM, dark current, µsv geometry even better results expected for thinner membranes (shorter drift path; higher E) ADAMAS217 Zagreb 27/11/217 Pomorski Michal 2

21 SIGNAL FORMATION TRANSIENT CURRENTS 5 MeV α-particles traversing membrane,6 signal amplitude [V],5,4,3,2,1, V µsv (p-i-m) 2.5V (m-i-m) time [ns] fast signals (clearly RC limited, 1mm 2 contacts area) contact surface optimization << 1 ns FWHM + high amplitude ADAMAS217 Zagreb 27/11/217 Pomorski Michal 21

22 LET MEASUREMENT 1 MEV PROTON BEAM Institute Curie Proton therapy Center (Orsay, France) 1 8 Bragg peak (IBA PP5) dose [a.u.] Proton beamline for intracranial treatments 1 MeV p 8 mm variable thickness solid-water phantom 3 µm SV diamond microdosimeter prototype y*d(y) 1,4 1,2 1,,8,6,4,2, depth H 2 O diamond membrane microdosimeter lineal energy [au] ADAMAS217 Zagreb 27/11/217 Pomorski Michal 22 mm 68 mm 78 mm

23 DIAMOND MEMBRANE MICRODOSIMETER-SUMMARY sccvd diamond membranes have a great potential for solid-state microdosimetry o full CCE V, well-defined µsv, ΔE spectra, fast o radiation hard (preliminary C data) o First LET measurements in clinical p beam (promising) Issues to be addressed soon: - µsv geometry optimization: 3D, implantation, thickness homogeneity - pulse-height defect for high LET (C) - dedicated electronics - real LET measurements (mixed fields) ADAMAS217 Zagreb 27/11/217 Pomorski Michal 23

24 DIAMIDOS COLLABORATION CO-AUTHORS Philippe Bergonzo, Dominique Tromson, Izabella Zahradnik CEA-LIST Thierry Pourcher, Joel Herault CEA-DRF, Antoine Lacassagne Center Ludovic de Marzi IC-CPO, Orsay Philippe Barbaret CENBG, Bordeaux Natko Skukan, Ivan Sudić, Milko Jaksic RBI, Zagreb, Croatia Wataru Kada, T. Kamiya, S. Onoda, T. Ohshima Gunma University, QST Takasaki, Japan ADAMAS217 Zagreb 27/11/217 Pomorski Michal 24

25 THANKS TO: DiamFab for growing excellent quality p+ diamond homoepitaxial layers Thank you very much for your kind attention!!! ADAMAS217 Zagreb 27/11/217 Pomorski Michal 25

26 Commissariat à l énergie atomique et aux énergies alternatives Institut List CEA SACLAY NANO-INNOV BAT. 861 PC Gif-sur-Yvette Cedex - FRANCE www-list.cea.fr Établissement public à caractère industriel et commercial RCS Paris B

27 MICRODOSIMETRY IN HADRON THERAPY same dose but different LET thus various biological effectiveness RBE (Relative Biological Effectiveness) of protons is uncertain : limits the efficiency of treatments; strong correlation between a microdosimetric quantity (i.e. spatial distribution of energy deposition by single particle at cellular level) and RBE : LET (linear energy transfer) and biological effects of charged particles in tissues are related; measurement of LET is difficult : today no detector is available in clinical routine. Challenges: single particles, pulse-height, low-signals, high rates, radiation damage 17 th International Symposium on Microdosimetry, Venice, Italy 1/11/217 Pomorski Michal 27