Tecnologie a diamante

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1 Tecnologie a diamante Gianluca Verona Rinati Dipartimento di Ingegneria Industriale, Italy INFN Sez. Roma gianluca.verona.rinati@uniroma.it Diamond properties Lattice constant Nearest neighbours Band Gap 3.56 Ǻ 1.54 Ǻ 5.5 ev 1

2 Diamond properties Diamond properties Diamond applications HARDNESS 9 Kg/mm (the higest) YOUNG S MODULES 11 N/m (the strongest) FRICTION.5 (the lowest) THERMAL CONDUCTIVITY W/cm K (5 times Cu) ELECTRICAL RESISTIVITY 1 16 Ωcm ELECTRICAL BREAKDOWN 1 7 V/cm (3 times GaAs) ELECTRON, HOLE MOBILITY > cm/v s OPTICAL ABSORPTION transparent from IR to IV (5.4 ev) MELTING POINT 335 C RADIATION HARDNESS very high CHEMICAL REACTIVITY extremely low Radiation detectors Particle detectors E-UV, V-UV sensors Soft-X sensors Transistors Fast FET High power FET Quantum computing Chemical sensors Optical windows Biological application Cold cathodes / field emitters Heat spreaders Diamond properties DOSIMETRIC PROPERTIES OF DIAMOND Near tissue equivalent High sensitivity per unit volume Photovoltaic regime operation Radiation hardness Low temperature dependence

3 Diamond properties Natural Diamond Syngle crystal Small in size Low availability - high cost No reproducibility Natural diamond dosimeters already in the market (PTW Freiburg) Natural diamonds: differences between different natural stones (NDD) high cost ( 15 k ) very long delivery times (more than 1 year) Synthetic diamond Chemical Vapor Deposition (CVD) High Pressure High Temperature (HPHT) Synthetic diamond Synthetic HPHT diamond Single crystal Small in size Low cost Poor electronic quality Polycrystalline CVD diamond Low cost and large area possible Polycrystalline Polarization / memory effects Synthetic CVD single crystal diamond Single crystal Small in size High electronic quality 3

4 CVD diamond deposition Microwave Plasma CVD SUBSTRATE TEMPERATURE OPTICAL PYROMETER MICROWAVE POWER FLOW CONTROLLERS GAS IN QUARTZ WINDOW QUARTZ TUBE PLUNGER MICROWAVE GENERATOR.45 GHZ PRESSURE CONTROL SAMPLE TO PUMP Typical growth parameters Plasma composition 99% H - 1% CH 4, Temperature 65 8 C Microwave power 6-13 W Pressure 1-15 mbar Gas flow rate 1 sccm Ag contact Al contact CVD slightly B doped CVD B+ doped HPHT substrate Output Single crystal diamond dosimeter Electrons, Photons, Protons 8 mm Ag contact Al contact CVD CVD Output 35 mm mm SCD PMMA Epoxy resin HPHT substrate Single crystal diamond Volume: <.1 mm3 Sens.: 1-8 nc/gy V bias: V Waterproof 4

5 Radiation therapy facility Experimental setup: Varian Clinac DHX (S. Filippo Neri Hospital, Policlinico Gemelli) Electa Precise accelerator (PTV) Electa Synergy (A.O.U. Careggi, Firenze) MP3 and MP1 water phantoms (PTW) Tandem electrometer (PTW) Unidos E electrometer (PTW) Mephisto software (PTW) The on-site acquisition system is used No need of dedicated electronics Dose linearity Q (nc) Field size 1x1 cm Field size x cm 1 MV Photons 1 cm deep in water x and 1x1 cm square fields Linear correlation parameter R =1 with a precision of 1-6 Deviation from linearity below ±.5% down to cgy 1.5 (<Q/M.U.>-1)x M.U. A.O. S. Filippo Neri, Roma 5

6 Dose rate and DPP dependence Normalized Q SCD / Q PTW Dose Rate dependence Dose Rate (MU/min) Dose Rate dependence is studied by varying the Pulse Repetition Frequency (PRF) of the Linac: variations of about ±.% (SCDD with PTW-like housing) (reference dosimeter: PTW 311 Semiflex IC) Q SCD / Q Farmer Dose per pulse dependence Dose Rate (Gy/min) Dose Per Pulse dependence is studied by varying the Source to Surface Distance (SSD) distance in the range 75-3 cm: variations of about ±.8% (SCDD with PTW-like housing) (reference dosimeter: PTW 313 Farmer IC) Policlinico di Tor Vergata, Roma Angular dependence 1.5 Polar angle 4 Azimuth angle Deviation from response (%) Angle (deg) cm.4 cm (d max ) Angle (deg) A.O. S. Filippo Neri, Roma 6

7 Temperature dependence Deviation from 3 C response (%) Temperature ( C) Observed dependence in the 18 C 4 C range changing the temperature by 1 C steps Maximum difference of about ±.% from the linear best fit Temperature coefficient of.14% C -1 A.O. S. Filippo Neri, Roma Output Factors Output Factors SCDD.7 Semiflex Diode P.6 Diode E Diamond Field Size (cm) Courtesy of PTW Freiburg 7

8 Output Factors Output Factors SCDD.95 Semiflex Diode P Diode E Diamond Field size (cm) Output Factors SCDD Semiflex Diode P Diode E Diamond Field size (cm) Relative deviation of the output factors from the Semiflex IC (reference dosimeter for large fields) Relative deviation of the output factors from the Diode E (reference dosimeter below 4x4 cm fieds) Courtesy of PTW Freiburg Photon beams: small fields PDD (%) SCDD 1x1 cm PP-IC 1x1 cm SCDD 1x1 c m PP-IC 1x1 cm 1x1 cm Normalised dose 1. SCD PP 1x1 cm.8 x 3x3.6 4x4 5x5 1x1.4. (SCDD/PP - 1)* x1 cm 1x1 cm 1x1 cm Depth (cm) PDDs: SCDD vs PTW 3114 PinPoint in vertical orientation Difference Plots: PTW 3114 PP SCDD A.O. S. Filippo Neri, Roma Difference (D SCDD - D PP-IC ) x1 cm x cm 3x3 cm 4x4 cm 5x5 cm 1x1 cm Lateral distance (cm) Beam profiles: SCDD vs PTW 3114 PinPoint in vertical orientation Difference plots: PTW 3114 PP SCDD 8

9 Spatial resolution: penumbra Normalised dose SCDD hor. (cross) SCDD vert. (cross) MV Field size (cm ) Lateral distance (mm) SCDD 9%-1% Penumbra (mm) SCDD hor. (cross) PP-IC vert. (cross) PP-IC 9%-1% Penumbra (mm) Vertical Horizontal Vertical Horizontal Inplane Cross- Plane Inplane Cross- Plane Inplane Cross- Plane Inplane Cross- Plane %-1% penumbra measured with the SCDD and PP-IC Best orientation for SCD was found to be the horizontal one Averaged values from SCD and PP-IC were then compared SCD spatial resolution (penumbra) is always better than the one from the PP-IC Penumbra narrowing of.9 mm and.4 mm in x and 1x1 cm respectively A.O. S. Filippo Neri, Roma Electrons: PDD Relative Dose (%) Relative Dose (%) MeV electrons IC as measured IC software corrected SSCD as measured IC 18 MeV SCD 18 MeV IC 15 MeV SCD 15 MeV IC 1 MeV SCD 1 MeV IC 9 MeV SCD 9 MeV IC 6 MeV SCD 6 MeV SCD 6 MeV bis Depth (mm) Accelerator A very good agreement is found between SSCD and IC with no need of any correction of the as measured data from the SSCD SCD Depth A.O. S. Filippo Neri, Roma 9

10 Electron beams: small fields cm 6, 8, 1, 1, 15 MeV 1 MeV, 3, 4, 5 cm PDD (%) Si-D - SCDD SCDD 6 MeV SCDD 8 MeV SCDD 1 MeV SCDD 1 MeV SCDD 15 MeV Si-D all energies 6 MeV - 8 MeV - 1 MeV - 1 MeV - 15 MeV Depth (mm) PDD: SCDD vs PTW Diode E in electron beams: cm tubular applicator and several beam energies (6, 8, 1, 1 and 15 MeV) Policlinico di Tor Vergata, Roma Normalized Charge (%) Si-D - SCDD Si all applic ators SCDD cm SCDD 3 cm SCDD 4 cm SCDD 5 cm Beam profiles: SCDD vs PTW Diode E in small field 1 MeV electron beams, obtained by tubular applicators, 3, 4 and 5 cm in diameter cm 3 c m 4 cm 5 cm Inplane Position (mm) VMAT - Treatment plan verification A.O.U. Careggi, Firenze 1

11 VMAT - Treatment plan verification Measured points in GT profiles (y positions), calculated dose, estimated relative gradient, DD and DTA for A1SL and SCDD A.O.U. Careggi, Firenze Hadron therapy Laboratori Nazionali del Sud (LNS) - INFN, Catania Italy Bragg curve for a MeV proton beam 11

12 Hadron therapy: dose linearity charge (nc) Equation sottraz. offset Linear Fit of D Allometric Fit of D y = a + b*x Adj. R-Square Value Standard Error D Intercept -- D Slope E-6 Equation delivered dose (Gy) y = a + b*x^c Adj. R-Square Value Standard Error D a D b E-4 D c relative deviation (%) delivered dose (Gy) 6 MeV Protons Deviation from linearity within ±.5% down to cgy LNS - INFN, Catania Italy Hadron therapy: dose rate dependence relative deviation (%) DR (Gy/min) 6 MeV Protons Constant response within ±.5% LNS - INFN, Catania Italy 1

13 Hadron therapy: Bragg curves normalized response (a.u.) 1. SCD 15 Markus IC Energy dependence not observed No radiation damage up to maximum delivered dose (1 kgy) position (mm) LNS - INFN, Catania Italy EURAMET JRP-7 project European metrology institutions collaboration: PTB-Germay, INMRI-Italy, LNHB-France, VSL-Netherlands, NPL-United Kingdom, SMU-Slovakia, STUK-Finland, UME-Turkey Main aim of JRP 7: development of primary standards (graphite and water calorimeters) for absorbed dose measurements in small radiation fields the investigation of promising radiation detectors for their applicability as secondary standards in small fields definition of a beam quality parameter for small fields, since the qualifiers used for standard fields are not adequate. ENEA-INMRI C R Casaccia 13

14 Stability and reproducibility Long term reproducibility:.4% (1σ) ENEA-INMRI C R Casaccia Monte Carlo Simulation The detector response is independent of field size within.5% from 1 cm x 1 cm down to cm x cm. Correction factors calculated for fields size down to 1x1 cm The Monte Carlo calculations were experimentally verified calibrating at PTB ENEA-INMRI C R Casaccia 14

15 EURAMET JRP-7 project results JRP-7 results (secondary standard) Only diamond prototypes (Rome Tor Vergata) and alanine are found to be suitable for absorbed-dose-to-water measurements traceable to the D w primary standards in radiotherapy photon beams down to 1 x 1 cm field size. SSCD detectors and alanine show similar accuracy in measuring D w in small field (1% in 1x1 cm fields), but the diamond detector has the advantage of a real time reading and a smaller sensitive volume (smaller volume correction calculation needed). ENEA-INMRI C R Casaccia Conclusions Diamond diodes exhibit unique properties for dose determination in radiotherapy application, especially when very collimated beams are used. Dosimetric properties comparable with the ones from several well assessed commercial dosimeters have been demonstrated in all the investigated radiation qualities and irradiation conditions The commercialization of SCDDs will start on August 13 by PTW- Freiburg (microdiamond Type 619) 15

16 Collaborations Dip. Ing. Industriale I. Ciancaglioni C. Di Venanzio M. Marinelli E. Milani F. Pompili G. Prestopino A. Tonnetti C. Verona INMRI - ENEA Casaccia M. Pimpinella A. Guerra Laboratori Nazionali del Sud INFN, Catania G.A.P. Cirrone G. Cuttone L. Raffaele C. Tuvè Policlinico di Tor Vergata D. Falco R. Santoni P. Bagalà Ospedale S. Filippo Neri, Roma R. Consorti A. Petrucci Universita degli Studi di Firenze - Azienda Ospedaliera Careggi M. Bucciolini M. Casati C. Talamonti M. Zani Polilclinico Gemelli, Roma A. Fidanzio A. Piermattei Funds and financial support Progetto DIARAD Progetto DIAMED 16