Presentation is loading. Please wait.

Presentation is loading. Please wait.

NATURAL AND CVD TYPE DIAMOND DETECTORS AS DOSIMETERS IN HADROTHERAPY APPLI CATIONS Cirrone G.A.P., Cuttone G., Raffaele L., Sabini M.G., De Angelis C.,

Similar presentations


Presentation on theme: "NATURAL AND CVD TYPE DIAMOND DETECTORS AS DOSIMETERS IN HADROTHERAPY APPLI CATIONS Cirrone G.A.P., Cuttone G., Raffaele L., Sabini M.G., De Angelis C.,"— Presentation transcript:

1 NATURAL AND CVD TYPE DIAMOND DETECTORS AS DOSIMETERS IN HADROTHERAPY APPLI CATIONS Cirrone G.A.P., Cuttone G., Raffaele L., Sabini M.G., De Angelis C., Onori S., Pacilio M., Bucciolini M., Bruzzi M., Sciortino S. INFN-Laboratori Nazionali del Sud, Catania CATANA - Italian Center for Prothontherapy Istituto Superiore di Sanità, Roma Dipartimento di Fisiopatologia Clinica Università di Firenze, Firenze Dipartimento di Energetica, Università di Firenze, Firenze

2 Diamond is potentially a very suitable material for use as radiation dosimeter Wide band gap Low dark current and low sensitivity to visible light High carrier mobility Fast response Tissue equivalent No correction on the dose determination

3 Strong bonds High sensitivity Small dimensions and then high resolution High Radiation Hardness....moreover It is particularly indicated for measurements in regions of high radiation field gradient Proton beams... IMRT....IMPT

4 PTW NATURAL DIAMOND DE BEERS CVD DIAMOND FILM Irradiation with 62 AMeV proton beams from a superconducting cyclotron used for the treatment of ocular melanoma : CATANA facilityCATANA facility Nominal current [nA]4 Dose rate range [Gy/min] Dose range [Gy] Our attention has been placed towards two different diamond detectors

5 20 mm 7.3mm Sensitive area:4.3/4.5 mm 2 Sensitive volume:1.3/1.4 mm 3 Thickness of sensitive volume:0.30/0.31 mm Operating bias:100 V In photon and electron beams the relative differences have been studied and already published (see De Angelis C et al. Med. Phys. 2002; 29(2): ) In proton beams the measured repeatability is 0.1% PTW NATURAL DIAMOND

6 100 Dark current [pA] 16 Sensitive surface [mm 2 ] 6,4 Sensitive volume [mm 3 ] 0,4 Thickness of sensitive volume [mm] Operating bias [V] 400 DE BEER CVD DIAMOND Charge and current measurements from four electrodes V sens is 1,6 mm 3

7 For the characterization of each detector has been paid attention to: I – V characteristic Preirradiation Effects Dose linearity Dose rate effects LET Dependence Relative dose distribution measurements

8 DARK CURRENT AT 100 V Specific resistance 2,7 * cm Specific resistance 11,3 * cm CVD diamond 9 pA Natural diamond 2,5 pA SIGNAL TO NOISE RATIO AT 100 V CVD diamond 5000 Natural diamond 1000

9 I – V CHARACTERISTICS CVD Natural

10 CURRENT RESPONSE AND PREIRRADIATION (PUMPING EFFECTS) 3,5% after 15 Gy and 50 % increase 0,1 % after 15 Gy and 8 % fall off

11 DOSE LINEARITY Specific sensitivity 7,5 nC/CGy*mm 3 CVD Specific sensitivity 0,64 nC/CGy*mm 3 Natural

12 DOSE RATE EFFECTS CVD Decrease: 4 % for natural 13 % for CVD

13 Fower describes the dose rate linearity as DOSE RATE EFFECTS From which Recombination time decreases with dose rate Number of electron-hole pairs inside the material F

14 IF WE EXPRESS THE INDUCED CONDUCTIVITY AS = 0.5 is expected for a pure material with no traps or for high excitation rate = 1 for low excitation rate So for high recombination rate we expect < 1 due to the lower recombination time DOSE RATE EFFECTS

15 Fitting our experimental data with the semi-empirical formula: 6 MV Photon 250 kV X-Ray 62 AMeV proton DOSE RATE EFFECTS

16 THE RECOMBINATION TIME RESULTS =5,9 ns For the CVD diamond =1 ns For the natural diamond And this justifies the higher sensitivity of CVD detector

17 DEPTH DOSE PROFILES Pure Bragg peak SOBP

18 Lateral Penumbra 1mm 90/50 Ratio 0.89 TRANSVERSAL PROFILES

19 CONCLUSION Preirradiation LET and Dose-rate dependence (to investigate deeper) Good linearity with absorbed dose Good radiation hardness High sensitivity for the CVD LOW response time (rise time of 2 s)


Download ppt "NATURAL AND CVD TYPE DIAMOND DETECTORS AS DOSIMETERS IN HADROTHERAPY APPLI CATIONS Cirrone G.A.P., Cuttone G., Raffaele L., Sabini M.G., De Angelis C.,"

Similar presentations


Ads by Google