NATURAL%20AND%20CVD%20TYPE%20DIAMOND%20DETECTORS%20AS%20DOSIMETERS%20IN%20HADROTHERAPY%20APPLI%20CATIONS

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
Low dark current and low sensitivity to visible
light
Fast response
No correction on the dose determination
3
....moreover
Small dimensions and then high resolution
High Radiation Hardness
4
Our attention has been placed towards two
different diamond detectors

• 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 facility
Nominal current nA 4 Dose rate range
Gy/min 2 - 15 Dose range Gy 2 - 20
5
PTW NATURAL DIAMOND

• Sensitive area 4.3/4.5 mm2
• Sensitive volume 1.3/1.4 mm3
• 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) 248-254.)
• In proton beams the measured repeatability is
  0.1

6
DE BEER CVD DIAMOND
Thickness of sensitive volume mm
0,4
Sensitive volume mm3
6,4
16
Sensitive surface mm2
Dark current pA
100
Operating bias V
400
Charge and current measurements from four
electrodes
Vsens is 1,6 mm3
7
For the characterization of each detector has
been paid attention to
I V characteristic
Preirradiation Effects
Dose linearity
Relative dose distribution measurements
Dose rate effects
LET Dependence
8
DARK CURRENT AT 100 V
Specific resistance 2,7 1014 ? cm
Specific resistance 11,3 1014 ? cm
9
I V CHARACTERISTICS
10
CURRENT RESPONSE AND PREIRRADIATION (PUMPING
EFFECTS)
11
DOSE LINEARITY
12
DOSE RATE EFFECTS
13
DOSE RATE EFFECTS
Fower describes the dose rate linearity as
From which
14
DOSE RATE EFFECTS
IF WE EXPRESS THE INDUCED CONDUCTIVITY AS
So for high recombination rate we expect ? lt 1
due to the lower recombination time
15
DOSE RATE EFFECTS
Fitting our experimental data with the
semi-empirical formula
62 AMeV proton
6 MV Photon
62 AMeV proton
250 kV X-Ray
16
THE RECOMBINATION TIME RESULTS
? 5,9 ns
For the CVD diamond
For the natural diamond
? 1 ns
And this justifies the higher sensitivity of CVD
detector
17
DEPTH DOSE PROFILES
18
TRANSVERSAL PROFILES
Lateral Penumbra 1mm
90/50 Ratio 0.89
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)