2nd NoRHDia workshop, GSI 2005 Monika Rębisz Bernd Voss Synthetic diamonds for heavy-ion therapy dosimetry
2nd NoRHDia workshop, GSI 2005
Monika Rębisz
Bernd Voss
Synthetic diamonds for heavy-ion
therapy dosimetry
2nd NoRHDia workshop, GSI 2005
Outline
Why CVD diamonds?
Motivation & Aim
Online monitoring High-speed single-particle beam monitor
Offline monitoring Thermo-Luminescent Detector
Detectors, Electronics and Equipment
Principles of operation
In-beam tests - results and discussion
Summary and Outlook
2nd NoRHDia workshop, GSI 2005
Why CVD Diamond? – Beam Monitor Concepts
– High drift velocity + short charge lifetime
– short pulses (ns) ‘’rise time & duration’’
– good time resolution for high-speed counting
– „Simple“ operation because of broad 5.5 eV band
– gap no cooling or pn junction is needed
– Radiation hard ~1015 particles/cm2
– Carbon low Z=6
– beam quality preserved
– biocompatible
– Actual size possible up to 12 cm ø wafers (nanoCVD larger size possible)
2nd NoRHDia workshop, GSI 2005
Motivation & Aim
Online monitoring High-speed single-particle beam monitor
Avoid the need for daily calibration of the gaseous monitor detector in terms of ‘particles
per monitor unit’
Measure intensity & structure of the extracted beam by counting individual particles
close to the GHz/channel-range
Offline monitoring Thermoluminescent diamond detector
Dose verification after irradiation
Mostly outside the beam (Dose ≈ 0) very sensitive material needed
Standard TLD material (LiF) shows low efficiency to HI - fast local saturation
CVD better candidate?
2nd NoRHDia workshop, GSI 2005
Detectors & Parameters
Sample
name
Size
[mm2]
Thickness
[µm]
# Pad Pad size
[mm2]
B 20 × 20 95 16 17.64
D1 10 × 10 100 21 2.01
D2 10 × 10 100 21 8.04
S6 10 × 10 500 1 63.6
L3 10 × 10 124 1 63.6
NCD ~ 1.2 60 21 4.15
Sample name Size
[mm2]
Thickness
[µm]
Producer
TM 3.6 × 3.6 385 e6
PC 3.6 × 3.6 359 e6
OP 3.6 × 3.6 355 e6
EL 3.6 × 3.6 370 e6
BEL 3.1 × 3.1 560 LUC Belgium
HPHT1 10.38 255 IMP Russia
HPHT2 7.84 359 IMP Russia
HPHT3 6.63 230 IMP Russia
Pixel area: 0,2 – 16 mm2
2nd NoRHDia workshop, GSI 2005
Detectors & Parameters
-5 -4 -3 -2 -1 0 1 2 3-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
EL 100 m
Cr/Au
Ti/Pl/Au
Da
rk c
urr
en
t (n
A/m
m2)
E (V/m)
Electric field = 1V/µm
I-V characteristics (D1 , D2)
2nd NoRHDia workshop, GSI 2005
What about fast read-out electronics?
Already existing fast "commercial" electronics:
DBA – Diamond Broad-Band Amplifier designed specially for diamond at GSI
- Various types : DBA II; III ; IV
- Low noise, remote controlled gain for DBA III and IV
- Analogue output signal,
- Band width 2.3 - 2.1 GHz
Quite good for heavy ion (high signal) beam monitoring
Only single channel read-out
Pick-up noise relatively high
Development of new fast multi-channel electronics:
NINO card prototype designed for ToF ALICE project,
- Differential read-out of 24 channels per card
- Digital signal
Modifications:
Differential input elimination of pickup noise
- Further modification in progress
2nd NoRHDia workshop, GSI 2005
Experiments & Beam Parameters
SIS UNILAC
Energy
80-430 MeV/u 12C
Therapeutic
conditions –
Scanning
beam
11,4 MeV/u 12C, 10.2 MeV/u 48Ca, 8.3 MeV/u 54Cr, 7.6 MeV/u 152Sm, 5.8 MeV/u
…
… Beam
size
4 -10 mm (FWHM)
3 × 3 cm2
10 × 10 cm2
45 mm Ø
Intensity 106 -108 ions/second
2.8×104 -2.6×107 ions/cm2
104-105 ions/second/mm2
Operation Transmission mode Stopping mode
Aims Feasibility test
DBA Reduce pickup noise bipolar
NINO 1.test unipolar bipolar
2nd NoRHDia workshop, GSI 2005
Setup
CR39
Intensity = const (x,y)
Field = 16 cm2
Intensity ≠ const
Field = 9 cm2
e
h
D
GND
-HV
12C
+HV
GND
SIS UNILAC
NINO /
DBA
2,3 GHz
Phillips
708
300MHz
Counter
300 MHz
80 mV 800 mV
256 irradiation points
Ø 2,2 – 8,8 mm
20 m
2nd NoRHDia workshop, GSI 2005
Results
-1.0x10-8 0.0 1.0x10
-82.0x10
-83.0x10
-8
-0.01
0.00
0.01
0.02
Pu
lse
he
igh
t [V
]
time [s]
DBA III
E=253 MeV/amu
1ns
-2.0x10-8
-1.0x10-8 0.0 1.0x10
-82.0x10
-83.0x10
-8
-0.08
-0.06
-0.04
-0.02
0.00
Pu
lse
he
igh
t [V
]
time [s]
NINO
E=253MeV/amu
1.9 ns
1st beam time – set-up of first electronics with unipolar readout
16 Pixel detector 150μm 12C E=253 MeV/u SIS
High pick-up noise with DBA III, better for NINO (even with unipolar input)
2nd NoRHDia workshop, GSI 2005
Results
DBA IV NINO
Single shots, unipolar read-out
Pulse area ~ QC Pulse with ~ QC
16 Pixel detector 150μm 48Ca E=8,3 MeV/u UNILAC
Double
hits ?
Near
Threshold
2nd NoRHDia workshop, GSI 2005
Results
Pulse width – charge dependency for adapted NINO
10 20 30 40 50 60 70 80 90 100 110 120 130
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
Pu
ls W
idth
(n
s)
Charge (fC)
Treshold vol. =26mV
Histeresis vol.=1.41V
2nd NoRHDia workshop, GSI 2005
Results
NINO card
Digital signal
after Philips 708
discriminator
Original signal
Th=30mV
Pileup problem Only 1 pulse is counted
Lecroy11.jpg
Double pulse width
-Pulse splitter used
½ original signal
from NINO
1 Pixel L3-GSI 124μm 12C E=10,2 MeV/u UNILAC
2nd NoRHDia workshop, GSI 2005
Results
2.0x106
4.0x106
6.0x106
8.0x106
2.0x106
4.0x106
CV
D L
3 [
pa
rtic
les
/cm
2s]
IC [particles/cm2s]
1 Pixel L3-GSI 124μm 12C E=10,2 MeV/u UNILAC
NINO card
30 mV threshold
Phillips 708
300 MHz discriminator
30 mV threshold
Too large pixel
Multi hits
2nd NoRHDia workshop, GSI 2005
Results
Trigger Threshold
Single Pixel detector L3 GSI 124μm 152Sm E=5,8 MeV/u UNILAC
Moving baseline
Loss of counting rate (?)
Baseline restorage needed
Discriminator Threshold
2nd NoRHDia workshop, GSI 2005
Results
104
104
105
D1 2.01 mm2
# c
ou
nts
[particles / mm2]
D2 8.04 mm2
105
105
106
116 MeV/u
expected
89 MeV/u
Pixel detectors D1, D2 100μm 12C E=80-430 MeV/u SIS
efficiency 89
MeV D1
89
MeV
D2
116Me
V D1
116Mev
D2%
94 83 94 83
93 84 89 81
88 79 80 73
85 75 73 65
83 73 65 58
81 70 61 54
77 67 57 50
76 67 55 48
74 64 53 46
efficiency 89
MeV D1
89
MeV
D2
116Me
V D1
116Mev
D2%
75 64 57 48
88 79 71 65
84 76 63 57
79 70 55 50
77 68 51 45
78 70 49 44
74 66 48 42
77 69 46 40
74 64 46 40
Missing counting efficiency due to electronics
200400
600800
1000
2
4
6
8
10
12
14
16
18
20
0
1000
2000
3000
4000
5000
Tem
pera
ture
[°C]
TL
in
ten
sit
y [
a.u
.]
Wavelentgh [nm]
2nd NoRHDia workshop, GSI 2005
Optical measurements
Emission spectra of IMO and PC samples after 1.2 kGy X-ray irradiation
HR= 2 °C / sec
PC
6
0
200 400 600 800 1000 1200
0
2000
4000
6000
Wavelength [nm]
TL
in
ten
sit
y (
a.u
.)
BEL
BEL+background
background
after 25min solar lamp ilumination
(=25 min x 20 intensity of day light)
60
460
280
400
495 675
200
4000 3500 3000 2500 2000 1500 1000 500
0
1
2
3
4
5
6
C
HPHT1 255m
HPHT2 359m
HPHT3 230m
SCVD
A
cm-1
A
2nd NoRHDia workshop, GSI 2005
Optical measurements
IR absorption spectra of 3 different HPHT samples
2nd NoRHDia workshop, GSI 2005
Optical measurements
IR absorption spectra of 3 different HPHT samples
Nitrogen pairs “A”
dominant in TL
SCVD not useful for TL
4000 3000 2000 1000
0.1
0.2
0.3
0.4
HPHT1 255m
HPHT3 230m
SCVD
C
A
A
cm-1
2nd NoRHDia workshop, GSI 2005
Offline monitoring - TLD
50 100 150 200 250
0
5
10
15
20 PC
TM
LiF:Mg,Ti (MTS-N)
TL
in
ten
sit
y [
a.u
.]
Temperature [°C]
Typical TL glow curves
irradiation with C ions (350MeV/u)
Dose up to 2 Gy
3 HPHT diamond detectors
irradiation with Au ions (11.4MeV/u)
dose 2.2 kGy and 30 kGy
100 200 300 400
0
100
200
300
400
E=11.1MeV/u Fluency=1.45*108 par/cm
2 Dose=2.2 kGy
HPHT2
HPHT3
E=11.1MeV/u Fluency=2*109 par/cm
2
Dose=30 kGy
HPHT1
HPHT2
HPHT3
TL
sig
na
l [a
.u.]
Temperature [°C]
2nd NoRHDia workshop, GSI 2005
Offline monitoring - TLD
1 10
101
102
103
104
105
106
107
HPHT 2
HPHT 3
EL
OP
TM
PC
BEL
LiF MTS-N
TL
sig
na
l [a
.u]
Dose [Gy]
60
Linearity test with X-rays
Good up to 60 Gy
TM, PC, HPHT
2nd NoRHDia workshop, GSI 2005
Offline monitoring - TLD
1 10
100
1000
10000 TM 10.8MeVu
PC 350MeVu
LiF X-ray 250kV,1mA scale1/50
Tl
inte
ns
ity
[a
.u.]
Dose [Gy]Efficiency η
Sample type 350 MeV/u 11.4 MeV/u
PC 100% 32%
TM 100% 41%
LiF (MTS-N) 100% 9%
Efficiency of pCVD diamonds and LiF (MTS-N) detector for different species and energy regimes
Efficiency
The efficiency η was derived
according to equation (1) where
TLHI and TLX are the integral
light sum of detectors irradiated
with heavy ions (HI) and X-rays
(X) respectively.
%100
)/(
/
DTL
DTL
X
HI
! Efficiency of TL diamond
detectors to HI better than
for standard TLD material
2nd NoRHDia workshop, GSI 2005
Summary & Outlook (online)
• Various poly-CVD diamond detectors tested
• First results on NanoCrystalineDiamond sample
• Various ion spezies & energies used
• Fast single channel & muliti-channel electronics tested
• Achieved promising results for online beam-diagnostics for HI
- double hits (UNILAC) more & smaller pixels
- Results depending on detector quality investigation on detector ‘grade’,
preparation, contacts
- electronics noise limits resolution bipolar readout (NINO) necessary,
work on DBA
- best choice: SC CVD membrane < 100µm, 200 × 200 mm2
2nd NoRHDia workshop, GSI 2005
Summary & Outlook (offline)
• Various poly-CVD and HPHT diamond detectors tested
• Different ion spezies & energies used
• Readout done with commercial equipment optimization of annealing- & readout-
parameters & procedure necessary
• Achieved very promising results for offline beam-diagnostics for all measured HI
- Efficiency higher than for LiF
- Linearity up to 60 Gy detailed investigations on dose- &
dose-rate dependency necessary
- Results depending on detector quality investigation on different batches &
‘grades’ necessary
- Results scatters in one batch dependency on history, annealing
needed
- Best results with material grade PC and TM more investigation with different ion species end energies
investigation of mixed field conditions
TSC investigation planed