Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Diamond as a solid state micro-fission chamber for thermal neutron detection
Michal Pomorski CEA-LIST , Diamond Sensors Laboratory, France
3rd ADAMAS Collaboration Meeting @ ECT* 18-20 November, 2014
Trento
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Co-Authors
Co-Authors (CEA Saclay):
Christine Mer-Calfati Francois Foulon
Many thanks to VR1 reactor team in Prague:
Lubomir Sklenka Tomas Bily Jan Rataj
and others…..
open access facility: [email protected]
request form: reactorvr1.eu/download/request_for_access.pdf
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
❑ Motivation / Previous work
❑ Diamond Samples / Pre-testing
❑ Set-up ❑ VR1 reactor in Prague ❑ U-235 + diamond detectors + electronics
❑ Some results ❑ fission fragments spectra ❑ linearity with flux, core-mapping ❑ TCT signals + other observations……
❑ Summary
Outline
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Motivation/Previous workneutron detection with diamond detectors
Dia
mo
nd
De
tecto
rs Ltd
Dia
mo
nd
De
tecto
rs Ltd
Bergonzo et al.
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Motivation/Previous workthermal neutron detection
otherwise mentioned. (In one sample, 5% of HDPE wasadded to a Al2O3:C and 6LiF mixture to increase thestrength of the pellet. In this case, HDPE was not usedas a neutron converter, but because of the mechanicalproperties.) The dimensions of the pellets are !6.4 mm indiameter and !0.5 mm of thickness. Before irradiationthe dosimeters were zeroed by bleaching with a light froma halogen lamp filtered by a yellow Kopp 3-69 filter.
2.2. Irradiation facilities
An uncalibrated Pu–Be source was used for initial com-parison of the neutron response for various mixtures ofAl2O3:C with neutron converters. The source is mountedinside a container filled with paraffin used for moderatingthe neutrons. For the irradiations, the samples were placedin a holder and introduced inside the paraffin container.Since the actual spectrum and dose rate at the sample posi-tion are unknown, this source was used exclusively to com-pare the properties of different materials or samples.Typical neutron spectrum of a Pu–Be source can be foundin [6,19].
Neutron irradiations were also performed at the SCK-CEN (Belgium Nuclear Research Institute) using a bare252Cf source traced to primary standard in UK NationalPhysics Laboratory (NPL). The SCK-CEN irradiationfacility is described in [20]. The dimensions of the roomare 6 m · 6 m · 3.5 m (height). During irradiation, thesource is positioned in one of the corners, at 1.4 m fromthe walls and 1.2 m from the floor. A 30 cm · 30 cm ·15 cm PMMA phantom was installed in the diagonal ofthe room, the side facing the source located at 75 cm or1.5 m from the 252Cf source, depending on the experiment.The dosimeters were centered on the face of the phantomthat is oriented towards the source, no less than 10 cm fromthe edge of the phantom. The dosimeters and the center ofthe phantom were at the same height as the source. Thedose equivalent rates were 6.9 mSv h"1 and 1.7 mSv h"1
at 75 cm and 1.5 m from the source, respectively, not con-
sidering the contribution from room scattering. The uncer-tainty on these values is of the order of 4% (1r interval).The typical spectrum of a 252Cf source is given by ISO8529-1 [21] and the spectrum of the source in the calibra-tion room simulated by Monte Carlo is given in [20]. Thephoton dose equivalent for a bare 252Cf source is !5% ofthe neutron dose equivalent [22]. All reported neutrondoses are personal dose equivalent at a depth of 10 mm,Hp(10).
The contribution of room scattering to the dosimeterreading was evaluated using the shadow cone technique[23]. The shadow cone from SCK-CEN consists of a 20-cm long front end made of iron followed by a 30-cm longboron-loaded polyethylene section [20]. The diameter ofthe shadow cone increases linearly from 3.5 cm on the sidefacing the source to 15 cm on the opposite side. With thephantom at 1.5 m from the source, the cone cast a shadowthat covers the 30 cm · 30 cm phantom almost completely,except for the outermost part of the corners. For near doseequivalent ambient neutron monitors, like the Studsvik2202D, the response due to scattered radiation is 33% ofthe total response [20].
Additional irradiations were performed with a 60Cogamma source at SCK-CEN, traced to primary standardfrom the Physikalisch-Technischen Bundesanstalt (PTB),Germany.
2.3. OSL readout
The OSL readouts were carried out using an automatedRisø reader TL/OSL-DA-15 [24] equipped with greenLEDs (broad band emission centered at 525 nm) for opticalstimulation, a bi-alkali PMT (model 9235QB from ElectronTubes, Inc.) for light detection and an integrated 90Sr/90Ybeta source for additional irradiations. For the OSLmeasurements, Hoya U-340 filters (7.5 mm thickness, trans-mission between 290 and 390 nm) were used in front ofthe PMT to discriminate the luminescence against thestimulation light. For TL measurements of TLD-600 andTLD-700 detectors, BG-39 filters (8.0 mm thickness, trans-mission between 340 and 600 nm) were used in front of thePMT.
The OSL readout sequence consisted first of stimulatingthe crystal for 600 s to measure the OSL curve of the irra-diated dosimeter. This was followed by irradiation withthe reference dose from 90Sr/90Y source and anotheroptical stimulation for 600 s to measure the OSL curveproduced by the reference irradiation. The first and thesecond OSL curves were integrated over the 600 s ofoptical stimulation to obtain respectively S and SR, whereS is the OSL signal produced by the radiation field to bemeasured and SR is the OSL signal produced by the refer-ence irradiation. The reference irradiation was used toaccount for variations in the dosimeter mass or intrinsicsensitivity. In all cases the background signal due toPMT dark counts was subtracted from the total measuredOSL signal.
Table 1Main isotopes used as neutron converters in luminescence detectors andcorresponding natural abundance, thermal neutron cross-section andproducts [6,9]
Isotope Naturalabundance(%)
r*
(barns)Products
6Li 7.4 940 3H (2.75 MeV) + 4He (2.05 MeV)
10B 19.8 3840 7Li (1.0 MeV) + 4He (1.8 MeV)7Li (0.83 MeV) + 4He (1.47 MeV)+ c (0.48 MeV)
157Gd 15.7 255,000 158Gd + cs + conversion e"
+ X-rays (29–182 keV)
155Gd 14.8 60,900 156Gd + cs + conversion e"
+ X-rays (39–199 keV)
J.C.R. Mittani et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 663–671 665
Dia
mo
nd
De
tecto
rs Ltd
Dia
mo
nd
De
tecto
rs Ltd
http://www-norhdia.gsi.de/talks/4th/G_Verona-Rinati.pdf
Single crystal CVD diamond neutron detectors in a p-type/intrinsic/metal layered structure - Gianluca Verona-Rinati, Uni Roma Tor Vergata
Dia
mo
nd
De
tecto
rs Ltd
Dia
mo
nd
De
tecto
rs Ltd
http://www-norhdia.gsi.de/talks/4th/G_Verona-Rinati.pdf
Dia
mo
nd
De
tecto
rs Ltd
Dia
mo
nd
De
tecto
rs Ltd
http://www-norhdia.gsi.de/talks/4th/G_Verona-Rinati.pdf
otherwise mentioned. (In one sample, 5% of HDPE wasadded to a Al2O3:C and 6LiF mixture to increase thestrength of the pellet. In this case, HDPE was not usedas a neutron converter, but because of the mechanicalproperties.) The dimensions of the pellets are !6.4 mm indiameter and !0.5 mm of thickness. Before irradiationthe dosimeters were zeroed by bleaching with a light froma halogen lamp filtered by a yellow Kopp 3-69 filter.
2.2. Irradiation facilities
An uncalibrated Pu–Be source was used for initial com-parison of the neutron response for various mixtures ofAl2O3:C with neutron converters. The source is mountedinside a container filled with paraffin used for moderatingthe neutrons. For the irradiations, the samples were placedin a holder and introduced inside the paraffin container.Since the actual spectrum and dose rate at the sample posi-tion are unknown, this source was used exclusively to com-pare the properties of different materials or samples.Typical neutron spectrum of a Pu–Be source can be foundin [6,19].
Neutron irradiations were also performed at the SCK-CEN (Belgium Nuclear Research Institute) using a bare252Cf source traced to primary standard in UK NationalPhysics Laboratory (NPL). The SCK-CEN irradiationfacility is described in [20]. The dimensions of the roomare 6 m · 6 m · 3.5 m (height). During irradiation, thesource is positioned in one of the corners, at 1.4 m fromthe walls and 1.2 m from the floor. A 30 cm · 30 cm ·15 cm PMMA phantom was installed in the diagonal ofthe room, the side facing the source located at 75 cm or1.5 m from the 252Cf source, depending on the experiment.The dosimeters were centered on the face of the phantomthat is oriented towards the source, no less than 10 cm fromthe edge of the phantom. The dosimeters and the center ofthe phantom were at the same height as the source. Thedose equivalent rates were 6.9 mSv h"1 and 1.7 mSv h"1
at 75 cm and 1.5 m from the source, respectively, not con-
sidering the contribution from room scattering. The uncer-tainty on these values is of the order of 4% (1r interval).The typical spectrum of a 252Cf source is given by ISO8529-1 [21] and the spectrum of the source in the calibra-tion room simulated by Monte Carlo is given in [20]. Thephoton dose equivalent for a bare 252Cf source is !5% ofthe neutron dose equivalent [22]. All reported neutrondoses are personal dose equivalent at a depth of 10 mm,Hp(10).
The contribution of room scattering to the dosimeterreading was evaluated using the shadow cone technique[23]. The shadow cone from SCK-CEN consists of a 20-cm long front end made of iron followed by a 30-cm longboron-loaded polyethylene section [20]. The diameter ofthe shadow cone increases linearly from 3.5 cm on the sidefacing the source to 15 cm on the opposite side. With thephantom at 1.5 m from the source, the cone cast a shadowthat covers the 30 cm · 30 cm phantom almost completely,except for the outermost part of the corners. For near doseequivalent ambient neutron monitors, like the Studsvik2202D, the response due to scattered radiation is 33% ofthe total response [20].
Additional irradiations were performed with a 60Cogamma source at SCK-CEN, traced to primary standardfrom the Physikalisch-Technischen Bundesanstalt (PTB),Germany.
2.3. OSL readout
The OSL readouts were carried out using an automatedRisø reader TL/OSL-DA-15 [24] equipped with greenLEDs (broad band emission centered at 525 nm) for opticalstimulation, a bi-alkali PMT (model 9235QB from ElectronTubes, Inc.) for light detection and an integrated 90Sr/90Ybeta source for additional irradiations. For the OSLmeasurements, Hoya U-340 filters (7.5 mm thickness, trans-mission between 290 and 390 nm) were used in front ofthe PMT to discriminate the luminescence against thestimulation light. For TL measurements of TLD-600 andTLD-700 detectors, BG-39 filters (8.0 mm thickness, trans-mission between 340 and 600 nm) were used in front of thePMT.
The OSL readout sequence consisted first of stimulatingthe crystal for 600 s to measure the OSL curve of the irra-diated dosimeter. This was followed by irradiation withthe reference dose from 90Sr/90Y source and anotheroptical stimulation for 600 s to measure the OSL curveproduced by the reference irradiation. The first and thesecond OSL curves were integrated over the 600 s ofoptical stimulation to obtain respectively S and SR, whereS is the OSL signal produced by the radiation field to bemeasured and SR is the OSL signal produced by the refer-ence irradiation. The reference irradiation was used toaccount for variations in the dosimeter mass or intrinsicsensitivity. In all cases the background signal due toPMT dark counts was subtracted from the total measuredOSL signal.
Table 1Main isotopes used as neutron converters in luminescence detectors andcorresponding natural abundance, thermal neutron cross-section andproducts [6,9]
Isotope Naturalabundance(%)
r*
(barns)Products
6Li 7.4 940 3H (2.75 MeV) + 4He (2.05 MeV)
10B 19.8 3840 7Li (1.0 MeV) + 4He (1.8 MeV)7Li (0.83 MeV) + 4He (1.47 MeV)+ c (0.48 MeV)
157Gd 15.7 255,000 158Gd + cs + conversion e"
+ X-rays (29–182 keV)
155Gd 14.8 60,900 156Gd + cs + conversion e"
+ X-rays (39–199 keV)
J.C.R. Mittani et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 663–671 665
Only one publication with FF and natural diamond (half page) ~ 1970… +previous work of Christine Mer et. al. thick pcCVD+EGscCVD + high power reactor
Idea: Use of fissile material as a converter eg.: Uranium-235 —> 584 barns for fission
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
.Diamond Samples
Optical Grade scCVD e6 (OGscCVD) p+-intrinsic-metal structure CEA (PIM)
[N0] =< 1ppm thickness = 17 microns size= 3 x 3 mm (broken) contacts = Al (1mm diam.)
[N0] << 1ppm thickness ~ 20 microns (intr.) size= 3 x 3 mm contacts = Cr/Au (<1mm diam.)
Cr(50nm)/Au(100nm)
intrinsic scCVD
p+-B dopedCVD(1micron)HPHT
OG scCVD
Al (100nm)
Al (100nm)
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Alpha SpectraLaboratory Pre-testing
0 200 400 6000.0
0.2
0.4
0.6
0.8
1.0
1.2
direct 5m BNC
counts/max
channel no.
PiM @ +30 V (1.5 V/µm)
479
0 200 400 6000.0
0.2
0.4
0.6
0.8
1.0
1.2
direct 5m BNC
counts/max
channel no.
opt. scCVD ~17µm @ +170 V(10V/µm)
468
Am-241 alpha spectra 5.486 MeV in vacuum, using CSA (3micros shaping)
OGscCVD PiM
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
AlphaTCTLaboratory Pre-testing
-20 0 20 40 60 80
0.0
0.1
0.2
0.3
optscCVD @ 170 V PiM @ 30 V
sign
al @
50
Ohm
[V]
time [ns]
TCT (50 Ohm) from 5.48 MeV alphas, CIVIDEC
-2 -1 0 1 2 3 4 50.0
0.1
0.2
0.3
optscCVD @ 170 V
sign
al @
50
Ohm
[V]
time [ns]
TCT (50 Ohm) from 5.48 MeV alphas, CIVIDEC
-20 0 20 40 60 80
0.00
0.05
PiM @ 30 V
sign
al @
50
Ohm
[V]
time [ns]
TCT (50 Ohm) from 5.48 MeV alphas, CIVIDEC
PiM, Claudio Verona Tor Vergata Univ.Rome
buried p+
buried p+
0 5 10 15 200.0
0.1
0.2
0.3
0.4
0.5
0.6
sign
al a
mpl
itude
on
50 O
hm [V
]
time [ns]
TCT signals
laser power
25%
p+ on top
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
VR1 reactor in Prague
VR1 in-core fluxes correspond to external for HP reactors
- low power research reactor (max 1kW, 1^10 n/cm2s@500W) - light water (reflector, shielding, cooling) - no thermal effects….
diamond detectors
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
U-235 + Diamond Detectors + Electronics
U-235
17microns OG scCVD 20 microns PIM scCVD
thermal neutrons
5m of BNC
in-core
CSA CSA
DAQ DAQ
fission fragments
bias voltages on read-out electrodes: OGscCVD +170V(10V/micron) (h-drift) PiM + 30V(~1.5V/micron) (h-drift)
PiM
OGscCVD
Emplacement pastille d’uranium
Emplacement collimateur
quantité de matière activable doit donc être limitée dans le dispositif pour qu’à l’issu des irradiations sous ULYSSE, le temps de désactivation (lié à la période radioactive du matériau) ne soit pas trop élevé.
V-1 Préparation des diamants et des convertisseurs
Les contacts en or (utilisés pour la caractérisation sous alpha) des diamants pré-caractérisés sont dissous (à l’aide d’une eau régale) puis redéposés par évaporation afin d’obtenir des plots de même surface.
Une couche de bore de 600 µm est déposée par évaporation au dessus d’une majeure partie du plot en or du diamant monocristallin T8 et du diamant CVD1 pour le diamant polycristallin. La partie du plot sans bore permettra de relier le fil en or afin de polariser le diamant. L’uranium ne peut pas être déposé par évaporation en raison de sa radioactivité. Il se présente sous forme de pastille sur laquelle est réalisé un dépôt d’uranium. La pastille est entourée de plastique, seul le dépôt est à nu.
FIG : Pastille d’uranium
Un support en téflon (non activable) à deux étages est réalisé pour le diamant T8 permettant de positionner un collimateur et la pastille d’uranium au dessus du diamant. Un autre support à un seul étage, pour la pastille d’uranium, est réalisé pour le détecteur CVD2. Le collimateur permettra de collimater les fragments de fission issus de l’uranium pour le diamant monocristallin. En revanche, pour les diamants associés au bore, les neutrons ne peuvent pas être collimatés.
FIG : Support en téflon
V-2 Montage du boîtier
Les boîtiers sont en graphite (non activable), munis de deux trous pour pouvoir faire passer les câbles dénudés amenant la haute tension (HT) et permettant de récupérer les impulsions. Les diamants sont collés avec de la pâte à l’argent sur une plaque de circuit imprimé. Des « protections » en téflon sont positionnées sous le fil d’or pour éviter que celui-
U-235
1 cm
no collimator used
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
U-235 + Diamond Detectors + Electronics
+ alpha decay with 4.679 MeV
U-235 fission
after 5mm air (rough estimation) ~80 MeV Kr (~110 MeV) ~35 MeV Ba (~60 MeV)
17 microns 17 microns
Ba-56@60MeV Kr-36@110MeV
average energy to fission fragments ~170 MeV
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Fission Fragments Spectra
0 200 400 600 800 10000.0
0.2
0.4
0.6
0.8
1.0
1.2
OGscCVD PIM
norm
aliz
ed c
ount
s
channel number
lighterFF heavierFF
lighterFF/higherE
heavierFF/lowerE
average energy to fission fragments
~170 MeV
gamma bckg.
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Fission Spectra with Increasing Power
0 200 400 600 800 1000100
101
102
103
104
105
500 W 100 W 10 W 1 W 0.1 W 0.01 W
counts/channel
ADC channel number0 200 400 600 800 1000
100
101
102
103
104
105 0.01 W 0.1 W 1 W 10 W 100 W 500 W
counts/channel
ADC channel number
OGscCVD PiM
alpha-peak@~4.679MeV100W ~ 2E9 n/cm2.s (core center)~ 10 min acquisition time
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Linearity with Flux
104 105 106 107 108 10910-2
10-1
100
101
102
103
diam
ond
dete
ctor
[cps
]reactor diagnostics [cps]
Equation y = a + b*x
Weight No Weighting
Residual Sum of Squares
5.1638E-4
Pearson's r 0.99998
Adj. R-Square 0.99996Value Standard Error
DIntercept -5.50928 0.01886Slope 1.00538 0.00283
σ0.3%R20.9999
104 105 106 107 108 109
10-1
100
101
102
103
diam
ond
dete
ctor
[cps
]
reactor diagnostics [cps]
Equation y = a + b*x
Weight No Weighting
Residual Sum of Squares
0.00337
Pearson's r 0.99989
Adj. R-Square 0.99973Value Standard Error
D1Intercept -5.10035 0.04817Slope 0.98325 0.00724
threshold @ 200 ch
σ0.7%R20.9997
OGscCVD PiM
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Core-Mapping
0
10
20
30
40
50
60
70
80
0.0 5.0x103 1.0x104 1.5x104 2.0x104
integrated counts diamond detector
dist
ance
from
the
chan
nel b
otto
m [c
m]
0
10
20
30
40
50
60
70
80
0.0 4.0x103 8.0x103 1.2x104
integrated counts diamond detector
dist
ance
from
the
chan
nel b
otto
m[c
m]
PiMOGscCVD@100W
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Core-Mapping
0
10
20
30
40
50
60
70
0.0 0.2 0.4 0.6 0.8 1.0counts normalized @ 30 cm
dist
ance
from
the
chan
nel b
otto
m [c
m]
0
20
40
60
80
100
0.0 0.2 0.4 0.6 0.8 1.0
He3 PiM OGscCVD
counts normalized @ 30 cm
dist
ance
from
the
chan
nel b
otto
m [c
m]
OGscCVD + PiM OGscCVD + PiM + He3
@100W
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Gamma Background
OGscCVD PiM
0 200 400 600 800 10001
10
100
1000
counts/channel
channel number
100 W 10 W 1W
0 200 400 600 800 10001
10
100
counts/channel
channel number
1 W 10 W 100 W
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
TCT Signals for OGscCVD
y 100mV/div ; x 10ns/div y 2mV/div ; x 5ns/div
350 MHz DSO@50 Ohm + 5m BNC
CIVIDEC 40dB amplifier no amp, just bias-T
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Priming of OGscCVDSome More Observations
0 50 100 150 2000
50
100
counts
channel number0 50 100 150 200
50
100
150
counts
channel number
γ-priming (?)
235U α-particles 4.679 MeV
OGscCVD PiM (no priming)
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Polarisation of OGscCVD@-170V majority of e-driftSome More Observations
0 200 400 600 800 1000
0
24
48
72
96
120
TAG
TAG
TAG
TAG
TAG
channel number
counts
time
0 200 400 600 800 1000 12000
50
100
150
200
250
300
350
counts/channel
channel number
e-drift
final state (stable)
strong electron trapping in OGscCVD…..
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Radiation Hardness Issue
1E14 1E15 1E1650
60
70
80
90
100
Polycristalline diamond with boron converter Polycristalline diamond with Uranium converter Single crystall diamond with Uranium converter
Rela
tive
decr
aese
of t
he p
ositi
on p
ic %
neutron fluence (neutron/cm2)
However, radiation hardness limits : Comparison of the signal loss between single crystal detector and poly X detector with neutron fluence
Æ Degradation of the homoepitaxial diamond detector at lower neutron fluences than polycristalline diamond
1- Thermal Neutron detection
U+MonoX
B+polyX
U+polyX
From previous work, Christine Mer et. al MonoX=EGscCVD ~200 microns thick
should be better for thin detectors, and even better for membranes………
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Summary and Outlook
What can be ‘easily’ improved: - sensitivity/count rate x100 —> larger samples+contact size+sandwich conf. - larger TCT signals —> better electronics, U-235 precipitation on diamond
- (Philippe talk) - better gamma/neutron ratio —> U-235 electro-precipitation on diamond - improved RH —> membrane OGscCVD, thinner i-layer = no implantation
- use of U-235 as converter material - with FF of high energy - diamond micro-fission chamber based on ‘cheap’ OG material concept proved:
- stable operation (FF up to 5kHz tested), perfect linearity - high n/gamma ratio - possibility to operate with no amps…maybe HTemp etc……
some open questions: - sensitivity, RH
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
In-core thermal neutron monitoringFirst Applications
Diamond as micro solid-state fission chamber:
U-235
17microns OG scCVD 20 microns PIM scCVD
thermal neutrons
5m of BNC
in-
CSA CSA
DAQ DAQ
fission fragments
VR1 training reactor in Prague
U-235- lower crossection, but heavy fragments large signal, better n/gamma ratio, no-amplifiaction needed
facility with open access please contact:[email protected]
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
In-core thermal neutron monitoring
average energy fission fragments
~170 MeV
0 50 100 150 200
50
100
150
coun
ts
channel number
γ-priming (?)
235U α-particles 4.679 MeV
0 50 100 150 2000
50
100
coun
ts
channel number
Fig. X. Uranium alpha peak 4.3 MeV for both detectors [left] OPT-scCVD, residual priming is visible at 1e7 alpha peak shifts right, reaching 100% CCE, similar to PIM-scCVD [right] PIM-scCVD, stable detection from the beginning no priming
0 200 400 600 800 1000
0
24
48
72
96
120
TAG
TAG
TAG
TAG
TAG
channel number
coun
ts
Z Axis
Title
0 200 400 600 800 1000 12000
50
100
150
200
250
300
350
TAG
(DES
CRIP
TIO
N)
Row Numbers
TAG
Fig. X Polarization phenomenon for OPT-scCVD, negative bias -170 V, majority of electrons drift
0 200 400 600 800 10000.0
0.2
0.4
0.6
0.8
1.0
1.2
OG diamond PIM
norm
alize
d co
unts
channel number
Fig. X Fission fragments spectra for both detectors, better performane of OPT-scCVD is evidenced, most probably due to thinner Al contacts (Au in case of PIM-scCVD) and/or high bias operation [OPT-scCVD@10V/micron, PIM-scCVD@2V/micron]
4e Gamma background
0 200 400 600 800 10001
10
100
1000
coun
ts
channel number
100 W 10 W 1W
0 200 400 600 800 10001
10
100
coun
ts
channel number
1e7 1e6 1e5
Fig. X [left] OPT-scCVD [right] PIM-scCVD
4 Transient Current signals
OPT-scCVD – optical grade e6 single crystal CVD diamond, metalized with Al ~100nm, 2 mm in diameter
front contact, 17 microns thick
PIM-scCVD – electronic grade scCVD diamond grown in the Diamond Sensors Laboartory of CEA-Saclay.
Detector’s structure includes: HPHT substrate, p+ CVD diamond layer, which serves as a back contact 1-3
microns thick, intrinsic CVD layer >14 microns(?) thick
3c electronics
- 5m cable, Amptek, A250 charge sensitive amplifier, Ortec shaper, HV voltage unit, pocket M8000
ADC
- Cividec 50 Ohm amplifier, bias T
- Bias-T 5m cable
4 Results and Discussion
4a Diamond detectors’ CPS vs. reactor power – sensitivity, linearity
Integration time (?)
0 200 400 600 800 1000100
101
102
103
104
105
500 W 100 W 10 W 1 W 0.1 W 0.01 W
coun
ts/c
hann
el
ADC channel number0 200 400 600 800 1000
100
101
102
103
104
105
coun
ts/c
hann
elADC channel number
Fig. X Diamond detectors spectra acquired with charge sensitive electronics while increasing reactor
power. [left] OPT-scCVD, [right] PIM-scCVD
104 105 106 107 108 109
10-1
100
101
102
103
diam
ond
dete
ctor
[cps
]
reactor diagnostics [cps]
Equation y = a + b*xWeight No WeightingResidual Sum of Squares
0.00337
Pearson's r 0.99989Adj. R-Square 0.99973
Value Standard ErrorD1 Intercept -5.10035 0.04817D1 Slope 0.98325 0.00724
threshold = 200 ch
0.7%
104 105 106 107 108 10910-2
10-1
100
101
102
103
diam
ond
dete
ctor
[cps
]
reactor diagnostics [cps]
Equation y = a + b*xWeight No WeightingResidual Sum of Squares
5.1638E-4
Pearson's r 0.99998Adj. R-Square 0.99996
Value Standard ErrorD Intercept -5.50928 0.01886D Slope 1.00538 0.00283
0.3%
OPT-scCVD – optical grade e6 single crystal CVD diamond, metalized with Al ~100nm, 2 mm in diameter
front contact, 17 microns thick
PIM-scCVD – electronic grade scCVD diamond grown in the Diamond Sensors Laboartory of CEA-Saclay.
Detector’s structure includes: HPHT substrate, p+ CVD diamond layer, which serves as a back contact 1-3
microns thick, intrinsic CVD layer >14 microns(?) thick
3c electronics
- 5m cable, Amptek, A250 charge sensitive amplifier, Ortec shaper, HV voltage unit, pocket M8000
ADC
- Cividec 50 Ohm amplifier, bias T
- Bias-T 5m cable
4 Results and Discussion
4a Diamond detectors’ CPS vs. reactor power – sensitivity, linearity
Integration time (?)
0 200 400 600 800 1000100
101
102
103
104
105
500 W 100 W 10 W 1 W 0.1 W 0.01 W
coun
ts/c
hann
el
ADC channel number0 200 400 600 800 1000
100
101
102
103
104
105
coun
ts/c
hann
el
ADC channel number
Fig. X Diamond detectors spectra acquired with charge sensitive electronics while increasing reactor
power. [left] OPT-scCVD, [right] PIM-scCVD
104 105 106 107 108 109
10-1
100
101
102
103
diam
ond
dete
ctor
[cps
]reactor diagnostics [cps]
Equation y = a + b*xWeight No WeightingResidual Sum of Squares
0.00337
Pearson's r 0.99989Adj. R-Square 0.99973
Value Standard ErrorD1 Intercept -5.10035 0.04817D1 Slope 0.98325 0.00724
threshold = 200 ch
0.7%
104 105 106 107 108 10910-2
10-1
100
101
102
103
diam
ond
dete
ctor
[cps
]
reactor diagnostics [cps]
Equation y = a + b*xWeight No WeightingResidual Sum of Squares
5.1638E-4
Pearson's r 0.99998Adj. R-Square 0.99996
Value Standard ErrorD Intercept -5.50928 0.01886D Slope 1.00538 0.00283
0.3%
gamma backgroundtypical spectra of fission products
varying reactor power (acq. 10min) linearity vs. reactor diagnostics
U-235 alpha 4.679 MeV
easy to optimise:
- U-235 deposition onto diamond - thinner membrane (RH, gamm/n) - larger surface, sandwiching (sens.)
First Applications
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Thanks for your attention!
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
UV 337nm laser TCT Photovoltaic Mode (zero-bias)Electronic Properties
ΔE
- - -+ +
membrane50 Ohm
laser absorbtion
DSOQE ~ 10-5UV 337nm, 2.5 ns pulse ~100µW nitrogen laser, trigger
p-doped
0 5 10 15 200.0
0.1
0.2
0.3
0.4
0.5
0.6
sign
al a
mpl
itude
on
50 O
hm [V
]
time [ns]
TCT signals
laser power
OD filters
Claudio Verona Tor Vergata Univ. Rome
0.01%
25%
metalintrinsic
p-dopedHPHT
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
PIM Membrane ‘Dosimetry’First Application
Methyl Viologen chemical dosimeter PIM membrane ‘dosimeter’
Michal Pomorski, CEA-LIST, Diamond Sensors Laboratory, ADAMAS 3rd, Trento 19/11/2014
Zero-Bias Compared to ‘Normal’ Operation (bias-T – 20V applied)First Application
-1.0x10-6 0.0 1.0x10-6 2.0x10-6 3.0x10-6
-1
0
1
2
3
4
5
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
indu
ced
curr
ent [
A]
sign
al a
mpl
itude
on
50 O
hm[V
]
time [s]
-1.0x10-6 0.0 1.0x10-6 2.0x10-6 3.0x10-6-0.1
0.0
0.1
0.2
0.3
0.4
0.5
sign
al a
mpl
itude
on
50 O
hm [V
]
time [s]
0V -20V
-1.0x10-6 0.0 1.0x10-6 2.0x10-6 3.0x10-6
-1
0
1
2
3
4
5
sign
al a
mpl
itude
on
50 O
hm [V
]
time [s]
-20V 0V
1 µs e-pulse