High resolution detector
developement based on solid
boron layer
DENIM
J. Orban
7-9th September , 2015
Contents
• Detectors at BNC
• Detectors based on solid boron converter
• Motivation
• Simulation
• Prototype detector / Experimental results
• Conclusion / Future
Contents
• Detectors at BNC
• Detectors based on solid boron converter
• Motivation
• Simulation
• Prototype detector / Experimental results
• Conclusion / Future
Detectors at BNC
• Detectors based on 3He
• Delay-line readout
Detectors at BNC
Instrument name Type
Active area
Resolution
TAST
PSD
TOF
ATHOS
REF
GINA
SANS
FSANS
200 mm X 200 mm
610 mm X O25 mm 1D tubes
1 mx1 m
200 mm X 200 mm
200 mm X 200 mm
200 mm X 200 mm
640 mm X 640 mm
200 mm X 200 mm
2 mm
TAS
Thermal diffractometer
TOF backscattering
Cold TAS
Reflectometer
Reflectometer
SANS
TOF-SANS
5 mm
2 mm
2 mm
2 mm
10 mm
2 mm
Contents
• Detectors at BNC
• Detectors based on solid boron converter
• Motivation
• Simulation
• Prototype detector / Experimental results
• Conclusion / Future
Motivation of own developement
• Small size chambers for FSANS and REFL
• Optimization of position resolution
• Focusing technics
• Miniaturazing
• Optimization for count rate
Contents
• Detectors at BNC
• Detectors based on solid boron converter
• Motivation
• Simulation
• Prototype detector / Experimental results
• Conclusion / Future
Simulation
7Li(1015 keV) +
10B
α(1777keV)
6%
α(1470keV) + γ(480keV)
94%
+n
7Li(840 keV) +
Ionization
model
TRIM
Simulation of
the ionization
process
Simulation of
the detection
process
Simulation
Neutron path
Ionization
Parameters:
• Neutron penetration depth
• α angle
• β angle
• α or 7Li
Simulation
Ionization by α
1470 keV
Ionization by 7Li
840 keV
70
1400000
60
1200000
50
1000000
40
800000
30
600000
20
400000
10
200000
0
0
Penetration depth [um]
Ionization by α
1470 keV
Energy loss
Total energy loss
Remaining energy
80
Lithium ionization energy loss vs. boron
thickness
1600000
70
1400000
60
1200000
50
1000000
40
800000
30
600000
20
400000
10
200000
0
Energy [eV]
1600000
Energy loss [eV/A/ion]
80
Alpha ionization energy loss vs. boron
thickness
Energy [eV]
Energy loss [eV/A/ion]
Simulation
0
Penetration depth [um]
Ionization by 7Li
840 keV
Energy loss
Total energy loss
Remaining energy
Simulation
Ionization length in CF4 vs. remained energy (Li)
3.5
3
2.5
2
1 bar
1.5
1,5 bar
2bar
1
0.5
Ionization length [mm]
Ionization length [mm]
Ionization length in CF4 vs. remained energy (α)
3.5
3
2.5
2
1 bar
1.5
1,5 bar
2bar
1
0.5
0
0
0
500
1000
1500
Remained energy [keV]
Ionization length in
CF4 by α
2000
0
500
1000
Remained energy [keV]
Ionization length
in CF4 by 7Li
1500
Simulation
Contents
• Detectors at BNC
• Detectors based on solid boron converter
• Motivation
• Simulation
• Prototype detector / Experimental results
• Conclusion / Future
B4C layer sputtering at Mirrotron LTD
• B4C layer with different thicknesses
• Characterization of the layers made by
Wigner
• DC Magnetron sputtering
• Polished aluminium substrate
• Collaboration with Mirrotron LTD in
prototype fabricationsupport
Prototype detector
• Thickness of boron layer: 1.5um
• Wire pitch: 0.8 mm
• Active area: 80 mm X 50 mm
• Readout: delay-line
• Filling gas: 2 bars CF4
• Anode - cathode distance: 3.2 mm
• Cathode - Boron layer distance: 2 mm
• 10 um / 30 um wire diameters
• Back cathode: PCB with conductive
lines
Experimental results:resolution
Position resolution at 4200V
Position resolution at 4300V
25000
1400
1200
Intensity [counts]
Intensity [counts]
20000
15000
10000
5000
0
1
6
11
16
1000
800
600
400
200
0
21
1
6
Position [pixels]
Position resolution at 4400V
16
21
Position resolution at 4500V
1000
900
800
700
600
500
400
300
200
100
0
4000
3500
Intensity [counts]
Intensity [counts]
11
Position [pixels]
1
6
11
Position [pixels]
16
21
3000
2500
2000
1500
1000
500
0
1
6
11
Position [pixels]
16
21
Experimental results:resolution
Position resolution vs. anode high voltage
• Position resolution is saturated
at 0.7 mm (FWHM)
Position resolution [mm]
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
4000
4100
4200
4300
4400
Anode high voltage [V]
4500
4600
Experimental results: linearity
Slit scanning
14000
• Detector is moved behind the
slit by 0,25 mm steps
12000
10000
8000
6000
4000
2000
0
1
6
11
16
Experimental results:linearity
Position linearity
2.5
• Detector is moved behind the
slit by 0,25 mm steps
Measured position [mm]
2
1.5
1
0.5
0
0
0.5
1
1.5
Real position [mm]
2
2.5
Experimental results: homogeneity
Experimental results: dead time
• Anode signal width: 100 ns
• Cathode signal width: 50 ns
• Length of delay line: 200 ns
• Conservative estimation: 250 ns dead time
• Global count rate capability › 4*105 events/s at 10% loss
• Global and local count rate capability is not measurable due to
low efficiency
• Beam flux was too low for local count rate measurement
Contents
• Detectors at BNC
• Detectors based on solid boron converter
• Motivation
• Simulation
• Prototype detector / Experimental results
• Conclusion / Future
Conclusions
• Boron detector is a good candidate for our plans
• Delay-ine readout is a good compromise for low-cost read-out
• 0.7 mm position resolution is achieved with solid boron layer
• 0.8 mm wire pitch is a limitation
• Count rate capability and position resolution is sufficient for our
applications
• Position linearity is good
Future
• Investigation of the possibility of smaller wire pitch
• Multigrid construction for high efficiency
• TPC algorithm with delay-line readout to decrease the
dispersion of position resolution
• Further measurements (characterization of local count
rate capability, efficiency, gamma sensitivity…)
Thank you for your attention!