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S. Normand,1 V. Kondrasovs,1 G. Corre,1
J.-M. Bourbotte,1 A. Ferragut2
1 Laboratoire Capteurs et Architectures Electroniques2 Saphymo
28-29 september 2011, Helsinki, Finland Speaker: K. Boudergui ([email protected] )
Neutron-gamma Discrimination in Standard Plastic Scintillators : application for passive
neutron measurements
2
Overview
Neutron-gamma discrimination goals
Is using a hardware a solution ?
How to manage discrimination by signal processing ?
Experimental results
K. BOUDERGUI etal., [email protected] - 28th september 2011
3
• Plastic scintillators properties A low cost detector Neutron-gamma
discrimination is complex (especially in solid detectors)
• Working on signal processing improvements rather than on intrinsic material properties
Liquid Organic
scintillator
Boron loaded plastic
scintillator
plasticscintillator
simple Hard
low
high
COST
He3
DISCRIMINATION ABILITIES
Neutron gamma discrimination goals
K. BOUDERGUI etal., [email protected] - 28th september 2011
4
Plastic Scintillators constraints Fine pulse shaping with a high data rate analog
to digital conversion (800 MHz, 8bit ADCs). Signal width about 20 ns with a rise time around 2 ns.
Hardware and Software partition for best data processing
Ad-hoc neutron-gamma discrimination algorithm
Neutron gamma discrimination goals
K. BOUDERGUI etal., [email protected] - 28th september 2011
5
Scintillator
PA
RT<=1nsG=10-50
ADC 200 MHz
8 bit
ADC 200 MHz
8 bit
ADC 200 MHz
8 bit
ADC 200 MHz
8 bit
Del
ay 0
.5- 1
ns
Del
ay 0
.5-1
ns
Delay 0.5- 1 ns
HT
µC
HV management
Setting and monitoring
Data and control transfers
-HT
FPGA
PC End User Interface
Data (4 Bytes, 200 MHz)
Is using a hardware a solution ?
K. BOUDERGUI etal., [email protected] - 28th september 2011
6
4 ADCs 200 MHz, 8
bits
100 MHz
PIC32 µc
SPARTAN IIIFPGA
demonstration-board
Delay line
Is using a hardware a solution ?
CEA digitizing board
K. BOUDERGUI etal., [email protected] - 28th september 2011
7
How to manage discrimination by signal processing ?
Neutron-gamma discrimination patented algorithm
Signal splitted into two parts:
• One is delayed, the other, emphasized• One without any change
Both signals are merged and then generate two quantities plotted in a bi-dimensional spectrum
Two regions appears, one for , one for and some crosstalk
K. BOUDERGUI etal., [email protected] - 28th september 2011
8
Neutron
Gamma
Let’s have a better look on the signal !
Gamma
After a pre-processing, two quantities are generated : sigma 1 and sigma 2 as described before
(Positive and negative fraction)
How to manage discrimination by signal processing ?
Neutron (Only positive fraction)
K. BOUDERGUI etal., [email protected] - 28th september 2011
9
SourceTotal count rate
Neutron count rate
Am-241 2500 c/s 130 c/s
Cs-137 16000 c/s 120 c/s
Cf-252 5600 c/s 320 c/s
Co-60 4000 c/s 128 c/s
Background
2200 c/s 120 c/s
Cf-252Neutron and gamma
Co-60 Gamma only
Experimental results
K. BOUDERGUI etal., [email protected] - 28th september 2011
11
No raising in the count rate is observed when we are set in a “neutron counting mode” and a gamma source is added (241Am, 137Cs, 60Co)
The efficiency on neutron sensitivity is around 25%
“estimated by the Monte Carlo MCNP simulation (252Cf),”
A false alarm rate less than 0.01%
The detection probability is 97.5% for a 12,000 n/s neutron source at 1 meter (AIEA+ANSI)
Experimental results
K. BOUDERGUI etal., [email protected] - 28th september 2011
12
Flexible and configurable hardware architecture allows to use it for a wide range of applications
Good performances obtained for homeland security applications with Plastic Scintillators
NR-module integration in an operating MA-NRBC system
Performance improvements will provide an He-3 alternative
Summary
K. BOUDERGUI etal., [email protected] - 28th september 2011
