Neutron detector developments at LPC Caen
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Transcript of Neutron detector developments at LPC Caen
Neutron detector developments at LPC Caen
• -delayed neutron detectors
current limitations future issues
• Search for new solid scintillators (Neutromania)
• Simulations for future neutron arrays
• Developments of digital electronics
TONNERRETONNERREEXOGAMEXOGAM
TONNERRE array
32 bars, 160 x 20 x 4 cm3
BC400 plasticUp to 45% of 4Intrinsic n ~ 45% at 1 MeVEn from TOF (d=1.2 m)En/En ~ 10%Threshold : En ~ 300 keV
-delayed n detectors : current state of the art
A. Buta et al., NIM A455 (2000) 412
n detectors : current limitations
50 100 150 200 250 300time-of-flight (ns)
number of counts
46Cl29
S. Grévy and the TONNERRE collaborationS. Grévy and the TONNERRE collaboration
No n- discrimination : background
En/En limited by thickness & dflight
Tails :• slow scintillation component?• light transmission?
2n with current detectorsTest on 11Li()9Be+2n with TONNERRE (F.M. Marqués et al.)
n + + 2n
• background dominant
• n- discrimination needed
• n- discrimination : background reduction, multiple neutrons (eg 2n) liquid scintillators or new solid scintillators
• improve En resolution increase distance of flight, thin detectors
• cross-talk rejection : multiple neutrons (eg 2n) modular, high granularity
• lower threshold : thin, small volume detectors, digital electronics, good discrimination
Issues for future-delayed neutron detectors
From -n Meeting, LPC, Feb. 2007 & Neutron Detector Workshop, Madrid, July 2006
Possible test experiment in 2008 :
• feasibility of 2n with n- discrimination
• learn about issues
EDEN (NE213, 5 cm thick) and standard electronics
• test of digital electronics (LPC or other)
xn detectors : plans
Neutromania at Caen
Sample synthesis at LCMT-ENSICAEN (chemistry lab) :• PMMA- or polystyrene-based polymers• various fluors tested• secondary solvents and/or solutes (naphthalene, POPOP…)
Scintillation and discrimination properties tested at LPC with sources
Results :• no major difficulties to obtain scintillation
some samples show high light output (~BC400)• discrimination is challenging
no sample shows discrimination
Understand discrimination mechanisms :• test of current solid & liquid scintillators
T. Dalet et al., in preparation
Discriminating plastic
Qslow
Qtotal
Test at LPC with digital ADC : 2 GHz, 12 bits, 2500 samples (1.25 s), low rate
« plastic 77 », Brooks et al, IRE Trans. Nucl. Sci., NS-7, 35 (1960)
• No exotic compounds (similarities with NE213)• Light output ~ BC400• Clean synthesis process (CEA Saclay)
neutrons
neutrons
Geant4 simulations
Design future neutron detectors for• fast neutrons from breakup reactions (Eurisol)• -delayed neutron spectroscopy (Spiral2, Eurisol) 2 year postdoc (Eurisol DS, task 10), Brian Roeder
Why Geant4 ?• handles complex geometries• tracking built-in• lots of available physics models for particle interactions
But need to validate
Geant4 issues
B. Roeder
} built-in elastic & inelastic models} inelastic cross-sections from Menate
No satisfying models
Geant4 simulations with home-made model
Develop our own models Start with low energy elastic scattering on H & C Data-based model
Good at low energyAdd inelastic scattering…
B. Roeder
Geant4 simulations with home-made model
Home made
Looks goodAdd inelastic scattering…
B. Roeder
Digital electronics developments
Planned developments :• Digital CFD• Digital trigger• Neutron-detector dedicated electronics
ADC FPGA
TOFQslowQfast
CFD, gates...
Issues for n-detector electronics :• What ADC sampling rate do we need for timing ~500 ps?• What resolution for Qslow/Qfast?• Improve n- discrimination?
PhD starting Nov. 2007D. Etasse et al
Detector
Current developments :• Fast DAQ, « FASTER »• Digital Spectroscopy Amplifier
Conclusions & Outlook
New materials :• solids can discriminate n & • why? how?
Design of future n-detectors :• simulations being tested & improved• special emphasis on cross-talk performances (multiple neutrons) first designs in 2008/2009
Digital electronics :• developments in the next 3 years (PhD)• test experiment ~ 2008• improve n- discrimination?
Feasibility of 2n :• test experiment with thin detectors & discrimination (~2008) issues, improvements
The DEMON array
Neutrons from break up reactions @ tens of AMeV
96 modules, 16 x 20 cm2 (4 liters)NE213 liquid scintillatorn- discriminationEn from TOF (d~3 m)Modular : position, solid angle, cross-talk rejectionEn threshold ~ 2 MeVIntrinsic n > 30 % for 3 < En < 60 MeVAngular acceptance ~ 30%
DEMON & digital electronics
Qslow vs Qfast
137Cs sourceQslow vs Qfast
AmBe source
Test at LPC with digital ADC : 2 GHz, 12 bits, 2500 samples (1.25 s), low rate
DEMON efficiency with Menate
DEMON intrinsic efficiency
All processesH(n,n)
C(n,np)C(n,p)
C(n,n’3)
C(n,)
MENATE simulation
Neutron energy (MeV)
Eff
icie
ncy
500 keVee threshold
SimpleReasonably accurateOnly cylindrical detectors with NE213 scintillator
P. Désesquelles et al, NIM A 307, 366 (1991)
Reactions :• H(n,n)• 12C(n,n)• 12C(n,n’)• 12C(n,2n)• 12C(n,)• 12C(n,n’3)• 12C(n,p)• 12C(n,np)
n- discrimination with digital electronics
With digitized n & signals (eg from DEMON) :
• discrimination with Qslow/Qfast comparison : optimal gates event by event baseline correction no signal splitting discrimination threshold? En threshold? better separation?
• develop & test new discrimination algorithms