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