Neutron detector for SPIRAL2

FP7-SPIRAL2: Neutron Wall

Construction of new infrastructures – prepartory phase

FP7-INFRASTRUCTURES-2007-1

SPIRAL2 PREPARATORY PHASE

Work Plan

•In two years we have to write a proposal with technical details for the future ‘neutron wall’

•Economical aspects and current status: A. Maj

FP7-SPIRAL2: Neutron Wall

Physics Motivations

• In-beam gamma spectroscopy– Proton-rich: Far away from valley of stability. Study of isospin

symmetry for medium mass nuclei.• High-angular covarage: High efficiency• Neutron gamma discrimination• High multiplicity

– Neutron-rich: Neutron emmission veto to get the most exotic nuclei

• High-angular coverage: High efficiency • Neutron gamma discrimination

– Gamma delayed n-emission, unbound states• High-angular covarage: High efficiency• Measuring Eneutron?• Neutron gamma discrimination

– Other reactions ...

Physics Motivation

• Off-beam gamma spectroscopy – Delayed neutron emission in beta decay

• What do we need?– High efficiency– Good energy resolution and low threshold

Are all these requirements compatible?

Presentation: F. Delaunay

Some Requirements

• High Efficiency (nuclear break-up, fusion-evaporation neutrons)• Good energy resolution• Low energy threshold• Neutron gamma discrimination• High multiplicity (Diminished cross-talk)• Digital Compact electronics• Variable thickness?• New materials• ....

Efficiency

• Solid angle (different configurations for the different phases of AGATA and EXOGAM2) → Modular detector.

• Intrinsic efficiency: Material

2008 (2009) (2015)

15 capsules ~3% 45 capsules ~9% 135 capsules ~30%

31

Efficiency: The phases of AGATA

Presentation: A. Gadea

Discrimination gamma-neutron

• TOF• Pulse shape analysis

Discrimination using TOF and zero-cross-over (ZCO) in BC501A scintillator in the

neutron wall

http://nsg.tsl.uu.se/nwall/results/nwall-zco-tof.pdf

Analogical electronics

Digital Electronics

• Dinamic range• Sampling time • Band Width• Digital Pulse shape discrimination• ....

Presentation: P.A. Soderstrom

Neutron multiplicity

• Optimization of geometry to distinguish between 1n, 2n, ..., i-n• Dimished cross-talk (multiple hit)

J. Ljungvall, M. Palacz and J. Nyberg, NIM A 528 (2004) 741–762

Multiple scattering: Neutron Wall

Started a Geant4 simulation: Two barrels of BC501A (carbon-

hydrogen based liquid scintillator)

An initial idea is to increase distance between the neighbouring detectors BUT without decreasing

the solid angle.

Simple Simulations.

Simulations

500 mm

TOF between neighbouring detectors

Neutron source

•Monocromatic source 2 MeV

•Gamma multiplicity = 0

•Neutron multiplicity = 1 or 2

Dimensions D=100mm L=150

Simulations

2n

n

Two neutrons

One scattered neutron

t2

t1

t2=t1+Δt

t1

Simulations

Preliminary results from the simulations:

Both peaks are slightly shifted just a few channels. It is not possible to distinguish between them.

Two neutrons

One scattered neutron

Tdiff

Still everything very preliminary, among other things there is a kinematical dependence

New Materials

• High intrinsic efficiency• Good time and Energy resolution• Puse shape discrimination• Safer chemical properties (toxicity and flammability)• ...

Presentation: L. Stuttge

• What physics we want to do? – Define the detector characteristics

• Simulations:– Geometry of the neutron detector for SPIRAL2 for the different

phases of AGATA and EXOGAM2 (modular detectors?)• Digital electronics• New materials.• FP7 SPIRAL2 Preparatory Phase: Report ready in two years

Summary

How to proceed?

• Define working groups– Detector characteristics (Physics)– Geometry (Simulations)– Study New Materials– Digital Electronics– Other tasks?

Programme

• Neutron detector for SPIRAL2 (J. Valiente)• Coupling of the neutron detector with AGATA (A. Gadea)• New neutron detector material “Neutromania” (L. Stuttge)• Neutron detector developments at LPC Caen (F. Delaunay)• Digital pulse shape discrimination (P.A. Soderstrom)• New neutron detector array at TRIUMF (S. Williams)• PARIS project and its synergy with neutron detectors (A. Maj)• DISCUSSION

• At some point coffe and lunch

Chairman: B. Wadsworth