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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
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