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NEDA (NEutron Detector Array). J.J. Valiente Dobon (LNL-INFN) on behalf of the NEDA collaboration. Organization. Spokeperson: J.J. Valiente Dobon (LNL-INFN) GANIL Liason: M. Tripon (GANIL) Steering committee: -B. Wadsworth (U. of York) -N. Erduram (U. of Istanbul)

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Neda neutron detector array

NEDA (NEutron Detector Array)

J.J. Valiente Dobon (LNL-INFN)

on behalf of the NEDA collaboration


Spokeperson: J.J. Valiente Dobon (LNL-INFN)

GANIL Liason: M. Tripon (GANIL)

Steering committee:

-B. Wadsworth (U. of York)

-N. Erduram (U. of Istanbul)

-L. Sttugge (IRES – Strasbodurg)

-J. Nyberg (U. of Uppsala)

-M. Palacz (U. of Warsaw)

-A. Gadea (IFIC - Valencia)

Members of the collaboration:

U. of Ankara (Turkey), COPIN (Poland), CSIC-IFIC (Spain), Daresbury Laboratory (U.K.), GANIL (France), U. of Istanbul (Turkey), INFN (Italy), IRES (France), U. of Nidge (Turkey), U. of Uppsala (Sweeden), U. of York (U.K.) and Kolkata, India (under discussion)



Working groups
Working groups

  • Detector characteristics (Physics interests of NEDA to define the detector specifications).

    • Responsible: B. Wadsworth

  • Geometry (Make a full study of geometry to determine (materials) efficiency, reduce cross-talk, ... Comparison between different codes: Geant4, MCNP-X. Simulate effect of other ancillaries, neutron scattering.).

    • Responsible: M. Palacz

  • Study New Materials (Exploring new materials, solid scintillators, deuterated liquid scintillators).

    • Responsible: L. Stuttgé

  • Digital Electronics (Flash ADCs, GTS, EXOGAM2 electronics, ..)

    • Responsible: A. Gadea

  • PSA (Pulse shapes analysis, PSA algorithms, ...).

    • Responsible: J. Nyberg

  • Synergies other detectors (Detectors that can be considered in synergy with NEDA: EXOGAM2, PARIS, AGATA, FAZIA, GASPARD, DIAMANT, DESCANT, Neutron spectroscopy at DESIR, DESPEC/HISPEC, NEUTROMANIA, ... ).

    • Responsible: P. Bednarczyk

Physics with neda
Physics with NEDA

NEDA will address the physics of neutron-rich as well as neutron deficient nuclei, mainly in conjunction with gamma-ray detectors arrays like AGATA, EXOGAM2, GALILEO and PARIS.

  • Nuclear Structure

    • Probe of the T=0 correlations in N=Z nuclei: The structure beyond 92Pd (Uppsala, LNL, GANIL, Stockholm, York)

    • Coulomb Energy Differences in isobaric multiplets: T=0 versus T=1 states (Warsaw, LNL, GANIL, York)

    • Coulomb Energy Differences and Nuclear Shapes (York, Padova, GANIL)

    • Low-lying collective modes in proton rich nuclei (Valencia, Istanbul, Milano, LNL, Krakow)

  • Nuclear Astrophysics

    • Element abundances in the Inhomogeneous Big Bang Model (Weizmann, Soreq, GANIL)

    • Isospin effects on the symmetry energy and stellar collapse (Naples, Debrecen, LNL, Florence)

  • Nuclear Reactions

    • Level densities of neutron-rich nuclei (Naples, LNL, Florence)

    • Fission dynamics of neutron-rich intermediate fissility systems (Naples, Debrecen, LNL, GANIL)

AGATA: A. Gadea

EXOGAM2: G. de France


PARIS: D. Jenkins

First day experiment
First day experiment


Nuclear structure N=Z beyond 92Pd : 96Cd, etc

Second day experiment
Second day experiment


Low-lying collective modes in proton rich nuclei


Transition densities

Neda paris experiment
NEDA+PARIS experiment

Courtesy M. Lewitowicz

The reaction to study the Pigmy resonance in 44Cr

34Ar + 16O → 44Cr + 2n(34Ar 108 pps)

Physics themes
Physics themes

  • G de Angelis – Physics with NEDA

  • G. de France - Results on the 92Pd experiment

  • A. Gottardo - Study of proton-rich nuclei with NEDA around A=100

  • A. Pipidis - NEDA: At the service of n-p correlations

  • M. Palacz - Spectroscopy next to 100Sn: 3n gating and where is 100In?

  • A. Di Nitto – The role of isospin in fusion-evaporation reactions

  • G. Verde - The Farcos project and access to the symmetry energy with proton-neutron measurements

Problem definition
Problem definition

  • -NEDA: Neutron detector to be used coupled to AGATA/EXOGAM2/GALILEO/PARIS

  • -Previous experience with the NWall (BC501) currently at GANIL

    • -High efficiency 25% for one neutron.

    • -Relatively good gamma/neutron discrimination.

    • -Problems with cross talk.

    • -Low efficiency for 2n (1-2%).

    • -Analogic electronics.

Neutron wall n z 2
Neutron Wall: N=Z-2



S. Lenzi et al., PRL87, 122501 (2001)

A. Gadea et al., PRL97, 152501 (2006)

Cross talk low 2n cross section
Cross talk – low 2n cross section

  • High cross talk between neighboring detectors

  • It is not possible to differenciate between 2n real events or just 1n scattered.

  • Therefore neighbouring detectors are dismiss in the analysis and the efficiency decreases to 1-2%.

J. Ljungvall et al., NIMA528 471 (2004)

Possible to improve 2n efficiency using TOF among detectors

One aim of NEDA is to be able to distinguish between real 2n events and scattered neutrons → Increase of the 2n efficiency.

Strategy of neda
Strategy of NEDA

  • -Optimization of the geometry: unitary cell size, spherical, planar, zig-zag, granularity, distance, versatile.

  • -FEE: GTS integrated in the motherboard and FADC in a mezzanine. Fully compatible with AGATA, GALILEO and EXOGAM2

  • -Use of the TOF information in addition to the measured energy to disentangle the 1n scattered events from the real 2n channels

  • -Use of the deuterated scintillator BC537

    • Pulse height seems to be proportional to incident neutron energy (reported by DESCANT collaboration)

    • Provides another method of determinig neutron energy beyond TOF

    • -Can lead to a better discrimination of high multiplicity neutron events and scattered events.

  • -New solid scintillators  Lawrence Livermore National Laboratory

Bc501 vs bc537 response
BC501 vs. BC537 response

Presented by P. Garrett




En = 2.5 MeV

En = 4.3 MeV



Courtesy of P. Garrett, University of Guelph.


Presented by M. Palacz

  • Neutron HP model in G4.9.2.p01 (rel. March 2009) much improved comparing to earlier versions

  • Total cross sections and angular distributions for elastic scattering on p, d, and 12C reasonable

  • Correct (high energy) γ-ray lines produced

  • Wrong kinematics (angular distributions?) in the 12C(n,α)9Be reaction.

  • Important reactions still missing, like 12C(n,n’)3α

Existing defficiencies not significant in the <~10MeV energy range, which if interest for NEDA

Light output of liquid scintillator
Light output of liquid scintillator

  • The light-output L is usually given in MeVee: the particle energy required to generate 1 MeVee of light is defined as 1 MeV for fast electrons

  • L is generally less for heavier particles such as protons, deuterons, alphas, beryllium, carbon…

  • Therefore, the light output L in a certain path dx is a function of the deposited energy E in dx: L(E)

Deposited energy

Light output

Presented by A. Gottardo

Dekempeneer et Liskien NIM A 256 (1987) 489-498

Geometry study
Geometry study

Presented by G. Jaworski

Definition of the unitary cell dimensions


  • There are two possible main geometries, either spherical or planar.

  • The spherical geometry presents the full symmetry.

  • The planar has some advantages, than the spherical does not present.

    • -Flexibility – different arrangements of the detectors, e.g. zig-zag

    • -Different focal posistions (500cm, 1000cm, 2000cm)

    • -Budget issues

Performance of diff geometries
Performance of diff. geometries






Presented by T. Hüyük

Discriminating neutron gamma
Discriminating neutron/gamma

  • Pulse shapes from the detector differs between neutrons and gamma rays.


  • Usually both pulse shape analysis and the time-of-flight information is used for discrimination neutron-gamma discrimination.

Digital electronics psa
Digital electronics: PSA

It is possible to obtain better quality using same algorithms but digital electronics

Analog zero-crossover method

Digital electronics neural network
Digital electronics: Neural Network

  • Applying an artificial neural network can increase the quality even further


Neda neutron detector array


prompt trigger



















Event Builder

Event Builder

Global Merger


Online analysis

Neda neutron detector array

Digital electronics: EXOGAM2-NEDA



Fast serial links

Parallel links

Slow control

Serial link

Presented by M. Tripon

Basic diference EXOGAM2/NEDA is the ADC: 200-300 MHz 12-14bit

Silicon photo multipliers readout
Silicon Photo multipliers readout


  • Direct replacement for photomultiplier tube

  • Insensitive to magnetic fields

  • Can operate in vacuum

  • Large sizes possible

  • Attractive for simultaneous PET and MRI scanning

Synergy with PARIS – D. Jenkins

Bc501a and bc537 detectors
BC501A and BC537 detectors

Currently bought commercial detectors from Saint Gobain

  • Two detectors 5”x5” BC537 (LNL-INFN)

  • Two detectors 5”x5” BC501A (York-Valencia)

A. Pipidis (founded SP2PP) working on the characterization of the detectors.


  • Currently bought BC537 and BC501A commercial detectors to test:

    • cross talk

    • light production

    • FADC – frecuency and number of bits

      – PSA – neutron-gamma discrimination

  • First contacts with Livermore – Start up collaboration solid scintillators?

  • Test of SPMPlus from York in BC537 and BC501A

  • Development of electronics in synergy with EXOGAM2

  • Optimal geometry

Phases of neda
Phases of NEDA

The current development on new materials and readout systems for neutron detection makes necessary to build NEDA in four different phases:

  • Phase 0: Upgrade of Neutron Wall with digital electronics.

  • Phase 1: R&D on new material and light readout systems for a highly segmented neutron detector array.

  • Phase 3: Construction of a limited size Demonstrator 

  • Phase 4: Final construction of NEDA

With current technological status
With current technological status …

  • Three main options:

    • 200 detectors BC501A – PM readout –Digital electronics

      • Total cost: 600K€ (BC501A) + 200K€(Elec.) + 40K€ (mechanics) = 840 K€

    • 200 detectors BC536 – PM readout – Digital electronics

      • Total cost: 2000K€ (BC537) + 200K€(Elec.) + 40K€ (mechanics) = 2240 K€

    • Upgrade Neutron Wall - Phase 0 (Digital electronics)

      • Total cost (50 channels) = 40K€

Collaborating institutes
Collaborating Institutes

  • Centro Superior de Investigaciones Cientificas (CSIC) – Valencia

  • Grand Accelerateur National d’Ions Lourds (GANIL)

  • Istituto Nazionale di Fisica Nucleare – Laboratori Nazionale di Legnaro

  • Royal Institute of Technology - KTH

  • University of Istanbul

  • University of Lund

  • University of Nidge

  • University of Uppsala

  • University of Warsaw

  • University of York

Summary and future work
Summary and future work

  • NEDA – Looks at improving efficiency for 2n channels – BC537, geometry

  • Validated simulatons – realistic results for BC501 and BC537

  • Included model for light production.

  • PSA algorithms to discriminate neutron-gamma – Neural Network great perspectives.

  • Synergies

    • PARIS (A. Maj): SPMPlus, electronics?

    • EXOGAM (G. De France): electronics

    • Neutron Spectroscopy at DESIR (D. Cano & N. Orr): Simulations, FADC


  • Currently bought BC537 and BC501 commercial detectors to test:

    • cross talk

    • light production

      – PSA – neutron-gamma discrimination

  • Test of SPMPlus from York in BC537 and BC501

  • Development of electronics in synergy with EXOGAM2

  • Design of FADC mezzanines

  • Optimal geometry

Neda possible geometries
NEDA possible geometries



Neutron discrimination
Neutron-γ discrimination

BC537 n-γ discrimination

BC501A(D) n-γ discrimination



EXOGAM array

Commercial electronics struck
Commercial electronics: Struck

4 channel VME digitizer/transient recorder with a sampling rate of up to 500 MS/s (for the individual channel) and 12-bit resolution

Programmable FPGAs

Intrinsic efficiency of bc501a and bc537
Intrinsic efficiency of BC501A and BC537