1. NEDA (NEutron Detector Array)
J.J. Valiente Dobon (LNL-INFN)
on behalf of the NEDA collaboration

2. 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)
-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)
FP7-INFRASTRUCTURES
SPIRAL2 PREPARATORY PHASE

3. 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

4. Physics with NEDA AGATA: A. Gadea EXOGAM2: G. de France GALILEO: C. Ur
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
GALILEO: C. Ur
PARIS: D. Jenkins

5. First day experiment Nuclear structure N=Z beyond 92Pd : 96Cd, etc
AGATA/EXOGAM2 + NEDA
Nuclear structure N=Z beyond 92Pd : 96Cd, etc

6. Second day experiment Low-lying collective modes in proton rich nuclei
PARIS + NEDA
Low-lying collective modes in proton rich nuclei
N=20
Transition densities

7. NEDA+PARIS experiment
Courtesy M. Lewitowicz
The reaction to study the Pigmy resonance in 44Cr
34Ar + 16O → 44Cr + 2n (34Ar 108 pps)

8. 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

9. 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.

10. Neutron Wall

11. Neutron Wall

12. Neutron Wall: N=Z-2 28Si(28Si,2nα)50Fe 24Mg(32S,2n)54Ni
S. Lenzi et al., PRL87, (2001)
A. Gadea et al., PRL97, (2006)

13. 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., NIMA (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.

14. 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

15. BC501 vs. BC537 response Presented by P. Garrett BC501 BC537
DESCANT
En = 2.5 MeV
En = 4.3 MeV
BC501A
BC537
Courtesy of P. Garrett, University of Guelph.

16. Solid scintillators for neutron detection

17. Simulations 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

18. 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)

19. Geometry study Presented by G. Jaworski
Definition of the unitary cell dimensions

20. Geometries
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

21. Performance of diff. geometries
Flat
Zig-zag
Spherical
BC501A
BC537
Presented by T. Hüyük

22. Discriminating neutron/gamma
Pulse shapes from the detector differs between neutrons and gamma rays.
neutrons
Usually both pulse shape analysis and the time-of-flight information is used for discrimination neutron- gamma discrimination.

23. Digital electronics: PSA
It is possible to obtain better quality using same algorithms but digital electronics
Analog zero-crossover method

24. Digital electronics: Neural Network
Applying an artificial neural network can increase the quality even further
P=sqrt(εn2+εγ2)

25. NEDA coupled to AGATA/EXOGAM2
Digitizer
prompt trigger
Digitizer
REQ
VAL
REQ
VAL
Pre-processing
GTS
local
GTS
local
Pre-processing
NEDA
GAMMA-ARRAY
PSA
PSA
Event Builder
GTS
supervisor
Event Builder
Global Merger
Tracking
Online analysis

26. Basic diference EXOGAM2/NEDA is the ADC: 200-300 MHz 12-14bit
Digital electronics: EXOGAM2-NEDA
MGT
Clocks
Fast serial links
Parallel links
Slow control
Serial link
Presented by M. Tripon
Basic diference EXOGAM2/NEDA is the ADC: MHz 12-14bit

27. Silicon Photo multipliers readout
SPMPlus
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

28. Currently bought commercial detectors from Saint Gobain
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.

29. Summary
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

30. Workshop program

31. 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

32. 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€

33. 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

34. 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
FUTURE WORK
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

35. NEDA possible geometries
Step-spherical
Spherical

36. Neutron-γ discrimination
BC537 n-γ discrimination
BC501A(D) n-γ discrimination

37. Light output

38. Time scale
2008
2009
2010 Q4 Q1 Q2 Q3
Validation GEANT4 neutron simulations
Geometry definition
Digital algorithms for PSA
Detector prototype
Test prototype
Electronics
Negoziations MoU
MoU signature

39. Silicon PM

40. Synergies
PARIS
EXOGAM array

41. 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

42. Intrinsic efficiency of BC501A and BC537