Daniel Cano-Ott, β-neutron Caen, Feb 27 th Ciemat. Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas

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1 Summary of the DESPEC neutron working group activities D. Cano-Ott on behalf of the WG members CIEMAT, IFIC, LNL, FYL, UPC, UU, UW

2 FAIR: Facility for Antiproton and Ion Research GSI today UNILAC 100 m SIS 18 Future facility SIS 100/300 ESR Cost Approx 1000M Timescale 650M central German government 100M German regional funding 250M from international partners RESR HESR Super FRS Feb German funds in budget start construction NESR NUSTAR 2012 phased start experiments 2014 completion

3 FAIR: Production Rates Predicted Lifetimes > 100ns from FAIR CDR, section 2

4 NUSTAR: Nuclear Structure Astrophysics & Reactions Exotic (radioactive) beams formed by fragmentation, selected by separator. HiSpec :gamma spec DeSpec :decay spec LASPEC: laser spec MATS: Penning traps R 3 B: reactions Stored beam (rings): EXL : hadron scattering ELISe : electron scattering AIC : antiproton scattering

5 DESPEC DEcay SPECtroscopy studies at FAIR The DESPEC experiment exploits the development of high intensity radioactive beams at FAIR to study their decay properties. p We will be able to study nuclei of much shorter half life than those produced at an Isol facility. It is part of the FAIR approved experimental programme The collaboration is formed (but it is open), and gathers people from Isol as well as from fragmentation facilities, it adds also part of the Gamma spectroscopy community. The experimental set-up is in its design phase, a lot of MC simulations are being performed, in a year from now we should start the production phase. Experiments will take place in the year n γ Complete spectroscopy: Prompt gammas β-delayed gammas β-delayed neutrons

6 DESPEC Layout Share the space with the in-beam gamma ray setup and a magnetic spectrometer. DESPEC HISPEC

7 Activities of the DESPEC Neutron Working Group Monte Carlo simulations of the TOF spectrometer (GEANT4) and the 4π (MCNPX) detectors are in progress. The physics models inside GEANT4 need to be patched or changed. 1 st round of prototype units acquired already: liquid scintillator cells (St. Gobain and Scionix), plastic scintillators (Scionix), position sensitive BF 3 and 3 He counters. Systematic tests with digital electronics performed by various institutions (CIEMAT, KTH, U. Uppsala). First beam tests performed. Need of future test measurements in 2007 but not clear where! Workshop on neutron detectors for DESPEC and other facilities, hold at CIEMAT s headquarters in Madrid, July 14 th and 15 th. 28 participants from 13 institutions and 5 companies (St. Gobain, Scionix for detectors, digital electronics ). Scientists working from the FAIR & SPIRAL-2 communities. Define the guidelines for the future work. GEANT4 Monte Carlo course on neutron detectors for the DESPEC/SPIRAL-2 communities. Organised by CIEMAT and IFIC-Valencia. 9 th -11 th of April More men power is necessary! We covered several PhD positions recently but

8 I. TOF Neutron Spectrometer (NE213) First Monte Carlo simulations with GEANT4. First experimental tests with a commercial detector cell + digital electronics. 2R d L Neutron source L Neutron source Possible 2 nd layer of detectors for enhancing the efficiency

9 Requirements for the TOF spectrometer (conclusions of the Madrid meeting): n-γ discrimination mandatory for reducing backgrounds, enable β-2n,3n... detection Liquid scintillators (or new solid scintillators) NE213 + EJ309 (only for short detectors), EJ325 (?, inexpensive). Longer bars, higher threshold! Still check some plastics/crystals like Stylbene. The best n/γ discrimination comes from a discrete array. Test NE213 with various PMT, EJ309 and EJ325 (push the thresholds down). good ΔE n /E n thin, small volume detectors with increased d flight ~3,4 m (space for both n and γ setups) lowest possible threshold in E n thin, small volume detectors + digital electronics (30 kev E n ) cross-talk rejection enable β-2n, 3n detection modular, highly granular array (>100 detectors) + variable geometry (cm alignement precision is Ok). 2options: DEMON-like or TONERRE-like (curved or straight bars). Cross talk rejection by time and E dep

10 high ε n identification 1π ΔΩ n 2π and ε γ for combined neutron/gamma measurements identification of n-decay to excited states large volume high efficiency Ge det s (conflict with the need for high ΔΩ n ) digital electronics better control of systematic uncertainties Other issues: β-trigger, need of additional detectors at SPIRAL (plastics) size of the beam spot defined d most probably bl by the Ge needs have enough space for both neutron and Ge arrays minimise the influence of magnetic fields! minimise the amount of dead material in and around the implantation setup: no B, no Li, no Br, avoid plastics (or materials rich in hydrogen). Al is a tentatively good material (low cross sections).

11 Detailed geometries with GEANT4 Prototype unit BC501A (NE213 = BC501) + 1 from Scionix (= EJ301) 12.7cmx12.7cm (thick detectors)

12 II. 4π Detector At present, a clone of the (very nice) NERO detector at MSU. high efficiency (independent on the E n ) large volume, large number of detectors ( 3 He, BF 3 ) investigate the possible energy reconstruction position sensitive detectors, deconvolution of the Φ(x,y,z,t n ). Development of appropriate software algorithms. Polyethylene (60cm x 60cm x 80cm) NERO detector [1] Hendryk Schatz schatz@nscl.msu.edu Ring A 3 He prop. Counters Internal diam.:2.5 cm Length: 80 cm Pressure:4.1 bar Wall thickness:0.05 cm Ring B and C BF 3 prop. Counters (99% 10 B) Internal diam.: 5.08 cm Length: 80 cm Pressure: 0.7 bar Wall thickness:0.05 cm Hole (void) 22.4 cm diameter Boron Carbide layer 1 cm thickness

13 Detector testing

14 Pulse shape analysis for n/γ discrimination with digital electronics Pulse Shape Discrimination: BC501A Pulse shape slow fast ( e, p, α,...) PSD Photons 0.6 delayed total Neutrons time(ns)

15 PSA performance I DATA Fitted γ shape Fitted n shape

16 PSA performance II DATA Fitted γ shape Fitted n shape

17 FADC ch channels Fit to True shape method: n/γ n/γ discrimination + pileup reconstruction BC501A with D-T neutron source χγ2 Fit to True Shape: n/γ discrimination Neutrons Photons time(ns) χ2 14 neutron Excellent n/γ discrimination + pileup reconstruction (tests with a Deuterium /Tritium source). source) C. Guerrero et al., submitted to NIMA Daniel Cano-Ott, β-neutron Caen, Feb 27th 2007

18 3 x BF 3 counters 3 x position sensitive 3 He counters 1 m 3 of polyethylene l 3x BF 3x 3 3 counter He counter (various sizes) 5 cm x 50 cm

19 BC 400 plastic scintillators of various sizes.

20 Summary and conclusions (I) Various prototype detectors have been acquired: 2 x N213 cells(st. Gobain and Scionix) i with ihslow and fast PMTs, several BC400 plastic scintillators. ill Systematic characterisation at a digital test bench: 8 bit fadc at 1Gs/s. We have found variations in the pulse shapes as a function of the neutron and gamma energy. We will have very soon a portable 4 channel digital DAQ. The several pulse shape analysis methods are really powerful but 8 bits aren t enough for reducing the energy threshold down to 30 kev: 10 bits or even 12 bits will be necessary. Planning some measurements at irradiation facilities, but a real test measurement is necessary. Find common points with other facilities/groups. This meeting!

21 Monte Carlo Simulations

22 Table based Monte Carlo Simulation codes (MCNP, MCNPX and other well established codes) in neutron transport problems allow: 1) To use cross sections from any possible nuclear data library: ENDFB, JENDL, JEFF, CENDL, BROND. The data format is well known and well documented: ENDF. 2) The ENDF files are publicly available and can be downloaded from the web. 3) All isotopes for which data exist are in the libraries. 4) Several processing tools for those files do exist (free or under license): PREPRO, NJOY 5) Sorting of secondary particles, many times without the necessary correlations between them. GEANT 4 neutron data library G4NDL: 1) No. Cross sections are God -given and sometimes even wrong! In the past, compilation of different channels from different libraries thus violating the unitarily (sum of partial σ i different from the total σ). ) No information of the format, but probably just point-wise cross sections. 2) Files have to be requested and are sometimes not delivered. 3) Only a safe selection of isotopes is present. 4) No processing tool is available to the public. The user is forced to use the G4NDL file distributed. 5) Appropriate data missing or incorrect in many cases.

23 Proposals ordered by priority: 1) To develop an interface between the ENDF files and GEANT4 inside the NUSTAR Collaboration. Understand the G4 format (temperature dependentd point-wise i cross sections?). Program an interface between the ENDF and G4 formats. Probably existing tools like PREPRO could be used for time-saving. In our opinion, it could be done in 6 months by one person with enough computing skills. 2) Patch GEANT4 with low energy models for secondary particle production which do include particle correlations. This has been done already for (n,g) measurements by IFIC and CIEMAT. What about (n,f)?

24 A Decay Event Generator for DESPEC Objective: Develop a Monte Carlo event generator for designing, g optimization and performance characterization of DESPEC experimental set-ups implantation One example: TAS NE213 moderator + 3 He count Primary processes: β - -decay β + /EC decay Isomeric decay Also: βn -decay β-decay Isomeric decay D. Jordan & Jose L. IFIC-Valencia

25 Basis for generator: Statistical model for population and decay of the nucleus Known level scheme Electromagnetic cascades β-intensity β-strength LEVEL DENSITY GAMMA-RAY STRENGTH S β ( E ) x = f I ( E ) x ( Q E ) T β β x 1 2

26 Inputs (simplified): Parent nucleus/level variables (A,Z,T 1/2, J π ) Type of decay (β -, β + /EC, ID) Q-value, beta-intensity distribution, neutron separation energy (Q β, I β, S n ) ε + ε + Fermi functions: f0, f0 + f0, f0 f0 (internal) Known level scheme (E lev, J π,e γ, I γ, α) Unknown level scheme: level density and gamma-strength parameters (internal) Approximations/simplifications: β-spectral shape: allowed electrons (EC or CE) only from K-shell no γ/n / competition i (n emitted) Integrated within Geant4 An event consists on (a Simulation Toolkit beta and) a set of γ-ray framework (and CE) momenta

27 Summary and conclusions (II) We need to patch GEANT4 or get it patched from the developers (not very likely l but ). 6 months work The decay event generator is ready.

28 Is there anything we (SPIRAL+FAIR+ ) can do in common? Practical things -Development of MC simulation tools. -Detector tests. -DAQ + software tests (common developments?) -Validation of our tools. -Networking: create a network for facilitating the information exchange. Training of students, participation in test-beams, technical workshops. More ambitious things -Share the design of the neutron cells? -Combining the SPIRAL and FAIR detectors for very ambitious experiments? -Have one wandering detector?

29 Proposed active implantation detector ΔE 8 x 8 cm 128 x 128 strips 1 mm (Micron in progress) 3 dssdd 8 cm Vet o T. Davinson, U. Edinburgh

30 A modular high resolution γ-detection array (proposed) Desired specifications: Res.2% Eff ph 21.7 % Peak to total 0.43 Modular Granularity promt flash (and summing) Tracking (correlation with implantation) Ang corr and pol (will benefit from Agata developments) 24 x 8x24 cm 2 Features of the proposed stacked planar strip array. Detectors 24 Planar elements per detector unit 3 Strips per element Salamanca: B. Quintana Electronics channels 1152 Effective number of voxels Univ. Autónoma de Madrid: A.Jungclaus Ires Strasbouerg: G. Duchene Univ. Surrey: P.Walker, P.Regan, W.Gelletly, ZP Z.Podolyak Cologne: P. Reiter Daresbury Laboratory: J.Simpson, D.Warner, I.Lazarus, V.Pucknell and Daresbury engineers IFIC (CSIC) Valencia: B. Rubio, J.L. Taín, A.Algora Debrecen: A.Algora Univ. Jyväskylä : R. Julin, J. Aysto, A. Jokinen GSI: M. Gorska, J. Gerl Liverpool: P. Nolan, A. Boston, E. Paul Bucharest: G. Cata-Daniel

31 BC501A response to an Am/Be neutron source Am/Be neutron source spectrum cou ounts Area method Fit to True Shape Differ in 1.2% of all cases How to implement this method into the HISPEC / DESPEC DAQ? PC farm or FPGA + flash ADCs? Photons Neutrons Pulse Area