TThehe DIAMANTDIAMANT lightlight --chargedcharged particleparticle detectordetector :: PerformancePerformance andand plansplans forfor improvementsimprovements Barna M. Nyakó B.M. Nyakó (ATOMKI) Workshop on NWall at GANIL … 4-5 Oct. 2007. HIL, Warsaw TheThe DIAMANTDIAMANT collaborationcollaboration CENBG (Bordeaux) – ATOMKI (Debrecen) – University of Napoli J.N. Scheurer et al. B.M. Nyakó et al. G. la Rana et al. Recently extended by: iThemba LABS (Cape Town) S.M. Mullins et al. DIAMANT is a high-granularity, 4π light charged-particle detector array [1] of CsI(Tl) scintillators, used as ancillary device in large gamma-ray spectrometers to discriminate xn γ & particle-xn γ data by vetoing or gating on emitted light charged particles. Signal processing: realized in VXI standard [2]. Contact persons: B.M. Nyakó a, J.N. Scheurer b a) Institute of Nuclear Research, (ATOMKI), Debrecen, Hungary; [email protected] b) CENBG, CRNS-IN2P3-Université de Bordeaux I, Gradignan, France; [email protected] References 1. J.N. Scheurer et al. Nucl. Instr. and Meth. A 385 (1997) 501. 2. J.Gál et al. Nucl. Instr. and Meth. A 516 (2004) 502. Th e features of the DIAMANT array: Detectors: 84 pcs 3mm CsI(Tl) scintillators with photodiode readout ; 76 pcs square-shaped (14.5 mm) 8 pcs triangle-shape (29 mm) special wrapping technique: >80% light-collection efficiency; α-energy resolution: 2% (5.5 MeV) DIAMANT on service stand: the flexi-board arrangement Geometry Rhombicuboctahedron: flexible PCB forward wall(s): 3x3 or 5x5 detectors Efficiency geometrical: ~ 90% of 4 π detection of protons: > 70% detection of alphas: ≈ 50% High granularity deduce particle multiplicity; Doppler-correction of gammas Electronics: in-vacuum preamplifiers; VXI signal processing The Octal Particle Discriminator VXI Card Output data from the VXI card Gating on individual (1D) or combined Example spectra of a CsI (2D) spectra of these data enables the detector - rejection of random events - selection of reaction channels PID-vs-E - enhancement of gammas with Energy (E) special conditions Protons Putting 1D gates on the – Time: eliminates part of the random Alphas coincidences – PID: improves channel selection Putting 2D gates on PID Time – PID-vs-Time: Further cleaning of particle-gamma coincidences from randoms; channel selection – PID-vs-E: Improved selection of gammas in coincidence with protons or alphas Summary of EXOGAM experiments using DIAMANT at GANIL Exp-# Spokesperson(s) Date Beam/Target Detectors Status (MEV/mgcm -2) E404S P.J.Nolan Jun. 2002 76 Kr/ 58 Ni EXG + DIAMANT Resubmit +N.Redon (320/1.1) E404aS “ Oct. 2004 (328/1.1) EXG + DIAMANT Conf.,Thesis +VAMOS ------------------------------------------------------------------------------------------------------------------------------------------------ Commission B.M.Nyakó Oct. 2005 EXG+ DIAMANT +J.N.Scheurer + n-Wall E498S S. Williams Oct. 2005 18 Ne/ 24 Mg EXG + DIAMANT Not analysed (60/1) + n-Wall E482 A.Gadea Nov. 2005 36 Ar/ 24 Mg+Zr EXG + DIAMANT Oxigen (?) +S.Lenzi, (85/0.5+8) + n-Wall Resubmitted E451 B. Cederwall Nov. 2005 36 Ar/ 58 Ni EXG + DIAMANT Report by (111/6) + n-Wall K.Andgren ------------------------------------------------------------------------------------------------------------------------------------------------ E505 G.de Angelis May 2006 36 Ar/ 40 Ca EXG + DIAMANT (No info) + n-Wall E514 M. Palacz Jun. 2006 58 Ni/ 54 Fe EXG + DIAMANT In progress +J.Nyberg (240/8) + n-Wall trigger probl's DIAMANT early implementations: exp.s E404S, E404aS Physics motivation: Identification of γγγ-rays in nuclei around the drip -line nucleus 130 Sm: probing the maximally deformed light rare -earth region • The 2+ energy of 130 Sm , inferred to be 121 keV from fine structure in the ground-state proton decay of 131 Eu , predicts a large moment of inertia and hence large quadrupole (prolate) deformation for this exotic nucleus • The nucleus 130 Sm is thus an ideal candidate to assess the feasibility of gamma-ray spectroscopy of exotic nuclei produced with radioactive ion beams of SPIRAL using state-of-the-art detector systems • A pioneering experiment for EXOGAM using the DIAMANT ancillary detector; Difficulty: low γ-ray energy to be identified - Need for special detector arrangment. Experimental details – Target: 1.1 mg/cm 2 of 58 Ni; 76 5 – Beam: Radioactive Kr ions ( t1/2 = 14.8 h ) of intensity ~5-8 x 10 particles per second and energy ~4.5 MeV/u • First Expt : ‘EXOGAM’ (6 segmented Clover detectors + 2 small Clover detectors) + DIAMANT (56 CsI detectors: 90 °–ring + FW) • Second Expt : ‘EXOGAM’ (11 segmented Clovers) + DIAMANT (48 CsI detectors) + VAMOS From Nadine Redon DIAMANT early implementations in EXOGAM Early Implementation-1: [5x5 forward wall + 90°-ring of 32 CsI]; beam EXOGAM+DIAMANT setup with VAMOS: Early Implementation-2: Clovers @ 90°and backward angles Sketch of the 'forward-only' version (to minimize γ-absorption) DIAMANT spectrum Condition : at least 3p Condition : at least 1 α Nadine Redon : GANIL Oct . 2005 no condition Physics motivations of the NWall + DIAMANT campaigns: E498S High Spin States in the Tz=-3/2 Nucleus 37 Ca – Mirror Symmetry at the (S.W) Largest Values of Isospin; 18 Ne(60MeV) 1 mg/cm2 24 Mg target; DIAMANT: selective device E482 Mirror Energy Differences in the A=58 T=1 mass triplet and Charge (A.G) Symmetry Breaking terms in the nuclear effective interaction above 56 Ni; 36 Ar(85MeV) 0.5 mg/cm2 24 Mg target on 90Zr backing, 4pnA Problem: Oxigen build-up in target; DIAMANT: rejective device E505 Electromagnetic decay properties of the Tz=±1/2 A=67 and 71 mirror pairs: (GdA) A test for isospin mixing and for pn pairing; DIAMANT: selective device E514 Neutron Single Particle Energies with Respect to 100 Sn and Z=50 Core (M.P) Excitations by Investigating Excited States in 103 Sn; 58 Ni(240 MeV) 8 mg/cm2 54 Fe target, 1.7 pnA Problem: backing, trigger conditions; DIAMANT: selective device E451 Search for T=0 pairing and a new coupling scheme in 92 Pd and 88 Ru (B.C) 36 Ar(111 MeV) 6 mg/cm2 58 Ni target, 5 pnA Problem: Efficiency; (To be reported next.) DIAMANT: selective device DIAMANT „fuller ” configuration for EXOGAM + NWall experiments with stable and radioactive beams (Oct.-Dec. 2005, May-June 2006) Radioactive beams: two quad detector modules had to be removed to allow the NBI target loader pass through; This “ fuller ” configuration (Geom. Eff.: ~82 %) used for Stable beams beam Target Loader DIAMANT mechanics in preparation for the NWall + DIAMANT campaign. Example spectra for DIAMANT performance E482: ~ OK (~all worked) E514: Problems with backward part High beam intesity, targets sim. PID-vs-E for the same detector Absorbent problem Ta Al Comments on setup the VXI: check 2D spectra for correct operation! Indicate improper Discrimination mode Mixed vs Ball. Def. PID-vs-Time Example spectra for DIAMANT performance (E482,E514) Good charged particle selection Good channel selection, but reduced efficiency for DIAMANT (Marcin’s exp.) p 2p 2α α 1α1p Energy 1α 1n Good Time resolution (with loss in statist.) Experimental observations during NWall campaigns Performance of the CsI detectors: thanks to Gábor Kalinka (labor) , Giovanni La Rana (finance) Excellent: with proper absorber (even with high-intensity beams) Bad if absorbers are not sufficient for killing scattered ions/electrons DIAMANT must be protected from direct beam --> beam profile monitoring Performace of the electronics: thanks to János Gál & József Molnár Preamps: Excellent in spite of 'severe' conditions VXI: very reliable with controlled temperature One card is unstable - need testing Overall Performance: good Need for standard procedures to improve reliability, ease of data analysis Plans for improvements Aim : Enhance the performance of DIAMANT by optimizing it s features for furture Ge -detector arrays intended for nuclear structure studies with high intensity stable and radioactive beams of SPIRAL -2 Known P roblems: A. Troublesome installation of CsI detectors in DIAMANT chamber B. CsI calibration, Target loading vs. efficiency, Vacuum feed-through C. Maintenance of the DIAMANT VXI cards is not obvious D. Limitations due to γ-absorption for Eγ < 200 keV; CsI(Tl), PAs, cables Future Improvements: E. Test the applicability of Avalange PD-s for CsI-s in DIAMANT F. The CsI electronics has to be compatible with next-generation DAQ systems G. Position sensitive detector setups? Solving Problems – ad A. Troublesome installation of CsI detectors: Compact geometry – to fit DIAMANT chamber inside EXOGAM configurations A and/or B The (relatively) EASY bits: The flexi board equipped with CsI + Ta-abs.; Rigid but versatile geometry and the DIFFICULT bits: The flexi board on support stand, ready for installation Very tight arrangement Solving Problems - ad B: CsI calibration: Doppler correction, reaction mech. studies, etc. In-beam, with α-sources Measured In -beam in ATOMKI Problems: In -beam - needs beam -time, cost Sources: needs 232 U or 228 Th α-sources on target loader γ-sources i n target position (needs action from GANIL) Solving Problems - ad B ctnd: Particle-Energy calibration of CsI with γγγ-ray source 100 90 80 70 60 L (proton) 50 L (alpha) 40 30 Particle Energy [MeV] Energy Particle 20 10 0 0 10 20 30 40 50 60 70 80 90 100 Light-Yield L Based on comparative α and γ calibrations: [D. Horn et al. NIM A420(1992)273] Light yield vs E: Solving Problems - ad B (ctnd): Vacuum feed-through for glued ribbon cables Target loading vs. efficiency. PCB feed-throughs for Target loader for DIAMANT on the