The DIAMANT Light-Charged Particle Detector

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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

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 γγγwith-ray source

100

60 L (proton) 50 L (alpha)

Particle Energy [MeV] Energy Particle 20

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 radioactve beams AFRODITE chamber (iThema LABS, SA)

Alternative t arget holder for stable beams: Enables the use of complete geometry Need for beam collimation New opening of the chamber - easy handling New inside connectors and feed-throughs (SA experience) Solving Problems - ad C: The VXI test-bench at GANIL

VXI cards for DIAMANT need low temp. (22C °)

Overheating happened in early exp.-s

Few VXI channels developed permanent faults, some recovered

One card has problems, needs fixing:

Maintenance of the DIAMANT VXI cards:

Ageing: > 10-year old technology; Obsolate parts/circuitries (GIR experts left the field, etc.); New VXI test-bench in GANIL - now compatible with CsI-VXI cards Need for dedicated slot(s) compatible Personnal's help very much appreciated ! with DIAMANT VXI cards (Solved!) Gamma-efficiency measured for Solving Problems – ad D: EUROBALL + DIAMANT installed γ -absorption: caused mainly by CsI(Tl) + PAs, cables

DIAMANT: Well suited for higher-energy γ-spectr.

In special configurations (cf. E404S) absorption can be minimized

Aims: minimize material, make room for handling, improve low-energy respons of the system

Solution: Use of APD instead of pin -PD on CsI-s Transition to Perspectives! Hamamatsu S8664 ser. short wavelength type Expected advantages of using avalange photodiodes : 2 APD: 10x10mm 1. Higher light collection efficiency, large gain, signal/noise, --> improved particle discr. low-energy detection 2. Simpler PA arragement may be sufficient --> easier handling

Plans for feasibility studies of using APD-s instead of pin -PD-s (EXOGAM-2 FP7 ?? G.d F. ) Future Improvements - ad E.

Properties of short wavelength type APD-s: Hamamatsu S8664-10-10

good spectral response for CsI light high quantum efficiency

low dark current at V bd (V opt ~ 350V) gain ~ 50 (T=20 C °)

Disadvantages: Needs higher Voltage PS (opt. ~350 V) Gain is temperature dependent --> stabilisation

APD with CsI(Tl): Excellent resolution for X-rays, low-energy γ-s Coincidence spectroscopy with [J.Kataoka et al. NIM A541(2005)398] PAD+CsI(Tl) can be done (?) --> use of DIAMANT as gamma-array for L.E. γ-s

Ge-CsI coinc. time resolutions with DIAMANT [J.Gál et al. NIM A516 (2004) 502] Future Improvements - ad F:

Plans for Upgrading: Digital Signal Processing for the CsI electronics for compatibility with next-generation gamma-arrays & DAQ systems

The ATOMKI solution: 4-channel DAQ module developed for miniPET

BlockBlock scheme scheme ofof miniPET2proposed DAQDAQ module module

Bicron LYSO MEMEC miniModule with Gigabit Ethernet Prelude P420 24x24 FastFast Fast 1.9x1.9x12 mm 3 preamppreamp ADC LVDS Base line restoration X+ µC Quad Pulse recognition PowerPC X- F Ethernet Time stamp CsI Y+ I 10/100/1000 Energy calculation module Y- F H BaseT W P O M H Hamamatsu Local clock A Y H9500 PMT C and/or To be developed at ATOMKI: Optical HV IP core - managing PID, Energy,etc. Module PSPMTCsI Analog FPGAfrom Xilinx digitalized V4 FX12 signals in the AnalogAnalog Devices Xilinx Virtex-4 FPGA frontendfrontend AD9229-65 MEMEC miniModule Future Improvements: position sensitive E-E particle discrimination

In iThemba LABS DSSSD + CsI(Tl) arrays have been used (in collaboration with ATOMKI)

DSSSD 6Li( 3He, t)6Be at 50 MeV 3He 4He

CsI(Tl)

The AFRODITE chamber equipped Example E vs E spectrum produced by with 60x60x0.3 mm 3 Si DSSSD + the DSSSD + CsI(Tl) arrays on the left 2x2 arrays of 30x30x3 mm 3 CsI(Tl) + Si pin-PD (P.Papka's curtesy) Summary of Perspectives and Future Developments of DIAMANT

Short-range plans: Continue nuclear structure studies with EXOGAM using the stable and high-intensity radioactive beams available at GANIL: We propose DIAMANT for the nuclear spectroscopy community for studying nuclei for E γ > 200 keV. We plan to use it also with AFRODITE (TLABS, SA) and even to test it with the demonstrator version of the future AGATA array. With the technical developments outlined, there is hope for a succesful continuation!

Long(er)-range plans: Develop a prototype CsI+APD detector and dedicated Preamplifier: (Plan) Test its applicability for low-energy coincidence spectroscopy Use Digital Signal Processing to replace the present VXI electronics (Needs financing!) for compatibility with EXOGAM-2 and AGATA Options: Use the 4-channel module under development in ATOMKI (Plan within EXOGAM-2) Dedicated Xilinx programs to be developed for CsI detector signals at ATOMKI; Use the circuitry under development for the Ge detectors of AGATA/GRETA [I.H. Lazarus et al, The GRT4 Pulse Processing Card ...., 2003] Need help from physics groups to realize the planned Future Developments of DIAMANT

List of volunteers : Form of contribution :

To be completed ! Thanks

Members of the DIAMANT Collaboration:

J.N. Scheurer et al 1, G. La Rana et al 2, J. Gál 3, G. Hegyesi 3, G. Kalinka 3, J. Molnár 3, B.M. Nyakó 3, K. Juhász 4 A. Algora 3, Zs. Dombrádi 3, J. Timár 3, L. Zolnai 3

1CENBG, CRNS-IN2P3-Université de Bordeaux I, Gradignan Cedex, France 2Dipartimento di Fisica, Universita di Napoli and INFN, Napoli, Italy 3Institute of Nuclear Research, (ATOMKI), Debrecen, Hungary 4Faculty of Informatics, University of Debrecen, Debrecen, Hungary

To all colleagues of the many physics groups from different EU and outside laboratories who provided material about the status of data analysis and results of experiments