C.M. Petrache Trento, January 16-20, 2006

1. Design study for a 4p ancillary detector for light charged particles to be used together with g-ray arrays in fusion-evaporation and direct reactions C.M. Petrache, D. Mengoni, M. Fantuzi – Camerino G. Ambrosi, E. Fiandrini – Perugia G. Prete, A. Gadea, G. De Angelis, R. Ponchia, G. Bassato – Legnaro E. Farnea, F. Recchia – Padova M. Boscardin, C. Piemonte, M. Novella, N. Zorzi - Trento C.M. PetracheTrento, January 16-20, 2006

2. Physics Case Study of the structure of exotic nuclei using secondary radioactive beams (SPES@LNL, SPIRAL2@GANIL) using Fusion-evaporation reactions in inverse kinematics to measure Energy and Angle of light charged particles (p,a) with Ancillary detectors coupled with gamma arrays using Direct reactions in inverse kinematics to measure Energy and Angle of the recoiling light particle

3. Ref.: Agata Proposal. http://agata.pd.infn.it AGATA

4. TRACE Fusion-evaporation -> different from TIARA & MUST (transparent, high granularity forward, low-energy threshold backward) Direct reactions -> similar characteristics like TIARA & MUST

5. AGATA + reaction chamber • = 40 cm Large space for ancillary detectors & electronics

6. Monte Carlo simulations with GEANT4 for the barrel geometry

7. Main requirements of our detector for light charged particles • Detector specifications: • Efficiency • Geometry • Position resolution • Energy resolution • Time resolution • Energy range • ∆E-E technique & PSA • Electronics • ASIC’s • DSS

8. Main Requirements • High detection efficiency: it has to cover as much as possible the solid angle, with a high granularity in order to minimize multiple hits probability. • Transparent to gamma rays for the coupling with a gamma spectrometer. • Fine discrimination among the various particles: protons, alphas and heavier ions. • Good position resolution: for Doppler correction and good energy resolution. • Good energy resolution: for detailed spectroscopy. • Good time resolution: for TOF discrimination of light ions. • Wide energy range:measurement of various reactions. • Pulse shape analysis: fast DSS to achieve very low thresholds.

9. Detector Specifications • Detector: made of Silicon to minimize the absorption of gamma rays, thin junction window (0.1mm). • Geometries: • ∆E: Si-pad det. <150 m thick, pad 2x2 mm2, strip 2 mm • E: Si-pad det. >1.5 mm thick, pad 2x2 mm2, strip 2 mm • Dimensions:40 x 80 mm2 • Angular Resolution: 1°, 1-2 mm at 15 cm • Energy resolution: <50 keV for 5 MeV a-particles • Wide energy range: 200 keV-20 MeV for p, 80 MeV for a • Time Resolution: 500 ps for A=8 & 2 MeV/u • Pulse shape analysis: 2 GHz, >10 bits • Coupling: AC

10. Coupling with AGATA demonstrator

11. Coupling with AGATA 2p

12. Lateral faces8 DE-E modules with orthogonal Si-strip

13. Forward 4 DE-E modules with Si-pad Backward 4 DE-E modules with Si-strip

14. Transparency EUCLIDES: EdE Si-ball for charge particle detection and identification. ΔE ~ 130 um E ~1000 um TRACE: EdE Si-Pad for charge particle detection and identification. ΔE ~ 150 um E ~1500 um

15. First AGATA Experiment (Sept. 2005 IKP KOLN) Goal: checking the feasibility of tracking with the first cluster prototype under (future) AGATA working conditions.

16. Experimental apparatus Ancillary device: DSSD 32 rings 64 sectors Ge detector: firstAGATAsymmetric cluster (3 detectors)

17. 48Ti(d,d)48Ti* 48Ti*(d,p)49Ti* Evidence For Various Reactions FWHM = 300 keV

18. Simulated System out Event generator: (d,p) reactions in inverse kinematics Ref.:DWBA. http://spot.colorado.edu/~kunz/DWBA.html in MAIN FEATURES: 1.Cross section produced with DWBA and loaded in the C code. 2.Energy lost of the beam in the target before interaction 3.Proton energetic and directional straggling 4.Recoil energetic straggling after interaction 5.Gammas loaded from an input file in the generator

19. Simulated Doppler correction FHWM 33 keV (cluster) 15.6 keV (single) 7 keV 4.3 keV (single)

20. Electronics Number of channels: ~ 8000 Dynamic range for Light Charged Particles 0.2 - 20 MeVSi = 56x103 - 6x106 e- = 9 fC – 1 pC Ranges in silicon for alphas: 60 MeV 1.5 mm 80 MeV 2.5 mm Ranges in silicon for protons: 15 MeV 1.5 mm 20 MeV 2.5 mm Pulse shape analysis: DSS 2 GHz, 10 bits Multiplexer based system for reducing the number of ADS and feed-through by a factor of ~ 100 R&D for ASIC with PSA

21. Electronics • ASIC read-out chips: to reduce at minimum the very limited space available around the target, the large number of electronic channels associated with the segmented detectors. • Tests of Si-pad detectors coupled via various boards to different ASIC chips are under way at Legnaro and Camerino. Chip Board VA32C2-TA32CG VA_TA_HPD2_H7546 VA32_HDR_11-TA32 VA_TA_HPD2 VATAGP3 – 128 channels, sparse read-out, range 18 fC System Test VADAQ

22. Tests have been performed on both Micron detectors, on several channels with either the ASIC or standard electronics, leading to encouraging results. ASIC electronics (VA32_HDR11 chip a-source: 241Am source in air at 1 cm FWHM ~ 500 keV @ 5.5 MeV (9.1%) Standard electronics a-source: 241Am source FWHM ~ 70 keV @ 5.5 MeV (1.3%)

23. 1 mm thick Sintef detector + ASIC (VA32C2-TA32CG) • γ-Sources: 241Am, 57Co • energy resolution: ~ 6 keV @ 60 keV (10%)

24. New Si-pad Detectors from IRST - Trento STRIP: 64 strips/side; strips orthogonal on the two sides strip pitch 500 µm Two different strip width: 300 µm (STRIP1) 200µm (STRIP2). • Thickness 1.5 mm • Thin junction window • (up to 100÷200 nm) • High resistivity • (>30 kΩ · cm) • Bias voltage: 200÷300 V • (multi guard rings) • One single metal layer • Near edge bonding contacts strip1 PAD2 PAD1 strip2 PAD3 PAD1=AC, 6x5 pads, 4x4 mm2 PAD2=AC, 8x32 pads, 1x1 mm2 PAD3=DC, 8x8 pads, 2x2 mm2

25. PAD1= AC coupled 6x5 pads 4x4 mm2 Signal extracted on the opposite sides to reduce strip length. 120 mm 140 mm 500 mm

27. Tests of Si-Pad Detectors and Read-out ASIC Electronics SINTEF MICRON Rear and front side of the adapter board on which the SINTEF Si-pad detector has been bonded. The adapter board can be inserted on the VATA-HPD2-H7546 read-out board, endowed of a suitable pin mask.

28. Results on Si-pad Detectors and Read-out Electronics The Si-pad detectors were bonded to the electronic read-out board and characterized in the clean room of the INFN Sezione di Perugia. Detailed measurements of Si-pad detectors of various geometries with either classical or ASIC read-out electronics were performed at the University of Camerino, Legnaro National Laboratory (LNL) and at INFN Sezione di Perugia. The leakage current as a function of the bias voltage in 1 mm thick detectors. The red lines represent two different measurements on the same detector. The capacitance as a function of the bias voltage in 1 mm thick detectors. The detector is fully depleted at around 150 V.

29. Equivalent noise charge (ENC) of the VA32_HDR11 chip, in units of electron charge, as a function of the input capacitance has been measured. A linear fit of the experimental data is also shown, which is given by the relation: The linearity of VA32C2 chip extends up to 220 keV, and the ENC curve is described by the relation: The statistical fluctuation for 60 keV photons in Silicon is 130 e-, which gives an energy resolution of 0.8%. A capacitance of ≈ 2.4 pF gives an ENC of ≈ 230 e-, which leads to an energy resolution worse than 3%.

30. Conclusions • An ancillary detector can be designed for fusion-evaporation and/or direct reactions in inverse kinematics at energies of 20 MeV/u. • An effort should be done to avoid duplicates and to develop convergent complementary set-ups • The chips have ENC values which worsens the performance of the Si-pad detectors, limiting the energy resolution. The obtained results disagree with the technical characteristics given by the producer. • R&D on ASIC’s and PSA.

31. SINTEF • thickness 1.0 mm • 6 x 21 pads • typical pad size:1.8x1.8 mm2 • Bias Voltage: 150 ÷300 V • AC coupled • A guard ring to allow a more stable operation at full depletion. The pads are connected via strips to the bond pads located on one side of the detector, suitable for wire bonding to a PCB read-out board.

34. Tests of Si-Pad Detectors and Read-out ASIC Electronics Experimental set-up used to test the hybrid chips. The whole system is inserted in a closed metallic cage put to mass, to prevent the influence of the external electric field and light. The image on the right is the VA-DAQ read-out system which is connected to the parallel port of the PC.

35. MICRON Device Type:IMAGE PIXEL ARRAY – 500 • thickness ~ 500 μm • 5x12 pads • pad size 3.75x3.75 mm2 • full depletion voltage:~ 50V • DC coupling As the detector was delivered completely naked, a self-made AC circuitry was used for the coupling either with the ASIC and the standard DAQ system.

36. More realistic event generators are needed to make (usefull) simulations. The analysis of the experiment is still going on, looking for the actual value of the resolution, achievable in working conditions. Still waiting for thicker Si prototype. An in-beam test is going to be planned. Summary

37. Doppler Correction Ref.: E.Farnea, F.Recchia. LNL Annual report 2003. FHWM 69 keV 7.8 keV

38. Simulated Results E rings E sectors slices E E Ge

39. Inverse Kinematics

40. Experimental Data 49Ti @ 1381.75 keV FWHM 35 keV (single crystal) 1381.75

41. Si-pad detectors for X-rays developed at UNICAM-PG-LNL Micron: 300mm, 12x5 pads of 4x5 mm2 Sintef: 1 mm, 21x6 pads of 2x2 mm2 AGATA Principal characterictics Ancillary for HPGe g-ray array • Solid angle: 4p • Angular/spatial resolution: 1 to 2 mm • Energy resolution: ~1 keV FWHM @ 60 keV • Time resolution: ~10 ns (FWHM) • Dynamic range: 20 - 500 keV • Rate and multiplicity: 1-10 kHz , 1-10 pads

42. PAD2= AC coupled 8x32 pads 1x1 mm2 Signal extracted on the opposite long sides to reduce strip length. 120 mm 140 mm 250 mm