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Silicon strip detectors and plastic scintillator hodoscope for Coulomb dissociation experiments

This study explores the use of silicon strip detectors and a plastic scintillator hodoscope to study nuclear astrophysics and nuclear structure through Coulomb dissociation experiments.

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Silicon strip detectors and plastic scintillator hodoscope for Coulomb dissociation experiments

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  1. Silicon strip detectors and plastic scintillator hodoscope for Coulomb dissociation experiments Naohito Iwasa Dept. Phys., Tohoku Univ.

  2. Coulomb dissociation method powerful tool to study nuclear astrophysics and nuclear structure. Motivation 7Be+p 8B • The 7Be(p,g)8B reaction: solar neutrino • 8B＋high-Z target→7Be+p 8B + 208Pb → 7Be + 1H + 208Pb 　　 　　　　↓ (~1000/MeV) 8B + g → 7Be + 1H ↓ ~1000 7Be + 1H → 8B + g High precision (Large cross section) Thicker target can be used (high energy) High detection efficiency (charged particle detection) Momenta and scattering angles of 7Be and p

  3. 1989～2000 (RIKEN) 13N(p,g)14O: SSD+CsI(Tl) EMRIC 7Be(p,g)8B, 8B(p,g)9C, 11C(p,g)12N, 12N(p,g)13O: plastic scintillator hodoscope Hodoscope 1 1m×1m active area ΔE:5mmt, E1: 60mmt ΔE: X:100mm× 1m E1: Y: 60mm × 1m 10 × 16 segments He gas Hodoscope II 1m×1m active area ΔE:5mmt, E1: 60mmt , E2: 60mmt ΔE: X:100mm(or 40mm)× 1m E1,E2: Y: 75mm(or 38mm) × 1m 13 × 16 segments position resolution θ<1.1 degrees vacuum Hisanaga, diploma thesis Scattering angles: position of hit on hodoscope time difference momenta: TOF(s～0.6ns) PI: ΔE-E

  4. 8B results（example） 1. Motobayashi et al., Phys Rev. Lett. 73, 2680(1994) Iwasa et al., J. Phys. Soc. Japan, 65,1256(1996) 2. Kikuchi et al., Phys. Lett. B391, 261 (1997) Eur. Phys. J., A3, 213 (1998) S17=18.9±1.8 eV b

  5. Heavier system (2000～) Particle identification of heavy ions(HI) using plastic scintillators is difficult!! → Silocon strip detectors are installed between the target and hodoscope. to measure scattering angle of proton and HI, PI and kinematical energy of HI Energy loss of HI is higher than that of proton (～600 for 35K+p case) Detection efficiencies of proton and HI are high. 4-5 layers 1st and 2nd layers: silicon strip detector 3rd&4th(&5th&6th) layers: silicon detector ～68cm

  6. Silicon strip detectors 1st: x 2nd : y p side n side 3,4,5,6 layers • 21 silicon detectors (50×50 mm2 active area, 0.3 mmt , 5mm pitch, mounted on 56×56 mm2 frames) Δθ～ 1.5 degree(σ) • 21 silicon detectors → 5-7 groups. • p side: high gain: proton O, HI: overflow • n side: low gain: proton ×, HI: O p: Cf=33pF or 47pF, n: Cf=270pF 23Al,27P: 8 detectors 20Mg, 31Cl, 36Ca : 21detectors

  7. readout p side High gain PA SA ADC V785 Cf=33(47)pF Bipolar P: 1MeV ～1mV HI: Noise- proton separation no saturation Z≦17(27P) OK Z= 20(36Cl) we will try. RC～0.1ms　→　resolution? Low gain n side PA SA ADC V785 Bipolar Cf=270pF TDC V775 delay CFD TFA

  8. SSD strip side HI overflow noise H He Results of silicon detectors Cf=33pF T. Gomi, Thesis E resolution 0.6% PI and energy of HI DE[ch] angle hodoscope He d PI of proton Velocity of proton DE[ch] E[ch] p H Invariant mass TOF+offset[ns] TOF+offset[ns]

  9. Results T.Gomi et al., J. Phys. G31, S1517 (2005). Y. Togano et al., Nucl. Phys. A758, 182c (2005). 3.4 1.372 1.77 2.7 2.0(new!) 0.55 0.125 1.6 23Al 22Mg+p 1.2 0.90 26Si+p 27P

  10. Experiment at higher energies • GSI: Coulomb dissociation of 8B at 254AMeV Coulomb dissociation of 6Li advantages High beam intensity, thicker target, M1 component↑, E2 component ↓ On the other hand, DE-E method → Br-DE-TOF method reaction loss several% → several 10% forward focus → precise measurements of scattering angle and momenta is necessary

  11. GSI (8B) 254AMeV 8B 1.6T Silicon strip detector 58×58 mm2, 0.3mmt, 0.1mm pitch GASSIPLEX+CRAM

  12. GSI (silicon strip detector) Silicon strip detector 58×58 mm2, 0.3mmt 0.1mm pitch single side 576 ch×4 = 2304 ch GASSIPLEX chip (16ch/chip, 64ch/board) (preamp+shaping amp+multiplexer) Analogue multiplex technique + CRAM

  13. Vertex z-vertex position SSD1/SSD2 SSD3/SSD4 y Target p Z x q17 7Be GSI experiment Y X Y X 4.6mrad 31cm 14cm background fee

  14. Results • Iwasa et al., Phys. Rev. Lett. 83, 2910 (1999) S17=20.6±1.2±1.0 eV b • Schümann et al, Phys. Rev. Lett. 90, 232501 (2003). • Phys. Rev. C73, 015806 (2006). S17=20.6±0.8±1.2 eV b Adopted: 19+4-2 eV b 4.8mrad, 0.3%

  15. Conclusion • Silicon strip detectors + plastic scintillator hodoscope → useful to study unbound states relevant to nuclear astrophysics and nuclear structure for A<40 • For A≧40, other methods should be considered. higher energies ΔE(HI)/ΔE(p)～2000 for 101Sb→ Sn+p or RP process A<110 • Pre-AMP and AMP with high dynamic range are needed. • VA chips with high dynamic range: AMS-02, VA32HDR11 • For lower noise level, development of PreAMP, AMP chips is desired.

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