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

Motivation Coulomb dissociation method powerful tool to study nuclear astrophysics and nuclear structure. 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

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 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

8B results（example） S17=18.9±1.8 eV b 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

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

Silicon strip detectors 1st: x 2nd : y p side n side 3,4,5,6 layers 23Al,27P: 8 detectors 20Mg, 31Cl, 36Ca : 21detectors 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

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 TFA CFD delay TDC V775

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

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

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

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

GSI (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

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

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%

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.