SuperCHICO; a 4π heavy-ion detector C.Y. Wu and D. Cline An arsenal of auxiliary charged-particle detectors must be an integral component of GRETA in order to achieve and exploit the ultimate in sensitivity and selectivity for nuclear science The 4π heavy-ion detector, SuperCHICO, is designed to exploit γ-ray tracking arrays for study of quasi-binary reactions at both stable and exotic beam facilities, that is: Coulomb excitation Single and multi-nucleon transfer reactions Deep inelastic reactions Fission SuperCHICO is based on the successful CHICO detector.

Ge detector CHICO Scattering angle: 12   85  (Front Part) 95   168  (Back Part) Azimuthal angle total: 280  of 360  Position resolution:  1  in  and 9.3  in  Solid angle: 69% of 4π Time resolution:  500 ps Mass resolution Δm/m = 5% Q-value resolution: ≤ 20 MeV CHICO * M.W.Simon, D. Cline, C.Y. Wu R.W. Gray, R. Teng. C. Long Nucl. Inst. Meth. A452 (2000) 205 * Work supported by the NSF

Doppler-corrected γ-ray spectra 1358 MeV 238 U on 170 Er Raw data Correction for U-like recoils Correction for Er-like recoils C.Y. Wu, D. Cline, et al, Phys. Rev. C61 (2000) 21305(R) CHICO/Gammasphere

CHICO-GS Operation CHICO-Gammasphere ideal for quasi-binary type reactions: Coulomb excitation transfer reactions deep-inelastic reactions fusion-fission reactions 24 experiments performed by 58 researchers from 17 institutions 48 publications, including 2 Phys. Rev. Lett. and 2 in Phys. Lett. 5 Ph.D. theses completed

SuperCHICO performance Angular coverage:20 o ≤ θ ≤ 85 o, 95 o ≤ θ ≤ 160 o ; 280 o in φ Angular resolution:Δθ = 1 o, Δφ = 1.4 o Solid angle:66% of 4π Time resolution:Δt = 500ps Mass resolution for kinematic coincidence:Δm/m = 5% Q-value resolution:≤ 20 MeV GRETA Doppler-corrected γ-ray resolution: ~ 0.3%

Advantages of SuperCHICO Large solid angle:Study weak exotic beams or low cross-section processes Large angular coverage:High kinematic coincidence efficiency Large range of impact parameters Angular and time resolution:Mass, Q-value resolution; high selectivity Achieve maximum Doppler-corrected γ-ray resolution for GRETA: Identify γ-rays from each fragment Very high count-rate capability:> 100kHz Hardness to radiation damage: High background suppression: PPAC blind to light ions, Kinematic coincidence requirement Minimal mass: Minimal γ-ray absorption and Compton scattering Low initial and operational costs: only 80 channels of electronics for 26,000 pixels

Cost details: LLNL estimate Assume most engineering carried out at LLNL Mechanical –Design:  22 weeks, $100k –Fabrication: $100k Electronics –Amplifier Replace CHICO hybrid circuit design Design:  6-8 weeks, $80k Fabrication: $80k –Downstream Recycled from CHICO Replaced by FADC and computer-controlled gas-handling system at some future date Total cost: $360k excluding scientific manpower at LLNL and Rochester. St. Louis Workshop

Future Opportunities SuperCHICO plus GRETA will be a powerful facility for nuclear spectroscopy using either stable or exotic beams Stable beams: a) Probe quadrupole, octupole, or pairing collective modes of motion in nuclei. b) Extend studies of transuranic nuclei to higher spin, ≥40ħ c) Probe collective bands built on unusual isomeric states and determine the Eλ and Mλ matrix elements involved to probe both collective and shell structure. Exotic neutron-rich beams: a) Explore the evolution of collectivity and shell structure with isospin. b) Deep inelastic and transfer reactions will extend range of neutron-rich nuclei. c) Pair transfer to probe neutron pairing correlations in neutron-rich nuclei d) Exploit isomeric beams to probe unusual configurations in nuclear structure