08/08/091 Towards Super-Hercules and Nanoball Walter Reviol, Demetrios Sarantites Washington University, St. Louis, Missouri, USA ATLAS User Workshop, Argonne, IL, Aug. ’09

08/08/092 Hercules – a detector for residues and fission fragments 64 fast-plastic detectors (1 mg/cm 2 ). Arc-type light guides (Δθ=5.6 o ). Light guides serve as “elastics stopper”. Recent improvement: small magnets to deflect target electrons. 21 cm θ = 4.1 o o,D tgt = 23.2 cm Residue gated “Raw” 18 O+ 207 Pb, E lab =96 MeV Limitations in count rate and position resolution are due to the still quite large detector size.

08/08/093 # det. elements (pixels) 64 Active fraction surface0.89 Pixel size (mm 2 )6x6 “Overall” light guideyes 8x8 Multianode PMT (Hamamatsu 8500) The light guide is a 0.15-mm thick plastic sheet. The PMT glass window causes cross talk (established by trying also “individual” light guides). The cross talk can be turned into an advantage (tracking). Four PMT’s will be arranged in a “Gobi” geometry.

08/08/094 Super-Hercules: Status and Design Considerations Source test ( 252 Cf) has lead to a workable Super-Hercules prototype. Use cross talk for position tracking. –PH(cross-talk signals)/PH (central hit) correlates with hit position. –Position resolution ≈ 1mm (inner pixel) to 2 mm (outer pixel). –Have algorithm. Beam test ( 16 O+ 197 Au), to learn about count-rate dependence of parameters, is carried out as we speak. Considerations for a Four-8x8-PMT device: –Keep up with θ and φ resolution for Gretina (Δθ=1.8 o ). –Keep # electronics channels at 256 channels per parameter. –Use higher granularity (factors of 10 [tracking], 2.5 [w/o tracking] w.r.t. Hercules), to take more beam. –Angular range depends on experiment (e.g. θ < 25 o, D tgt =11cm). –Modernize analog electronics (32-channel CFD with veto capability) and use read-out chip (PSD + chip delay).

08/08/095 Super-Hercules - Additional Thoughts Possible application for binary-reaction experiments in inverse kinematics: Detector in Super-Hercules geometry with the “Microball material” CsI(Tl). Example: 142 Xe + 11 B single-proton or neutron transfer (Caribu beam). Geometry consideration for binary reaction in inverse kinematics: The grazing angles 40 o, the elastics rates are sometimes too high. Hence the significant region for solid angle coverage is 3 o to 30 o. Small Δθ and Δφ desirable [for dσ/dΩ TLF (θ)]; Microball geometry is not optimum. Measurement and additional requirements: The observables are TLF particles and PLF γ rays. The important derived quantity is dσ/dΩ PLF (θ); Doppler correction of PLF γ rays benefits from small Δθ and Δφ as well. If Z-identification becomes an issue, use fast-plastic + CsI(Tl) phoswich. For θ > 30 o coverage, more 8x8 PMT’s could be added modularly.

08/08/096 Nanoball vs. Microball Microball Refresher: –4π CsI(Tl) device with high efficiency and reasonably high granularity. –Excellent p, α, etc. “PID”; the device helps sharpen γ-ray spectra. –Rather slow detectors: “PID” needs 8 µs. Microball has been also used in stable-beam inverse-kinematics experiments: 9 Be( 136 Xe, 8 Be), 13 C( 136 Xe, 12 C) 137 Xe single-neutron transfer (Radford et al.). Nanoball concept: 4π Trans-Stilbene (organic scintillator) device with Microball’s granularity. Rather fast detectors: “PID” needs 130 ns. Detectors have indeed “PID” – see next slide. Detector material will be commercially available. >100

08/08/097 PID Plot for Stilbene Notice short charge-integration gates [50 x faster than CsI(Tl)]. 97% pure material “home grown”

08/08/098 Thanks for your attention!