J.D. Brown

The missing 12+ mirror state in 9B

Abstract The status of the mirror state in 9 B of the first excited 1 2 + 1.68 MeV state in 9 Be is reviewed. The experimental evidence is inconclusive except for an apparent peak recently reported in a spectrum from the 9 Be( 6 Li, 6 He) 9 B reaction. This reaction has been reinvestigated at the same energy and angle but with substantially improved resolution and statistics, and the present results provide no evidence for the previously reported peak. Spectra obtained at other energies and angles have very low background and yet similarly fail to exhibit a peak. In addition, no evidence for population of the mirror state is found in spectra taken for the reaction 10 B( 9 Be, 10 Be) 9 B at two bombarding energies. The energy and width of the expected 1 2 + state in 9 B remain open questions for which several different theoretical descriptions offer quite different predictions.

Measurement of high momentum transfer reactions by recoil detection at a cooler ring

Abstract A system for the measurement of medium-energy, high-momentum transfer reactions via detection of the heavier ion products has been developed. The system consists of a parallel grid avalanche counter, a proportional counter, and a large-area microstrip silicon detector array, all attached to a large-gap dipole magnet that bends the primary beam through 6° and sweeps the recoil ions into the detection system. The detector stack measures the energy, time-of-flight, nuclear charge, mass, and angle of recoil-ion emission products. Ray tracing gives the emission angle of the recoil ions at the target. The system was installed at the Indiana Cooler Ring and its advantages and use in a storage ring environment are discussed. Preliminary results of differential cross section measurements for the reaction 12C(p, π+)13C at Tp = 166 and 294 MeV are presented.

A readout system for microstrip silicon detectors

Abstract A readout system for Si microstrip detectors has been developed in which inductors are placed between each strip thus forming an LC delay line with the detectors intrinsic capacitance. Each strip in a 50-strip detector is resolved and a time resolution of 800 ps is obtained with 5.49 MeV alpha particles. Only two fast signals and an energy signal are needed from an entire detector in order to determine a particles time of arrival, position and energy. The system requires little power and is made of components that are available commercially.

Recoil ion detection system for the IUCF cooler

The detection of neutral particles or exotic ejectiles in reactions initiated by medium energy probes is discussed. (AIP)