YRAST Ball

The YRAST Ball (the Yale Rochester Array for SpecTroscopy), a major new Ge detector array for high-resolution gamma-ray spectroscopy has recently been commissioned at the Wright Nuclear Structure Laboratory at Yale University, where it is anticipated that it will become the workhorse for the nuclear structure program. The YRAST Ball, with 28+ Ge detectors and a total photo peak efficiency of 2% is the worlds largest university based Ge detector array.

The YRAST Ball framework is modular and is designed to accommodate twenty-eight (plus) Ge detectors centered on the target. The detector arrangement is flexible to facilitate the variety of detector types which are used in YRAST Ball. Detectors are mounted in four rings making angles of 163⁰ (3 positions), 135⁰ (8 positions), 90⁰ (9 positions), and 55⁰ (8 positions) with respect to the beam axis. The forward 35⁰ cone is vacant to allow easy access for auxiliary detectors, such as the NYPD (New Yale Plunger Device) gamma-ray plunger which is used for lifetime measurements of short lived nuclear states. Additional Ge detectors may also be mounted in these forward positions to facilitate certain experiments.

Currently 17 ~25% and  1 70% (efficiency measured relative to a standard NaI scintillator) Compton suppressed Ge detectors, 4 Low Energy Photon Spectrometers (LEPS) and 4 150% segmented CLOVER Ge detectors are available for use with the YRAST Ball. Additional detectors, including an additional CLOVER detector, will be added in the near future.

The YRAST Ball was commissioned at the end of 1997 with a reception held in the WNSL control room, attended by various departmental and DOE folk. The official tape cutting ceremony was performed by Rick Casten and Con Beausang.
 
 
 
 
 

The first experiment, with 20 Ge detectors, was carried out in early December 1997. The reaction ¹⁴N + ¹⁹⁷Au was used to study high-spin states in light Rn nuclei in the vicinity of 205Rn.

A variety of auxiliary detectors are available for use with YRAST Ball. In addition to the NYPD these include a 38 element BGO sum-energy multiplicity filter, our solar cell array for heavy charged particle detection (SCARY, the Solar Cell ARray at Yale) and an array of 12 neutron detectors.

YRAST Ball will be used as part of the new program in gamma-ray spectroscopy at WNSL. It will be used for both high- and low-spin studies. If any outside users would like to request some beam-time, or would like to collaborate with the WNSL nuclear structure group, please contact Andreas Heinz at andreas.heinz@yale.edu.