The Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei, GRIFFIN, is a new experimental facility for radioactive decay studies at the TRIUMF-ISAC laboratory. The performance of the 16 high-purity germanium (HPGe) clover detectors that will make up the GRIFFIN spectrometer is reported. The energy resolution, efficiency, timing resolution, crosstalk and preamplifier properties of each crystal were measured using a combination of analog and digital data acquisition techniques. The absolute efficiency and add-back factors are determined for the energy range of 80–3450 keV. The detectors show excellent performance with an average over all 64 crystals of a FWHM energy resolution of 1.89(6) keV and relative efficiency with respect to a 3 in . × 3 in . NaI detector of 41(1)% at 1.3 MeV.

Characteristics of GRIFFIN high-purity germanium clover detectors

Gamma ray spectra of two (p,γ) resonances have been utilised for the characterisation of the Clover detector at energies beyond 5 MeV. Apart from the efficiency and the resolution of the detector, the shapes of the full energy peaks as well as the nature of the escape peaks which are also very crucial at higher energies have been analysed with special attention. Proper gain matching in software have checked deterioration in the energy resolution and distortion in the peak shape due to addback. The addback factors show sharp increasing trend even at energies around 11 MeV.

Characterisation of a Compton suppressed Clover detector for high energy gamma rays (⩽11MeV)

High spin structure of 136Ce

The development of a digitizer based pulse processing and data acquisition system for γ -ray spectroscopy with large detector arrays is presented. The system is based on 250 MHz 12-bit digitizers, and is triggered by a user chosen multiplicity of Compton suppressed detectors. The logic for trigger generation is similar to the one practised for analog (NIM/CAMAC) pulse processing electronics, while retaining the fast processing merits of the digitizer system. Codes for reduction of data acquired from the system have also been developed. The system has been tested with offline studies using radioactive sources as well as in the in-beam experiments with an array of Compton suppressed Clover detectors. The results obtained therefrom validate its use in spectroscopic efforts for nuclear structure investigations.

A Compton suppressed detector multiplicity trigger based digital DAQ for gamma-ray spectroscopy

A gamma spectrometer composed of two Clover Ge detectors in close geometry is described. The advantages and drawbacks of the different modes of operation are investigated. The use of offline coincidence analysis for substantial background reduction is presented and an experimental approach for the determination of the summing correction factor is formulated.

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Gamma spectroscopy using two Clover detectors in close geometry

The Clover detectors in their addback mode are excellent tools for detecting high-energy gamma rays (⩾2 MeV ) . The characteristics of these detectors, at energies above 2 MeV , are usually determined from simulation data or from extrapolation of the empirical data. This is the first time that the characteristics of a Compton suppressed Clover germanium detector have been studied up to 5 MeV using a radioactive 66 Ga (T 1/2 =9.41 h ) source.

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P. Datta

Papers

Characteristics of a Compton suppressed Clover detector up to 5 MeV