Nuclear Physics Group


Figure 1 : Schematic of one hemisphere of the GRIFFIN gamma-ray spectrometer in its maximum efficiency configuration. The low-energy radioactive ion beam will be implanted in a thin tape in the middle of the central vacuum chamber, where the radioactive decays will take place.

Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei (GRIFFIN) is a new state-of-the-art high-efficiency gamma-ray spectrometer for decay spectroscopy research with low-energy radioactive ion beams. GRIFFIN will support a broad program of basic research in the fields of nuclear structure, nuclear astrophysics, and fundamental particle interactions.

GRIFFIN will be comprised of 16 large-volume "clover-type" high-purity germanium (HPGe) gamma-ray detectors, each of which contains 4 large germanium single crystals. All of the detector signals from GRIFFIN will be continuously digitized 100 million times per second (100 MHz) and processed in custom-designed digital electronics modules capable of complete data readout from the array with each of the 64 HPGe crystals recording as many as 50,000 gamma-ray interactions per second.

As shown in Figures 2 and 3, the gamma-ray detection efficiency of GRIFFIN will be approximately 17 times higher for 1 MeV gamma rays and 40 times higher for 10 MeV gamma rays, than the 8pi Spectrometer that currently supports the decay spectroscopy research programs of Canadian researchers and our international colleagues at the world-leading ISAC-I radioactive ion beam facility. As most GRIFFIN experiments will be performed in a coincidence mode in which at least 2 gamma rays from the same nuclear decay are measured in coincidence, the relevant figure of merit for the performance of the spectrometer is the square of the above efficiency ratio, i.e. a factor of ~ 300 increase in gamma-gamma coincidence efficiency compared to the current 8pi Spectrometer for typical experiments with ~ 1 MeV gamma rays. This enormous increase in gamma-ray detection sensitivity will revolutionize Canada's decay spectroscopy research programs at ISAC-I, enabling detailed studies of the most neutron-rich radioactive beams that will be produced by the current actinide production targets as well as the new ARIEL facility under development at TRIUMF.

GRIFFIN has been designed to incorporate all of the existing auxiliary detection systems currently operating with the 8pi Spectrometer, including:

  • the 20-element SCEPTAR plastic scintillator beta detector array,
  • the in-vacuum moving tape collector system,
  • the 5-element PACES Si(Li) conversion electron spectrometer, and
  • 8 of the 10 elements of the DANTE BaF2 fast gamma-ray timing array.

GRIFFIN has also been designed for full compatibility with the new DESCANT neutron detector array under development at the University of Guelph.

A full suite of beta-gamma-electron-neutron coincidence decay studies will thus be possible with GRIFFIN providing approximately 300 times the gamma-gamma coincidence efficiency of the current 8pi Spectrometer.

Figure 2 : Absolute efficiency of the GRIFFIN Spectrometer in its "maximum efficiency" (blue) and "optimal suppression" (red) configurations, compared to the efficiency of the current 8pi Spectrometer (pink) at ISAC-I, as a function of gamma-ray energy. Figure 3 Caption: Ratio of the efficiency of GRIFFIN, in its two configurations, to the current 8pi Spectrometer. The maximum efficiency configuration of GRIFFIN is 17 times more efficient in gamma-ray singles (~ 300 times more efficiency for gamma-gamma coincidences) at 1 MeV, and ~ 40 times more efficient by 10 MeV, than the current 8pi Spectrometer.

GRIFFIN in an $8.775M project funded jointly by the Canada Foundation for Innovation (CFI), the University of Guelph, and TRIUMF, with major in-kind contributions from TRIUMF and commercial vendors. With project initiation in 2011, GRIFFIN will begin early-implementation operation at ISAC-I in 2014 and will be completed and fully operational for fundamental discovery research with radioactive ion beams provided by ISAC in 2015.