Geant4 Simulations for the Radon Electric Dipole Moment Search at

Figure 2.7: One GRIFFIN/TIGRESS HPGe clover comprised of four individual crystals.
Each crystal is 90 mm in length and 60 mm in diameter and has an efficiency
of 40% relative to a standard 3”× 3” NaI(Tl) crystal for 662 keV γ rays.
14.5 cm. The front suppressors in this configuration also have the option of being
collimated with a dense metal (hevimet). The dense metal, composed mostly of
tungsten, prevents γ rays from directly hitting the front suppression shields.
The GRIFFIN spectrometer is very similar in external geometry to its sister array
TIGRESS (TRIUMF-ISAC Gamma-Ray Escape Suppressed Spectrometer) [33],
which currently resides in the ISAC-II experimental hall at TRIUMF. The primary
difference between the two designs is that a TIGRESS detector has each HPGe crystal
electrically segmented into 8 segments. This results in 32 electrical signals (plus
four addition core contacts) per clover, whereas a GRIFFIN detector will have only
4 electrical signals (the four core contacts) per clover. The principle reason for TI-
GRESS’s highly segmented crystals is to provide three-dimensional localization of
γ-ray interactions inside the crystals [34], which is necessary for experiments with
the accelerated radioactive ion beams at ISAC-II. GRIFFIN, on the other hand, will
reside in the ISAC-I hall and will be used primary as a decay spectrometer with
low-energy radioactive ion beams. The segmentation of the TIGRESS detectors is
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