single VIP unit module detector is made of 4 CdTe pixelated detectors
(see Figure 1). CdTe can provide an energy resolution as low as 1.5%
FWHM for a 511 keV incoming particle, which will make the
contribution of scattered events to the final data-set negligible.
Each one of the four detectors has a parallelepiped shape and
consists of ∼ 200 voxels. Each voxel has a size of 1mm x 1mm x 2mm
and is connected to its own independent readout channel for the
energy, position, and arrival time of the gammas. Each readout
channel is bonded to a microchip hosting a fully integrated front-end
electronic as designed and developed by the VIP project.
VIP unit detector module is bonded to a thinned read out chip (ROC)
and then mounted on a kapton printed circuit board (PCB). A 2000 V
high voltage is applied with the electric ﬁeld directed
perpendicular to the surface so that the detector can be run inside a
magnetic field without affecting the signal, for hybrid MRI/PET
operation. The ROC and the PCB are 50 µ m thick each, whereas for
the conductive glue between the ROC, the PCB, and the CdTe detectors
a thickness of 15 µm is assumed. The combined attenuation coefﬁcient
of the passive material accounts for less than 2% compared to 2 mm
The VIP modular design is extremely versatile with the possibility to build virtually any detector geometry by stacking the needed number of modules in arbitrary patterns. The resulting detector has a 3-D segmentation with a channel density of ∼ 470 voxels per cm3.
Figure 1. The basic VIP unit module. It consists of 4 CdTe pixelated detectors of 200 voxels each with trapezoidal shape and a pixel pitch of 1 mm. The smaller base of the first detector is 2 cm, whereas the smaller base of the 4th detector is 2.37 cm. The detector thickness is 2mm.