Characterization of blue sensitive 3 × 3 mm²SiPMs and their use in PET

Abstract

Three types of SiPMs (Silicon Photomultiplier) with an active area of 3 × 3 mm 2 manufactured by KETEK with cell sizes of 50 µm (PM3350), 60 µm (PM3360) and 75 µm (PM3375) have been investigated. All devices have optical trenches in between the cells to suppress direct crosstalk. Their breakdown voltage at room temperature is about 23 V and the gain at an overvoltage U over = 3.4 V is > 6 • 10 6 . The temperature variation of the breakdown voltage is < 16 mV/K and the gain coefficient with temperature is < 1% for overvoltages U over > 1.7 V. The photodetection efficiency (PDE) at 420 nm and U over = 3.4 V is 51% for PM3350, 55% for PM3360 and 58% for PM3375. At U over = 3.4 V, the dark count rates are < 470 kHz/mm 2 at 20 • C and the afterpulse probability is < 9% at −20 • C. Single photon timing of 230 ps FWHM for PM3350, 320 ps for PM3360 and 375 ps for PM3375 have been achieved. To test their performance in PET (Positron Emission Tomography), energy spectra of 22 Na with LYSO (Lutetium Yttrium Oxyorthosilicate, Lu 1.8 Y .2 SiO 5 :Ce) and GAGG (Gadolinium Aluminum Gallium Garnet, Gd 3 (Ga,Al) 5 O 15 :Ce) scintillators with a size of 2×2×6 mm 3 have been acquired. The saturation corrected energy resolution (FHWM) at 511 keV was with LYSO 12.3% for PM3350, 13.4% for PM3360, 12.4% for PM3375 and with GAGG 10.8% for PM3350. Coincidence timing (FWHM) at U over = 3.4 V was with LYSO 174 ps for PM3350, 178 ps for PM3360, 157 ps for PM3375 and with GAGG 430 ps for PM3350.

Performance analysis of digital silicon photomultipliers for PET

“…Intrinsic properties of silicon photomultipliers are comparable for the studied DPC and analog devices. Both, the breakdown voltage temperature coefficient and optical crosstalk (see sections 3.1 and 3.2), are similar to the ones of state-of-the-art analog SiPMs [37]. The DPC's behavior against temperature and bias voltage variations is also as expected for a SiPM.…”

“…The optical crosstalk probability between cells within one pixel is extracted from a dark-count generated single photon spectrum and defined as the ratio of "counts >1 photon-count" to "number of total photon-counts", as proposed in [37]. It has been measured in one slave pixel triggered randomly by a master pixel located in opposite corners of the tile using the neighbor logic [7].…”

Spatially resolved dark count rate of SiPMs

“…The gain G is measured by flashing the SiPM with a pulsed laser (406 nm, 1 kHz repetition rate, < 70 ps pulse width) which drives the SiPM into saturation (number of emitted photons >> number of micro-cells). For each flash the SiPM signal is integrated for a duration of 450 ns and the gain is determined by dividing the integral charge by the load resistance, the number of SiPM micro-cells, and the elementary charge [12]. The breakdown voltage V bd is obtained by extrapolating G(V ) to G(V bd ) = 0.…”

Characterization of the photo-detection efficiency temperature dependence of silicon photomultipliers from -30°C to 70°C

“…The three different devices were selected to compare different generations of SiPM designs. The KETEK PM3350 [8,9] has been available on the market for many years whereas the NUV-MT technology from Broadcom [10] was recently released. Both SiPM deploy a planar design for the single-photon avalanche diodes.…”