V. Postolache

The test results of the Silicon Tungsten Tracker of DAMPE

V. Gallo∗1, G. Ambrosi2, R. Asfandiyarov1, P. Azzarello1, P. Bernardini3,4, B. Bertucci2,5, A. Bolognini2,5, F. Cadoux1, M. Caprai2, I. De Mitri3,4, M. Domenjoz1, Y. Dong6, M. Duranti2,5, R. Fan6, P. Fusco7,8, F. Gargano7, K. Gong6, D. Guo6, C. Husi1, M. Ionica2,5, D. La Marra1, F. Loparco7,8, G. Marsella3,4, M.N. Mazziotta7,, A. Nardinocchi2,5, L. Nicola1, G. Pelleriti1, W. Peng6, M. Pohl1, V. Postolache2, R. Qiao6, A. Surdo4, A. Tykhonov1, S. Vitillo1, H. Wang6, M. Weber1, D. Wu6, X. Wu1, F. Zhang6

A four-dimensional photon detector for PET application

We analyzed a photon detector for positron emission tomography with high spatial resolution and depth of interaction capability. The detector is composed of a monolithic LYSO scintillator crystal coupled on top and bottom sides to two custom SiPM arrays. We investigated the ability to reconstruct the DOI of the 511 keV photon comparing the number of triggered SiPMs on the two sides of the module. Acquisitions were performed scanning the lateral surface of the crystal with a collimated 511 keV photon beam at different incident positions. A standard deviation of 1.5 mm in depth of interaction was obtained at the center of the module.

Development of a 16-channel matrix of photodetection sensors for medical imaging and astrophysical applications

Recen% developed near W-photosensors are currently adopted in those applications where high sensitivity and good imaging capabilities are required, especially in fields such as astroparticle physics and medical imaging. An example of such applications is the camera of the Schwarzschild Couder Medium Size Telescope prototype (pSCT) which is in construction within the Cherenkov Telescope Array experiment. The camera consists of 177 photo-detection modules grouped into sectors of 25 modules, each based on matrixes of 64 6mm × 6mm pixels of SiUcon PhotomultipUers (SiPMs). Sensors produced by the Fondazione Bruno Kessler (FBK) in Italy are currently under investigation. Here we present a complete characterization of these highly sensitive near UV sensors, the assembly procedure and metrology results on several focal plane elements.

Towards the development of a SiPM-based module for the camera of the Schwarzschild-Couder Telescope prototype of the Cherenkov Telescope Array

The Italian Institute of Nuclear Physics is currently involved in the development of a prototype for a camera based on Silicon Photomultipliers (SiPMs) for the Cherenkov Telescope Array (CTA), a new generation of telescopes for ground{based gamma{ray astronomy. In recent years, SiPMs have proven to be highly suitable devices for applications where high sensitivity to low{intensity light and fast responses are required. Among their many advantages are their low operational voltage when compared with classical photomultiplier tubes, mechanical robustness, and increased photo{detection efficiency (PDE). Moreover, due to the possibility of operating them during bright moonlight, SiPMs can therefore considerably increase telescope duty cycle. Here we present a full characterization of a particular type of SiPM produced in Italy by the Fondazione Bruno Kessler, which is suitable for Cherenkov light detection in the Near-Ultraviolet (NUV). This device is a High{Density (HD) NUV SiPM, based on a micro cell of 40 μm × 40 μm and with an area of 6×6 mm2, providing low levels of dark noise and high PDE peaking in the NUV band. NUV-HD SiPMs will be arranged in a matrix of 8×8 single units to become part of the focal plane of the Schwarzschild-Couder Telescope prototype for CTA. An update on recent tests of the front-end electronics based on signal sampling with the TARGET-7 chip will be given as well.

Depth of interaction determination in monolithic scintillator with double side SiPM readout

BackgroundMonolithic scintillators read out by arrays of photodetectors represent a promising solution to obtain high spatial resolution and the depth of interaction (DOI) of the annihilation photon. We have recently investigated a detector geometry composed of a monolithic scintillator readout on two sides by silicon photomultiplier (SiPM) arrays, and we have proposed two parameters for the DOI determination: the difference in the number of triggered SiPMs on the two sides of the detector and the difference in the maximum collected signal on a single SiPM on each side. This work is focused on the DOI calibration and on the determination of the capability of our detector. For the DOI calibration, we studied a method which can be implemented also in detectors mounted in a full PET scanner. We used a PET detector module composed of a monolithic 20u2009×u200920u2009×u200910xa0mm3 LYSO scintillator crystal coupled on two opposite faces to two arrays of SiPMs. On each side, the scintillator was coupled to 6u2009×u20096 SiPMs. In this paper, the two parameters previously proposed for the DOI determination were calibrated with two different methods. The first used a lateral scan of the detector with a collimated 511xa0keV pencil beam at steps of 0.5xa0mm to study the detector DOI capability, while the second used the background radiation of the 176Lu in the scintillator. The DOI determination capability was tested on different regions of the detector using each parameter and the combination of the two.ResultsWith both parameters for the DOI determination, in the lateral scan, the bias between the mean reconstructed DOI and the real beam position was lower than 0.3xa0mm, and the DOI distribution had a standard deviation of about 1.5xa0mm. When using the calibration with the radioactivity of the LYSO, the mean bias increased of about 0.2xa0mm but with no degradation of the standard deviation of the DOI distribution.ConclusionsThe two parameters allow to achieve a DOI resolution comparable with the state of the art, giving a continuous information about the three-dimensional interaction position of the scintillation. These results were obtained by using simple estimators and a detector scalable to a whole PET system. The DOI calibration obtained using lutetium natural radioactivity gives results comparable to the other standard method but appears more readily applicable to detectors mounted in a full PET scanner.