Read-out electronics for digital silicon photomultiplier modules

A new kind of a PET-Scanner (PET = positron emission tomography) for plant research is developed asa joint project of the Forschungszentrum Jülich and Philips Digital Photon Counting (PDPC). Thisscanner will utilize digital silicon photomultiplier (dSiPM) for plant phenotyping for the very first time.The goal of this work is to get a further knowledge of the operation of digital silicon photomultiplier.On this account a test-facility for this new photo detectors has been installed at the central instituteof engineering, electronics and analytics (ZEA-2 electronic systems) to determine the usage of thissensors, having regard to use them as scintillation detectors in a PET-Scanner later on.This work has its focus on the development of a fast read-out electronic for the used photo sensorsDPC3200-22-44. As there will be high data rates a fast USB 3.0 interface has been used. All thenecessary processing and data handling has been implemented in a state of the art FPGA

phenoPET: A dedicated PET Scanner for Plant Research based on digital SiPMs

In the frame of the German Plant Phenotyping Project (DPPN) we developed a novel PET scanner. In contrary to a clinical or preclinical PET scanner the detector rings of the Plant System are oriented in a horizontal plane. The final system will be equipped with three rings covering a Field of View (FOV) of 18 cm diameter and 20 cm axial height. One detector ring is formed by 12 modules. Each module contains four 8×8 pixel digital SiPM devices DPC-3200-22-44 (Philips Digital Photon Counting) connected to a PCB and four scintillator matrices with 16×16 individual LYSO scintillators. Crystal size is 1.85×1.85×10 mm3. The matrices are composed with both reflective and transparent contact faces between the crystals in order to optimize crystal identification. A cooling system keeps the detectors below 5°C and limits the dark count rate. Data are already preprocessed by the Cyclone FPGA (Altera) in the module and transmitted from there at 50MiB/s to the base board. The base board collects the data from all modules and allows coincidence detection performed on a Kintex-7 FPGA (Xilinx). Finally the data link to the computer system for image reconstruction is realized via an USB 3.0 connection. Due to the fast photodetectors the system is dedicated to work with rather high activities. Preliminary measurements showed a coincidence peak of 250 ps FWHM between two detector elements and an energy resolution ΔE/E = 12%. This paper will present first results from a one ring system with a FOV of 18 cm diameter and 6.5 cm axial height

Development of a solid-state position sensitive neutron detector prototype based on 6Li-glass scintillator and digital SiPM arrays

Photomultiplier tubes (PMT) have been used extensively as the photodetector of choice in scintillation baseddetectors for cold and thermal neutrons. However, the limitations of PMT based scintillation neutron detectorssuch as their sensitivity to magnetic fields or their high operating voltages (> 1 kV) have triggered the search foralternative photodetectors for these applications. Silicon photomultipliers (SiPM) operate in the single photonregime, have lower operating voltages (∼20–70 V) than PMTs and are insusceptible to magnetic field. Additionalfeatures of the SiPMs like their low production cost, compactness and higher readout rates make them apotential candidate to replace the photodetector part in these developments. Therefore, we are developing ascintillation neutron detector based on SiPM technology. The detector prototype with an active detection area of13 cm × 13 cm is aimed to be used in the future at the TREFF instrument of the Heinz Maier-Leibnitz Zentrum (MLZ)in Garching, Germany, for neutron reflectometry experiments. In this paper, we report the detector concept, itsdevelopment and the simulation results for design optimization

Properties of Ultra High Performance Concrete (UHPC) in tension at high strain rates

This paper is a contribution to the material description of Ultra High Performance Concrete (UHPC) at high-speed dynamic loading conditions. Based on a series of Hopkinson-Bar experiments, dynamical material parameters such as the Tensile Strength, Young's Modulus and Fracture Energy are determined at high strain rates of 102 s-1. A comparison with the results of these parameters for normal and high strength concretes leads to a qualitative and quantitative description of UHPC at high strain rates. Differences in macroscopic strain-rate-effects occur due to a significantly reduced amount of the moisture effect (reduced capillary pores) on the one side and a different relation of aggregate to grout strength for UHPC on the other side (section 1). Based on the experimentally determined Fracture Energy and Stress-Crack-Opening- Relation a material model for UHPC at high strain-rates is postulated by extending the established RHT concrete damage model with a new fracture me chanical damage law (section 2). Numerical hydrocode simulations of the Hopkinson-Bar Experiments are presented to proof the evidence of the concrete model for a one-dimensional wave propagation problem. Furthermore a series of impact experiments on rebar reinforced UHPC plates with more complex three-dimensional wave propagation show a satisfying accuracy of the new fracture mechanic concrete model even for more complex failure mechanisms from cracking of the concrete to perforation of aircraft engine missiles at high strain rates (section 3)

Fiber-reinforced ultra-high performance concrete under tensile loads

The present paper deals with the material behavior of ultra-high performance concrete (UHPC) at high strain rates up to 160 1/s. Static and dynamic material-parameters and the fracture behavior of a fiber-reinforced ultra-high performance concrete (mixture B4Q) were investigated. The material shows static compression strength up to 180 MPa and static tension strength up to 9 MPa. With the help of Hopkinson Bar experiments, dynamic material-properties like Young's modulus, tensile strength and fracture energy are determined. Furthermore, it was possible to record the failure process in small time-steps by application of a new method of fracture observation. Based on the measured material-parameters, the paper provides "Dynamic Increase Factors" (DIF) of Young's modulus, tensile strength and fracture energy to figure out the differences between UHPC, conventional and high strength concrete and the potential of the new building material

Development and characterization of a 4 × 4mm 2 pixel neutron scintillation detector using digital SiPMs

This work describes the development of the first demonstrator device for neutron detection based on a 6Li-glass as a scintillator and silicon photomultipliers (SiPM) as photodetector. For the first characterization, the scintillator was pixelated with a one to one correspondence between scintillator and SiPM pixels, and optical cross-talk between pixels was minimized. Measurements in a high luminosity neutron beam show the functionality of the device and allow for partial characterization. The position resolution is 4 × 4mm2 and the detection efficiency of neutrons is 91(6)% relative to the active area. The device is linear up to at least 600 kcps

PET Scintillator Arrangement on digital SiPMs

The common way to build a PET detector is to place an array of scintillator elements on top of a photo detector. In order to achieve high spatial resolution the scintillator footprints are often smaller than the pixel size of the photodetector. This requires light sharing and some kind of algorithm like Anger-Logic in order to identify the correct scintillator element in which the event took place. The digital Silicon Photomultiplier DPC3200-22-44 (Philips Digital Photon Counting) is a fully digital photo sensor device [1]. Each pixel consists of 3200 individual micro cells which are charged and read out under digital control. The device (Tile) is organized as an array of 8 by 8 pixels each of 3.9x3.9 mm2 size and is realized as a PCB equipped with 16 dice. One die provides four pixels together with the corresponding triggering, validation and readout electronics. Depending on the configuration the detection of an event on one die can cause the other dice to transmit their data as well (neighbor logic). The obvious solution of using neighbor logic and a scintillator matrix with light guide covering the whole tile shows some drawbacks. After each event all 16 dice will be busy and all pixels need to be read out. This results in increased dead time and a lot of data. Furthermore it turned out that sometimes pixels are missing because dice were already busy and could not transmit data when the event was detected. This will complicate the identification of the event position. A better performance can be obtained when the light is shared only within the four pixels of each die and the dice work independent from each other. We investigated the positioning capability of different scintillator matrices and light guides. These are arranged in such a way, that a single die can only receive the light from a 4 by 4 array of LYSO crystals which covers exactly the die dimensions. The results show that clear crystal identification can be achieved with such an arrangement. [1] Haemisch et al., Physics Procedia 37 (2012) 154