G. Kalinka

The first candidate for chiral nuclei in the A~80 mass region: 80Br

Abstract Excited states of 80Br have been investigated via the 76Ge(11B, α 3 n ) and 76Ge(7Li, 3n) reactions and a new Δ I = 1 band has been identified which resides ∼ 400 keV above the yrast band. Based on the experimental results and their comparison with the triaxial particle rotor model calculated ones, a chiral character of the two bands within the π g 9 / 2 ⊗ ν g 9 / 2 configuration is proposed, which provides the first evidence for chirality in the A ∼ 80 region.

Development of an FPGA-based data acquisition module for small animal PET

We report on the design of a data acquisition (DAQ) module for a small animal PET camera developed at our institutes. During the design an important guideline was to develop a system which is built up from strictly identical DAQ modules, and which has no built-in hardware limitation on the maximum number of modules. The developed DAQ module comprises of an LSO scintillator crystal block, a position sensitive PMT, analog signal conditioning circuits, a digitizer, an field programmable gate array (FPGA) for digital signal processing, and a communication module through which the collected data are sent to a cluster of computers for postprocessing and storage. Instead of implementing hardware coincidence detection between the modules, we attach a precise time stamp to each event in our design, and the coincidence is determined by the data collecting computers during postprocessing. The digital CFD algorithm implemented in the FPGA gives a time resolution of 2 ns FWHM for real detector signals

Development of an FPGA-Based Data Acquisition Module for Small Animal PET

We report on the design of a DAQ module for a small animal PET camera developed at our institutes. During the design an important guideline was to develop a system which is built up from strictly identical DAQ modules, and which has no built-in hardware limitation on the maximum number of modules. The developed DAQ module comprises of an LSO scintillator crystal block, a position sensitive PMT, analog signal conditioning circuits, a digitizer, an FPGA for digital signal processing and a communication module through which the collected data is sent to a cluster of computers for post processing and storage. Instead of implementing hardware coincidence detection between the modules we attach a precise time-stamp to each event in our design, and the coincidence is determined by the data collecting computers during the post processing. The digital CFD algorithm implemented in the FPGA gives a time resolution of 2 to 3 ns FWHM for real detector signals

Ethernet based distributed data acquisition system for a small animal PET

We report on the design of a small animal PET scanner being developed at our institutes. The existing setup is the first version of the miniPET machine consisting of four detector modules. Each detector module consists of an 8times8 LSO scintillator crystal block, a position sensitive photomultiplier, a digitizer including a digital signal processing board and an Ethernet interface board. There is no hardware coincidence detection implemented in the system and coincidence is determined based on a time stamp attached to every event by a digital CFD algorithm. The algorithm is implemented in the digital signal processing board and generates a time stamp with a coincidence resolution of less than 2 ns. The data acquisition system is based on Ethernet network and is highly scalable in size and performance

Deterioration of Electrical and Spectroscopic Properties of a Detector Grade Silicon Photodiode Exposed to Short Range Proton, Lithium and Oxygen Ion Irradiation

The electrical properties and spectral response of a Hamamatsu S5821 silicon PIN photodiode were investigated in-situ during and after irradiation by 430 keV H⁺, 2.15 MeV Li²⁺, 4 MeV O³⁺ and 6.5 MeV O⁴⁺ ion beams focused to a sub-micrometer beam size. Ion species and their respective energies were selected to approximately have the same end range of 5 mum within the depletion region of the unbiased photodiode. Particle irradiation fluences (Phi) of 10⁸ to 10¹² cm^-2 were selected, such that displacement damage dose (D_d) values within the material had a similar range of 10¹⁰ to 10 ³ MeV/g for the selected particles. Under these conditions, it has been observed that protons produce the largest increase in device capacitance. At 100 V an increase in the generation current from 2.3 nA/cm² for a unirradiated sample to 1.7 muA/cm², 2.4 muA/cm², and 3 muA/cm² for samples irradiated by protons, lithium, and oxygen ions, respectively, was determined for a displacement damage dose of 3.9 times 10¹¹ MeV/g. The ion beam-induced charge (IBIC) technique was used to investigate the charge collection efficiency (CCE) of the irradiated photodiodes. The irradiation-induced changes of the CCE for both protons and oxygen were compared with respect to the non-ionizing energy loss (NIEL), which is a good measure of displacement damage introduced into a material by ionizing particles. The measured reduction of the pulse height with increasing displacement damage dose was fitted to a radiation damage function. The calculated equivalent damage factors, <i>K</i> _ed, for the proton probe on proton damaged silicon (3.6 plusmn0.4) times 10^-15 g/MeV, the proton probe on oxygen damaged silicon (3.90 plusmn0.07) times 10^-15 g/MeV , and the oxygen probe on oxygen damaged silicon (3.65 plusmn0.03) times 10^-14 g/MeV have been obtained.

Particle discriminator for the identification of light charged particles with CsI(Tl) scintillator + PIN photodiode detector

Abstract A particle discriminator exploiting the ballistic deficit effect for pulse shape discrimination has been developed for CsI(Tl) scintillator + PIN photodiode charged-particle detectors. The method is theoretically investigated and it is shown that the figure of merit of the particle separation is mainly governed by the absolute value of the differential quotient of the rise time dependent ballistic deficit. As the actual particle discriminator contains shaping amplifiers, baseline restorer, pile-up rejector and analog-to-digital converters, it directly accepts signals from a charge-sensitive preamplifier, and its outputs deliver the type and the energy of the particles in the form of eight-bit digital codes. The performance of the particle discriminator is characterised by the figure-of-merit measured as a function of the particle energy.

Development of an Improved Detector Module for miniPET-II

We present a new detector module developed for miniPET-II, the second generation of the miniPET small animal PET scanners. The improved module features new hardware components for better performance: LySO crystal material, increased number of crystal segments, Hamamatsu H9500 PSPMT, Xilinx Virtex-4 FPGA and Gigabit Ethernet. However, the principle of operation is the same: no hardware coincidence detection is implemented, data is acquired in list mode and transfered over an Ethernet network. The resulting new module is more suitable for full ring configurations.

Ethernet Based Distributed Data Acquisition System for a Small Animal PET

We report on the design of a small animal PET scanner being developed at our institutes. The existing setup is the first version of the miniPET machine consisting of four detector modules. Each detector module consists of an 8times8 LSO scintillator crystal block, a position sensitive photomultiplier, a digitizer including a digital signal processing board and an Ethernet interface board. There is no hardware coincidence detection implemented in the system and coincidence is determined based on a time stamp attached to every event by a digital CFD algorithm. The algorithm is implemented in the digital signal processing board and generates a time stamp with a coincidence resolution of less than 2 ns. The data acquisition system is based on Ethernet network and is highly scalable in size and performance

Realization of charge sensitive preamplifiers using current feedback operational amplifier

Abstract A simple charge sensitive preamplifier circuit has been designed, which uses a CFOPA. Despite its simplicity the preamplifier exhibits good noise and speed parameters.

Entrance window structure of a Si (Li) detector

Abstract The response function of a Si (Li) detector with a 45 μm thick decompensated front p-Si layer, in order to enhance window effects, has been measured in the 1.2–6 keV X-ray energy region as a function of the so-called photo dead layer thickness in the 14-0.4 μm range by varying the detector bias between 200 and 1000 V. From measured spectrum component (photopeak, tail, shelf, escape and SiK line) intensity data, discrete regions responsible for particular spectrum components have been identified: (i) the Au surface barrier, in addition to characteristic X-rays, contributes only to the shelf, adjacent to it is located (ii) an “absolute” Si dead layer, which exists only in the undepleted p-region case, and produces no events except for the internal SiK fluorescence, followed by (iii) an incomplete charge collection region, divided into shelf and tail subrogions, beyond which (iv) there is the detector sensitive volume with complete charge collection, resulting in photo- and escape peaks, and a bulk shelf component as well. A model has also been developed for the explanation of the observed dead layer thickness dependence of escape- and SiK line intensity.