Marcin Molenda

Test of a single module of the J-PET scanner based on plastic scintillators

A Time of Flight Positron Emission Tomography scanner based on plastic scintillators is being developed at the Jagiellonian University by the J-PET collaboration. The main challenge of the conducted research lies in the elaboration of a method allowing application of plastic scintillators for the detection of low energy gamma quanta. In this paper we report on tests of a single detection module built out from the BC-420 plastic scintillator strip (with dimensions of 5 � 19 � 300 mm 3 ) read out at two ends by Hamamatsu R5320 photomultipliers. The measurements were performed using collimated beam of annihilation quanta from the 68 Ge isotope and applying the Serial Data Analyzer (Lecroy SDA6000A) which enabled sampling of signals with 50 ps intervals. The time resolution of the prototype module was established to be better than 80 ps (σ) for a single level discrimination. The spatial resolution of the determination of the hit position along the strip was determined to be about 0.93 cm (σ) for the annihilation quanta. The fractional energy resolution for the energy E deposited by the annihilation quanta via the Compton scattering amounts to σðEÞ=E � 0:044= ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi EðMeVÞ p

Novel method for hit-position reconstruction using voltage signals in plastic scintillators and its application to Positron Emission Tomography

Currently inorganic scintillator detectors are used in all commercial Time of Flight Positron Emission Tomograph (TOF-PET) devices. The J-PET collaboration investigates a possibility of construction of a PET scanner from plastic scintillators which would allow for single bed imaging of the whole human body. This paper describes a novel method of hit-position reconstruction based on sampled signals and an example of an application of the method for a single module with a 30 cm long plastic strip, read out on both ends by Hamamatsu R4998 photomultipliers. The sampling scheme to generate a vector with samples of a PET event waveform with respect to four user-defined amplitudes is introduced. The experimental setup provides irradiation of a chosen position in the plastic scintillator strip with an annihilation gamma quanta of energy 511 keV. The statistical test for a multivariate normal (MVN) distribution of measured vectors at a given position is developed, and it is shown that signals sampled at four thresholds in a voltage domain are approximately normally distributed variables. With the presented method of a vector analysis made out of waveform samples acquired with four thresholds, we obtain a spatial resolution of about 1 cm and a timing resolution of about 80 ps ( σ).

Synthesis, thermal and electrical properties of Li1+δMn2−δO4 prepared by a sol–gel method

Abstract The Li 1+ δ Mn 2− δ O 4 samples (0.00≤ δ ≤0.20) were obtained by a sol–gel method and characterized using: chemical analyses, XRD, SEM, TGA, DSC, electric conductivity and thermoelectric power. The obtained results were discussed in relation to the calcination temperature, and to the results obtained on commercial LiMn 2 O 4 . The samples calcined at 300 °C (S-samples) consisting small excess of Li ( δ ≤0.04) showed no phase transition at 285 K and no disturbance in electric conductivity and thermoelectric power, as observed for the related samples calcined at 800 °C (H-samples). Partial thermal decomposition of the S-samples or oxygen uptake by the H-samples were observed during TGA experiments above 350 °C. The beginning of the thermal decomposition of the H-samples started at higher temperatures, depending on Li-contents. At about 920 °C, the rapid acceleration took place independently on type of the samples. The thermal decomposition up to 800 °C seems to be reversible, owing to the samples reoxidation.

A novel method based solely on field programmable gate array (FPGA) units enabling measurement of time and charge of analog signals in positron emission tomography (PET)

Abstract This article presents an application of a novel technique for precise measurements of time and charge based solely on a field programmable gate array (FPGA) device for positron emission tomography (PET). The described approach simplifies electronic circuits, reduces the power consumption, lowers costs, merges front-end electronics with digital electronics, and also makes more compact final design. Furthermore, it allows to measure time when analog signals cross a reference voltage at different threshold levels with a very high precision of ~15 ps (rms) and thus enables sampling of signals in a voltage domain.

Electronic structure and reactivity of Li1−xMn2O4 cathode

Abstract The investigations of low temperature electrical and structural properties of the Li 1− x Mn 2 O 4 cathode as a function of lithium concentration are presented. Structure studies of deintercalated spinel revealed the existence of a broad (300–200 K) phase transition from cubic into orthorhombic phase also confirmed by DSC results. Thermoelectric power and electrical conductivity measurements indicate that the manganese spinel undergoes a modification of electronic structure during intercalation process.

Electrochemical and chemical deintercalation of LiMn2O4

Abstract This work presents results of measurements of electrical conductivity, thermoelectric power and thermal properties of manganese spinel samples deintercalated in two different ways—an electrochemical and chemical one. It was shown that different methods of lithium extraction lead to striking differences in electrical properties of the obtained Li x Mn 2 O 4 samples what agrees with the observed differences in their structure as seen by XRD.

A pilot study of the novel J-PET plastic scintillator with 2-(4-styrylphenyl)benzoxazole as a wavelength shifter

For the rst time a molecule of 2-(4-styrylphenyl)benzoxazole containing benzoxazole and stilbene groups is applied as a scintillator dopant acting as a wavelength shifter. In this article a light yield of the plastic scintillator, prepared from styrene doped with 2 wt% of 2,5-diphenylbenzoxazole and 0.03 wt% of 2-(4-styrylphenyl)benzoxazole, is determined to be as large as 60% 2% of the anthracene light output. There is a potential to improve this value in the future by the optimization of the additives concentrations.

SYNTHESIS AND PROPERTIES OF Li2MnSiO4 COMPOSITE CATHODE MATERIAL FOR SAFE Li-ION BATTERIES

Lithium silicates Li2MnSiO4 (where M is a 3d metal) with their theoretical capacity up to 333 mAh⋅g-1 and high chemical stability, thanks to a presence of strong covalent bonds Si–O, seem to be a good potential cathode material for Li-ion batteries. The main drawback of those materials is their low electric conductivity which can be enhanced by coating the material with conductive carbon layer (CCL). This work concerns the synthesis of CCL/Li2MnSiO4 composite material and investigation of its physicochemical properties. The material was successfully produced using sol-gel Pechini method. In order to find the best way of receiving Li2MnSiO4 product various synthesis conditions were applied. CCL/Li2MnSiO4 composite was produced in a one-step process using organic precursor matrix as a source of carbon. Both Li2MnSiO4 material and CCL/Li2MnSiO4 composite were investigated using thermal analysis (EGA-TGA/DTG/SDTA), X-ray diffraction (XRD) and electrical conductivity measurements to find the relations between structure, morphology and electrochemical properties.

Facile synthesis of C/Sn nanocomposite anode material for Li ion batteries

Abstract C/Sn nanocomposites were prepared in simultaneous pyrolysis and carboreduction process (700 and 800°C) of a nanometric tin oxide(IV), obtained by a modified reverse microemulsion method. The proposed method provided formation of tin nanograins encapsulated in conductive carbon layers. The obtained materials with different carbon loadings (13–26 wt-%) were characterised by X-ray diffraction (XRD), low temperature nitrogen adsorption method (N2-BET) and transmission electron microscopy. Galvanostatic discharge/charge tests, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) as well as electrical conductivity studies were used to characterise electrochemical properties of C/Sn nanocomposites. It was found that the electrochemical performance of C/Sn nanocomposites may be affected by carbon matrix morphology.

Trigger-less and reconfigurable data acquisition system for positron emission tomography

Abstract This article is focused on data acquisition system (DAQ) designed especially to be used in positron emission tomography (PET) or single-photon emission computed tomography. The system allows for continuous registration of analog signals during measurement. It has been designed to optimize registration and processing of the information carried by signals from the detector system in PET scanner. The processing does not require any rejection of data with a trigger system. The proposed system possesses also an ability to implement various data analysis algorithms that can be performed in real time during data collection.