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Positronium signature in organic liquid scintillators for neutrino experiments  [PDF]
D. Franco,G. Consolati,D. Trezzi
Physics , 2010, DOI: 10.1103/PhysRevC.83.015504
Abstract: Electron anti-neutrinos are commonly detected in liquid scintillator experiments via inverse beta decay, by looking at the coincidence between the reaction products, neutron and positron. Prior to positron annihilation, an electron-positron pair may form an orthopositronium (o-Ps) state, with a mean life of a few ns. Even if the o-Ps decay is speeded up by spin flip or pick off effects, it may introduce distortions in the photon emission time distribution, crucial for position reconstruction and pulse shape discrimination algorithms in anti-neutrino experiments. Reversing the problem, the o-Ps induced time distortion represents a new signature for tagging anti-neutrinos in liquid scintillator. In this paper, we report the results of measurements of the o-Ps formation probability and lifetime, for the most used solvents for organic liquid scintillators in neutrino physics (pseudocumene, linear alkyl benzene, phenylxylylethane, and dodecane). We characterize also a mixture of pseudocumene +1.5 g/l of 2,5-diphenyloxazole, a fluor acting as wavelength shifter. In the second part of the paper, we demonstrate that the o-Ps induced distortion of the scintillation photon emission time distributions represent an optimal signature for tagging positrons on an event by event basis, potentially enhancing the anti-neutrino detection.
Measurement of ortho-Positronium Properties in Liquid Scintillators  [PDF]
S. Perasso,G. Consolati,D. Franco,S. Hans,C. Jollet,A. Meregaglia,A. Tonazzo,M. Yeh
Physics , 2013, DOI: 10.1088/1748-0221/9/03/C03028
Abstract: Pulse shape discrimination in liquid scintillator detectors is a well-established technique for the discrimination of heavy particles from light particles. Nonetheless, it is not efficient in the separation of electrons and positrons, as they give rise to indistinguishable scintillator responses. This inefficiency can be overtaken through the exploitation of the formation of ortho-Positronium (o-Ps), which alters the time profile of light pulses induced by positrons. We characterized the o-Ps properties in the most commonly used liquid scintillators, i.e. PC, PXE, LAB, OIL and PC + PPO. In addition, we studied the effects of scintillator doping on the o-Ps properties for dopants currently used in neutrino experiments, Gd and Nd. Further measurements for Li-loaded and Tl-loaded liquid scintillators are foreseen. We found that the o-Ps properties are suitable for enhancing the electron-positron discrimination.
Characterization of positronium properties in doped liquid scintillators  [PDF]
G. Consolati,D. Franco,S. Hans,C. Jollet,A. Meregaglia,S. Perasso,A. Tonazzo,M. Yeh
Physics , 2013, DOI: 10.1103/PhysRevC.88.065502
Abstract: Ortho-positronium (o-Ps) formation and decay can replace the annihilation process, when positron interacts in liquid scintillator media. The delay induced by the positronium decay represents either a potential signature for anti-neutrino detection, via inverse beta decay, or to identify and suppress positron background, as recently demonstrated by the Borexino experiment. The formation probability and decay time of o-Ps depend strongly on the surrounding material. In this paper, we characterize the o-Ps properties in liquid scintillators as function of concentrations of gadolinium, lithium, neodymium, and tellurium, dopers used by present and future neutrino experiments. In particular, gadolinium and lithium are high neutron cross section isotopes, widely used in reactor anti-neutrino experiments, while neodymium and tellurium are double beta decay emitters, employed to investigates the Majorana neutrino nature. Future neutrino experiments may profit from the performed measurements to tune the preparation of the scintillator in order to maximize the o-Ps signature, and therefore the discrimination power.
Plastic scintillators for positron emission tomography obtained by the bulk polymerization method  [PDF]
?ukasz Kap?on,Andrzej Kochanowski,Marcin Molenda,Pawe? Moskal,Anna Wieczorek,Tomasz Bednarski,Piotr Bia?as,Eryk Czerwiński,Grzegorz Korcyl,Jakub Kowal,Pawe? Kowalski,Tomasz Kozik,Wojciech Krzemień,Szymon Nied?wiecki,Marek Pa?ka,Monika Pawlik,Lech Raczyński,Zbigniew Rudy,Piotr Salabura,Neha Gupta-Sharma,Micha? Silarski,Artur S?omski,Jerzy Smyrski,Adam Strzelecki,Wojciech Wi?licki,Marcin Zieliński,Natalia Zoń
Physics , 2015, DOI: 10.1515/bams-2013-0108
Abstract: This paper describes three methods regarding the production of plastic scintillators. One method appears to be suitable for the manufacturing of plastic scintillator, revealing properties which fulfill the requirements of novel positron emission tomography scanners based on plastic scintillators. The key parameters of the manufacturing process are determined and discussed.
A mobile antineutrino detector with plastic scintillators  [PDF]
Yasuhiro Kuroda,Shugo Oguri,Yo Kato,Ryoko Nakata,Yoshizumi Inoue,Chikara Ito,Makoto Minowa
Physics , 2012, DOI: 10.1016/j.nima.2012.06.040
Abstract: We propose a new type segmented antineutrino detector made of plastic scintillators for the nuclear safeguard application. A small prototype was built and tested to measure background events. A satisfactory unmanned field operation of the detector system was demonstrated. Besides, a detailed Monte Carlo simulation code was developed to estimate the antineutrino detection efficiency of the detector.
Application of Compressive Sensing Theory for the Reconstruction of Signals in Plastic Scintillators  [PDF]
L. Raczyński,P. Kowalski,T. Bednarski,P. Bia?as,E. Czerwiński,?. Kap?on,A. Kochanowski,G. Korcyl,J. Kowal,T. Kozik,W. Krzemień,M. Molenda,P. Moskal,Sz. Nied?wiecki,M. Pa?ka,M. Pawlik,Z. Rudy,P. Salabura,N. G. Sharma,M. Silarski,A. S?omski,J. Smyrski,A. Strzelecki,W. Wi?licki,M. Zieliński
Physics , 2013, DOI: 10.5506/APhysPolBSupp.6.1121
Abstract: Compressive Sensing theory says that it is possible to reconstruct a measured signal if an enough sparse representation of this signal exists in comparison to the number of random measurements. This theory was applied to reconstruct signals from measurements of plastic scintillators. Sparse representation of obtained signals was found using SVD transform.
Application of WLS strips for position determination in Strip PET tomograph based on plastic scintillators  [PDF]
J. Smyrski,P. Moskal,T. Bednarski,P. Bia?as,E. Czerwiński,?. Kap?on,A. Kochanowski,G. Korcyl,J. Kowal,P. Kowalski,T. Kozik,W. Krzemień,M. Molenda,Sz. Nied?wiecki,M. Pa?ka,M. Pawlik,L. Raczyński,Z. Rudy,P. Salabura,N. G. Sharma,M. Silarski,A. S?omski,A. Strzelecki,W. Wi?licki,M. Zieliński,N. Zoń
Physics , 2013, DOI: 10.1515/bams-2013-0103
Abstract: A method of determination of a gamma quantum absorption point in a plastic scintillator block using a matrix of wavelength-shifting (WLS) strips is proposed. Application of this method for improvement of position resolution in newly proposed PET detectors based on plastic scintillators is presented. The method enables to reduce parallax errors in reconstruction of images which occurs in the presently used Positron Emission Tomography scanners.
Neutrino Flavor Tagging in a Four-Neutrino Mixing and Oscillation Model  [PDF]
E. M. Lipmanov
Physics , 1999,
Abstract: A neutrino mass dominance quantity is introduced for tagging the neutrino flavor in the phenomenological two-parameter four neutrino mixing matrix with two neutrino mass doublets and thorough maximal neutrino doublet mixing. While there is no hierarchy of the neutrino masses in the neutrino flavor eigenstates of this model, it may rather be a special hierarchy of the mass dominance ratios in these eigenstates. A neutrino flavor hierarchy condition is suggested: a direct link between the neutrino flavor and the flavor of the charged leptons which interconnects the two mixing angles, theta and phi, via the charged lepton mass ratios, with the net result tg^2 phi = (tg^2 theta)^gamma, gamma ~ 2.06. It leads to distinct inferences testable at SNO and Super-K.
Test of a single module of the J-PET scanner based on plastic scintillators  [PDF]
P. Moskal,Sz. Nied?wiecki,T. Bednarski,E. Czerwiński,?. Kap?on,E. Kubicz,I. Moskal,M. Pawlik-Nied?wiecka,N. G. Sharma,M. Silarski,M. Zieliński,N. Zoń,P. Bia?as,A. Gajos,A. Kochanowski,G. Korcyl,J. Kowal,P. Kowalski,T. Kozik,W. Krzemień,M. Molenda,M. Pa?ka,L. Raczyński,Z. Rudy,P. Salabura,A. S?omski,J. Smyrski,A. Strzelecki,A. Wieczorek,W. Wi?licki
Physics , 2014, DOI: 10.1016/j.nima.2014.07.052
Abstract: 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 article we report on tests of a single detection module built out from BC-420 plastic scintillator strip (with dimensions of 5x19x300mm^3) read out at two ends by Hamamatsu R5320 photomultipliers. The measurements were performed using collimated beam of annihilation quanta from the 68Ge isotope and applying the Serial Data Analyzer (Lecroy SDA6000A) which enabled sampling of signals with 50ps intervals. The time resolution of the prototype module was established to be better than 80ps (sigma) for a single level discrimination. The spatial resolution of the determination of the hit position along the strip was determined to be about 0.93cm (sigma) for the annihilation quanta. The fractional energy resolution for the energy E deposited by the annihilation quanta via the Compton scattering amounts to sigma(E)/E = 0.044/sqrt(E[MeV]) and corresponds to the sigma(E)/E of 7.5% at the Compton edge.
Novel method for hit-position reconstruction using voltage signals in plastic scintillators and its application to Positron Emission Tomography  [PDF]
L. Raczynski,P. Moskal,P. Kowalski,W. Wislicki,T. Bednarski,P. Bialas,E. Czerwinski,L . Kaplon,A. Kochanowski,G. Korcyl,J. Kowal,T. Kozik,W. Krzemien,E. Kubicz,M. Molenda,I. Moskal,Sz. Niedzwiecki,M. Palka,M. Pawlik-Niedzwiecka,Z. Rudy,P. Salabura,N. G. Sharma,M. Silarski,A. Slomski,J. Smyrski,A. Strzelecki,A. Wieczorek,M. Zielinski,N. Zon
Physics , 2014, DOI: 10.1016/j.nima.2014.07.032
Abstract: 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
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