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1
Content available remote

Can Tao-Eldrup Model Be Used at Short o-Ps Lifetime?

100%
Zgardzińska B.
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|
vol. 125
|
issue 3
700-701
EN
The distortion of estimated void radii introduced by assumption of an infinite potential depth in the Tao-Eldrup model is discussed. If the deviation by 10% is still acceptable, the range of ortho-Ps lifetimes at which the model gives correct radii is from 1.8 to 6.2 ns.
2
Content available remote

Investigation of PCM Microcapsules with Paraffin Filling by Positron Lifetime Spectroscopy

100%
Zgardzińska B.
Acta Physica Polonica A
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2015
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vol. 127
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issue 5
1536-1539
EN
Positron annihilation lifetime spectroscopy was applied to investigate the microcapsules composed of n-eicosane (filling material) and polysiloxane polymer (shell) in the range of temperatures 123-333 K. Pure components of microcapsules were also investigated as a base for interpretation of the measurement results. The temperature of phase transitions in microcapsules was determined. It showed the appearance of a rotary phase, which is not present in pure n-eicosane. In the considered material, two types of free volume have been identified. The sizes of free volumes able to accommodate Ps were estimated using standard models. On the basis of the o-Ps intensities, the content of polysiloxane in microcapsules was estimated as about 40%. Internal structure of the microcapsules (morphology) was observed by scanning electron microscopy.
3
Content available remote

Ortho-Positronium in Alkanes under High Pressure

64%
Goworek T., Zgardzińska B.
Acta Physica Polonica A
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2008
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vol. 113
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issue 5
1379-1383
EN
Phase transitions in n-alkanes were observed by using the positron annihilation lifetime method. In the case of alkanes, application of pressure is equivalent to temperature lowering (1 K corresponds to ≈4 MPa). When argon at high pressure penetrates the sample one observes a non-monotonous dependence of the melting point on pressure. This effect is observed also in even-numbered alkanes, in which there is no rotator phase.
4
Content available remote

Positronium Formation with Trapped Electrons in n-Alkanes

64%
Zgardzińska B., Goworek T.
Acta Physica Polonica A
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2011
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vol. 119
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issue 3
328-331
EN
Positronium (Ps) formation during self-irradiation by positrons was observed in n-alkanes of various carbon chain length. The rise of Ps intensity with time of irradiation is the result of positronium formation with trapped excess electrons. In the range T < 190 K the saturation value of positronium intensity changes with temperature mainly due to the change of positron mobility. With the increase of the irradiation dose the process of charging traps is slowing down and this effect is ruled mainly by interaction of excess electrons with ionization products during electron's migration to the traps.
5
Content available remote

Positronium in Phase IV and Rotator Phase of Long-Chain Alkanes

64%
Zgardzińska B., Goworek T.
Acta Physica Polonica A
|
2008
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vol. 113
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issue 5
1551-1555
EN
Ortho-positronium lifetime and intensity was measured as a function of temperature and pressure for some n-alkanes in which so-called "phase IV" appears. This phase is characterized by slightly increased ortho-positronium lifetime compared to low-temperature phases. It was found that the effect of quenching positronium by light does not appear in all phases from phase IV upwards. The lifetime in the rotator phases becomes equal to that in liquids, and only the change of positronium formation intensity allows to detect the solid-liquid transition in positron lifetime measurements.
6
Content available remote

New Porosimetric Method Based on the 3γ Annihilation Rate. Applications to Materials Science and Medical Imaging

64%
Jasińska B., Zgardzińska B.
Acta Physica Polonica A
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2017
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vol. 132
|
issue 5
1616-1619
EN
A new parameter δ based on 3γ annihilation is proposed. It describes the porosity of the materials containing small intermolecular voids below 1 nm. It can be applied to material investigation to compare changes in the material porosity depending on temperature or pressure as well as to study of ageing or manufacturing processes. Particularly it is dedicated to prepare the new imaging method and can be used during positron emission tomography diagnosis allowing determination the kind or stage of pathogenic alteration.
7
Content available remote

Aerogel IC3120 Under High Pressure Exerted Mechanically and by Nitrogen

64%
Gorgol M., Zgardzińska B.
Acta Physica Polonica A
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2017
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vol. 132
|
issue 5
1531-1534
EN
Highly porous IC3120 silica aerogel was subjected to the high pressure up to 450 MPa while the positron annihilation lifetime spectra were collected. The pressure was delivered to the investigated samples in two ways: by pistons and by gas (nitrogen) penetrating the aerogel. The evolution of all PALS parameters was discussed. With the increase of the pressure, shortening of ortho-positronium lifetimes (different, depending on the pressure method introduced) was observed. Similarity between the dependence of the longest-lived o-Ps component lifetime on the pressure, for the sample affected with nitrogen molecules and pure nitrogen was observed. It suggests, that the nitrogen fills the largest free volumes of the aerogel. The pressure exerted mechanically causes much smaller decrease of free volume available for positronium. The comparison of PALS results with the electron microscopy images, obtained after removing the pressure, confirmed that more intense and lasting changes were caused by affecting the aerogel with the pistons.
8
Content available remote

Influence of Pressure on the Size of Free Volumes in Some Waxes

64%
Zgardzińska B., Gorgol M.
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|
vol. 125
|
issue 3
816-820
EN
Positron lifetime spectra were measured as a function of pressure for multicomponent mixtures of alkanes with an average carbon chain length of 19 atoms, and a varying width of length distribution. The range of rotator phase broadens with increasing the wax component distribution. When the number of wax components was five or more, we have observed the coexistence of rotator-rigid phases. The results of analysis of high statistics positron annihilation lifetime spectra by MELT program speaks in favour of an existence (in that range) of a single broad component, rather than two components corresponding to the separate rigid and rotator phases. In the mixtures of alkanes, the inter-lamellar gap size increases significantly due to the presence of various chain lengths of the components forming the mixture. For all investigated waxes the pressure of 360 MPa was sufficient to reduce the gap width to that one observed in pure alkanes.
9
Publication available in full text mode
Content available

Influence of Positron Irradiation on Positronium Formation in n-Alkanes

64%
Pietrow M., Zgardzińska B.
Acta Physica Polonica A
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2006
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vol. 110
|
issue 5
641-648
EN
Positronium formation probability was investigated as a function of irradiation time and temperature for some long-chain saturated hydrocarbons (alkanes). Intensity of ortho-positronium component in the lifetime spectrum depends on the concentration of trapped excess electrons, but also on concentration of radicals and ions acting as electron scavengers. The results indicate the existence of two kinds of electron traps; those which are not emptied by thermal treatment disappear after several days of positron irradiation.
10
Content available remote

A New Approach to the Presentation of the Positron Annihilation Lifetime Spectroscopy Results, n-Alkanes

64%
Zgardzińska B., Standzikowski K.
Acta Physica Polonica A
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2017
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vol. 132
|
issue 5
1496-1500
EN
The standard form of the positron annihilation lifetime spectroscopy results presentation are two plots of o-Ps lifetime and intensity as a function of external factor, e.g. temperature, pressure. Both o-Ps parameters change (stepwise) when in the medium phase transitions occur. For a more complete picture of the structural changes occurring in the matter we suggest to use an additional plot, in the coordinates, (τ₃, I₃). The hydrocarbons are selected to show the advantages following from the presentation of the results in the intensity-lifetime (INTI) plot.
11
Publication available in full text mode
Content available

Ortho-Positronium in Some n-Alkanes; Influence of Temperature and Pressure

51%
Zgardzińska B., Pietrow M., Goworek T., Wawryszczuk J.
Acta Physica Polonica A
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2006
|
vol. 110
|
issue 5
747-753
EN
Positron lifetime spectra were measured for a series of odd-numbered n-alkanes from C_{11}H_{24} to C_{19}H_{40} as a function of temperature and pressure. The ortho-Ps lifetimes in the rotator phase and the increase in intensity at the transition to that phase can be explained by location of Ps in the vicinity of kink-type conformers. The relation between o-Ps lifetime and molecule length can be described in the framework of extended Tao-Eldrup model. One can eliminate the effect of intensity rise in time by sample illumination or by application of high pressure. A decrease in temperature by 1 K is equivalent to an increase in pressure by about 4 MPa.
12
Content available remote

Gas Pressure Induced Porosity of CYTOP Polymer. A~Positron Study

45%
Zgardzińska B., Goworek T., Śniegocka M., Zaleski R., Dlubek G.
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|
vol. 125
|
issue 3
782-784
EN
The pore formation in CYTOP polymer under high pressure of argon or nitrogen gases was investigated by positron annihilation spectroscopy. In the range 0-70 MPa, formation of large open pores was observed. After reduction of pressure to normal one, the free volumes inside the polymer structure remained enlarged. The structure of CYTOP can be restored by applying the temperature over 470 K at normal pressure.
13
Content available remote

Analysis Procedure of the Positronium Lifetime Spectra for the J-PET Detector

18%
Dulski K., Zgardzińska B., Białas P., Curceanu C., Czerwiński E., Gajos A., Głowacz B., Gorgol M., Hiesmayr B., Jasińska B., Kisielewska-Kamińska D., Korcyl G., Kowalski P., Kozik T., Krawczyk N., Krzemień W., Kubicz E., Mohammed M., Pawlik-Niedźwiecka M., Niedźwiecki S., Pałka M., Raczyński L., Raj J., Rudy Z., Sharma N., Sharma S., Shivani S., Shopa R., Silarski M., Skurzok M., Wieczorek A., Wiślicki W., Zieliński M., Moskal P.
Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 5
1637-1640
EN
Positron annihilation lifetime spectroscopy has shown to be a powerful tool to study the nanostructures of porous materials. Positron emission tomograph is a device allowing imaging of metabolic processes e.g. in human bodies. A newly developed device, the Jagiellonian PET will allow positron annihilation lifetime spectroscopy in addition to imaging, thus combining both analyses providing new methods for physics and medicine. In this contribution we present a computer program that is compatible with the Jagiellonian PET software. We compare its performance with the standard program LT 9.0 by using positron annihilation lifetime spectroscopy data from hexane measurements at different temperatures. Our program is based on an iterative procedure, and our fits prove that it performs as good as LT 9.0.
14
Content available remote

Time Calibration of the J-PET Detector

18%
Skurzok M., Silarski M., Alfs D., Białas P., Shivani, Curceanu C., Czerwiński E., Dulski K., Gajos A., Głowacz B., Gorgol M., Hiesmayr B., Jasińska B., Kisielewska-Kamińska D., Korcyl G., Kowalski P., Kozik T., Krawczyk N., Krzemień W., Kubicz E., Mohammed M., Pawlik-Niedźwiecka M., Niedźwiecki S., Pałka M., Raczyński L., Raj J., Rudy Z., Sharma N., Sharma S., Shopa R., Wieczorek A., Wiślicki W., Zgardzińska B., Zieliński M., Moskal P.
Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 5
1641-1644
EN
The Jagiellonian positron emission tomograph project carried out in the Institute of Physics of the Jagiellonian University is focused on construction and tests of the first prototype of PET scanner for medical diagnostic which allows for the simultaneous 3D imaging of the whole human body using organic scintillators. The J-PET prototype consists of 192 scintillator strips forming three cylindrical layers which are optimized for the detection of photons from the electron-positron annihilation with high time-and high angular resolutions. In this article we present time calibration and synchronization of the whole J-PET detection system by irradiating each single detection module with a ²²Na source and a small detector providing common reference time for synchronization of all the modules.
15
Content available remote

Preliminary Studies of J-PET Detector Spatial Resolution

18%
Pawlik-Niedźwiecka M., Niedźwiecki S., Alfs D., Białas P., Curceanu C., Czerwiński E., Dulski K., Gajos A., Głowacz B., Gorgol M., Hiesmayr B., Jasińska B., Kisielewska D., Korcyl G., Kowalski P., Kozik T., Krawczyk N., Krzemień W., Kubicz E., Mohammed M., Pałka M., Raczyński L., Raj J., Rudy Z., Shivani, Silarski M., Skurzok M., Sharma N., Sharma S., Shopa R., Strzelecki A., Wieczorek A., Wiślicki W., Zgardzińska B., Zieliński M., Moskal P.
Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 5
1645-1648
EN
The J-PET detector, based on long plastic scintillator strips, was recently constructed at the Jagiellonian University. It consists of 192 modules axially arranged into three layers, read out from both sides by digital constant-threshold front-end electronics. This work presents preliminary results of measurements of the spatial resolution of the J-PET tomograph performed with ²²Na source placed at selected position inside the detector chamber.
16
Content available remote

Human Tissue Investigations Using PALS Technique - Free Radicals Influence

18%
Jasińska B., Zgardzińska B., Chołubek G., Pietrow M., Gorgol M., Wiktor K., Wysogląd K., Białas P., Curceanu C., Czerwiński E., Dulski K., Gajos A., Głowacz B., Hiesmayr B., Jodłowska-Jędrych B., Kamińska D., Korcyl G., Kowalski P., Kozik T., Krawczyk N., Krzemień W., Kubicz E., Mohammed M., Pawlik-Niedźwiecka M., Niedźwiecki S., Pałka M., Raczyński L., Rudy Z., Sharma N., Sharma S., Shopa R., Silarski M., Skurzok M., Wieczorek A., Wiktor H., Wiślicki W., Zieliński M., Moskal P.
Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 5
1556-1558
EN
The positron annihilation lifetime spectroscopy was applied to the samples of the human uterine leiomyomas and the normal myometrium tissues taken from the selected place of the uterus during a surgery. The method indicated differences in values of the measured positron annihilation lifetime spectroscopy parameters (lifetimes and intensities) between healthy and diseased tissue samples. The additional measurements were performed either in darkness or in presence of visible light which influenced the free radicals present in both kind of tissues and, as a result, made changes in free annihilation and o-Ps decay lifetime and intensity values.
17
Content available remote

A Method to Produce Linearly Polarized Positrons and Positronium Atoms with the J-PET Detector

18%
Mohammed M., Białas P., Curceanu C., Czerwiński E., Dulski K., Gajos A., Głowacz B., Gorgol M., Hiesmayr B., Jasińska B., Kisielewska D., Korcyl G., Kowalski P., Kozik T., Krawczyk N., Krzemień W., Kubicz E., Pawlik-Niedźwiecka M., Niedźwiecki S., Pałka M., Raczyński L., Raj J., Rudy Z., Sharma N., Sharma S., Shivani, Skurzok M., Silarski M., Wieczorek A., Wiślicki W., Zgardzińska B., Zieliński M., Moskal P.
Acta Physica Polonica A
|
2017
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vol. 132
|
issue 5
1486-1489
EN
A method for creating linearly polarized positrons and ortho-positronium (o-Ps) atoms with the J-PET detector is presented. The unique geometry and properties of the J-PET tomography enable one to design a positron source such that the quantization axis for the estimation of the linear polarization of produced o-Ps can be determined on the event by event basis in a direction of the positron motion. We intend to use ²²Na or other β⁺ decay isotopes as a source of polarized positrons. Due to the parity violation in the beta decay, the emitted positrons are longitudinally polarized. The choice of the quantization axis is based on the known position of the positron emitter and the reconstructed position of the positronium annihilation. We show that the J-PET tomography is equipped with all needed components.
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