Zoran Kaliman

Calculation of nuclear excitation in an electron transition

Abstract We have made a theoretical investigation of nuclear excitation during an electron transition (NEET). Our approach allows us to express the NEET probabilities in terms of the excited nuclear level width, the energy difference between the nuclear and electron transition, the Coulomb interaction between the initial electron states, and the electron level width. A comparison is made with the available experimental results.

Mechanism for nuclear excitation during positron annihilation using Coulomb wave functions

Abstract We have calculated cross sections for the process of nuclear excitation during positron annihilation on any bound electron. We used Coulomb wave functions for the electron and positron.

The Neutron Dose Equivalent Around High Energy Medical Electron Linear Accelerators

The measurement of neutron dose equivalent was made in four dual energy linear accelerator rooms. Two of the rooms were reconstructed after decommissioning of 60Co units, so the main limitation was the space. The measurements were performed by a nuclear track etched detectors LR-115 associated with the converter (radiator) that consist of 10B and with the ac - tive neutron detector Thermo BIOREM FHT 742. The detectors were set at several locations to evaluate the neutron ambient dose equivalent and/or neutron dose rate to which medical personnel could be exposed. Also, the neutron dose dependence on collimator aperture was analyzed. The obtained neutron dose rates outside the accelerator rooms were several times smaller than the neutron dose rates in side the accelerator rooms. Never the less, the measured neutron dose equivalent was not negligible from the aspect of the personal dosimetry with almost 2 mSv a year per person in the areas occupied by staff (conservative estimation). In rooms with 15 MV accelerators, the neutron exposure to the personnel was significantly lower than in the rooms having 18 MV accelerators installed. It was even more pronounced in the room reconstructed after the 60Co decommissioning. This study confirms that shielding from the neutron radiation should be considered when building vaults for high energy linear accelerators, especially when the space constraints exist.

Positronium interaction with low-energy radiation

The cross sections of elastic photon scattering, Compton scattering and photodisintegration for positronium are calculated for incident photon energies below 3 keV. The relation between positronium and hydrogen matrix elements for these processes is established and we compare our positronium cross section calculations with the corresponding hydrogenic data. We present the model for the positronium triplet state depletion before annihilation, when the positronium atoms are exposed to black-body radiation, and the breakup process occurs. We discuss the relevance of our breakup calculation for the positron annihilation process in solar flares.

Nuclear excitation by positron annihilation with bound electrons in a screened atomic potential

Abstract We have calculated the total cross section for the process of nuclear excitation in positron-bound electron annihilation. The calculations presented in this work use a spherically symmetric screened atomic potential. Comparisons with more approximate treatments of the process are made.

Wave–particle duality of radiation in Compton scattering

In this work we analyze the wave–particle aspects of radiation in (incoherent) Compton scattering in the radiation energy range from 2–100 keV. From the calculated cross sections of the scattering from the electron (positron), hydrogen and positronium we construct the interpretation functions (IFs), where our assertion is that the Compton scattering from the free electron (positron) is an established example of the particle behavior of radiation. These IFs estimate the possibility of the interpretation of radiation in terms of waves or particles in an analogy with the analysis carried out in the coherent scattering of light. Based on these IFs we propose a new criterion for the estimation of the validity of the impulse approximation (IA).

Disintegration of positronium: Low energy Compton scattering and photoabsorption

We study interference effects in Compton scattering of a photon from positronium. Interference effects, which are due to the binding of an electron and a positron, are important at lower energies up to several keV. In our study we use full nonrelativistic electron/positron-photon interaction.

Interference effects in Compton scattering from positronium and from H2 and H2+ molecules

We study the interference effects in Compton scattering of a photon from positronium and from the simplest molecules H2 and H2+ in their ground states. We will discuss the adequacy of impulse approximation in describing these interference effects.