High-energy Gamma-quanta Research Articles

Generation of Narrow Beams of Super High-Energy Gamma Quanta in the Resonant Compton Effect in the Field of a Strong X-ray Wave

The article presents a theoretical study of Oleinik resonances in the process of scattering a gamma quantum by an ultrarelativistic electron in the field of a strong electromagnetic wave with intensities up to 1027Wcm−2. The resonant kinematics for three possible resonant reaction channels in a strong external field have been studied in detail. It is shown that under resonant conditions, the scattering channels of the reaction effectively split into two first-order processes according to the fine structure constant, such as the external field-stimulated Compton effect. The annihilation channel of the reaction effectively decays into direct and reverse the external field-stimulated Breit–Wheeler processes. In the absence of interference from the reaction channels, a resonant differential cross-section was obtained in a strong external electromagnetic field. The cases when the energy of the initial electrons significantly exceeds the energy of the initial gamma quanta have been studied. At the same time, all particles (initial and final) fly in a narrow cone away from the direction of wave propagation. The conditions under which the energy of ultrarelativistic initial electrons is converted into the energy of a finite gamma quantum are studied. It is shown that the resonant differential cross-section of such a process significantly (by several orders of magnitude) exceeds the corresponding nonresonant cross-section. This theoretical study predicts a number of new physical effects that may explain the high-energy fluxes of gamma quanta produced near neutron stars and magnetars.

Search for High-Energy Gamma Quanta from the Cygnus Cocoon Source in October–November 2020

Search for High-Energy Gamma Quanta from the Cygnus Cocoon Source in October–November 2020

The Generation of High-Energy Electron–Positron Pairs during the Breit–Wheeler Resonant Process in a Strong Field of an X-ray Electromagnetic Wave

The Breit–Wheeler resonant process was theoretically studied in a strong X-ray electromagnetic wave field under conditions when the energy of one of the initial high-energy gamma quanta passes into the energy of a positron or electron. These conditions were realized when the energy of a high-energy gamma quantum significantly exceeded the characteristic Breit–Wheeler energy, which was determined using the parameters of the electromagnetic wave and the initial setup. Analytical formulas for the resonant differential cross-section were obtained. It is shown that the resonant differential cross-section significantly depends on the ratio between the energies of the initial gamma quanta and the characteristic Breit–Wheeler energy. With a decrease in the characteristic Breit–Wheeler energy, the resonant cross-section increases sharply and may exceed the corresponding non-resonant cross-section by several orders of magnitude. The results make it possible to obtain narrow beams of ultrarelativistic positrons (electrons) with energies of the order ∼102 GeV and could also be used to explain high-energy fluxes of positrons (electrons) near neutron stars, as well as to simulate QED processes in laser fusion.

Generation of Narrow Beams of Ultrarelativistic Positrons (Electrons) in the Breit–Wheeler Resonant Process Modified by the Field of a Strong Electromagnetic Wave

The resonant external field-assisted Breit–Wheeler process (Oleinik resonances) for strong electromagnetic fields with intensities that are less than the critical Schwinger field that has been theoretically studied. The resonant kinematics were studied in detail. The case of high-energy initial gamma quanta and emerging ultrarelativistic electron–positron pairs was studied. The resonant differential cross section was obtained. The generation of narrow beams of ultrarelativistic positrons (for Channel A) and electrons (for Channel B) was predicted with a probability that significantly exceeded the corresponding nonresonant process.

The effect of generation of narrow ultrarelativistic beams of positrons (electrons) in the process of resonant photoproduction of pairs on nuclei in a strong electromagnetic field

The generation of narrow beams of high-energy positrons (electrons) in the process of resonant photogeneration of ultrarelativistic electron–positron pairs by high-energy gamma quanta in the field of the nucleus and a strong electromagnetic wave is theoretically predicted. It is shown that if the energy of the initial gamma quanta significantly exceeds the characteristic energy of the process, then ultrarelativistic positrons (electrons) are emitted with energies very close to the energy of gamma quanta. Moreover, the resonant differential cross-section of such processes can exceed the corresponding differential cross-section without an external field by thirteen orders of magnitude. This effect makes it possible to obtain narrow beams of ultrarelativistic positrons (electrons) in strong electromagnetic fields with high probability.

The possibility of creating narrow beams of high-energy gamma quanta in the process of resonant spontaneous bremsstrahlung radiation of ultrarelativistic electrons on nuclei in strong electromagnetic fields

The production of narrow beams of high-energy gamma quanta in the process of resonant spontaneous bremsstrahlung radiation of ultrarelativistic electrons on nuclei in strong electromagnetic fields is predicted. This effect is realized under special experimental conditions for the frequencies and intensities of the laser installation. Resonant differential cross sections with simultaneous registration of the outgoing angle and the energy of the spontaneous gamma quantum, as well as a small number of absorbed photons of the wave, can exceed the corresponding differential cross section without an external field by 18–19 orders of magnitude. The obtained results can be used to obtain narrow beams of high-energy gamma quanta, as well as to explain high-energy gamma quanta near pulsars and magnetars.

Radiation of High-Energy Gamma Quanta by Ultrarelativistic Electrons on Nuclei in Strong X-ray Fields

The possibility of radiation of high-energy gamma quanta with energies of the order of 100 GeV by ultrarelativistic electrons on nuclei in strong X-ray fields with intensities up to ∼1027Wcm−2 was theoretically studied. It is shown that this effect can be realized under special experimental conditions in the process of resonant spontaneous bremsstrahlung radiation of ultrarelativistic electrons on nuclei in an external electromagnetic field. These special experimental conditions determine the characteristic energy of the electrons. This characteristic energy should be significantly less than the energy of the initial electrons. Under these conditions, spontaneous gamma quanta are emitted in a narrow cone with energies close to the energy of the initial electrons. Moreover, the resonant differential cross-sections of such processes can exceed the corresponding differential cross-section without an external field by twenty orders of magnitude. The results obtained can explain the occurrence of high-energy gamma quanta near pulsars and magnetars.

RADIATION DAMAGE IN URANIUM TARGET OF THE ACCELERATOR DRIVEN SYSTEM “KIPT NEUTRON SOURCE”

In this work, the rate of radiation damage production in a uranium target of the neutron source at NSC KIPT un-der electrons irradiation with an energy of 100 MeV was estimated. The contribution of elastic and inelastic proc-esses is determined: high-energy electrons and gamma quanta, photo-neutron production, fragments arising from photo-fission, damage from neutrons. It was found that the main input into damage production in a uranium target give fragments of photo-fission.

Resonant emission of hard gamma-quanta at scattering of ultrarelativistic electrons on a nucleus within the external light field

The contemporary theoretical investigation researches the resonant emission of high-energy gamma-quanta within the process of scattering of ultrarelativistic electrons on a nucleus in the external electromagnetic field. With implementation of the resonant conditions under the field ambience the particle in the intermediate state re-modulates into the real form. Therefore, the phenomenon examination determines the functional splitting of the second order process into a pair of first-order effects that possess a possibility to develop within two reaction channels. Consequently, the first channel characterizes the kinematics of electron scattering by a nucleus and following radiation of a spontaneous gamma-quantum. The second channel delineates the spontaneous gamma-quantum radiation by an electron with subsequent scattering on a nucleus. It is important to emphasize that within a specific range of observation the calculations derive three discrete magnitudes for the resonant frequency dependency on the angle of spontaneous photon radiation. As a result, the work represents an estimation of the resonant differential scattering cross-section in ratio to the scattering cross-section computed without the external field. In conclusion, various scientific facilities may verify the project data simulation (SLAC, FAIR, XFEL, ELI, XCELS).

Особенности развития длительных потоков высокоэнергичного гамма-излучения на разных стадиях солнечных вспышек

We have studied properties of sustained gamma fluxes having quantum energies of >100 MeV at different stages of flares with 1-min temporal resolution (Fermi/LAT). 
 The most probable process of emergence of high-energy gamma-quanta during the impulsive phase of flares (6 events) has been confirmed. Acceleration of particles, produced by flare energy release (at dissipation of current sheet), occurs when they interact with a shock front of a coronal mass ejection (CME), which develops in the same active region at the same time. Nuclear interactions of accelerated protons (>500 MeV) with plasma ions lead further to the emergence of high-energy gamma-quanta. We have established that the interaction between a flare flux and a high-speed CME during the flare impulsive phase occurs within fairly limited periods — from 2 to 16 min. In the events considered, we have found a direct connection between maximum gamma flux F max (γ > 100 MeV) and CME velocity.
 High maximum values of gamma fluxes are typical of the flare impulsive phase: 3.5·10⁻⁴ cm⁻²s⁻¹ ≤ F max (γ > 100 MeV) ≤ 1.3·10⁻² cm⁻² s⁻¹. At the same time, the value F max (γ > 100 MeV) = 0.013 cm⁻²s⁻¹ was the highest for the events observed by Fermi/LAT from 2008 to 2017.
 During the development of CMEs moving with a supersonic speed, shock waves are formed which are the major power source of accelerated particles during the main phase of gradual flares. In some cases, however, the impact of shock waves on particle acceleration is the greatest in the short impulsive phase.
 To reveal parameters most effectively influencing the generation of high-energy gamma-ray emission, we have compared 17 flare events. The most significant parameter proved to be the time interval of joint action of flare process and CME shocks.
 We have established that during simultaneous development of flare process and CME attendant on the flare, the most efficient particle acceleration occurs which gives rise to maximum fluxes of high-energy gamma-quanta.

Features of development of sustained fluxes of high-energy gamma-ray emission at different stages of solar flares

We have studied properties of sustained gamma fluxes having quantum energies of >100 MeV at different stages of flares with 1-min temporal resolution (Fermi/LAT). 
 The most probable process of emergence of high-energy gamma-quanta during the impulsive phase of flares (6 events) has been confirmed. Acceleration of particles, produced by flare energy release (at dissipation of current sheet), occurs when they interact with a shock front of a coronal mass ejection (CME), which develops in the same active region at the same time. Nuclear interactions of accelerated protons (>500 MeV) with plasma ions lead further to the emergence of high-energy gamma-quanta. We have established that the interaction between a flare flux and a high-speed CME during the flare impulsive phase occurs within fairly limited periods — from 2 to 16 min. In the events considered, we have found a direct connection between maximum gamma flux F max (γ > 100 MeV) and CME velocity.
 High maximum values of gamma fluxes are typical of the flare impulsive phase: 3.5·10⁻⁴ cm⁻²s⁻¹ ≤ F max (γ > 100 MeV) ≤ 1.3·10⁻² cm⁻² s⁻¹. At the same time, the value F max (γ > 100 MeV) = 0.013 cm⁻²s⁻¹ was the highest for the events observed by Fermi/LAT from 2008 to 2017.
 During the development of CMEs moving with a supersonic speed, shock waves are formed which are the major power source of accelerated particles during the main phase of gradual flares. In some cases, however, the impact of shock waves on particle acceleration is the greatest in the short impulsive phase.
 To reveal parameters most effectively influencing the generation of high-energy gamma-ray emission, we have compared 17 flare events. The most significant parameter proved to be the time interval of joint action of flare process and CME shocks.
 We have established that during simultaneous development of flare process and CME attendant on the flare, the most efficient particle acceleration occurs which gives rise to maximum fluxes of high-energy gamma-quanta.

Photonuclear Technology for Hidden Explosive Detection

The photonuclear technology for explosive detection is based on the recording of the decays of short-lived 12B and 12N isotopes. These radionuclides are formed in reactions on 14N and 13C nuclei under effect of irradiation by high-energy gamma quanta. Carbon and nitrogen are found in the composition of all explosives. We can obtain the information for the identification of the explosives based on the time spectra of the signals of isotope decays after the pulsed irradiation of the object. The operational parameters of the detectors for baggage screening and humanitarian demining were obtained by computer simulation. We developed a laboratory unit consisting of a 55-MeV racetrack microtron, 250-L Cherenkov water counter, and VME standard electronics to study the technology. The experimental results obtained using this equipment are discussed.

The Search for High-Energy Photons and Neutrinos Producing Extensive Air Showers with Energies E > 1018 eV and Zenith Angles θ > 70° in the Yakutsk Array Data

The method of searching for showers generated by neutral particles such as high-energy gamma quanta and astrophysical neutrinos is described, and the results of this search are presented. These results were obtained in the combined analysis of data on electrons, muons, and Cherenkov radiation of EASs and their temporal responses in scintillation and Cherenkov detectors. An upper limit on the flux of gamma quanta with energies of 3 × 1018, 1019, and 3 × 1019 eV was obtained. The multiparameter analysis of shower characteristics did not reveal EASs produced by neutrinos.

Search for neutrino generated air shower candidates with energy ≥ 1019 eV and Zenith angle θ

The description of the methodology and results of searching for air showers generated by neutral particles such as high energy gamma quanta and astroneutrinos are presented. For this purpose, we conducted a comprehensive analysis of the data: the electron, the muon and the EAS Cerenkov light, and their response time in scintillation and Cherenkov detectors. Air showers with energy more than 5·1018 eV and zenith angle θ ≥ 55∘ are selected and analyzed. Search results indicate a lack of air shower events formed by gamma-rays or high-energy neutrinos, but it does not mean that such air showers do not exist in nature; for example, experiments that recorded showers having a marked low muon content, i.e., “Muonless”, are likely to be candidates for showers produced by neutral primary particles.

Yarman’s approach predicts anomalous gravitational bending of high-energy gamma-quanta

We predict anomalous gravitational bending of gamma rays using the gravitational framework of Yarman’s approach, abbreviated hereinafter as “YARK” from the initials of the co-authors to designate their teamwork. In contrast to the metric layout of the general theory of relativity (GTR), YARK theory is founded directly on the energy conservation law pertaining to interaction between masses. Despite the fact that predictions made respectively by GTR and YARK regarding cornerstone astrophysical observations appear remarkably identical to each other, the philosophies behind them are irreconcilably different. To test which theory comes closer to the reality, one should propose ways to distinguish their success at the experimental level. Note that bending of light in GTR represents a purely metric effect, which cannot depend on the energy of photons, whereas YARK conceptually allows the deflection of photons across a gravitational environment contingent upon either their wave-like or corpuscular-like behavior. In the case of “wave-like propagation”, which we deem particular to low-energy photons (including the visible range), YARK arrives at the same results as GTR; whereas for high-energy gamma-quanta, which we deem to signify “corpuscular-like propagation”, the deflection in a gravitational field practically vanishes in YARK. Given this opportunity to test YARK theory against GTR, we discuss possible experimental setups relevant to the subject.

Interaction of high energy gamma-quanta with crystal surface: Classical reflection and interference phenomena

The interaction of high energy gamma-quanta with crystal surfaces under small sliding angles is considered. It is shown that under certain conditions, such interactions can be described in classical wave theory formalism up to the energies, exceeding 1011eV.

Simulation of generation of bremsstrahlung gamma quanta upon irradiation of thin metal films by ultra-intense femtosecond laser pulses

We report the results of simulations of generation of bremsstrahlung gamma quanta upon irradiation of a thin-film metal target by ultra-intense femtosecond laser pulses. It is shown by the example of a thin gold target that the mean electron energy is twenty five times higher than the mean energy of gamma quanta generated by them. A simple approximating formula is proposed, which establishes a one-to-one relation between these quantities. The angular distributions of electrons and gamma quanta are studied. It is shown that only the angular distribution of high-energy gamma quanta repeats the angular distribution of the electrons leaving the target.

CO-57: an electrophoretic investigation on the properties in the ultradiluted aqueous solutions

Radioactive Cobalt is used in nuclear medicine mainly for radiotherapy as well as radiodiagnostics. Radiotherapeutic application usually includes extracorporeal gamma irradiation by means of nuclide Co-60, which spectrum is rich of very high energy gamma quanta. At the contrary, the isotope Co-57 emits merely low energy gamma quanta, thus represents a soft gamma emitter, highly suitable for the clinical radiodiagnostics. In-vivo treatment with the radioactive Cobalt drugs, however, provokes the risk of patient`s blood and tissue radioactive contamination, due to appearance of simple Cobalt ions and their insoluble forms. Therefore, it could be of a practical interest to know chemical properties as well as the behavior of the hydrated Cobalt ions in water solutions at microconcentrations as low as 10-6 - 10-7 mol.l-1. In this paper the highly suitable electromigration technique is discussed and applied. A set of collected radioanalytical data, including values of parameters such as ion mobilities, molar volumes, Stocks radii, hydration numbers and diffusion coefficients as well as their temperature dependence in water solutions is presented. Scripta Scientifica Medica 2008; 40(1):13-17

Detection of metagalactic and galactic sources of very high-energy gamma-quanta and neutrinos with the mirror Cherenkov telescope SHALON

Gamma-astronomy and neutrino astronomy are unique experimental possibilities to search for sources of high-energy cosmic rays ( 10 12 – 10 14 eV ) . Experimental data on sources of γ -quanta with the energy > 1 TeV are characterized by the fact that observed metagalactic sources (active galactic nuclei), being different in power from galactic sources by the factor of 10 6 – 10 7 , do not differ in the energy spectrum, F ( > E γ ) ∝ E γ - 1.3 ± 0.15 . The power of the metagalactic sources and their unlimited number casts doubts on the assumption of a galactic origin of the observed cosmic-ray flux. It is possible to assume that the uniform cosmic-ray spectrum is formed by “braking” in multiple elastic or inelastic collisions with relict photons in intergalactic space. Thus, the observed distribution of protons and cosmic-ray nuclei with the spectral index 2.72 ± 0.02 ( = 2.718 … , the Napier's constant) may be a consequence of such a “braking” that warms up the relict photons. Problems in observation of extensive air showers generated by neutrinos are connected with an extremely small cross section of inelastic collisions of neutrinos with nuclei. However, two facts allow to search for showers generated by neutrinos: (1) a hadron cascade with the primary energy of more than 10 12 eV leaves a mountain ridge to the atmosphere from the depth ∼ 300 g / cm 2 without an essential loss of the total energy in the hadron cascade, and (2) air Cherenkov radiation from such hadron cascades will be observed with a 7.5 km distant telescope over an area of more than 7 × 10 5 m 2 . This partially compensates the small cross section of inelastic neutrino collisions.

On the coherent radiation of relativistic electrons and positrons in crystal in the range of high energies of gamma-quanta

The formulae for the cross-section of coherent radiation of high energy gamma-quanta by relativistic electrons and positrons in crystal taking into account the contribution of the second Born approximation into radiation are obtained. The dependence of the radiation cross-section in the field of atomic plane on the sign of charge of the particle is considered.