DETECTION AND DISCRIMINATION BETWEEN ALPHA PARTICLES AND PROTONS BASED ON PHONONIC CRYSTALS MATERIALS

2019 ◽  
Vol 26 (07) ◽  
pp. 1850219 ◽  
Author(s):  
AHMED MEHANEY ◽  
MOSTAFA F. EISSA ◽  
ARAFA H. ALY
Keyword(s):  
Polymethyl Methacrylate ◽  
Alpha Particle ◽  
Elastic Waves ◽  
Incident Energy ◽  
High Probability ◽  
Radiation Detector ◽  
Thin Sheet ◽  
Phononic Crystal ◽  
Phononic Crystals ◽  
Alpha Particles

Ionizing particles detection based on phonons counting are considered as a growing research point of great interest. Phononic crystal (PnC) detectors have a higher resolution than other detectors. In the present work, we shall prepare a setup of a radiation detector based on a 1D PnC. The PnC detector can be used in detection and discrimination between protons and alpha particles with incident energy 1[Formula: see text]MeV. We have proposed a model capable of filtering the energies of two different ionizing particles (proton and alpha particle) of specific lattice frequencies in steps. Firstly, the high probability of phonons production was found at transmitted energy 5[Formula: see text]KeV from the whole path of protons and alpha particles through a vertical thin sheet made from Mylar and Polymethyl methacrylate (PMMA), respectively. The outgoing elastic waves are subjected to propagate through the proposed PnCs structure (Teflon-Polyethylene)2 that shows the different transmission percentage to each particle. Therefore, the detection and discrimination between ionizing ions were achieved.

scholarly journals An elastic fiber based on phononic crystals

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Farzaneh Motaei ◽  
Ali Bahrami
Keyword(s):  
Crystal Structure ◽  
Elastic Waves ◽  
Acoustic Waves ◽  
Elastic Fiber ◽  
Phononic Crystal ◽  
Phononic Crystals ◽  
Core Region ◽  
Crystal Fiber ◽  
The Core ◽  
First Time

AbstractIn this study, a novel elastic phononic crystal fiber has been presented for the first time. This proposed structure can expand the sonic communications field, significantly. In order to realize the elastic fiber performance, solid–solid phononic crystal has been utilized. The phononic crystal structure operates as cladding in surroundings and central region acts as core of fiber by elimination of rods. Incident acoustic waves with transverse polarization have confined and propagated in the core region of the phononic crystal fiber. Two types of phononic crystal fiber with different core radii have been investigated. Incident elastic waves can confine in the core region with confinement factor higher than 500. Also, longitudinal losses have been achieved low and equal to 0.35 dB/km.

scholarly journals Autoradiography Imaging in Targeted Alpha Therapy with Timepix Detector

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Ruqaya AL Darwish ◽  
Alexander Hugo Staudacher ◽  
Eva Bezak ◽  
Michael Paul Brown
Keyword(s):  
Alpha Particle ◽  
Radiation Detector ◽  
Absorbed Dose ◽  
Compartmental Analysis ◽  
Alpha Particles ◽  
Imaging Data ◽  
Analysis Model ◽  
Particle Emissions ◽  
Targeted Alpha Therapy ◽  
Alpha Therapy

There is a lack of data related to activity uptake and particle track distribution in targeted alpha therapy. These data are required to estimate the absorbed dose on a cellular level as alpha particles have a limited range and traverse only a few cells. Tracking of individual alpha particles is possible using the Timepix semiconductor radiation detector. We investigated the feasibility of imaging alpha particle emissions in tumour sections from mice treated with Thorium-227 (using APOMAB), with and without prior chemotherapy and Timepix detector. Additionally, the sensitivity of the Timepix detector to monitor variations in tumour uptake based on the necrotic tissue volume was also studied. Compartmental analysis model was used, based on the obtained imaging data, to assess the Th-227 uptake. Results show that alpha particle, photon, electron, and muon tracks were detected and resolved by Timepix detector. The current study demonstrated that individual alpha particle emissions, resulting from targeted alpha therapy, can be visualised and quantified using Timepix detector. Furthermore, the variations in the uptake based on the tumour necrotic volume have been observed with four times higher uptake for tumours pretreated with chemotherapy than for those without chemotherapy.

Nuclear Electrons and Nuclear Structure

2018 ◽  
Author(s):  
Roger H. Stuewer
Keyword(s):  
Nuclear Structure ◽  
Beta Decay ◽  
Gamma Rays ◽  
Alpha Particle ◽  
Continuous Distribution ◽  
Alpha Particles ◽  
Light Nuclei ◽  
Coincidence Method ◽  
Wolfgang Pauli ◽  
Beta Particles

Serious contradictions to the existence of electrons in nuclei impinged in one way or another on the theory of beta decay and became acute when Charles Ellis and William Wooster proved, in an experimental tour de force in 1927, that beta particles are emitted from a radioactive nucleus with a continuous distribution of energies. Bohr concluded that energy is not conserved in the nucleus, an idea that Wolfgang Pauli vigorously opposed. Another puzzle arose in alpha-particle experiments. Walther Bothe and his co-workers used his coincidence method in 1928–30 and concluded that energetic gamma rays are produced when polonium alpha particles bombard beryllium and other light nuclei. That stimulated Frédéric Joliot and Irène Curie to carry out related experiments. These experimental results were thoroughly discussed at a conference that Enrico Fermi organized in Rome in October 1931, whose proceedings included the first publication of Pauli’s neutrino hypothesis.

scholarly journals Drift kinetic theory of alpha transport by tokamak perturbations

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Elizabeth A. Tolman ◽  
Peter J. Catto
Keyword(s):  
Heat Flux ◽  
Kinetic Theory ◽  
Alpha Particle ◽  
Heat Fluxes ◽  
Alpha Particles ◽  
Alpha Power ◽  
Mode Amplitude ◽  
Effective Collision Frequency ◽  
Perturbation Frequency ◽  
Particle Confinement

Upcoming tokamak experiments fuelled with deuterium and tritium are expected to have large alpha particle populations. Such experiments motivate new attention to the theory of alpha particle confinement and transport. A key topic is the interaction of alpha particles with perturbations to the tokamak fields, including those from ripple and magnetohydrodynamic modes like Alfvén eigenmodes. These perturbations can transport alphas, leading to changed localization of alpha heating, loss of alpha power and damage to device walls. Alpha interaction with these perturbations is often studied with single-particle theory. In contrast, we derive a drift kinetic theory to calculate the alpha heat flux resulting from arbitrary perturbation frequency and periodicity (provided these can be studied drift kinetically). Novel features of the theory include the retention of a large effective collision frequency resulting from the resonant alpha collisional boundary layer, correlated interactions over many poloidal transits and finite orbit effects. Heat fluxes are considered for the example cases of ripple and the toroidal Alfvén eigenmode (TAE). The ripple heat flux is small. The TAE heat flux is significant and scales with the square of the perturbation amplitude, allowing the derivation of constraints on mode amplitude for avoidance of significant alpha depletion. A simple saturation condition suggests that TAEs in one upcoming experiment will not cause significant alpha transport via the mechanisms in this theory. However, saturation above the level suggested by the simple condition, but within numerical and experimental experience, which could be accompanied by the onset of stochasticity, could cause significant transport.

scholarly journals Nuclear excitation and disintegration collisions involving strong Interaction─I

1937 ◽  
Vol 162 (911) ◽  
pp. 529-556 ◽  
Keyword(s):  
Strong Interaction ◽  
Incident Energy ◽  
High Probability ◽  
Collision Cross Section ◽  
Energy Levels ◽  
Stable Complex ◽  
Nuclear Excitation ◽  
Resonance Effects ◽  
Resonance Phenomena ◽  
Probability Of Capture

The study of collisions between nuclear particles has developed to a remarkable extent with the discovery of the neutron and the introduction of artificial methods for effecting nuclear disintegration. It has been found in the last few years that the interpretation of the observed results is by no means as simple as was first expected. This situation is most apparent when the explanation of the variation of probability of capture of slow neutrons by different nuclei is considered. This probability varies in a very irregular manner from element to element and pronounced selective effects occur in certain cases. Attempts to explain (Elsasser and Perrin 1935; Bethe 1935) these resonance phenomena in terms of the usual approximations of quantum collision theory were soon found to be inadequate, All such attempts were based on the assumption that the Chance of a nuclear collision being elastic is high compared with that of its resulting in capture or excitation. A high probability of capture (with emission of radiation) or excitation could then only appear together with a high probability of elastic collision and this is frequently contradicted by the experimental results. The sharpness of the observed resonance phenomena was also difficult to under­stand on this basis. It was first pointed out by Bohr (1936) that the initial assumptions concerning the probability of elastic collisions, virtually involving the treatment of the elastic scattering as a one-body problem in the first approximation, cannot be valid for nuclei in which the particles, even is existing separately in the nuclei at all, are so closely packed. On making a close collision with a nucleus a particle, such as an α -particle, neutron or proton, comes into close and strong interaction with a number of nuclear particles and its incident energy becomes distributed among them. It is only when a particular particle receives sufficient energy to leave the quasi-stable complex formed that a disintegration particle is emitted. (This may of course be the original incident particle, in which case the collision would be an elastic or excitation one.) Otherwise the surplus energy is emitted as radiation. The resonance phenomena arise from the energy levels of the quasi-stable complex. If the incident energy is such that the total energy is equal or nearly equal to that of one of these energy levels, the range of interaction and hence the collision cross-section is quite large. This point of view must be adopted not only when dealing with neutron collisions but in all cases in which the impinging particle does not possess an energy greatly in excess of the minimum necessary for the process to occur. Disintegrations produced by charged particles, in which resonance effects have been observed for some time (Feather 1937, P. 154), must therefore be capable of description in this way.

Thermal Design of Highly-Efficient Thermoelectric Materials With Atomic-Scale Three-Dimensional Phononic Crystals

2007 ◽  
Author(s):  
Jean-Numa Gillet ◽  
Yann Chalopin ◽  
Sebastian Volz
Keyword(s):  
Thermal Conductivity ◽  
Bulk Material ◽  
Phononic Crystal ◽  
Three Dimensional ◽  
Mean Free Path ◽  
Dispersion Curves ◽  
Phononic Crystals ◽  
Thermal Design ◽  
Atomic Scale ◽  
Thermal Insulating

Owing to their thermal insulating properties, superlattices have been extensively studied. A breakthrough in the performance of thermoelectric devices was achieved by using superlattice materials. The problem of those nanostructured materials is that they mainly affect heat transfer in only one direction. In this paper, the concept of canceling heat conduction in the three spatial directions by using atomic-scale three-dimensional (3D) phononic crystals is explored. A period of our atomic-scale 3D phononic crystal is made up of a large number of diamond-like cells of silicon atoms, which form a square supercell. At the center of each supercell, we substitute a smaller number of Si diamond-like cells by other diamond-like cells, which are composed of germanium atoms. This elementary heterostructure is periodically repeated to form a Si/Ge 3D nanostructure. To obtain different atomic configurations of the phononic crystal, the number of Ge diamond-like cells at the center of each supercell can be varied by substitution of Si diamond-like cells. The dispersion curves of those atomic configurations can be computed by lattice dynamics. With a general equation, the thermal conductivity of our atomic-scale 3D phononic crystal can be derived from the dispersion curves. The thermal conductivity can be reduced by at least one order of magnitude in an atomic-scale 3D phononic crystal compared to a bulk material. This reduction is due to the decrease of the phonon group velocities without taking into account that of the phonon average mean free path.

Proton Beam Abundance Variations and Their Relation to Alpha Particle Properties

2021 ◽  
Vol 923 (2) ◽  
pp. 170
Author(s):  
Tereza Ďurovcová ◽  
Jana Šafránková ◽  
Zdeněk Němeček
Keyword(s):  
Solar Wind ◽  
Proton Beam ◽  
Alpha Particle ◽  
Source Region ◽  
Radial Distance ◽  
Alpha Particles ◽  
Momentum Balance ◽  
Particle Interactions ◽  
Coulomb Collisions ◽  
Particle Properties

Abstract Less abundant but still dynamically important solar wind components are the proton beam and alpha particles, which usually contribute similarly to the total ion momentum. The main characteristics of alpha particles are determined by the solar wind source region, but the origin of the proton beam and its properties are still not fully explained. We use the plasma data measured in situ on the path from 0.3 to 1 au (Helios 1 and 2) and focus on the proton beam development with an increasing radial distance as well as on the connection between the proton beam and alpha particle properties. We found that the proton beam relative abundance increases with increasing distance from the Sun in the collisionally young streams. Among the mechanisms suggested for beam creation, we have identified the wave–particle interactions with obliquely propagating Alfvén modes being consistent with observations. As the solar wind streams get collisionally older, the proton beam decay gradually dominates and the beam abundance is reduced. In search for responsible mechanisms, we found that the content of alpha particles is correlated with the proton beam abundance, and this effect is more pronounced in the fast solar wind streams during the solar maximum. We suggest that Coulomb collisions are the main agent leading to merging of the proton beam and core. We are also showing that the variations of the proton beam abundance are correlated with a decrease of the alpha particle velocity in order to maintain the total momentum balance in the solar wind frame.

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