XVIII.—The Emission of Long-Range Alpha Particles in Fission

1963 ◽  
Vol 66 (3) ◽  
pp. 192-209
Author(s):  
N. Feather
Keyword(s):  
Long Range ◽  
Alpha Particle ◽  
Experimental Tests ◽  
Alpha Particles ◽  
Ternary Fission ◽  
Neutron Excess ◽  
Final Energy ◽  
Open Question

It is generally agreed that the long-range alpha particles of fission are set free before the fragment nuclei have acquired more than a small fraction of their final energy of separation, but whether the alpha particle is liberated before the instant of scission, at that instant, or from one of the fragment nuclei very shortly thereafter, has remained an open question. Each of these views has been seriously advocated. These various hypotheses are examined in relation to recently published information regarding the distribution of mass in low-eneigy ternary fission, and other considerations, and it is suggested that the hypothesis having the strongest claim to attention is that which assumes that the alpha particles originate in the heavy fragments exclusively, being liberated, very shortly after the instant of scission, with probability not much less than unity, from fragment nuclei of low yield and small neutron excess. Conclusions which would follow, if this hypothesis were accepted, are indicated, and possible experimental tests of these conclusions are suggested.

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.

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.

Targeted Alpha-Particle Immunotherapy for Acute Myeloid Leukemia

2014 ◽  
pp. e126-e131 ◽  
Author(s):  
Joseph G. Jurcic ◽  
Todd L. Rosenblat
Keyword(s):  
Acute Myeloid Leukemia ◽  
Phase I ◽  
Alpha Particle ◽  
Myeloid Leukemia ◽  
Hematopoietic Cell Transplantation ◽  
Myeloid Cell ◽  
Multicenter Trial ◽  
Alpha Particles ◽  
Particle Therapy ◽  
Acute Myeloid

Because alpha-particles have a shorter range and a higher linear energy transfer (LET) compared with beta-particles, targeted alpha-particle immunotherapy offers the potential for more efficient tumor cell killing while sparing surrounding normal cells. To date, clinical studies of alpha-particle immunotherapy for acute myeloid leukemia (AML) have focused on the myeloid cell surface antigen CD33 as a target using the humanized monoclonal antibody lintuzumab. An initial phase I study demonstrated the safety, feasibility, and antileukemic effects of bismuth-213 (213Bi)-labeled lintuzumab. In a subsequent study, 213Bi-lintuzumab produced remissions in some patients with AML after partial cytoreduction with cytarabine, suggesting the utility of targeted alpha-particle therapy for small-volume disease. The widespread use of 213Bi, however, is limited by its short half-life. Therefore, a second-generation construct containing actinium-225 (225Ac), a radiometal that generates four alpha-particle emissions, was developed. A phase I trial demonstrated that 225Ac-lintuzumab is safe at doses of 3 μCi/kg or less and has antileukemic activity across all dose levels studied. Fractionated-dose 225Ac-lintuzumab in combination with low-dose cytarabine (LDAC) is now under investigation for the management of older patients with untreated AML in a multicenter trial. Preclinical studies using 213Bi- and astatine-211 (211At)-labeled anti-CD45 antibodies have shown that alpha-particle immunotherapy may be useful as part conditioning before hematopoietic cell transplantation. The use of novel pretargeting strategies may further improve target-to-normal organ dose ratios.

The kinetic energy of fragments and alpha particles in the ternary fission of U235

1964 ◽  
Vol 15 (1) ◽  
pp. 659-663
Author(s):  
V. N. Dmitriev ◽  
K. A. Petrzhak ◽  
Yu. F. Romanov
Keyword(s):  
Kinetic Energy ◽  
Alpha Particles ◽  
Ternary Fission

Use Of A Solid-State Detector for the Analysis of X-Rays Excited in Silicate Rocks by Alpha-Particle Bombardment

1971 ◽  
Vol 15 ◽  
pp. 388-406 ◽  
Author(s):  
Ernest J. Franzgrote
Keyword(s):  
Alpha Particle ◽  
Particle Bombardment ◽  
Pulse Height ◽  
Silicon Detector ◽  
Alpha Particles ◽  
X Rays ◽  
Solid State Detector ◽  
X Ray ◽  
Alpha Scattering ◽  
Silicate Rocks

The analysis of alpha-excited X-rays has been studied as a possible addition to the alpha-scattering technique used on the Surveyor spacecraft for the first in situ chemical analyses of the lunar surface.Targets of pure elements, simple compounds, and silicate rocks have been exposed to alpha particles and other radiation from a curium-214 source and the resulting X-ray spectra measured by means of a cooled lithium-drifted silicon detector and pulse-height analysis.Alpha-particle bombardment is a simple and efficient means of X-ray excitation for light elements. Useful spectra of silicate rocks may be obtained in a few minutes with a source activity of 50 millicuries, a detector area of 0.1 cm2 and a sample distance of 3 cm. An advantage over electron excitation is the higher characteristic response relative to the bremsstrahlung continuum. Peak-to- background ratios of greater than 100 to 1 have been obtained for elemental targets. Relative efficiencies of X-ray excitation by alpha particles and by X-rays from the curium source have been determined.Resolution of the detector system used is approximately 150 eV for the lighter elements. This is sufficient to resolve the Kα X-rays of the geochemically important elements, Na, Mg, Al, and Si in silicate rocks. Although these and lighter elements are analyzed as well or better by the alpha-scattering and alpha-proton technique, the X-ray mode enables results to be obtained more quickly.The study shows that the addition of an X-ray mode to the alpha-scattering analysis technique would result in a significant improvement in analytical capability for the heavier elements. In particular, important indicators of geochemical differentiation such as K and Ca (which are only marginally separated in an alpha-scattering and alpha-proton analysis) may be determined quantitatively by measuring the alpha-excited X-rays. An X-ray detector is under consideration as an addition to an alpha-scattering instrument now under development for possible use on a Mars-lander mission.

Determination of CR-39 and LR-115 Type II Mean Critical Angle of Etching Using a New Monte Carlo Code

2020 ◽  
Author(s):  
Hicham Harrass ◽  
Abdellatif Talbi ◽  
Rodouan Touti
Keyword(s):  
Monte Carlo ◽  
Alpha Particle ◽  
Critical Angle ◽  
Current Method ◽  
Particle Energy ◽  
Alpha Particles ◽  
Monte Carlo Code ◽  
Type Ii ◽  
Alpha Particle Energy ◽  
The Mean

Abstract CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs) are both used, in order to assess the concentration of nucleus belonging to 238U and 232Th series, these ones can be also used to measure radon 222Rn and thoron 220Rn gases in different locations. In this paper, a Monte Carlo code was developed to calculate the mean critical angle for which alpha particles emitted from 238U and 232Th families in studied material samples reach CR-39 and LR-115 type II surfaces and bring about latent tracks on them. The dependence of the SSNTDs mean critical angle on the removed thickness, the initial alpha particle energy has been studied. A linear relationship between CR-39 mean critical angle and the initial alpha particle energy for different removed thicknesses has been found. This straightforward relationship allows determining quickly the mean critical angle of etching which corresponds to initial alpha particle energy for a given removed thickness. CR-39 mean critical angle ranged from 59° for an alpha particle emitted by 212Po to 71° for an alpha particle emitted by 232Th, for the value of removed thickness of 6 µm; whereas LR-115 type II mean critical angle does not depend on the initial alpha particle energy except for 232Th, 238U, 230Th and 234Ra when the removed thickness ranged from 6 µm to 8 µm. Obtained data by using the current method and those obtained in the literature [18] are in good agreement with each other.

Continuous Energy Spectra of Protons and Alpha Particles Emitted by the Deuteron and Alpha Particle Reaction

1967 ◽  
Vol 22 (1) ◽  
pp. 28-34 ◽  
Author(s):  
Kiyoji Fukunaga ◽  
Hitoshi Nakamura ◽  
Tetsumi Tanabe ◽  
Kazuhiko Hosono ◽  
Seishi Matsuki
Keyword(s):  
Alpha Particle ◽  
Alpha Particles ◽  
Energy Spectra ◽  
Continuous Energy
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