Kinetics of nonhomogeneous chemical processes in tracks of high-energy charged particles

1990 ◽  
Vol 68 (9) ◽  
pp. 858-871 ◽  
Author(s):  
A. Hummel
Keyword(s):  
Spatial Distribution ◽  
Large Fraction ◽  
Charged Particles ◽  
Coulomb Field ◽  
High Energy ◽  
Transient Species ◽  
Charged Species ◽  
Solvent Molecules ◽  
Kinetics Of ◽  
Initial Spatial Distribution

High-energy charged particles, when slowing down in a molecular medium, lose their energy by electronic excitations and ionizations of molecules along their paths. If the secondary electrons that are formed as a result of the ionizations have sufficient energy, they give rise to further excitations and ionizations. In this way tracks of excited states, positive ions, and electrons are formed. The spatial distribution of the species initially formed in the track will change in time owing to diffusion; the charged species will also drift in each other's Coulomb field. In nonpolar systems the range of the Coulomb forces is very large (30 nm) and neutralization of the oppositely charged species in the track is a dominant process, which in turn leads to formation of excited molecules that generally decompose into reactive fragments. In polar liquids, like water, neutralization is less prevalent and a relatively large fraction of the charged species escapes from the Coulombic attraction. The transient species formed may react with one another and with molecules of the medium, either solvent molecules or solute molecules. The probability of the occurrence of these reactions depends on the initial spatial distribution of the reactive species in the track. The present state of the theory of the kinetics of the nonhomogeneous processes in tracks of high-energy charged particles, which relates the initial spatial distribution of the transient species in the track to the various experimental observables, will be discussed.

A study of a disintegration produced by a particle of energy ~20 000 GeV

1954 ◽  
Vol 221 (1146) ◽  
pp. 367-383 ◽  
Keyword(s):  
Charged Particle ◽  
Large Fraction ◽  
Charged Particles ◽  
High Energy ◽  
Interaction Length ◽  
Nuclear Disintegration ◽  
A Value ◽  
Different Types ◽  
Nuclear Interactions

A detailed investigation has been made of a nuclear disintegration produced by a charged particle, almost certainly a proton, of energy ~20 000 GeV. The disintegration, of type 22 + 76 p , was recorded in a stack of plates exposed at ~90 000 ft. The jet of secondary charged particles, and the associated cascade of electrons and photons, can be followed through the emulsion of twenty-two plates. The observations lead to a value 0⋅25 for the ratio of neutral π -particles to charged shower particles produced in the disintegration. If π 0 -mesons are produced in high-energy nuclear interactions with a frequency half that of the charged π -mesons, and if 10% of the shower particles are assumed to be protons, the present results indicate that 40 % of the charged shower particles are other than π -mesons. As there is no evidence for the existence of nucleon pairs, it is reasonable to identify these other particles with the heavy k -particles. The corresponding ratio of the numbers of charged k - to π-mesons, N K ±/ N π ±, is equal to 0⋅80±0·4. The interaction length of the shower particles from the event, measured without distinction between the different types of mesons which may be among them, is shown to be very nearly equal to the value for nucleons. It follows that the k -mesons, which constitute a large fraction of the shower particles, interact strongly with nuclei.

scholarly journals Direct measurement of the 3-dimensional DNA lesion distribution induced by energetic charged particles in a mouse model tissue

2015 ◽  
Vol 112 (40) ◽  
pp. 12396-12401 ◽  
Author(s):  
Johanna Mirsch ◽  
Francesco Tommasino ◽  
Antonia Frohns ◽  
Sandro Conrad ◽  
Marco Durante ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Mouse Model ◽  
Dose Distribution ◽  
Biological Effects ◽  
Charged Particles ◽  
High Energy ◽  
X Rays ◽  
Particle Path ◽  
Modeling Approaches ◽  
Physical Measurements

Charged particles are increasingly used in cancer radiotherapy and contribute significantly to the natural radiation risk. The difference in the biological effects of high-energy charged particles compared with X-rays or γ-rays is determined largely by the spatial distribution of their energy deposition events. Part of the energy is deposited in a densely ionizing manner in the inner part of the track, with the remainder spread out more sparsely over the outer track region. Our knowledge about the dose distribution is derived solely from modeling approaches and physical measurements in inorganic material. Here we exploited the exceptional sensitivity of γH2AX foci technology and quantified the spatial distribution of DNA lesions induced by charged particles in a mouse model tissue. We observed that charged particles damage tissue nonhomogenously, with single cells receiving high doses and many other cells exposed to isolated damage resulting from high-energy secondary electrons. Using calibration experiments, we transformed the 3D lesion distribution into a dose distribution and compared it with predictions from modeling approaches. We obtained a radial dose distribution with sub-micrometer resolution that decreased with increasing distance to the particle path following a 1/r2 dependency. The analysis further revealed the existence of a background dose at larger distances from the particle path arising from overlapping dose deposition events from independent particles. Our study provides, to our knowledge, the first quantification of the spatial dose distribution of charged particles in biologically relevant material, and will serve as a benchmark for biophysical models that predict the biological effects of these particles.

scholarly journals Saturation effects in SIDIS at very forward rapidities

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
E. Iancu ◽  
A. H. Mueller ◽  
D. N. Triantafyllopoulos ◽  
S. Y. Wei
Keyword(s):  
Inelastic Scattering ◽  
Cross Section ◽  
Cross Sections ◽  
Virtual Photon ◽  
Large Fraction ◽  
Quark Distribution ◽  
High Energy ◽  
Longitudinal Momentum ◽  
Black Disk ◽  
Gluon Saturation

Abstract Using the dipole picture for electron-nucleus deep inelastic scattering at small Bjorken x, we study the effects of gluon saturation in the nuclear target on the cross-section for SIDIS (single inclusive hadron, or jet, production). We argue that the sensitivity of this process to gluon saturation can be enhanced by tagging on a hadron (or jet) which carries a large fraction z ≃ 1 of the longitudinal momentum of the virtual photon. This opens the possibility to study gluon saturation in relatively hard processes, where the virtuality Q2 is (much) larger than the target saturation momentum $$ {Q}_s^2 $$ Q s 2 , but such that z(1 − z)Q2 ≲ $$ {Q}_s^2 $$ Q s 2 . Working in the limit z(1 − z)Q2 ≪ $$ {Q}_s^2 $$ Q s 2 , we predict new phenomena which would signal saturation in the SIDIS cross-section. For sufficiently low transverse momenta k⊥ ≪ Qs of the produced particle, the dominant contribution comes from elastic scattering in the black disk limit, which exposes the unintegrated quark distribution in the virtual photon. For larger momenta k⊥ ≳ Qs, inelastic collisions take the leading role. They explore gluon saturation via multiple scattering, leading to a Gaussian distribution in k⊥ centred around Qs. When z(1 − z)Q2 ≪ Q2, this results in a Cronin peak in the nuclear modification factor (the RpA ratio) at moderate values of x. With decreasing x, this peak is washed out by the high-energy evolution and replaced by nuclear suppression (RpA< 1) up to large momenta k⊥ ≫ Qs. Still for z(1 − z)Q2 ≪ $$ {Q}_s^2 $$ Q s 2 , we also compute SIDIS cross-sections integrated over k⊥. We find that both elastic and inelastic scattering are controlled by the black disk limit, so they yield similar contributions, of zeroth order in the QCD coupling.

ENERGY ORDERING EFFECTS IN THE ARRIVAL DIRECTIONS OF ULTRA-HIGH ENERGY COSMIC RAYS MEASURED BY THE PIERRE AUGER OBSERVATORY

2011 ◽  
Vol 20 (supp02) ◽  
pp. 50-56
Author(s):  
◽  
PETER SCHIFFER
Keyword(s):  
Cosmic Rays ◽  
Magnetic Fields ◽  
Charged Particles ◽  
High Energy ◽  
Pierre Auger Observatory ◽  
Ultra High Energy ◽  
High Energy Cosmic Rays ◽  
Ordering Effects ◽  
Arrival Directions

The Pierre Auger Observatory is the world's largest experiment for the measurement of ultra-high energy cosmic rays (UHECRs). These UHECRs are assumed to be to be charged particles, and thus are deflected in cosmic magnetic fields. Recent results of the Pierre Auger Observatory addressing the complex of energy ordering of the UHECRs arrival directions are reviewed in this contribution. So far no significant energy ordering has been observed.

Diffusion Enhancement in Glassy Metals Under Non-Equilibrium Conditions

1995 ◽  
Vol 400 ◽  
Author(s):  
S. Bellini ◽  
G. Mazzone ◽  
A. Montone ◽  
M. Vittori-antisari Enea ◽  
C.R. Casaccia
Keyword(s):  
Free Volume ◽  
Growth Kinetics ◽  
Bulk Diffusion ◽  
High Energy ◽  
First Case ◽  
Diffusion Enhancement ◽  
Glass Crystal ◽  
Kinetics Of ◽  
Crystal Interface ◽  
Diffusion Properties

AbstractThe diffusion properties of a Ni-Zr metallic glass formed at the interface of a bulk diffusion couple have been studied in conditions far from a fully relaxed state. The growth kinetics of the interface film have been enhanced by both plastic deformation and high energy electron irradiation. Different results have been obtained in the two cases, since in the first case the film grows exponentially with time, while in the second case the usual square root dependence on time is observed. This behaviour has been interpreted as a consequence of the annihilation kinetics of the excess free volume introduced in the glass by the above methods. Two different mechanisms of free volume annihilation , namely exchange with a crystal vacancy at the glass-crystal interface and structural relaxation in the bulk glassy phase have been considered to be operative so that the nature of the growth kinetics has been found to depend on the mechanism predominant in each experimental condition.

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