Antiproton stopping at low energies: confirmation of velocity-proportional stopping power

The stopping power for antiprotons in various solid targets has been measured in the low-energy range of 1-100 keV. In agreement with most models, in particular free-electron gas models, the stopping power is found to be proportional to the projectile velocity below the stopping-power maximum. Although a stopping power proportional to velocity has also been observed for protons, the interpretation of such measurements is difficult due to the presence of charge exchange processes. Hence, the present measurements constitute the first unambiguous support for a velocity-proportional stopping power due to target excitations by a pointlike projectile.     

Kinetic Study on Channelling of Protons in Metallic Carbon Nanotubes

Based on the kinetic model and the dielectric response theory, a theoretical model is put forward to describe the transport of protons along nanotube axes. With the introduction of electron band structure for different nanotubes like zigzag and armchair nanotubes of metallic properties, the collective excitation of electrons on the cylinders induced by the incident ions is studied, showing several distinct peaks in the curves of the energy loss function. Furthermore, the stopping power and the self-energy are calculated as functions of ion velocities, especially taking into account the influence of damping coefficients. It is conceivable from the results that, in the kinetic formulation, plasmon excitation plays a major role in the stopping. And as the damping increases, the peaks of the stopping power shift to the lower velocities, with the broadening of the plasmon resonance.     

Stopping Power of Charged Particles I

The stopping power of charged particles is determined in the random phase approximation using Lenard Balescu type collision integrals. The stopping power is closely related to other single particle properties such as self energy and quasi particle life time. In this part I, numerical evaluations are given for equal masses (of test and target particles).     

Using Relativistic Kinematics to Generalize the Series Solution of Bethe Stopping Power Obtained from the Laplace–Adomian Decomposition Method

JETP Letters - One widely used expression of electronic stopping power is the Bethe stopping power, which is used in many applications such as radiation dosimetry. Various studies have presented...     

The channeled stopping powers of Boron ions and range calculations in Si

An analytical fitting expression is obtained for the channeled stopping power of B ions in crystalline silicon. Ions incident in the Si 〈100〉 direction at energies from 50 keV/amu to 900 keV/amu are considered. The mean projected ranges of ions have been determined within the framework of the transport theory formalism where the fitting relation obtained for the stopping power was used. For this purpose, a first order ordinary differential equation including second order stopping coefficients is solved numerically by usingFehlberg fourth-fifth order Runge-Kutta method. By using the results for the channeled ion ranges, a transformation relation is proposed for the conversion of channeled/random ion ranges for the ion target system under consideration. The obtained results are compared with widely used standard programs such as Crystal-TRIM, SRIM and PRAL and our program applied to crystalline targets is in good agreement with Crystal-TRIM.     

Z31 effect on the stopping powers of several metallic elements for 28.8 MeV alpha particles: Deviations of experimental data from theories

Stopping powers of several metallic elements for 28.8 MeV alpha particles have been measured. One fourth of the stopping power for alpha particles is larger than the stopping power for protons of the same velocity. But the differences do not agree with Z³₁ correction theories.     

Development of an electronic stopping power model based on deep learning and its application in ion range prediction

Deep learning algorithm emerges as a new method to take the raw features from large dataset and mine their deep implicit relations, which is promising for solving traditional physical challenges. A particularly intricate and difficult challenge is the energy loss mechanism of energetic ions in solid, where accurate prediction of stopping power is a long-time problem. In this work, we develop a deep-learning-based stopping power model with high overall accuracy, and overcome the long-standing deficiency of the existing classical models by improving the predictive accuracy of stopping power for ultra-heavy ion with low energy, and the corresponding projected range. This electronic stopping power model, based on deep learning algorithm, could be hopefully applied for the study of ion-solid interaction mechanism and enormous relevant applications.     

Stopping of Heavy Ions in Magnetized Strongly Coupled Plasmas: High‐Velocity Limit

The energy loss of a heavy ion moving in a magnetized strongly coupled electron plasma is considered within the linear response treatment and in high‐velocity regime. The analytical expressions for the stopping power have been found for the arbitrary ion incidence angle. The obtained general expression for the stopping power is analyzed for the ion which moves parallel or perpendicular to the magnetic field. It is found that in general the magnetic field and the Coulomb coupling reduce the stopping power as well as the dynamical screening length at high velocities. The influence of the magnetic field and the Coulomb coupling on the high‐velocity stopping power is discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the use of averaging stopping power of recoiled nuclei for determining maximum neutron energy of 241Am–Be by superheated drop detectors

The average stopping power of the recoiled nuclei generated by neutron elastic interactions with the Freon-12 drops in a superheated drop detector has been used to determine the maximum neutron energy of the ²⁴¹Am–Be source. In an elastic interaction of neutrons with the Freon-12 liquid, the nuclei of ¹²C, ¹⁹F and ³⁵Cl with different values of stopping power are scattered. The stopping power of these scattered nuclei corresponding to the energy transferred to them through the head-on collision was extracted from the SRIM code. The stopping power values were weighted by considering the neutron–nucleus elastic scattering cross section and the number of each nucleus in the Freon-12 molecule and the average stopping power was calculated from known neutron energy.The maximum energy of the ²⁴¹Am–Be neutron source was estimated as 10.9 ± 3.0 MeV. The consistency between the determined energy and the other reported values confirms the validity of using the average stopping power in the superheated drop detectors. The average stopping power was also used to determine the threshold neutron energy as a function of external applied pressure at different temperatures. Knowing the threshold neutron energy as function of applied pressure, can be used in pressure scanning method for neutron spectrometry by superheated drop detectors.     

Stopping power contribution due to target and projectile excitation/ionization: a comparative study

A comparative study of stopping power codes for different ions in compounds has been made by comparing the computed stopping power values using different codes with the corresponding experimental data. Two computer codes, semiempirical SRIM2006.02 and theoretical CasP3.2 have been used to evaluate and compare the stopping powers of different compounds for protons (125 KeV), helium (500 KeV) and lithium ion (175 KeV) projectiles. The energy behaviour of stopping power of various compounds for helium ion in the energy range (0.3–2.0 MeV) has been studied. The merits and demerits of the adopted formulations are highlighted. It has been observed that the calculation based on SRIM2006.02 provides the best agreement with the experimental data as compared to CasP3.2 code. The stopping power contribution due to target and projectile excitation/ionization at low energies has been evaluated and discussed with reference to CasP3.2 code. From these comparative studies it has been concluded that the target and projectile excitation-ionization increases the stopping power (>20%) at lower energies.     

Excitation and fragmentation mechanisms in ion-fullerene collisions

Electronic and vibronic excitations as well as fragmentation mechanisms in high energy ion ( H+, C+, Ar+) fullerene collisions are investigated within a fully microscopic approach, called nonadiabatic quantum molecular dynamics. The total kinetic energy loss of the projectile depends dramatically on ion mass, but, surprisingly, does not depend on the impact velocity for all ions in a certain range. This is in striking contrast to the predictions of the "stopping power" concept of solids, but explains apparently contradicting experimental observations. Signatures for nonstatistical fragmentation mechanisms are predicted.     

Positron scattering by phonons in metals

Processes involved in positron-matter interaction are studied. The stopping power and mean free path are calculated for positrons with an energy of about 1 eV, which are scattered mostly by phonons. The mean free path and range of positrons in tungsten, as well as the stopping power of tungsten, are calculated for positron energies between 0.025 and 10 eV.     

微通道板离子壁垒膜及其对入射离子的阻止作用

给出了三代微光像管中微通道板离子壁垒膜对入射正离子阻止作用的描述,引进了核阻止本领、电子阻止本领和平均射程的概念。结合Tomas-Fermi屏蔽势进行了分析讨论和Monte-Carlo模拟计算,给出Al₂O₃和SiO₂薄膜对不同能量垂直入射时的核、电子阻止的定量结果。得出了Al₂O₃薄膜阻止本领比SiO₂阻止本领高的结论。证实了选用Al₂O₃离子壁垒膜的科学性和可行性。     

Electronic stopping power in LiF from first principles

Using time-dependent density-functional theory we calculate from first principles the rate of energy transfer from a moving proton or antiproton to the electrons of an insulating material, LiF. The behavior of the electronic stopping power versus projectile velocity displays an effective threshold velocity of approximately 0.2 a.u. for the proton, consistent with recent experimental observations, and also for the antiproton. The calculated proton/antiproton stopping-power ratio is approximately 2.4 at velocities slightly above the threshold (v approximately 0.4 a.u.), as compared to the experimental value of 2.1. The projectile energy loss mechanism is observed to be extremely local.     

Influence of electron exchange and correlation on the stopping power for slow ions in metals

The exchange and correlations between free electrons in metals are shown always to increase electronic stopping power for slow ions. The stopping power is expressed analytically for theoretical evaluations. This expression was used to calculate stopping powers for slow protons in Al and Ag. A better agreement with experimental data is noticed.     

Channeling stopping power for high energy ions

Making use of the inelastic scattering function introduced by Ohtsuki, the position dependent stopping power is derived for energetic ions in a channeling condition. We can interprete the Lindhard theory, Esbensen-Golovchenko theory, and Burenkov-Komarov-Kumakhov theory for the channeling stopping power in terms of our method. Our results agree very well with experiment.     

Das elektronische Bremsvermögen von Stickstoff und Sauerstoff für niederenergetische Protonen

The electronic stopping power of molecular oxygen and nitrogen for protons with energies between 1 keV and 30 keV has been measured using a differentially pumped stopping cell. Our results give a surprisingly good confirmation of the Lindhard-Scharff statistical theory which predicts a linear velocity dependence of the electronic stopping power at low projectile energies. Moreover our data are in fair agreement with earlier high energy (E ≧ 20 keV) measurements in other laboratories. The combination of the present measurements with theoretically calculated nuclear stopping powers yields an estimate of the atomic stopping power. This estimate leads to substantially lower atomic stopping powers at low energies compared to values derived from range measurements. This result may have interesting implications on auroral hydrogen emissions.     

Effective stopping charges and stopping power calculations for heavy ions

In this study the model suggested by Sugiyama has been developed and applied for the calculation of the stopping powers for nonrelativistic heavy ions in various target materials. Sugiyama's model has been expanded to low and high energy regions in our work. Analytical expressions are obtained in the modified BB stopping power formula for the effective charge and effective mean excitation energies. In the modified LSS formula, a quasi-molecule criterion has been applied to both the projectiles and the target atoms. Electronic excitation contribution, S _e0, and quasi-molecule contribution, S _ei , to stopping power were found for a wide energy region. It is observed that in intermediate energy region both contributions have maxima. The stopping power due to excitation-ionization in the intermediate and higher energy region is found to be dominant, whereas quasi-molecule contribution is dominant in the lower energy region. The calculated results of stopping power are in good agreement with experimental data for various ions and targets within a few percent in a wide projectile energy range.     

High resolution measurements of energy spectra of protons scattered from silicon crystals in the case of planar channelling

The energy spectrum of backscattered protons in the case of incidence along several planar directions shows a fine structure near the high-energy edge. This structure, an oscillatory dependence of the probability of backscattering vs. depth in the crystal, offers a possibility to study the proton trajectory in the lattice and also to obtain the stopping power of protons near planes in silicon.

Application of a simple model for the proton trajectory yields a stopping power near the planes 4 to 5 times higher than for random incidence. These effects have been observed using primary energies in the range 40–140 keV and for incidence along (110). (111), (100) and (112) planes.