Hydrogen molecule - antihydrogen scattering at very low energies

We consider the low-energy scattering of antihydrogen () by the simplest molecule, H₂. This preliminary treatment applies a generalisation of the Kohn variational method to the calculation of total elastic cross section at low energies. The scattering wavefunction calculated by the generalised Kohn method is used to estimate the antiproton annihilation in flight using a delta function pseudo potential introduced in the treatment of antiproton annihilation in H- scattering.     

Electronic stopping power of hydrogen in KCl at the stopping maximum and at very low energies

The electronic energy loss of hydrogen ions in KCl was investigated in a wide energy range. Thin films of KCl were evaporated on an Au/Si substrate. Rutherford Backscattering Spectrometry (RBS) was performed with protons and deuterons at energies from 30 to 400 keV/nucleon. At lower energies experiments were performed by Time-Of-Flight Low energy ion scattering (TOF-LEIS) again with proton and deuteron projectiles. Experimental results are compared to calculated/tabulated values for the electronic energy loss. Whereas at energies beyond the stopping maximum very good agreement is found, at lower ion energies discrepancies between experiment and calculations increase. At very low ion velocities the extrapolated stopping cross section ε predicts vanishing electronic energy loss at energies below 100 eV/nucleon.     

A new technique for measuring sputtering yields at high energies

The use of thin, self-supporting carbon catcher foils allows one to measure sputtering yields in a broad range of materials with high sensitivity. Analyzing the foils with Rutherford forward scattering, we have measured sputtered A1, Si and P surface densities down to 5 × $\text{10}{}^{13}\text{cm}{}^2$ with uncertainties of about 20%.     

新一代钠冷快堆及特高温堆的研发

为解决长远能源的需求,同时避免因气体排放引起温室效应对环境的危害,就必须研发第四代钠冷快堆及特高温堆.同时在现有的现代技术的基础上,介绍了可以改进及更新的技术要点.由于走向真正工艺应用聚变能的道路还远,必须认清21世纪仍然是核裂变能的世纪.     

Electron ionization cross-section calculations for liquid water at high impact energies

Cross-sections for the ionization of liquid water is perhaps the most essential set of data needed for modeling electron transport in biological matter. The complexity of ab initio calculations for any multi-electron target has led to largely heuristic semi-empirical models which take advantage elements of the Bethe, dielectric and binary collision theories. In this work we present various theoretical models for calculating total ionization cross-sections (TICSs) for liquid water over the 10 keV-1 MeV electron energy range. In particular, we extend our recent dielectric model calculations for liquid water to relativistic energies using both the appropriate kinematic corrections and the transverse part. Comparisons are made with widely used atomic and molecular TICS models such as those of Khare and co-workers, Kim-Rudd, Deutsch-Märk, Vriens and Gryzinski. The required dipole oscillator strength was provided by our recent optical-data model which is based on the latest experimental data for liquid water. The TICSs computed by the above models differ by up to 40% from the dielectric results. The best agreement (to within ∼10%) was obtained by Khare’s original model and an approximate form of Gryzinski’s model. In contrast, the binary-encounter-dipole (BED) models of both Kim-Rudd and Khare and co-workers resulted in ∼10-20% higher TICS values, while discrepancies increased to ∼30-40% when their simpler binary-encounter-Bethe (BEB) versions were used. Finally, we discuss to what extent the accuracy of the TICS is indicative of the reliability of the underlying differential cross-sections.     

Finite element analysis of loaded structures at very high temperatures

At very high temperatures loaded metallic structures undergo creep deformations. The generated creep strains are connected with stress relaxations, stress redistributions and/or progressive deformations.In mainly load controlled situations the behaviour of the material can be described by a nonlinear viscous flow law (Norton power law).A stress-deformation analysis of complex structures can be carried out by finite element codes in which the mentioned constitutive equation is implemented. The code PERMAS-VISCOUS was used to analyse the stress state of a notched tension bar and the deformation behaviour of a tube under external pressure undergoing a creep collapse. The relation to experimental findings is also given.     

Fast-beam spectroscopy at tandem energies

The main areas of interest in the field of beam-foil and beam-gas spectroscopy, as far as wavelength and term value information are concerned, are discussed. Typical examples of the work done since the previous topical conference (Laval 1981) are presented.     

Antiproton-nucleus reactions at intermediate energies

Antiproton-induced reactions on nuclei at the beam energies from hundreds Me V up to several Ge V provide an excellent opportunity to study interactions between the antiproton and secondary particles(mesons, baryons and antibaryons) with nucleons. The antiproton projectile is unique in the sense that most of the annihilation particles are relatively slow in the target nucleus frame. Hence, the prehadronic effects do not much influence their interactions with the nucleons of the nuclear residue. Moreover, the particles with momenta less than about 1 Ge V/c are sensitive to nuclear mean field potentials. This paper discusses the microscopic transport calculations of the antiproton-nucleus reactions and is focused on three related problems:(i) antiproton potential determination,(ii) possible formation of strongly bound antiproton-nucleus systems, and(iii) strangeness production.     

Deuteron tunneling at electron-volt energies

We speculate on a new mechanism for deuteron-deuteron fusion reactions at electron-volt energies. Appealing to conservation principles, it is shown that deuteron tunneling leading to fusion is very unlikely to take place between two isolated deuterons. It is argued that in solids, however, tunneling may lead to fusion via a new reaction mechanism which populates energy levels of⁴He, with simultaneous energy transfer to an electron. Predictions of this theory are that d+d+e^– fusion at electron-volt energies in solids should lead to copious production of tritium, protium, energetic electrons, and small quantities of⁴He.     

Integrity assessment of the high temperature engineering test reactor (HTTR) control rod at very high temperatures

The high temperature engineering test reactor (HTTR) is the first high temperature gas-cooled reactor (HTGR) in Japan with a reactor outlet coolant temperature of 950°C at high temperature test operation. The HTTR contains 16 pairs of control rods for which Alloy 800H is chosen of the metallic parts. Because the maximum temperature of the control rods reaches about 900°C at reactor scrams, structural design guideline and design material data on Alloy 800H are needed for the high temperature design. The design guideline for the HTTR control rod is based on ASME Code Case N-47-21. Design material data is also determined and shown in this paper. Under the guideline, temperature and stress analysis was conducted, and it is confirmed that the target life of the control rods of 5 years can be achieved.     

Boron suppression with a gas ionization chamber at very low energies (E < 1 MeV)

Efficient boron suppression for precise ¹⁰Be measurements with AMS is crucial. The performance of ΔE ? E_res gas ionization chambers is also very important for isobar suppression at low beam energies (<1 MeV). A boron suppression of 6–7 orders of magnitude is achievable with the ETH ΔE ? E_res gas ionization in the standard operational mode (readout of ΔE and E_res electrodes). Some physical effects such as pulse height defect or the energy focusing effect within a ΔE section will be discussed, emphasizing ¹⁰Be measurements below 1 MeV. Additionally the potential of silicon nitride membranes as passive energy degraders in front of the detector is demonstrated.     

Charge transfer in collisions of protons with water molecule at high projectile energies and small scattering angles

The electron capture process induced by fast protons impinging upon water has been theoretically studied for very small scattering angles. Singly differential and total cross sections have been calculated for scattering angles ranging from 0 to 0.5 mrad and compared to the existing experimental data. For the sake of comparison, we have also presented the theoretical charge transfer cross sections for proton-helium collisions.     

Electromagnetic phenomena and collider performance at ultrarelativistic energies

The expectation of ultrarelativistic heavy ions in a collider mode (Brookhaven and CERN), necessitates the study of new electromagnetic phenomena during beam crossing. The two dominant modes of beam loss are explored in this paper. These are electron capture following pair production, and excitation of multiple dipole resonances. The expected energy dependence of the capture cross sections are investigated using exact Monte Carlo techniques.     

Total cross-section of chromium at low neutron energies

The total neutron cross-section of chromium has been measured in the range 1.3 × 10^?4 to 30 eV by the transmission method with pulsed neutron time of flight techniques. A theoretical fit was performed giving a value of (3.25 ± 0.15) b for σ_abs at 0.0253 eV.     

Accelerator mass spectrometry of U at low energies

The performance of the compact ETH-TANDY system for accelerator mass spectrometry measurements of ²³⁶U is presented. Despite the low ion energies of around 1.2 MeV we can demonstrate a background level that is comparable to larger facilities. The careful ion-optical design of the high-energy spectrometer leads to a high suppression of neighboring isotopes sufficient to measure samples with isotopic ratios of ²³⁶U/²³⁸U > 10^-11 the ion chamber only, as demonstrated by systematic investigations with different slit settings and time-of-flight measurements. Additionally, a high overall efficiency is achieved due to a high transmission through the accelerator.     

A concept of very high ratio gas compression device

A very high ratio gas compression device based on liquid metal conical implosion is described in this paper, which can reach a compression ratio up to 10^9–12. This device can produce extremely high density, high pressure, and high temperature, thermally equilibrated states by rapid but continuous compression of gaseous materials. The changes in the state parameters (temperature, pressure, density, radiation, line emission, Doppler broadening, dissociation, ionization) of the compressed material can be monitored over a very wide temperature range up to a million Kelvin. Potential applications of the device include many research fields such as chemical molecule property analyses, high density plasma production, high pressure physics, molecular and atomic physics, intermediate density nuclear fusion, sonoluminescence, etc.