[en] This chapter summarizes the experiences with different positron sources and describes experiments which will be possible in the near future. Topics considered include the moderators, fast positron sources (radioactive sources, electron accelerators), the proposed experiments (positron impact ionization, differential cross sections), and future experiments. The measurement of angular resolved and partial cross sections is possible as a result of the increased positron intensity. The most challenging experiment to be done in the future will concern the scattering of positrons on atomic hydrogen

[en] Published in summary form only

[en] Recent experimental results from positron scattering experiments are presented. Partial cross sections which impose more stringent tests on theory than total cross sections are discussed in detail. Astrophysical applications and positronium beams are briefly covered. 58 refs.; 17 figs

[en] Previously the cross sections were measured for positronium formation and single ionization by positron impact for He and H2. With the same apparatus, slightly modified, the single and multiple ionization of xenon is now investigated. The principle of the method is the detection of ion and positron in time correlation which allows the discrimination of positronium formation (whereby the positron vanishes) and the destinction of single, double and triple impact ionization (which lead to different ion flight times from the gas target to the ion detector). By using secondary electrons from the positron moderator, similar measurements were performed on electron impact ionization. By comparing with literature values for electron multiple ionization cross sections, the detection-probability ratios were determined for the differently charged ions

[en] With the crossed beam apparatus the relative impact-ionization cross section of atomic hydrogen by positron impact was measured. A layout of the scattering region is given. The first measurements on the ionization of atomic hydrogen by positron impact are also given

No abstract available

[en] The positron total scattering cross sections for Ne, Ar, Kr and Xe between 1 and 6 eV have been measured using a time-of-flight spectrometer which has a straight beam-line geometry. A comparison with other results shows rather good agreement for neon but serious deviations for the other gases; the present cross section values lie distinctly above the others. (author)

[en] Positrons ionize helium atoms either by charge exchange leading to positronium (Ps) or by impact ionization. From a gas target in form of a long thin tube with longitudinal magnetic guiding and electric extraction fields positrons and ions are extracted, mass separated and detected. Relative cross sections, normalized at high energies to the electron-impact ionization cross section, are obtained for the sum of positronium-formation and impact-ionization cross section by detecting all extracted ions and for the ionization cross section σ_Ion⁺ without Ps formation by detecting only those ions which are time-correlated to a positron. The Ps-formation cross section σ_Ps is then given by the difference of the two measurements. Our results for σ_Ps confirm the measurements made at the University of Texas, Arlington. The three partial cross sections σ_Ps, σ_Ion⁺ and σ_Ion^- (for electron-impact ionization) peak at 35, 95 and 130 eV, respectively and have respective cross section maxima of 0.39, 0.45 and 0.37 x 10^-16 cm². (Auth.)

[en] For positron impact on xenon we have measured the ratios of double-to-single and triple-to-single ionization cross sections, R2 and R3, respectively, and compared them with the corresponding cross section ratios for electron impact. At high projectile energies, at about 600-800 eV, the cross section ratios R2(e⁺) and R2(e^-) merge. At lower projectile energies, the positron ratios lie below the electron ratios. Qualitatively, this agrees with the previous results for He, Ne and Ar. (author)

[en] The problem of measuring the particle projected angle of incidence on the basis of measuring the cluster size, i.e. the number of wires touched by an inclined track, in a proportional chamber is discussed. It is shown that for tracks with large angles of incidence, the space and angular resolution depends in a critical way on the electronics threshold and high voltage setting. With proper operating conditions, the space resolution can be made independent of angle. This means that the resolution perpendicular to the track improves with the cosine of the angle. It is concluded that the projected track angle can be measured directly from the cluster size, with a resolution of typically 10 deg - 20 deg full base width