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The authors investigated the possibility of replacing the conventional photomultiplier tube with a vacuum photodiode as light sensor for gas scintillation counters. This was successfully done for heavy ions in counters where a high light output was available. It is shown that the diode can also be used with a gas scintillation proportional counter measuring low-energy particles if a large light amplification factor exists. Test results with 238U ions at 1.4 MeV/amu, 252Cf fission fragments and 241Am α-particles are presented.

A scintillation drift chamber operated with a gas mixture of 90% Ar + 10% N2 in the range of pressure between 50 and 150 torr is described. The position where a heavy ion transverses the chamber is determined in one dimension from the drift time of ionization electrons measured as the time delay between primary and secondary scintillation flashes; the other dimensions is derived by charge-division techniques from the charge of the electron swarm arriving at the end of the drift space. ΔE signals for particle identification were derived from both the collected charge and the total light amplitude. With 136Xe and 238U ions of 1.4 MeV/amu, position resolution, pulse height and pulse-height resolution were studied systematically. Best resolutions obtained were 0.5 mm and 0.3 mm, respectively, for the two dimensions and 4.7% for ΔE.

A multiplate ionization chamber for absolute photofission cross section measurements with monoenergetic γ radiation is described. Physical, electronic, and mathematical methods for background elimination are presented as well as a procedure to take fission-fragment absorption in the target layers into account. The chamber is tested under conditions typical for the photofission of bismuth.

A noble-gas scintillation counter for heavy ions is described, which was operated with pure argon and xenon at pressures ranging from 50 to 400 torr. The response of the counter to medium-energy 86 Kr and 136 Xe ions (1.4 MeV/amu) was determined. The observed time structure of the scintillation pulses is characterized by fast deexcitations within a few ns and slow components that are delayed up to a few μs; decay times vary considerably with pressure. With xenon, an energy resolution (fwhm) of 2.2% and an instrumental time resolution of 210 ps were obtained for 136 Xe ions. With argon, corresponding values were 2.6% and 350 ps, respectively. The relative pulse heights measured for 136 Xe ions and 241 Am α-particles have confirmed constancy (within 8%) of light output per unitenergy, independent of ionization density.

Better understanding of bremsstrahlung and modern experimental techniques, especially the use of GeLi detectors for the determination of weak γ-impurities, may today allow to make wider use of bremsstrahlung counting in the metrology of radionuclides. Therefore, present theoretical and experimental knowledge of the different types of bremsstrahlung is first briefly reviewed. Then some known or possible applications of bremsstrahlung counting and corrections for bremsstrahlung in other methods are discussed. Finally the 4π β-bremsstrahlung coincidence method for the measurement of pure β-emitters of nuclides decaying by pure electron capture is described and some new experimental results are presented. Conclusions concerning fundamental principles of coincidence counting can be drawn from these results.