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The energy losses of charged particles traversing 30 proportional chambers are measured simultaneously. The relativistic rise of ionization is investigated in several gases. A maximum increase of 45% is observed in a mixture of argon-propane, where Landau theory predicts an increase of 78%. The application of these measurements for particle separation is discussed.

The experimental set-up used to study the π+ absorption in flight by complex nuclei with two outgoing protons is described. The momentum of the incident pion is measured by a magnetic spectrometer, and the momenta of the two outgoing protons by a range array of 48 plastic scintillators, each 2 mm thick. The directions of the particles are measured by film-less spark chambers. An on-line computer system allows a continuous control of the data which are finally recorded on magnetic tape.

We present a high-energy neutron hodoscope where the impact vertex of the neutron is determined by detection of charged particles produced in a converter, with two multiwire proportional chambers. Tests in 19 GeV/ c neutron and 10 GeV/ c proton beams give, for a total neutron efficiency of 6.5%, an accuracy of ±2.2 mm. Of the reconstructed events 96% are found within ±1 cm distance from the true impact point. The efficiency is then six times larger for neutrons than for gamma-rays.

Several methods are discussed, which reduce substantially the number of amplifiers required for the readout of a proportional multiwire chamber. 1. 1. The plane of wires is built as a lumped delay line. The difference in the arrival time of the pulse at the two ends of the line determines the position of the active wire. 2. 2. The wires are connected to a resistive attenuator network The ratio of the pulse heights arriving at the two ends localizes the active wire. 3. 3. The wires can be connected in different subgroups by transformer coupling.

The European Muon Collaboration has built a large magnetic spectrometer system for deep inelastic muon scattering experiments at the CERN SPS muon beam. The general characteristics of the apparatus — composed of a target of either liquid hydrogen or deuterium, or iron plus scintillator, followed by a large magnet with wire chambers before and after it for precise angle and momentum measurement, a muon identifier, large trigger hodoscopes, and hadron identifiers — are explained and each part is described in some detail. The main features of the data-acquisition and apparatus-monitoring systems and of the off-line event reconstruction are given.

A method is proposed for nonphotographic positioning of sparks. In the chamber, the charge from a condenser discharges to ground through the conductive channel produced by the spark. The grounded plate is connected to ground at two opposite points and the current is thus divided between the two different channels, according to their relative impedance, which is a function of spark position. (R.E.U.)