F. Krienen

Electron cooling in ICE at CERN

Abstract A general description is given of the CERN ICE electron cooling experiment. The storage ring and the design and realisation of the cooling apparatus (electron gun and collector, the vacuum system, the magnetic system, the beam diagnostics, the high voltage stabilisation) are discussed. Some typical experimental cooling results are presented, and finally the cooling times are compared with some approximate theoretical estimations.

Digitized spark chambers

Abstract A new nuclear instrument for the detection of ionizing particles is described. The instrument operates in the manner of a spark chamber in which the ionization due to the passage of an ionizing particle is amplified by means of a strong pulsed electric field resulting in an electrical discharge. The instrument here described differs from the conventional spark chamber in the way in which the information is used to record the passage of the ionizing particle. The currents produced during the electrical breakdown of the gas in the chamber are suitably shaped and forced to follow specific current paths which are linked with a magnetic memory system. From thereon the data may be readily available for further processing by conventional means.

Electron cooling experiment at CERN

Abstract Beams of 46 MeV protons have been cooled by means of electrons in the ICE (initial cooling experiment) storage ring. Six two-day runs starting in May 1979 have shown, for proton intensities of up to 3 × 108, a density increase in six dimensional phase space of over a factor of 106, with cooling times in momentum spread and betatron amplitudes of 0.3 and 1.2 s, respectively. The proton beam lifetime was increased by a factor of 40. Measurements of the evolution of momentum spread, beam profile, and neutral atom production rate are in reasonable agreement with theory.

A digitized spark chamber

A wire spark detector is described, which is essentially a coordinate detector with a number of wire planes orientated in two planes. On each wire is threaded a magnetic core of the so-called square loop hysteresis type. A spark in the chamber results in a reversal of the magnetization in the corresponding core. The information concerning an event is stored in a number of switched cores, which can be read out in the usual way by threading additional wires through the cores. An efficiency >90% was measured in a model of the chamber. The spatial resolution was of the order of one wire spacing. (A.G.W.)

Measurement of antiproton lifetime using the ice storage ring

Antiprotons have been stored in the ICE Storage Ring and held for 85h with the help of stochastic cooling. We set a limit of at least 32 h for the antiproton lifetime (in its rest frame).

Dependence of v-nucleus cross sections on the mass number

Abstract High energy v -nucleus cross sections have been compared for Pb, Fe, Al and C as target nuclei, exposed to the CERN v -beam. The events with θ vμ 0 and p μ ⪆ 1 GeV /c have rates in the ratio of the mass number of the nuclei. Also a restricted sample with q 2 ⪅ 0.1 (GeV/ c ) 2 and θ vμ 0 does not reveal a theoretically predicted deviation from A -proportionality, although due to the limited statistical accuracy in this restricted sample an “ A 2 3 - contribution ” of several tenths cannot be excluded either.

Pulsed electrostatic quadrupole focusing for the CERN muon storage ring

Abstract In order to improve the precision in the measurement of the g -factor anomaly a = (g − 2) 2 , it is desirable to have the polarized muons circulating in a uniform magnetic field ( B · ν = 0 ). Vertical focusing of the muons can be done with an electrostatic quadrupole field. Although the required potentials on the electrodes are reasonable (∼40 kV), the combined action of magnetic and electric field considerably enhances the probability of breakdown. This is due to trapped electrons which circulate around the electrodes and ionize the molecules of the rest gas. However, with reasonable vacuum ( −6 torr) the build-up of charge is slow. Therefore a pulsed electrostatic quadrupole field is applied, the field being on during the storage time of the muons, i.e. 1 ms. In this way the system is operational.

The CERN neutrino spark chamber

BS>The design of the CERN neutrino spark chamber was mainly determined by the postulate of maximum flexibility. It consists of modular subunits that can be combined with counters and, if necessary, with absorbers in any suitable way. Some subunits are made of Al and some of brass, Each is the minimum practical size with two outside plates and one high-voltage leading plate in between. Problems presented by the optical system are discussed briefly. Possibilities and limitations of the chambers are illustrated by photographs taken in test runs on an assembly of 19 Al chambers followed by 4 brass chambers (A.G W.)

Test on the conservation of the muonic lepton number

Abstract An investigation has been made on the conservation of the muonic lepton number by using a pure neutrino beam and by measuring the charge ratio of the muons in neutrino interactions. The experiment yields a new upper limit for a possible violation of the muonic lepton number of

Antiproton lifetime measurement in the ice storage ring using a counter technique

Abstract Results are presented of the search for an antiproton decay into an electron and a neutral pion. Using a stacking scheme based on stochastic cooling an average of 7000 antiprotons was accumulated and stored in the ICE ring for 10 days. No experimental evidence for such an antiproton decay was found. The following lower limit for the antiproton lifetime has been established in the antiproton rest frame: τ > BR × 1700 h at 90% confidence level (CL), where BR is the branching ratio for this decay channel.