H. Herr

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.

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.

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).

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.

Antiproton-proton mass comparison with a radio-frequency mass spectrometer

Abstract The experiment aims at the reduction of the upper limit on a hypothetical CPT violation in the antiproton-proton system. A radio-frequency mass spectrometer (RFMS) has been designed and built to make the comparison of the charge to mass ratios of p and p by measuring the ratios of the cyclotron frequencies of p and H− ions. At present, the RFMS is installed on-line to the LEAR facility at CERN. The resolving power has been found to be close to 3 × 105 and it still could be improved. A decelerating system (RFQ) has been installed in order to decelerate antiprotons from 2 MeV to 200 keV and to match as well as possible the acceptance of the spectrometer. It is presently under test and data taking should take place in 1992.

Experiments on Stochastic Cooling in ICE (Initial Cooling Experiment)

Recent experiments on stochastic cooling have resulted in cooling rates several orders of magnitude higher than obtained previously in the ISR. Two cooling systems reduce betatron oscillations. A third system reduces momentum spread, using the so-called filter method. The favourable signal-to-noise ratio of this method has led to cooling times (e-folding of peak density) of 15 s with 7.107 protons in ICE. Betatron cooling times are longer due to the lower signal-to-noise ratio. Simultaneous cooling in all three planes has yielded lifetimes of about 100 h, a value consistent with losses caused by single scattering on the residual gas. The existing stochastic cooling theory has been confirmed.

The radiofrequency mass spectrometer for the comparison of proton-antiproton masses

The radiofrequency mass spectrometer has been prepared in Orsay, and moved to CERN to be installed on-line with LEAR (PS189). The present and finally expected performances are given.

Resolution limits with cooled beams

Storage rings for intense proton and ion beams are under construction which will work in the low and intermediate energy range, for experiments with internal targets. These machines will have a very good vacuum and will be equipped with efficient cooling devices which will give small beam dimensions and a small momentum spread. Under these conditions intrabeam scattering becomes a dominant effect. Calculations were made to estimate the resulting beam dimensions and momentum spread for different ions and energies.

Measurement of the antiproton inertial mass using a radio-frequency mass spectrometer: Present status

Abstract In order to test CPT invariance theorem, PS189 aims at checking the equality of proton and antiproton masses via the measurement of the ratio of H − and p masses using a radio-frequency mass spectrometer. Recent progress, including a resolving power of 6 × 10 5 , is presented.

Present Status of the Radiofrequency Mass Spectrometer for the Comparison of the Proton-Antiproton Masses (Experiment PS 189)

The principle and the main parameters of the radiofrequency mass spectrometer for the experiment PS 189 (Fig. 1) have already been discussed and described in detail1,2,3. We shall here only recall them very briefly and give the present status of the preparation of the experiment.