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Journal ArticleDOI

First results of electron cooling experiments at LEAR

01 Jun 1989-European Physical Journal A (Springer-Verlag)-Vol. 332, Iss: 2, pp 171-188

AbstractThe first results are presented of electron cooling experiments in the Low-Energy Antiproton Ring (LEAR) at CERN, performed with a proton beam of about 50 and 21 MeV. The number of stored protons ranged from 107 to 3 × 109. Cooling times of the order 1 s and proton drag rates of up to 0.7 MeV/s were obtained. The capture of cooling electrons by protons producing hydrogen atoms was used to derive an effective electron temperature (0.25 eV). From the angular profile of the neutral hydrogen beam an upper limit of 3π mm.mrad could be deduced for the horizontal equilibrium proton-beam emittance. The lowest equilibrium momentum spread was 2 × 105 (FWHM), as derived from the analysis of the longitudinal Schottky signal. This Schottky signal exhibited an unusual behaviour with beam intensity and under certain conditions showed a doublepeak structure which was associated with collective beam noise. For very cold beams transverse instabilities were observed, which resulted in a rapid spill-off of protons and a stabilization at lower intensities. The threshold of these instabilities was raised by heating the proton or the electron beam. The cooling of a bunched proton beam was investigated. The reduction of the proton momentum spread led to bunch lengths of about 2 m, containing 3 × 108 protons.

Topics: Electron cooling (64%), Proton (58%), Beam emittance (57%), Antiproton (57%), Electron capture (57%) more

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Journal ArticleDOI
Abstract: Advances in ion-source, accelerator and beam-cooling technology have made it possible to produce high-quality beams of atomic ions in arbitrary charged states as well as molecular and cluster ions that are internally cold Ion beams of low emittance and narrow momentum spread are obtained in a new generation of ion storage-cooler rings dedicated to atomic and molecular physics The long storage times ( approximately 5

59 citations

Journal ArticleDOI
Abstract: We have performed for the first time precision spectroscopy on a coasting fast7Li+ ion beam in a storage ring. The ion beam moving with 6.4% speed of light was first electron cooled and then merged with two counterpropagating laser beams acting on two different hyperfine transitions sharing a common upper level (λ-system). One laser was frequency locked to thea 3 127J2 hfs frequency component established as a secondary frequency standard at 514 nm. The second laser was tuned over theλ-resonance, which was recorded relative to127J2 hfs components. This experiment is sensitive to the time dilation in fast moving frames and will lead to new limits for the verification of special relatively. The present status of the experiment and perspectives in accuracy are discussed.

17 citations

Book ChapterDOI
Andreas Wolf1
01 Jan 1992
Abstract: In this paper, we shall discuss the effect of laser-stimulated transitions on the rate of radiative electron-ion recombination, considering in particular merged beams of electrons and protons or highly charged ions. We shall present theoretical predictions concerning the spontaneous and stimulated recombination rates and discuss the limitation of the stimulated rate by photoionization. The emphasis in this discussion will be on transitions into Rydberg states, which play an important role especially for recombination involving highly charged ions. Recent experiments demonstrating laser-stimulated recombination in merged electron and proton beams will be reviewed and a perspective of future experiments will be given.

8 citations

Proceedings ArticleDOI
20 Mar 1989
Abstract: The IUCF (Indiana University Cyclotron Facility) 270-keV electron cooling system has demonstrated collection efficiencies of 100% (+0/-2 p.p.m.) operating with a 2-A electron beam (0.4 A/cm/sup 2/). In addition, a very complete set of longitudinal drag rate measurements have been completed. These measurements span rest frame electron-proton velocity differences of over three orders of magnitude and include the region where the average longitudinal electron-proton velocity difference is less than the electron beam longitudinal velocity spread (a region which has not previously been measured). No obvious Schottky signal suppression (evidence of beam crystallization) has been observed for low-intensity cooled proton beams, though many interesting collective phenomena have been observed for high-intensity cooled proton beams. >

7 citations

01 Jan 2006
Abstract: The high density Lead ion beams, needed for LHC, are obtained in the Low Energy Ion Ring (LEIR) at CERN by multi-turn injection followed by electron cooling and stacking. During this injection and stacking phases where the circulating beam is unbunched, diagnostics with Schottky noise are used for probing essential beam parameters, such as tune, momentum spread, emittance and their evolution with time… The hardware facility and first results obtained during the recent commissioning of LEIR are described.

3 citations

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Journal Article
Abstract: Simplified formulae for the capture of low-energy electrons by stationary protons are averaged over Maxwellian and "flattened" Maxwellian electron velocity distributions. The latter distribution is more nearly appropriate for electron beams used in accelerator proton-beam cooling experiments. Flattening increases the capture rate by a factor of about two. Similar formulae for the capture of antiprotons by protons are mentioned.

51 citations

Journal ArticleDOI
M. Bell1, John Chaney1, H. Herr1, F. Krienen1, Poul Møller-Petersen1, G. Petrucci1 
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

50 citations

Proceedings ArticleDOI
01 Jan 1984
Abstract: A conceptual survey and exposition is presented of some fundamendal aspects of fluctuations and coherence, as well as the interplay between the two, in coasting charged‐particle beams—both continuous and bunched—in storage rings. A detailed study is given of the spectral properties of the incoherent phase‐space Schottky fluctuations, their propagation as waves in the beam, and the analytic complex coherent beam electromagnetic response or transfer function. The modification or distortion of these by collective interactions is examined in terms of simple regeneration mechanisms. Collective or coherent forces in the beam–storage‐ring system are described by defining suitable impedance functions or propagators, and a brief discussion of the coherent collective modes and their stability is provided, including a general and rigorous description of the Nyquist stability criterion. The nature of the critical fluctuations near an instability threshold is explored. The concept of Landau damping and its connection with phase‐mixing within the beam is outlined. The important connection between the incoherent fluctuations and the beam response, namely the Fluctuation–Dissipation relation, is revealed. A brief discussion is given of the information degrees of freedom, and effective temperature of the fluctuation signals. Appendices provide a short resume of some general aspects of various interactions in a charged‐particle between‐environment system in a storage ring and a general introduction to kinetic theory as applied to particle beams.

43 citations