First results of electron cooling experiments at LEAR
TL;DR: In this paper, the 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.
Abstract: The 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.
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TL;DR: A method based on the state space representation in the frequency domain to overcome the fine resolution limit of two closely spaced harmonics is proposed and greatly reduced the computational cost while still retaining superb accuracy.
Abstract: Nuclear mass measurements by means of Schottky mass spectrometry critically rely on an accurate determination of revolution frequencies of the circulating ions in a storage ring. Such a harmonic retrieval problem is conventionally tackled via the periodogram of the Schottky data, where the ion peaks are identified and their spectral locations are obtained by fittings. However, the discrete frequency grid of the periodogram has unfortunately hampered a fine resolution of two closely spaced harmonics. We thereby propose a method based on the state space representation in the frequency domain to overcome this limit. Moreover, its frequency-selective merit has allowed the method to focus only on a narrow band and thus greatly reduced the computational cost while still retaining superb accuracy. With the real Schottky data from an isochronous-Schottky beam time at the experimental cooler-storage ring in Lanzhou, the accuracy of the retrieved harmonics is demonstrated to be around 1 ppm, as limited by the anisochronism effect of the ion optics.
3 citations
CERN1
TL;DR: In this article, the authors discussed the motivation of using electron cooling in low-energy antiproton storage rings and the expected cooling performance, concerning the equilibrium beam properties, the recombination between cooling electrons and cooled protons, and the deceleartion of acceleration of protons by friction in the electron beam.
Abstract: The motivation of using electron cooling in low-energy antiproton storage rings and the expected cooling performance are discussed. Results obtained recently, during the first operation of electron cooling in LEAR at CERN with a 50 MeV proton beam, are summarized, concerning in particular the equilibrium beam properties, the recombination between cooling electrons and cooled protons, and the deceleartion of acceleration of protons by friction in the electron beam. Conclusions are drawn for the formation of antihydrogen with the cooled antiproton beam, and for the deceleration of antiprotons to energies close to or below 1 MeV.
2 citations
Cites background from "First results of electron cooling e..."
...In fact, the equilibrium momentum spread obtained by electron cooling is smaller than this critical value and must be determined [ 30 ] from a more complicated analysis of the noise spectrum, in which the electromagnetic interaction between the stored particles [32] is taken into account....
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...The detailed results of this run will be presented elsewhere [ 30 ]....
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Posted Content•
TL;DR: In this paper, the formulae relevant for the linear optics design of Synchrotrons are derived systematically from first principles, a straightforward exercise in Hamiltonian Dynamics, and the relevant "Use Cases" are then captured for a streamlined approach.
Abstract: The formulae relevant for the Linear Optics design of Synchrotrons are derived systematically from first principles, a straightforward exercise in Hamiltonian Dynamics. Equipped with these, the relevant "Use Cases" are then captured for a streamlined approach. This will enable professionals -- Software Engineers -- to efficiently prototype & architect a CAD Tool for ditto; something which has been available to Mechanical Engineers since the mid-1960s.
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Journal Article•
TL;DR: Simplified formulae for the capture of low-energy electrons by stationary protons are averaged over Maxwellian and "flattened" Maxwellian electron velocity distributions as discussed by the authors, which is more nearly appropriate for electron beams used in accelerator proton-beam cooling experiments.
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
CERN1
TL;DR: In this paper, a general description of the CERN ICE electron cooling experiment is given, and the storage ring and the design and realisation of the cooling apparatus (electron gun and collector, the vacuum system, the magnetic system, beam diagnostics, high voltage stabilisation) are discussed.
50 citations
01 Jan 1984
TL;DR: In this paper, 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 in storage rings.
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.
44 citations