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Journal ArticleDOI

Detailed studies of a high-density polarized hydrogen gas target for storage rings

TL;DR: In this article, a high-density target of polarized atomic hydrogen gas for applications in storage rings was produced by injecting atoms from an atomic beam source into a T-shaped storage cell.
Abstract: A high-density target of polarized atomic hydrogen gas for applications in storage rings was produced by injecting atoms from an atomic beam source into a T-shaped storage cell. The influence of the internal gas target on electron-cooled beams of 27 MeV α-particles and 23 MeV protons in the Heidelberg Test Storage Ring has been studied in detail. Target polarization and target thickness were measured by means of 27 MeV α-particles. For hyperfine states 1 + 2 a target thickness of n = (0.96±0.04) × 1014H→/cm2 was achieved with the cell walls cooled to 100 K. Working with a weak magnetic holding field (≈5 G) the maximum target polarization was PT = 0.84±0.02 when state 1 and PT = 0.46±0.01 when states 1 + 2 were injected. The target polarization was found to be constant over a period of 3 months with a net charge of Q ≈ 100C passing the storage cell.
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Journal ArticleDOI
TL;DR: ANKE as mentioned in this paper is a new experimental facility for the spectroscopy of products from proton-induced reactions on internal targets, which has recently been implemented in the accelerator ring of the cooler synchrotron COSY of the Forschungszentrum Julich (FZ-Julich), Germany.
Abstract: ANKE is a new experimental facility for the spectroscopy of products from proton-induced reactions on internal targets. It has recently been implemented in the accelerator ring of the cooler synchrotron COSY of the Forschungszentrum Julich (FZ-Julich), Germany. The device consists of three dipole magnets, various target installations and dedicated detection systems. It will enable a variety of hadron-physics experiments like meson production in elementary proton–nucleon processes and studies of medium modifications in proton–nucleus interactions.

158 citations

Journal ArticleDOI
TL;DR: In this article, the energy dependence of the total and differential cross sections for excess energies up to 80 MeV by determining the Fermi momentum of the target neutron on an event-by-event basis was extracted.
Abstract: The quasifree $pn\ensuremath{\rightarrow}d\ensuremath{\phi}$ reaction has been studied at the Cooler Synchrotron COSY---J\"ulich, using the internal proton beam incident on a deuterium cluster-jet target and detecting a fast deuteron in coincidence with the ${K}^{+}{K}^{\ensuremath{-}}$ decay of the $\ensuremath{\phi}$ meson. The energy dependence of the total and differential cross sections are extracted for excess energies up to 80 MeV by determining the Fermi momentum of the target neutron on an event-by-event basis. Though these cross sections are consistent with $s$-wave production, the kaon angular distributions show the presence of $p$ waves at quite a low energy. Production on the neutron is found to be stronger than on the proton but not by as much as for the $\ensuremath{\eta}$ meson.

31 citations

Journal ArticleDOI
TL;DR: In this paper, the spin-flip cross-section of a low-energy electron-proton scattering was measured and the measured cross-sections are too small for making spin flip a viable tool in polarizing a stored beam.

27 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed a method for polarising antiprotons in a storage ring by means of a polarised positron beam moving parallel to the anti-antiprotons.
Abstract: We propose a method for polarising antiprotons in a storage ring by means of a polarised positron beam moving parallel to the antiprotons. If the relative velocity is adjusted to v/c ≈ 0.002 the cross-section for spin-flip is as large as about 2 . 1013 barn as shown by new QED calculations of the triple spin cross-sections. Two possibilities for providing a positron source with sufficient flux density are presented. A polarised positron beam with a polarisation of 0.70 and a flux density of approximately 1.5 . 1010 /(mm2 s) appears to be feasible by means of a radioactive 11C dc-source. A more involved proposal is the production of polarised positrons by pair production with circularly polarised photons. It yields a polarisation of 0.76 and requires the injection into a small storage ring. Such polariser sources can be used at low (100MeV) as well as at high (1GeV) energy storage rings providing a time of about one hour for polarisation build-up of about 1010 antiprotons to a polarisation of about 0.18. A comparison with other proposals show a gain in the figure of merit by a factor of about ten.

21 citations

Journal ArticleDOI
TL;DR: In this article, a high degree of dissociation of more than 70% at gas throughputs up to 3 mbar/l/s for both hydrogen and deuterium, corresponding to an atomic flow rate of 1.2×1020−1.
Abstract: A source of highly dissociated, intense, cold hydrogen and deuterium atomic beams to be used as a dissociator in polarized gas targets for storage ring experiments has been developed. This dissociator is based on a plasma source which couples a 2.45 GHz surface wave to the discharge. At the end of the discharge tube a cold atomic beam is formed by means of a cooled nozzle. The entire system has been optimized to obtain a beam with a high atomic fraction and long-term stable reproducible operation. We measured a high degree of dissociation of more than 70% at gas throughputs up to 3 mbar l/s for both hydrogen and deuterium, corresponding to an atomic flow rate of 1.2×1020 s−1. Excellent long-term stability has been achieved. We also studied quantitatively the effect of recombination of atoms on the nozzle surface for various materials.

21 citations

References
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Journal ArticleDOI
TL;DR: In this paper, it was shown that if n alternates rapidly between large positive and large negative values, the stability of both radial and vertical oscillations can be greatly increased compared to conventional accelerators in which n is azimuthally constant and must lie between 0 and 1.

1,034 citations

Journal ArticleDOI
TL;DR: Comprehensive analyses of nucleon-nucleon elastic-scattering data below 1100 MeV laboratory kinetic energy are presented and a resonancelike structure is found to occur in the /sup 1/D/sub 2/, /sup 3/F/sub 3/, /Sup 3/P/ sub 2/-/sup 3-F/ Sub 2/, and /sup 2/H/sub 4/ partial waves.
Abstract: Comprehensive analyses of nucleon-nucleon elastic-scattering data below 1100 MeV laboratory kinetic energy are presented. The data base from which an energy-dependent solution and 22 single-energy solutions are obtained consists of 7223 pp and 5474 np data. A resonancelike structure is found to occur in the $^{1}\mathrm{D}_{2}$, $^{3}\mathrm{F}_{3}$, $^{3}\mathrm{P}_{2}$${\mathrm{\ensuremath{-}}}^{3}$${\mathrm{F}}_{2}$, and $^{3}\mathrm{F}_{4}$${\mathrm{\ensuremath{-}}}^{3}$${\mathrm{H}}_{4}$ partial waves; this behavior is associated with poles in the complex energy plane. The pole positions and residues are obtained by analytic continuation of the ``production'' piece of the T matrix obtained in the energy-dependent solution. The new phases differ somewhat from previously published VPI solutions, especially in I=0 waves above 500 MeV, where np data are very sparse. The partial waves are, however, based upon a significantly larger data base and reflect correspondingly smaller errors. The full data base and solution files can be obtained through a computer scattering analysis interactive dial-in (SAID) system at VPI, which also exists at many institutions around the world and which can be transferred to any site with a suitable computer system. The SAID system can be used to modify solutions, plan experiments, and obtain any of the multitude of predictions which derive from partial-wave analyses of the world data base.

152 citations

Journal ArticleDOI
TL;DR: The Heidelberg heavy ion test storage ring TSR started operation in May 1988 and the first experiments were performed in 1989 as mentioned in this paper, where the lifetime of the ion beams observed in the first experiment can be explained by interactions with the residual gas.
Abstract: The Heidelberg heavy ion test storage ring TSR started operation in May 1988. The lifetimes of the ion beams observed in the first experiments can be explained by interactions with the residual gas. Multiple Coulomb scattering, single Coulomb scattering, electron capture and electron stripping are the relevant processes. Electron cooling of ions as heavy as O 8+ has been observed for the first time. With increasing particle number, the longitudinal Schottky noise spectrum becomes dominated by collective waves for cooled beams, allowing a determination of velocities of sound. After correcting for these coherent distortions fo the Schottky spectrum, the longitudinal beam temperature could be extracted. The observed longitudinal equilibrium beam temperatures increase strongly with the charge of the ions. For a cooled C 6+ beam, temperatures a factor of 120 higher were measured compared to a proton beam with the same particle number. The shrinking of the beam diameter due to electron cooling was observed with detectors which measured the profile of charge-changed ions behind a bending magnet. A strong laser-induced fluorescence was detected when storing metastable 7 Li + ions in the ring. Via the Doppler effect a very accurate measurement of the ion velocity profile could be performed. First attempts to observe laser cooling failed, probably due to heating effects from intrabeam scattering and a coupling between longitudinal and transversal motion in the beam. Several experiments under preparation are outlined.

90 citations

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