The Stuttgart positron beam, its performance and recent experiments

Bauer, Wolfgang; Briggmann, J.; Carstanjen, H. D.; Connell, S. H.; Decker, W.; Diehl, J.; Maier, K.; Major, J.; Schaefer, H.‐E.; Seeger, A.; Stoll, Hermann; Widmann, E.

doi:10.1016/0168-583x(90)90372-2

Cited by 25 publications

(12 citation statements)

References 12 publications

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“…A series of experiments has searched for such resonances in collisions of positron beams with low-Z solid state targets. 9 No resonance has been found in elastic Bhabha scattering [17,18] at a level of about 0.1% enhancement of the cross section. This translates into a bound for the decay width (assuming J = 1 and no competing decay channels) F~+~-< 1.10 .3 eV.…”

Section: Resonant Bhabha Scatteringmentioning

confidence: 92%

Can extended objects explain the GSI e+ e? lines?

Stein

Graf

Reinhardt

et al. 1991

Z. Physik A - Hadrons and Nuclei

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The anomalous electron-positron coincidences observed in heavy-ion collisions have been interpreted as signal for the pair decay of hitherto unknown neutral objects with masses around 1.8 MeV. We discuss the decay modes of such extended composite particles when they are bound to a nucleus. In particular we investigate the angular correlation of the emitted pair and the competing single-photon decay channel. We confront the particle hypothesis with recent negative results from experiments searching for resonances in Bhabha scattering. The induced pair decay of a metastable 1 § § state in secondary collisions with target atoms is discussed as a possible explanation. PACS: 14.80.Pb; 12.90. +b; 23.20.Nx This is the characteristics of a two-body decay of a (slowly moving) particle-like object X~ § +e-with mass in the 1.8 MeV region. This has led to a large diversity of models and speculations on the nature of the object X ~ [9]. Meanwhile the situation has become even more complex since several line structures have been found which do not all confirm with the two-body decay scenario [10,11].In this paper we will briefly summarize the experimental situation (Sect. 2) and then concentrate on a particular model for a composite X ~ particle [12,13] which was devised to give a comprehensive description of the data (Sect. 3). In Sect. 4 we investigate the decay modes of X ~ bound to a nucleus. Section 5 confronts the particle hypothesis with recent data from Bhabha scattering experiments.

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Section: Resonant Bhabha Scatteringmentioning

confidence: 92%

Can extended objects explain the GSI e+ e? lines?

Stein

Graf

Reinhardt

et al. 1991

Z. Physik A - Hadrons and Nuclei

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“…Immediately after the correlated e § e-pairs were observed, several laboratories started a search for corresponding resonances in the elastic e + e-(Bhabha) scattering in the energy region of interest [9][10][11][12][13][14][15][16][17]. In an early experiment at the Stuttgart pelletron [11], at = 1.83 MeV a structure on the 5 ~-level was found with a width of ~8 keV (FWHM in the e+e-c.m, system), which fitted the Compton profile of the bound electrons of the Be target used in this experiment.…”

Section: Introductionmentioning

confidence: 99%

Limits for two-photon ande + e ? decay widths of positron-electron scattering resonances for?s=1.78 to 1.92 MeV

Widmann

Bauer

Connell

et al. 1991

Z. Physik A - Hadrons and Nuclei

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Motivated by the observation of energy-and momentumcorrelated e § e -pairs in heavy ion collisions, a search for resonances in e + e-scattering at the corresponding energies has been made. The e + e-decay channel is analyzed in a time window from ~ 10 -13 s to ~ 10 -11 s with a set-up optimized for low-background detection of delayed e + e-decays. The two-photon decay channel of a hypothetical resonance is investigated by measuring the two-photon annihilation-in-flight excitation function.New upper limits for the partial e + e-decay width Fee of a few meV are derived for total centre-of-mass energies ]/~ between 1.78 and 1.92 MeV, taking into account the dilepton as well as the two-photon decay of a neutral resonance.

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“…Actually, high-energy positron beams generated by electrostatic accelerators have been applied for PALS in materials at high temperatures [2,3]. A normal conducting accelerator has also been developed for PALS [4].…”

mentioning

confidence: 99%

Design of a liquidless superconducting accelerator for positron annihilation lifetime spectroscopy

Oshima

Kuroda

et al. 2007

Phys. Status Solidi (c)

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A design of a superconducting accelerator for a pulsed positron beam of ~1 MeV for positron annihilation lifetime spectroscopy is proposed. The total system can be extremely small with an application of superconducting technology. Both a miniaturization and easy maintenance of the accelerator can be achieved by usage of a small liquidless refrigerator for cooling of a superconducting RF cavity. Moreover, the operation duty cycle of the superconducting cavity is ~100% which is much larger than that of a normal conducting one. The required RF power to drive the system is ~10 W, therefore a large-size klystron is not necessary. The designed system including a slow positron source is small (~2 m 3 ) enough to be used in a general laboratory.1 Introduction Positron annihilation lifetime spectroscopy (PALS) is the unique method to investigate microscopic characteristic of materials [1]. For PALS, two methods are commonly used to supply positrons in specimens. One is usage of fast beta + rays emitted from radioisotopes (RIs). The RI sealed with thin films is sandwiched by two pieces of specimens during the PALS measurment. The other method is usage of a pulsed slow positron beam. In this case, a specimen has to be mounted in the vacuum. Applying of PALS to materials under extreme conditions (i.e., high temperature, high pressure, and high stress) is difficult with these two methods. The sealed RI might be destroyed under such extreme conditions in the former case and we have to solve a troublesome task that the extreme conditions have to be kept in the vacuum in the later case.PALS for materials under extreme conditions in atmosphere become possible with a high energy positron beam (~1 MeV), because higher energy positrons can pass through the vacuum window of a beamline. Actually, high-energy positron beams generated by electrostatic accelerators have been applied for PALS in materials at high temperatures [2,3]. A normal conducting accelerator has also been developed for PALS [4]. However, all the systems including their controllers so far developed are too huge to be used in a general laboratory.We propose a small accelerator system for high energy (~1 MeV) PALS, in which a superconducting accelerator is used. The overall system can be made extremely small (~2 m 3 ). Both a miniaturization and easy maintenance of the accelerator can be achieved when the superconducting cavity is cooled with a small liquidless refrigerator. To our knowledge, this is the first time a superconducting accelerators is cooled only by a liquidless refrigerator. In this paper, we discuss a design of a superconducting accelerator which is specially optimized for PALS.

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The Stuttgart positron beam, its performance and recent experiments

Cited by 25 publications

References 12 publications

Can extended objects explain the GSI e+ e? lines?

Can extended objects explain the GSI e+ e? lines?

Limits for two-photon ande + e ? decay widths of positron-electron scattering resonances for?s=1.78 to 1.92 MeV

Design of a liquidless superconducting accelerator for positron annihilation lifetime spectroscopy

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