The slow positron source at the giessen 65 MeV linac

doi:10.1016/0168-9002(88)90742-5

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Volume 272, Issue 3, November 1988, Pages 626-628

https://doi.org/10.1016/0168-9002(88)90742-5 Get rights and content

Abstract

The Giessen facility to produce slow positrons (TEPOS) with the 65 MeV electron linear accelerator (linac; at 34 MeV, maximum mean current 200 μA) of the University Giessen, Strahlenzentrum, is described. Some parameters like positron beam diameter and intensity are given. The energy spread is analyzed.

References (15)

M. Begemann et al.
Nucl. Instr. and Meth.
(1982)
R.H. Howell et al.
Appl. Phys. Lett.
(1982)
G. Gräff et al.
Appl. Phys.
(1984)
O. Sueoka et al.
Jpn. J. Appl. Phys.
(1985)

There are more references available in the full text version of this article.

Cited by (25)

The SPOT-IL positron beam construction and its use for Doppler Broadening measurement of annealed Cu
2024, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
The construction and successive first operation of a slow positron beam at The Hebrew University of Israel are reported here. The beam follows a traditional design, using a ²²Na source, and a Tungsten moderator. It is designed to allow a combined measurement of Doppler-Broadening (DB), sample conductivity, and sample in-situ cooling, with the flexibility to add more detection options in the future. The beam energy varies between 0.03 keV and 30 keV. The detection system consists of two high-purity Germanium detectors, facing each other, allowing coincidence DB measurements. Event readout is done using a state-of-the-art compact desktop system. The beam has been successfully tested by using it to characterize annealed Copper (Cu) samples. Three samples were measured at various energies (0.5 keV–16.5 keV), one before any treatment and two annealed at 250 °C and 500 °C. The results, fitted using VEPFIT, show consistent behavior with previous measurements.
Atomic physics of positronium with intense slow positron beams
2002, Applied Surface Science
The theory of quantum electrodynamics has presented a complete calculation of the energy levels of positronium (Ps, e⁺e⁻) up to the order R_∞α⁴. The annihilation rates for para-Ps $(1^{1} S_{0})$ and ortho-Ps $(1^{1} S_{1})$ are completely known up to the order R_∞α⁵ and R_∞α⁶, respectively. The present experimental uncertainty for spectroscopic results is 5–100 times larger than the theoretical uncertainty. For the annihilation rates the experimental situation is even worse. The theoretical predictions have presently reached a level of precision which is a challenge to experimentalists! The experimental uncertainty for the fine- and hyperfine transitions in the Ps atom is determined by the natural line width. An improvement is only possible with better statistics, i.e. higher positron intensities. For the annihilation rate of ortho-Ps there exist controversial measurements. Here completely new experiments are necessary which differ from the old measurements by possible systematic errors. All new proposals need high positron intensities which can be conveniently produced by bremsstrahlung and pair conversion in the beam dump of medium energy electron accelerators.
Antihydrogen beam generation using storage rings
1996, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
The scheme of antihydrogen beam generation is proposed. Two storage rings should be used for effective generation of antihydrogen - an antiproton ring and a small additional one for storing and cooling of positrons. This scheme has advantages compared with those discussed earlier due to the use of a longitudinal magnetic field as the focusing system of the positron ring with the positron source immersed in this field. The electron cooling of positrons is an essential part of the project. The Low Energy Antiproton Ring (LEAR) at CERN is chosen as the basic machine for idea demonstration and all the numerical applications are made for it.
The rate of antihydrogen generation is limited in the case discussed here by the positron source intensity. The simplest version of this scheme permits one to achieve a rate of about 3 × 10⁴ fast (50 MeV) atoms/s and 30 slow (0.5 MeV) ones. Simultaneously such a scheme is a generator of orthopositronium with a productivity of about 2 × 10⁴ and 35 “atoms”/s, correspondingly.
The particle dynamics in the positron storage ring are considered.
Multiple and inner-shell ionization by positron and electron impact
1995, Nuclear Inst. and Methods in Physics Research, B
Recent results for the K- and L-shell ionization of silver and gold, respectively, and the multiple ionization of argon, krypton, and xenon atoms by positron and electron impact will be discussed. The measured cross section ratios for triple relative to single ionization by positron impact decrease more rapidly towards threshold compared to electron impact. This behavior is similar compared to results obtained for the inner shell ionization of silver and gold, and attributed to the acceleration or deceleration which incident electrons or positrons, respectively, undergo in the target nuclear field.
Characteristic and non-characteristic X-ray emission by lepton impact
1994, Nuclear Inst. and Methods in Physics Research, B
Recent progress of characteristic and non-characteristic X-ray emission in collisions of leptons (electrons, positrons) with target atoms is reviewed. We discuss, in particular, i) the differences between electron and positron impact in the ionization of inner atomic shells, ii) the two-photon bremsstrahlung emitted in collisions of electrons with heavy atoms, and iii) the role played by stimulated emission and absorption of photons during electron collisions in a strong laser field.
Recent experiments at the Giessen slow positron source TEPOS
1993, Nuclear Inst. and Methods in Physics Research, B
Recent results for the K- and L-shell ionization of silver and gold, respectively, by positron and electron impact and for the energy loss of 6–20 keV positrons in thin foils obtained at the Giessen slow positron source TEPOS will be discussed. The measured cross section for inner-shell ionization by positron impact decreases more rapidly towards threshold compared to electron impact. This behaviour is confirmed by theoretical calculations performed in the plane wave Born approximation which include an electron exchange term and take the deceleration or acceleration of the incident positron or electron, respectively, in the target nuclear field into account.

View all citing articles on Scopus

View full text

The slow positron source at the giessen 65 MeV linac

Abstract

Nucl. Instr. and Meth.

Appl. Phys. Lett.

Appl. Phys.

Jpn. J. Appl. Phys.