Speaker
Haruhiko Saitoh
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/O4.406.pdf
Overview of the status of the PAX/APEX pair plasma project
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H. Saitoh , U. Hergenhahn , J. Horn-Stanja , S. Nißl , T. Sunn Pedersen , E.V. Stenson , M.
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Dickmann , C. Hugenschmidt , M. Singer , M.R. Stoneking , J.R. Danielson , C.M. Surko
1
Max-Planck Institute for Plasma Physics, Garching and Greifswald, Germany
2
The University of Tokyo, Kashiwa, Japan
3
Technische Universität München, Garching, Germany
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Ernst-Moritz-Arndt-Universität, Greifswald, Germany
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Lawrence University, Appleton, USA
6
University of California, San Diego, USA
By combining recent progress in the fields of toroidal non-neutral plasmas and antimatter
physics, we aim to create magnetically-confined electron-positron pair plasmas [1] in a dipole
magnetic configuration [2]. Experimental verification of the pair plasma properties, such as
remarkable stability [3] and wave propagation characteristics, is the final goal of the project.
Ultimately, intense slow positrons from NEPOMUC (NEutron induced POsitron source
MUniCh) [4] will be accumulated in PAX (Positron Accumulator eXperiment) by using the
so-called buffer gas technique [5], and then transported to and confined in the levitated dipole
trap APEX (A Positron Electron eXperiment) together with an equal number of electrons. Our
key challenges include the accumulation of a large number of positrons in PAX, highly
efficient transport of positrons from the NEPOMUC beamline into the closed dipole field
lines of APEX, and stable and simultaneous trapping of positrons and electrons as plasmas
therein. Based on beam characterization [6] and numerical orbit analysis, we have realized
essentially lossless injection of positrons into a prototype dipole field trap created by a
permanent magnet. After injection, we observed more than 1 s of long trapping of positrons in
the dipole magnetic field. This was realized by carefully eliminating the asymmetry of the
electric fields in the system and reducing the loss channel of positrons toward the magnet
poles. Based on these initial results in the prototype dipole trap [7], we are conducting design
and construction studies for a buffer gas type positron accumulator and a superconducting
levitated dipole configuration for pair plasma confinement. This work is supported by the
European Research Council (T. Sunn Pedersen, ERC-2016-ADG No.741322).
[1] T. Sunn Pedersen et al., New J. Phys. 14, 035010 (2012). [2] U. Hergenhahn et al., AIP Conf. Procs. 1928,
020004 (2018). [3] P. Helander, Phys. Rev. Lett. 113, 135003 (2014). [4] C. Hugenschmidt et al., New J. Phys.
14, 055027 (2012). [5] J.R. Danielson et al., Rev. Mod. Phys. 87, 247 (2015). [6] J. Stanja et al., Nucl. Instr.
Meth. Phys. Res. A 827, 52 (2016). [7] H. Saitoh et al., New J. Phys. 17, 103038 (2015).
