A Positron-Electron eXperiment Collaboration

Matter-antimatter plasma research at IPP:

The APEX collaboration is focused on the creation of confined, low-temperature, long-lived, electron-positron plasma in the laboratory. Doing so will allow us to conduct experiments involving this unique state of matter, in order to test fundamental plasma physics predictions and gain insight into the physics of the early universe.

In contrast to conventional ion-electron plasmas, electron-positron "pair" plasmas consist of charged particles with identical mass. This symmetry results in pair plasmas having certain novel properties, a topic that has been studied theoretically and numerically for decades; experimental studies, however, are just getting started.
The generation of matter-antimatter plasmas in the laboratory is a significant challenge.  To achieve this, we are developing and bringing together techniques from a variety of fields of physics.  Once the different projects we are working on are all brought together, positrons from a world-class source (NEPOMUC) will be accumulated into ever denser bunches in a series of non-neutral plasma traps, then injected along with electrons into either of two toroidal magnetic confinement configurations:


Research topics:

Positron beams & diagnostics

Non-neutral positron plasma accumulation & storage

Injection and trapping in a prototype dipole trap

Pair plasma traps


Selected publications (experiment strategies):

Stoneking, M.; Pedersen, T. S.; Helander, P.; Chen, H.; Hergenhahn, U.; Stenson, E. V.; Fiksel, G.; Linden, J. v. d.; Saitoh, H.; Surko, C. M. et al.; Danielson, J. R.; Hugenschmidt, C.; Horn-Stanja, J.; Mishchenko, A.; Kennedy, D.; Deller, A.; Card, A.; Nißl, S.; Singer, M.; König, S.; Willingale, L.; Peebles, J.; Edwards, M. R.; Chin, K.: A new frontier in laboratory physics: magnetized electron–positron plasmas. Journal of Plasma Physics 86 (6), 155860601 (2020)
Stenson, E. V.; Horn-Stanja, J.; Stoneking, M. R.; Pedersen, T. S.: Debye length and plasma skin depth: two length scales of interest in the creation and diagnosis of laboratory pair plasmas. Journal of Plasma Physics 83 (1), 595830106 (2017)
Pedersen, T. S.; Danielson, J. R.; Hugenschmidz, C.; Marx, G.; Sarasola, X.; Schauer, F.; Schweikhard, L.; Surko, C. M.; Winkler, E.: Plans for the creation and studies of electron-positron plasmas in a stellarator. New Journal of Physics 14, 035010 (13pp) (2012)

Selected publications (theory predictions):

Horn-Stanja, J.; Biancalani, A.; Bottino, A.; Mishchenko, A.: Linear gyrokinetic studies with ORB5 en route to pair plasmas. Journal of Plasma Physics 85 (3), 905850302 (2019)
Kennedy, D.; Mishchenko, A.; Xanthopoulos, P.; Helander, P.; Banon Navarro, A.; Görler, T.: Linear gyrokinetics of electron–positron plasmas in closed field-line systems. Journal of Plasma Physics 86 (2), 905860208 (2020)
Helander, P.: Microstability of Magnetically Confined Electron-Positron Plasmas. Physical Review Letters 113, 135003 (2014)


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