Positron injection and trapping for positron-electron pair plasma creation

• Applicants: Professor Dr. Christoph Hugenschmidt; Dr. Eve V. Stenson, Ph.D.
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 461996311

"Pair plasmas" consisting of electrons and positrons are uniquely symmetric plasmas in which the negatively and positively charged particles have identical mass (in contrast to the large mass difference between electrons and ions in standard plasmas). After more than four decades of theoretical and computational predictions about their properties, we are finally on the verge of being able to create and study magnetically confined pair plasmas in the laboratory. The results are expected to make significant contributions to our understanding of fundamental plasma physics, with implications for diverse areas, from magnetic confinement for fusion energy to astrophysical systems in which electron-positron plasmas occur naturally. Three key challenges en route to our goal are (i) getting enough positrons at suitable parameters as to be in the plasma (collective behavior) regime, (ii) development of traps with sufficiently long confinement times for those positrons and an equal number of electrons, and (iii) transfer of the charged particles into the traps (which in the case of positrons must be highly efficient).Support from the DFG of our proposal "Positron Injection into a Magnetic Dipole Field for the Study of an Electron-Positron Plasma" has enabled essential progress with respect to all three of those challenges. Highlights have included lossless injection of low-energy positrons into a dipole magnetic field, long confinement (in excess of a second) of positrons in that field, injection of positrons into a preexisting electron space charge, and sophisticated simulations that mimic past experiments and guide the design of future ones. Thanks to these results, work has been able to move forward on the development (in parallel, funded by other sources) of next-generation traps capable of confining larger numbers of positrons and electrons. In our current proposal, we explain how we would like to apply our successes from our last proposal to these new traps, thereby further developing these methods and bringing us to our goal of pair plasmas within the next few years.

• DFG Programme: Research Grants
• International Connection: USA
• Cooperation Partner: Professor Clifford Surko