Optical Properties of Cold Dense Electron-Positron Plasmas

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A neutral plasma is a gas composed of equal numbers of particles with positive and negative charges. This project addresses a frontier in plasma physics research in which the two charges, negative electrons and positive positrons, are each other’s antiparticles, with exactly equal masses and opposite charges. The simpler behavior of this type of system will be of great value in the understanding and control of the non-equal mass plasmas required for power generation using future fusion energy technologies. The equal mass electron-positron plasma will be examined under various conditions of density and temperature to verify its predicted greater stability compared to the non-equal mass plasmas. This research will occur at a federally-designated Hispanic Serving Institution and over time will create opportunities for undergraduate, graduate, and postdoctoral training, thus supporting the education and diversity goals of the campus and the Nation.The goal of this exploratory project is to demonstrate the trapping of polarized electron-positron plasmas in cavities of various sizes from 1 mm to 50 micron embedded in a solid such as diamond. Short, 10 nanosecond, bursts of ~107 positrons will be delivered to the cavities through a thin window. The positrons will be repelled by the chemical potential of the solid, and they will attract an equal number of “hot” electrons released during the implantation. A neutral electron-positron plasma will build up in the cavity and rapidly equilibrate at a common temperature. The plasma polarization, temperature, and density will be deduced from the annihilation rate and from plasma oscillations induced by pulsed excitation. Being devoid of the instabilities that come from unequal mass, the equal mass plasma is the ideal system to explore other instabilities that might be associated with cavity geometry or impedance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.