When a positron (an elementary particle of antimatter) annihilates with an electron, all of its mass and kinetic energy is converted to photons. 100% of the mass is converted. Compare that to a tiny fraction of the mass in chemical and even nuclear fuels. When it comes to space travel, any extra unused mass requires vast quantities of fuel and only a miniscule fraction of the total mass is payload. Antimatter fueled propulsion would be a game changer for the payload fraction. Thanks to the grant from the W.M. Keck Foundation, IMR was able to investigate a novel idea to store antimatter for long times. To prevent premature annihilation, positrons (or any antimatter in general) must be confined away from any matter, including air and other gases. This is accomplished with high magnetic and electric fields to force charged particles (positrons or electrons) into cylindrical confinement. More particles require larger fields and quickly limit the stored antimatter mass to 10-12 (a pico) of a picogram. Unless – and that was the novel concept and idea – the properties of metallic electric conductors are be used as Faraday cages to shield the charge of the stored particles from each other.
The general idea was shown to work, but achieved storage times for electrons (which are easier to come by than positrons) remained in the 0.1 second range. More ideas are required to reduce the mass of the metal cages compared to the mass of the stored particles. For further information on the positron trapping research funded by the W.M. Keck Foundation, visit our W.M. Keck Lab page.
A few key publications of this work are indicated below:
- Khamehchi, M., C. Baker, M. Weber, and K. Lynn, “Feasibility of cooling positrons via conduction in conductive micro-tubes,” Physics of Plasmas, 21 (2013).
- Weber, M., B. Riley, C. Baker, and K. Lynn, “Positron beams from small accelerators and status of a novel positron storage project,” Journal of Physics Conference Series, 443, 2081 (2013).
- Verma, A., J. Jennings, R. Johnson, M. Weber, and K. Lynn, “Fabrication of 3D charged particle trap using through-silicon vias etched by deep reactive ion etching,” Journal of Vacuum Science Technology B: Microelectronics and Nanometer Structures, 31, 2001 (2013).
- Narimannezhad, A., C.J. Baker, M.H. Weber, J. Jennings, and K.G. Lynn, “Simulation studies of the behavior of positrons in a microtrap with long aspect ratio,” The European Physical Journal D, 68(11), 351 (2014).
- Narimannezhad, A., J. Jennings, M.H. Weber, and K.G. Lynn, “Pushing the Limits of Bonded Multi-Wafer Stack Heights While Maintaining High Precision Alignment,” Journal of Microelectromechanical Systems, 25(4), 725-736 (2016).
- Lund, K.R., M.H. Weber, K.G. Lynn, J. Jennings, C. Minnal, A. Narimannezhad, R. Rao, and K.A.W. Monster, “Progress towards an intense beam of positrons created by a Van de Graaff accelerator,” Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 412, 71-80 (2017).