Particle Accelerators
When we think of particle accelerators, we most likely think of huge facilities such as SLAC (the Stanford Linear Accelerator Center) or the LHC (Large Hadron Collider) in Europe. SLAC is capable of accelerating electrons up to energies of 50 GeV in its 2 mile length; for comparison, electrons at room temperature have energies of about 0.03 eV. The LHC is now capable of accelerating electrons up to 6.5 TeV in its 17-mile circumference.
Accelerators also exist that you can fit in a box. When you don't need GeV or TeV energies, but rather just MeV, you can use an accelerator less than a meter in length. These devices are often used to generate X-rays in medical x-ray machines. We are interested in the science of the radiation belts, which are populated by electrons of energies up to tens of MeV. Can we learn about the radiation belts using these accelerators? |
"Active" experiments refer to those where we modify the environment we wish to study, and then observe the response of the environment. Example experiments include the HAARP facility in Alaska, which heats the lower ionosphere while scientists observe the ionosphere's response. In active release experiments, dust or other particulates are deposited in the upper atmosphere by a rocket, and the evolution of the dust cloud is observed. These active experiments are much more rare than passive observational experiments. An accelerator in space would provide a unique active experiment, and the first ever injection of relativistic electrons into the space environment.
Our Work
In collaboration with SRI International, SLAC, and Los Alamos National Laboratory (LANL), we are currently investigating the feasibility of putting a compact linear accelerator in space to actively probe the near-Earth space environment. Such an experiment could address a number of science topics, including i) tracing the Earth's magnetic field lines during geomagnetic storms, to understand how the field reconfigures itself; ii) studying wave-particle interactions in the radiation belts using defined beams of electrons; and iii) investigating the atmospheric interaction during radiation belt electron precipitation. We have undertaken modeling of the beam stability, propagation, and interaction with the atmosphere, and SLAC is developing designs for an instrument that could fly in space.
References
- Sanchez, E. R., A. T. Powis, I. D. Kaganovich, R. Marshall, P. Porazik, J. Johnson, M. Greklek-Mckeon, K. S. Amin, D. Shaw, and M. Nicolls (2019), Relativistic Particle Beams as a Resource to Solve Outstanding Problems in Space Physics, Front. Astron. Space Sci, 6, 71, doi: 10.3389/fspas.2019.00071.
- Marshall, R. A., W. Xu, A. Kero, R. Kabirzadeh, and E. Sanchez (2019), Atmospheric Effects of a Relativistic Electron Beam Injected From Above: Chemistry, Electrodynamics, and Radio Scattering. Front. Astron. Space Sci. 6:6. doi: 10.3389/fspas.2019.00006.
- Marshall, R. A., M. Nicolls, E. Sanchez, N. G. Lehtinen, and J. Neilson (2014), Diagnostics of an artificial relativistic electron beam interacting with the atmosphere, J. Geophys. Res. Space Physics, 119, doi:10.1002/2014JA020427.