Tracking E X B Electrons

By Eric November 12, 2016 BNL

This project is part of the G-2 experiment*. Sometimes atoms in the G-2 ring vacuum are ionized and the charged particles travel around the electrodes in the direction perpendicular to both the electric and magnetic fields (the E X B direction) and eventually enter the vacuum pipes containing the high-voltage leads.

(The note and presentation below were written for the members of the G-2 experiment. Therefore, there is little background in the note and jargon may be used.)

GitHub code: https://github.com/EmptyBucket9000/BNL_EXB_Tracking
Technical note: charged_particle_tracking_near_high-voltage_leads_in_vacuum_pipe.pdf
Power point presentation: electron_tracking_results_in_high-voltage_vacuum_pipe.pdf

There are vacuum pipes that contain 4 high-voltage leads, 2 positive and 2 negative, that power the electrodes in the storage ring. The leads extend towards the center of the ring, the magnetic field rapidly decreases over this distance. While the magnetic field is strong enough, the charged particles are trapped in an oscillating motion, unable to either escape to the outer pipe, the ground, or fall into a high-voltage lead.

The code was written to follow the charged particles through the pipe until they escape to ground or fall into a lead. The final goal was to find at what magnetic field none of the charged particles are still in the pipe.

This is important as the charged particles were able to achieve relativistic velocities due to the 30kV leads. These high energies would, in the first version of G-2, contact and damage the high-voltage feedthrough insulators, eventually causing sparks.

I was an intern working with William M. Morse at Brookhaven National Lab (BNL). More information on this experiment can be found at the Fermilab and BNL websites.