Gabor Lens meeting: 14Jan21; 16:00 GMT

Summary of actions

Notes

2. Updates on the particle generation: HT
   • Fixed a bug within the coordinate conversion script. Thus, the artefacts in the phase space plots disappeared.
   • Optics with the laser-generated beam closer to the ideal optics - with the exception of one point in the arc. Possible cause: large population of off-axis low energy protons after the first bending magnet.
   • The nozzle was treated as a cylinder.

3. Next iteration of the Gabor lens: CW/All
   • Plan of simulations/design changes needed
     • CW: Feed electrons on-axis - good filling of the lens, but not viable as a modification to LhARA beamline. Better alternative: an annular emitter (hot wire) which produced a cylinder of electrons. The assumption is that as the electron population builds up, the space charge would move radially in, closer to the axis. Some simulations were done for 5 to 20 ns to look at the electron distribution.
     • CW: Need to reduce the energy of the electrons to allow them to move closer to the lens axis. Other traps did that (eg. anti-H trap at CERN - electrons emit RF radiation and lose energy). For our Gabor lens, the RF frequency is very low so that the wavelength is larger than the length of the lens. The main proposed alternative is collisional damping due to a background gas.
     • RB: Proposed to start with a higher magnetic field strength to fill the centre of the plasma column and then reduce the field strength.
     • CW: Further possibility to enhance the B-field locally.

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Agenda

1. Introduction, notes and actions: KL/All

2. Updates on the particle generation: HT

3. Next iteration of the Gabor lens: CW/All
   • Plan of simulations/design changes needed

4. AOB: All

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