12/4/18
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Completed
- Ghost beam test 1a/1b (see previous log entry)
- Ghost beam systematic study: varied anode bias between 1kV and ~300V for given gun solenoid currents (150A, 125A, 100A (bad data...), and 75A)
- Measured Ghost beam current on faraday cup. Noted similarities between ghost beam current decay and gun vacuum decay (or really improvement)
- Creating GPT simulations of protons and electrons:
- 1 million and 10000 electron randomized distribution simulations. These suggest that electrons with sufficiently low KE could be trapped within the first two solenoid lenses.
- 10000 proton randomized distribution simulations. Similar to electron simulations above, except that the protons get trapped BETWEEN the two solenoid lenses, not within them like the electrons.
- GPT simulation degree of accuracy matters: if the accuracy (or really precision) of the simulations is too low, the electron/proton trap is unstable. GPT accuracy above 10, corresponding to a precision of 10^-10, seems to be sufficient for our purposes, though this increases the time it takes to create the simulations.
- Used an ion precipitator as a BPM to determine if we can see characteristic ion frequencies on the sidebands of the electron beam frequency. Unfortunately, the electron bunch length was way too small to see any significant peak.
- Used spectral analyzer to determine if we could see light due to ionization at the viewer. No significant light was measured.
In Progress
- Analyzing the above tests.
- Creating GPT simulations of electrons AND protons with and without space charge. Will extend this to the conditions of the ghost beam studies (I'm currently still using the 1mA run conditions from August).
Future Work
- May take more ghost beam measurements in the next couple of weeks.
- Writing and publishing a paper on simulations of ion bombardment of polarized photocathodes using Joe's measurements. Will either use GPT or IBSimu to create a simulation of ion production at GTS.