High Gradient RF in strong magnetic field #3: review and discussion – 09 September 2025
Short minutes:
Question: Is there an asymptote in the maximal achievable gradient when the DC magnetic field is higher than a given value (~ 1 T)?
Answer: According to the beamlet model in Bowring’s paper and to CST simulations at CEA, yes, since the beamlet radius reaches a maximum around 1 T. however, with a model of magnetic field influence on the emission site, we don’t know. And in Moretti’s experiments, there is no asymptote.
Discussion: Need of a “standard” test cavity design, scalable with frequency, that could be used in simulation.
SLAC will start tests at 2.8 GHz and then 1.3 GHz. The first cavity will only have RF diags. The solenoid is expected in January. It is not shielded so it can provide lots of fringe field. Their test stand is open to other members of the collaboration.
The necessity of having more diagnostics in tests, especially cameras, is underlined (to know what really happens).
Three students are presently working on the breakdown phenomena:
· A Phd student in Strathclyde, on field emission
· Dillon Metternich, PhD student in Berkeley lab: see https://indico.cern.ch/event/1557051/
· Yuan Zhi LIM, Master student at CEA, working on Magneto hydrodynamical simulations for an emitter.
Next meetings:
· Student presentations
· Test stand progress
Everyone is free to make a proposal, just email to juliette.plouin@cea.fr
