Does beam size spike when ramping up energy cause problems?

[jmc2000]

I've noticed that there is now a single very large beam size spike when rampling up the energy,

Is this causing any problems?

[BenM]

I would hazard a guess at the beam size spike being a symptom of a problem rather than the cause of a problem... it could be all sorts of things - including not really there at all and just a "feature" of the instrumentation under certain conditions.

I get the impression that a large percentage of the job with commissioning the machine is determining what is real and what is a feature/bug that needs addressing.

All the above is just a guess - but it seems reasonable to me

[jmc2000]

I've noticed that there is now a single very large beam size spike when rampling up the energy,

Is this causing any problems?

On fill 1892, they perservered while filling, with the beam size varying chaotically around 10mm and in the past this has usually meant the beam having to be dumped later on. As it happens, they lost the beams this time. No doubt the operators have far more knowledge about what's going on, than I do but even so, it's curious that they carry on with a bad fill, even though refilling would take less than an hour and reduce the risk of a beam dump and longer turnaround later on.

[adam_jeff]

I've noticed that there is now a single very large beam size spike when rampling up the energy,

Is this causing any problems?

Out of interest, which instrument is the beam size which you see spiking measured with?

[Kasuha]

Out of interest, which instrument is the beam size which you see spiking measured with?

I believe he means the Dashboard, there's a Beam Size graph on the left.

[adam_jeff]

Out of interest, which instrument is the beam size which you see spiking measured with?

I believe he means the Dashboard, there's a Beam Size graph on the left.

I think that the beam size shown there is the one measured by the BSRT (synchrotron light measurements) although I'm not sure why there are two lines for each plane.
The BSRT is a complicated optical instrument with mirrors that move during the ramp to follow a moving light source. At some point during the ramp it's quite possible that the light is defocused and the beam size is measured as larger than it really is. This would be reproduced on each ramp.
In any case, it's not physically realistic for the beam to suddenly increase in size and then suddenly decrease (increase is possible but decrease is not - except a slow decrease during acceleration). So I would say it's instrumental.