[BTeam] [New Logentry] Saturday Evening CEBAF Status and path towards energy scaling on Monday

[freyberg at jlab.org]

========  SATURDAY EVENING CEBAF STATUS AND PATH TOWARDS ENERGY SCALING ON  ====
======== MONDAY [1]  ===========================================================


Lognumber 3278329 [1]. Submitted by freyberg [2] on Sat, 03/29/2014 - 21:14.



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|Logbooks:|BTLOG [3]|
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Another CEBAF roller coaster ride. After struggling with pathlength issues, 
CEBAF hardware, and optics issues all week, it was a significant accomplishment 
to get the optics setup to converge Friday swing. Unfortunately going CW has 
illuminated some additional hardware issues with an at present unknown source. 
I 
hope the accomplishment of getting this optics setup to converged does not get 
obfuscated by the hardware issue.

The observation we are presently dealing with is an horizontal jitter on the 2A 
SLM and BLM trips at high dispersion points. The nominal conclusion is that 
this 
is an RF or energy issue. 12 hours of looking at the RF has not found anything 
wrong. With some of the diagnostics not quite 100%, there are some blind spots 
in our tool set. For example 1A SLM would be useful and BLA waveforms are not 
working. So I pass on some important guidance from Mike T. that in the past 
some 
of these instabilities have been sourced by magnetic issues and other sources. 
Indeed discussion of BBU has been heard in the control room as well as some 
cursory magnet checks. Nothing is ruled out and I encourage everyone to keep an 
open mind as they engage the problem.

With that said, the hall does have a useful low current program which we 
switched over to on early Swing shift. The hall program is limited to 2$\mu$A 
as 
beam currents above result in some vacuum excursions. Parasitic and 
opportunistic debugging is encouraged.

The program for Sunday remains the Moller program and the program for Monday is 
to perform the energy scaling. On Monday we will be down most of the day-shift 
for RF recovery, which is needed as we by-passed a large number of cavities 
today in trying to identify the energy jitter source.

The goal for the 1000MeV/linac setup is to send tune-mode beam to Hall-A at 
greater than 6GeV. Once this is accomplished (Wednesday?), we could try CW 
operations again just to give the Hall-A one more try for the target boiling 
test. Who knows, the change in energy might flush out or hide the present 
issue. 
It all depends on how the energy scaling goes, we might be performing optics 
tuning all week. However, I must stress, that establishing 6GeV, tune-mode beam 
is a good example of where good enough is good enough. We are not looking for a 
perfect setup, just get the beam on target, get the energy required, get some 
events to tape and declare victory. What we do after that will be topics of 
discussion next week.

Thanks for all the hard work in the control over the past week. One more week 
to 
go.

[1] https://logbooks.jlab.org/entry/3278329
[2] https://logbooks.jlab.org/user/freyberg
[3] https://logbooks.jlab.org/book/btlog
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