[BTeam] Upcoming beam studies opportunities

Thu May 26 17:39:26 EDT 2016

All:

 From rayTrace info from 19 May 17:00 hrs, the following puzzling 
quadratic dispersion observed in the 3R-4L junction may be less 
mysterious.  The exaggerated dispersion which was apparent in 4L had the 
exact same structure as the beta bumps in 4L.  It appears likely to me 
that there is some nonlinear dispersion (asymmetric source) in the early 
accelerator, possibly coming from 1A and potentially associated with the 
exaggerated "8 meter" dispersion peak placed there.  The "beta" analog 
indicated by rayTrace for 4L during the 19 May time frame corresponds to 
kilometer-scale horizontal betas (1500 m) when the nominal matched betas 
are about 40 meters.  The corresponding gross magnification of otherwise 
small leakage dispersion oscillates along the linac with exactly the 
same peak structure as the rayTrace "beta" (well, more like 
sqrt(beta)).  Using orbitSnaps to visualize the beam trajectory in other 
parts of the machine during the parabolic plots of dP vs. IPM4L03.XPOS 
shows bipolar dispersion in each arc, but some "one-sided" asymmetric 
dispersion in the recombiner areas feeding through from 1A.

The reason, as I recall it, that we limited the 1A21 dispersion many 
years ago to 6 meters was a fear of pushing the beam outside the linear 
quadrupole window with energy swings otherwise advisable/necessary to 
diagnose the rest of the system.  Not long ago, the dispersion peak was 
raised by ~30%, and it may be advisable to revert to 6 meter optics.

I have plots of this awaiting elogging (with the customary commentary) 
on one of the principal investigator computers in the control room, 
along with a rayTrace comparison of mismatch in the linacs between the 
19 May and (much-improved) 23 May setups.  I'll be posting this analysis 
later (I expect to be in attendance in the MCC tonight) but thought it 
was appropriate to mention this to the participants here.  I would very 
much like to revisit the 3E and 4E transverse matches, and Yves (as well 
as me) is interested in 2R details.  This appears to be a reasonable 
follow-in to our 2-pass optics tuning, and relevant to future low energy 
gain per pass setups currently anticipated for the accelerator.

The data files for the 19 May series are
horizontal: 
/cs/prohome/apps/r/rayTrace/2-2/fileio/data/2016-05-19_16:36:07/rayTrace.data
vertical: 
/cs/prohome/apps/r/rayTrace/2-2/fileio/data/2016-05-19_16:59:10/rayTrace.data

and for the 23 May series are
horizontal: 
/cs/prohome/apps/r/rayTrace/2-2/fileio/data/2016-05-23_18:27:21/rayTrace.data
vertical: 
/cs/prohome/apps/r/rayTrace/2-2/fileio/data/2016-05-23_18:45:09/rayTrace.data

The "req" files are in the same directories.

Michael Tiefenback

Todd Satogata wrote:
> Dear BTeamers,
>
> Tommy notes that we may well have beam studies time tomorrow and 
> Tuesday daytime
> at this rate. Mike notes that the 750 MHz separator shunt impedance 
> measurements
> should be done tonight. a16193 (cryo heaters) was done Wed May 25; I 
> think (but
> am not sure) that Joe's injection generator test was also done yesterday.
>
> Other open items on the beam studies plan include
>
>   http://opsweb.acc.jlab.org/CSUEApps/atlis/task/16392
>      (Continued RF fratricide tests)
>
>   http://opsweb.acc.jlab.org/CSUEApps/atlis/task/15664
>      (Linac gradient calibration with TOF viewer-limited beam)
>
> There is a possible study for zigzag YAG in the injector that could 
> use more data,
> but also depends on the state of hardware/software:
>
>   http://opsweb.acc.jlab.org/CSUEApps/atlis/task/15645
>
> Are there any other near-term beam studies that we have plans to perform?
> We discussed chopper alignment studies at Tuesday's BTeam meeting but 
> I have
> not seen an ATLis on that yet. Yves will develop ATLis items for beam 
> optics
> on separate steering paths, but those will likely not be done until 
> after his
> PRex/CRex review talk next Weds.
>
> If there are no volunteers and we have opportunity, I'll set up some 
> AutoQuad
> studies to do in the spreaders/recombiners to carefully investigate the
> 1R08/2S/2R/3S YSOF changes that were rolled back on May 19.
>
>                                                 -Todd
>
> --------------+---------------------------+----------------+------------------ 
>
> Todd Satogata | CASA Group, Jefferson Lab | (631) 807-0674 | 
> satogata at jlab.org
> --------------+---------------------------+----------------+------------------ 
>
>
> -------- Forwarded Message --------
> Subject: beam studies tomorrow between 6AM and noon?
> Date: Thu, 26 May 2016 15:12:46 -0400 (EDT)
> From: Tommy Hiatt <hiatt at jlab.org>
> To: Todd Satogata <satogata at jlab.org>
>
> Hi Todd,
> Looks like we've got some time that some studies could be done 
> tomorrow between 6AM and noon and then again on Tuesday and Wednesday 
> after the holiday between 6AM and 3:30PM.
> Do you have any studies I may be able to pencil in?
> thanks
> ht
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