[BTeam] Injector Alignment

[Steve Benson]

We see the same thing in the LERF cryounit, only worse because the gradients are higher. By luck, the horizontal kicks are small but the vertical kick is about 10 mrad (the horizontal kicks depend on the cavities phases and, for certain phases close to where we operate, happen to almost cancel out. The vertical kicks add.) Because of this we cannot center in the first two quads after the booster cryounit. In my mind, the best way to fix this is to use the new booster cryomodule, which has a different FPC design that should not have strong kicks. Until then, the idea of just not using the first quad and correcting for the FPC kicks sounds like quite a reasonable solution.  At one point we did install windows and checked to see if the cavities were offset and producing the kick because of that. They were actually pretty well aligned, so it was the FPC.

Steve Benson

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________________________________
From: BTeam <bteam-bounces at jlab.org> on behalf of Michael Tiefenback <tiefen at jlab.org>
Sent: Friday, October 2, 2020 1:08:27 PM
To: Jay Benesch <benesch at jlab.org>; bteam at jlab.org <bteam at jlab.org>
Subject: Re: [BTeam] Injector Alignment

Jay,

I do not read your comments as arguing that we ought _not_ to move the cryounit.  I am not certain whether you think an attempt to "improve" things is ill- or well-advised, or whether you are attempting to withhold opinion on that.

The (large) beam offset in the beam line downstream from the cryounit has been a problem from multiple perspectives, and I thought we should consider what might be done.  The 1.2 mm offset mentioned in Reza's note (survey reference) that Todd forwarded appeared to me implicitly to portray a 1.2 mm offset as the total content related to the beam line issue.  I think this is a significant integer factor too small (like five times too small), and that speaking "1.2 mm" in this context is very misleading to observers unfamiliar with the actual situation.

Michael Tiefenback

________________________________
From: Jay Benesch <benesch at jlab.org>
Sent: Friday, October 2, 2020 12:47
To: Michael Tiefenback <tiefen at jlab.org>; bteam at jlab.org <bteam at jlab.org>
Subject: Re: [BTeam] Injector Alignment

Mike,

The transverse kick is why we never use MQJ0L01: add the feeddown to the
transverse momentum and the correctors are too feeble.  Steer to center
the beam before 0L02 and one can get by.  The peak beam envelope is
large (~2.5 mm sigma) as one develops the FODO lattice through
0L02/0L02A, 0L03A/0L03, 0L04.  That's why I wanted to switch to solenoid
focusing in the 6 MeV region.

Jay
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