[FFA_CEBAF_Collab] FFA energy range

[Jay Benesch]

Colleagues,

I did not understand this limitation when we changed to one FFA.  I 
suggest that being able to vary the beam energy is more important to 
physics than 22 GeV.  It would make the splitters easier to design too; 
for that matter it's not clear that six splitters fit in the tunnel at 
all.

Jay


-------- Forwarded Message --------
Subject: Re: [EXTERNAL] Re: FFA energy range
Date: Thu, 25 May 2023 15:41:43 +0000
From: Brooks, Stephen <sbrooks at bnl.gov>
To: Jay Benesch <benesch at jlab.org>
CC: Katheryne Price <kprice at jlab.org>

Yes, essentially having the tunability costs you a turn because it 
requires the FFA to accommodate lower energy beams at the low energy end 
of the range, which would increase the ratio unless the highest energy 
is also lowered.

You have three options:
~22GeV with no tunability, just discrete energies (14, 16, 18, 20, 22)
~22GeV with a percent or two of tunability, so a small range around each 
energy above
~20GeV with close to full tunability (I haven't checked if it can 100% 
cover with no gaps)

      -Stephen

________________________________________
From: Jay Benesch <benesch at jlab.org>
Sent: 25 May 2023 11:36
To: Brooks, Stephen
Cc: Katheryne Price
Subject: Re: [EXTERNAL] Re: FFA energy range

Stephen,

I did not understand that.  If we had only five FFA passes, 20 GeV top,
could the good field region and tune accommodate some energy span?  The
users might prefer that to fixed energies, especially given the
unreliability of our SRF.

Jay

On 5/25/23 11:27, Brooks, Stephen wrote:
> There isn't any adjustable linac energy range in the 1-FFA solution.  This is one of the requirements that ended up being dropped when we changed to a single FFA.  Or to put it another way, accommodating linac tunability to get a fully continuous energy range was one of the things that pushed me towards the 2-FFA solution.
>
> Of course we could accommodate a couple of percent by running at slightly dubious tunes.
>
>       -Stephen
>
> ________________________________________
> From: Jay Benesch <benesch at jlab.org>
> Sent: 25 May 2023 11:22
> To: Brooks, Stephen
> Subject: FFA energy range
>
> Stephen,
>
> I've forgotten the allowed energy range as it's been a year since it's
> been discussed.  I remember linac energy range 1000-1100 MeV.  Is that
> correct?
>
> Jay