[FFA_CEBAF_Collab] [EXTERNAL] RE: FFA energy range

[Brooks, Stephen]

--[If we want some tunability in the energy, couldn't we keep the bottom energy of the FFA arc the same, then just do some path length adjustments to have the higher passes run off crest? that would be a knob to lower the energy not raise it]--

Yes, that would actually fix the problem!  I just don't know how much the longitudinal dynamics would cooperate with being off-crest.

      -Stephen

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From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org> on behalf of Edith Nissen via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>
Sent: 25 May 2023 13:25
To: Kirsten Deitrick; FFA_CEBAF_Collab; Berg, J Scott
Subject: Re: [FFA_CEBAF_Collab] [EXTERNAL] RE:  FFA energy range

If we want some tunability in the energy, couldn't we keep the bottom energy of the FFA arc the same, then just do some path length adjustments to have the higher passes run off crest? that would be a knob to lower the energy not raise it (unless we leave some phase room in the nominal configuration).

It would make the splitters/recombiners a bit more complicated, and that may end up being a showstopper.

Edy Nissen
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From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org> on behalf of Berg, J Scott via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>
Sent: Thursday, May 25, 2023 12:15 PM
To: Kirsten Deitrick <kirstend at jlab.org>; FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>
Subject: Re: [FFA_CEBAF_Collab] [EXTERNAL] RE: FFA energy range


If everything adjusted to keep the energy ratios the same in the splitters, then we would not need to do anything. If the ratios aren’t maintained, then there will be some steering adjustments needed. Presumably the same issue is faced in CEBAF.



-Scott



From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org> On Behalf Of Kirsten Deitrick via FFA_CEBAF_Collab
Sent: Thursday, May 25, 2023 12:05 PM
To: FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org>
Subject: Re: [FFA_CEBAF_Collab] [EXTERNAL] RE: FFA energy range



Isn't there a concern that just because the FFA can accept any energy in the range, the splitter lines won't have the necessary flexibility to provide position/angle for different energies? Or is this a case of "if we know we need it, we can make sure we have that flexibility"?



-Kirsten

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From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org<mailto:ffa_cebaf_collab-bounces at jlab.org>> on behalf of Berg, J Scott via FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org<mailto:ffa_cebaf_collab at jlab.org>>
Sent: Thursday, May 25, 2023 11:59 AM
To: FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org<mailto:ffa_cebaf_collab at jlab.org>>
Subject: [FFA_CEBAF_Collab] [EXTERNAL] RE: FFA energy range



Presumably this could also be addressed with a redesign of the FFA? I would think we could accommodate the additional energy range and flexibility at the cost of larger magnets and maybe some other modest penalties like radiation? Or is there something that stops this from working? I'm not suggesting it's the best choice, just an option.

-Scott

> -----Original Message-----
> From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces at jlab.org<mailto:ffa_cebaf_collab-bounces at jlab.org>> On Behalf Of Jay
> Benesch via FFA_CEBAF_Collab
> Sent: Thursday, May 25, 2023 11:53 AM
> To: FFA_CEBAF_Collab <ffa_cebaf_collab at jlab.org<mailto:ffa_cebaf_collab at jlab.org>>
> Subject: [FFA_CEBAF_Collab] FFA energy range
>
> 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<mailto:sbrooks at bnl.gov>>
> To: Jay Benesch <benesch at jlab.org<mailto:benesch at jlab.org>>
> CC: Katheryne Price <kprice at jlab.org<mailto: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<mailto: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<mailto: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
>
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