[BTeam] CEBAF/Cryo Status

[Andrew Kimber]

Arne, 

Just shunts from DCP like you said. When?

Andrew


> On Mar 28, 2015, at 1:50 PM, Richard Nelson <nelson at jlab.org> wrote:
> 
> Arne,
> 
> Not good news on the cryo front. I wondered why we were in restricted.
> 
> Nothing comes to mind for RF issues at 6 GeV.  Presently pass 2 IOT is bypassed, but if it's required it can unbypassed.
> 
> Rick
> 
> From: "Arne Freyberger" <freyberg at jlab.org>
> To: "Matt Bickley" <bickley at jlab.org>, "Steve Suhring" <suhring at jlab.org>, "Paul Vasilauskis" <vasilaus at jlab.org>, "Theo Larrieu" <theo at jlab.org>, "Anthony Cuffe" <cuffe at jlab.org>, "Ron Lauze" <lauze at jlab.org>, "Randy Michaud" <rmichaud at jlab.org>, "Pam Kjeldsen" <kjeldsen at jlab.org>, "Reza Kazimi" <kazimi at jlab.org>, "Arne Freyberger" <freyberg at jlab.org>, "Ken Baggett" <baggett at jlab.org>, "Matt Bickley" <bickley at jlab.org>, "Randy Michaud" <rmichaud at jlab.org>, "Pam Kjeldsen" <kjeldsen at jlab.org>, "Steve Suhring" <suhring at jlab.org>, "Theo Larrieu" <theo at jlab.org>, "Reza Kazimi" <kazimi at jlab.org>, "Anthony Cuffe" <cuffe at jlab.org>, "Ron Lauze" <lauze at jlab.org>, "Andrew Kimber" <kimber at jlab.org>, "Omar Garza" <garza at jlab.org>, "Nelson, Rick" <nelson at jlab.org>, "Arne Freyberger" <freyberg at jlab.org>, "Dan Sexton" <dsexton at jlab.org>, bteam at jlab.org
> Sent: Saturday, March 28, 2015 1:29:24 PM
> Subject: Fwd: CEBAF/Cryo Status
> 
> Time to start thinking about a 6GeV program.  What are the issues?  Shunts?  What else?
> 
> Arne
> 
> 
> -------- Forwarded Message --------
> Subject:	CEBAF/Cryo Status
> Date:	Sat, 28 Mar 2015 13:26:22 -0400
> From:	Arne Freyberger <freyberg at jlab.org>
> To:	Hugh Montgomery <mont at jlab.org>, mike dallas <mdallas at jlab.org>, Bob McKeown <bmck at jlab.org>, Andrew Hutton <Andrew at jlab.org>, Fulvia Pilat <pilat at jlab.org>, rode >> Claus Rode <rode at jlab.org>, Allison Lung <lung at jlab.org>, Leigh Harwood <harwood at jlab.org>, Rolf Ent <ent at jlab.org>, rossi patrizia <rossi at jlab.org>, Mary Logue <logue at jlab.org>, Bob May <may at jlab.org>, Will Oren <oren at jlab.org>, Tim Michalski <michalsk at jlab.org>, Rusty Sprouse <sprouse at jlab.org>, Rolf Ent <ent at jlab.org>, rossi patrizia <rossi at jlab.org>, 'Javier Gomez' <gomez at jlab.org>, Cynthia Keppel <keppel at jlab.org>, Volker Burkert <burkert at jlab.org>, Eugene Chudakov <gen at jlab.org>
> CC:	Jonathan Creel <creel at jlab.org>
> 
> This is a summary email from Arne and Jonathan.
> 
> Cryo recovery efforts since the power outage Wednesday have not converged.
> 
> CHL2->SCN->NorthLinac: has gone through several 2K pumpdowns only to trip an hour or so after achieving 2K.  The CHL2->SCN hardware is in working order.  Analysis indicates the cause of these trips appears to be contamination plugging across the 2K to 4K heat exchanger in the bottom of the SCN cold box. This is forcing them them to operate at or near their surge curves. This problem coupled with the previous contamination problem with SCN cold compressor 2 seems to indicate that we had a significant amount of contamination enter the system or move in the system during the multi-hour power outage. The SCN must be warmed up and decontaminated in order to support any 2K operation.
> 
> CHL1->SCM->SouthLinac:  has not been able to pump down to 2K.  Evidence is mounting that there is a likely physical problem with cold compressor #4 (CC4) in the SCM.  CC4 went through an unusual trip during the first pump down attempt after the power outage, the controller responding as it should but the hardware ramped from 500Hz to 0Hz in a very abrupt fashion. The magnetic bearings for CC4 will no longer levitate the compressor wheel. The coils are drawing maximum current but the internal hardware is not moving. The coil resistances appear normal. The CC4 and CC5 mag bearing control cables were switched during trouble shooting.  Either mag bearing cabinet can successfully levitate CC5 but neither mag bearing cabinet can successfully levitate CC4.  This leads to the conclusion that there is likely something physically wrong with CC4. This is a single point of failure; CC4 can not be by-passed.  The SCM must be disconnected and warmed up in order to access the compressor to determine what happened and carry out any repairs. Cryo is performing some final checks on CC4 and developing plans for an SCM warm up which could last several weeks to months in duration. 
> 
> Short Term: No beam  operations this weekend and probably for the next week or two.  Cryo will continue to assess the CC4 problem. Cryo is formulating plans this weekend which they will review with Ops on Monday morning to formulate a revised schedule.
> 
> Long Term (Plan B):   There are options on the table if CHL1->SCM is not available.   These options include, but there may be others:
> Configuring both CEBAF LINACS to 2K on CHL2->SCN   and establishing a 5-6GeV CEBAF.   Hall-A has some 2GeV data and HPS data can be accommodated by this configuration, Hall-D could do some commissioning activities with a 6GeV beam.
> Extending the run well beyond  the May 4th scheduled end date, this will result in a tremendous amount of UIM/CHL2 and other contractual changes.   But it would retain the physics weeks. 
> 
> Arne and Jonathan
> -- 
> Arne Freyberger
> Director of Accelerator Operations
> Jefferson Lab             
> 12000 Jefferson Avenue      Cell: (757) 876-6289
> Postal Suite 19             Email:  freyberg at jlab.org 
> Newport News, VA 23606  
> 
> 
> 
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