Interim Assessment of Solenoid for GlueX
Indiana University Cyclotron Facility
November 30 - December 1, 2004
South Large Conference Room
- Bob Kephart, chair (Fermilab)
- John Alcorn (LASS solenoid engineer, JLab retired)
- Claus Rode (JLab)
Background Information for the
This is an appropriate time to assess whether the plans for refurbishment of the
coils of the solenoidal magnet are complete; whether more extensive
rework should be considered; and take a fresh look the complete list of tests
which are scheduled for the magnet before installation in Hall D.
The magnet assessment will be conducted at the Indiana University
Cyclotron Facility in Bloomington, IN, on November 30 and December 1.
We will begin on Tuesday morning at 9:00 am and be finished by noon on
More general information about the
can be obtained from from the project
Chapter 5 from our design report has background information on
the solenoid magnet including plans for refurbishment. A description of
scope of work of the GlueX solenoid contains an evaluation of the status of
the magnet before any coil refurbishments, initial list of recommended modifications,
detailed assessment of the components, and early estimates of costs.
Pictures of the Magnet
Below is a brief description of the goals for the assessment as well as
details of the recent work and status of the superconducting coils.
For any travel arrangements, please contact
Linda Ceraul at 757-269-7621.
Two of the four coils of the MEGA/LASS solenoid have been refurbished
at IUCF and have been stored for shipment to JLab early next year.
The other two coils will be refurbished this fiscal year (FY05) as
soon as contract terms are agreed to, expected by October 1, 2004.
Coils three and four are already in the IUCF Solenoid work space and
the technical team has been ready to start work since Sept 1, 2004.
This is a good time to conduct an assessment of the ongoing work on the
coils as well as have experts comment on the long term plans to upgrade
this magnet for GlueX. The timing is motivated by the recent discovery of
internal corrosion of LN2 supply stainless piping during the refurbishment
of coils one and two. Coil one had LN2 system leaks that were all traced
to corrosion sites on the internal supply piping while coil two had no
shield leaks at all but had a Helium leak. Coils one and two have been
refurbished, leak tested, pressure tested and the shields have been cold
tested. Both coils are currently leak free to highest industry standards.
Coils three and four have been extensively tested and leak tested to very
high sensitivity. Location of the known shield leaks and final
refurbishment remains TBD for coils three and four.
A brief description of what we would like to achieve during the assessment
- Obtain expert advice to guide the decision to continue coil
refurbishment as planned, or opt for a more complete cryostat
remanufacture. (See notes below)
- Review plans for tests in the Test Lab, including manpower required, and
all preliminary activities in advance of installation of the magnet in
- Propose any near-term activities which could substantially reduce cost
and/or risk to the project in the long-term.
"Continue as planned" means leak repair, replacement of instrumentation
and MLI. The same extensive testing(leak, pressure and cold) and
periodic retesting are relied on to assure that
the four coil cryostats remain leak free.
"Remanufacture" means that the four solenoid coil cryostats
are dismantled and that the Helium vessels are removed (but not
otherwise disassembled) from the cryostats to permit replacement of all
LN2 supply and return piping to eliminate possible corrosion sites. A
side decision to replace the present copper LN2 shields with comparable but all
stainless shield panels would be a cost effective side benefit.
Status and Detailed Questions on Coil Refurbishment
Report by Paul Brindza
The work to refurbish the GlueX Solenoid is at an interesting point where
we have a significant choice to make about how to proceed. The first two
coils are completely refurbished, tested LN2 tested and in dry nitrogen
storage. They have new shield instrumentation, new strain gauges, new
conflat flanges on all internal connections, no leaks and they have passed
a pressure test. However coil one was at this stage around Memorial Day
and it sprung a leak in the LN2 supply pipe at a pressure of only 30
pounds gauge. This is below the JLAB LN2 system operating pressure. The
leak was found and fixed and coil one has since passed all of the above
tests. However the leak source was found to be surface "pits" in the
stainless steel LN2 supply line. Chemical analysis confirmed the existence
of chlorides and the "pits" had visible red inclusions at the bottom. All
this is evidence of corrosion, possibly due to brazing fluxes left over
from the initial assembly or subsequent repairs.
We are about to perform the same refurbishment on the remaining coils
three and four. These two coils are known to have large LN2 shield leaks
at as yet unknown sites.
The question is "Should we proceed with the R&R activities as planned and
rely on further testing to catch any future leaks due to latent corrosion,
or should we "bite the bullet" and remove all the suspect stainless
piping that may harbor the cancer of corrosion"?
If we decide to do a more thorough rebuild, essentially a complete
remanufacture of the four cryostats, it will cost us significant funds.
We estimate that the R&R of coils cost will easily double. The extra cost
could be at least 250K$ to 350 K$ over and above what we have and will
spend to get all four cryostats completely remanufactured. This is
partially offset by not having to conduct the months long search for the
location of the leaks in Coils three and four.
If we choose not to do the extra work and rely on periodic retesting to
make sure we don't assemble leaky coils in Hall D then we run the risk
that we spring a leak perhaps after the GlueX experiment starts. Every
experiment that has used this magnet has had to contend with leaks. The
corrosion pits that we have seen and the leak that opened during pressure
testing ( greater than 10^-4 warm) may exceed our ability to pump.
Are the risks worth the extra costs?
Are there extra risks if we remanufacture the cryostats that may reduce the
If we choose to remanufacture the cryostats, should we then replace the
copper shields with all welded stainless inflated panels?
(This is at a
small extra cost relative to the labor cost to perform the remanufacture).
Is there anything else that should be considered if we choose to
If we choose not to remanufacture then what further testing could be
considered to buy more confidence?
Two of the Coils (coils one and three) have resistive shorts to ground.
These shorts are historical and MEGA ran with them. However the value of
the short in Coil one has changed while the short in coil three is nearly
identical. There is thus a resistive short of 2 ohms across about half the
solenoid when in operation. During charging there would be of order 5
volts thru two ohms thus dissipating approximately 2.5 watts, mostly in
coil 1 at the site of the short. This assumes that the shorts remain at
their room temperature values. If the short(s) are metallic then the
resistance would decrease and if the shorts were due to oxides then in
general they would become more resistive and if the shorts are due to
foreign objects then anything can happen including the disappearance of
Given this and considering the other work proposed, is it worth the
obvious extra work and risk to open the coil cases and try to remove
Physics Division, Jefferson
12000 Jefferson Ave., Mail Stop 12H, Newport News, VA 23606
Office: (757)269-7625, FAX: (757) 269-5800