High Risk Maintenance Projectat the LBNL 88-Inch Cyclotron
Jim MorelOperations Supervisor

88-Inch Cyclotron
Lawrence Berkeley National Laboratory
April 15, 2010

The 7th International Workshop on Accelerator Operation

High Risk Maintenance ProjectThe 88-Inch Cyclotron Operation• The 88-Inch Cyclotron is a small facility– staff of ~ 24 FTE (4 Oper., 10 Techs, 3 Eng, 7 Ops Grp.)• The Cyclotron runs ~ 93% availability.
• Scheduled operation of ~ 5000 hours a year.
• Operates on a 10-4 cycle, 24 h/day, 2 long shutdowns/ year.
• We support LBNL nuclear science research program (60%)
and our applied science program for the Aerospace industry
radiation effects testing (40%).
• 88-Inch has managed to survive by continuing to doimportant nuclear science research and applied science witha steady program of upgrades and by adjusting to our user’s
needs.

High Risk Maintenance Project88-Inch Cyclotron Complex
Experimental Facilities
Heavy Ion Facilities

Cave 4C GRETINA/GRETA
Cave 1 BGS

BASE
Cave 0, Isotope production
Applied and Nuclear Science
Neutron Facility
88-InchLight Ion Facility

LIBERACE
Laser Trapping

High Risk Maintenance ProjectOverview• The Cyclotron’s layout• Variable frequency RF Tank
• Accelerate every elementfrom Hydrogen to Uranium
at various energies
High Intensity Light Ions
Protons to 55 MeV
3He to 135 MeV
Heavy Ions
5 To 32 MeV/nuc
0.2  Q/M  0.5
Mass Resolution
1/3000High Risk Maintenance Project
Maintenance Work on a Mature Accelerator
Maintenance work on the 88-Inch Cyclotron is mostly routine
component maintenance and repair.
On occasion projects develop that involve systems that are nottypical maintenance work.

This talk is about such a high risk project:
To repair the Accelerating Dee vacuum seal.
– The risk is that this repair project could result in
un-repairable damage to the Accelerating Dee.
– The high current RF system might not work after the project.
– No one working at the 88 had ever done this.

High Risk Maintenance Project
The Sideview• The Accelerating Dee is a ~14 foot cantilevered structure weighing about
2000 lbs supported by a rigid support structure mounted on the RF tank.

RF Tank

Alignment Pins

Support Structure

Accelerating Dee
Alignment Pins

High Risk Maintenance ProjectThe Problem• The Dee plate vacuum seal is an
O-Ring compressed by the Deeplate against the RF tank.
• Spacers were used to prevent
over compression of the O-Ring.
• The O-Ring had been in place forover 30 years.

Dee PlateHigh Risk Maintenance Project
Historically (1960s to 1970s)• The method of servicing the O-Ring
involved pulling the Dee out of theRF tank, which required removing
parts of the Vault wall.

Vault wallremoved

Sealing
SurfaceDee PlateHigh Risk Maintenance ProjectThe Project• The project was to replace the O-ring without removing theVault wall.

• The project was analyzed to plan the sequence of steps to
optimize the efficiency of the work.
• The hazards were analyzed and mitigations were put in place.
• The team was trained on the sequence of the work.
• Each day the days work was discussed and the lessons
learned from the previous day were incorporated.
• In lieu of “Dee pulling experience” we would rely on project
preparation and the skills of the staff.

High Risk Maintenance ProjectThe Plan
• To pull the Dee we had to build a Dee cart (~ 1 year to build).
with a counterweight to support the Dee.

• We decided we only needed to move the Dee about 1 foot togive us access to service the O-Ring.
Vault
Wall
Accelerating Dee
Dee CartCounterweight

High Risk Maintenance ProjectPreparation• When the repair project was initiated the first step was to get
the cart moved into position.

Riggers moved the cart
into position.

High Risk Maintenance ProjectPreparation• Opening the Cyclotron or RF Tank requires ContaminatedArea (CA) controls to limit risk of spreading removable
contamination.
• Planning the repair required coordination of effort to manage
the limited access resulting from CA’s being posted.

High Risk Maintenance ProjectPreparation• Removing the Dee required removing the grounding strips
between the Dee, RF panels and the RF Tank

• Removing the Dee groundingstrips was risky.

High Risk Maintenance ProjectPreparation• The Dee plate wassupported and unbolted
from the RF Tank.

Load Shift• The load of the Dee wasshifted to the Dee cart.
• The alignment pins wereremoved,• The Dee cart supported theDee

High Risk Maintenance ProjectDee Pull
• When all preparations
were completed for theDee pull
the pull team prepared toenter the CA.

High Risk Maintenance Project
Dee Pull• The task was to pull the Dee back ~12 inches.

High Risk Maintenance ProjectDee Pull
• The task was to pull the Dee back ~12 inches.

High Risk Maintenance Project
Dee Pull• The task was to pull the Dee back ~12 inches.

High Risk Maintenance Project
Dee Pull• The Dee pull went smoothly.

High Risk Maintenance Project
The Repair• The old O-Ring was removed.
• The sealing surfaces were cleaned and polished (~ 1 week).
• The spacers were cleaned and replaced.
• The new O-Ring was fabricated in place.

• The new O-Ring was greased and installed.

High Risk Maintenance ProjectThe Recovery• The Dee was reattached to the RF tank.
• Damaged grounding strips werereplaced and all strips were re-attached.
• The alignment of the Dee was verified.

• The infrastructure connections were reinstalled.
• The Cyclotron was sealed and it pumped down easily.
• A standard beam was tuned out of the Cyclotron..we wereable to accelerate particles.
• The Dee cart was removed form the Vault.

High Risk Maintenance ProjectThe Return to Operation• The RF system had sparking problems and we had vacuum
problems associated with high RF power.

• We investigated and found the grounding strips had not
remained attached and were overheated.
• We also found a screwdriver had been left in the RF tank.
• The grounding strips were re-attachedusing appropriate material and thescrewdriver was removed.
• Lesson Learned• How to attach the grounding strips.
• We needed better management of tools.

High Risk Maintenance Project
Summary• The Accelerating Dee’s vacuum leak was repaired.
• The Accelerating Dee and RF system were NOT damaged.
• The project was completed despite our lack of experiencepulling the Dee and not having complete information at thebeginning of the process.
• We made some mistakes but they were not catastrophic, werecovered, we learned useful lessons.
• We now have the experience and a process to use toconduct future repairs of the Accelerating Dee if needed.