PHENIX Preparing for Run 8
By Don Lynch
As summer ends, the weather cools, and the leaves begin to fall, it is once again time to button up the PHENIX experiment and prepare for the next RHIC run. From June to September each year the RHIC accelerators are shut down and the annual rituals of maintenance, upgrades and enhancements are undertaken by the technical staffs of the Collider-Accelerator Department and the major experiments at RHIC. Most of the scientists have packed up their laptops and headed to the far corners of the world to analyze the data collected from the previous runs and to report their findings to the larger scientific community, gathering accolades and esteem from their colleagues and peers. Meanwhile back at BNL, engineers, technicians and a few remaining scientists have been repairing, replacing, upgrading and augmenting the colossal facilities that make up the RHIC collider and the experiments. At PHENIX a dedicated and talented group of mechanical and electrical technicians prepare to restore the experiment to operating order.
The PHENIX experiment is made up of an extremely complex array of detector subsystems which are physically and logically segregated into 7 major subassemblies: the north and south MuID sections, the north and south Muon magnets, the east and west carriages and the central magnet. The north and south MuID sections and the north Muon magnet are stationary and permanent, while the other 4 assemblies can be moved to gain access to all of the many subsystems involved. In addition, there are two 3.5 ton cast steel semi-cylindrical background shields which are cantilevered off of the south Muon magnet, around the beam pipe. The entire assembly is entombed behind a 4-6 feet thick boundary of concrete for radiation shielding. Most of the concrete is stationary and permanent, with the exception of a (6’8” h x 3’ w x 6’ d) small plug door used for access during the runs and a large moveable shield wall (30’ x 30’ x 5’ d) which is removed during long maintenance shutdowns.
Each year, immediately after the run ends, the PHENIX technicians disassemble and relocate the tightly packed major portions of the PHENIX detector to gain access and working room for the many maintenance, repair, upgrade, calibration and verification tasks that will be performed during the next few months. In a coordinated effort PHENIX techs, with assistance from BNL trades, CAD technicians, and CAD and PHENIX safety experts, purge flammable gas, disconnect radiation safety interlocks, open and disassemble the ~450 ton large shield wall, and along with the plug door, move the components to safe and convenient temporary storage, remove and store the MuID collars, move the south Muon Magnet to its southernmost position and disconnect electric power, signal and sensor cables, optical fibers, gas and cooling water piping from the East Carriage. Next they fold up the East carriage access platforms, remove the equipment elevator, move the ~200 ton East carriage south and east to the PHENIX assembly hall to its shutdown location, and minimally reconnect electric, gas, water and fiber as necessary to maintain the detectors in a protected state and allow whatever shutdown tasks are planned.
PHENIX techs then install large aluminum plates to cover up potential fall hazards uncovered by the departure of the East carriage and position the 12 ton rolling cart and articulated manlifts to access high areas of the detectors. A few more removals of access covers (“lampshades”) as necessary for the shutdown activities and the experiment is ready for shutdown action.
All summer long the PHENIX techs, engineers and scientists tinker with the experiment, adding detector subsystems here, modifying existing subsystems there, replacing, fixing, upgrading and improving. When the fall comes, they are ready to put the experiment back in action as the “New and Improved” PHENIX experiment.
This fall cool-down of the RHIC ring was scheduled for the 1st of November. This year, as has become usual, Congress had not passed the Federal budget, but unlike recent years, the decision was made to start the run anyway. As in years past, the PHENIX tech group was given the task of putting it all back together.
The PHENIX tech crew includes mechanical technicians Carter Biggs, Kenny Jones, Jim LaBounty, John Tradeski and Mike Lenz and electrical techs Sal Polizzo and Frank Toldo. In addition, BNL electrician Mike Rau is assigned to PHENIX and integrally involved in putting the detector back together each year. The efforts also typically involve additional BNL tradespersons and CAD technicians in supporting roles.
The start up preparations at PHENIX involve a carefully choreographed set of regular tasks that typically need to be intertwined with a set of specific tasks which are unique to the current year. This year there were several detector subsystem maintenance/repair tasks and CAD work on upgrading the electronics cooling water system concurrent with the regular tasks.
The preparation for PHENIX operations unfolds as follows:
The first step is to remove access steps and any other tools and equipment used during the shutdown from inside the muon magnets. When the PHENIX techs have finished this effort, CAD techs re-install any access hatches (“lampshades”) on the north and south Muon Magnets (this year there was only one on the south magnet which needed to be installed). CAD techs use the 12 ton crane and the articulated man-lift to install the lampshades and when they are finished the man-lift needs to be relocated to the Assembly Hall (AH). PHENIX techs accomplish this using the AH crane. The south muon magnet must be in its southernmost position to leave enough room for the East Carriage (EC) to be moved into place.
The next task is comprised of moving the aluminum floor plates from the Interaction Region (IR) to the AH and pre-positioning the 2 semi-cylindrical steel MuID collars in the south east corner of the IR. Moving heavy items from the PHENIX AH to the IR requires 2 crane lifts separated by a ride on the 12 ton cart. This is because there are separate cranes for the AH and IR, divided by the shield wall. Furthermore, since the cart can only be used when the EC is out of the IR, heavy items, such as the collars, need to be pre-positioned. The MuID collar staging location is precise to about ¼ of an inch to allow clearance for the EC to be moved into the IR.
With the collars pre-positioned, the next step is to prepare the EC for its move into the IR. PHENIX technicians disconnect water, electric, gas and optical systems, while BNL carpenters fold up the various platforms allowing access to electronics. If not folded up the EC would not fit through the shield wall opening. Even with the platforms folded the EC barely fits through the opening and nearly touches the upper platform on the south muon magnet.
With the EC ready for its trip, the PHENIX technicians carefully check that there are no cables hoses or other foreign material in the path and that all cables and hoses under the EC are secured Then the techs use 2 large hydraulic pistons to push the EC west towards the IR. The pistons apply a lateral force of up to 20 tons to move the 200 ton EC on 4 Hillman rollers along the precision rails and into the IR. This requires several piston cycles as the piston has a limited stroke. At the end of each stroke the pistons are loosened from their fixed attachments to the rails, retracted to their minimum stroke and reattached to the rails for another stroke.
After the EC is moved into the IR it must be moved north onto a different set of rails. To accomplish this the EC is jacked up, one side at a time, using integral hydraulic jacks, and the Hillman rollers are rotated 90 degrees. The EC is then moved south 50 inches using a smaller portable hydraulic piston, where the carriage is again jacked up and the rollers rotated back to the original orientation. All of these moves require precision to within about 1/16 of an inch, with the final location requiring even greater precision. (An elapsed time video of the EC installation prior to run 6 can be found here.)
As soon as the EC has completed its journey, PHENIX techs and BNL tradespersons begin reattaching cables, hoses, piping, and optical fibers. Unfolding the EC platforms, reattaching the equipment elevator and restoring power connections to the various components and subsystems are accomplished concurrently.
BNL riggers then bring back the ~40 ton shield wall base and place it on the AH rails. PHENIX techs then perform precision alignment checks and corrections so that the shield wall will fit properly with the fixed IR shielding. Once aligned, the riggers carefully stack the 18 individual 20+ ton interlocking shield blocks on the base and secure the assembly with long thick threaded steel tie-rods for seismic restraint.
Meanwhile, the PHENIX techs are busy in the IR using built in hydraulic pistons to move the south muon magnet to its run position and using the IR overhead crane to install the MuID collars. The installation of the collars is a precision operation prescribed by an engineered lift procedure to assure that this lift is performed safely to both personnel and the delicate beampipe around which the collars are installed. Other techs are beginning the tedious process of carefully checking and calibrating each and every monitoring and safety system for the PHENIX complex. This checkout process consists of a PHENIX internal checkout, followed by CAD and PHENIX safety systems verification and magnet system tests. (Called “pink sheeting”, “blue sheeting” and “white sheeting” respectively due to the color of the paper used to printout the checklists for signoffs for each of these operations.)
When the riggers have completed stacking the shield wall, the PHENIX techs take over and carefully move the wall into its closed position. This is accomplished using the same hydraulic pistons as the EC used. Precision in this case, however, is not as critical as the 450 ton shield wall requires positioning only to within about ¼ of an inch. (An elapsed time video of the shield wall installation prior to run 6 can be found here.)
After the shield wall is in place, the checkout process continues. Pink, blue and white sheets are filled out, verified and signed off, the shield wall is interlocked into the radiation safety system, the RHIC rings are cooled and beam is introduced, flammable gases are reintroduced into the detectors and the scientists return to PHENIX like bees to the hive, ready for a new round of PHYSICS experimentation with the “New and Improved” PHENIX detector.