• Tue, 04/28/2015 - 8:52am

    Spring Challenges!
    April 27, 2015


    Spring is often an unstable period. Temperature fluctuations, pretty days interspersed with storms, blossom blasted by gusts of wind. That seems to have been the case at the Laboratory over the past several weeks. 

    The 12 GeV Upgrade project was subjected to scrutiny in a mini-review conducted by the Office of Project Assessment. It went very well. This was partially because we had succeeded in projecting a more coherent view of the status of the project from a cost and schedule perspective and partially because we have seen some good progress with the superconducting magnets.

    By now we have 5 cold masses delivered from Fermilab for the Hall B Torus. The 6th is expected within a week and the two spares have been started. The cryostat work on three coils is complete and the coils are in the hall. Two are mounted and interconnection through the so-called Hex beams is underway. A week ago, I accompanied our team on a visit to Everson Tesla Inc. in Nazareth, Pennsylvania, and saw the first of the Hall B solenoid coils, for which the winding is now complete.

    In Hall C, the Q1 magnet from Scientific Magnetics is on the SHMS, and the magnet has been tested successfully up to 110% of the expected operating current. The HB dipole also arrived from NSCL-Michigan State University and is mounted and nearly ready for operation. The big dipole at SigmaPhi in France, is in preparation for collaring; the 4 coils of the Q2 magnet are glued together ready for wrapping and potting of the outer shell and the first pair of coils of Q3 have also been potted.

    With some hiccups, the accelerator was working towards operation for three Halls, A and D at high energy, and Hall B at low energy. The latter, for the Heavy Photon Search experiment, only during evenings and weekends to allow progress with CLAS12 Torus assembly.

    Progress came to an abrupt halt on March 25. A power outage offsite took out the main sub-station and the accelerator site. Power came back on the smaller substation within a relatively short period, but only after several hours to the main sub-station. As a consequence, the CHL complex suffered. On the one hand there was some contamination in one CHL, and on the other, after some recovery attempts, a compressor failed in the other cold box. Investigations over the next several days established that the latter was serious and that at a minimum, month(s) of effort could be anticipated before the cold box could be used again. However, the contamination could be cleared in a couple of weeks. A decision was taken to reconfigure the crippled plant to operate both linacs off one plant, analogous to the 6 GeV era. Of course, the immediate implication was lower energy. It also took quite some work to get there. As a result, it is only now that there is a sense that both the cryo-plant and the accelerator are properly under control.

    During this time, we had a review of the Contractor Assurance System. This is the system in which the Laboratory, JSA, and the DOE site office work together to assure a reasonable level of operations and rigor in the way we do business. The review was led by a distinguished physicist who provides oversight for Princeton Plasma Physics Laboratory for Princeton University. He and the external team gave us a glowing report; in particular they were impressed by the level of cooperation evident in the way we do business at Jefferson Lab.

    And so to this past week.

    Urged by Bob McKeown, Arne Freyberger, Jonathan Creel, and others, we re- examined the plan to shut down the accelerator on May 4. There are all manner of things to consider. In May, the meter, which sets our “demand charge,” and hence our electricity cost for next year, is read. There are contracts for work starting as soon as the accelerator stops. There is also consideration of work needed to investigate and hopefully repair the damaged cold box. We have some scheduled work by the vendor of CHL to mitigate some minor performance issues during the shutdown. We also plan on trying to do some Helium treatment of installed cavities to maintain the gradient capability of the installed cryo-modules. So, as an interim response to the situation, we have decided to extend the run of the accelerator for a couple of weeks. Unfortunately this cannot include high energy both because of the cryogenic limitations and because of the cost. We will concentrate on single pass running to salvage some physics for the Heavy Photon Search. This was announced to the user community on April 23.

    As to the ultimate length of the shutdown and hence the startup of the accelerator in the Fall, we are still looking into our options.

    So a spring full of challenges, but hopefully with some modicum of happy ending!!!