Jefferson Lab Weekly Briefs
June 20, 2012
JLab All-Hands Memo
JLab Landline Phone Outage Set for Saturday, June 23
To report an emergency at JLab during this time:
For more information regarding this outage, contact the IT Division Helpdesk. For further information regarding Emergency Response steps to take during this scheduled phone outage, contact JLab's Emergency Manager, Tina Menefee, 768-4030.
12 GeV Upgrade
The second sector of the PreShower Calorimeter for Hall B's CLAS12 is complete and has been tested successfully with cosmic rays. Stacking of lead sheets and scintillator bars threaded with wavelength-shifting fibers is complete for the third sector and is being readied for the fourth. The third and fourth Region 1 wire chambers are being strung at Idaho State University; the fifth Region 2 chamber is complete at Old Dominion University, and the first two Region 3 chambers are being strung at JLab. High-voltage and readout boards are being added to sectors that are strung, and cosmic ray testing is underway. The first complete module of the Silicon Vertex Tracker was tested in CLAS during the recent accelerator run, and the flex-cables and support staves with all recent improvements are being manufactured. The last two of five types of mirror substrates are being built for the high threshold Cerenkov counter. Delivery of the final orders of photomultiplier tubes and scintillator material to the University of South Carolina has begun, where assembly of the forward time-of-flight 1-b slats is progressing well. An agreement was signed with FermiLab to produce the six large cold masses with the coils for the torus magnet.
Q-weak disassembly work continues in Hall C. The electronics bunker and much of the main detector shielding have been removed. Detector removal has started with the unmounting of one of the large region 3 drift chamber packages. The Hall C Summer Workshop is Friday, June 22, and Saturday, June 23.
This began the first week in the Long Shut Down where all areas of the accelerator were open for access during the day. The intent is at the end of each day, the South Linac will be locked for superconducting radiofrequency cryomodule commissioning and the injector and North Linac will be locked to allow work on the Polarized Electrons for Polarized Positrons (PEPPo) experiment to continue overnight and into the morning. On Monday, the lock up of the injector was delayed due to an issue with air pressure interlocks preventing the opening of vacuum valves. Starting Wednesday, the injector status was changed to remain locked during the day when possible to allow work on the PEPPo magnets and to aid in ensuring no inadvertent changes are made in the injector area. On Wednesday, the PEPPo power supplies were worked on by Engineering Support, resulting in a more stable output. Also on Wednesday, the accelerator participated in a sitewide load reduction test, which resulted in the shedding of approximately 2500 kilowatts of load. The remainder of the week and into the weekend was smooth running, with PEPPo work continuing in the injector and cryomodule commissioning continuing in the South Linac.
The FEL team delivered ultraviolet light at 370.5 and 427 nanometers to a metastable krypton beam, observing only small effects. This is a very important result, because it validates the use of un-filtered 3rd harmonic vacuum ultraviolet light to try to create a metastable beam. The gun performed extremely well this week. The DarkLight test chamber was installed in the 3F region of the FEL.
Center for Theoretical and Computational Physics
A new paper points out an important difference between two different versions of the theory describing interactions of pions and nucleons. The theory based on the "pseudovector" πN coupling is consistent with properties of QCD in the limit of vanishing quark mass, whereas that based on the "pseudoscalar" coupling (which is often used in the literature) is shown to give incorrect behavior in this limit. The paper stresses the importance of using the correct theory to reliably describe the effects of the pion cloud on nucleon properties.
The survey and alignment group has been busy since the start of the May shutdown of the 6 GeV machine. The group has completed an elevation survey (levels) around the accelerator ring. This comprised more than 400 survey monuments being measured. The closure over this distance was 0.6 millimeters, an error of 1 in 2.2 million or 4.6 x 10-7. The group is now carrying out a three-dimensional survey of the entire accelerator. This is required as the tunnel has shifted and expanded by millimeters over its lifetime. After the completion of the Q-weak and g2p experiments in Halls C and A respectively, the alignment group surveyed the final position of the detectors and targets. The survey of monuments in Hall D and the tie in of the main accelerator to the new hall is continuing. The group also laid out the stands for the new equipment in the Hall D target area.
Environment, Safety, Health and Quality
National Safety Month
Important Golf Cart Safety Reminder
Computing and Networking Infrastructure
Planned Network Maintenance, June 27, 5-7 p.m.
Email Migrations into New System Continue
JLab Personal Dosimeter Change Out Set For July 2
JSA Initiatives Fund Call for Proposals Announced
Tracking Thomas at JLab
No one submitted a correct answer for the June 13 location, so Little Thomas has provided another picture with a different background in the same location as an additional hint. Check out the Tracking Thomas webpage for a better view of this mystery location.
JLab Calendar of Events
June 18-22: Program Advisory Committee Meeting (PAC39)