Jefferson Lab Weekly Briefs March 4, 2009
Jefferson Lab Weekly Briefs
March 4, 2009
12 GeV Upgrade
A review of the reference design and coil trial winds of the horizontal bend (HB) magnet was completed. This superconducting HB magnet allows for small-angle operation of Hall C's Super High Momentum Spectrometer. This work was performed at the National Superconducting Cyclotron Laboratory at Michigan State University. The review committee validated maturity of the reference design and pointed to items that would assist in the successful construction and operation of this critical magnet.
A series of reviews of the detailed plans for installation of 12-GeV equipment (and de-installation of 6-GeV equipment) in the experimental halls is presently ongoing, with Halls A, C and D reviews completed and Hall B upcoming.
Eugene Chudakov has graciously assumed responsibility as the interim Hall D leader.
The first European Workshop on CLAS12 was held Feb. 25-28 in Genoa, Italy. With more than 120 registered participants, the attendance was beyond all expectations. In addition to a diverse physics program that covered topics from GPDs (generalized parton distributions) and TMDs (transverse momentum dependent parton distributions) to nuclear correlations, there were talks by representatives of the French and Italian funding agencies and the Nuclear Physics European Collaboration Committee (NuPECC).
At JLab, Hall B continues to run the eg1-dvcs group of experiments that combines measurements of DVCS (deeply virtual Compton scattering) and semi-inclusive pion production on a polarized proton target (NH3). The run has been extended by four days until March 16.
The accelerator was running well for the first couple of days. On Thursday, a failed pump caused the insulating vacuum of cryomodule 1L06 to deteriorate. The vacuum was recovered after the faulty pump was replaced. During the vacuum work, the injector laser spot was moved and the Wien angle was changed. Hall A was changed from pass 4 to 5, and Hall C from pass 5 to 4. On Friday, the vacuum in 1L04 region started to deteriorate. Sunday evening, a power glitch tripped off some magnet box supplies and the Central Helium Liquefier. After the CHL was recovered, cryomodule 1L06 was cryo-cycled to recover the vacuum. Beam delivery resumed at noon on Tuesday.
Free-Electron Laser (FEL)
After several days (a short time considering the work scope) optimizing the FEL with the longer drive laser pulse, the FEL team successfully operated the FEL at 0.93 microns for over five hours. There were no "magic knobs" to turn in order to maintain a high level of performance; the accelerator and laser simply ran well. This is a tribute to everyone’s hard work on improvements.
A relativistic quark model based on the covariant spectator theory has been used to describe the electric quadrupole and the magnetic octupole moments of the Δ resonance (arXiv:0902.4212). The Δ is modeled as a quark-(quark pair) system with a dominant S-wave state (orbital angular momentum zero) plus two small admixtures (about 1%) of D-wave (orbital angular momentum two) components. If the Δ were a pure S-state, both moments would be exactly zero; but with the predicted D-wave components, they are both negative, suggesting an oblate (pancake-like shape) for both the electric charge and magnetic dipole distributions.
JLab's Safety Numbers
58 Days since Last Recordable Accident (JLab record: 331)
JLab Calendar of Events
March 7: Virginia Regional Middle School Science Bowl
Environment, Safety, Health & Quality
Following are two important things to be careful and aware of during winter weather.
In icy conditions, it is best to wear shoes or boots which are specifically designed to grip in ice and snow. An additional measure is to purchase a set of snow and ice traction cleats, a product that can be pulled on over most shoes and is designed to add additional gripping power to icy surfaces.
Another precaution is awareness surrounding ice and packed snow falling from buildings and structures. There have been reports of serious and fatal injuries received from such circumstances. In one case, a woman was struck by ice that slid off the building she was leaving as she shut the door; she suffered near life-threatening injuries. It is advisable to avoid areas where such conditions might occur. In many cases, city and building managers will cordon off higher risk areas. Employees should always be aware of their surroundings, and if you observe an unsafe condition, avoid the condition and contact an ESH&Q Safety Representative, Safety Warden or Facilities Management. If in doubt about who to contact, report the situation to your immediate supervisor or manager.
Computing and Networking Infrastructure (CNI)
E-mail Outage and Reconfiguration Begins Friday, March 20, 10 p.m.
The location of e-mail folders is being changed. Currently, JLab account holders have e-mail folders that are stored in their home directories (/home/user on Unix or J: drive on Windows). The reconfiguration will move these folders out of account holders' home directories and place them on a standalone, isolated file system. Account holders will not have direct access to this new file system. All access to these folders will require an IMAP mail client (i.e. Thunderbird, Pine configured as an IMAP client, etc). Further information about this reconfiguration will be available on the CNI group web page as the date approaches.
jlab.org Alias Change
CNI Maintenance Period Set for Tuesday, March 17
Mathematica 7 Now Available
2009 Benefits Open Enrollment Ends Today
Daylight-Saving Time Begins March 8
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