Jefferson Lab Weekly Briefs January 23, 2008
Jefferson Lab Weekly Briefs
January 23, 2008
12 GeV Upgrade
A full-scale, wooden mock-up of a segment of the planned Hall B CLAS12 has been constructed in the physics storage building (see 12 GeV Updates page) mimicking two coils of the torus magnet and one sector of the Region-II drift chamber. The mock-up has been used so far to test Region-II drift chamber mounting and to verify maintenance access and will be used to optimize cable routing. Regions I and III will be added to the mock-up in the future.
Hall B continues to run the Frozen Spin Physics Program with the FROST polarized hydrogen target. The target continues to operate very well at high polarization (80 percent on average). At the same time, linearly polarized photons are being used to measure double and triple (for strange particle production) polarization observables as a means to search for yet undiscovered new baryon resonances.
Free-Electron Laser (FEL)
FEL staff has made good progress on processing the gun test stand gun cathode structure over a 24-hour schedule, processing to more than 415 kilovolts (kV) on the high-voltage power supply. An automated processing script that has made HV processing an easier and more controlled process has also been commissioned. Also, good progress is being made in getting the Master Laser Personnel Safety System wiring completed.
The Deeply Virtual Compton Scattering (DVCS) process allows us to study Generalized Parton Distributions (GPDs) of quarks and gluons in nucleons and nuclei, thereby helping us to construct three-dimensional images of their internal structure. Modeling nuclear GPDs in terms of proton and neutron GPDs, a recent paper (arXiv:0801.3235 [nucl-th]) calculated the so-called beam-spin DVCS asymmetry for a wide range of nuclear targets,and considered the cases when the target nucleus is intact (coherent process) or when it excites or dissociates (incoherent process). The JLab DVCS experiment on helium-4 will be able to test these predictions in both the coherent and incoherent regimes and thus constrain the poorly-known neutron GPDs, as well as probe modifications of nucleon GPDs in the nuclear medium.
JLab's Safety Numbers
126 Days since Last Recordable Accident (JLab record: 319)
JLab Calendar of Events
Jan. 25: American Red Cross Blood Drive, 10 a.m.- 4 p.m.
Adopt-A-Spot Litter Pickup event on Jan. 25
Environment, Safety, Health & Quality
Several recent local winter weather events point out the importance of being aware of what specific winter weather terms actually mean. Knowledge of winter forecasting terms will provide information as to which driving conditions to expect. The following is a brief description of winter driving forecast terms and their meaning:
Armed with the knowledge of expected conditions, you as the driver can answer one of the most significant questions regarding winter driving: Is this trip necessary? There are many options available prior to a trip in these weather conditions. Can the trip be delayed until road crews have improved traction? Can multiple trips be combined so that exposure to the traffic environment is diminished.
Welding of Exotic Alloys Lesson Learned
INL staff used standard welding practices for a proprietary alloy (high in nickel, chromium and cobalt content for corrosion resistance and elevated temperature strength) in vessel fabrication. Initial welding attempts were not completely successful, due to tensile strengths failing at less than minimum strength. Also, problems were encountered with heat treatment processes. INL analyzed these welding problems as resulting from the "super alloys" allowing design vessels to operate in previously unachievable environments. INL followup actions included allowing welders to practice on new materials to become familiar with their characteristics and exercising great care with heat and cleanliness controls. For additional JLab-specific welding information, contact Brian Murphy of the Quality Assurance and Continuous Improvement Department at x5515 or firstname.lastname@example.org.
Computing and Networking Infrastructure
Automatic Installation of Microsoft Office
E-Mail changes to impact users of Pine, Mutt and mailx clients
The changes that will take place are two-fold:
Additional changes that will affect all users and where you store your e-mail folders will take place later in the spring/summer. Announcements will be made regarding those changes at a later date.