Jefferson Lab Weekly Briefs
May 19, 2010
12 GeV Upgrade
The preliminary manufacturing readiness review for the solenoid magnet for CLAS12 was held in May at Wang NMR in California. This included a progress review of the machine preparations for soldering the superconducting cable to the copper stabilizer and for winding the coil. Short sample tests of the superconducting cable for the solenoid are in final stages at the University of Twente, the Netherlands, with good results to date. Production extrusion of the scintillator for the Pre-Shower Calorimeter (PCAL) for CLAS12 is underway at Fermilab. Tests showed that inserting two wavelength-shifting fibers per through-hole into each scintillator slat gave better light yield results than gluing in a single fiber, and this method was adopted for PCAL assembly. A lab for this work is nearing completion at The College of William & Mary. Tests were made of a composite rib structure that would minimize material thickness for the CLAS12 High Threshold Cerenkov Counter (HTCC), and the first eight (of 48) of the 5-inch diameter quartz-face photomultiplier tubes have arrived and are being tested.
A Hall C Safety Awareness (SAF112) training session will take place Monday, May 24, at 4 p.m. in the Counting House. Arrive promptly in the Hall C control room with your radiation badge a few minutes before 4 p.m. and make sure your Radiation Worker and Oxygen Deficiency Hazard training are both up to date.
Overall, the accelerator was running well, with low trip rates. Last Wednesday, of last week, the injector was optimized to stabilized beam. Hall D construction work caused a power outage in the East Arc on Thursday, causing about three hours of downtime. Two shifts were spent for accelerator beam studies.
The FEL team performed extended studies of transverse and longitudinal halo generation in the injector this week. The team also provided light for a photon-induced carrier transport experiment.
That the proton's structure at large distances is influenced by its "pion cloud" has been the lore of nuclear physics since the 1930s. Using the new concept of transverse charge densities in a fast-moving nucleon, theorists have now quantified the pion cloud contribution to electromagnetic structure in a manner which is model-independent and compatible with Quantum Chromodynamics <arXiv:1004.3535>. The new formulation combines results of elastic form factor measurements (Mainz, JLab) and peripheral deep-inelastic processes (COMPASS, LHC and EIC) and reveals that the pion cloud is visible clearly only at surprisingly large distances (~2 fm).
Facilities Management and Logistics
A weekend power outage is scheduled for the F-Wing of CEBAF Center. The outage is set to start at 7 a.m. on Saturday, May 22, and end Sunday morning. The purpose of this outage is for York River Electric to install an 800 Amp circuit breaker in the electrical room switchboard. Note that only the F-wing section is to have the outage; the rest of CEBAF may function as normal. If you have questions about the outage, contact Richard Williams at x7025.
Environment, Safety, Health & Quality
On March 15, U.S. Transportation Secretary Ray LaHood announced a new cycling policy: "People across America who value bicycling should have a voice when it comes to transportation planning. This is the end of favoring motorized transportation at the expense of non-motorized. We are integrating the needs of bicyclists in federally-funded road projects. We are discouraging transportation investments that negatively affect cyclists and pedestrians. And we are encouraging investments that go beyond the minimum requirements and provide facilities for bicyclists and pedestrians of all ages and abilities."
In honor of National Bike Month, here are a few safety tips for cyclists gleaned from http://bicyclesafe.com/:
Colloquium and Public Lecture
Clean the Bay Day Seeks Volunteers
JLab's Safety Numbers
21 Days since Last Recordable Accident (JLab record: 331)
JLab Calendar of Events
May 26: Colloquium and Public Lecture
Summer Education Calendar