Jefferson Lab Weekly Briefs October 8, 2008
Jefferson Lab Weekly Briefs
October 8, 2008
12 GeV Upgrade
All beam diagnostics and control system hardware designs have been completed. Two accelerator R&D tasks are complete and reports have been submitted: re-verification of the higher-order mode damping of the 12 GeV superconducting radiofrequency (SRF) cavities and the prototyping of the beam transport quadrupoles.
Vendor proposals have been received for fabrication of the superconducting accelerating cavities and klystrons for the accelerator. Questions from the potential vendors for the 4.5 Kelvin (K) coldbox were received, and the responses have been provided to all vendors.
The installation of the polarized helium-3 target is proceeding smoothly in Hall A. The assembly of the polarized target is in its final stages, as is that of the laser table above the target. First calibrations with the water cell have been made. The cool down of both High Resolution Spectrometers (HRS) has made significant progress, with the left HRS cold and the right HRS on hold.
Hall B is getting ready for the second part of the e1-dvcs run group. The DVCS solenoid magnet has been installed and cooled down. The inner calorimeter, which will detect high-energy DVCS photons at angles of 5-15 degrees, is being prepared for installation, including a laser calibration system. Groups from the U.S., France, Russia, Chile and Korea are involved in the preparations. The Saclay group is also testing a novel type of gas tracking detector, the Micromegas (Micromesh gas system) in the 5 Tesla magnetic field of the solenoid magnet. This kind of detector may be used for accurate tracking in situations with complicated space constraints and high magnetic fields.
In Hall C, installation work for the Spin Asymmetries of the Nucleon Experiment (SANE) is progressing. The major supporting components of the polarized target have been installed, and the structure to support the helium bag that contains the downstream beam has been erected. Detector preparation continues with the placement of the lucite bars in front of the BigCal lead glass calorimeter and the installation of mirrors in the gas Cerenkov detector. At MIT/Bates, the Q-weak magnet and power supply have been energized up to the design maximum of 9500 amps.
Preparations for beam operations are well underway. Optimization of the injector started, and settings for beam operations have begun to be established. All box magnets were brought up to 6 GeV power settings and cycled. RF commissioning began on Cryomodules NL11 and SL09. Q measurements began on numerous cavities. The Central Helium Liquefier (CHL) filled all cryomodules after enough helium inventory was on hand. In addition, a tour was conducted for the polarized source conference attendees.
Free-Electron Laser (FEL)
FEL staff continued high-voltage processing the gun. The team is making careful progress and are presently at 275 kilovolts (kV) en route to 370 kV. The FEL modules were all cooled to 2 K by the CHL. The Workshop on Sources of Polarized Electrons and High Brightness Electron Beams (PESP2008) held at JLab had more than 80 participants from around the world, and FEL staff heard many relevant gun presentations. Nearly every group using DC gun technology was in attendance, including major efforts at Cornell, Daresbury and KEK. Several side meetings were held jointly to advance common aspects of the technology for 500 kV guns. Several new designs are in various stages of construction and testing, and it's expected that the FEL will be able to take advantage of the worldwide effort on this. Cathode materials, high-voltage technology, and high voltage power supplies were also major topics of interest.
Using recently derived relations between spin-dependent nuclear and nucleon structure functions at finite momentum transfers, Q2, a new Theory Center paper (arXiv:0809.3998 [nucl-th]) has studied nuclear effects in the helium-3 nucleus in the nucleon resonance and deep inelastic regions. Comparing the finite-Q2 results with previous calculations in the large-Q2 limit, significant broadening of the nucleon momentum distribution functions is found, leading to additional suppression of the nuclear structure functions around the resonance peaks.
Environment, Safety, Health & Quality
Influenza is a serious disease of the nose, throat and lungs, and it can lead to pneumonia. According to the Centers for Disease Control, about 200,000 people are hospitalized and about 36,000 people die in the U.S. each year because of the flu. A flu vaccination is 70-90 percent effective in preventing infection, making it the first and most important step in protecting against this serious disease.
While there are many different flu viruses, the vaccine is designed to protect against the three main flu strains that will likely cause the most illnesses in a particular season. In addition to protecting you from getting sick from these three viruses, it can also make your illness milder if you get a different flu virus. Getting vaccinated soon after initial availability is always a good idea, and the protection you get from vaccination will last throughout the flu season.
JLab's Occupational Medicine department is now accepting appointments for flu vaccinations. Contact Johnie Banks at x7539 to set up an appointment. Note that for 15 minutes after vaccination, you should remain at JLab in the presence of other people and avoid safety sensitive activities, including driving.
Physics Nobel Prizes Awarded
Knotty String Lassos Ig Nobel: Less noble than the original Nobels are the Ig Nobels, which are awarded by the Journal of Improbable Research "for achievements that first make people laugh, then make them think." This year's physics prize went to Dorian Raymer and Douglas Smith for proving mathematically that heaps of string, or hair or almost anything else will inevitably tangle themselves up in knots.
Physics Nobel Laureate Speaks
Red Cross Blood Drive Results
Excess-Freestock Furniture Moves to New Building
JLab's Safety Numbers
28 Days since Last Recordable Accident (JLab record: 331)
JLab Calendar of Events
Oct. 13-15: Electromagnetic N-N* Transition Form Factors Workshop