Jefferson Lab Weekly Briefs
March 9, 2011
12 GeV Upgrade
Conventional facilities are continuing with preparations for the accelerator shutdown scheduled to start in mid-May. The Hall D construction contractor is developing an excavation plan and detailed construction schedule for the tunnel connection planned for this period. Proposals for the beam switchyard addition construction contract, which includes two new tunnel penetrations, are under review with a contract award scheduled for mid-April. The concrete pads for cooling towers, pumps and heat exchangers are being placed for the North and South Access Building low-conductivity water (LCW) upgrades, with equipment deliveries expected in April.
In Hall A, experiment E08-010 (Measurement of the Coulomb Quadrupole Amplitude in the N→Δ Reaction at Low Momentum Transfer) has been running smoothly and was successfully completed on Monday. The next experiment is E07-006 (Short Range Correlations in Nuclei using a Triple Coincidence).
The power supply for the Q-weak torus magnet was damaged by the power outages on Feb. 25. Repairs of the supply's DC current transformer electronics by Hall C and DC power staff restored operation of the magnet last week. Because of the drop in hall radiation levels while the supply was being repaired, a decision was taken to replace the leaky bellows near the beam dump. After the bellows was replaced, the beamline would not pump down. This was found to be due to a mismatch between the bellows and the beam pipe. In an overnight effort, a new bellows was fabricated by the Hall C technical group with the help of the Hall A and the Target groups, which supplied flanges.
Research Assistantship Offered
The CEBAF accelerator machine availability for last week was 81.7 percent. It was a good week for beam delivery. Beam was delivered only to Hall A. Hall B was preparing for HDIce. On Wednesday, the End Station Refrigerator tripped during a maintenance checkup, and it was quickly recovered. During Beam Studies, data were collected to improve the Q-weak beam quality. These beam studies include improving the beam transport match from Arc1 to the Hall C transport line and measuring and reducing any X-Y coupling, which is sourced in the injector.
The FEL team successfully transported light from the ultraviolet FEL to User Lab 4 last week. As that work continues, the team intends to demonstrate the capabilities of the Laser Micro-Engineering Station using UV light. The team also qualified operation of the vacuum UV spectrometer in Lab 1 for measurement of the harmonic spectrum in the near future.
Theoretical and Computational Physics
Researchers at Jefferson Lab and Trinity College Dublin have calculated to high statistical precision an excited spectrum of isoscalar mesons using lattice quantum chromodynamics <arXiv:1102.4299>, including states of high spin and, for the first time, light exotic JPC isoscalars. Isoscalar mesons, with all flavor quantum numbers equal to zero, can mix through quark annihilation and so provide a window on annihilation dynamics in QCD; using novel techniques and the Hadron cluster at JLab, researchers have overcome the long-standing challenge of efficiently calculating these annihilation contributions in lattice QCD. This work is part of a program of calculations that will provide the ab initio predictions for masses demanded by experiment and inform expected production rates for GlueX.
Environment, Safety, Health and Quality
According to the National Safety Council, in 2011, there's a vehicle crash every 26 seconds that involves a driver using a cell phone or texting.
The first 12 GeV radiofrequency system cathode power supply (CPS) has been delivered to JLab and placed in the South Linac. SL24 will be the first RF zone to be assembled by the RF group. The CPS is used to energize the eight klystron amplifiers that provide RF power to a cryomodule in an RF zone. This unit is the first of 10 to be used in the 12 GeV upgrade.
In preparation for the 12 GeV Upgrade, the Magnetic Measurement Facility (MMF) started a BB-style dipole magnet refurbishment test using all the new components needed to upgrade the 2-meter magnets from a C-style dipole to the revised H-steel style dipole. The test has been conducted with a spare magnet and simulating all the necessary steps for the magnet upgrade. The purpose of this test is to allow the MMF to make any necessary adjustments to the parts and procedures before the six-month down starts.
MMF completed all the magnetic measurements and approved a total of 57 QR-style and 57 QP-style quadrupole magnets. A total of 30 quadrupole magnets were transferred to the vacuum group to be mounted in their corresponding girders.
MMF is also conducting a magnetic test on a total of 37 vacuum chambers for the new 4-meter XP-style dipoles. The test will be ongoing for about two days.
Annual Property and Key Validation Begins March 15
This year's property validation period is March 15-April 30. Each custodian must log in to their Property Validation account and validate each item on their respective inventory list and take the Property Custodian Refresher GEN 150 training (about 5 minutes). Also during the validation period, every person who has been issued one or more JLab keys must validate each key issued to them. Further announcements will be made regarding this process once the validation period begins.
JAG Seeks Design Entries for JLab 2011 T-shirt Contest
JLab Calendar of Events
March 13: Daylight Saving Time begins