Jefferson Lab Weekly Briefs May 14, 2008

Jefferson Lab Weekly Briefs

May 14, 2008

12 GeV Upgrade

For the GlueX detector in Hall D, the dominant contributions to the particle detector rates come from background processes that are not of interest for the physics measurement. A so-called "Level-1 trigger" must be created using the electronics and data acquisition systems to select only particles of interest and reduce the rate of stored information from several millions of particles per second down to less than 200,000 for high luminosity running. A recipe, or trigger algorithm, to accomplish this was recently studied using a full GEANT detector simulation that incorporates realistic detector geometry and responses, and the trigger electronics performance. This is implemented on the electronic signal level using the new VXS-based Flash Analog-to-Digital Converters (ADCs) in conjunction with other special VXS-based modules for the Hall D trigger developed by the JLab fast electronics and data acquisition groups. The overall Level-1 trigger rate thus simulated results in a rate of 150,000 particles of interest per second, while maintaining close to 100 percent efficiency.



Hall A successfully completed experiment E04-007 (Electroproduction of Pi-Zero near Threshold) on May 8. Installation of E08-007 (The Proton Form Factor Ratio at Low Q2) is proceeding, and it is expected that the experiment will begin taking data by May 15.

In Hall-B, g12, the experiment for studying cascade baryons and exotic mesons, continues to run smoothly. A CLAS12 systems review took place May 7-9. It went extremely well. All 12 presentations got excellent responses. The review committee did not have any recommendations or comments for CLAS12.

In Hall C, during production running for E04-108, the measurement of GEp/GMp and high Q2, the vacuum in the target scattering chamber started deteriorating. Before the vacuum reached unacceptable levels, beam delivery was paused, and radiation levels were allowed to decay for two days. The O-rings on the chamber were replaced over the weekend, and a good vacuum was obtained after pumping down the scattering chamber. The liquid hydrogen target was recooled, and production data taking resumed.


During this reporting period, Hall A ended the current portion of their experiment, while Hall C stopped taking beam for a few days to fix various problems. Through May 11, the halls divided 185 hours of beam. The accelerator delivered beam to Hall B for a few days, and then Hall C resumed taking beam towards the end of the period. The only significant accelerator problem occurred when a vacuum gasket failed during machine tuning and was quickly replaced.

Free-Electron Laser (FEL)

Work is proceeding to get components prepared for the ultraviolet FEL system installation this summer. The FEL injector group is in the process of refurbishing the FEL gun so that it can be reassembled in June for testing later this summer. Measurements and preparations are being made for more advanced beam diagnostics on the gun test stand.

Theory Center

The Color Glass Condensate (CGC) model is an effective approach to high-energy quantum chromodynamics, which allows one to calculate distributions of partons in heavy nuclei in the limit of high parton densities. Using the CGC model, a collaboration of theorists from JLab and Germany evaluated nuclear quark and gluon generalized parton distributions and the cross section of deeply virtual Compton scattering off heavy nuclear targets in the small Bjorken-x region, arXiv:0804.4424 [hep-ph]. These predictions are relevant for the physics program of the future Electron-Ion Collider and for ultra-peripheral nucleus-nucleus collisions at the Large Hadron Collider at CERN.


The magnet measurement group has started measurements in the Test Lab on the first eight of a total of 26 QX quadrupoles for the FEL for the ultraviolet upgrade. Each magnet has been measured for field strength and harmonic content. The magnets are being powered by the TrimCardII power supply with a ramping protocol programmed onto a chip on the card and controlled by EPICS.

JLab's Safety Numbers

238 Days since Last Recordable Accident (JLab record: 319)
557 Days since Last Lost Workday Accident (JLab record: 557)




Environment, Safety, Health & Quality

Hurricane season begins officially on June 1. JLab has already begun its advance preparations to ensure the Lab can quickly elevate its readiness should a storm threaten our region. But employees won’t be on site here when the hurricane arrives. By the time conditions are dangerous, you’re most likely to be home, or at some alternate, safer location. Every expert on hurricane preparedness stresses the importance of planning ahead for evacuation, shelter-in-place and other options you may need to take on short notice. Here is a partial preparedness checklist provided by the National Hurricane Center:


  • Discuss the type of hazards that could affect your family. Know your home's vulnerability to storm surge, flooding and wind.
  • Determine escape routes from your home and places to meet. These should be measured in tens of miles rather than hundreds of miles.
  • Have an out-of-state friend as a family contact, so all your family members have a single point of contact. 
  • Make a plan now for what to do with your pets if you need to evacuate.
  • Post emergency telephone numbers by your phones and make sure your children know how and when to call 911.

For a full list of preparation tips, visit the National Hurricane Center Website.

Computing and Networking Infrastructure (CNI)

jlab_secure Wireless Users Must Update Their Systems Before May 15
The credentials used to create secure connections on the jlab_secure wireless network expires May 15. Before 8 a.m., the wireless servers will be updated with a new certificate. After that time, jlab_secure clients that have not been updated will not be able to connect to jlab_secure. Instructions for updating your system can be found on the Computer Center website. This change does not affect the guest wireless that relies on WEP keys that are manually updated every few months.

JLab Auger/PBS Fedora 8 Compute Farm Update
The Lab's experimental physics compute farm is transitioning to production service with Fedora 8 running PBS/Maui scheduling and resource management. Beginning Monday, May 22, the cluster will transition to friendly-user mode; if no major problems are uncovered, the cluster will transition to full production on Monday, June 2. More information is available in the batch farm wiki. E-mail comments/questions to, or for assistance, e-mail


Controlled Areas Access Announcement for JLab Radiation-Trained Workers
If you are JLab radiation-trained and haven't yet read and electronically signed the General Access Radiation Worker Permit for 2008, your JLab badge won't allow you to access radiation-controlled areas the next time you attempt to enter them. To rectify this situation, visit the Web-Based Training webpage; open the General Access RWP KD0003 document listed under Web-based Knowledge Documents. After reading the document, click the link at the bottom of the document.

TIAA-CREF June Retirement Counseling Session
The June dates for individual counseling sessions are Wednesday, June 4 and Thursday, June 5 in VARC 42. This is an opportunity to discuss the current status of your account, investment strategy and retirement goals. To sign up for an appointment, click Meetings & Counseling and follow the menu on the TIAA-CREF website.

Jefferson Ave. Scavengers Taking Anything They Can Carry
Thefts to businesses and other establishments along Jefferson Avenue have been climbing, according to reports received by Kris Burrows, JLab's security officer. Property scavengers – people looking for anything of value that can be carried away and quickly sold for cash – are targeting JLab, retail businesses and even local hospitals. An entry method attempted at JLab is to stand outside a door and tell unsuspecting individuals they need entry so they can talk to Human Resources about a job or to see a friend. Once inside, they quickly case unattended offices, conference rooms and unsecured supply areas and carry off items that can be quickly and easily sold on the street for cash. See the full bulletin on the website.

JLab Calendar of Events

May 14: JLab Run-A-Round
May 19-23: The 4th Electron Ion Collider Workshop
May 19-23: DOE ES&H Inspection - Planning Visit
May 25-31: Virginia Tax Holiday for Hurricane Supplies
May 26: Memorial Day Holiday (JLab closed)



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