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In this issue:
Researchers Find Evidence for the Origin of Cosmic Rays
Fermilab's CDF Observes Omega-sub-b Baryon
Cyber Security Basics Course Due Thursday
SLAC Safety Note: Dosimeter FAQ

SLAC Today

Tuesday - June 30, 2009

Researchers Find Evidence for the Origin of Cosmic Rays

Studies of supernova remnant RCW 86 (above) has revealed the origin of cosmic rays. (Image courtesy of ESO/E. Helder and NASA/Chandra.)

An international team of researchers has discovered strong evidence that extremely energetic cosmic rays are born in supernova remnants.

"Cosmic rays constantly bombard the earth's atmosphere but, until now, we didn't have proof of where in our galaxy they originated," said co-author Stefan Funk of the Kavli Institute for Particle Astrophysics and Cosmology at SLAC. "That's because cosmic rays are almost entirely made of protons, which as charged particles are bent by magnetic forces as they travel to Earth. So we can't just trace a straight line back to know where they originated, like we can with light."

Instead, the researchers traced the sources of cosmic rays by indirect means.  Read more...

Fermilab's CDF Observes Omega-sub-b Baryon

At a recent physics seminar at the Department of Energy's Fermi National Accelerator Laboratory, Fermilab physicist Pat Lukens of the CDF experiment announced the observation of a new particle, the Omega-sub-b (Ωb). The particle contains three quarks, two strange quarks and a bottom quark (s-s-b). It is an exotic relative of the much more common proton and has about six times the proton's mass.

The observation of this "doubly strange" particle, predicted by the Standard Model, is significant because it strengthens physicists' confidence in their understanding of how quarks form matter. In addition, it conflicts with a 2008 result announced by CDF's sister experiment, DZero.  Read more on

Cyber Security Basics Course Due Thursday

This Thursday, July 2, is the final deadline for anyone with a SLAC computer account to complete the required Cyber Security Basics online training course. The course covers the basics of computer security: creating and protecting a password, appropriate use of e-mail and the internet, and what to do in case of a computer security incident. If you already know this information, you can challenge the quiz on the first slide. You must answer four of five questions correctly to pass.

Anyone who has a SLAC account to access SLAC information resources must take this course by July 2, 2009 or their account may become disabled. Please visit the course Web page for more information. If you have questions, please contact Marilyn Cariola (x2820) or e-mail Computer Security Training.

SLAC Safety Notes

Dosimeter FAQ

Q: Why do I have to wear a dosimeter?

A: The law requires radiation dose measurements for potentially exposed workers. Although radiation levels are low at most SLAC locations, we measure personnel radiation doses to ensure that dose levels are "As Low As Reasonably Achievable"—ALARA—and keep records that are required by the Department of Energy.

Q: Where at SLAC do I have to wear my dosimeter?

A: If you are issued one or more SLAC whole-body dosimeters, you are required to wear them while working in or visiting areas that are defined as:

  • Radiologically Controlled Areas
  • Radioactive Material Storage Areas
  • Radiation, High Radiation, and Very High Radiation Areas
  • Contamination Areas

Q: What training do I need to get a dosimeter?

A: All employee, visitors, users and subcontractors are required to take Employee Orientation to Environment, Safety, and Health training—also called EOESH training—at SLAC. General Employee Radiological Training, or GERT, is required for personnel who need unescorted access to Controlled Areas and/or Radiologically Controlled Areas. Radiological Worker Training, or RWT, is required for personnel identified as radiological workers.

For more dosimeter information, see the complete Dosimeter FAQ.


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