SLAC Today is available online at:
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In this issue:
Making Heads or Tails of Comet Dust
Science Today: Towards a Global Effort on ILC Emittance Preservation Studies
Take Your Career to the Top!

SLAC Today

Thursday – March 9, 2006
(Image - Stardust probe - courtesy of NASA)
NASA's Stardust gathered material from the tail of a comet in January 2004 and returned to earth in January 2006.

Making Heads or Tails of Comet Dust

by Erik Vance

Last week, a team of SSRL researchers began analyzing particles taken from the tail of a comet.

The particles came from the Stardust NASA mission, which clipped the tail of comet Wild 2 (pronounced Vilt). Comet particles skidded through ultra-light aerogel and remained stuck there for the journey back to earth. 

SLAC is one of many laboratories identifying elements in the samples, which arrived from NASA in thin aerogel slices.

“We are very excited to be mapping out the elemental abundance of the comet particles,” said SLAC's Sean Brennan.

The purpose of the mission was to catch ancient unspoiled material from the tail of the Wild 2 comet that might tell about the birth of the solar system. As it is, scientists know very little about what makes up interplanetary material.  Read more...
(Daily Column - Science Today)

Toward a Global Effort on ILC Emittance Preservation Studies

by Jeff Smith

(Photo - Jeff Smith)The International Linear Collider (ILC) requires ultra-small emittances, or beam sizes, to maintain its high luminosity. After exiting the damping ring, the beam is quite small. But it then must travel many kilometers while being accelerated before it finally reaches the interaction point. All physics results at the ILC are dependent on preserving the small beam size of 5 nanometers—about the size of a hemoglobin molecule. To achieve this, the machine components must be aligned with extreme accuracy. An offset larger than 1/10th of a human hair can completely upset the science. This far exceeds the capability of conventional surveying techniques.

Therefore, more sophisticated methods called Beam-Based Alignment (BBA) must be used. In BBA, the beam itself is used as the diagnostic tool. BBA has been used extensively before, but the precision and lengths involved in the ILC are unprecedented. As a result, very detailed simulations are required to develop and confirm the performance of these BBA algorithms.

A global effort has begun to critically analyze these BBA techniques and crosscheck their performance in the presence of both static and dynamic sources of misalignment. To do this, we are using various simulation codes from numerous laboratories from around the world including CERN, Cornell University, DESY, Fermilab and SLAC. These programs simulate the motion of the particle beam as it passes through the ILC. After various types of misalignments are introduced into the ILC computer model, the BBA algorithms are applied and the resultant beam size is calculated. We have currently completed a first stage of crosschecking and are beginning to get into the details of the various BBA algorithms.

Take Your Career
to the Top!

By Pauline Wethington

(Image - mountain peak)

Yosemite National Park's El Capitan.
Image courtesy of Delicia Gipson

Each year, SLAC selects one employee as the recipient of the Alonzo W. Ashley Career Development Fellowship. The fellowship was created in 1999 in honor of Al Ashley.  During his 30 years of service to SLAC, Ashley promoted diversity and encouraged career development for employees and career exploration for talented students.

This one-year fellowship is an opportunity for SLAC employees to further develop their careers while contributing to the mission of the lab. The fellowship can help employees develop and implement programs and projects, explore new job opportunities, and take time off to further their education.

This fellowship must take place between October 1, 2006 and September 30, 2007. To be eligible, you must:

• Have been a SLAC employee for at least three years
• Have a demonstrated interest in promoting diversity at work or in the community
• Be able to manage time
• Have your supervisor’s approval

Don’t miss this opportunity to impact your career, your community, and SLAC! Contact Pauline Wethington (x4559 or lean@slac.stanford.edu) by Monday, March 13 to attend an application workshop. Applications are due June 30, 2006. Workshop space is limited, so don’t delay!

More information


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(Photo - Owl hatchlings)

Great Horned Owl hatchlings are now visible on End Station B. The owls are nesting on a ledge several hundred feet in the air, well-protected from predators but still in plain sight. Photo by Diana Rogers. (Click on image for larger version)

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