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In this issue:
Symmetry Explains it in 60 Seconds: Magnet Quench
Science Today: Free Electron Laser Basics—An LCLS Primer
Colloquium Monday: The Global Climate and Energy Project
Reminder: LCLS Tour Today
New Uniform Fittings Required
Financial Counseling and Classes Offered on Campus

SLAC Today

Thursday - December 4, 2008

Symmetry Explains it in 60 Seconds: Magnet Quench

A magnet quench is a dramatic yet fairly routine event within a particle accelerator. It occurs when one of the superconducting magnets that steer and focus the particle beams warms above a critical temperature, bringing operations to an abrupt halt.

A quench often starts when stray particles from the beam enter a magnet’s coils, producing an initial burst of heat. Within a fraction of a second, parts of the superconducting wire in the magnet lose their ability to conduct electricity without resistance, generating more heat that quickly spreads throughout the entire magnet. The coolant surrounding the magnet begins to boil.

In the case of a large superconducting magnet, which can be several meters long and carry currents of 10,000 amps or more, the quench creates a loud roar as the coolant—liquid helium with a temperature close to absolute zero—turns into gas and vents through pressure relief valves, like steam escaping a tea kettle.

Such a quench generates as much force as an exploding stick of dynamite. A magnet usually withstands this force and is operational again in a few hours after cooling back down. If repair is required, it takes valuable time to warm up, fix, and then cool down the magnet—days or weeks in which no particle beams can be circulated, and no science can be done.

This piece originally appeared in Symmetry magazine.

(Daily Column - Science Today)

Free Electron Laser Basics: An LCLS Primer

Click for an interactive map of the Linac Coherent Light Source.

In a few short months, the Linac Coherent Light Source will start operation as the world's first hard X-ray free electron laser, pushing SLAC National Accelerator Laboratory to the frontier of photon science. Using SLAC's linac to drive a free electron laser, or FEL, the LCLS will generate X-rays an eye-popping 10 billion times brighter than the current cutting-edge technology, while simultaneously providing pulses lasting less than one millionth of one billionth of a second.

How does an FEL accomplish these feats of X-ray wizardry? Although it reaches nearly two kilometers end-to-end, the LCLS contains the same basic components as a pocket laser pointer: an energy source, a light source, a monochromater to select a single wavelength and an amplifier. The energy source provides the power, which the light source uses to generate X-rays. The monochromater and amplifier give the X-rays the ultra-bright, coherent properties of a laser.

The LCLS pulls its energy from electrons accelerated in the final kilometer of the SLAC linac. The 14 GeV electron beam is so powerful that the LCLS requires less than 0.1% of the linac's energy to create 10 billion watts in X-rays.  Read more...

Colloquium Monday

Next Monday, Stanford Professor Sally Benson will present "The Global Climate and Energy Project" at 4:15 p.m. in Panofsky Auditorium. All are welcome.

LCLS Tour Today

Today is the staff tour of the Linac Coherent Light Source. If you registered to join in, please remember your SLAC badge, closed-toe shoes and long pants for the tour. Enjoy!

New Uniform Fittings Required

SLAC has a new uniform supplier. Ameripride Uniform Service has been awarded the contract for the uniform rental and cleaning services for 2009. All SLAC personnel who used Prudential Uniform Services for uniforms (shirts and pants), coveralls, lab coats, machine aprons, shop coats, frocks or smocks will need to be re-fitted by Ameripride.

Ameripride will be at SLAC from 7:00 a.m. to 4:00 p.m. on Thursday, December 4, and from 8:00 a.m. to 12:00 p.m. on Friday, December 5, in Building 81, room 100 (the old Accounts Payable offices). Swing shift and owl shift personnel should make arrangements to make one of these times. If you will be on vacation during these dates, please leave your measurements with Gordon Scrimger (x2612).

Financial Counseling and Classes Offered on Campus

The global economy, as well as personal and retirement savings, has suffered in recent months. To help faculty and staff make informed decisions about their finances in these challenging times, Stanford Benefits has arranged an expanded number of free one-on-one financial counseling sessions. In addition, the benefits team has announced the return of financial education classes provided by Financial Knowledge. See the full announcement for details and a schedule of appointment dates available to SLAC employees.


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