|Fig. 1: : The Linear Particle Accelerator, construction began in 1962 and the first beam was produced in 1966.  (Courtesy of the DOE)|
The Stanford Linear Accelerator (SLAC) opened in 1962 as one of 10 Department of Energy national research laboratories. Operated by Stanford University, it is the longest linear accelerator in the world and in fact, the longest modern building stretching 3,073.72 meters (1.9 miles). Electrons gain energy as they zip down the accelerator at a speed of 2.99 × 108 m/s (6.696 × 108 mph) - 99.9999999 percent of the speed of light.  Designated for research in the physical sciences, SLAC focuses its research in four main areas: The Stanford Synchrotron Radiation Light source (SSRL), The Linac Coherent Light Source (LCLS) X-ray laser, The Facility for Advanced Accelerator Experimental Tests (FACET), and Ultrafast Electron Diffraction/Microscopy (UED/UEM). 
|Fig. 2: The SLC Polarized Electron Gun.  (Courtesy of the DOE)|
The Stanford Linear Accelerator uses polarized electrons as its energy source for many of its projects. The polarization comes from an electron gun that consists of a 100-nm-thick strained gallium arsenide (GaAs) photocathode held at a negative voltage and distributed by a Titanium Sapphire laser. The Laser produces two 2 nanosecond long pulses at 120 Hz. The gun operates at up to -120 kV to produce the 7.5 × 1010 electrons per pulse necessary to power the accelerator. Overall, the process is efficient in low beam intensities with an 85% beam polarization rate. 
SLAC is a groundbreaking research laboratory powered by an efficient polarized electron system. The laboratory continues to attract thousands of scientists from around the world. The potential for discovery is extraordinary with a lab focused on innovation and operations. 
© Sarah Helgeson. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 "SLAC By the Numbers," SLAC National Accelerator Laboratory, July 2015.
 "SLAC Strategic Plan," SLAC National Accelerator Laboratory, November 2014.
 D. Schultz et al., "The Polarized Electron Source of the Stanford Linear Accelerator Center," Stanford Linear Accelerator Center, SLAC Pub 6606, August 1994.