First Warm Accelerator Structure Fabricated for Cold Machine
The Klystron Microwave Department has finished fabricating the first warm "L-Band" accelerator structure to fill a unique niche in the International Linear Collider (ILC) project. L-Band structures use a frequency of 1.3 GHz to accelerate electrons and positrons. For most of the ILC's 31 kilometer length, the structures are cold, functioning at a few degrees above absolute zero. But the ILC needs a warm, or room-temperature, L-Band structure just after the positron source because producing positrons generates huge amounts of heat and "capturing" them requires strong focusing.
The prototype room-temperature structure is currently being installed at the Next Linear Collider Test Accelerator in End Station B, where it will be tested with one millisecond pulses at an accelerating gradient of 15 mega-volts per meter.
"The challenge is trying to run a beam that is optimized for a long-pulse cold machine using warm structures," said Project Manager Chris Adolphsen of the ILC Experiments and Prototypes group.
SLAC has a long history of designing and building warm structures, including the S-Band structures that power the SLAC linear accelerator, and the X-band structures that were proposed before superconducting technology was chosen for the ILC.
The fabrication of this structure comes from the Klystron Microwave Department's unique capability in assembling and processing high-power RF (radio-frequency) equipment, said Department Head Chris Pearson.
Juwen Wang, Deputy Head of the Accelerator Technology Department, originated the basic RF design for the structure and Zenghai Li of the Advanced Computation Department worked out the precise details. The engineering and mechanical design was done by Erik Jongewaard and Gordon Bowden, who faced the daunting challenge of removing 25 kW of power from the structure while limiting its temperature rise to less than one degree Centigrade. Juwen and Gordon also worked as liaisons with the Klystron Department during the structure fabrication, and worked on tuning it with Jim Lewandowski.
Heather Rock Woods, SLAC Today, August 14, 2007
Above image: Some of the people who contributed to the first warm "L-Band" accelerator structure fabricated in the Klystron Microwave Department.