One of the current programs at SLAC National Accelerator Laboratory is the Linac Coherent Light Source, or LCLS. Using the existing hardware of the last third of their linear accelerator (or “linac”), SLAC has created one of the most energetic X-ray free electron lasers (or “FEL”). Since 2009, LCLS has used this FEL to perform a wide range of experiments across all sciences, most notably ultrafast filming at the molecular scale. As requests for beam-time with this laser increases, SLAC is purposing a linac upgrade to better match this demand. This upgrade, named LCLS-II, will replace existing copper radio frequency (or “RF”) cavities with superconducting Niobium RF cavities in the middle third of the linac. With superconducting RF, the power requirements are far lower to fire each laser pulse, and can be fired thousands of times faster, thus speeding up data-gathering and thus speeds up science. Superconductors are inherently unstable, however. Due to the pressure waves of the liquid He needed and the extremely narrow bandwidth of the RF cavities’ resonance, peak performance can never be maintained without intervention. To prove that off-the-shelf hardware can be constructed to counter all of these instabilities, our team built a proof-of-concept electronic model of a control circuit. With this model, we found that by using a circuit board to accurately represent the nature of a new Nb RF cavity, we could perform all the prerequisite operations to keep the cavity in check and always at peak resonance.


Atomic, Molecular and Optical Physics | Controls and Control Theory | Electrical and Electronics | Engineering Physics | Plasma and Beam Physics | Power and Energy | Signal Processing


Joe Frisch

Lab site

SLAC National Accelerator Laboratory (SLAC)

Funding Acknowledgement

This material is based upon work supported by the S.D. Bechtel, Jr. Foundation and by the National Science Foundation under Grant No. 0952013 and Grant No. 0833353. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the S.D. Bechtel, Jr. Foundation or the National Science Foundation. This project has also been made possible with support of the National Marine Sanctuary Foundation. The STAR program is administered by the Cal Poly Center for Excellence in Science and Mathematics Education (CESaME) on behalf of the California State University (CSU).


URL: http://digitalcommons.calpoly.edu/star/254


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