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Kotturi, K. D.

Paper Title Page
MOPAS061 LCLS RF Gun Feedback Control 572
  • C. H. Rivetta, R. Akre, P. Cutino, J. C. Frisch, K. D. Kotturi
    SLAC, Menlo Park, California
  Funding: Work supported by Department of Energy (USA) under contract # DE-AC02-76SF00515

The LCLC RF gun requires a water cooling thermal system to tune the resonance frequency of the cavity to 2856.03MHz. The RF system operates in pulsed mode with bursts of 2.5usec at a repetition rate of 30-120Hz. The thermal system operates in combination with the low-level RF system to set the operation point of the cavity. The Low-Level RF system controls the magnitude and phase of the cavity voltage and define slow signals to the thermal system. The thermal system operates by pre-heating / pre-cooling the water and mixing both channels to achieve the optimal temperature to control the cavity resonant frequency. The tune control of the RF gun include two systems with different dynamics. The dynamics of the thermal system is slow while the RF system is fast. Additionally, different actuators in the system present limits that introduce non-linearities to be taking into account during the start up process . Combining these characteristics, a controller is designed for the resulting hybrid system that allows convergence in large for all the operation conditions and achieve the performance in the magnitude and phase of the cavity voltage required around the operation point.

WEPMS036 LCLS LLRF Upgrades to the SLAC Linac 2421
  • R. Akre, D. Dowell, P. Emma, J. C. Frisch, B. Hong, K. D. Kotturi, P. Krejcik, J. Wu
    SLAC, Menlo Park, California
  • J. M. Byrd
    LBNL, Berkeley, California
  Funding: DOE

The Linac Coherent Light Source at SLAC will be the brightest X-ray laser in the world when it comes on line. In order to achieve the brightness a 100fS length electron bunch is passed through an undulator. To creat the 100fS bunch, a 10pS electron bunch, created from a photo cathode in an RF gun, is run off crest on the RF to set up a position to energy correlation. The bunch is then compressed chicanes. The stability of the RF system is critical in setting up the position to energy correlation. Specifications derived from simulations require the RF system to be stable to below 100fS in several critical injector stations and the last kilometer of linac. The SLAC linac RF system is being upgraded to meet these requirements.