• H. Ma, J. Rose
  BNL, Upton, Long Island, New York

Funding: US DOE

The National Synchrotron Light Source-II (NSLS-II) is a new ultra-bright 3GeV 3rd generation synchrotron radiation light source. The performance goals require operation with a beam current of 500mA and a bunch current of at least 0.5mA. The position and timing specifications of the ultra-bright photon beam imposes a set of stringent requirements on the radio Frequency (RF) control, among which, for example, is the 0.14 degree phase stability, and the flexibility of handling varying beam conditions. To meet these requirements, a digital implementation of the LLRF is chosen in order to be able to take the advantage of the power of precision signal processing and control that only DSP technology can provide. The initial design of NSLS II LLRF control solution is comprised of a FPGA-based basic field controller, a dual ASIC DSP co-processor directly coupled to the FPGA controller, as well as a local CPU which monitors the operation, stores the data, and facilitates the tests and development. The prototype of the basic FPGA field controller hardware has been designed. The first sample has been fabricated, and is currently being tested.

• N.A. Towne, H. Ma, J. Rose
  BNL, Upton, Long Island, New York

Funding: Work performed under contract number 126615 for Brookhaven Science Associates, LLC.

NSLS-II is a new ultra-bright 3GeV 3rd generation synchrotron radiation light source. The performance goals require operation with a beam current of 500mA and a bunch current of at least 0.5mA. The position and timing specifications of the photon beam place tolerances on the phase stability of the RF cavity fields of less than 0.15 degrees jitter. This study develops computational methods for the construction of LQG controllers for discrete-time models of single-cavity rf systems coupled to rigid-bunch beams able to meet this tolerance. It uses Matlab’s control-systems toolbox and Simulink to synthesize the LQG controller; establish resolutions of state variables, ADCs, DACs, and matrix coefficients that, in a fixed-point controller provide essentially undiminished performance; simulate closed-loop performance; and assess sensitivity to variations of the model. This machinery is applied to NSLS-II-, CLS-, and NSLS VUV-ring models showing exceptional noise suppression and bandwidth. Thoughts are given on the validation and tuning of the rf model by machine measurements, DSP implementations, and future work.