EPICS Meeting 2005, SLAC. Spallation Neutron Source Low-Level RF Control System. Kay-Uwe Kasemir, Mark Champion. April 2005. SNS Linac LLRF. RF Reference Line, Timing System. Klystron. Cavity. LLRF. [mW]. [MW]. Fwd. Ref.
Kay-Uwe Kasemir, Mark Champion
RF Reference Line, Timing System
SNS Utility board
Time of day, events, etc.via SNS real-time data link
SNS Timing board
TTL timing pulses
“High Power Protection Module”
Monitors power levels,arc detectors, …for fast shutdown
“Field Control Module”
40MHz FPGA-based control loop
SC Linac uses IOCs with 2xHPM, 2xFCM.Total of about 55 IOCs.
We use VXI as if it was VME
No need for VXI “slot-based” addressing
8-bit VME instead of 16-bit VXI interrupt vectors.
VME CPU on extender board cheaper than VXI slot-zero controller.LLRF Hardware
“nanoEngine”check-card computer,runs Linux & EPICS R3.14.
Xilinx Spartan FPGAXC2S150for 40MHz control loop.
OK, but at its limit:6kB of history buffer,no floating-point CPU.FCM Ancestor: SNS “Generation 1 & 2” LLRF
Cavity amplitude & phase controls
Calls up Auto-Run sequencer page
Calls up FCM “expert” pages including Adaptive FeedForward controls
Fig. 1 Beam loading in DTL6 with ~40 us, 20 mA beam induced error of 2.7% and 2 deg in amplitude and phase.
Fig. 2 Beam loading eliminated by means of Adaptive FeedForward.