Digital Low Level RF control for Advanced Light SourceQiang Du1, Lawrence R Doolittle1, Kenneth Baptiste1, Michael Betz1, Massimiliano Vinco1, Gang Huang1
1Lawrence Berkeley National Laboratory, Berkeley, CA 94720
Abstract
A digital LLRF control system has been built and installed as part of the Storage Ring RF system upgrade project at Advanced Light Source in LBNL. In order toenable a configurable two klystrons driving two cavities operation, the system implements low-noise RF front-end, non-IQ digital receiver/digitizer, double rate feedbackcontrol loop, and 42 channels distributed RF monitor with integrated fast interlock across multiple chassis and subsystems. Chassis level test shows > 78 dB isolationbetween feedback channels, and 128 fs RMS time jitter [10Hz, 50MHz] at Klystron drive ports. Preliminary test result shows RF field stability of 0.01% in amplitudeand 0.01◦ in phase at 499.654 MHz for the band above 1 Hz (no beam).
System setup: LLRF controller + RF monitors + Fast RF interlock
ADC PHY
ADC PHY
ADC PHYX12
14-bit ADCADS62P49
14-bit ADCADS62P49
229.0MSPS
229.0MSPS
14-bit ADCLT2175
14-bit ADCLT2175
14-bit ADC4X3 CHAN
LT2175
114.5MSPS
14-bit ADCLT2175
14-bit ADCLT2175
14-bit ADC4X3 CHAN
LT2175
114.5MSPS
14-bit ADCLT2175
14-bit ADCLT2175
14-bit ADCLT2175
14-bit ADC4X4 CHAN
LT2175
114.5MSPS
LO458.0 MHz
LO458.0 MHz
LO458.0 MHz
LO458.0 MHz
... X12
LO458.0 MHz
LO458.0 MHz
... X12
LO458.0 MHz
LO458.0 MHz
... X16
ADC PHYX12
ADC PHYX16
Cavity1 Cell
Cavity2 Cell
Cavity1 RevCavity2 FwdCavity2 RevBPMMaster Osc
Cavity1 Rev
Kly1 Drive RevKly1 Out FwdKly1 Out RevCirc1 Load FwdCirc1 Out FwdCirc1 Out Rev
Kly1 Drive Fwd
Kly2 Drive RevKly2 Drive Fwd
Kly2 Out FwdKly2 Out RevCirc2 Load FwdCirc2 Out FwdCirc2 Out Rev
Magic T In RevMagic T Load FCirc2 Load RevTest Load 1 FwdTest Load 1 RevTest Load 2 Fwd
Magic T In Fwd
Test Load 2 Rev
LO GEN
114.5MHz
229.0MHz
458.0MHz499.64MHz
Master Oscillator
Circular RAM(64k)
DDS LO(IF/CLK = 2/11)
DLO I
DLO Q
DLO phi
DDC
DLO Q
DLO I
FIR
FIR
Cart2Polar
CORDIC
Cart2Polar
CORDIC
ClipLinerize
Interpolate
P
A
Cart2Cart
CORDIC
Q
I
PHS
phs set
AMP
amp set
DLO phi
DAC PHYEN
offset
14-bit DAC
DAC3283
229.0MSPS
LO458.0 MHz
Kly2 Drive
Permit
ClipLinerize
Interpolate
P
A
Cart2Cart
CORDIC
Q
I
PHS
phs set
AMP
amp set
DLO phi
DAC PHYEN
offset
14-bit DAC
DAC3283
229.0MSPS
LO458.0 MHz
Kly1 Drive
Permit
runtimedecimation
2nd orderCIC
Permit
DDC
DLO Q
DLO I
DDC
DLO Q
DLO I
DDC
DLO Q
DLO I... X12
Aurora 8b10b
GTXduplex
Integral
Ki
Kp
-SP
AMP/PHS PI
Circular RAM(64k)
runtimedecimation
2nd orderCIC
Permit
DDC
DLO Q
DLO I
DDC
DLO Q
DLO I... X16
Aurora 8b10b
GTXduplex
DDC
DLO Q
DLO I
DDC
DLO Q
DLO I... X12
DDS LO(IF/CLK = 2/11)
DLO I
DLO Q
DLO phi
Aurora 8b10b
GTXduplex
Aurora 8b10b
GTXduplex
Fast RF
Power Interlock
(14)
Fast RF
Power Interlock
(28)
RISC-VCPU
UART
GBE MAC
GBE MAC
GBE MAC
Circular RAM(64k)
MODBUS RTU - TO PLC
CMODSerial
&
CMODSerial
ARC Status(16)
ARC Pwr Status(16)
&
Config
RF Permit
LLRF FPGA
RFMON FPGA Interlock FPGAField IO FPGA
Digital LLRF chassis
Figure: LLRF chassis assembly
Features
I 74.3 dBFS signal-noise ratio on feedback channels, 72.1 dBFS on monitorchannels;
I > 78 dB channel isolation between feedback channels;
I 128 fs RMS time jitter [10Hz, 50MHz] at Klystron Drive ports;
I < 3.4 microsecond total feedback group delay;
I < 0.01% amplitude and phase stability (preliminary);
I 42 channels distributed synchronous digital oscilloscope with deterministiclatency;
I 1.45 microsecond maximum RF power interlock latency;
I Programmable feedback and interlock configurations with respect tooperation modes;
I Non-OS, Non-Ethernet, direct hardware integration with high power RFand personnel safety interlocks;
I EPICS and various diagnostic software support;
I Fully open source from hardware, gateware, firmware to software design;
Status
As part of ALS Storage Ring RF System upgrade project, the digital LLRFcontrol system was commissioned in March 2017 and enabled nominaloperation with desired preliminary performance. Further optimization isplanned together with additional upgrades in the FY 2018.
Digital Low Level RF control for Advanced Light Source LLRF17 Workshop, Barcelona, Spain, Oct. 2017Q.Du, L.R Doolittle, K.Baptiste, M.Betz, M.Vinco, G.Huang P-46
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