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A New Frequency Program in the CERN Proton Synchrotron

By Magnus Sundal. A New Frequency Program in the CERN Proton Synchrotron. «RF Manipulations and LLRF in Hadron Synchrotrons» GSI Darmstadt, 20. March 2014. Thanks to: Heiko Damerau, Damien Perrelet, Daniel Oberson, Andrea Villanueva, Maciej Lipinski et. al. Content.

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A New Frequency Program in the CERN Proton Synchrotron

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  1. By Magnus Sundal A New Frequency Program in the CERN Proton Synchrotron «RF Manipulations and LLRF in Hadron Synchrotrons» GSI Darmstadt, 20. March 2014 Thanks to: Heiko Damerau, Damien Perrelet, Daniel Oberson, Andrea Villanueva, Maciej Lipinski et. al.

  2. Content • The PS frequency program • Currentfrequencyprogram implementation • The B-train & White Rabbit • Requirements • The newfrequencyprogram • Test results • Conclusion and outlook

  3. The PS frequency program • B-field and revolution frequency information needed for various subsystems • Especially important as reference for RF beam control • Transmission protocol to be changed with renovation of B-train system • PS chosen for first White Rabbit implementation • *for beam current measurement

  4. The PS frequency program • Function • Generate the revolution frequency, frev based on the following parameters: • B = Magnetic field strength of dipole magnets • Particle type (charge Ze, mass m) • Frequency program for different particle types can be generated by scaling from proton frequency program • PS specific solution: • Static B to f table calculated from beam based measurements and corrections • Scaling input (~charge/mass) • Resolution loss due to scaling • S. Hancock, A fit-based frequency programme for the PS, • http://cds.cern.ch/record/1072486/files/newfprogp%2Bion.pdf

  5. The PS frequency program • Protons: • Rest mass mp = 938.27 MeV • Charge = e0 • Pb54+Ions: • Rest mass mi = 193.72 GeV • Charge = 54e0 • New particle types to come: • 40Argon11+(2014) and 129Xenon39+

  6. Current frequency program implementation • Multiple NIM modules • Dedicated frequency program for each particle type • dB/dt (rate of change) transmitted separately: • fmax=300 kHz (3 T/s) • 10 µT resolution • Up-/down-counter as integrator • Reset to zero field between cycles necessary

  7. The B-train • Old system: • Instant distribution of Bdot (rate of change of B-field) • Reset signal • End of cycle = back to zero • 10 µT resolution • New system: • Distribution of B, Bdot, G & S via White Rabbit • 50 nT resolution • Real-time measurement and distribution of B-field from reference dipole magnet • Draft frame format for PS tests • Daniel Oberson, TE/MSC/MM, 2013

  8. The White Rabbit • Key points: • Ethernet based time synchronous network • Sub-ns accuracy/precision for synchronization • Deterministic low-latency data transfer • Existing hardware implementation • «Backwards compatible» with standard Ethernet • Maciej Lipinski, ALBA 2012, Warsaw

  9. The White Rabbit Standard hardware from BE/CO/HT • White Rabbit Switch (WRS) • 18 ports, Gb/s, VLAN, HP MAC-address register, deterministic low-latency, transparent • Simple PCI-E FMC Carrier(SPEC) • PCI-E, SFP, 1xFMC slot, 32 Mb SPI flash, 2 Gb DDR3, 1 Xilinx Spartan 6 FPGA • Simple VME FMC Carrier(SVEC) • VME 64x, SFP, 2xFMC slots, 128 Mb SPI flash, 4 Gb DDR3, 2 Xilinx Spartan 6 FPGAs

  10. Requirements • Solution: • Scalable particle support from 1 to 1/10 charge/mass ratio of protons • B to f table:Resolution=640 nT15.6 x higher • White Rabbit compatible • Distribution of frev follows beam control standard • B to f table with20 x increase in resolutionold resolution= 10 µT • Support for different types of particles • Compatible with B-train distribution ANDexisting beam control

  11. The new frequency program Hardware • Choice: • SPEC for development-SVEC for final implementation • Develop simple custom FMCs to meet RX & TX link req. • Standard CO hardware used for B-train distribution and chosen by all other WR users

  12. The new frequency program Hardware • Flexible support of particle type (resolution) • Multiple distribution options • Easy implementation (VME x64) • No integration functionality necessary • SPI EEPROM to store B to f table. SVEC’s advantage with large configuration memory

  13. The new frequency program Specialized hardware • FMC-DTRX-4CHA (CVORB Receiver and transmitter) • Low-bandwidth transceiver • Carrier side: LVTTL • Link side: RS-485 diff. • Compatible with CVORB function generator format • Reception of correction function • Matthieu Cattin, «GFAS like Serial Transmission Format», (https://edms.cern.ch/file/1071129/1/GFAS_like_serial_transmission_format.pdf) Prototype validated • FMC-DTX-4CHA (frevTransmitter) • High-bandwidth transmitter • Carrier side: LVTTL • Link side: Differential line driver compatible with existing 40 Mb/s serial transmissions • Distribution of frev to existing beam controls Prototype validated • Joao Bento, (https://edms.cern.ch/file/434163/1/Note.doc)

  14. The new frequency program Firmware

  15. The new frequency program Firmware • address.vhd (from B-field to B to f table address) • LSB cut for resolution match +MSB cut for excessive range • Multiplication for frequency values divided over 3 bytes

  16. The new frequency program B f table generation • Procedure (Xilinx FPGA): • Export B to f table in list as binary file with Wolfram Mathematica • Use ISE iMPACT to generate an .mcs file containing firmware andB to f table as “non-configuration data”

  17. The new frequency program B f table read cycle spi_controller.vhd • Master-single slave SPI I/F • «RAM»-functionality • 40 MHz SPI clock • Flash EEPROM already implemented in SPEC/SVEC • |← 2 µs delay < 1 turn →| • Fully validated - tested under realistic conditions

  18. Test results VHDL Modules SPI Controller • Initial issues with latency between FPGA and EEPROM • Latency caused byhardware multiplexers Now fully functional

  19. The new frequency program Firmware Encoders/decoders in VHDL • Distribution of frev : • 23 bit Manchester encoded protocol • 40 Mb/s • J. Bento, A 40 Mb/s Serial Link System for Cern – PS & PSB • CVORB Correction: • 16 bit «pulse length» encoding • 3.2 Mb/s • M. Cattin, GFAS Like Serial Transmission Format

  20. Test results Transmission • Transmission latency test with B-field frames only • 64 byte Ethernet packages • 250 kHz frame rate • 1 B-frame broadcasting node (TE/MSC/MM) • 1 receiving node • Output pulses through FMCs • Effect of frame collision on latency • 1 additional node broadcasting the I-frame (current from main power supply) with 1 kHz frame rate

  21. Test results Transmission • Latency (1 broadcasting node) • Data rate: up to 250 kframes/s • Measurements done with a Frequency & Time interval analyzer and Chipscope Histogram: 1’000 samples 100 meas ↑ 0 meas 100’000 samples 3.978 µs → 4.378 µs • Discrete latency distribution (multiples of 62.5 MHz clock)Ongoing investigations in collaboration with CO (White Rabbit dev.) • Daniel Oberson, TE/MSC/MM,2014

  22. Test results Transmission • Latency (2 broadcasting nodes) • Data rate: up to 250 kframes/s • Additional latency caused by queuing in switch Histogram: 1’000 samples 100 meas ↑ 0 meas 1’000’000 samples 3.9516 µs → 4.3516 µs Time latency vs time: 1’000 samples 6 µs ↑ 3.5 µs • Andrea V. Villanueva, TE/EPC/CCE, 2014 0 → 8.14025 ms

  23. Test results Transmission • Time between frames • Data rate: up to 250 kframes/s • Corresponds to measured latency Histogram: 1’000 samples 250 meas ↑ 0 meas 1’000’000 samples 3.6755 µs → 4.2755 µs • B-field rate of change, worst case scenario : 3 T/s → 5 µs = 15 µT • Latency < 5 µs : no critical effect on operation

  24. Test results Total latency introduced by frequency program: • 1 broadcasting node: • Tfprog~ 2.5 µsTtrans~ 4.3 µs = 6.8 µs • 2 broadcasting nodes: • Tfprog~ 2.5 µsTtrans~ 5.2 µs = 7.7 µs • |← fprog latency →| • Received B-frame • frev distribution

  25. Conclusions and outlook • New flexible frequency program for the PS developed for protons and ions: • Based on WR-transmissions of magnetic field • Data rate of 250 kframes/s • 2 FMCs for adaptations to existing hardware developed, prototypes fully functional • Successful validation of B-field distribution via White Rabbit • Full design successfully tested under realistic conditions with sending part of B-field distribution by TE/MSC/MM

  26. Conclusions and outlook • Serves as intermediate solution before implementation of a fully digital beam control system • Outlook: • Migration of firmware from SPEC to SVEC • Commissioning and implementation into the PS beam controls • Tests with beam in 2014

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