PSB Digital LLRF, beam acceleration & beam-induced voltage cancellation with Finemet HLRF LLRF: M. E. Angoletta, A. Findlay, M. Jaussi, J. Molendijk, J. Sanchez Quesada HLRF: M. Haase, M. Paoluzzi CERN, BE/RF Finemet® Review, 14-15 September 2015

DLLRF overview & integration Finemet® interfacing and servoloops Outline DLLRF overview & integration Finemet® interfacing and servoloops LLRF beam operation with Finemet® Results & future steps Conclusions References

PSB DLLRF systems & Ring 0 DLLRF PSB rings PS Booster: 4 rings. One DLLRF system per ring (independent). DLLRF sampling period = 10 µs “Ring 0” LLRF: additional DLLRF system connected to PSB Ring 4. Some beams (users) controlled by Ring 0 DLLRF for PSB Ring 4 Controls the Ring 4 beam in PPM with Ring 4 DLLRF. Used to validate new implementation prior deployment on all rings or for machine studies. Used for Finemet® R&D in 2014-2015. M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 1

DLLRF operation: LLRF systems Ring 4 Ring 3 Ring 2 Ring 1 Ring 0 M. E. Angoletta PSB Digital LLRF with Finemet Finemet review, 14/9/2015 2

Servoloops at h =1,2,3,5 currently operational Ring 0 LLRF layout Under commissioning Servoloops at h =1,2,3,5 currently operational M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 3

PSB ring 4 layout Finemet (10 cells) C02 C16 C04 DLLRF < 2 µs electrical delay between LLRF & Finemet (round trip). C16 DLLRF R = 25 m C04 2015 run: ferrite & Finemet®-based HLRF systems characteristics & usage.  M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 4

LLRF operation Operation (control + diagnostics) with standard tools: knobs, function editors, virtual scopes… Digital data from virtual scope can be retrieved as .csv files in original format (often: floating point). Workingset with knobs, timings, functions. Virtual scope with extracted .csv data Operators can switch between Ring 4 DLLRF (ferrite HLRF only) and Ring 0 DLLRF (ferrite + Finemet®) autonomously. M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 5

DLLRF overview & integration Finemet® interfacing and servoloops Outline DLLRF overview & integration Finemet® interfacing and servoloops LLRF beam operation with Finemet® Results & future steps Conclusions References

DLLRF-Finemet® operation Servoloops in I/Q coordinates. Currently operational harmonics h=1,2,3,5. Four additional harmonics under commissioning. h=1 & h=2 controlled with voltage programs. Phase also controlled by phase function and rotations. All other harmonics servoed to 0 V. Protection against HLRF overdrive. DLLRF controls gap relay in PPM. Intensity [E10] B field [G] Gap open Gap closed Finemet® voltage is ramped down in user-programmable time interval (typically 10 ms) @end of the cycle or if cycle is aborted. M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 6

LLRF-Finemet® power chain Picture courtesy of J. Molendijk M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 7

Finemet® servoloops: h=2 control Finemet® @h2 alignment with C04 Rotation function for beam shaping Voltage function (control in I) PID controller (integrator) Two controllers (I,Q) with same setup Protection against HLRF overdrive h=2 voltage I,Q to DSP B for phase loop implementation Rotation in forward path for servoloop operation M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 8 sa

DLLRF overview & integration Finemet® interfacing and servoloops Outline DLLRF overview & integration Finemet® interfacing and servoloops LLRF beam operation with Finemet® Results & future steps Conclusions References

LLRF operation with Finemet® (high-intensity beams) Finemet® as h=2 (reliability run, max intensity, July 2015 onwards) C02 = 8 kV, Finemet® @h2 = 7.2 kV, C04 OFF, C16 blowup Beam phase loop closed on C02 Finemet® @h2 phase programmed as function Intensity [E10] C02 detected voltage C16 detected voltage Finemet® h=2 voltage program M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 9

LLRF operation with Finemet® (high-intensity beams) Finemet® as h=1 Finemet® @h1 = 7.2 kV, C02 OFF, C04 = 8 kV, C16 blowup Beam phase loop closed on Finemet® @h1 C04 phase loop (shaping) closed on Finemet® @h1 Finemet® as multiharmonic h=1+2 C02 = 4.5 kV, C04 = 4.5 kV, Finemet ® @h1 = 3.5 kV, Finemet® @h2 = 3.5 kV, C16 blowup. At extraction Finemet® @h2 ramped to 0 V; C04 kept to 2.5 kV. Beam phase loop closed on C02 Finemet harmonics rotated to be aligned with C02 and C04. C04 phase loop (shaping) closed on CO2 Finemet® @h2 phase programmed as function M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 10

DLLRF overview & integration Finemet® interfacing and servoloops Outline DLLRF overview & integration Finemet® interfacing and servoloops LLRF beam operation with Finemet® Results & future steps Conclusions References

Results: beam results & DLLRF reliability Beam performances (beam intensity & characteristics) similar to what is obtained with ferrite cavities → see Alan’s talk. Reliability DLLRF rings 1-4 operate successfully 24/7 since June 2014 (excluded Christmas stop, 15 Dec 2014 – 2 Feb 2015) DLLRF ring 0 operated ISOLDE reliability run (July 2015 onwards), LHC-type beams & several MD cycles → see Alan’s talk. Problems July 2015: problem on ring 4 DLLRF (giga-bit links h/w fault on a board) Sometimes malfunctioning after system update. If problem cannot be solved quickly, we revert to previous version (< 30 min operation). Loose/broken cables (bad quality in stores). M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 11

Results: cavity servoloop normalised response Fixed fREV: 0.5 MHz, 1 MHz, 1.5 MHz. Servoloop harmonics: 1,2,3,5. Network analyser (NA) excites the HLRF by sweeping the band around each considered harmonic. Gap return input to NA and transfer function measured. Servoloop PID settings are those used operationally. Non-optimum phase margin 3 dB BW: ~ 16 kHz (double sided) ~ -36 dB reduction in cavity impedance (system gain) M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 12

Results: cavity servoloop step response Step response @fixed fREV (0.5 MHz, 1 MHz, 1.5 MHz) for various step amplitudes and PID gains. Measured loop BW ~ 8 kHz for gain used in operation. Red trace: voltage reference for h=1 Yellow trace: detected voltage @h=1 Green trace: Finemet® driving signal from DLLRF 2 sampling periods delay Response to a 1 kV step in voltage reference for h=1 and fixed fREV = 1 MHz. Same PID gain as for the normalised response measurement (i.e. operational settings). M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 13

Servoloop future improvements Now we’re running with only four, non-optimised cavity servoloops …and still performance with beam is satisfactory! Intensity [E10] Bfield [G] 960E10 protons accelerated with Finemet as h=1 (servoloops ON case in next slide) Several improvements are possible and already planned Additional harmonics (also with multi-harmonic LO sources scheme) Feedforward compensation table of Finemet® transfer function to increase phase margin (hence available gain). Servoloops implemented in FPGA to obtain lower group delay and larger BW. M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 14

Results: beam loading suppression Finemet as h=1 with/without servoloops @harmonics 1,2,3,5. h=1 servoed to 7.2 kV; other harmonics servoed to 0. > 900 E10 protons accelerated in both cases → strong beam loading. Vertical scale for h=2,3,5: 200 V/div Vertical scale for h=2,3,5: 10 V/div B field Servoloops OFF. 920E10 protons extracted. Servoloops ON. 960E10 protons extracted. M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 15

Results: beam loading suppression – cont’d Finemet® as h=2 with servoloops ON as used operationally for ISOLDE reliability run. Typical beam intensities ≥ 800 E10 protons. Error on Finemet® shaping voltage < 80 V Finemet driving signal Finemet® detected voltage < 60 V detected with servoloops ON @ h=1,3,5. M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 16

DLLRF future steps Short-term (2015-2016) Finalise commissioning of servoloops at additional harmonics Implement multi-harmonic HLO sources scheme Implement loops to 0 V in FPGA (lower loop delay & larger BW) Implement Finemet® transfer function compensation table. Longer term (before end LS2): LLRF adaptation to HLRF consolidation on PSB operational rings Budget already included in PSB LLRF planning (2016-2020) Same h/w type as what is deployed now. Possibly more boards, depending on requirements and development progress. Additional s/w (FPGA code, DSP code, controls integration) M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 17

Conclusions Ring 0 DLLRF has successfully+reliably controlled Finemet® HLRF. Beam loops easily adapted to Finemet® + ferrite operation. Current cavity servoloops implementation reduces cavity impedance by ~36 dB at four revolution harmonics (h=1,2,3,5). Servoloops performance improvements already planned. Adaptation of PSB LLRF to approved HLRF consolidation (ferrite or Finemet®) included in PSB LLRF EVM planning (2016-2020). Limited manpower: everybody stretched over several projects and/or machine operation! But great enthusiasm, interest for new developments & team spirit will grant successful deployment(s). Obtained performances (beam intensity & characteristics) similar to what achieved with ferrite cavities. See Alan’s talk. M. E. Angoletta PSB Digital LLRF with Finemet® Finemet review, 14/9/2015 18

Additional slides

Multi harmonic LO source Simulation results Courtesy of J. Molendijk An economic multi Harmonic LO source can be constructed for Finemet DLLRF Benefits: Uses mainly abundant DSP resources Exact phase lock between generated harmonics Enables development of a multi harmonic RF receiver and modulator.