PSB RF Transverse Feedback Aspects M E Angoletta

PSB RF & Transverse Feedback Aspects M. E. Angoletta, L. Arnaudon, A. Blas, A. Butterworth, A. Findlay, M. Haase, W. Hofle, M. Jaussi, E. Jensen, P. Leinonen, T. Levens, R. Louwerse, J. Molendijk, M. Paoluzzi, D. Perrelet. (CERN) G. Kotzian, S. Kouzue, J. Sanchez-Quesada (Med. Austron) LIU Beam Studies Review 28 th August 2012

PSB RF & Transverse Feedback Aspects Introduction • • PSB Finemet® cavity test results, status and plans. PSB Digital Low Level RF beam test results, status and plans. PSB Transverse Feedback, status and plans. PSB Controls for Low Level RF & Transverse Feedback, status and plans. • PSB RF Bypasses, plans. • Summary

PSB Finemet® Cavity Test Results, Status and Plans Courtesy of M. Paoluzzi • • Test Set-up: Test 5 -cells cavity prototype installed during shutdown 2011 -2012, each gap equipped with shorting relays & wideband gap voltage divider and powered by solid state amplifiers. New Digital Low Level Beam Control prototype developed to drive cavity in full Pulse to Pulse Mode (PPM) in parallel with (synchronised) or independently of existing H=1 cavity(C 02). AVC loop developed to stabilize the Finemet® system voltage. Phase loop developed to lock the Finemet® accelerating voltage to the beam pick-up signal 5 Cells open cavity Full prototype cavity assembly

PSB Finemet® Cavity Tests Results, Status and Plans Courtesy of M. Paoluzzi Cell Impedance & RF Feedback: • Beam accelerated (40 E 10 protons) with existing RF cavity C 02 and the induced voltage on a single Finemet® cell measured both with and without RF feedback. Cell 1 gap V 1 k. V/V Beam monitor ~400 m. A/V Without RF Feedback • Cell 1 gap V 1 k. V/V Beam monitor ~400 m. A/V With RF Feedback The RF feedback reduced the induced voltage by a factor ~3(peak) at 1. 8 MHz, which is a half of what was expected with the loop gain of 16 d. B: this is thought to be due the impedance response and will require further study. Loop Gain Gap Impedance

PSB Finemet® Cavity Tests Results, Status and Plans • Courtesy of M. Paoluzzi Acceleration Test Results: The 5 -cells do not produce enough voltage to accelerate the beam for a whole PSB cycle, so the C 02 system was used in parallel to supply the voltage required to accelerate, then reduced to it’s minimum voltage for stable operation(limited by tuning loop instability) at the end of the cycle with 2 k. V on the Finemet® cavity, for example: 460 E 10 Protons accelerated, C 02=5 k. V-1. 5 k. V, Finemet=2 k. V, peak beam current measured at extraction ~6 A Vgap [k. V]V 3 2 Gap (5 Cells) - C 800 • 1 0 -1 • -2 -3 1 Turn (0. 85 A) 4 Turn (3. 7 A) -5 E-07 8 Turn (6 A) 0 E+00 t [s] 5 E-07 • One of the concerns was the interaction of the wideband gap impedance with the beam as the wake fields and gap voltage distortion can lead to instabilities. So far the beam did not seem to suffer from this effect. Beam Current and Gap Voltage Distortion: In these tests the Finemet® cavity voltage was limited to 2 k. V. Going beyond this value triggered an instability in the low level electronics that will be solved in next MDs. With 8 turns injected the beam current at extraction was ≈60% of typical PSB maximum (6 A vs. 10 A). Considering that the system can give 50% more voltage we can think of reaching the present max beam intensity with equivalent gap voltage distortion.

PSB Finemet® Cavity Tests Results, Status and Plans Courtesy of M. Paoluzzi Issues and Future Plans: • • Quality issues during the solid state power amplifier production have been identified and will be solved for next series production. Wideband RF feedback pushed the loop gain too far, and when working above 2 MHz the stability limit can be reached. Solutions being investigated: • Use of more modern power Mosfets with improved characteristics. The original 700 V cell design voltage is not achievable due to voltage saturation in the amplifiers active devices, present limit ~600 V. The solution is a different amplifier topology which is under study. Further diagnostics are required to monitor the amplifier status and will be included in the design. A second 5 -cells system will be produced in LS 1 and installed adjacent to the existing one. A new amplifier must be designed for nominal 800 V but with a preference for more voltage if possible. All 10 cells will be equipped with these new amplifiers during LS 1. Ring 4 will have a Finemet® system capable of ~8 k. V by the end of LS 1 in addition to the existing RF cavities. Beam acceleration tests with only the Finemet® system are then required. A single cell is to be installed in J-PARC Main Ring in 2013 to test the effectiveness of the Japanese Feed Forward compensation. The Feed Forward could be used in place or in addition to the fast RF feedback to handle the higher beam intensities that will come from Linac 4. • • Limiting loop gain

PSB Finemet® Cavity Tests Results, Status and Plans Courtesy of M. Paoluzzi Conclusions and Beam Requests 2012 -2013: • • The tests showed that the Finemet® system operated at H=1 can cope with a beam of 460 E 10 protons (~6 A) The accelerating voltage distortion due to beam loading does not seem to cause major instabilities under the test conditions noted It is expected that the proton intensity could be increased by ~50% if the Finemet® voltage was increased from 2 -3 k. V, beam time required to test this. If time permits, test Finemet® system as second harmonic system in parallel with the C 02 as the H=1 system, beam time required to test this. Beam Time Request For Finemet® Cavity: • 3 x ½ days per week from 1 st-20 th October 2012

Digital Low Level RF Beam Tests, Status and Plans Courtesy of M. E. Angoletta What Remains to be Demonstrated with New Digital Low Level RF? AIM: Deploy New PSB Digital Low Level RF Beam Control (4 rings) for start-up 2014, in parallel with existing system. What has been achieved with beam tests carried out in PSB ring 4 during 2012 with presently installed prototype Digital Low Level RF Beam Control System? • • Digital Low Level System (DLLS) was developed and tested for Finemet® cavity tests DLLS was developed to work in Pulse to Pulse Mode (PPM) with existing cavities and Finemet® cavity • DLLS controls were developed to use standard LSA database tools to copy, store and archive settings • Work to continue the integration of the diagnostic signals from the Low Level system into the standard CERN virtual scope (OASIS) ongoing What remains to be developed and tested in 2012 with prototype Digital Low Level system? • Complete validation of C 16 longitudinal blow-up with phase modulation on high-intensity + LHC type beams. • Complete validation of extraction synchronisation schemes, including single-batch transfer & synchronisation with PS. • Continue testing of integration into standard operational tools used for copying and archiving settings.

Digital Low Level RF Beam Tests, Status and Plans Courtesy of M. E. Angoletta What Remains to be Demonstrated with New Digital Low Level RF? Present planning would allow installation of the final Digital Low Level RF system in PSB Ring 4 by November 2012, allowing PPM tests to start with a cycle very soon afterwards and beam tests would quickly follow. Note that both hardware and software would have to be available at this point. Beam tests with final Digital Low Level RF for system validation before series production : • Frequency program, beam capture, acceleration, phase loop and radial loop. • Initial tests with extraction synchronisation. • Start with H=1 beam tests increasing intensity, but include LHCINDIV type beam. • Once H=1 tested, start adding H=2 and perhaps longitudinal blow-up using C 16, with the aim of producing a LHC 25 type beam.

Digital Low Level RF Beam Tests, Status and Plans Courtesy of M. E. Angoletta Beam Request for Completion of Tests Before LS 1 • Until end of September 2012: 3 x ½ days per week • From 20 th October until 15 th November 2012 tests with timing cycle may be requested to start commissioning of new HW & SW: 3 x ½ days per week • From 15 th November to 16 th December 2012 commissioning tests with beam: 3 x days per week • From 17 th January to 11 th February 2013 commissioning tests with beam: 3 x days per week

Transverse Damper Status and Plans Courtesy of A. Blas Status of the PSB Transverse Damper AIM: New Transverse Damper being developed for installation before the end of LS 1, but this will be available in parallel with the existing Transverse Damper system. • Upgraded power amplifiers are under development with 800 W available in place of 100 W presently, but over the same frequency range of 10 k. Hz 100 MHz. • Recent proposal to use the same Digital Low Level RF developed for the beam control also for the TFB Low Level. • Present system bandwidth is limited by filter to 13 MHz, the new system will be designed for a bandwidth of 20 MHz. What is required by July 2014? • 4 VME VXS crates (including CPUs), 8 Digital Low Level Motherboards, 8 DACs, 8 ADCs, 4 CTRV, 16 power amplifiers (controlled by external PLCs) • 8 new VME delay boards to be developed for 0 -32 ns. • RF fast clock from Digital Low Level Beam Control + optical distribution • New PLC power amplifier controls • New controls interface • New cooling water and electrical distribution

Transverse Damper Status and Plans Courtesy of A. Blas What Would Be Required For Beam Tests December 2012 - February 2013? It would be desirable to equip PSB Ring 4 in the horizontal plane so as to allow PPM testing of the proposed Damper system before LS 1, but there are several un -resolved issues: • The firmware would require re-engineering for new hardware, and it does not seem likely that the people required to do this will be available before LS 1. • There is no mother board available, and it would have to be established if it was possible to make and test one before December, but manpower to do so is also an issue. • The PPM controls interface would have to be defined and the manpower found to create it. For the above reasons, it seems very unlikely that beam tests will be requested before LS 1.

Controls for PSB Feedback Systems Courtesy of M. E. Angoletta Aim: Establish Common Method of Interfacing Final Digital LL Beam Control & Transverse Feedback. The controls interfaces are essential tools in both systems and it would be most desirable to use the same or similar methods for both feedback systems. We will require: • Application programs such as synoptic, working sets, function editor, OASIS channels & sampler type signals • Extensive alarms reporting is required, and using the standard alarms program preferred • Full PPM controls including archiving, copying between cycles and users plus remote access. • PSB/PS OP will be asked to help ensure we achieve “standard” integration and advise/help with application programs, so they remain usable for everyday operation. • The basic set-up for the final Digital Low Level system integration should be defined before the end of 2012, and completed for start-up 2014. • BE-RF-CS and BE-CO are already working on this. No dedicated beam time requested before LS 1

PSB RF By-Passes Courtesy of A. Blas There a number calculations and measurements to be done during LS 1, but new RF by-passes will only really be required before connection to Linac 4 : • Calculate if a single RF by-pass can withstand the entire beam current in the case of a radial offset (by March 2013) • Simulate the value of the impedance perceived by the beam with the 3 RF bypasses we have per flange, spaced by 120 degrees (June 2013) • Lab impedance measurements in collaboration with F. Caspers and/or J. Tan will be requested for September 2013 • Depending upon the results above, investigate the possibility of installing some new flanges before March 2014 in one or more rings for test purposes No beam time will be requested before LS 1

RF & Transverse Feedback Aspects: Summary • • • Prototype Finemet® Cavity shows great promise, HW issues mostly understood, beam request to continue tests: 3 x ½ day per week from 1 st-20 th October 2012 Further 5 -cells Finemet® to be installed during LS 1, and beam tests using only Finemet® cavity to accelerate beam reliably are required before decision can be made to commit to this system. Digital Low Level RF Beam Control beam tests are progressing well, beam request to complete tests with prototype system: 3 x ½ day per week until end September 2012 Final Digital Low Level RF Beam Control will be installed on Ring 4 and require a timing cycle for tests 21 st October- 15 th November 2012, then commissioning with beam will be requested: 3 x day per week ~16 th November-16 th December 2012, and 17 th January-11 th February 2013 It seems unlikely that it will be possible to test a single plane of the Transverse Damper with beam before LS 1, but complete system for all rings should be available in parallel with existing system after LS 1. RF by-passes are still under study and do not require beam time before LS 1.