Transverse feedback: high intensity operation, cleaning, lessons for 2012

1. Transverse feedback: high intensity operation, cleaning, lessons for 2012 Daniel Valuch for the ADT team

2. The transverse damper system • Important role in preservation of the beam’s transverse emittance • Damping of injection oscillations • Damping of oscillations driven by coupled bunch instability • Within certain limits damping external perturbances

3. The transverse damper in general • The transverse damper is a feedback system: it measures the bunch oscillations and damps them by fast electrostatic kickers • Key elements: • Beam position monitor(s) • Signal processing system • Power amplifiers • Electrostatic kickers • Key parameters: • Feedback loop gain, phase and total delay • Kick strength • System bandwidth • The one visible from the CCC: damping time

4. LHC transverse damper (ADT)

5. ADT as seen from the CCC

6. ADT as seen from the CCC • Level1: switches on the heaters, blowers and control electronics. • Level2: switches on the high voltage power supply, the system is ready for operation. • Note: The system contains 16 tetrode amplifiers. When sitting in Level2 it already consumes more than 0.5 MW of power! • Level3 (RF ON): the power system is fully activeand the beam sees any applied excitation: • Chirp signals from the BI colleagues. • RF signals from the ADT signal processing. • Cleaning/blow-up excitation.

7. ADT as seen by the experts

8. Setting up: Beam Position Module • The Beam Position (BPos) Modules processes the RF signals from the pickups and calculates an intensity independent, normalized beam position. • Gain of the BPos module must be adapted to the maximum per bunch intensity and expected orbit displacement. • Saturation levels are typically set to ~10-20% above the intended max. intensity with a 2-2.5mm displacement. • Setting up needs to be performed once for each intensity step higher than 10-20%. • Setting up for one intensity step takes around 30 min/beam/plane (could be done remotely).

9. Setting up: Beam Position Module • BPos front ends could be damaged by excessive signals: • Injecting nominal when set to pilot/ion settings. • Injecting 3e11 when set to nominal settings. • Switching off the ADT from the CCC application does not protect the front-ends from high intensity signals! • In case the ADT is not set-up for given intensity, please ask the ADT experts to “park it” safely.

10. Setting up: Signal processing unit • The Digital Signal Processing Unit (DSPU) collects data from the BPos modules and calculates the correction kick. • DSPU generates the cleaning signals. • DSPU provides data for the injection oscillation fixed display. • DSPU needs to be set up for different bunch spacings. • Currently available settings: 25 ns, 50 ns, 100 ns, 200 ns, >600 ns • Phase advance functions need to be set up when tune changes. • Typically 30 minutes/beam/plane plus editing the LSA functions. (measurement done locally in SR4).

11. ADT through the cycle

12. ADT through the cycle

13. ADT through the cycle

14. ADT through the cycle

15. ADT through the cycle

16. Injection/Abort gap cleaning • In 2011, the injection and abort gap cleaning was commissioned into routine operation at 450 GeV. • The uncaptured beam is cleaned by coherent excitation until it hits the collimators. • Q±0.01 in 15 steps, each 750 turns. • Abort gap cleaning: excitation window fixed in part of the abort gap. • Injection gap cleaning: excitation window slides and covers the next injection slot. • End 2011: Abort gap cleaning commissioned for 3.5 TeV operation. Cleaning strategy being discussed.

17. Injection gap cleaning (horizontal plane) Abort gap cleaning (vertical plane) before 1st injection Cleaning pulse • Window function 1st injection before 2nd injection Signals acquired during injection of the fill #1867 last injection prepare ramp

18. Batch selective blow-up • Batch selective excitation using wideband noise was introduced in 2011. • Successfully demonstrated creation of a fully controlled steady losses on selected bunches as well as emittance blow-up up to the aperture limit • Intention to use ADT for loss maps, aperture measurements, quench tests etc. from 2012 onwards: • Needs time for proper commissioning at the 2012 start up. • Needs new user applications.

19. Batch selective blow-up • Test from 30.10.2011: A batch of 12 bunches lost in 4 seconds. 1 sec 1 sec 1 sec

20. Bunch by bunch observation with ADT Beam Position module Digital Signal Processing Unit Multiturn application gets this buffer Injection oscillations fixed display

21. Plans for TS 2011 and 2012 run • Recabling of one system: • 7/8” coaxial cable damage during the initial installation. • Evaluation of a new type transmission line without corrugation. delta signal last batch no beam

22. Plans for TS 2011 and 2012 run • Recabling of one system • Cable damage during the initial installation • Evaluation of a new type transmission line without corrugation delta signal last batch no beam

23. Plans for TS 2011 and 2012 run • Detailed study of, and potential improvement to, the system’s impulse response. • Cleaning signals are currently exciting beam out of the cleaning window. • Detailed study of the system noise properties as a preparation for LS1 and 7 TeV run. • Feasibility study for Q measurement using the ADT data. • Residual noise method. • Witness bunches method. • ADT gain modulation within turn. • Preparation for complete recabling in LS1 (>20km of 7/8” smooth-wall coaxial cable)

24. Re-commissioning after the TS • Commissioning of the recabled system: 4 hours. • Intensity settings for 1.4 and 1.7e11 ppb: 2x4 hours. • Verification of the loop parameters (phasing, delay): 6 hours. • Commissioning of the blow-up for loss maps: 8 hours (min). • Automatic gain adjustment (pilot/nominal): ? • Re-commissioning after the TS: total 3-4 shifts.

25. Thank you…