2)A Practical Introduction to PSB Low Level RF

1. 1)PSB Operation Basics 2)A Practical Introduction to PSB Low Level RF B.Mikulec 9/2/2011 A.Findlay 9/2/2011

2. Introduction • A rather brief explanation of the PSB Low Level RF hardware. • How we use the PSB Low Level system and what we use it for. • What tools do we have to help us observe and measure the beam? • What tools do we have to adjust the RF parameters. • The various “types” of beam we have and some typical adjustments. • What does the future hold for the PSB Low Level?

3. What Hardware do we have in the PSB Low Level system? What’s the secret of the black, magic box????

4. What are the building blocks for the Low Level systems? How do we generate the revolution frequency? Measure the field and send to B Train Generator hardware Generate a train of pulses proportional to the measured field and distribute The RF system receives the B Train pulses and generates a frequency word to be distributed to each of the rings RF hardware The hardware for each of the rings converts the frequency word to a sine wave which is the revolution frequency for the measured field Send Sine Wave to Cavity Hardware Measure B Field Convert Frequency Word into Sine Wave Convert Field to Pulse Train Convert B Train to Frequency Word

5. What are the building blocks for the Low Level systems? • How do we generate the RF frequency? Phase Offset Function Beam/C02 Phase Discri Radial Loop (inc. Rad. Pos. Funct) PLA C04 Ejection Sync. Loop Digital Loop Processor Phase Loop Amplifier Frequency Offset Function

6. What are the building blocks for the Low Level systems? How do we add the second harmonic information? RF C02 RF C04 or RFc04 divided by 2

7. The C02 (H=1) System • The building block of the Low Level systems • Takes the frequency and phase errors or corrections and applies them to revolution frequency to generate the RF frequency • Controls the phase loop by applying the error measured between the RF and the beam • Applies the phase offset function to allow us control of the phase between the beam and the RF frequency • Applies the frequency offset function to allow us control of the RF frequency • Applies the output of the Radial Loop to the RF frequency to allow us control of the radial position • Applies the output of the Ejection Synchronisation Loop to allow us control of when the bunches are extracted • Applies the output of the H=2 phase loop to the revolution frequency when the bunch is split

8. The C04 (H=2) System • The Second harmonic system • Used to increase the bucket size (along with the C02) to reduce the space charge effect at low energy • Used as part of the controlled longitudinal blow-up • Used to split single bunches into two • The phase of this system compared to the H=1 system is one of the main tools used to perform RF gymnastics • Limited in power when high intensity H=1 beams are produced, and requires >500v programmed to avoid beam loading effects on the cavity (usually 1-2kV)

9. The C16 System • Used to perform controlled longitudinal blow-up • The harmonic number is changed during the acceleration to keep the frequency within the range 11-16 MHz • A sinusoidal modulation is applied to the frequency to provide the blow-up, this can be changed in amplitude and frequency

10. What happens you add it all up?

11. Still awake?

12. What do we use the PSB Low level for? • Bunching and capturing the beam injected from LINAC2 • Create as large a bucket as possible with the available cavity voltages • Longitudinal shaving at capture to minimize emittance • Accelerate one or two bunches • Adjusting the average radial position during acceleration • Generating longitudinal blow-up to control the bunch length • Bunch splitting and control of separation of the bunches once split • Synchronisation of bunches from ring to ring and with the destination • Generation of RF trains for kickers, dampers etc.

13. What tools do we have to observe the longitudinal aspects of the beams? • Tomoscope (see next slide) • Bunch Shape Measurement (BSM) • Samplers • OASIS • Real oscilloscopes and frequency measurement in the cage (local control only)

14. What tools do we have to observe the longitudinal aspects of the beams? Some hints and tips for using the Tomoscope Excellent online documentation available from S.Hancock & J-F.Comblin under the “Help” button…

15. What tools do we have to observe the longitudinal aspects of the beams? Some hints and tips for using the Tomoscope

16. What tools do we have to adjust the RF paramaters? • Knobs to control timings, parameters and functions • GFA Editor to edit functions • Non-PPM gain potentiometers in cage (local control only)

17. What’s the point?

18. What are the types of beams as seen by the RF systems? • Nominal H=1 with controlled longitudinal blow-up (ISOLDE, AD, TOF, EAST, LHC25A&B) • Longitudinally shaved low intensity H=1 with limited longitudinal blow up (LHCPROBE, LHCINDIV) • Nominal H=2 with controlled longitudinal blow-up and bunch splitting (CNGS, SFTPRO) • Single batch H=2+1 with controlled longitudinal blow-up and uneven bunch spacing at extraction (LHC50, LHC75 and LHC150) • Pure H=2, with 2 bunches from capture(not operational… yet)

19. 1. Nominal H=1 with controlled longitudinal blow-up (ISOLDE, AD, TOF, EAST, LHC25A&B)

20. 2. Longitudinally shaved low intensity H=1 with limited longitudinal blow up (LHCPROBE, LHCINDIV)

21. 3. Nominal H=2 with controlled longitudinal blow-up and bunch splitting (CNGS, SFTPRO)

22. 4. Single batch H=2+1 with controlled longitudinal blow-up and uneven bunch spacing at extraction (LHC50, LHC75 and LHC150) 324ns & 248ns

23. 5. Pure H=2, with 2 bunches from capture(not operational… yet) • This does not use the C02 system but bunches the beam directly with the C04 giving 2 bunches from the capture • There is no operational user that requires this at present, but measurements will be made in 2011 to define the characteristics of this beam once more

24. Synchronisation • We can be synchronised with 3 destinations, the dump, ISOLDE and the PS • ISOLDE and the dump both use the internal reference from the PSB control system, and lock the RF to this • The PS RF is master and so the PSB RF synchronises to the PS when this is the destination • We can be synchronised in H=1 or H=2 (if the bunches are equally spaced in the ring) • For an H2+1 beam we have to synchronise in H=1 to be sure that choose which of the bunches we want to extract first

25. What do the cavities need from the Low Level? • The cavities are sent the voltage programs via the Low Level buffers, but the Low Level performs no processing on these functions • The C02 cavities are sent the H=1 RF frequency for each ring • The C04 cavities are sent the H=2 RF frequency for each ring • The C16 cavities are sent the modulated RF frequency mulitplied by a harmonic number for each ring

26. What does the future hold for the PSB Low Level? • There is a consolidation program underway to upgrade the present hardware to a Digital Signal Processor based system, similar to that used in LEIR • All functions will be fully PPM • Expect much greater stability of settings with “drifts” from nominal settings greatly diminished or eradicated • The operation of this system will rely on OASIS type virtual scopes acquiring the digital data for display. This will be a major challenge to ensure that we have the capability to observe the same signals for the same user in several locations, as well as for different users with different settings

27. Who yagonna call? • Your BE-RF-CPS Low Level piquet is always available to help you! • There are 2 specialists eager to please during working hours, A. Findlay (aka Dr. Fine-Delay) and A. Blas (akaFredi)

28. NNNNNNNOOOOOOOOOO!!!!! Don’t leave me in here again!!!!