LHC Instrumentation Commissioning: Beam Monitoring and Calibration

1. Beam Commissioning of LHC instrumentation Chamonix XIV, January 2005 H.Schmickler on behalf of the AB-BDI group

2. For information: Outline of Talk of B.Holzer (Wednesday) • Beam Position Monitor (BPM) System • Polarity errors • Testing of electronics • BPM Database issues • Timing issues • Beam Loss Monitor (BLM) System • Hardware set-up & testing • Calibration • Threshold determination • Emittance and Current Measurement Systems • Sector Test • Summary

3. Outline of this Talk • Prerequisites for a working instrumentation • Action areas:- design office support- coordinated effort for application programs • Two major lessons learnt from LEP:- Independence of beam synchronous timing- Deadlocks during hardware/software developments • Bringing the instruments (machine) to their nominal performance- orbit system- beam loss monitor system- time resolved tune and chromaticty measurements- beam current measurements, lifetime calculations- profile measurements- others • conclusions

4. Prerequisites (same slide as last year) Working and exploitable instruments need:- sensors and electronics : AB-BDIdetails see AB-LHC review; recurrent problem: Design support- controls infracstructure : AB-CO, in progress- RT software and expert tools: AB-BDI-SWwill be based on FESAII framework • Operational application programs AB-CO + AB-OPwork needs to be organized soon (that is the text of last year)work needs to be organized now (see following slides)

5. Design effort still needed • There are still major BDI components, for which the mechanical design is not done / finished. • The situation was similar at Chamonix 2004. • After the workshop a significant improvement in design office support was notable. • With the QRL problem higher priorities defined, present support insufficient • Without the requested support - some special BPMs (= special BPMs of the normal orbit system and special BPMs for tune measurements)- the synchrotron light telescope- the wire scannerswill not be ready

6. Prerequisites: Software effort • Example: Time resolved chromaticity measurementsat day 0: We should not count on PLL tune tracking and momentum modulation  use head-tail method (despite emittance growth) • SPS application program:- needs visual inspection of result- gives chromaticty as number onthe screen- needs:automation, integration into a measurement system… Solution: Define for the key system “System commissioners”and start definition, design and coding of the application programs

7. Lessons learnt from LEP (1/2) • Provide reduced functionality of instruments without beam synchronous timing (BST)- BPM-system: works without BST, but no bunch/turn identification, reduced noise immunity- BLM system: most of the system acquires data in an asynchronous 1ms rhythm- BCT DC: no timing- BCT BB: needs beam synchronous timing, was a problem for the downstream BCT in TI8, people are working on a input filter to stretch the signal for single bunch operation- tune measurement systems: tune kicker needs rough timing, tune meter will have one front-end not depending on timing basic functionality without BST- all TV based monitors: will work without BST, obviously no bunch gating (sync-light telescope, ionisation profile monitor, screens)- wire scanners and luminosity monitors: will have an acquisition mode without BST- AGM and LDM: need the BST in order to work.

8. Lessons learnt from LEP (2/2) • Hardware can not be tested because software not ready,Software can not be developed because hardware not available…- The FESA framework provides the possibility to have device emulation of missing hardware, such that the software can be developed and tested at a time when the hardware is still partially missing: This feature will help having software/hardware ready in time

9. Commissioning with Beam: BPM system

10. BPM system: • Application software:This should be in good shape:System commissioner at work since years. Application programs very similar to those of LEP and SPS.Attention: The turn by turn analysis program as provided for the SPS needs more work.

11. Commissioning with Beam: BLM system

12. There will be 3000 * 11 dump thresholds with an energy dependent multiplication factor to be computed in simulation, to be implemented and to be tested! Beam Commissioning: BLM dump thresholds • There will be more than 3000 beam loss monitors. Each of them can be enabled to dump the beam. • The dependence of the dump level as function of the duration of the loss (3 orders of magnitude) is realized with 11 different integrators with exponential staggering of integration times (about factor 2) • The dependence on beam energy represents another 2 orders of magnitude (multiplication factor) Clear need for a system- commissioner

13. Beam Commisioning: BCTs • DCCT: will be checked with calibration wire.Will work from day 0. Verifications of EMC immunity, noise behaviour and appropriate improvements during the run. • Bunch to bunch system:Requires BST, will be available after a few hours of beam (setting of timing delays). Presently we study a filter to stretch the bunch shape by a factor 20. This should give then a measurement without the timing adjusted, but signal to noise for pilot intensity very poor. • Lifetime calculations:Noise of DCCT: 0.5 uA rms (1 Hz bandwidth)Pilot beam: 9 uA: 10h lifetime calculation needs 10-5 noise level for current measurement.Take bunch to bunch system for lifetime. Noise level (single shot): 10-2 for pilot. Need 10^6 turns to gain factor 1000 in statistics: 200 s measurement time for lifetime or more bunches….

14. Beam Commissioning: Tune measurements We will start with the basic method: Kick as beam stimulus, FTT of beam motion:Q-kicker: 9 us pulse length, needs rough timing set up (a few hours)BPM for tune measurements (for example BBQ system) does not need timing, data acquired with 24bit audio system (one acquisition per turn = 11k Hz). Basic system will be operational at day 0.

15. Beam Commissioning: Tune measurements Time resolved measurements, PLL tune tracking: 1) We will prepare the software for a sequence of kick stimulus and FFT based tune measurements (spectrogram). This contains more information than a PLL trace and it will be available straight away. 2) The PLL will need a few weeks to be set up (BNL: 3 years, FNAL after 1 year a preliminary system in one plane). US-LARP collaboration ongoing. Difficult to say when first system will be operational.Compatibility with transverse damping so far unclear. System Commissioner in AB-OP would help.

16. Beam Commissioning: Chromaticity Measurements: • Day 0: kick stimulus and Head-Tail analysis of resulting betatron motion. This system needs the BST to be set up ( a few hours). • Condition: betatron oscillation has to last at least 20% of a synchrotron period. • As already mentioned: Considerable software effort needed for automated repetitive (= time resolved ) chromaticity measurements. • Alternative: Difference in tune for two discrete settings of beam momentum (sufficient to monitor decay during injection plateau) Chromaticity tracking via periodic momentum modulation will be available as soon as the PLL works. Again, considerable effort in the application programs will be needed to extract chromaticty data.

17. Coupling Measurements • Day 0: Again kick as beam stimulus. Coupling (in particular if large) from cross talk to other plane: (software?) • Day N:With PLL available: closest tune approach measurement From ISR!

18. Transverse Diagnostics: • Clear two step approach:1) Day 0 with kicked beams and classical motion analysis2) Day N with PLL and more powerful time resolved methods.This puts a high pressure on getting dedicated machine time in order to commission the PLL early.As long as emittance growth is not the major concern, the problems will be:- automation of parameter settings depending on beam conditions (filters, gain switches, timings)- phase scans in order to determine the correct PLL lock conditions For operational beams the additional problems will be:- lowering the excitation level to an insignificant level- achieve compatibility with resistive transverse damping

19. Commissioning with Beam (2)

20. Commissioning with Beam (3)

21. Conclusions • The BDI group makes an attempt to have integrated into all instruments basic modes of operation, which will give acceptable measurements in the conditions of “bootstrap”. • The essential systems for commissioning have an acquisition mode independent of beam synchronous timing. • The BLM system for machine protection will need a considerable commissioning effort. • All systems need a large investment into the corresponding application programs. • The recently proposed concept of system commissioners should be implemented soon with the right people selected for the key beam instruments. This is for me the most urgent line of action.