First turn

Succcessfully completed November 2009, and with minimal problems February 2010.

Assumptions: The clear assumption here is that both apertures are clear and that there are no major polarity errors. Either of these problems could seriously hamper establishing a first turn and necessitate a crash program of measurements to try and find the location of the problem.

Prerequisites: machine configuration as specified above. Full machine checkout performed.  Kicker pre-pulses, timing events.

Exit: pilot around one turn with trajectory corrected to better than, say +/- 3 mm., beam on available screens

Objectives - clear that some of these will have a low proirity during initial commissioning

- Commission TI 8 end, injection and thread to IR7/IR3
- Commission trajectory acquisition and correction
- Commission Beam Loss Monitor system (largely in shadow of other measurements)
- Optics measurements
- Aperture checks
- Effect of magnetic cycle
- Field quality/polarity checks
- BLM response - collimators
- (Setting up of injection machine protection)


  Beam Task Group Time Status  
1 B1/B2

Commission TI8 & TI2 end transfer line,
Commission injection region: kickers, septa, check aperture, instrumentation, beam to TDI.

BT/OP 6 hours per beam Done in injection test  
2 B1/B2 Commission trajectory acquisition and correction,   12 hours Done in injection test  
3 B1/B2 Initial commissioning of beam loss monitors   24 hours Done in injection test  
4 B1/B2
  • Thread - first turn,
  • energy matching between SPS & LHC, between sectors
OP/BI 12 hours S23 done  
5 B1/B2
  • BPM and corrector checks via kick-response
  • Optics checks via kick-response

Method established OK for S23-34-45 B1
S78-67 B2

6 B1/B2 Initial aperture check via free osciallations OP/AP   Leave for circulating beam  
7 B1/B2 Polarity checks        
8 B1/B2 Dispersion        



Commission injection region:

Prerequisites:  TDI fully in. Injection kickers off


Dedicated/expert application software
–Injection steering, injection post-mortem, TDI positioning, injection fixed displays, equipment expert applications
Remaining issues/areas for study
–Tight aperture at MSI septum -local correction strategy?
–Synchronised shot-by-shot logging for each injection (not“Post-Mortem”)
–Controls across TI 8/LHC interface?


Commission trajectory acquisition and correction.

• ‘LEP strategy’
–Inject & measure; correct over small range (manual BPM rejection); iterate
–Watch out for the separation/recombination dipoles (transfer functions…)
• Method checked by coupling MAD-X to YASP steering program, with aperture filter, noise etc. (LHC beam 1)
– Results promising (in absence of big problems, egquad polarity reversals)
• 13 iterations for fullfirst-turn. Expect 1-4 iterations to IR7 TED?
• Fairly insensitive to errors, e.g. isolatedbad BPMs with >10mm offset

Dedicated/expert application software
–YASP, BPM intensity acquisition and signal display
•Other stuff
–TI 8 + LHC beam 2 MAD-X sequence with full aperture model
•Remaining issues/areas for study
–Extend threading from TI 8 TED87765
–Extend threading simulations to check sensitivity to:
•Injection errors, quadrupole polarity errors, …
•More subtle errors : BPM signs, H/V crossover, calibrations+ energy offsets, mega-offsets, noise, …
–Still foresee to test an automatic threader? Does not seem justified….


Take screens and TDI out. Thread beam..

Check all related beam instrumentation:


BLMs, Get the system up and running, recording losses
–Prior calibration with source: expect reasonable numbers quickly(factor ~5)
–Acquisition (& display!) of beam losses for some (many? all?) monitors
–Some crosstalk studies possible (in principle ‘beam 1’monitors available…
6 hours beam time foreseen early on–Will be plenty of other opportunity for parasitic commissioning–Probably to be organisedtogether with the aperture measurements

Dedicated/expert application software
–BLM displays, MCS?, BLM expert applications•Remaining issues/areas for study–Finalise data exchange with control system (logging, PM, thresholds) –BLM display (prototype for final LHC version?)–Triggering for single-shot logging? Do we need it???–Post Mortem to be tested?


BPMs (polarity, offsets). This will be the first, provisional check of the aperture and polarity. Check energy matching. Threading beam to first turn. auto-trigger, sum signals



Linear Optics checks

Trajectory response using correctors and BPMs
–BPM + corrector polarity and calibration errors
–Phase, coupling, Twiss
•Dispersion measurement with dpand BPMs
•Betatron matching measurement with BTVsTED

(Tools already tested in TI8 etc.)

12 hours foreseen early on
–1-2 x 1010 p+ for improved BPM and BTV response
– Semi-automated tests….lots of off-line data analysis to make quickly
Dedicated/expert application software
– Automatic kick-response measurement and correlation with logging,
– BTV image processing, online re-matching and analysis tools?
•Remaining issues/areas for study
– Expected measurement accuracies, tools for analysis & re-matching
– TI 8 beam time in Oct/Nov 2007 for further tests of tools


Aperture measurement

Verify physical aperture as expected (bottlenecks, arc, IRs)
– First iteration : oscillation from 2 correctors at 90ºto probe ‘all’phases
– Second iteration if needed/time : pbumps (local anomalies, specific regions)

Momentum aperture (lower priority)
–Transmission vsmomentum offset by changing SPS RF frequency
–Probably limited by TI 8 arc (max |Dx| ˜4 m, c.f. 2 m in LHC) so maybe not worthwhile as explicit measurement…
–Could rematch TI 8 to another momentum(present measured acceptance ±0.003)

• Dedicated/expert application software–Need automatic “scan ‘n’measure”applications:
• Free oscillations (~5 amplitudes, ~12 phases, 2 planes, ~2 starting locations)
• For sliding bumps (~45 correctors, 2 planes, ~5 amplitudes)
• Remaining issues/areas for study–Best way to measure LHC momentum aperture



Alternative pathways

Backup optics?

Alignment optics?

Big kicks?