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Re-commissioning 2012

Re-commissioning 2012. J. Wenninger , G. Arduini , C. Bracco , LHC machine coordinators and friends. Schedule. 21 days + 3 days of scrubbing. Physics @ Easter… DSO tests March 1 st and 2 nd – tbc . Expected end of powering tests. Machine configuration. See one of Stefano’s talks….

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Re-commissioning 2012

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  1. Re-commissioning 2012 J. Wenninger, G. Arduini, C. Bracco, LHC machine coordinators and friends

  2. Schedule • 21 days + 3 days of scrubbing. • Physics @ Easter… • DSO tests March 1st and 2nd – tbc. Expected end of powering tests LBOC - LHC re-commissioning

  3. Machine configuration See one of Stefano’s talks… LBOC - LHC re-commissioning

  4. Options for b* 4 TeV, 50 ns, 1.5e11, 2.5 microns

  5. Beta* choice • b* = 0.9 m : standard 2011 collimator settings • 2011 workhorse – known to work well. • From 0.9 m to 0.7 m : here is the ‘BIG’ step • From standard to tight collimator settings. • Tight settings worked in physics (EoF), • … but gave some issues in squeeze with non-colliding beams and reduced BB separation. • From 0.7 m to 0.6 m : ‘small’ step • Re-arrangement of TCSG6-TCDQ-TCT. Tolerances added quadratically - ‘risk management’. LBOC - LHC re-commissioning

  6. This assumes that they are statistically independent and builds on the fact that the variances can be added linearly to obtain the variance of the sum of any uncorrelated stochastic variables. Margins Roderik Bruce/Ralph Assmann Error margins at TCTs 70 cm 60 cm

  7. Tight settings • Issues to be resolved • Orbit control in squeeze – in particular at matched points . • Instability/impedance control with octupoles and better chromaticity control . • Good points: • > 20% increase in performance • Not so good: • Increased sensitivity to beam perturbation • Effect of strong octupoles? • Operational demands on Q’ control.

  8. Tight versus tight • 70 cm • Good: familiar tolerances, lower pile-up. • Not so good: -5 to 10% performance (NB bunch length). • 60 cm: • Good: performance, challenging. • Not so good: pile-up, assumptions involved in adding margins in quadrature, optics issues(?).

  9. Proposal for b* strategy • Prepare squeeze settings to 0.6 m and 0.7 m. • Work in progress - sequence update and optics import. • 2 separate squeezes. • Commission with low intensity (probe/nominal) to 0.6 m. • Measure and correct orbit, optics, Q’ etc at 0.9, 0.7 and 0.6 m. • Define target for Q’ (< 1 ?) and octupoles (I = xxx A). • Q’ reproducibility measurements in squeeze? • Step back to 0.7 m for (initial) operation. • Collimator setup and validations with 0.7 m. • Possibly move to 0.6 m later in the year. LBOC - LHC re-commissioning

  10. Configuration – open points • Crossing angle IR2 to be decided. • LHCb external crossing angle rotation. • Propose to perform it AFTER colliding - one setup for both LHCb polarities. Ramp down H angle in parallel to ramping up V angle. • Could easily revert back to 2011 situation by removing this last step. • Extra beam process (BP) or part of collision BP (with stop point before rotation)? To be decided. • Decide on H crossing angle at 4 TeV in IR8. • Scaling 3.5 TeV situation  220 mrad. Ramp down in ~140-150 s. • Can we use smaller values  Werner et al. • Need an ‘official’ V crossing bump for imports (madx strength files). LBOC - LHC re-commissioning

  11. Other points • Bunch length: • Start off with 1.2-1.25 ns (2011) and then test 1.3-1.35 ns later. LBOC - LHC re-commissioning

  12. LHC re-commissioning Injection Collimation Dump First turn, CO, capture Transfer line setup Setup 450 GeV Collimation 450 GeV Injection steering Setup 4 TeV 450 GeV Ramp settings Ramp Dump protection Injection protection Collimation 4 TeV FT Squeeze Transfer line collimation Dump protection validation Tertiary setup squeeze & collisions Optics corrections Injection protection validation Squeeze settings MPS commissioning Loss maps Injection setup & validation Collimation setup & validation Stable beams and intensity ramp up LBOC - LHC re-commissioning

  13. Planning - outline • Commissioning plan for 2012 (inspired by 2011 actual commissioning) based on 20 days with 100% machine availability. • Day count arbitrary (for the moment). • Time allocated to different topics is based on: • Experience. • Evian/Chamonix presentations & plans. • Will be completed with more input. • We may have to consider moving some items into the intensity ramp up in case the list becomes very long. LBOC - LHC re-commissioning

  14. Planning - outline The first few days. Exact order will be redefined on daily basis – the machine will tell… LBOC - LHC re-commissioning

  15. Planning – selected items • 3 dedicated BI shifts • Q/orbit feedbacks have extra time. • 3 RF shifts • 4-5 ADT shifts (probe, nominal, 50 ns, abort gap, injection cleaning) • 3 decay measurement shifts (injection, FT) • 2 shifts for aperture at injection • 3 (+1 spare) shifts for local apertures at 4 TeV • 1 shift for loss map / asynch dump tests @ 450 GeV • 4 shifts for loss map / asynch dump tests @ 4 TeV • Commissioning of ‘ADT excitation’ maps within those 5 shifts. • Impedance measurements shifts needed? LBOC - LHC re-commissioning

  16. Injector beams • Standard probe • Standard nominal • 50 ns : prepare for ≥1.4E11 p/b. • 25 ns : nominal for scrubbing run. • But only injections of 72 b LBOC - LHC re-commissioning

  17. Access during operation • Contrary to 2011 where the WAT was active only in TS, IMPACT will remain active for access throughout the run. • For short accesses during operation: • Fill in the IMPACT form when the need for access arises (even if not urgent). • When the coordinators decide to schedule an access on a given day, they will grant the access based on the IMPACT information (duration, location). • The IMPACT will be signed by the EiC/operator/coordinator just before the access. • This will allow us to track the access requests (main aim!). • There will be special IMPACT templates for un-scheduled short interventions. LBOC - LHC re-commissioning

  18. Tight settings and orbit • Orbit in squeeze commissioning. • Hope to do it in parallel to the other squeeze work. • Requires a few squeezes (in one go) with probes/nominals. • Possible approaches: • Feed-forward from the orbits predicted from the model. • Feed-forward from measured orbits. • Run OFB with higher bandwidth (hoping that it catches all), feed-forward the OFB trims into the functions. • Has been demonstrated with ions, software ready. • For A. and B. there is no ad-hoc software – could do it semi-manually with YASP. • Alternative: scrape tails in the ramp with TCPs? • Close the TCPs a bit more in the ramp (0.5s?) and then re-open at very end of ramp/start of squeeze. • May then be less sensitive to orbit in the squeeze…. LBOC - LHC re-commissioning

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