1. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 1 Main goals for this session: -summarize the main ‘Accelerator Physics systems’ that need to be analyzed / verified during the early LHC commissioning (e.g. optics, aperture, emittance, correction circuit powering - adjustments, beam loss patterns, cleaning efficiency etc.) -review the ‘Readiness for these Accelerator Physics systems’ -review the required beam plans for ‘commissioning’ the systems during the early LHC operation -discuss the planned procedures and required sub-systems / tools for ‘operating’ the above Accelerator Physics Systems during the commissioning -review procedures and required tools for verifying key parameters

2. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 2 Session Organization: 1)LHC optics (version summary and data base implementation) 2)LHC Aperture (known bottlenecks & procedures for measurements)  -beating, coupling and dispersion measurement and correction 4)Orbit correction tools (threading, feedback loops, IR regions) 5)Q and Q’ and coupling correction (options of feedback loops) 6)Emittance (measurement procedures and tolerance budget) 7)Non-linear correction circuits (which are required & procedures) 8)Beam loss patterns and BLM system 9)MADX online model -Session coordinated by A. Macpherson AB-OP and O. Br ü ning AB-ABP -Session discussed 9 ‘Accelerator Physics Systems’ in 11 presentations

3. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 3 LHC Optics: 1)LHC optics is in good shape [current version 6.501 and 6.503 to come (x-ing magnet & coll.)] 2)Modular optics design: arc, IRs with various  * values and squeeze 3)Current optic versions optimized for aperture at injection energy  * values in IR1 and IR5 lowered to 11m (from 18m) (-> reduced squeeze) 5)All layout files automatically generated from EDMS data base (including aperture) 6)Optic files are well integrated in LSA (files are already used for hardware commissioning and squeeze ‘dry runs’) -Presented by Thys Risselada AB-ABP (overview of the optics versions) and Marek Strzelcyk AB-OP (data base implementation in LSA)

4. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 4 LHC Optics: 1)Aperture and alignment entries in EDMS data base are not complete [current implementation based on individual effort and local files]  Status of the ‘as built’ data base? 2)Current optic versions optimized for aperture at injection energy  IR phase advance still needs to be optimized for minimization of chromatic aberrations 3)Modular optics implementation implies D x is not matched for crossing angles on  need to specify procedure for D x correction when crossing angles are on (no correction for vertical dispersion) 4)Optics file naming conventions could be improved Open issues:

5. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 5 LHC Aperture: 1)LHC aperture model includes: LHC optic model; mechanical aperture of elements; manufacturing tolerances; alignment tolerances and tolerances for optic imperfections (closed orbit,  -beat, spurious dispersion) 2)Aperture model was developed within collimation team in collaboration with ABP; OP; TS-IC (first version available since mid 2004). 3)LHC aperture maximized by the MEB activity (gain of about 1  beam size) 4)Alignment information from MEB activity is available via WISE (  magnet geometry information available for MADX use) 5)Potential aperture bottlenecks are well known and documented. 6)Procedures for aperture measurements with beam are well established (the required hardware and application software are ready and in place). -Presented by Stefano Redaelli AB-ABP

6. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 6 LHC Aperture: 1)Aperture and alignment entries in EDMS data base are not complete [current implementation is based on individual effort and local files]  Status of the ‘as built’ data base? 2)Information on vacuum chamber aperture non-conformities not accessible  access to non-conformity reports often denied to ‘outsiders’  quoted operational  implementation in ‘as built’ data base? 3)Modular optics implementation implies D x is not matched for crossing angles on  need to specify procedure for D x correction when crossing angles are on (no correction for vertical dispersion) 4)Radiation and activation in the transfer lines de to aperture limitations needs to be specified 5)Issues related to integration in tunnel need to be clarified  next LTC Open issues:

7. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 7 LHC  -beating, coupling and dispersion: 1)Various calibration independent measurement procedures are well defined and tested (robustness tested in simulations [MADX] and general test of methods with beam in RHIC operation; future tests are planned in the SPS). 2)Correction procedures have been defined and tested (robustness tested in simulations [MADX] and general test of methods with beam in RHIC and future tests are planned in the SPS) 3)Controls application are being implemented 4)Measurements can be done with pilot bunch intensities and required hardware (kicker magnets) and controls application (turn by turn BPM acquisition system and YASP) should available for start-up Rogelio Tomas Garcia AB-ABP

8. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 8 LHC  -beating, coupling and dispersion: 5)Procedures would benefit from AC dipole implementation in the LHC and from beam profile monitors (the LHC rest Gas Ionization monitor might not be operational for early commissioning) 6)Method and tools will be presented in a dedicated AB seminar Rogelio Tomas Garcia AB-ABP

9. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 9 Orbit steering and correction tools: 1)Threading procedure is well defined (MICADO with few correctors applied to limited region where amplitude grows) and tested (tests based on MADX simulations). 2)Energy scans via the SPS should not be an issue (SPS energy is 449.2GeV) 3)Common regions in the LHC require special attention (settings for one beam will affect threading for second beam). Various strategies exist. 4)The steering application provides automated procedures for probing calibration and optics errors (online diagnostics possible). 5)Implementation of local CO corrections (e.g. IR x-ing bumps & cleaning) 6)Closed bump application available (e.g. aperture scans) J ö rg Wenninger AB-OP

10. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 10 Orbit steering and correction tools: 7)Slow (< 0.1Hz) orbit feedback based on YASP is only available for operation at injection and collision. 8)Slow feedback will not work during ramp and squeeze:  real time control outside the LSA frame work required  implementation ready for LHC startup Requirements: -BPM calibration -COD calibrations and mappings are checked -reasonable optics (beta-beat < 50%) 9)The real-time system has functional requirements that are outside the scope and capabilities of LSA but their settings and data interfaces are based on FESA/CMW will be managed through LSA J ö rg Wenninger AB-OP

11. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 11 Q, Q’ and coupling correction tools: 1)Q and Q’ drifts are expected to be large during LHC ramp  Q and Q’ control are an integral part of LHC operation 2)Various tools available for Q measurements (FFT using BPM data, FFT using BBQ data, PLL based measurements). 3)Beam instrumentation for online Q measurements is in place: (PLL system with BBQ) and well tested (SPS, LEIR, PSB, RHIC,….) 4)BI expert interface (Tune Viewer) ready and tested / debugged. 5)Tools for Q’ and coupling measurement are in place 6)Q and Q’ real time feedback ready:  implemented outside the LSA frame work Ralph Steinhagen AB-BI

12. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 12 Emittance measurements: 1)Total allowed emittance growth for nominal LHC beam parameters is small (7%!) and requires accurate measurements data (in the SPS, TL and LHC) and calibration between different machines. 2)SPS emittance depends on number of bunches and bunch intensity (design emittance for all beam parameters requires controlled blow up in the SPS [e.g. by pink noise]) 3)Various tools for transverse beam size measurements exist in the LHC (OTR screens, OTR screen mactiung monitors, wire scanners, SL monitor ionization profile monitors, collimator scans, Schottky) but relative and absolute calibration is an issue. 4)Beam size  emittance measurement requires several nearby monitors and stable optics (e.g. dynamic beta variation) Frank Zimmermann AB-ABP

13. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 13 Emittance measurements: 5)Ideal tool for measuring emittance blow-up during injection is a single monitor that provides turn-by-turn data with high resolution (  1%)  measurements using the matching screens require a fast camera which is not radiation hard (  can not be used in normal operation)  SL monitor and IPM with fast camera might be available from year 2 onwards  not available for early commissioning  use of IPM during early commissioning would require gas injection which is currently excluded by vacuum experts  The LHC will not have a matching monitor for the start-up 6)Three monitors are in place for longitudinal emittance measurements. (but only one might be available for LHC start-up: wall current monitor) Frank Zimmermann AB-ABP

14. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 14 Non-linear correction circuits: 1)In total 200 independent non-linear correction circuits. 2)Only a sub-set of these correctors are required for the early LHC commissioning (mainly lattice sectupole and decapole circuits) (all non-linear triplet corrector magnets are not required for commissioning) 3)Tools and procedures are in place for a beam based verification of the lattice sextupole circuits (use of closed orbit bumps over the arcs) 4)Tools and procedures are in place for a beam based verification of the lattice decapole circuits (via chromatic tune and phase advance measurements and optional resonance driving term measurements) 5)Landau octupole circuits are only required for high intensity operation (Tools and procedures are in place for a beam based verification) Massimo Giovannozzi AB-ABP

15. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 15 Verification of the Beam Loss data: 1)Total of ca 4000 BLM installed in the LHC which are grouped into 250 families 2)Extensive simulations have been performed for simulating the expected loss patterns for different beam loss scenarios (global and local patterns)  installation of 3 BLMs per beam at each locations and optimization of the BLM positions 3)All BLM will be HW commissioned prior to beam operation 4)BLM signals are essential for collimation and MP systems  requires clear definition of the BLMsystem commissioning procedures with beam Laurette Ponce AB-OP

16. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 16 Verification of the Beam Loss data: 5)Several discussions on the BLM beam commissioning took already place in the past (LTC and Chamonix) and raised the issue of uncertainties in the knowledge of the LHC magnet quench and damage levels and the correlation of beam losses to measured BLM signals. The discussions lead to the proposal of beam induced quenches for the calibration of the magnet quench levels. Laurette Ponce AB-OP

17. 17 typical results of the simulations z (cm)‏ Maximum of the shower ~ 1m after impacting point in material whatever the impacting angle and transverse position of the post protons increase of the signal in magnet free locations factor 2 between MQ and MB 20 % more in the peak amplitude by doubling the angle (typic. 0.25 mrad)‏ 40 % less in peak amplitude between the uppermost/innermost impacting point

18. 18 Realistic “local” loss pattern The 3 monitors at the quadrupoles will show a decreasing signal in beam direction beam 2 Cross-talk signal

19. 19 Topology of the losses Position of the detectors optimized to catch losses from the aperture limitation and middle of the quad but a change of 25 cm in the impact point position makes a factor 2 in the signal thresholds at the worst case (conservative) or at the most likely(statistics needed)?

20. 20 Ingredients of the recipe Threshold values contain :  the BLM response (electronics, chamber response calibration)‏ measured during HW commissioning  the position of the BLM relative to the cold masses,i.e amount of material to cross (BLM grouped by families)‏ requires different threshold values for each family  the ratio between the lost protons and the BLM signal (particle shower simulation) ‏factor of 3 to 4 uncertainty expected from simulation studies  the ratio between the BLM signal and the deposited energy in the coil for the family (particle shower simulation)‏ obtained from simulations  the knowledge of quench level and/or the damage level (W/cm 3 )‏ (seeds for parametrization) no calibration available for the moment  the dependence of the quench/damage level on beam energy and integration time. (for parametrization of the thresholds)‏ obtained from simulations  topology of the losses studied in simulations  calibration with measurements required?

21. Trade-Off: Number of Quenches vs. False Aborts Assumed quench limit BLM threshold (-) not all quenches caught (+) no false aborts (+) all quenches caught (-) many false aborts given by the same simulation toolkit quench test calibration

22. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 22 Verification of the Beam Loss data: 6)Operation tools are in place to adjust BLM threshold during operation between extreme limits (ultra safe versus just safe damage) 7)Controlled beam induced quenches would help removing one uncertainty for the BLM threshold setting (but other uncertainties remain!)  Can we justify with this dedicated quenches during sector test?  or should we start operation with conservative BLM settings and increase BLM settings when required?  how do you assure proper machine protection in the later case? 8)Dedicated quench test outside the LHC would be ideal  was already proposed in past Chamonix meeting but not possible due to lack of resources  this should be re-analyzed  what type of magnets should be chosen? Laurette Ponce AB-OP

23. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 23 MADX online model: 1)Scope: testing of knobs before LHC hardware settings are changed; utilization of all MADX tools in the control room (e.g. aperture mapping); facilitate the offline analysis of measured [orbit response measurements]); front-end to other programs (e.g. TRAIN; tracking programs and PTC) 2)First application tests have been performed for the CNGS start-up 3)First version will be released middle of March 4)First tests are planned for the SPS start-up and system should be ready for an eventual LHC sector test 5)Presented application examples include: off momentum optics calculations; aperture predictions using aperture data base and ‘true’ orbit and optics errors in the machine;  * correction and x-ing angle adjustments -Presented by Frank Schmidt AB-ABP (basic tasks and implementation) and Werner Herr AB-ABP (implementation in LSA)

24. Beam Plans for Accelerator Physics Systems eLTC Summary February 2008 - Session 5: Beam Plans for Accelerator Physics Systems 24 Summary: 1)Readiness of the Accelerator Physics System seems to be in good shape 2)Many aspects have been already tested in other machine and / or are planned to be tested. 3)First tests are planned for the SPS start-up and system should be ready for an eventual LHC sector test. 4)Some issues still need to be clarified: e.g. are we planning dedicated beam induced magnet quenches during sector test or commissioning? 5)Many sessions featured discussions on planned and potential ‘dry runs’  these ‘dry runs’ should be organized as son as possible with the involvement of the whole commissioning team 6)Status and future of the ‘as built’ data base need to be looked at 7)LHC matching monitor would be very desirable for start-up