Beam Loss Simulations LHC

1. Beam Loss Simulations LHC • Shower Development in • Arc Magnets • Dispersion Suppressor Magnets • Long Straight Sections • Collimations Regions • Location of Proton Losses along the LHC • Fluencies and Doses • Loss Simulations for Ions

2. Shower Development in Arc Magnets • Simulations by Ana Arauzo (1998-2000), optics version 6.2(LHC Project Note 238, LHC Project Note 213, CERN-SL-200-052 BI). • Charged secondary particles (called “MIPs” in the papers) are counted outside the vacuum vessel (in a 10 cm high detection area). Energy and spectrum of the particles not known. • 3 loss location (middle of quadrupole, and misalignment before and after the quadrupole), point losses and distributed losses (assumption 4m). • 4 combinations of beam directions and magnetic fields. • 3 loss locations: inside and outside of beam screen and top of beam screen (bottom is about the same as top).

3. BLM position BLM position Loss location Loss location Shower Development in Arc Magnets • Different corrector magnet layouts simplified to two cases (with and without MDCO in front of the dipole magnet). • Dependence on energy studied: Factor of 10 to 25 in signal for a 7 TeV proton compared to a 450 GeV proton, depending on loss location. Dependence linear to quadratic (on given longitudinal position. 10-4 MIPs/ p cm2

4. Loss location BLM position Shower Development in Arc Magnets • 6 BLM positions on/around each arc quadrupole proposed and calibration constants calculated. Positions: z= -250, 200, 450 cm (for beam going right) and z= -450, -100, 200 cm (for beam going left). The positions are chosen to: • reduce difference between inside and outside loss • minimize crosstalk • distribute loss to resemble point loss • reduce difference with and without MDCO • BLMs do not sit at shower maximum. Losses simulated at z=0 and z=+/-325 cm

5. Shower Development in Arc Magnets: To Do • Some positions will have to shift for space reasons (BLMs about 0.5m long) – calibration constants? • Calibration constants calculated for fluency (all charged particles are considered to give the signal of a MIP) – changes if energy deposition is calculated? • Check Ana’s assumptions of p losses against new simulations. • Did the arc layout change since version 6.2? (Diameter of beam screen changed in the meantime.) • Energy spectrum and particle spectrum – penetration of ionization chamber?

6. Shower Development in Dispersion Suppressor Magnets • Simulations by E. Gschwendtner (2001-2003), optics version 6.3 (AIP Conf. Proc.: 648 (2002) pp.229-236, CERN-AB-2003-068-BDI, CERN-SL-2002-021-BI). • Geometry in GEANT 3 for all layouts of dispersion suppressors (10 cases). • Simulations for region of Q10 of one dispersion suppressor layout (right of IR1 and IR5), 19 different cases: • beam 1 and 2 • longitudinal loss position • transverse loss position (top, left, right of beam screen) • energy (mostly 7 TeV) • Incident proton lost at 0.25 mrad (results depend only weakly on angle)

7. Shower Development in Dispersion Suppressor Magnets • Shower maximum: 1m after loss point of proton • Shower width: 0.5m

8. Shower Development in Dispersion Suppressor Magnets • Angles theta (angle to the x-axis) and phi of charged particles at detector location: mostly in horizontal plane and with an angle of 45 degrees to the x-axis.

9. 1 bin = 5 MeV Energy [GeV] Shower Development in Dispersion Suppressor Magnets • Number of charged particles and energy deposition simulated: • Energy spectrum:

10. Dispersion Suppressor Magnets: To Do • Particle Spectrum. • Refined Energy Spectrum. • Recheck the angle distributions. • Folding of GEANT results with distribution of longitudinal p losses (exist only for right of IR7 at the moment). • Possibly simulation of different magnets and dispersion suppressor layouts necessary. • Define (optimize) positions to install BLMs and calculate calibration constants. • Simulation (GEANT) of the shower particles through the real chamber design (M. Hodgson).

11. Shower Development in Long Straight Sections (excluding collimation, including triplets) • Not yet started To Do: • Longitudinal loss positions with an aperture model including the LLS (has been promised for last year, but still not here) and different beam conditions. • Define (optimize) chamber positions and calculate calibration constants (similar to the work done for the arc and dispersion suppressor – but a very big variety of layouts).

12. Shower Development in Collimation Regions • Momentum cleaning, IR3, simulations for protons by Igor Kurochkin (MARS) and J.B. Jeanneret (K2) (2003). • Optics version 6.2 but new collimator design. • Fluency and energy deposition in a (10x10x10 cm3) air volume calculated. • Energy threshold 10 MeV for charged hadrons and 1 MeV for electrons. • BLM positioned 30 cm downstream of collimators and less than 10 cm from the center of the beam pipe. • “Good” signal (from the adjacent collimator) compared to “background” signals from other collimators and the second beam. Most signals dominated (90-99%) by “background” signal.

13. Shower Development in Collimation Regions: To Do • IR3 with final optics • IR3 for ions (I. Kurochkin?) • IR7 for protons and ions (Alfredo Ferrari and team – to be defined by E. Chiaveri). • In the final layout of the collimation, there might be space problems for putting the BLMs close to the beam!

14. Location of Proton Losses along the LHC • First simulations by E. Gschwendtner and V. Kain (2002-2003) of tertiary halo particles (MADX and SLICETRACK). But a detailed aperture model of the LHC was missing  • New aperture model (dispersion suppressor and arc right of IR7) and tracking of tertiary and secondary halo particles, E.B. Holzer and V. Kain (end of 2003), (halo particles simulated by R. Assmann). p lost / p on primary collimator Q27 Q28 Arc cells, z [m]

15. Location of Proton Losses along the LHC p lost / p on primary collimator Q7 Right of IR7 after last collimator, z [m] • Longitudinal resolution of the simulation ~1.5m • Longitudinal resolution of the aperture model: very high (<cm) – loss regions can be studied in detail (SLICETRACK).

16. Location of Proton Losses along the LHC Q11 Q8 Q7 p lost / p on primary collimator Dispersion suppressor and beginning of arc right of IR7, z [m]

17. Location of Proton Losses along the LHC: To Do • Aperture model for the whole LHC – especially the straight sections. • New halo data. • Different scenarios – range of different loss patterns: • orbit error • misalignment • including non-linear effects • beta beat • different collimator settings • Investigate statistical fluctuations of loss patterns. • Finer slicing of loss locations at critical points (e.g. with SLICETRAC). • Transversal position of loss?

18. Fluencies and Doses • Simulations of fluencies and doses in the dispersion suppressor of IR3 by I. Baishev, J.B. Jeanneret, I.A. Kurochkin, LHC Project Note 331 (2003). • IR3? To Do: • Study consequences for BLM?

19. Ions: Long. Losses after Collimations in IR7 • Simulations by H. Braun (2004) with the new aperture model.

20. Loss Simulations for Ions • J.M. Jowett: Electron capture by pair production inside of ALICE. • Other experiments?

21. Loss Simulations for Ions

22. Loss Simulations for Ions • Energy deposition of lost ions in material (compared to protons). By A. Ferrari

23. Loss Simulations for Ions: To Do • Simulations for ion induced showers through the cold mass to the BLMs needed – H. Braun to coordinate (?). • Request for additional BLMs at ion “hot spots” – need to define positions and calibration constants.