Status of Loss Map Simulation with MERLIN Code

1. Status of Loss Map Simulation with MERLIN Code M. Serluca, R. Appleby, R. Barlow, J. Molson, A. Toader

2. Summary MERLIN code LHC optics calculation LHC collimation and cleaning efficiency: loss map Impact of imperfections on loss map Enhanced scattering physics model Future plans and conclusion

3. MERLIN code C++ Accelerator Physics library Written by Nick Walter et al. (DESY), it was initially used to simulate ground motion in the ILC beam delivery system and later for the main linac and damping rings Now adapted for large scale proton collimation simulation by Manchester and Huddersfield Allows a modular design for different physics processes

4. MERLIN code Accelerator lattice design: can load directly from tfs table output of MAD or XTTF format, the main classes for each elements of the machine are the AcceleratorComponent, EMField, Accelerator Geometry, Aperture, WakePotential Bunch creation: can be generated anywhere along the machine and with different phase space distributions Particle tracker: particle and moment tracking, different integrator sets can be specified, override specific integrators Physics process: examples are wakefield, synchrotron radiation, space charge and collimation, they can be applied at selected elements and positions

5. MERLIN code Position errors: can misalign the position of every elements in s, x, y and can adjust angular tilt. For the collimators is also possible to misalign and tilt the individual jaw Field errors: can be added including additional multipoles Parallel running: MPI protocol in order to run large simulations using multiple physical machines with interconnects Tracking, collimation etc. are independent on a per-particle basis

6. LHC optics calculation with MERLIN Thick-lens version V6.5.2012.seq Energy = 4TeV, en= 3.5 mm-mrad, dp/p = 0, sz=0 Using beam 1 or beam 2 b* for IP1 and IP5: 0.6 m b* for IP2 and IP8: 3 m Crossing Angle [mrad]: X1 = -145, X2 = -90, X5 = 145, X8 = -220 Parallel separation on at all IP: sep = +/- 0.65 mm

7. LHC optics calculation: IR5

8. Loss map: simulation setup Optics setup: squeezed and separated beams Ideal machine: no imperfections and collimators aligned to orbit Beam1 horizontal pencil halo: a ring in x-x’ in the normalized space, 0values for the vertical coordinates 6.4M particles simulated, beam halo injected at first horizontal primary collimator in IR7 (TCP.C6L7) and tracked for 200 turns Impact parameter = 1 mm and 10 cm longitudinal loss resolution Sixtrack like scattering mode

9. Loss map result with MERLIN Inefficiency definition:

10. Loss map result: IR7 zoom

11. Impact of lattice imperfection on loss map Misalignment and magnetic errors on lattice elements are introduced and corrected in MAD using the available correctors, then they are imported in MERLIN The collimators are aligned to the ideal reference orbit Simulations for uncorrected orbit show a different distribution of the losses and can lead to the collimation hierarchy breaking Simulations for corrected orbit show a little impact on the loss maps

12. Impact of imperfections on loss map Unavoidable errors affect any accelerator and can further degrade the cleaning efficiency Random errors with Gaussian distribution cut at 3 s are generated inside MERLIN for collimator-jaw alignment and tilt angular errors

13. Impact of collimator imperfections on loss map RMS error on gap center with respect to the beam orbit: 50 mm RMS error on gap size: 0.1 s RMS error on jaw angle with respect to the beam orbit: 200 mrad Jaw flatness error: not yet implemented Non ideal closed orbit: not yet evaluated

14. Impact of collimator imperfections on loss map (preliminary results) For misalignment, tilt and gap error an increase of a factor 2 in the highest cold loss was found with respect to the ideal case Next step is the introduction of the deformation jaw and the evaluation the impact of the combined effect of collimators and lattice errors

15. Enhanced scattering physics More accurate simulations of the losses in the dispersion suppressor need a detailed knowledge of the scattering physics processes in the bulk jaw material New models of proton-proton interactions have been developed, with the aim of expanding these to proton- nucleus interactions

16. Enhanced scattering physics: elastic Elastic scattering will give an angular kick to the ongoing protons, resulting in an increase of the beam halo and the possibility to be lost along the machine Use the model of Donnachie and Landshoff: arXiv:1112.2485v1 [hep-ph] Fit the existing pp and p-pbardata is possible because data exist on either side of the region of interest The fit on elastic data is almost completed

17. Enhanced scattering physics: SD Single Diffraction interaction on a nucleon will result in an angular kick and energy loss to the outgoing proton The proton with an energy lower than the reference one will enter in the dispersion suppressor and will be subject to a larger orbit excursion. Use the model of Donnachie and Landshoff that involve soft QCD physics: arXiv:hep-ph/0305246v1 The fit on SD data is completed

18. Conclusion and future plans We are developing the code MERLIN in order to produce loss maps for collimation simulations for the current layout and future HiLumi upgrade Results for 4TeV 2012 running show a good agreement with sixtrack simulation results The results with new elastic and SD model are in progress A more detailed description of the effects induced by lattice and collimator imperfections is almost ready Near future works will be focused on advanced materials and the improved optics We are open to collaborate on new ideas for HiLumi project

20. Reserve slide