Download presentation
Presentation is loading. Please wait.
Published bySilas Malone Modified over 6 years ago
2
Overview of Needs for SixTrack on-line Aperture Check
R. De Maria, M. Giovannozzi, A. Mereghetti, S. Redaelli 8th Mar 2017 A.Mereghetti
3
Outline Introduction; Available Functionalities: Road-map;
Native in SixTrack; In SixTrack for collimation studies; In the Fluka-SixTrack coupling; Road-map; 8th Mar 2017 A.Mereghetti
4
The on-line Aperture Check for SixTrack
SixTrack is a single particle tracking code for beam dynamics based on symplectic integration; it is widely used at CERN for studies of dynamic aperture and collimation; Aperture check: verify that tracked particles stay within the mechanical aperture of the machine; fundamental functionality for predicting losses; …on-line: the aperture check is performed during tracking; Loss Map, B2H, 6.5TeV 8th Mar 2017 A.Mereghetti
5
Functionality Presently Available in SixTrack
Check against a general aperture: Shapes: RECTANGLE; WHAT(4) and WHAT(5) of 4th row in ITER block; defaults: 1m; Check against local apertures: Shapes: RECTANGLE, CIRCLE, ELLIPSE; Input: LIMI block (name of single element, aperture type, 2 specifiers); Liabilities: performed only if the previous check finds at least a particle out of aperture; Bugged parsing of LIMI block (e.g. RECTANGLE is actually treated as ELLIPSE and ELLIPSE is treated as general RECTANGLE); Conflict on use of kp(j) (storing aperture type) with H/VMON (ORBI block); Limited pool of aperture types; Need for revision! 8th Mar 2017 A.Mereghetti
6
Functionality Presently Available for Collimation Studies
Check against local apertures: Shapes: whichever type that can be generalized as RECTANGLE; smoothing of aperture model via linear interpolation of aper. parameters (Ds=10cm); Done as post-processing step by a package external to SixTrack: Trajectories dumped at every element and turn, and compared to the aperture model; Actual point of loss is determined via back-tracking particle coordinates until they match the local aperture (linear fitting, Ds=10cm); Aperture model of entire machine (external to lattice description used at run time): .tfs table (thick lens) with the description of the aperture (including a tilt angle for some apertures); Survey file describing aperture offsets; Hard-coded 8th Mar 2017 A.Mereghetti
7
Functionality Presently Available for Collimation Studies (II)
Liabilities: Being performed at post-processing, particles out of the machine aperture are still tracked: Other quantities computed on-line may be over-estimated; Need for cleaning on-line quantities! handling of a very large file: large disk space use; Intensive I/O; not possible to port to BOINC; OCTAGON aperture not treated; Room for improvement! 8th Mar 2017 A.Mereghetti
8
Functionality Presently Available in the Fluka-SixTrack Coupling
Tracking through lattice structure performed by SixTrack; Once the location of a collimator is reached, the beam is transferred to Fluka for the interaction with beam-intercepting devices, and surviving particles are given back to SixTrack, to continue tracking; Mechanics done at every collimator found and in every turn; First applications: endep in SPS scrapers, LHC ion collimation; Aperture check: Fundamental to have it on-line for the application to the SPS scrapers, in order not to over estimate losses/endep in blade; Functionality obtained merging assets of what was already available in native SixTrack and in SixTrack for collimation studies; 8th Mar 2017 A.Mereghetti P.D.Hermes, 211th CWG
9
Functionality Presently Available in the Fluka-SixTrack Coupling (II)
Check against local apertures: Shapes: whichever type that can be generalized as RECTELLIPSE + RACETRACK + OCTAGON; smoothing of aperture model of machine via linear interpolation of aperture parameters - Ds=ad libitum; Performed on-line during tracking (no handling of big files): input: LIMI block; particle trajectories are compared to local aperture model; actual point of loss is determined via back-tracking particle coordinates via bi-section method; full aperture model of machine (including offsets and tilt angles) is embedded in the lattice description used by SixTrack at run time: same input info as the one for collimation studies can be fed; merging done as pre-processing step; Liabilities: Back-tracking performed assuming only DRIFTs (as for collimation version); Broken original mapping through nlostp(j) (important for DA calculations); Good starting point! 8th Mar 2017 A.Mereghetti
10
Road-map Import the functionality presently available in the Fluka-SixTrack coupling: Check performed on-line; Aperture shapes: RECTELLIPSE-like, OCTAGON, RACETRACK; Smoothing of aperture model + estimation of actual loss point via bi-section method; including fixing of broken mapping! Extension to thick-lens tracking: extend back-tracking to (sliced/split) dipoles and quads; With care, as in coupled simulations there might nuclear interactions leading to more than a particle worth following the tracking (e.g. ion fragmentation) 8th Mar 2017 A.Mereghetti
11
Generation of SixTrack Input via MADX
Input to Fluka-SixTrack coupling: LHC: complex aperture model generated not directly with MADX, merging .tfs aperture file and a survey file; SPS: generation can be already done with MADX (only ELLIPSEs and RECTANGLEs); Using MADX only would make things more robust, self-consistent and clean; SixTrack input files are (mostly) automatically generated by MADX via the sixtrack command; aperture flag of sixtrack command: allows to dump the respective aperture marker immediately after each lens in the lattice structure – “present” (modulo planning/timing of pro release) implementation: Only aperture types available in native SixTrack (RECTANGLE, ELLIPSE, CIRCLE); Optimisation of unique definitions of aperture markers (single elements); 8th Mar 2017 A.Mereghetti
12
Generation of SixTrack Input via MADX (II)
In order to provide the on-line aperture check with complete information via MADX, some updates are required; Some work already done: MADX ticket 351 (closed): Update format of LIMI block automatically generated: 4 aperture specifiers + 2 offsets + 1 tilt; (Fixing units); Still needed: When slicing a sequence, add an aperture marker at beginning / end of the active length of the thick element code by H.Burkhardt MAKETHIN module? Offsetting aperture (separation/recombination dipoles) with reasonable longitudinal resolution (set by user, as done in the APERTURE module); Optimise sequence of aperture markers, e.g. avoid repetitions over the same piece of DRIFT; …can we make for the next pro release? 8th Mar 2017 A.Mereghetti
13
Conclusions Some mechanisms for aperture checking are available in different versions of SixTrack (native / for collimation / coupling to Fluka); to converge is synergic to all involved applications / studies: Merging the assets of all the approaches and overcoming liabilities; Ease of code maintenance; Road map was shown, including requirements on the MADX side (input generation); 8th Mar 2017 A.Mereghetti
14
Spare Slides 8th Mar 2017 A.Mereghetti
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.