Slide 1 FP7: Collimator Wakefields program Building on the achievements in EuroTeV to provide a comprehensive system of knowledge of wakefield effects in collimators for nanoscale bunches in high energy machines Roger Barlow

Slide 2 Collimator Wakefields Why they are different Non-resonant. Short range intra-bunch effects only Bunches are non-Gaussian (due to sextupole magnets and the wakefields themselves). Transverse deviations are what matters High order angular modes (not just dipole) have to be considered Question: to what extent do wakefields effects degrade the luminosity?

Slide 3 Bunch shape Wakefield Also makes any adaptation of BDSIM tough Why not just use Gdfidl/ECHO/HFSS…?

Slide 4 Higher modes matter Merlin simulation of simple 1.9mm collimator. Geometric wakes – Raimondi formula 0.5 mm offset 1.0 mm offset 1.5 mm offset Modes Plots show y’ versus z after the collimator

Slide 5 Losses caused by Jitter in position at start of BDS leads to jitter in position at collimators and thus jitter in angle which spreads out focus at IP Nongaussian ‘banana’ bunches with tails give luminosity loss even when colliding head-on

Slide 6 What have we done Adapted Merlin simulations to include azimuthal and radial transverse kicks Extended Merlin simulations to include angular modes of arbitrary order Provide ability to easily implement different delta-wake formulae +++ Mechanism for deconvoluting bunch wake results from EM simulations Applications to ILC BDS Comparison with PLACET (in progress) See various PAC posters and EuroTeV reports

Slide 7 Objectives 1. A compilation of the delta wake formulae in the literature (some of them have to be unscrambled from their assumptions about beam bunch shapes). Appraisal of the limits of their validity, benchmarked against EM simulations and experimental results. Coding of these for different simulation programs (Merlin, Placet). Preliminary in Year 1, and then ongoing. 2. A library of numerical delta wakes for various proposed collimator shapes and materials, obtained from GdfidL and ECHO2D and perhaps other codes and then deconvoluted, with routines to implement them Preliminary in Year 1, and then ongoing. 3. Compendium of analytical and numerical formulae. Finalised at end of project 4. Analyses of the emittance growth/luminosity loss for various proposed BDS systems (hopefully these will show that all is well, but it has to be verified!) Ongoing through project

Slide 8 Is this infrastructure? 1 - What are Research Infrastructures? In the scope of the Community action, the term “research infrastructures” refers to facilities that provide essential services to the scientific community for basic or applied research. Only research infrastructures which have a clear European dimension or interest are being considered. They may concern the whole range of scientific and technological fields, from social sciences to astronomy, going through genomics or nanotechnologies. Examples include libraries, databases, biological archives, clean rooms, communication networks, synchrotrons, accelerators, telescopes. They may be “single-sited”, “distributed”, or “virtual”. Research infrastructures are essential tools for the development of leading-edge research in Europe in scientific and technological fields. By attracting users from various countries and through networking, they integrate and structure the scientific community in Europe and play a major role in the construction of the European Research Area. In many domains, they have a significant economical, social or environmental impact. EU Working document on the Research Infrastructures in FP7 29October 2004

Slide 9 Do collimator wakefields belong here? Discussions will proceed with Ralph Assman’s collimation package, but that is more focussed on protons and sLHC. There are useful common areas which we will explore, but it’s not an obvious fit

Slide 10 Benchmarking Experiments have measured collimator wakefields as kick factors Kick factors are not enough to describe the effects but they are a useful benchmark SLAC ESA measurements ongoing but more / better bpms needed. More experiments will surely happen at SLAC and elsewhere

Slide 11 Resources No materials Faculty (x1/3) – no problem RA from FP7 RA from Cockcroft – agreed (subject to 1st RA) PhD student – will be found

Slide 12 Costs for 3 years Resourc es Mat direct Mat. indirect People MonthsDirectIndirect Lab K€261K€ Request K€94K€ Total K€355K€

Slide 13 Downsize Cut effort / time 70%: 2 years not 3 50%: 1 RA not 2 30%: 1 RA for 2 years All objectives stay but in weaker form. Surveys less complete, verifications less complete, and (especially) less BDS analysis

Slide 14 Project vision Complete library of wakefield effects in various collimators, ways to implement them in simulation programs, benchmarked against experiments, and with applications to proposed machines