CERN BEABP Accelerators and Beam Physics group Integrated

CERN, BE-ABP (Accelerators and Beam Physics group) Integrated simulations of ground motion effects in CLIC Jürgen Pfingstner Jochem Snuverink 12 th of January 2011 Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Outline 1. Introduction – Ground Motion – Stabilization & Feedback systems – Framework 2. Long term simulations 3. Short term simulations – Local stabilization development – Beam-based development 4. Conclusions Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) 1. Introduction Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Ground Motion Main dynamic cause for luminosity loss Slowly drifting element positions Short time scales (< 10 s) Micro-seismic peak – A. Seryi models [1] (see figure) Long time scales – ATL law: – <(Δy)2> = A*t*L Model A, B and B 10 used Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Ground Motion Jürgen Pfingstner and Jochem Snuverink Taken from D. Schulte Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Stabilization & Feedback systems Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Quadrupole Stabilisation Reduces quad movements above 1 Hz (int. rms 1 nm) Reduces emittance growth and beam jitter for high frequencies Taken from CERN stabilisation group (see [2]) Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Pre-isolator Taken from A. Gaddi et al. (see [3]) Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Pre-isolator Reduces movements of the Final Focus magnets above several Hz (int. rms 0. 13 nm) Reduces beam jitter (offset) at IP for high frequencies Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Beam-based feedback Orbit correction 2010 quads and BPMs per beamline Weighted SVD controller [4] – One large response matrix – Smaller singular values downweighted Robust against noise Reduces emittance growth for low frequencies Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) IP feedback Kicker IP BPM Feedback based on the deflection angle of the colliding beams Pulse to pulse (intrapulse possible, but not used here) Reduces beam offset at IP for low frequencies Non-linear effect In collaboration with LAPPAnnecy Taken from J. Resta-Lopez (see also e. g. [5]) Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Simulation Framework & Settings A simulation framework has been setup – Placet-CVS: /clic-integrated-simulations/linac-bds/dynamic – Main Linac and BDS, Placet for tracking – Guinea. Pig for luminosity calculation Ground motion generation for all models Including all feedback systems mentioned One settings file Scripts to run on batch and analyse results In development, more will be added Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) 2. Long term simulations Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) BPM resolution Impact of BPM resolution No ground motion, only BPM errors Required BPM resolution 100 nm for a few % loss Improved result due to noise-robust beam based feedback el. Luminosity Time [s] Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) ATL After some time the beam-based feedback is not able to maintain the nominal luminosity Further optimization procedures are required after about 10 minutes Can probably be improved by optimizing beam-based feedback Luminosity Jürgen Pfingstner and Jochem Snuverink Time [s] Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) 3. Short term simulations Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Luminosity with only IPFB (no pre-isolator) • Model B • beams are brought as good as possible into collision by the IPFB Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Luminosity with IPFB and pre-isolator • Model B • beam offset due to final focus motion is suppressed Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Luminosity with IPFB, pre-isolator and BBFB • Model B • beam size at IP is reduced due to the BBFB, but offset jitter is amplified Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Luminosity with IPFB, pre-isolator and BBFB and stabilization (LFB) • Model B Performance was not sufficient at Jürgen Pfingstner and Jochem Snuverink • offset jitter is thatdrastically time! reduced by the LB, but low frequency beam size growth is amplified!? Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Stabilization system transfer functions (TF) Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Performance of different stab. system TFs Guidelines for stabilization team: • No amplification at the micro seismic peak • Amplification around 75 Hz has to be kept small Performance still not good enough! Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Beam-based orbit feedback (BBFB) Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Why were only 16 SV directions used? Normalized projected emittance growth at the end of the main linac, due to excitation with the different controller direction. Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Effect of different controller direction on Lumi Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Modifications to the BBFB controller diag(Fold) [1] • If a 1 is too small: => Low frequency lumi. decrease, due to beam size growth • If a 1 is too big: => High frequency lumi. decrease, due to beam offset • Best value found: a 1=0. 05 • Further controller optimization possible Old controller a 0 = 1 a 2 = 0. 0001 2105 16 modes [1] diag(Fnew) [1] a 0 = 1 New controller a 1 = 0. 05 a 2 = 0. 0001 16 300 2105 Jürgen Pfingstner and Jochem Snuverink modes [1] Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Result with the modified BBFB controller Weak point of the BBFB found and fixed Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Final averaged result Luminosity averaged over approx. 15 seeds Only y-axis considered We HOPE the performance is good enough!? Average luminosity loss: • model A: 0. 9% • model B: 2. 8% • model B 10: 7. 0% Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) 4. Conclusions Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Conclusions • • A simulation framework for ground motion effects in CLIC was developed. It can be used: 1. as a test bench for algorithm design and optimization. 2. to verification the allover luminosity preservation in spite of ground motion (feasibility item of the CDR) The simulations delivered guidelines for the design of the stabilization system transfer function: 1. TF should be 1, around the 0. 1 -0. 4 Hz (micro-seismic peak) 2. It should also be kept small in the frequency range around 75 Hz (amplification from the orbit FB). Also a weak point of the orbit feedback was discovered and fixed. Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Conclusions cont. • Short term simulation: average luminosity decrease • Model A: 0. 9% • Model B: 2. 8% • Model B 10: 7. 0% • Long term simulation: • Further optimizations necessary after about 10 minutes (10% luminosity loss). • Optimization of the BBFB could probably improve the long term behavior. • Also continuous running of the ground motion countermeasures could improve the situation. Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Further information and references [1] A. Seryi, “Ground Motion Models for Future Linear Colliders”, EPAC 2000, Vienna [2] C. Collette et al. , “Active quadrupole stabilization for future linear particle colliders”, Nuclear Instrumentation and Methods in Physics Research A, 2010 [3] A. Gaddi et al. , "Passive Isolation", IWLC 2010, Geneva [4] J. Pfingstner et al. , “Adaptive Scheme for the CLIC Orbit Feedback”, IPAC 10, Kyoto, [5] G. Balik et al. , "Non-linear feedback controller", IWLC 2010, Geneva Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC

CERN, BE-ABP (Accelerators and Beam Physics group) Thank you for your attention! Jürgen Pfingstner and Jochem Snuverink Integrated simulations of ground motion effects in CLIC