FD Stabilization in NLC

Transcription

1 FD Stabilization in NLC Andrei Seryi SLAC LC02, WG4 February 7, 2002

2 Antivibration work for NLC: Joint efforts of many people SLAC Chris Adolphsen Fred Asiri Gordon Bowden Marty Breidenbach John Cogan Carlos Damian Eric Doyle Leif Eriksson Joe Frisch Linda Hendrickson Tom Himel Frederic Le Pimpec Tom Markiewicz Rainer Pitthan Tor Raubenheimer Robert Ruland Andrei Seryi Steve Smith Peter Tenenbaum Mike Woods Nancy Yu CERN Ralph Assmann Stefano Redaelli FNAL Joe Lach Chris Laughton Duane Plant Vladimir Shiltsev BINP Andrei Chupira Anatoly Medvedko Mikhail Kandaurov Vasili Parkhomchuk Shavkat Singatulin Evgeny Shubin Northwestern Univ. Heidi Shellman Mayda Velasco et al. UBC Tom Mattison Russ Greenall Parry Fung Oxford Phil Burrows Simon Jolly Gerald Myatt Gavin Nesom Colin Perry Glen White Brookhaven Nick Simos Stanford Sri Adiga

3 In this talk: Tools used for simulation of LC FD stabilization description examples of results Inertial, optical stabilization of FD; feedforward correction Test facilities

4 Tools: MATLAB-LIAR-DIMAD These tools include All the LC physics as included into LIAR-DIMAD Ground motion model given by P(w,k) spectrum Possibility to simulate 2 beamlines (e+ and e-) with proper GM correlation Transfer functions (TF) between GM and girder Additional technical noise (uncorrelated to GM or to other tech noises) TF and tech noises can be arbitrary assigned to a girder Active stabilization can be modeled by modifying TF

5 Once you have data on ground motion and vibration (+correlation!) Build a modeling P(ω,k) spectrum of ground motion (if necessary, add technical noise to specific locations, like detector) Then make simulation how LC performs Apply corrections, feedbacks, optimize them Decide whether this ground motion or parameters of LC are acceptable

6 Example: GM effect on TESLA and NLC NLC: DR -> IP TESLA: Linac + BDS (without bunch compressor) Mat-LIAR/DIMAD simulation with ground motion Two beamlines (e+ and e-) next page results are preliminary

7 128 pulses of NLC Beam-beam deflection feedback will make this curve flat with σ =0.8nm Idealized beam-beam deflection feedback : 1 for f>f c (f/ f c ) 2 for f<f c where f c =Frep/20 ( more real should also include small amplification at slightly above f c ) Seeds may be different unless stated otherwise.

8 1024 pulses of NLC BDS Beam-beam deflection feedback makes this curve flat with σ =0.65nm

9 128 pulses of TESLA Seeds are different on all pictures. Not for direct comparison.

10 Assumptions: NLC - The Next Linear Collider Project NLC BDS with active stabilization of FD, intermediate GM +additional noise at detector FD placed at +- 8m GM model B (given by P(w,k)) Added tech noise in FD support Tech noise at FD e+ and FD e- are uncorrelated! Stabilization/correction modeled by this TF Same GM seed is used in examples shown below

11 NLC BDS with active stabilization of FD, intermediate GM + noise at detector No FD noise w beam-beam defl.fdbk => σ = 0.72nm With FD noise w beam-beam defl.fdbk => σ = 12.3nm With FD noise & stabilization w beam-beam defl.fdbk => σ = 0.36nm

12 NLC BDS with active stabilization of FD, intermediate GM + noise at detector With additional FD noise & Stabilization

13 NLC BDS with active stabilization of FD, intermediate GM + noise at detector With FD noise Beam sizes are not disturbed at this time scale and parameters Rms energy spread of the input beam was 0.3% With FD noise & stabilization

14 NLC BDS with active stabilization of FD, intermediate GM + noise at detector In this idealized example, if GM B, no FD noise => σ = 0.72nm If there is FD noise, then: No FD active correction => σ = 12.3nm With active FD stabilization given by idealized TF => σ = 0.36nm Such TF can be provided by different methods Correction w.respect to ground (optical anchor) may result in σ ~ 0.72nm or even less, depending on where the reference is taken

15 R&D on inertial stabilization of FDs Inertial sensors Springs & electrostatic pushers Feedback ON Joe Frisch, et al. Single small object in 6D. Later extended object(s) Digital real time OS

16 Active stabilization options Position stabilization via feedback sensor quad Correction of magnetic center motion sensor quad Dipole corrector spring mover Good: 1/ω 2 attenuation above resonance; FD decoupled from noise source Concern: Need to act against inertia; Vibrations occurring inside FD; External forces acting on FD Good: Less sensitive to external forces; To correct field is easier; May correct for multiple reasons of magnetic center motion; Concerns: Effectiveness of feedforward; Internal vibration modes Coupling to external high freq noises

17 Optical Anchor concept: tie FD to stable rock

18 Demonstrated required resolution Developed by Mike Woods, SLAC

19 Optical Anchor R&D => UBC Canada 1D stabilization of an object 2nm Test of photodiode fitting algorithms Tom Mattison, UBC Partially assembled platform. Feb.2001

20 University of British Columbia Status as of Oct.2001 Optical Anchor R&D continues UBC team: Tom Mattison Russ Greenall Parry Fung Sub-nm stability (resolution) Test platform Interferometer signal used to close feedback loop Now optimization of hardware and feedback algorithm

21 One of the goals of LINX facility is to master FD stabilization LINX FF NLC FF LINX IR

22 LINX FFS with active stabilization of FD, intermediate GM + noise at detector No FD noise w beam-beam defl.fdbk => σ = 0.85nm With FD noise With FD noise & stabilization w beam-beam defl.fdbk => σ = 14.3nm w beam-beam defl.fdbk => σ = 0.58nm

23 LINX FFS with active stabilization of FD, intermediate GM + noise at detector With additional FD noise & Stabilization

24 LINX FFS with active stabilization of FD, intermediate GM + noise at detector In this idealized example, if GM B, no FD noise => σ = 0.85nm If there is FD noise, then: No FD active correction => σ = 14.3nm With active FD stabilization given by idealized TF => σ = 0.58nm Correction w.respect to ground (optical anchor) may result in σ ~ 0.85nm or even less, depending on where the reference is taken

25 Summary Stabilization of FD may be quite essential R&D on several methods of stabilization are ongoing Modeling tools exist to help understand their performance Stabilization/correction depends on very important technical details and optimization requires realistic prototyping