Linear Collider Alignment and Survey

1. Linear Collider Alignment and Survey “LiCAS” Visit of Jonathan Dorfan to RAL

2. Overview • Why and how Oxford wants contribute to a linear collider • LiCAS Phase I (build survey) • The survey problem • Our solution • Our Experience (ATLAS & ZEUS) • Our Resources • LiCAS Phase II (online alignment) • The alignment problem • Steps towards a solution Visit of Jonathan Dorfan to RAL

3. Why and how Oxford wants to contribute to a LC ? • Why: • Physics ! • Our technologies and expertise are applicable to collider survey and alignment • Beam instrumentation work already exists in UK • How: • Will be releasing large technological capabilities from ATLAS construction phase (next two years) • This gives ability to take up similar sized project • Open mind about other tasks Visit of Jonathan Dorfan to RAL

4. LiCAS Phase I(TESLA survey, build and repair) • Collider Survey • Collider alignment at build time 200 mm (vertical) over 600m • Today’s open air survey technology fails both in speed and accuracy • We want to build survey instrument that matches requirement • Apply our technologies (FSI, straightness monitors) to new problem Visit of Jonathan Dorfan to RAL

5. This is the main beam line Survey & Alignment are difficult Visit of Jonathan Dorfan to RAL

6. Many beam lines Very tight space (1m wide) Space also serves as emergency escape route Automated process (induced radiation environment, re-align without re-opening collider) Horizontally and vertically curved sections, (Rmin>500m) Some sections geometrically straight, others following geoid Some sections with significant slopes Electronically noisy environment No long-term stable reference monuments Special boundary conditions in TESLA Visit of Jonathan Dorfan to RAL

7. straightness monitors FSI-distance measurements reference markers tunnel wall straightness monitor beam single car with sensors LiCAS Phase I • Automatic survey train measures reference markers in tunnel wall • Later (not too late!!) measure collider against reference markers • Instrument internal lines in vacuum • Use scalable laser technology (EDFA & telecom style lasers) • Prototype @ DESY during FEL installation • Want same scheme for TESLA & NLC Visit of Jonathan Dorfan to RAL

8. LiCAS Phase I(Our experience with alignment so far) • FSI for ATLAS • Large scale O(800 lines) on-line survey system for the ATLAS inner detector. • Optimised for minimum mass • Self-calibration to silicon detector’s co-ordinate system using X-Ray scanning system • In large scale production now • Straightness monitors • Transparent silicon detector system for ZEUS vertex detector • Similar transparent Si from ATLAS muon system tested on TESLA undulators for FEL test beam line • CCD based system for ATLAS x-ray scanner Visit of Jonathan Dorfan to RAL

9. LiCAS Phase I & II (FSI extrapolation) 7th digit changes • Today: • s = 117 nm @ L=0.4m • sL/L = 0.29 ppm • Phase I: • s=1 mm @ L=5m • sL/L = 0.5 ppm • Phase II: • s=1 mm @ L=10m • sL/L = 0.1 ppm s =117nm L=4*108nm Visit of Jonathan Dorfan to RAL

10. ATLAS FSI components • Retro Reflectors • Quills Visit of Jonathan Dorfan to RAL

11. Alternative Solutions • Alternative scheme: • stretched wire over 25m for vertical position • hydrostatic levelling system for horizontal position • same train layout but different measurement modules • Drawbacks • not suitable for geometric straight or sloping sections (very important for NLC style collider !) • not suitable for “strongly” curved sections • many measurement steps to get to a single position • slow (many mechanical moves and measurements) • lower resolution (limits use as diagnostic tool after initial survey) Visit of Jonathan Dorfan to RAL

12. Grzegorz Grzelak Nikhil Kundu LiCAS Cast academic electronic mechanic +1 student

14. Project Constraints • Timescales: • short term: 1st year, compatible with DESY installation of TTF3 • medium term: 2nd-3rd year, compatible with DESY operation of FEL in TTF3 and similar test-beams else where. • long term: 4th- infinity, general development of LC alignment scheme for both TESLA and NLC • Funding: • short term: • Oxford PP internal, guaranteed 15K£ • Paul Instrument fund, possibly O(60K£), • medium term: PPAP project, Basic Technology fund • long term: funding together with LC project on UK scale Lots of good people Many good ideas Small capital funds Visit of Jonathan Dorfan to RAL

15. LiCAS Phase II(online alignment) Visit of Jonathan Dorfan to RAL

16. 70nm LCs move… (time scales of ground motion) Powerspektrum of ground motion in various HEP tunnels LEP: 60 to 180 mm/Jahr Visit of Jonathan Dorfan to RAL

17. relative beam motion wavenumber : 1/l [m -1] 1/25m …the beam moves even more(length scales of ground motion) • Relative beam motion vs. wavenumber of ground motion • But wavelength > 25m do not matter all that much Visit of Jonathan Dorfan to RAL

18. <1nm 25nm <8mm 8mm Magnet Sensitivities (position dependence) • Sensitivity S of magnets in FF of NLC • Drift < 5Hz < Jitter • Drift assumed to be corrected for by beam • S(Drift): 25nm - 8mm • S(Jitter): 0.5nm - 2.5 mm closer to interaction point Visit of Jonathan Dorfan to RAL

19. Effect on Luminosity (time scale) TESLA Luminosity versus log(time/sec) assume: ideal beam corrections, ATL groundmotion (HERA) must move magnets now 1week 2s 20s Visit of Jonathan Dorfan to RAL

20. LiCAS Phase II(online alignment) • Address “slow” alignment with f<O(Hz) • Fixed alignment Grid on most sensitive components (BDS, final focus) • Total length O(1km) • Total number of SM stations O(500) • develop cheap camera and readout system • Total number of FSI lines O(5000) • Profit from scalability and cheap telecom fibres/amplifiers • Add fixed frequency laser to FSI system and use as Michelson interferometer: • FSI gives O(mm) absolute alignment • Michelson Mode gives O(nm) stabilisation (optical anchor) • Prototype @ DESY in FEL operation • ESPI “afterburner” for straightness monitors ?? Visit of Jonathan Dorfan to RAL