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Commissioning progress at GEO600

This document discusses the commissioning progress at GEO600, including investigation periods, power measurements, simulation improvements, and various technical issues. It also covers power failures, attempts to discharge charges, and improvements to the SR and clean-room cleanliness.

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Commissioning progress at GEO600

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  1. Commissioning progress at GEO600 Martin Hewitson for the GEO team WG1, Hannover, Jan 2007

  2. Overview - plans • Ended full-time S5 15 Oct 2006 • Back to commissioning, overnight/weekend mode • Planned work: • Investigation period • Power measurements, simulation improvements, etc • ESD AA for MID • Improve clean-room cleanliness • New HEPA filters for AC • Fix various mains problems • Filtering, ground loops, PE to neutral connections • Open central cluster • Exchange HV feedthroughs for ESDs (corroded) • Reposition beam block (scattering suspected) WG1, Hannover, Jan 2007

  3. Since the last meeting… • Investigations: • Power build-up • Power increase - instability, PUGs • ‘Ripple’ noise • Commissioning: • MID AA ESDs • SR longitudinal loop • Problems: • Significant series of power failures WG1, Hannover, Jan 2007

  4. Not in this talk • Power up stability, glitches • Detector not stable with full available input power • HOT TOPIC • Also observed large glitches in the past when at full power • Not observed recently so hard to investigate • Ripple noise investigations • See Josh’s talk WG1, Hannover, Jan 2007

  5. Running performance Post S5 running Power cut WG1, Hannover, Jan 2007

  6. PR build-up • Two reliable methods used to determine factor: • PR cavity pole • Direct measurement of power reflected from BS AR coating • Additional measurements of power transmitted at end mirrors • Less reliable due to low light levels WG1, Hannover, Jan 2007

  7. PR cavity pole Measurements of PR cavity pole give WG1, Hannover, Jan 2007

  8. PR build-up - Summary • PR pole and BS-AR measurements agree within 10% • Yield a build-up factor of 840-920 • Transmission at MFe gives build-up factor of 1410 (less confidence) Can be explained by 120-130 ppm/mirror WG1, Hannover, Jan 2007

  9. Site Power Failure - 02/12/06 • 3 power failures of increasing duration - last one around 40 minutes • Various systems damaged • MC turbo pump, computers, ESDs • North ESD damaged • 2 pairs of wires shorted inside vacuum • Diagnosed by current-limit of HVA • Some external rewiring to bypass the problem • Still less actuation after repair • 35% less on North drive, 65% less on East drive • All quadrants on East are working • What else? Charges on test-mass counter-act the dielectric effect of ESD which means less force WG1, Hannover, Jan 2007

  10. Charges on East test-mass • Lock with north only • Drive East drive with varying bias plus fixed ac (calibration) line • Measure line height in MID error-point • For un-charged test-mass line height should be zero for zero bias WG1, Hannover, Jan 2007

  11. WG1, Hannover, Jan 2007

  12. Attempts to discharge • UV attack • Shine UV into TCe • Knock of electrons from metal-work • neutralize test-mass • Venting central cluster with argon • Vented to 1mbar failed failed WG1, Hannover, Jan 2007

  13. Going on after power cut • Decide to stick with lower strength ESDs for now since we want to open vacuum anyway soon • Calibration adjusted to give old sensitivty • Checked with PPD • Loop gains adjusted for this state • So far seems not to cause too much trouble for locking WG1, Hannover, Jan 2007

  14. Improving SR long lock • Motivation: • Want to try PRAA for higher power • PR long noise couples to SR cavity • Want more SR long gain • Current SR long state: • Loop bandwidth is limited by how much feedback noise we can tolerate • Feedback is shot-noise above 100Hz • Previously using the AA quadrant diode for long error-signal • Installed SED resonant for 9MHz • Expect x2 lower shot-noise WG1, Hannover, Jan 2007

  15. Further improvements • Noticed coherence through dSPACE is not 1 • Limited by DAC noise • First tried flat gain factor for feedback • Then added whitening at feedback output WG1, Hannover, Jan 2007

  16. Using new SED for SR long • Lowers MSR feedback projection to H • We can use this gain to improve the control loop WG1, Hannover, Jan 2007

  17. New SR run-loop Relax feedback low-pass filtering allows more low-frequency gain for similar loop-stability margins WG1, Hannover, Jan 2007

  18. Cleaning up the clean-room • Additional HEPA filters installed for AC system • We have additional particle leak from pump-room due to over-pressure there WG1, Hannover, Jan 2007

  19. Coming up • Opening vacuum system • Reposition beam dump(s) and install translation stage(s) • Repair ESDs • Fix wiring and install new HV feedthroughs • Improvement of air-conditioning system • HEPA filters in clean room [done] • Continue work on power increase • Continue commissioning of MID ESD AA WG1, Hannover, Jan 2007

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