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Harald Lück for the GEO team

The GEO-HF Project. Harald Lück for the GEO team. ILIAS Meeting Palma, October 2005. What is GEO-HF ?. A research and upgrade program instead of the name of a new detector sequential upgrades of GEO600 (similar to LIGO+ / VIRGO+ ) prototype research to prepare these upgrades

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Harald Lück for the GEO team

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  1. The GEO-HF Project Harald Lück for the GEO team ILIAS Meeting Palma, October 2005

  2. What is GEO-HF ? • A research and upgrade program instead of the name of a new detector • sequential upgrades of GEO600 (similar to LIGO+ / VIRGO+ ) • prototype research to prepare these upgrades • support transit of 3rd generation Lab research to detector subsystems or detector configuration

  3. Optical Layout interferometer with „dual recycling“ modecleaner 12W Laser detector

  4. GEO600 Noise Sources (Design values)

  5. GEO600 Noise Sources (Design values)

  6. GEO HF - Motivation • Provide scientifically interesting data with the GEO instrument until 2014 • optimized at low frequencies for network analysis or • optimized for high frequency sources • Perform developments and tests towards third generation detectors • technologies, materials and optical schemes • Maintain capability to do high-fidelity measurements • Discover and analyze additional noise sources • keep team of experts in GEO collaboration → upgrade GEO600 and work on prototypes

  7. Shot Noise

  8. High Frequency Sources

  9. Possible way forward for ‘GEO-HF’ • improvements without changing mirrors • increase circulating power • improve thermal compensation scheme • optimize signal recycling bandwidth • use squeezed light to reduce shot noise • change main mirrors • reduce coating thermal noise if possible • further increase circulating power and / or reduce signal recycling bandwidth

  10. Changes interferometer with „dual recycling“ modecleaner Laser detector increase laser power 40W / 200W

  11. Nd:YAG 200W Laser System 200W 12W 0.8W

  12. Injection-Locked Single Frequency Power 300 250 200 200 Slope: 30 % 150 Output Power [W] 150 100 Output Power [W] 50 100 0 400 500 600 700 800 900 1000 1100 1200 Pump Power [W] 50 230 2 225 W; M =1,45 225 0 00:00 00:10 00:20 00:30 00:40 2 218 W; M =1,3 220 Time [hh:mm] 2 215 W; M =1,2 Output Power [W] 215 2 213 W; M =1,14 210 205 930 940 950 960 970 Pump Power [W] P = 195 W  continuous single-frequency operation >8h

  13. 4 Rod Nd:YVO4 Amplifier 39W output power11W seed / 115W pump 2/8/2 mm Nd:YVO4 rod GEO 600 style 11W seed laser

  14. Changes interferometer with „dual recycling“ modecleaner Laser detector • mid-arm pumping • new gate valves reduce Finesse of MC to keep peak intensity constant

  15. Changes interferometer with „dual recycling“ modecleaner Laser detector • (reduce absorption) • thermal compensation

  16. Squeezed light 600 m Power- Recycling mirror 600 m Laser Signal-recycling mirror Faraday Rotator Squeezed state Photo diode

  17. Rotated Squeezing Ellipse

  18. Table Top Setup

  19. Sqeezing Enhanced Signal/Noise

  20. Optional Changes interferometer with „dual recycling“ modecleaner Laser detector replace main mirrors

  21. Further GEO-HF optional changes • based on thermal noise considerations we consider replacing the end mirrors with new mirrors • better coatings (mechanical and optical losses) if available • possibly switch to silicon/ sapphire if thermal noise performance is better than in fused silica Coated fused silica mirror for GEO600 ~18cm diameter

  22. Thermal Noise for GEO Main Optics

  23. Ongoing lab work on coatings • Considerable work in LIGO Scientific Collaboration and elsewhere on studies of coating loss • Results suggest: • Ta2O5 is dominant source of coating dissipation • doping Ta2O5 with TiO2 can reduce dissipation by ~factor 2 • Further, studies by Pinto et al suggest by using multi-layers of ‘non-standard’ periodicity fraction of lossy high index material may be reduced?

  24. Silicon future detectors e.g. GEO-HF, EGO Silicon suspension technology. • Strong interest in cryogenic silicon for use in ‘3rd generation detectors’ • Laboratory studies ongoing on: • fabrication of, and dissipation in, silicon suspension elements • intrinsic dissipation in bulk silicon • fabrication and dissipation of monolithic silicon pendulums

  25. Thermal noise options

  26. Prototype Work within GEO-HF • Glasgow (in operation): • Advanced Configuration Prototype • Cryogenic Materials Test System • Hannover (planned): • test subsystem before installation in GEO • active seismic isolation system • digital control • fast mirror installation tools and techniques • test 3rd Generation techniques and configurations

  27. GEO-HF Summary • We plan to operate a flexible GW detector in a worldwide network until advanced IFOs come online. • Sequential upgrades to improve high frequency sensitivity will be made. • higher circulating power • lower coating thermal noise ( ? ) • squeezed light injection • GEO collaboration will operate prototypes to prepare these upgrades and • to support the transit of 3rd generation Lab research to the detector subsystems or detector configuration level. • Timeline: starting upgrading after extended data taking 2007/2008 • Proposal for ~3.5 M€ approved by MPG

  28. Lowest loss obtained so far = (9.6 +/- 0.3) x 10-9 Comparable with the lowest loss factors measured at room temperature (consistent with results by Mitrofanov et al from earlier times) (Cryogenic measurements in preparation) Results for silicon at room temperature Measured loss factors for two samples of bulk silicon The doped [111] sample typically showed lower dissipation, though whether this was due to the crystalline orientation of the sample, the dopant, or some other reason, is as yet unknown.

  29. Controlling the SR bandwidth Bandwidth  Finesse of the SR cavity  Reflektivity of MSR Signalrecycling-Etalon (r=150mm, d=75mm) Reflectivity is controlled by temperature Heater

  30. Diffraction Gratings 1st order Littrow 2nd order Littrow

  31. All-Reflected Cavities University of Jena

  32. Title: The GEO-HF Project • Abstract: The GEO 600 gravitational wave detector uses advanced technologies like signal recycling and monolithic fused-silica suspensions to achieve a sensitivity close to the km scale LIGO and VIRGO detectors. As soon as the design sensitivity of GEO600 is reached the detector will be operated as part of the worldwide network to acquire data of scientific interest. The limited infrastructure at the GEO site does not allow for a major upgrade of the detector. Hence the GEO collaboration decided to improve the sensitivity of the GEO detector by small sequential upgrades some of which will be tested in prototypes first. The development, test and installation of these upgrades are named "The GEO-HF Project" and this contribution will give a status report on this project.

  33. contents • GEO600 • description • current sensitivity • limits • GEO HF Detector • motivation • sources • ways forward • increase circulating power and power handling capability • change optics if coating technology allows for lower coating thermal noise • use squeezed light • GEO HF Prototypes • test subsystems / optical layout before installation • test installation procedures for fast installation at site • allow for high displacement sensitive measurements • test and develop third generation materials, optical readout schemes, control schemes

  34. Improvements to GEO sensitivity possible by changing to silicon mirrors? – possible option.

  35. Improvements to GEO sensitivity possible by changing to silicon mirrors? – possible option.

  36. Uses: Substrate loss of 1 x 10-7 (Suprasil mirrors) Current SiO2/Ta2O5 coatings Current estimate of thermal noise limited sensitivity of GEO -22 10 -23 10 -24 10 1 2 3 4 10 10 10 10 -21 10 substrate, loss = 1e-7 standard coating Total (coating + substrate) ] Hz Ö h [/ Frequency [Hz]

  37. Squeezing vs Quadrature Phase squeezing Phase squeezing Phase squeezing Phase squeezing Frequency dependent squeezing, (single filter cavity) Squeezing at 45° Squeezing at 45° Squeezing at 45° Squeezing at -45° Amplitude squeezing Amplitude squeezing R. Schnabel et al., Class. Quantum Grav. 21, S1045 (2004)]

  38. Assume: Loss in Suprasil = 5 x 10-9 In this case we would then be limited by coating thermal noise  strong interest in reducing coating dissipation Estimated GEO600 thermal noise – high Q value -21 10 substrate, loss =1e-7 substrate, loss =5e-9 -22 10 ] Hz h [/Ö -23 10 -24 10 1 2 3 4 10 10 10 10 Frequency [Hz] Limit set by coating thermal noise alone

  39. Possible improvements to thermal noise limited sensitivity of GEO for better coatings -21 10 -22 10 ] Hz h [/Ö -23 10 -24 10 1 2 3 4 10 10 10 10 Frequency [Hz] Thermal noise from: substrate, loss = 5e-9 standard coating Standard coating+substrate Coating using doped Ta2O5 Doped coating+substrate Reduced coating noise using Non-Standard Periodicity (NSP) ?????– Pinto et al NSP coating+substrate 4 Studies of coating loss ongoing – (see poster by G. Cagnoli)

  40. GEO Simulated Noise – high Q

  41. Studies of silicon as a test mass substrate Clamp Suspension thread/wire • Preliminary room T measurements made of mechanical dissipation of bulk silicon samples suspended on silk thread or wire loops • Internal resonant modes of the samples excited; decay of mode amplitude measured Test mass To high voltage Excitation plate (behind mass) Schematic diagram of front view of suspended test mass. • Dissipation of two silicon samples of identical geometry, supplied by collaborators in Stanford, was measured over a range of frequencies. Silicon samples cut along different crystal axes, [111] and [100]. The [111] sample was boron-doped.

  42. Shot Noise in SR IFOs

  43. GEO600 sensitivity evolution

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