Katrin Dahl for the AEI 10 m Prototype team AEI 10m Prototype AEI 10 m Prototype and its Suspension Platform Interferometer The team Harald Lck: Pretty much everything... Kasem Mossavi: Vacuum system, infrastructure Stefan Hild : Interferometer sensing and control Kentaro Somyia: Caltech Alessandro Bertolini: Isolation Tables Michael Born: CDS, Interface SPI2CDS Fumiko Kawazoe:Frequency-Reference Cavity design and control Gerrit Khn : CDS and related infrastructure Bob Taylor: Suspension Systems Katrin Dahl :Suspension Platform Interferometer Christian Grf : Digital Control Tobias Westphal : Monolithic suspensions, IFO-control Alexander Wanner : Seismic Isolation Oliver Kranz : Suspension Platform Interferometer Daniel Gering : Interface SPI2CDS Andreas Weidner: Electronics 2 Ph.D Students Diploma Student Postdoctoral Research Fellow Research Fellow Staff scientist Lecturer Senior staff scientist Ken Strain: Scientific Leader of the 10m Prototype StefanGoler: Coordinator, Leader QUEST Research Group Benno Willke : Leader QUEST task group, high power laser AEI 10 m PROTOTYPE AEI 10 m Prototype and its Suspension Platform Interferometer 3 The AEI 10 m Prototype Goals: Maximal overlap with GEO-HF subsystems develop and prove as many of the techniques needed for GEO 600 upgrades as possible (e.g. PSL, digital control infrastructure) provide training for people who will install and run GEO-HF Provide ultra low displacement noise testing environment To probe at (and later go beyond) the SQL Entanglement of macroscopic test masses For geodesy/LISA related experiments ... 4 IFO 5 Frequency reference cavity: - Finesse ~ roundtrip length 24.6 m - mirrors 850 g - Triple cascade all steel wire pendulum suspension - monolithic all-silica last stage - silica suspension filaments of 28 m diameter g mirrors - triple cascaded pendulum suspensions The prototype hall 6 Vacuum system 7 Tubes: 1.5 m diameter Volume ca. 100 m 3 22 t stainless steel Tanks: 3 m diameter, 3.4 m tall Tank centers separated by 11.65m Roughing: One 170 l/s screw pump Main pumps: Two 2000 l/s turbo-molecular pumps Backing and differential pumping: Two scroll pumps 270 view After 12 hours of pumping mbar After about one week of pumping mbar 8 GEO600 tank 9 Walk-in tanks mm flanges to fit feed throughs 600 mm flanges to fit viewports 100 mm flanges to fit feed throughs Door into the tank S eismic A ttenuation S ystem One SAS per vacuum tank, optical table goes on top of SAS Improved version of HAM-SAS Resonance frequency around 0.1 Hz Up to 80 dB attenuation in both vertical and horizontal directions Angstrom residual motion above 1 Hz 11 Relative residual motions between the tables will be detected and stabilised by the SPI Horizontal table actuation 12 Vertical table actuation 13 Vertical table actuation 14 SPI AEI 10 m Prototype and its Suspension Platform Interferometer 15 Why a S uspension P latform I nterferometer ? Ease lock acquisition of cavities by reducing residual test mass motion Reduction of burden to actuators on the mirrors Testbed for GRACE follow-on and LISA related experiments Sets requirements on SPI 16 THE SPI Requirements: No specific lock point Control bandwidth 100 Hz 100 pm/sqrt(Hz) and mHz Heterodyne Mach-Zehnder interferometry Suits our needs best In-house knowledge 17 Heterodyne Mach-Zehnder IFO 18 Optical layout 19 Measurement bench 20 Beam height 45 mm Overall height below 65 mm Phase determination Phase is extracted from heterodyne signal by use of an hardware Phasemeter 1 based on FPGA chips 1.Preamplifier and A/D conversion Photocurrent converted to voltage Digitising signals results in time series 2.Single bin discrete Fourier transform Fourier transform at only one frequency complex amplitude of PD signal at f het 3.Signal combination of each QPD quadrant leads to phase, DC, Differential Wavefront Sensing (DWS) and contrast information 21 Illustration of DWS 1 developed for LISA Pathfinder, Heinzel G et al Class Quantum Grav Choice of parameters Due to the arm length mismatch (20 m optical path length) a highly stabilised laser is necessary: mHz for IR light (1064 nm) 22 Iodine stabilised Nd:YAG laser 23 Michael Trbs output power: 1 W Stabilisation via Modulation Transfer Spectroscopy Choice of parameters According to the arm length mismatch (20 m optical path length) a highly stabilised laser is necessary: mHz for IR light (1064 nm) Control bandwidth 100 Hz heterodyne frequency around 20 kHz new phasemeter interface needed 24 Phasemeter Interface 25 Transfer rate from phasemeter EPP to microcontroller ethernet around 1.9 kHz with 16 channels Choice of parameters According to the arm length mismatch (20 m optical path length) a highly stabilised laser is necessary: mHz for IR light (1064 nm) Control bandwidth 100 Hz heterodyne frequency around 20 kHz Thermal drifts requires components to be monolithically bonded to plate with low CTE (ClearCeram, CTE=0.4*10 -7 /K) 26 Optical layout 27 Expected transversal signals 28 contrast DC Phase difference [rad] DWS [rad] Transveral displacement of MW1 or MS1 [mm] Transveral displacement of MW1 or MS1 [mm] Transveral displacement of MW1 or MS1 [mm] Transveral displacement of MW1 or MS1 [mm] Red curve: PDCW1 Black curve: PDCS1 Expected longitudinal signals 29 contrast DC Phase difference [rad] DWS [rad] Longitudinal displacement of MW1 or MS1 [mm] Longitudinal displacement of MW1 or MS1 [mm] Longitudinal displacement of MW1 or MS1 [mm] Longitudinal displacement of MW1 or MS1 [mm] Red curve: PDCW1 Black curve: PDCS1 Expected rotational signals 30 contrast DC Phase difference [rad] DWS [rad] Rotation of MW1 or MS1 [mdeg] Rotation of MW1 or MS1 [mdeg] Rotation of MW1 or MS1 [mdeg] Rotation of MW1 or MS1 [mdeg] Red curve: PDCW1 Black curve: PDCS1 Modulation bench 31 Test setup 32 Use of vacuum compatible components (free of grease) Longitudinal displacement 33 Pitch 34 Yaw 35 Blind test 36 Blind test 37 Next steps Stabilisation loops Amplitude 20 kHz Optical pathlength difference stabilisation Bond optics Use CDS via phasemeter interface Install final setup inside vacuum envelope Calibrate signals Table actuation Reach design sensitivity 38