Advanced LIGO Suspensions Brett Shapiro for the SUS
Advanced LIGO Suspensions Brett Shapiro, for the SUS Group Detector Characterization Telecon 25 August 2011 G 1100866 -v 8 1
Contents • • i. LIGO to a. LIGO Seismic Isolation Sensors and Actuators: BOSEMs and AOSEMs Suspension Overview Signals and Control SUS Testing What can you do? G 1100866 -v 8 2/33
i. LIGO to a. LIGO Better Seismic n o i t a l o s I Red The uced rm Noi al se G 1100866 -v 8 Kissel – thesis defense, P 1000103 d e s ea wer r c In r Po l e igna s a L d. S g an cyclin Re 3/33
Suspensions and Seismic Isolation – From Initial to Advanced LIGO coarse & fine actuators 4 layer passive isolation stack single pendulum on steel wire Ref: LIGO-G 1000469 -v 1; Kissel Ph. D thesis hydraulic external preisolator (HEPI) (one stage of isolation) G 1100866 -v 8 quadruple pendulum (four stages of isolation) with monolithic silica final stage active isolation platform (2 stages of isolation) 4/33
z An a. LIGO HAM Chamber x y HAM 2 (Chamber hidden for clarity) G 1100866 -v 8 5/33
Five Suspension Designs Ref: G 100434 6 G 1100866 -v 8 6/33
SUS group ITM, ETM PR 3, SR 3 PRM, PR 2, SRM, SR 2, IMC Other suspensions + Trans. Mon G 1100866 -v 8 7/33
Suspension Isolation Performance 1/f 2 1/f 4 Each stage provides 1/f 2 isolation G 1100866 -v 8 1/f 6 1/f 8 8/33
Optical Sensor Electro. Magnet (OSEM) Birmingham OSEM (BOSEM) G 1100866 -v 8 BOSEM Schematic Advanced LIGO OSEM (AOSEM) - modified i. LIGO OSEM Magnet Types (M 0900034) • BOSEM – 10 X 10 mm, Nd. Fe. B , Sm. Co 10 X 5 mm, Nd. Fe. B, Sm. Co • AOSEM – 2 X 3 mm, Sm. Co 2 X 6 mm, Sm. Co 2 X 0. 5 mm, Sm. Co 9/33
Displacement (m/Hz 0. 5) BOSEM Sensor Noise Ref: T 090496 -v 4 G 1100866 -v 8 a. LIGO 10 Hz goal: 10 -19 m/Hz 0. 5 Frequency (Hz) 10/33
Sensor Feedback Only to Top Mass 10000 times higher! a. LIGO 10 Hz goal: 10 -19 m/Hz 0. 5 G 1100866 -v 8 11/33
Output Mode Cleaner Double (OMCS) In use during S 6 Location • HAM 6, (12) Control • Local – damping at M 1 (true for all SUS’s) T 3 LF T 2 M 1 RT T 1 SD Sensors/Actuators • BOSEMs at top mass Top mass naming convention • L 1: SUS-OMC_M 1… site subsystem unit stage 2 3 3, 4 2 M 2 Optics Documentation • Final design review - T 0900060 • HAM SUS controls arrangement – E 1100109 G 1100866 -v 8 V T Local coordinates L 12/33
HAM Small Triple Suspension (HSTS) Purpose T 1 • PRM, PR 2, SRM, SR 2 • MC 1, MC 2, MC 3 SD Location • HAM 2, 3, 4, 5, (8, 9, 10, 11) Control • Local – damping at M 1 • Global – LSC & ASC at all 3 Sensors/Actuators • BOSEMs at M 1 • AOSEMs at M 2 and M 3 • Optical levers and interferometric signals on M 3 Naming: L 1: SUS-PRM_M 1… Documentation • Final design review - T 0900435 • Controls arrangement – E 1100109 G 1100866 -v 8 T 2 M 1 LF T 3 RT UR UL M 2 LL LR UL UR M 3 LL LR V L T 13
HAM Large Triple Suspension (HLTS) Purpose • PR 3, SR 3 Location • HAM 2, 5, (8, 11) Control • Local – damping at M 1 • Global – LSC & ASC at all 3 Sensors/Actuators • BOSEMs at M 1 • AOSEMs at M 2 and M 3 • Optical levers and interferometric signals on M 3 Naming: L 1: SUS-SR 3_M 1… Documentation • Final design review – T 1000012 • Controls arrangement – E 1100109 G 1100866 -v 8 M 1 UR UL M 2 LL LR UL UR M 3 LL LR V L T 14/33
Beamsplitter/Folding Mirror (BSFM) Purpose • BS, (FMX and FMY) Location • Beamsplitter – BSC 2, (4) • (Fold Mirror – BSC 6, 8) Control • Local – damping at M 1 • Global – LSC & ASC at M 2 Sensors/Actuators • BOSEMs at M 1 and M 2 • Optical levers and interferometric signals on M 3 RT LF F 1 F 2 SD F 3 M 1 UR UL M 2 LL LR Naming: L 1: SUS-FMX_M 1… Documentation • Final design review - T 080218 • Controls arrangement – E 1100108 G 1100866 -v 8 M 3 V L T 15/33
Quadruple Suspension (Quad) Reaction Main (test) Chain R 0, M 0 L 1 L 2 Purpose • Input Test Mass (ITM, TCP) • End Test Mass (ETM, ERM) Location • H 1 - BSC 1, 3, 9, 10 • H 2 - BSC 7, 8, 5, 6 • L 1 – BSC 1, 3, 4, 5 Control • Local – damping at M 0, R 0 • Global – LSC & ASC at all 4 Sensors/Actuators • BOSEMs at M 0, R 0, L 1 • L 3 16/33 G 1100866 -v 8 AOSEMs at L 2 • Opt. levs. and interf. sigs. at L 3 • Electrostatic drive (ESD) at L 3 Documentation • Final design review - T 1000286 • Controls arrang. – E 1000617
Quadruple Suspension ESD Reaction Main (test) Chain UR UL LR LL G 1100866 -v 8 The electrostatic drive (ESD) acts directly on the test ITM and ETM test masses. • ± 400 V (ΔV 800 V) ≈ 100 μN • Each quadrant has an independent control channel • Common bias channel over all quadrants 17/33
Quadruple Suspension ESD F = αΔV 2 • α = coupling coefficient, depends on geometry Test mass • ΔV = differential voltage across traces Linearization occurs in the control! 5 mm Reaction mass Cartoon diagram illustrating the working principle of the ESD. The upper rectangle represents the test mass containing two polarized molecules; the lower rectangle represents the reaction mass bearing two electrodes. Surface plot shows electrical potential with electric field lines shown in cyan (John Miller Ph. D thesis, P 1000032). G 1100866 -v 8 18/33
Quadruple Suspension (Quad) Reaction Main (test) Chain R 0, M 0 Fibers L 1 L 2 L 3 Pulling a fiber at MIT 7 May 2010 G 1100866 -v 8 Newly welded monolithic quad at MIT 11 May 2010 19/33
Delicate Fibers G 1100866 -v 8 Video of breaking the monolithic test suspension fibers at MIT, 5 Nov 2010. To see how robust they are when they are not touched see http: //www. youtube. com/watch? v=ql. J 0 o 7 R 4 -LU 20/33
Quadruple Suspension (Quad) MIT monolithic quad in BSC June 2010 G 1100866 -v 8 21/33
Pendulum Coordinates Reaction Main (test) Chain • SUS control follows local pendulum coordinates • The ‘beam line’ does not always correspond to the IFO coordinates Interferometer coordinates y x Vertical (V) Yaw (Y) z Local Coordinates Transverse (T) Pitch (P) Longitudinal (L) Roll (R) Main chain top mass longitudinal: L 1: SUS-ITMX_M 0_L G 1100866 -v 8 22/33
Signal Flow – HSTS Bottom Stage Offload to next stage ISC Input Filters A D C Lock Filters Output calibrated to nm (nrad) OSEM Input Filters Output calibrated to nm (nrad) Control DOF Decoupling Matrix Frequency dependent Test Filters OSEM to Euler + Euler to OSEM Out Filters Coordinate transform Witness Filters Coordinate transform Actuator Outputs Tests Sensor Inputs G 1100866 -v 8 WIKI reference: https: //awiki. ligo-wa. caltech. edu/a. LIGO/Naming. Conventions 23/33 D A C
Signal Flow – HSTS Middle Stage Offload to next stage Inputs from previous stage Lock Filters Control DOF Decoupling Matrix Frequency dependent A D C Test Filters OSEM Input Filters Output calibrated to nm (nrad) OSEM to Euler + Euler to OSEM Out Filters Coordinate transform Witness Filters Coordinate transform Actuator Outputs Tests Sensor Inputs G 1100866 -v 8 WIKI reference: https: //awiki. ligo-wa. caltech. edu/a. LIGO/Naming. Conventions 24/33 D A C
Signal Flow – HSTS Top Stage Offload to next stage Inputs from previous stage Lock Filters Control DOF Decoupling Matrix Frequency dependent A D C Damping Filters OSEM Input Filters Output calibrated to nm (nrad) OSEM to Euler + Euler to OSEM Out Filters Coordinate transform Test Filters Coordinate transform Actuator Outputs Tests Sensor Inputs G 1100866 -v 8 WIKI reference: https: //awiki. ligo-wa. caltech. edu/a. LIGO/Naming. Conventions 25/33 D A C
Quad MEDM Overview Screen G 1100866 -v 8 26/33
Global Cavity Control (LSC) C 4 C 3 C 2 Cavity Length ITM G 1100866 -v 8 Each stage has limited range, so the control is distributed up the chain with: • Increasing control force • Lower frequency control C 1 ETM 27/33
Parallel Control of Cavity Length • With parallel feedback, changing one loop requires changing the others to account for changes in gain and stability. • The stability of all stages are coupled C 2 Cavity Length ITM G 1100866 -v 8 C 1 ETM 28/33
Hierarchical Control of Cavity Length • If each stage’s input is the output of the previous stage, any feedback change is automatically registered by the rest of the loop. • The stability at each stage is independent from the others. • Detailed discussion in T 1000242. C 2’ Cavity Length ITM G 1100866 -v 8 C 1 ETM 29/33
SUS Testing – G 1100693 • Top mass transfer functions • Sub-pendulum resonance measurements (lock stages down) • OSEM calibration – sensors and actuators • Cross-coupling tests • Magnet polarity checks • Active damping tests • Alignment range tests (drive OSEMs) • Structure resonances • The testing plan is still a work in progress! G 1100866 -v 8 30/33
Recent Transfer Functions H 2 ITMY just installed on BSC-ISI last week! G 1100866 -v 8 31/33
What can Det. Char do? • Damping: measure how much OSEM sensor noise makes it to DARM; look for pendulum resonant frequencies and Q’s. This will tell us how optimal our damping control is. • Study impact of undamped bounce and roll modes. Each triple and quad has a pair. How big are the peaks, do they ring up often? What are the Q’s? • Study impact of wire and fiber violin modes and acoustic modes of the optics. How big are the peaks? Ring up often? Some of these will have active damping. • Look for actuator saturation and RMS history; will tell us if the global control is distributed properly between stages. • Monitor long term alignment drifts in the suspensions. Ex. The masses rise and fall slightly with variations in temperature and pressure (quad mirror drops 1/3 mm under vacuum). • More ideas welcome. G 1100866 -v 8 32/33
a. LIGO SUS Team LLO SUS Team: Janeen Romie – HAM SUS lead eng Gary Traylor – SUS Install lead Carl Adams Anna Aitken Richard Biedenharn Derek Bridges Virginia Brocato William Elliott Anamaria Effler Matt Heintze Ed Merilh Mike Meyer Ralph Moffatt Bobby Moore Danny Sellers Gene Winton MIT SUS Team: Jeff Kissel – Testing lead Rich Mittleman – LASTI lead Sam Barnum Michael Hillard Brett Shapiro Sam Waldman LHO SUS Team: Mark Barton – HAM-SUS cog scientist Betsy Bland – SUS Install lead Jeff Bartlett Doug Cook Jesse Garner Robert Lane Gerardo Moreno Andres Ramirez Travis Sadecki Vern Sandberg Caltech SUS Team: Norna Robertson – SUS Leader Jay Heefner – SUS Electronics Lead Jay Copti Phillip Croxton Todd Etzel Kate Gushwa Alastair Heptonstall Kristen Holtz Tim Mac. Donald Gary Mc. Intyre Margot Phelps University of Glasgow (UK): Angus Bell Nicola Beveridge Alan Cumming Liam Cunningham Giles Hammond Jim Hough Russell Jones Rahul Kumar Sheila Rowan Ken Strain Marielle Van Veggel G 1100866 -v 8 Rutherford Appleton Lab (UK): Justin Greenhalgh Joe O’Dell University of Strathclyde (UK): Nick Lockerbie Kirill Tokmakov University of Birmingham (UK): Stuart Aston Ludovico Carbone Ron Cutler 33/33
Back Ups G 1100866 -v 8 34
G 1100866 -v 8 35
Single Suspensions • Modified i. LIGO SOS’s (Small Optic Suspension) – Addition of blade springs – Removal of side OSEM – Addition of eddy current damping • Steering and focusing auxiliary mirrors. • Located in HAM 2, 8 AOSEM G 1100866 -v 8 36
Trans. Mon Double Location • BSC 9, 10 Control • Local – damping at top mass Sensors/Actuators • BOSEMs at top mass Top mass naming convention • L 1: SUS-TRMX_M 1… G 1100866 -v 8 Ref: E 1000040 37
HAM 2 Layout Luke Williams, 22 Sept Ref: G 0900788 G 1100866 -v 8 38
HAM 3 Layout Luke Williams, 22 Sept Ref: G 0900788 G 1100866 -v 8 39
Different Suspensions ETM = end test mass ITM = input test mass BS = beamsplitter FM = folding mirror CP = compensator plate PR = power recycling mirror SR = signal recycling mirror IMC = input mode cleaner OMC = output mode cleaner SM = steering mirror IMMT = input mode matching telescope G 1100866 -v 8 Ref: LIGO-G 1000469 -v 1 40
Example Loop Gain of Cavity Control Cross over frequencies G 1100866 -v 8 41
SUS SVN T 1100117 -File_Directory Naming Convention G 1100866 -v 8 42
E 1000617 -v 3 G 1100866 -v 8 43
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