LIGO ADVANCED SYSTEMS TEST INTERFEROMETER (LASTI)

Transcription

1 LIGO ADVANCED SYSTEMS TEST INTERFEROMETER (LASTI) Program Update: LSC Meeting, Hannover Dave Ottaway August 2003 LSC Meeting August 03 1

2 Talk Overview 1. LASTI goals and timelines 2. Overview of progress to date 3. Previously proposed solution, new problems 4. Proposed solutions 5. Conclusions LSC Meeting August 03 2

3 LASTI Mission Test LIGO components & systems at full mechanical scale Practice installation & commissioning Minimize delays & downtime for advanced LIGO upgrades Qualify design mods & retrofits for initial LIGO Specific Advanced LIGO Program Tasks ( ): Qualify advanced isolation & suspension systems and associated controls at full scale Develop detailed SEI/SUS installation & commissioning handbook Look for unforeseen interactions & excess displacement noise Test PSL and Input Mode Cleaner together at full power LSC Meeting August 03 3

4 LASTI People Resident MIT Staff Students - Jamie Rollins, Stefan Ballmer, Dan Mason, Waseem Bakr Engineering -Myron MacInnis, Ken Mason, Jonathan Allen, Bill Rankin Scientists - Gregg Harry, Rich Mittleman, Dave Ottaway, David Shoemaker, Pradeep Sarin, Mike Zucker (Advice) Computers Keith Bayer Laboratory and LSC Visitors (to date) Initial SEI & SUS- Corey Gray, Hugh Radkins, Gary Traylor, Harry Overmier, Betsy Bland, Jonathan Kern, Marcel Hammond, Dennis Coyne Advanced SEI - Joe Giaime, Brian Lantz, Wensheng Hua, Corwin Hardham Advanced SUS - Norna Robertson, Calum Torrie, Janeen Romie, Phil Willems, Justin Greenhalgh, Ken Strain, Caroline Cantley, Mark Barton CDS/DAQ - Jay Heefner, Rus Wooley, Paul Russel LSC Meeting August 03 4

5 LASTI Advanced LIGO R&D Program Commission infrastructure (vacuum, cleanrooms, cranes ) Commission PSL & controls Commission initial seismic stack, suspensions & 1m test cavity in HAM chamber Develop & test EPI for LLO seismic remediation Qualification test of early pre-prototype triple pendulum (Delayed) Integrate/test active HAM SEI pathfinder (Delayed) Integrate/test active BSC SEI pathfinder (Delayed) Integrate/test Quad and Triple suspensions Integrate/test sapphire & fused silica core optics Qualify for low displacement noise with sensitive interferometer system Integrate and test full scale adaptive thermal compensation Integrate/test AdLIGO 180 Watt PSL & Mode Cleaner LSC Meeting August 03 5

6 High Bay Schematic X-end HAM BSC Y-mid HAM PSL Y-end HAM Currently planned to use the Y-arm More space around the X-arm BSC orientated such that layout mimics: ETM Chamber X arm, ITM Chamber Y arm Y mid with seismic isolation installed is not compatible for additional experiments if Y-end HAM is used for LASTI LSC Meeting August 03 6

7 LASTI Infrastructure and PSL LASTI PSL Mid Y HAM with MEPI BSC chamber including cartridge clean room LSC Meeting August 03 7

8 Pre-stabilized Laser (PSL) J. Rollins aligning PMC cavity D. Ottaway and J. Rollins commissioning controls LSC Meeting August 03 8

9 Intensity Stabilization Experiment Our approach: => Very low noise AC-coupled PD => Low voltage low noise parts in the signal path => Beam geometry stabilized by PMC LSC Meeting August 03 9

10 High Bandwidth FSS Servo Design Alternative high bandwidth frequency topology tried Achieved an upper unity gain frequency of 1 MHz Based on design by J. Hall LSC Meeting August 03 10

11 External Pre-Isolators (EPI) Magnitude Ground to Optical Table (Jun15) Ground to Optical Table (Jul23) Ground to Optical Table (loops off) K. Mason, MIT 10-4 Frequency (Hz) Coherence Ground to Optical Table (Jun15) Ground to Optical Table (Jul23) Ground to Optical Table (loops off) LSC Meeting August 03 11

12 External Pre-Isolators (EPI) J. Giaime, LLO/LSU Active vibration suppression interposed between ground and existing internal seismic isolation Main gravitational load is supported by angled coil springs (2 per leg) 2 forcers per leg, one vertical and one tangential Payload-mounted L-4C geophone + DC position sensor for local feedback STS-2 seismometer on floor permits feedforward at low frequencies (µseism) LSC Meeting August 03 12

13 Initially proposed Interferometric Noise Test Configuration 16 m ITM ETM RM RM MC3 MC2 MCx, MMTx, SM: Adv LIGO SOS ETM, ITM: Adv LIGO LOS MC1 PSL LSC Meeting August 03 13

14 LASTI Interferometer Sensitivity Model For sapphire TM s (baseline plan) Q TM = 2e8, Φ coating = 4e-4 6W laser power (LIGO I laser) Cavity finesse m cavity length 3mm beam radius (max. practical) Limited by thermoelastic noise over most of band due to small beam G. Harry, 6/25/02 LSC Meeting August 03 14

15 (Silica Test Mass Option) For silica TM s (backup plan) Q TM = 3e7, Φ coating = 4e-4 6W laser power (LIGO I laser) Cavity finesse m cavity length 2.25mm beam radius Limited by internal Brownian noise over most of band due to lower Q G. Harry, 6/25/02 LSC Meeting August 03 15

16 Summary of Initial Solution Two cavities proposed to provide common mode rejection of mode cleaner frequency noise and technical radiation pressure noise Problem : Proposed payload exceeds seismic limits Seismic mass limit = 800 kg Current payload mass ~ 1000 kg ITM Suspension mass = kg ETM Suspension mass = kg MC Suspension mass = 81.3 kg +spacer Possible solutions : Modify seismic for LASTI or modify/remove one of the reference cavities or anchor mirror catchers elsewhere LSC Meeting August 03 16

17 Active Seismic Isolation Internal active isolator External active isolator Existing LIGO I structure & vacuum chamber Quad-pendulum suspension (GEO/LIGO) LSC Meeting August 03 17

18 Advanced LIGO Suspensions Based on successful GEO600 triple pendulum design Quad pendula for TM, BS; Triples for input optics Blade springs for vertical isolation Indirect damping through upper stage recoil Electrostatic or photon drive for fast control at final stage; reaction mass for ES recoil R. Jones, LSC Glasgow Meeting U. August 03 18

19 More details of possible solutions Designing higher payload LASTI Seismic => Specifically testing Seismic then re-engineering to hold larger suspension weight Cons -Expensive, time consuming -Almost certainly better ways Anchoring catcher to vacuum chamber Cons -Not likely to be used in AdvLIGO, and hence not testing what is in Advanced LIGO Pros -Saves a lot of weight -No modifications necessary to LASTI Seismic LSC Meeting August 03 19

20 More details of possible solutions Using a single test cavity Mass closest to designed AdvLIGO seismic load Simplest design Potentially good performance if OSEM noise in MC can be overcome Also possible if global control can be used to damp the MC Alternatively turn damping off for short periods Using a second lighter cavity test cavity Possible solution if OSEM noise in MC cavity cannot be fixed Disable local damping rely on global control for damping Control problems and noise analysis to still needs to be done! LSC Meeting August 03 20

21 Parameter File for Calculations Test Cavity Parameters Length =16m Finesse = 2026 Modulation frequency = 9.8 MHz Mode Cleaner Parameters Length = 16 m Finesse = 2026 PD quantum efficiency = 0.9 Modulation frequency = 25 MHz Laser Power = 0.3 W (Low Power) Laser power = 0.3 W (Low Power) = 1.5 W (High Power) Spot size = 3mm (Conservative) = 1.5 W (High Power) = 16 mm (Aggressive) MC1,MC3 ROC = Flat Coating phi =5.0e-5 MC2 ROC = 26.9 m Input mirror substrate: Fused Silica Substrate phi = 1.0e-7 Spotsize = 2.7 mm Substrate mass =15 kg Coating phi = 5.0e-5 Input mirror ROC = Flat (Aggressive) Substrate phi = 0.3e-7 = 40 m (Conservative) End mirror substrate: Sapphire Substrate mass =3 kg Substrate phi = 1.0e-8 General Parameters Substrate mass = 40 kg Intensity noise =Advanced LIGO Requirements Output mirror ROC = 40 km Beam Jitter = LIGO 1 Measured PSL filtered by MC LSC Meeting August 03 21

22 Predicted MC Operation Frequency Noise (Hz/Hz 1/2 ) Advanced LIGO requirement Radiation pressure noise Shot noise VCO noise Best suspension Beam Jitter Noise Thermal noise Total noise (0.3 W att input) Total Noise (10 Watt input) Initial LIGO MC Beam jitter only known 100 Hz Calculated using AdvLIGO Parameters High power curve ignores VCO, beam jitter noise Relies on alternative OSEM strategy Frequency (Hz) LSC Meeting August 03 22

23 Predicted Single Arm LASTI Performance (Low Power) Length Noise (Hz/Hz 1/2 ) Frequency (Hz) Thermal Noise Thermoelastic Noise Radiation Pressure Noise Shot Noise MC Requirement Advanced LIGO MC Total Noise Aggressive Thermal Aggressive Thermoelastic Aggressive Beam Jitter Noise Power incident on mode cleaner =0.3 W Conservative LASTI not limited by MC noise Requires significant improvement over OSEM damping Should be possible with eddy current damping LSC Meeting August 03 23

24 Predicted Single Arm LASTI Performance (Higher Power) Frequency Noise (Hz/Hz 1/2 ) Thermal Noise Thermoelastic Noise Radiation Pressure Noise Shot Noise MC Requirement Advanced LIGO MC Total Noise Aggressive Thermal Aggressive Thermoelastic Power incident on mode cleaner =1.5 W Can reach AdvLIGO sensitivity at 1kHz if technical intensity noise is improved from 2e-6 to 5e-7 at 1kHz Frequency (Hz) LSC Meeting August 03 24

25 Comments on Aggressive LASTI Beam Jitter Noise Susceptability Parameters used:» Cavity length = 16 m» Input mirror roc =flat, Output mirror roc =40 km» Spot size = 16 mm» Alignment sensitivity 3e-7 radians for 1% power loss» Beam jitter not likely to be a problem based on static mis-alignment of 3e-7 radians and dynamic beam jitter limited by current PSL. Agressive LASTI Conservative LASTI πc( ε sε + βsβ ) ν ( f ) = 2( ε sβ + βsε ) f LF 2sin( α) 1 cos( α) 2sin( α + θm) 1 cos( α + θ ) m 2sin( α θ m) 1 cos( α θ ) m Ref E. Calloni et al. Optics Communications 142 (1997) Modulation Frequency/FSR LSC Meeting August 03 25

26 Updated milestones: LLO seismic remediation interleaved with Advanced LIGO development 4Q99 (4Q99 act): LASTI vacuum envelope commissioned 1Q00sch (3Q01 act): LASTI SEI external structures installed 2Q00sch (4Q00 act): LASTI infrastructure design review 3Q01sch (1Q02 act): LASTI infrastructure complete (DAQ, SEI, PSL, test cavity) NEW 4Q01: Fit LIGO I BSC stack (from spare parts) to support EPI qualification NEW 1Q02: External pre-isolator tests for LLO seismic retrofit underway NEW 4Q02: PSL intensity stabilization experiment underway NEW 4Q02: MC triple suspension prototype installed for controls pre-test 4Q02: HAM SEI pathfinder installed for standalone testing (slips to 3Q04) 3Q02: BSC SEI pathfinder installed for standalone testing (slips to 3Q04) 2Q04: LASTI noise test begins; SUS prototypes installed (slips to 2Q05) NEW: 2Q05: Thermal compensation integration and test 4Q05: Interferometric displacement tests 1Q06: LASTI SUS/SEI test review 2Q06: Adv LIGO PSL/MC tests start (180 Watts) LSC Meeting August 03 26

27 Short term plans (ie 6months) Finalize the design of the LASTI experiment for Advanced LIGO EPI» Test HEPI on a HAM» Finish conversion of controls from Dspace to VME Install a controls prototype in the Xend HAM LSC Meeting August 03 27

28 Conclusions LASTI s mission to pre-qualify Advanced LIGO technology has an unexpected dress rehearsal in the LLO seismic retrofit with the successful trial of HEPI/MEPI Need to find more information about MC suspensions before final decision can be made on the Advanced LIGO experimental program If mode cleaner suspension noise is significantly better than the radiation pressure limited Advanced LIGO specification can probably only require a single test cavity It may be technically feasible to significantly increase the spot size in the test cavity and measure noise at the Advanced LIGO displacement sensitivity (Not 10 X below) at 10 Hz and 1kHz LSC Meeting August 03 28