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

Talk Overview LASTI goals and timelines Overview of progress to date Previously proposed solution, new problems Proposed solutions Conclusions LSC Meeting August ‘03

Specific Advanced LIGO Program Tasks (‘01 - ‘06+): 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 (‘01 - ‘06+): 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

Laboratory and LSC Visitors (to date) LASTI People 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… 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 LSC Meeting August ‘03

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

High Bay Schematic Y-end HAM X-end HAM BSC Y-mid HAM PSL 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

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

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

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

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

External Pre-Isolators (EPI) K. Mason, MIT LSC Meeting August ‘03

External Pre-Isolators (EPI) 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 (mseism) J. Giaime, LLO/LSU LSC Meeting August ‘03

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

LASTI Interferometer Sensitivity Model For sapphire TM’s (baseline plan) QTM= 2e8, Fcoating= 4e-4 6W laser power (LIGO I laser) Cavity finesse 2000 16m 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

(Silica Test Mass Option) For silica TM’s (backup plan) QTM= 3e7, Fcoating= 4e-4 6W laser power (LIGO I laser) Cavity finesse 2000 15m 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

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 = 422.5 kg ETM Suspension mass = 472.5 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

Active Seismic Isolation LSC Meeting August ‘03

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 LSC Meeting August ‘03 R. Jones, Glasgow U.

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 -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

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

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

Predicted MC Operation Beam jitter only known 100 Hz Calculated using AdvLIGO Parameters High power curve ignores VCO, beam jitter noise Relies on alternative OSEM strategy LSC Meeting August ‘03

Predicted Single Arm LASTI Performance (Low Power) 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

Predicted Single Arm LASTI Performance (Higher Power) 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 LSC Meeting August ‘03

Comments on Aggressive LASTI 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. Ref E. Calloni et al. Optics Communications 142 (1997) 50-54 LSC Meeting August ‘03

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

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

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