Initial LIGO improvements Advanced LIGO P Fritschel PAC

Initial LIGO improvements & Advanced LIGO P Fritschel PAC Meeting LLO, 18 May 2005 G 050259 -00 -D LIGO I

General considerations q Any upgrade must account for time to install and fully commission it, plus time for running! q Plan should favor technologies, techniques, subsystems that are part of Advanced LIGO q Plan should consider contingency options for potential Ad. LIGO delays q Initial LIGO components/features that are not candidates for upgrade Ø Core Optics (except possible spare replacements) Ø Isolation stacks Ø IFO beam path (e. g. , no suspension change that moves the optic) G 050259 -00 -D LIGO I 2

Initial LIGO fundamental noises SRD, 14 Mpc 8 W into MC 5 x 10 -4 + beam offset 2 x 10 -3 G 050259 -00 -D LIGO I See also Rana Adhikari’s thesis 3

Astrophysical impact of a modest improvement q How does the number of surveyed galaxies increase as the sensitivity is improved? From astro-ph/0402091, Nutzman et al. , “Gravitational Waves from Extragalactic Inspiraling Binaries: Selection Effects and Expected Detection Rates” For NS-NS binaries Power law: 2. 7 Factor of 2 reduction in strain noise, factor of 6. 5 increase in MWEG Prop. to inspiral range G 050259 -00 -D LIGO I 4

Sensitivity to Virgo cluster Effect of reducing min freq: Effect of reducing noise floor: Factor of 1. 8 in noise min Upgrade? SRD f_min = 225 Hz f_min = 150 Hz S 4 f_min = 100 Hz NS-NS (same shape as SRD) Data courtesy of Philip Nutzman G 050259 -00 -D LIGO I 5

Detection rate estimates Assuming factor of 6 increase in surveyed volume: Source Initial LIGO Improved NS-NS ~1 / 3000 yrs to ~1 / 3 yrs ~1 / 500 yrs to ~2 / yr NS-BH ~1 / 5000 yrs to ~1 / 3 yrs ~1 / 800 yrs to ~2 / yr BH-BH ~1 / 250 yrs to ~2 / yr ~1 / 40 yrs to ~12 / yr G 050259 -00 -D LIGO I 6

Suspension options q Find that current wire suspensions operate at wire-loss limit Ø Optimize with beam position shift (1 cm down from center) q Find that current wire suspensions have excess loss Ø Design new clamping systems for the ends Factor of 2 -3 lower noise than SRD at 100 Hz Beyond current wire suspensions: more than 3 x below SRD q Two wire loops q Low-loss flexures q Cradle for optic, suspended by silica fibers Ø See G 020241 & G 020242 Research needed: In-vacuum test suspension, to investigate violin mode Q’s of current wire suspension, and potential variants G 050259 -00 -D LIGO I 7

Power increase: 4 x more laser power q Higher power laser Ø Amplify current Lightwave Electronics laser with commercial amp Ø Amplifier from Laser-Zentrum Hanover (LZH) Fiber-delivered pump light, as in Ad. LIGO design 4 rod amplifier Nd: YVO 4 G 050259 -00 -D LIGO I 8

Input Optics to handle it q New electro-optic modulators Ø Thermal lensing in current modulators (Li. Nb. O 3) would be too high Ø Use modulators developed at UFl for Advanced LIGO Ø RTP & RTA, 4 mm x 4 mm aperture, negligible thermal lensing at 100 W q New in-vacuum Faraday isolator Ø Current isolators produce beam drift, would lens too much at higher power Ø Use Ad. LIGO Faraday isolator, developed at UFl Ø Design uses birefringence & thermal lensing compensation; different polarizer type q Replace or clean mode cleaner optics ? Ø MC transmission only ~75% G 050259 -00 -D LIGO I 9

Output mode cleaner to handle the output power q Basic motivations Ø Quadruple the photodetectors: 4 16 ! Ø Acoustic noise: close to limiting sensitivity now (jitter on detection tables); H 1 -H 2 stochastic sensitivity limited by it Beam Steering Mode Matching 1% 1% sample ISCT 4 q Solution ISCT 6 Beam Steering Shutter OMC Locking OMC 1% Ø Output mode cleaner Ø In-vacuum detection bench 50/50 splitter Photodetectors G 050259 -00 -D LIGO I 10

OMC design options q Monolithic spacer cavity Ø Ø Ø HAM 6 Triangular or 4 mirror zig-zag Low finesse Sidebands pass on same FSR Easier design, HAM 5 or HAM 6 Could test DC readout with a higher finesse version q Suspended Ø Ø Same design as input mode cleaner High finesse Sidebands pass on next over FSR More complicated design, more expensive, HAM 5 and HAM 6 q Seismic isolation Ø Initial LIGO stack Ø Advanced LIGO HAM isolation G 050259 -00 -D HAM 5 HAM 4 ITMX BS RM ITMY LIGO I 11

Thermal compensation q Current thermal compensation system (TCS) on H 1 compensates for 100 m. W absorbed power Ø Working to extend this with a higher power CO 2 laser q If optics absorb at their expected level q Initial LIGO estimate: P_bs = 8 W*0. 65*40 = 200 W: Ø factor of 6 headroom q Potential that extra-absorbant core optics would be replaced G 050259 -00 -D LIGO I 12

4 x more power* & good wire suspensions + beam offset 14 Mpc 30 Mpc *Doesn’t include increased detection efficiency due to output mode cleaner G 050259 -00 -D LIGO I 13

Other possibilities q Add PEPI to the LHO test masses Ø Sensors (large part of cost) would be useable in Ad. LIGO Ø Could help with up-conversion q Dealing with wind noise (both sites) Ø Adding good tilt sensing to HEPI q Miscellaneous Ø Ad. LIGO electronics improvements: lower noise ADCs; new architectures for controls and monitoring Ø Detection table seismic isolation Ø Acoustic mitigation at LHO G 050259 -00 -D LIGO I 14