KAGRA future discussion 1 The 3 rd KAGRA International Workshop May 2017 Tokyo Institute of Technology Kentaro Somiya
KAGRA Advanced R&D It is not a subsystem but a group of activities for a future upgrade of KAGRA.
KAGRA Advanced R&D Advanced R&D subjects and past presentation slides are listed in the wiki page.
Discussion on a future upgrade • Some advanced techniques have been proposed • We shall integrate them to make a concrete plan(s) for the future upgrade of KAGRA • How much can we improve the current sensitivity? • In which timescale shall we consider the upgrade?
GW detectors Japan USA Europe TAMA LIGO 1G GEO Virgo Advanced GEO‐HF 2G LIGO Advanced KAGRA Virgo A+ 3G Voyager Einstein Telescope ? Cosmic Explorer
Sensitivities Inspiral range for BNS O2 KAGRA aLIGO A+ Voyager ET CE 70Mpc 150Mpc 200Mpc 320Mpc 700Mpc 3200Mpc ?
LIGOʼs plan in 2022~2024 A+ Voyager 300K Silica 120K Silicon 1064nm 1550nm SQ SQ 4km filter 16m filter Voyager is the final upgrade of LIGO in its current facility.
In the case of KAGRA • QN and Suspension TN limit the sensitivity • Mirror TN is small in 20K but not too small
How to calculate noise curves Simplified model Suspension thermal noise � � � for � � � � Mirror coating thermal noise � � � ��� � � � � � Quantum noise � � ��� ��� � � * Y:Youngʼs modulus, :Poisson ratio, d w :fiber diameter, l:fiber length, d coa :coating thickness
Looking back the design sensitivity in ʻ04 [LCGT document ver.1 (2004)] • BNS observation range was 188Mpc (current:158Mpc) • Susp TN and QN increased for lighter mass (50kg>23kg)
Adv. R&D (1): Squeezing [Matsumoto F2F 2011] [Somiya F2F 2014] [Flaminio F2F 2015] Freq-independent squeezing equivalent to high laser power Freq-dependent squeezing equivalent to heavy mass
Adv. R&D (2): non-uniform suspension [Nishida F2F 2011] h w [Sekiguchi F2F 2012] • Ribbon suspension • Thin-end fiber suspension
Adv. R&D (3): Vertical SPI [Ando F2F 2012] Measure the distance between upper and lower masses using interferometry
Integration of the techniques It is not enough to propose one technique to improve the overall KAGRA sensitivity. We shall combine multiple techniques to make a plan. We would like to have a few candidate plans by the next F2F meeting!
Trade-offs with some parameters Parameter Good Bad temperature increase, high laser power low shot noise parametric instability different wavelength, use of Silicon can be larger than Sapphire lower Youngʼs modulus thin fiber low suspension TN less cooling capability large beam low mirror TN diffraction loss, less stable thick mirror heavy mass more absorption at ITM (same radius) large radius large beam (low TN) more dissipation (high TN) (same mass) A proper combination of the parameters is necessary to achieve a good sensitivity.
Other ideas to improve the sensitivity • Non-cylindrical mirror to increase the mass • Non-cylindrical mirror to decrease TN • Composite mirror • 300K Silica ITM + 20K Sapphire ETM • Evanescent cooling • Crystaline coating • Delay line • Local readout • Balanced homodyne detector • EPR entanglement
How do we proceed? Today and Tomorrow My talk: introduction Haino-san: astronomical targets and technical feasibility Michimura-kun: example plans of “KAGRA+” For the next F2F meeting Pre-meeting/telecon to discuss future upgrades Discussion day/session at the F2F meeting Near future (maybe not now, until bKAGRA-I/II? finishes) We shall start to organize a working group to consider a strategy (technology, budget, human resources, etc.)
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