New suspension study for LCGT Erina Nishida Ochanomizu

New suspension study for LCGT Erina Nishida Ochanomizu University The Graduate School of Humanities and Sciences The Division of Advanced Sciences/ NAOJ 1

LCGT Sensitivity There is a peak at 117 Hz l l Those depends on the fiber being thick and tunnel tilting. b. LCGT default parameters Arm length: 3000[m] Test mass: 30[kg] Mass temperature: 20[K] Suspension length: 0. 3[m] LCGT f 2 f meeting@Tokyo university, Japan, 5 th Aug, 2011 Erina Nishida 2

troublesome peak from data analysis • One of problem for data analysis is vertical mode at 117 Hz • LIGO mode frequency is about 300～ 400 Hz. • Sensitivity is worse. ( lower S/N→lower detection efficiency) • Power is unstable. (power fluctuation make detection efficiency worse) • It is difficult to analyze this frequency band. • Frequency band this mode could be widen. >> Laser amplitude noise, seismic noise, 4 wires… LCGT f 2 f meeting@Tokyo university, Japan, 5 th Aug, 2011 Erina Nishida 3

Simulation model fiber ribbon Mathmatica Model parameters ● 4 sapphire suspensions ● 0. 30 m length ● 30 kg mass LCGT f 2 f meeting@Tokyo university, Japan, 5 th Aug, 2011 Erina Nishida 4

Why fiber is not effective? ? Mechanical lossΦ Physics Letters A 270 (2000) 108 -114 ‘Ribbon’ thickness could be thinner while the heat transportation keep. LCGT f 2 f meeting@Tokyo university, Japan, 5 th Aug, 2011 Erina Nishida 5

Moving 120 Hz peak by changing the fiber shape • Including cooling effect, those peaks doesn’t move to lower. • Without thermal noise increasing, how to make the peak decrease…. is Ribbon, which could make cross section larger, then resonant frequency higher. LCGT f 2 f meeting@Tokyo university, Japan, 5 th Aug, 2011 Erina Nishida 6

Comparison of different ribbon ratio Thinner ribbon make 2 nd mode To 500 Hz!! Ribbon cross section constant Ribbon thickness h, 　width w Cooling effect　above 0. 8 W Thin ribbon can make violin mode move to higher. LCGT f 2 f meeting@Tokyo university, Japan, 5 th Aug, 2011 Erina Nishida 7

Comparison of different cross sections Ribbon thickness constant Ribbon width w Cooling effect　above 0. 8 W 7 times area make 1 st mode to 300 Hz Those parameters are realistic!! Vertical mode and violin mode move to higher according to the thickness. LCGT f 2 f meeting@Tokyo university, Japan, 5 th Aug, 2011 Erina Nishida 8

Alternative solution to reduce vertical TN VSPI for vertical mode l Vertical mode could be suppressed by VSPI. [Vertical Suspension Point Interferometer] Feedback control • Resonant frequency can be changed. • Thermal noise can be reduced. LCGT f 2 f meeting@Tokyo university, Japan, 5 th Aug, 2011 Erina Nishida 9

Options for solutions l To avoid the suspension peak at the 117 Hz →Use ribbon which has wide width and thin thickness l To avoid vertical mode →vertical SPI l Thank you for your attentions!! LCGT f 2 f meeting@Tokyo university, Japan, 5 th Aug, 2011 Erina Nishida 10