Coating development and plans for filter cavity tests at TAMA

Coating development and plans for filter

cavity tests at TAMA

Daisuke TATSUMINational Astronomical Observatory of Japan

2014/08/02 KAGRA f2f 　 August 2014 @ Toyama Univ. 1

2014/08/02 KAGRA f2f 　 August 2014 @ Toyama Univ. 2

Filter cavity

2014/08/02 KAGRA f2f 　 August 2014 @ Toyama Univ. 3

Squeezing Light and Filter cavity

Squeezed vacuum injection is one of promising way to reduce the detector noises.

As a R&D activity for beyond the KAGRA detector, we have a plan to develop the filter cavity at TAMA.

2014/08/02 KAGRA f2f 　 August 2014 @ Toyama Univ. 4

A demonstration by eLIGO

2dB

2014/08/02 KAGRA f2f 　 August 2014 @ Toyama Univ. 5

Frequency independent squeezing

2014/08/02 KAGRA f2f 　 August 2014 @ Toyama Univ. 6

Solution: Filter Cavity

2014/08/02 KAGRA f2f 　 August 2014 @ Toyama Univ. 7

Frequency dependent squeezing

2014/08/02 KAGRA f2f 　 August 2014 @ Toyama Univ. 8

Loss requirement (2)

2014/08/02 KAGRA f2f 　 August 2014 @ Toyama Univ. 9

Loss requirements

2014/08/02 KAGRA f2f 　 August 2014 @ Toyama Univ. 10

Rough design of the filter cavity

Cavity pole freq. = 40Hz

Roundtrip Loss < 1ppm/m

Cavity length 10m 300m

Finesse 4E+5 4E+4Mirror reflectance 5N=99.999% 4N=99.99%

Cavity Loss 10ppm 300ppm

2014/08/02 KAGRA f2f 　 August 2014 @ Toyama Univ. 11

Coating developments

2014/08/02 KAGRA f2f 　 August 2014 @ Toyama Univ. 12

Low loss mirror developments

NAOJ and UEC

(Univ. of Electro-Communications)

collaborate with Japanese coating companies

for low-loss mirror coating

developments.

Cross section of the multi-layered coating

Pictures are taken by TEM microscopein Univ. of Tokyo

The films have clear edges.Each layer is dense and uniform.

X-ray Photoelectron Spectroscopy ： XPS

Argon ion gun

Neutralizer

Soft X-ray

Soft X-ray

O K

LL

O 1

s

Ta 4

d5

O 2

s

Ta2O5 film

X-ray Photoelectron Spectroscopy ： XPS

measured by A. Ueda at Institute of Engineering Innovations,

University of Tokyo

Ave. 　 8.0ppm

Scattering Loss

coated by SigmaKoki

world top class quality!

At least the best performance in Japan

446 J/cm2 with 10nsec pulse

44.6 GW/cm2 (peak power density)

This is tolerance for one shot pulse.

KAGRA IOO requireshigh power density (> 1 MW/cm2) tolerance for 10 year continuous operation.

Damage Threshold

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SUMMARY

Recent few years we develop

low-loss mirror

with Japanese companies.

By using the mirror

the filter cavity tests at TAMA

are planned.

End