Abstract
A viable technique for the preparation of highly thermal conductive joints between sapphire components in gravitational wave detectors is presented. The mechanical loss of such a joint was determined to be as low as 2 × 10−3 at 20 K and 2 × 10−2 at 300 K. The thermal noise performance of a typical joint is compared to the requirements of the Japanese gravitational wave detector, KAGRA. It is shown that using such an indium joint in the suspension system allows it to operate with low thermal noise. Additionally, results on the maximum amount of heat which can be extracted via indium joints are presented. It is found that sapphire parts, joined by means of indium, are able to remove the residual heat load in the mirrors of KAGRA.
Highlights
The detection of gravitational waves is one of the most challenging tasks in astrophysics today
Like Advanced LIGO [2] and Advanced Virgo [10], use quasi-monolithic suspensions based on fused silica elements joined by welding [11,12,13] and hydroxide catalysis bonding [14] to reduce suspension thermal noise which limits the sensitivity in the low frequency band
Besides low mechanical loss—and low thermal noise—the indium joint needs to fulfil a second task: it needs to be able to extract the residual heat in the mirror which originates from optical absorption
Summary
The detection of gravitational waves is one of the most challenging tasks in astrophysics today. In order to construct a quasi-monolithic suspension from crystalline materials it is necessary to develop a fabrication technique for the fibres, a suitable jointing technique for the components, as well as to check if the techniques being used are compliant with the thermal noise and the heat removal requirements. It was shown [45,46,47,48] that hydroxide catalysis bonding—developed initially for the Gravity Probe B mission [49] and successfully applied. A measurement is presented which confirms the capability of this jointing technique to produce highly thermal conductive components which are able to handle the heat load from residual optical absorption of the test masses in KAGRA
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