Looking for the best gravitational wave detectors,scientists are looking for a cold. The coming KAGRA detector will search for space-time ripples using sophisticated technological tricks: the key components will be cooled to temperatures just above absolute zero, and the entire super-sensitive installation will be located in a giant underground cave. Scientists at the KAGRA project, located in Kamioka, Japan, recently received the results of the first ultracold tests. According to them, the detector will be ready for the start of the search for gravitational waves at the end of 2019.
KAGRA: Japanese gravity wave detector
New detector will join similarobservatories in the search for subtle cosmic disturbances caused by turbulent events - for example, collisions of black holes. The LIGO laser interferometric gravitational-wave observatory supports the work of two detectors located in Hanford, WA, and Livingstone, Los Angeles. Another observatory - Virgo - is located next to the Italian Pisa. These detectors are above ground and do not use cooling methods.
It turns out that KAGRA will be the first of its kind.
KAGRA is made up of two 3-kilometer sleeves,lined up in the shape of a letter. Inside each sleeve, a laser beam is reflected between two mirrors located at both ends. Light acts as a giant ruler, capturing tiny changes in the length of each arm, which can be caused by a passing gravity wave, stretching and compressing space time.
Since gravitational wave detectors measurechanges in length less than in the diameter of the proton, minor effects like the movement of molecules on the surfaces of the mirrors can interfere with measurements. The mirrors are cooled to about 20 kelvins (-253 centigrade), thereby limiting molecular vibrations.
In the new tests conducted in the spring of 2018,scientists have cooled only one of the four KAGRA mirrors, says project manager Takaaki Kadzita of Tokyo University. When the detector starts up for real, the rest will also be cooled.
Having a detector underground also helpsprevent mirror vibration due to activity on the surface of the earth. LIGO is so sensitive that it can be affected by thundering trucks, strong winds or even wildlife. The underground lair of KAGRA should be much quieter.
Underground construction and cooling requiredyears of effort. KAGRA scientists have taken on these two challenging tasks that are important for the long-term future of the industry, says David Schoumaker, a spokesman for LIGO. In the future, even more advanced gravity wave detectors may be based on KAGRA methods.
Currently adding KAGRA to the listexisting observatories should help scientists improve their research sources of gravitational oscillations. As soon as scientists discover the signal of a gravitational wave, they warn astronomers who are looking for light from the cataclysm that gave rise to these waves, hoping to better understand the event. The presence of an additional gravitational wave detector in another part of the world will help to better triangulate the wave sources. As you know, telescopes can only observe certain patches of sky.
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