In search of the best detectors of gravitational waves, scientists are looking for the cold. The upcoming KAGRA detector will look for the ripples of space-time, using clever technological tricks: key components will be cooled to temperatures just above absolute zero, and all sensitive installing will be placed in a giant underground cave. Scientists of the KAGRA project, located in Kamioka, Japan, recently received the results of the first ultracold tests. According to them, the detector is ready to begin searches of gravitational waves at the end of 2019.
KAGRA: Japanese gravitational wave detector
The new detector will join similar observatories in the search for the barely visible cosmic disturbances caused by violent events such as collisions of black holes. Laser interferometric gravitational wave Observatory LIGO supports two detectors situated at Hanford, Washington and Livingston, state of Los Angeles. Another Observatory — Virgo is located near Pisa Italian. These detectors are above ground and do not use cooling methods.
It turns out, KAGRA will be the first of its kind.
KAGRA consists of two 3 km-long sleeves, built in the form of letters, Inside of each sleeve laser beam is reflected between two mirrors located at both ends. The light acts as a giant ruler, fixing a tiny change in the length of each arm, which can be caused by a passing gravitational wave, tensile and compressive space of time.
Since the gravitational wave detectors measure changes of length less than the diameter of a proton, minor effects like the motion of molecules on the surfaces of the mirrors can interfere with the measurements. Mirrors are cooled to approximately 20 Kelvin (-253 Celsius), thus limiting the vibrations of molecules.
In new tests conducted in the spring of 2018, scientists cooled only one of the four mirrors of KAGRA, says project leader Takaaki kajita from Tokyo University. When the detector starts for real, the others will also be chilled.
Detector under the ground also helps prevent the vibration mirror due to activity on the Earth’s surface. LIGO is so sensitive that it can act the rumbling trucks, the wind and even wildlife. Underground lair of KAGRA should be much quieter.
The construction of underground and cooling demanded years of effort. Scientists KAGRA took on these two difficult tasks, which are important for the long-term future of the industry, says David shoemaker, LIGO representative. In the future, even more advanced gravitational wave detectors can be based on the methods of KAGRA.
Currently, the addition of KAGRA to the list of existing observatories should help scientists improve their investigations of sources of gravitational fluctuations. Once scientists find the signal of gravitational waves, they warn astronomers who are looking for the light from the cataclysm that gave rise to these waves, in the hope to better understand the event. The presence of additional gravitational wave detector in another part of the world will help you better triangulate the sources of the waves. As you know, telescopes can see only certain pieces of the sky.
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