The recent detections of gravitational waves (GWs) reported by LIGO/Virgo
collaborations have made significant impact on physics and astronomy. A global
network of GW detectors will play a key role to solve the unknown nature of the
sources in coordinated observations with astronomical telescopes and detectors.
Here we introduce KAGRA (former name LCGT; Large-scale Cryogenic Gravitational
wave Telescope), a new GW detector with two 3-km baseline arms arranged in the
shape of an "L", located inside the Mt. Ikenoyama, Kamioka, Gifu, Japan.
KAGRA's design is similar to those of the second generations such as Advanced
LIGO/Virgo, but it will be operating at the cryogenic temperature with sapphire
mirrors. This low temperature feature is advantageous for improving the
sensitivity around 100 Hz and is considered as an important feature for the
third generation GW detector concept (e.g. Einstein Telescope of Europe or
Cosmic Explorer of USA). Hence, KAGRA is often called as a 2.5 generation GW
detector based on laser interferometry. The installation and commissioning of
KAGRA is underway and its cryogenic systems have been successfully tested in
May, 2018. KAGRA's first observation run is scheduled in late 2019, aiming to
join the third observation run (O3) of the advanced LIGO/Virgo network. In this
work, we describe a brief history of KAGRA and highlights of main feature. We
also discuss the prospects of GW observation with KAGRA in the era of O3. When
operating along with the existing GW detectors, KAGRA will be helpful to locate
a GW source more accurately and to determine the source parameters with higher
precision, providing information for follow-up observations of a GW trigger
candidate.