After a long journey, halfway across the globe, the tiny 1 mm3 Thorium doped calcium fluoride optically polished cubes have safely arrived in Japan.
There they will have to withstand high fluxes of 29 keV x-rays in the hope of seeing the photonic decay of the isomer state of Thorium-229.
The 5 crystals provide Koji Yoshimura and his team enough oppertunity to see the light, hence the name kagayaku.
Kagayaku means ‘shining’ in Japanese. Which is a description as well as a wish for the future.
Due to the high doping concentration of the radioactive Thorium-229 each crystal has an activity of several kBq.
The alpha, beta and gamma decays in the crystal produce Cherenkov light and Self Trapped Excitons that make the crystal permanently shining.
We hope that these crystals, 400 times better than the last ones, will shine their isomer light!