Background: X-ray curved-crystal spectrometer

as one of important diagnostic tool for measuring the plasma temperature and rotation velocity of the tokamak

is usually based on the satellite spectra of some special kind of impurity by single-crystal diffraction

which limits the temperature range to be measured simultaneously. Purpose: This study aims to effectively broaden the temperature range of the spectrometers

an assembly of double-crystal was designed to replace the previous of single-crystal. Methods: The two crystals of the assembly having the similar Bragg angles were installed on the same pedestal

which could make the spectra recorded on the same detector. Consideration and technology route of the double-crystal were described and analyzed together with the experimental tests on the Experimental Advanced Superconducting Tokamak (EAST). Results: Experimental results on the double-crystal X-ray spectrometer showed that the He-like and H-like Ar spectra were obtained for the first time

and the ion Ar temperatures calculated by two kinds of spectra were in good consistence within a certain error range. Conclusion: The application of double-crystal for X-ray curved-crystal spectrometers on EAST proposed in this paper is applicable and feasible. Abstract