Background: The toroidal charge exchange recombination spectroscopy (CXRS) diagnostic was recently deployed on Experimental Advanced Superconducting Tokamak (EAST). The main purpose of this diagnostic system is the profiles of plasma temperature and velocity profiles. The system was calibrated preliminarily by using an integrating sphere lamp whose wavelength and intensity was checked precisely by the manufacturer. As the integrating sphere lamp can only be used before or after the experiment

the real time calibration for the CXRS diagnostic system becomes very important. Purpose: This study aims to use CXRS to measure impurity density

which requires the absolute intensity of the spectrum

so the system must be absolutely calibrated. Methods: The intensity of bremsstrahlung emitted from the plasma during the CXRS experiments was measured. Theoretical computations were performed using relevant parameters of EAST plasma. Results: Compared the measurement results of bremsstrahlung intensity to the theoretical calculation whose parameters were provided by other diagnostic systems

it is shown that errors were in the same order of magnitude and very common in the plasma diagnostic. Conclusion: The experimental results showed that absolute intensity calibration based on the bremsstrahlung is feasible and it gives a possible way for the real time calibration. In the future experiment

the CXRS diagnostic system will adopt this method. Abstract