Detection system based on monochromator for visible bremsstrahlung measurements of HT-6M tokamak

A detection system based on a monochromator for visible bremsstrahlung measurements is constructed. A new line-free spectral portion and stray light level, which affect the Zeff measurements considerably, are carefully investigated under different discharge conditions. The results show that the contribution of line emissions to the continuum for this system does not exceed 10%. It can be further reduced to 3% if an interference filter with a full width at half-maximum of 500 إ is applied.