The synchrotron radiation spectra of spherical grating monochromator (SGM) working in soft X-ray and VUV region are often contaminated by significant amount of higher order harmonics

They cannot be suppressed completely by suitable filters. Higher order contributions in the spectral radiation standard and metrology beamline were researched using transmission grating (made in house) and IRD AXUV100G (USA) photodiode detector. The exit beam was dispersed with the transmission grating behind exit slit of the monochromator

and the contributions of the different orders were analyzed. The higher order distributions were quantitatively determined for three gratings in line densities of 1800

600 and 200 l/mm. It is shown that in wavelength between 5~15 nm the contributions of the higher orders to the detector signal are restricted to less than 7% even without filters; In wavelength region between 5 nm and 34 nm the contributions of the higher orders to the detector signal are less than 14% with proper Al

Si

3

N

4

and Zr filters; after modified by quantum efficiency of the detector

the higher order contributions are restricted to less than 6.5%. The research also shows that higher orders are almost totally suppressed by MgF

2

filter when the wavelength between 115~140 nm.