In this paper the structure and the operating principle of a lowpower ultra-soft X-ray source are described and the measurement results of the source are shown. The choice of the operating voltage is discussed. Eight targets made of different material are mounted on a carrying wheel which may be turned and are bombarded in turn by the electrons with high-velocity

and so the characteristic line spectra of eight kinds of elements are obtained. By using this X-ray source we have obtained the K

characteristic line spectra of aluminum(8.34Å)

carbon (44.7Å)and boron(67.6Å). The performances of this X-ray source are as follows: (1)The operating wavelength region-10-67 a. (2)The target power: 12 mW. (3)The target voltage: 500-4000V. (4)The radiation intensity of this source is variable in the range of 10-10

6

photons/second/steradian. The electron(primary)excitation mode is adopted in this source. It doesn't require any cooling because of the low power(12mW).