When X-ray fluorescence(XRF)is used in analyzing the element composition of the sample in air atmosphere,the strong absorption from the air to the low-energy characteristic X-rays from such low atomic number(Z)elements as Cl,K,Ca,and so on,deeply affect the analysis for them.To avoid the strong absorption from the air to the characteristic X-ray of low Z elements,the XRF technology in a vacuum atmosphere is often used,but it requires a complicated and expensive vacuum system.Besides,the power of the laboratory source is generally low.This results in a low intensity of incident X-rays,which also affects the analysis of the element composition of the sample with XRF.To solve the above problems,a simple closed XRF analysis system in a helium atmosphere based on a monolithic polycapillary X-ray lens(PCXRL)and rotating target X-ray source was designed.Strong XRF signals were obtained by using X-rays with a high gain of power in density focused by the PCXRL to irradiate the sample,and the excitation channel and the detection channel were both in a stable helium atmosphere to reduce the absorption from the air to the characteristic X-rays of low Z elements.The designed XRF system was characterized to show that with a rotating molybdenum target working at a voltage of 29 kV and a current of 20 mA,the detected XRF intensity of Cl,K,Ca,and Fe in a helium atmosphere is higher than that in an air atmosphere,respectively.For elements with an energy of the characteristic XRF below 8 keV in plants,the characteristic XRF intensity detected in the helium atmosphere is 1.1 to 5.5 times that in the air.This is helpful for an efficient and non-destructive XRF analysis of the elements with low Z of samples.
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