Ring Magnet Enhanced Radio Frequency Glow Discharge Mass Spectrometry Theory And Method Research

Glow discharge mass spectrometry（GD-MS）has become an important characterization and research tool in the development and production of new materials because of its advantages of direct analysis of trace/ultra-trace elements in solid materials.It is widely used in the fields of information and communication,semiconductor,and environment.When GD-MS is equipped with a rf source,glow discharge mass spectrometry can directly analyze non-conductor materials.However,related studies have shown that when using rf-GD-MS to analyze artificial crystalline materials,the conductivity and thermal conductivity of the materials are poor,and the rf power effect will be attenuated,resulting in weaker glow discharge sputtering,causing problems such as lower ion signal intensity and lower analytical sensitivity,which in turn restrict the development and wide application of rf-GD-MS.This study focuses on the above key issues,based on the group’s previous work,we firstly investigated the mechanism of magnetic field-enhanced glow discharge ionization using theoretical methods,and then developed a simple and efficient rf-GD-MS ring magnet enhancement technique based on the theoretical research results to realize the efficient characterization of GGAG,LYSO,Lu AG and other scintillation crystal materials,and obtained significantly enhanced ion signal intensity,the main research contents are as follows:（1）The enhancement mechanism of ring magnet enhanced rf-GD-MS was investigated.The COMSOL Multiphysics software was used to simulate and study the distribution and intensity of magnetic susceptibility lines,electron motion trajectories,electron flux variations,etc.The results showed that when the magnet enhancement device was used,under the combined effect of electric and magnetic fields,the electrons could perform Larmor progression on the sample surface,and the electron flux in the discharge cell was enhanced 10⁷ times compared with that without the magnet.It is presumed that after the ring magnet enhancement device was used,the electron trajectory was prolonged and the motion was more violent,which increased the chance of collision with the particles such as atoms to be analyzed,thus improving the ionization efficiency.（2）The rf-GD-MS ring magnet enhancement device was constructed based on theoretical research and optimized through actual experiments.Firstly,the magnet enhancement device configuration was designed and optimized,and a ring magnet device with the dimensions of D30×d20×5 mm was finally selected by exploring the effects of magnet magnetic induction strength,magnet-sample relative position and magnet polar orientation on the ion signal enhancement;Secondly,the effects of rf power and discharge pressure on the ion signal intensity were investigated.The results showed that the signal intensity enhanced as the rf power increased from 25 W to 70 W.When the discharge pressure increased from 2.2 m Pa to 8.4 m Pa,the signal intensity first enhanced and then decreased,reaching a peak at 4.8 m Pa.It was speculated that when the discharge air pressure was too high,argon particles and electrons had many collisions before they collided with the sample,losing energy and reducing the possibility of sample ionization.Combining with the actual situation,the optimized discharge conditions were 40 W of rf power and 4.8 m Pa of discharge pressure.Under this condition,the measured signal intensity of ²⁰⁹Bi in the BGO crystal was 27600times higher than that in the absence of magnetic field.（3）Verification and application of rf-GD-MS ring magnet enhancement method.Two glass specimens of NIST SRM 1831 and NIST SRM 620 were utilized to verify and calculate the accuracy and detection limits of the ring magnet enhanced rf-GD-MS.The experimental results indicated that the relative error of the method was less than 13%and the minimum detection limit could be as low as 0.0023μg/g.Finally,ring magnet enhanced rf-GD-MS was applied to detect GGAG,LYSO and Lu AG crystals.The results suggested that the method had good signal enhancement for both matrix elements and trace elements.