"阶式碰撞取样器" can be translated as "stepped cascade impactor sampler" or simply "stepped impactor sampler" in English, depending on the specific context and level of detail required.
"Stepped" refers to the staged or sequential nature of the device.
"Cascade impactor" is a common term in aerosol science for a type of instrument that uses a series of stages to separate particles by size through inertial impaction.
"Sampler" indicates its function of collecting samples.
In some cases, if the emphasis is more on the sampling aspect and less on the detailed cascade structure, "stepped impactor sampler" might be sufficient. However, if the specific cascade design is crucial to the understanding, "stepped cascade impactor sampler" would be more accurate.