The microwave cavity perturbation method is widely used for material parameter measurements in connection with small homogeneous samples. Its applicability to larger and inhomogeneous samples is uncertain, but highly desirable in connection with the in-situ condition monitoring of chemical reactors. We have investigated the problem of the reconstruction of axially inhomogeneous permittivity distributions in tubular reactors from measured cavity resonance frequencies of the reactor. It is shown that the use of a-priori knowledge about the function class of the permittivity distribution, which in turn follows from assumptions about the chemical process inside the reactor, allows one to reconstruct the permittivity distribution based on a few resonances only. The resulting errors in the function parameters or in the permittivity values identified are on the order of 5 %, as demonstrated by analytical and numerical calculations, by numerical experiments, and by laboratory experiments.

中文翻译：

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通过腔微扰原位测量反应器中的介电常数分布

微波腔微扰法广泛用于与小均匀样品相关的材料参数测量。它对较大和不均匀样品的适用性尚不确定，但与化学反应器的原位状态监测相关联是非常理想的。我们已经研究了从测量的反应器腔共振频率重建管式反应器中轴向非均匀介电常数分布的问题。结果表明，使用关于介电常数分布函数类的先验知识，这反过来又来自对反应器内部化学过程的假设，允许人们仅基于少数共振重建介电常数分布。