Research of Solar Very Small Velocity Fields by Magneto-Optical Filter

磁光滤光器(MOF或Caccianl滤光器)是由放置在强磁场中的透明单元制成的。电池中含有钠等物质的蒸气。通过利用谱线波长附近的磁光效应，MOF提供了一个非常窄和稳定的通带，特别适合于太阳地震观测。我们于1984年开始对这种类型的过滤器进行基础实验研究。在大多数MOF的设计中，只有钠容器是加热的，所以当钠蒸气在那里冷却时，它会附着在墙上。因此，随着年龄的增长，细胞变得不那么透明，只能用于几个月的观察。我们的目标是建造一种可以连续使用10-20年而不会损失细胞壁上的钠蒸气的过滤器。这是通过将整个电池加热到约200ﾟC来实现的。我们开发了引入对高温钠气体稳定的新材料的方法。由于这种发展是每一件事情都需要很长时间的，我们只能完成新的MOF系统的建设，所以太阳速度场的数据获取才刚刚开始。我们描述了发展的过程和实验结果。

The magneto-optical filter (MOF or Caccianl filter) is made of a transparent cell placed in a strong magnetic field. The cell contains the vapor of material like sodium. By utilizing the magneto-optical effect near the wavelength of a spectral line, MOF provides a very narrow and stable passband, which is perticularly suitable for helio-seismological observations. We started basic experimental studies on this type of filters in 1984. In the design of most MOF's, only the sodium reservoir is heated, so that the sodium vapor attaches onto the wall when it cools there. The cell therefore becomes less transparent as it ages, and can only be used in observations for several months. Our aim was to construct a filter that can be continuously used for 10-20 years without losing the sodium vapor at the cell wall. This was achived by heating the whole cell to about 200ﾟC.We developed the method of Introducing the new material that is stable for high temperature sodium gas. As this development was necessary very long term for each affair, we chould finish only the construciton of the new MOF system, and so the data obtainment of solar velocity fields has just started.We descrive the process of the development and experimental results.