| 摘要 |
An apparatus 300 for the measurement of the magnetic susceptibility of a gas mixture comprises a gas sample chamber adapted to receive the gas mixture, and a test body 301, 302, with mirror 303, rotatably suspended within the chamber; means for creating an inhomogeneous magnetic field within the chamber; means for detecting rotational motion of the test body comprising a compact optical system including a light source 304 and at least two photodetectors 308, 309 arranged on either side of the source to detect a light signal indicative of the rotational motion; and an actuation system arranged to keep the test body substantially at a null position determined by said optical system. The divergent beam 330 from the source reflects from mirror 303 on the test body onto both detectors and allows for a more compact optical detection system. |
