| 摘要 |
<p>A method is described for the automatic determination of the time when barium starts to evaporate, or "start time", of barium evaporable getters. A temperature difference measurement is made of the temperature of the glass wall (105) outside the getter location by means of a sensor (110) preferably comprising an infrared pyrometer calibrated on a wave length of about 10 mu m suitable for measuring temperatures of 0-500 DEG C. Under these conditions the temperature curve measured, through an integral function, follows the behaviour of the temperature of the getter which reveals a typical behaviour at the moment in which barium starts to evaporate. Once DELTA T has been calculated from the analysis of a series of experimental test results on the integral curve, that value corresponds to the start time. The measurement of temperature is transformed into a suitably amplified voltage this giving a value of DELTA V corresponding to the start time. This can then be used to automatically regulate the R.F. generator power level to obtain a constant start time or to regulate the total time of evaporation of the getter so as to obtain a constant barium yield. <IMAGE></p> |
