Low pressure mercury vapor filled discharge lamp

Abstract From the Canadian patent

In a fluorescent lamp with amalgam, a surface of the amalgam is covered by a barrier having at least one opening through which mercury atoms can move to a discharge space of the lamp from the amalgam while the lamp is being lighted. When the lamp is switched off, the barrier restricts the return of the mercury atoms from the discharge space to the amalgam. The amalgam solidifies faster than all the mercury atoms return to the amalgam, so that a lot of mercury atoms remain in the discharge space. When the lamp is re-lighted an initial mercury, vapor pressure can be maintained. Thus the lamp illuminates at, a predetermined intensity of the luminance from the beginning of the re-lighting.