Optical pneumatic beam detector for intermittent infrared radiation

The detector has two chambers (17,20) surrounded by a housing (1). The chambers can be closed in a gas tight manner and are filled with a radiation absorbent gas. At least one chamber is formed as an absorption chamber and is provided with a radiation transparent window (13). A probe is connected to both chambers. This detects the pressure difference between the two chambers and converts this to a measurement signal. The detector housing (1) has a base element (2) and an insert element (3). The base has a cylindrical stepped bore (4) with a first, larger diameter section (5) and a second smaller diameter section (6) in the beam path. Each section (5,6) is connected via a radial bore (11,12) into a probe chamber (10). The outer end of the second section is closed by a beam reflecting base or a beam transmitting window (13). The insert element is arranged in the first section (5). This divides the bore into the two chambers and has a bore (18) in the beam path. The bore is closed at least on one side by a beam passing window (13) or a beam reflecting base.