Abstract: Apparatus for securing a fragile cylindrical tube within an envelope by using at least two spaced-apart mounting rings which tend to center the tube within the envelope. Each mounting ring is provided with three radially-extending through-holes, and an elastic sphere having a diameter greater than the thickness of the ring placed in each through-hole is in contact with the inner surface of the envelope and the outer surface of the tube, thus centering the tube within the envelope.

Abstract: The invention relates to an instrument for chemi- or bioluminescent analysis of the concentration of a constituent of a sample gas (G.sub.1) which in a reaction chamber (C) reacts with a liquid reagent (R.sub.1) in a luminescent manner. The liquid reagent (R.sub.1) is ejected into the reaction chamber (C) by ejection means. The sample gas (G.sub.1) can be used as propellant in the ejection means (E) sucking the liquid reagent (R.sub.1) into the propellant and as an aerosol be sprayed into the reaction chamber. Carefully mixed with the sample gas, it generates chemiluminescent radiation (L.sub.1, L.sub.2) in the field of view of a photodetector (D). The propellant (G.sub.1) can also be prepared so that either heating or cooling occurs on expansion in the reaction chamber (C). By providing walls of the reaction chamber with reflecting layers, the main portion of the luminescent radiation reaches the detector (D).

Abstract: A gated, pulsed laser spectrofluorometer is provided analyzing subpicogram amounts of fluorescent substance in sample volumes of less than 10 .mu.l. This is accomplished by repetitively exciting the fluorescent sample with a subnanosecond, intensive excitation radiation pulse and by gating a fluorescence radiation detector output signal so that detection starts after the excitation radiation pulse has decayed to a negligible intensity and ends when the fluorescence radiation detector output signal caused by the fluorescence emission from the sample has decayed to a level comparable to the electrical noise level of the electronic measuring apparatus connected to said fluorescence radiation detector.

Abstract: A coaxial high repetition rate pulsed gas laser is provided, having a peak value pulse to pulse reproducibility better than 1% at a repetition rate of up to 400 Hz. This is accomplished by synchronizing the time evolution of the high tension laser electrode voltage with the gas break-down delay period in such a way that the laser output and stability are optimized.