GB945438A - Ionization detector - Google Patents

Abstract

945,438. Discharge tubes. BECKMAN INSTRUMENTS Inc. April 28, 1961 [June 27, 1960], No. 15388/61. Heading H1D. [Also in Division G1] In an arrangement for detecting the presence of ionizable substances in a gas, such as the outflow from a chromatograph column, the gas is mixed with a second gas stream during its passage into an ionization chamber electrons which have previously been introduced into the second gas stream acquiring a considerably higher energy level under the influence of the electric field in the chamber, and in consequence effecting ionization of the components of the sample stream. The gas to be tested is admitted to the ionization chamber 24 by a pipe 37, Fig. 2, and the second gas (argon) is fed into the electron generator by a pipe 36. An ultraviolet lamp 25 acting on the metallic inner surface of tube 23, which may be copper, produces photo electrons which diffuse into the ionization chamber 24 with the second gas stream. The second gas, which may be argon, helium, neon, krypton, or Xenon, should have a high ionizing potential so as not itself to become ionized by the high energy electrons. Alternative electron generator metal linings are referred to including metal oxides, and metals like potassium and caesium of low work function responsive to visible light. The use of X-rays is also referred to. The projection of rays through the walls of a glass chamber and the use of a mercury arc lamp, hydrogen lamp, zenon lamp, or a heated filament are also described. Anode 33 is energized from a source 31 and the current after amplification in an amplifier 32 is recorded by a recorder 19. A modified arrangement, Fig. 3, includes an inwardly directed ridge 40 at the junction between the two zones and a baffle plate 41 on the inlet line of the gas under test. Numerous physical arrangements of the chambers including " in line," " L," " T " and concentric arrangements are described with reference to Figs. 4-9 and 11 (not shown), and an arrangement wherein the ionization chamber is included in a bore within a solid block of copper which latter forms the chamber for the electron generator is described with reference to Fig. 10 (not shown). The lamp in this latter arrangement projects substantially radially into the bore.