DES0034482MA - - Google Patents

Description

■: ■; .. , PATENT CLAIMS:

1. Ionization measuring chamber with electrode coatings made of metals with a high atomic number, thereby characterized in that a mixture of colloidally distributed platinum is used as the covering material and silver in a lacquer-like binder

. is used. _; '_;■; /. ':

2. A method for producing an ionization measuring chamber according to claim 1, characterized characterized in that the mixture dissolved in a diluent oil is embedded in lacquer-like binders Platinum and silver colloids by means of a preferably electrostatic Spray device is applied.

3. Large-area ionization measuring chamber according to claim 1 with two spaced parallel to each other arranged electrode plates simultaneously forming the outer wall of the chamber and one arranged between these plates, made of insulating material - preferably made of insulating plastic Plate, the coverings on both sides made of a mixture of platinum and silver colloids embedded in lacquer-like binders has ,, characterized in that the outer plates are made of aluminum.

Referred publications:

German Patent Nos. 849 733, 897 603; Swiss Patent No. 226563; U'SA. Patent Nos. 2479271, 2.596080.

1 sheet of drawings

Claims (1)

S 34482 VIII c / 21g The invention relates to an ionization measuring chamber with electrons exposed to radiation • - · emitting electrodes, in particular a flat ionization chamber for automatic setting of the exposure time for X-ray exposures. As a rule, thin lead coatings are used as electrodes for such chambers, which are placed on a suitable Carriers, e.g., insulating plastic sheets, are vapor-deposited. These lead coatings often show ίο severe signs of corrosion after a short time, which are mainly due to the formation of hydroxides. According to the invention, a corrosion-resistant electrode coating with good electron yield for ionization measuring chambers can be achieved by using a mixture of platinum and silver colloids embedded in paint-like binders as the coating material. The use of noble metal colloids in paint-like binders for producing electrically conductive surfaces on electrically non-conductive substrates is known per se ... The coating material according to the invention has good electrical conductivity, even when applied in a thin layer, and a layer with an electron yield approximately corresponding to a lead coating is obtained if the platinum-silver ratio _3: 7 is selected; By increasing the platinum content results in a significant increase but not the electron yield. The order of the lacquer-like. Mixture of platinum and silver colloids embedded in binders is expediently carried out by a preferred wise electrostatic spray device, for which the mixture is mixed with a suitable diluent oil will. With the help of a template placed at a distance of a few millimeters from the carrier is arranged, electrode fields with well-running edges can be created in this way produce. Ionization measuring chambers are known whose electrode coatings contain graphite colloids. These electrode coatings only give off a relatively small number of electrons when exposed to radiation. Electrode coatings made of metals, which, due to their high atomic number, give off many electrons when exposed to radiation, are usually not corrosion-resistant. Only pure platinum coatings are corrosion-resistant and, moreover, have a sufficient yield of electrons, but they cannot be considered due to the high price of platinum. A vapor deposition of platinum on plastic layers serving as electrode carriers is not possible, since the known plastic layers are not sufficiently temperature-resistant: The mixture of platinum and silver colloids according to the invention is 'relatively cheap, can be' easily.on plastic = - '■'< Apply layers, emits a large number of electrons when exposed to radiation and is corrosion-resistant. In the case of ionization measuring chambers with two outer walls arranged parallel to one another at the same time and plates forming external electrodes and one arranged between these plates, the The plate forming the inner electrode has proven to be sufficient with regard to the electron yield to cover the inner electrode on both sides with the mixture of platinum and silver colloids according to the invention, if the outer electrodes consist of aluminum. 1 and 2 is a flat comb according to the invention iri the broad side and in the narrow side shown in section, ;; '/ In a wooden frame 1, an insulating plastic plate 2 is arranged, both sides of which are covered with electrodes 3 and 4 made of the platinum-silver-celloid mixture according to the invention. When The aluminum plates 5 and 6 serve the outer electrodes and outer walls of the chamber Mounting of the aluminum plates 5 and 6, a rail 7 encompassing the wooden frame 1 is provided, to which a power supply socket 8 (not shown in detail because it is known) is attached.