Abstract: An improved plasma torch for the high-frequency capacitive generation of a plasma beam, a special nozzle construction providing a large-length, small-diameter plasma beam. The nozzle includes a first channel for cooling an internal plasma-generating electrode and a second channel for converging the plasma beam.

Abstract: An inductive heating apparatus includes two or more inductors (2, 3) connected to a single high-frequency generator (1). With such a heating apparatus, for example, the two supports (9, 10) in a cathode ray tube can be heated simultaneously. In order to have the heating of each support proceed properly, the heating operations of the individual supports (9, 10) should be effected independently. Independent interruption of the electromagnetic power transfer from the inductors (2, 3) to the supports (9, 10) is preferably effected by axially moving away from the workpiece (4) a coil core (6, 8) inside the associated induction coil (5, 7). This is advantageous in that the case of low-ohmic inductors no large currents and in the case of high-ohmic inductors no large voltages need to be switched. In addition, the induction coils, which in the case of low-ohmic inductors (2, 3) often consist of an internally cooled tubular conductor, can then be rigidly mounted.

Abstract: In a getter arrangement for providing a getter spot on the walll of an evacuated space, for example an electron tube, the power transfer can be of too short or too long a duration (for example because of positional inaccuracies of the holder containing the getter material or inaccuracies in the shape or composition of the wall). In the first case the intended quality of the getter process is not obtained, in the second case the electron tube may get damaged. A control unit measures the duration of the time interval which starts at the beginning of the power transfer and ends at the instant the getter spot is created. This instant is determined by a detector which detects the getter spot. After this instant the control unit continues the power transfer during a further time interval whose length depends on the first time interval. Consequently, the duration of the transfer depends on the behaviour of the gettering process, which improves the quality of the gettering process and prevents damage to the tube.

Abstract: Solid glass preforms are made by externally heating a tubular preform by a plasma which is reciprocated along the hollow tube. The plasma gas consists entirely or partly of a molecular gas (N.sub.2 or O.sub.2, for example). The hollow preform is preferably rotated during collapsing.

Abstract: An alternately heatable and coolable moulding block for manufacturing plate-shaped information carriers from thermoplastic material, which block is composed of a plate of an electrically insulating material which has a thin metal mould containing the information and in which plate a duct for a cooling liquid is provided and of an electrical conductor wound to form a flat induction coil. Between the mould and the insulating plate, there are provided a layer of a material of good thermal conductivity, which layer is in contact with the mould, and a layer of a ferromagnetic material.