JPS5960844A - Ion source device - Google Patents

Abstract

PURPOSE:To make the size of the thermal cathode smaller while securing the required thermal cathode area on the side of the main discharge room by providing roughness on the surface on the main discharge side of the thermal cathode. CONSTITUTION:The surface on the side of the main discharge room 4 of the thermal cathode 5 is provided with roughness. When the representative length indicating the degree of said roughness is sufficiently larger than the Debye length to be decided by the electrons, the temperature and the density in the plasma generated inside the main discharge room 4, the effective area increases due to the roughness provided on the surface of the thermal cathode 5. Thereby, the size of the thermal cathode 5 can be reduced without changing the thermal cathode area on the side of the main discharge room 4 so as to reduce all power to heat the structure holding it, the auxiliary discharge room 8 and the thermal cathode emitting radiation heat entering the auxiliary discharge room.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an ion source device that generates plasma by gas discharge, extracts and accelerates the plasma and ions.

[Prior art and its problems]

Conventional ion source devices directly extract ions from a heated filament as a cathode, and therefore have a short lifespan and require maintenance. In order to solve this problem, the present inventor invented a system consisting of a main discharge chamber that generates plasma for extracting the ion beam, and a sub-discharge chamber separated from the main discharge chamber. All or part of the partition wall serves as a hot cathode of the main discharge chamber, and an ion having an auxiliary electrode provided in the sub-discharge chamber to heat the hot cathode by discharge or electron impact. In the source, the structure supporting the hot cathode is larger than the structure supporting the tungsten filament that has been conventionally used as the hot cathode of the ion source, making it uneconomical and making the entire ion source device larger. Become larger. Furthermore, if the sub-discharge chamber is attached to the ion source, at least that area cannot be covered with a cusp magnetic field, increasing the loss of ions in the plasma. It should be made as compact as possible. Furthermore, the ratio of the area on the sub-discharge chamber side to the total surface area of the heat shielding cathode body is preferably made as small as possible in order to reduce radiant heat entering the sub-discharge chamber.

[Purpose of the invention]

The present invention improves the drawbacks of the conventional device described above, and aims to further reduce the size of the hot cathode while securing the required area of the hot cathode on the main discharge chamber side.

[Summary of the invention]

In the ion source device of the present invention, by providing unevenness on the main discharge side surface of the hot cathode, the thermionic emission area is increased compared to a case without unevenness.

〔Effect of the invention〕

According to the present invention, the size of the hot cathode body can be reduced without changing the area of the hot cathode on the main discharge chamber side, so that the structure that supports it, the sub-discharge chamber, and the radiant heat cathode that enters the sub-discharge chamber are heated. All the power required for this can be reduced.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG. The main discharge chamber 4 of the ion source consists of a discharge anode wall 1, a grid electrode 3 for extracting the ion beam, and a sub-discharge chamber partition wall containing a hot cathode 5. A permanent magnet 2 is installed on the discharge anode wall to improve plasma confinement.
may be installed.

The sub-discharge chamber 8 consists of a partition including a hot cathode 5, an auxiliary electrode 6, and a tungsten filament 7, and is filled with vacuum or low-pressure gas. The surface of the hot cathode 5 on the main discharge chamber 4 side is uneven. If the typical length representing the degree of this unevenness is sufficiently larger than the Debye length, which is determined by the temperature and density of electrons in the plasma generated in the main discharge chamber, the effective area of the unevenness on the hot cathode surface can be increase First, the auxiliary electrode 6 is heated to its predetermined temperature by electrons emitted from the heated tungsten filament 7. Next, the hot cathode 5 is heated by electron impact by applying a voltage of alternating current, direct current, or a superimposed countercurrent and direct current using the heating power source 101 between the hot cathode 5 and the auxiliary electrode 6.
When the temperature of the tungsten filament 7 and the auxiliary electrode 6 can be maintained at a predetermined value, the power supply between the tungsten filament 7 and the auxiliary electrode 6 is disconnected. Ionizes the gas and creates an arc discharge.

[Other embodiments of the invention]

In FIG. 1, the hot cathode 5 and the auxiliary electrode 6 may have any abrasive material, shape, and structure as long as the requirements are met. Also, there may be one or more sub-discharge chambers,
The installation location is also arbitrary.

Furthermore, the uneven shape formed on the hot cathode is also arbitrary.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the device of the present invention. 1...discharge anode wall, 2...Permanent magnet, 3... Extraction electrode, 4... Main discharge chamber, 5...Heat, negative pole, 6... Auxiliary electrode, 7...Tungsten filament, 8... Sub-discharge chamber, 9... Insulation material, 10...Heating power supply.

Claims (1)

[Claims] It consists of a main discharge chamber that generates plasma from which the ion beam is extracted, and a sub-discharge chamber that is partitioned from the main discharge chamber, and a part or all of the partition wall between the main discharge chamber and the sub-discharge chamber serves as the main discharge chamber. In an ion source that has an auxiliary electrode that serves as a lumpy hot cathode and is located in the sub-discharge chamber and is provided to heat the hot cathode by electric discharge or electron impact, the main discharge side surface of the hot cathode is An ion source device characterized by having unevenness.