JPH0353403Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to a gas phase ion source.

[Prior Art] In a gas-phase ion source, an emitter placed in a gas atmosphere that serves as ion species is cooled with, for example, liquid helium, and a strong electric field is formed at the tip of the emitter. It is ionized.

In order to create such a strong electric field at the tip and accelerate the generated ions, it is necessary to apply a high voltage to the emitter. Therefore, conventionally, an electrode is brought into contact with the emitter from the outside.

On the other hand, in order to supply the gas serving as ion species to the vicinity of the tip of the emitter from the outside, a supply pipe must be provided close to the emitter.

[Problems to be solved by the invention] However, because heat flows in from this electrode, the temperature of the emitter could not be lowered sufficiently even if it was cooled with liquid helium or the like.

In addition, since such electrodes and supply pipes must be placed around the emitter, this poses an obstacle in replacing the emitter.

This invention was made in view of the above points,
It is an object of the present invention to provide a gas phase ion source in which the inflow of heat into the emitter is small and the configuration around the emitter is simplified.

[Means for Solving the Problems] To achieve this object, the present invention includes a tank containing a refrigerant, a base of good electrical conductor attached to the bottom of the tank, and an emitter removably attached to the base. an extraction electrode disposed opposite to the emitter; a channel for supplying ion species gas to the vicinity of the tip of the emitter through the base; and supplying ion species gas to the channel from the outside. A supply pipe is provided, the part of the supply pipe connected to the base is made of a good electrical conductor, the other part is made of an electrical insulator, and the part of the supply pipe made of a good electrical conductor has a thin It is characterized by applying high voltage through the conductor wire.

[Operation] In the present invention, the ion species gas is supplied to the vicinity of the emitter tip through the base. A portion of the gas supply pipe connected to the base is formed of a good electrical conductor, and a high voltage is applied to the portion formed of this good electrical conductor via a thin wire.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

[Embodiment] The accompanying drawing is a schematic diagram showing the configuration of an embodiment of the present invention. In the figure, 1 is the outer wall of the ion source whose interior is kept in a high vacuum, 2 is a tank filled with liquid helium 3, and the thermal It is supported in a state where it is blocked by. A copper base 7 is attached to the bottom of the tank 2 via an electrical insulator 6 with good thermal conductivity such as sapphire, and an emitter 9 is further held in a copper holder 8.
is removably attached to this base 7 with screws 10. 11 is an insulating tube, and 12 is an extraction electrode.

The holder 8 is provided with a gas passage 13, and the ion species gas is supplied to the emitter 9 through the gas passage 14 provided in the base 7 and this gas passage 13.
is supplied to the vicinity of the tip. 15 is a copper gas introduction pipe attached to the base 7, and this pipe 1
5 is connected to an insulating tube 16 for transporting an ion species gas from the outside. 17 is a joint provided at a portion where the insulating tube 16 passes through the outer wall 1.

18 is a high voltage terminal installed through the outer wall 1;
Reference numeral 19 denotes a high voltage terminal attached to the gas introduction pipe 15, and the two are connected by an extremely thin conducting wire 20. 21 is a terminal for applying an extraction voltage to the extraction electrode 12.

In the configuration as described above, the emitter 9 is cooled to a cryogenic temperature by the liquid helium 3 filled in the tank 2. Here, when an ion species gas (for example, helium gas) is introduced from the outside through the tube 16, the helium gas is sent to the vicinity of the tip of the emitter 9 through the passages 14 and 13. The gas flow rate at this time is appropriately set so that the helium pressure around the emitter 9 is, for example, about 10 ^-3 Torr.
In this state, an accelerating voltage of, for example, about +100 KV is applied to the emitter 9 via the terminal 19.
An appropriate extraction voltage is applied between the emitter and the extraction electrode via terminals 18 and 21. A strong electric field formed at the tip of the emitter due to this extraction voltage ionizes the helium present at the tip. The generated helium ions are accelerated by an accelerating electric field formed by an accelerating voltage applied to the emitter, and are given high energy.

By the way, a voltage is applied to the emitter 9 through a thin conducting wire 20 with relatively high electrical resistance, but since the thin conducting wire has a high thermal resistance, the inflow of heat from the outside from the terminal 18 to the terminal 19 is kept to an extremely low level. Is possible. Therefore, it is possible to sufficiently lower the temperature of the emitter 9 using liquid helium.

Furthermore, since the current (ion beam current) flowing through the conducting wire at this time is extremely small, on the order of picoamperes, the voltage drop due to this conducting wire is kept small, and a sufficiently high accelerating voltage can be efficiently applied to the emitter.

Furthermore, in the present invention, the introduction pipe 15 for supplying gas into the base 7 is made of a conductive material, and a high voltage is applied to the emitter 9 through this introduction pipe, so that the structure around the emitter is simplified. Therefore, it is less likely to become a hindrance to the work of replacing the emitter.

[Effects] As described in detail above, according to the present invention, a gas phase ion source is realized in which less heat flows into the emitter and the configuration around the emitter is simplified.

[Brief explanation of drawings]

The accompanying drawings are schematic diagrams showing the configuration of one embodiment of the present invention. 2: Tank, 3: Liquid helium, 6: Electrical insulator, 7: Base, 8: Holder, 9: Emitter, 1
2: Extraction electrode, 13, 14: Gas passage, 15:
Gas introduction pipe, 16: Insulation tube, 18,1
9: High voltage terminal, 20: Conductor.

Claims (1)

[Scope of utility model registration request] a tank containing a refrigerant, a base of good electrical conductivity attached to the bottom of the tank, an emitter removably attached to the base, a lead-out electrode disposed opposite the emitter, and an emitter that passes through the base. is equipped with a channel for supplying gas for ion species near the tip thereof, and a supply pipe for supplying gas for ion species from the outside to the channel, and a portion of the supply pipe connected to the base is electrically connected to the base. A gas phase ion is formed of a good conductor, the other part is made of an electrical insulator, and a high voltage is applied to the part of the supply pipe made of a good electrical conductor via a thin conductor wire. source.