JP2876248B2 - Ion source - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ion source that generates ions by arc discharge.

[Prior Art] Conventionally, an ion source shown in FIG. 2 has been known. The ion source includes two cathodes 100 arranged at a predetermined interval, and an anode 103 arranged to form two arc discharge units 101 and an ion generation unit 102 therebetween.

A gas supply port 104 is formed in a portion of the anode 103 which is a partition wall of the arc discharge unit 101. A gas such as argon is supplied to the arc discharge unit 101 from these gas supply ports 104 by a gas supply device. An arc voltage is applied to the cathode 100 and the anode 103 by a voltage application device. An ion extraction port 105 for extracting an ion beam is formed in a portion of the anode 103 which is a partition wall of the ion generation unit 102.

In this ion source, when a gas is supplied from a gas supply port 104 to the arc discharge unit 101, the gas is ionized by electrons emitted from the cathode 100, and the arc discharge unit 10
At the same time as the occurrence of arc discharge in 1, the gas is extended to the ion generation unit 102 and the gas of the ion generation unit 102 becomes plasma, multiply-charged ions are generated, and the ion beam is extracted from the ion extraction port 105 in the direction of arrow m.

[Problems to be Solved by the Invention] In the case of an ion beam incident on an accelerator or the like, in order to extract a beam with a large energy from the accelerator or the like, it is desirable that the ions be polyvalent. It has been found that in the above-mentioned ion source, in order to increase the proportion of polyvalent ions, the amount of gas should be reduced.

However, the generation rate of multiply-charged ions is higher when the amount of gas in the ion generation section is smaller, but when the amount of gas is small, discharge is difficult to occur, or even if discharge occurs, it is unstable, and the plasma is maintained. hard.

For this purpose, by the gas supply device, for example, a valve is opened and closed in a pulsed manner, a gas is supplied to the discharge unit 101 so that the gas flow rate changes in a pulsed manner, and a discharge voltage is applied at the maximum gas flow rate. An arc discharge is caused to ionize the gas. Since the pulsed gas exponentially decreases after the start of discharge, the multiply-charged ions among the generated ions are
It increases as the gas decreases, but it is difficult to control the amount of gas.

Therefore, in the conventional ion source, the control of the amount of gas is unstable, and the valve of the gas supply device needs to be repeatedly opened and closed continuously, so that there is a problem that there are many valve replacements and maintenance operations. is there.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ion source in which the control of the gas amount is stable, a large amount of multiply-charged ions can be obtained, and the valve replacement and maintenance work of the gas supply device are extremely small. .

[Means for Solving the Problems] According to the present invention, a discharge section formed between a cathode and an anode and supplied with a gas, and an ion communicating with the discharge section to generate multivalent ions An ion source having an ion generator, wherein the ion generated by the ion generator is extracted from an ion extraction port provided on a partition wall facing the electrode for extracting ions. And a throttle means provided with a flow rate variable mechanism for adjusting the flow rate of the gas from the discharge section to the ion generation section while causing a difference in the amounts of these gases between the discharge section and the discharge section. An ion source characterized in that the amount of gas in the ion generating section is further reduced.

[Operation] In the present invention, the gas in the discharge section is supplied to the discharge section by supplying the gas at a constant flow rate, adjusting the flow rate of the gas in the discharge section by the throttle mechanism, and sending the gas to the ion generation section. The amount of gas in the ion generation section is reduced.

Example Next, an example in which the present invention is applied to a hot cathode type will be described in detail with reference to the drawings.

In FIG. 1, reference numerals 1 and 1 indicate cathodes. These cathodes 1 are arranged so as to face each other at a predetermined interval. The cathode 1 is maintained at a predetermined temperature by a heating device (not shown) provided in one or both of the cathodes 1.

Between these cathodes 1, a cylindrical anode 2 is arranged. The anode 2 forms a discharge section 3 between the anode 2 and the cathode 1, and forms an ion generation section 4 at the center. That is, the anode 2
It also serves as a partition wall for the discharge unit 3 and the ion generation unit 4. A voltage applying device (not shown) is applied to the cathode 1 and the anode 2
Thereby applying an arc discharge voltage.

A gas supply port 5 is formed in each of the anodes 2 serving as partition walls of the discharge unit 3. A gas such as argon is supplied to the discharge unit 3 from the gas supply ports 5 by a gas supply device (not shown). This gas supply device
The gas is supplied to the discharge unit 3 so that the flow rate is constant.

A throttle mechanism 6 is provided between the discharge unit 3 and the ion generation unit 4. The throttle mechanism 6 is provided with a member for preventing gas flow in a gas passage. The throttle mechanism 6 causes a difference between the amount of gas in the discharge unit 3 and the amount of gas in the ion generation unit 4, so that the amount of gas in the discharge unit 3 is maintained as required for arc discharge.

In the part of the anode 2 which is a partition wall of the ion generation part 4,
An ion outlet 7 is formed. An electrode (not shown) for extracting ions is arranged to face the ion extraction port 7. An ion beam generated by the ion generator 4 is extracted from the ion extraction port 7 in the direction of arrow a.

A gas amount adjusting hole 8 is formed in a portion of the partition wall of the ion generation unit 4 other than the ion extraction port 7. The gas amount adjusting holes 8 allow the gas of the ion generating section 4 to escape to the outside and adjust the gas amount of the ion generating section 4 to a range where multivalent ions are easily generated.

When a gas having a constant flow rate is supplied from the gas supply port 5 to the discharge unit 3, electrons are emitted from the cathode 1 by the arc discharge voltage applied between the cathode 1 and the anode 2, and the discharge unit 3 At the same time as the gas is ionized and an arc discharge occurs, the gas is extended to the ion generating section 4 to be in a plasma state.

The electrons emitted from the cathode 1 lose energy by colliding with the gas in the discharge part 3. The electrons that have lost energy do not contribute to the production of multiply charged ions. The electrons having high energy pass through the discharge unit 3 and pass through the ion generation unit 4.
Collides with gas to generate multiply charged ions. Since the amount of gas in the ion generation unit 4 is smaller than the amount of gas in the discharge unit 3, in the ion generation unit 4, recombination of electrons and multivalent ions is unlikely to occur. The proportion of multiply charged ions increases, and a large amount of multiply charged ions are extracted from the ion extraction port 7 by ion beam.

The degree of flow rate adjustment in the throttle mechanism 6 and the size of the gas amount adjusting hole 8 are determined depending on the type of gas. Further, the throttle mechanism 6 may be constituted by a variable flow rate mechanism capable of changing the size of the gas passage.
You may comprise so that it can be replaced. The present invention can also be applied to a cold cathode type.

[Effects of the Invention] According to the present invention, the amount of gas in the discharge unit and the ion generation unit is controlled by the throttle means provided between the discharge unit and the ion generation unit. A large amount of multiply-charged ions can be obtained stably, and the gas supply device only needs to supply gas to the discharge unit so that the flow rate is constant. Few.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an embodiment of the present invention, and FIG.
FIG. 1 is a sectional view schematically showing a conventional ion source. DESCRIPTION OF SYMBOLS 1 ... Cathode, 2 ... Anode, 3 ... Discharge part, 4 ... Ion generation part, 5 ... Gas supply port, 6 ... Throttle mechanism, 7 ... Ion extraction port, 8 ... Gas amount adjustment hole.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-10432 (JP, A) JP-A-61-134659 (JP, A) JP-A-61-121248 (JP, A) 152555 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01J 27/00-27/26 H01J 37/08

Claims (1)

(57) [Claims] A discharge section formed between a cathode and an anode and supplied with a gas; and an ion generation section communicating with the discharge section to generate multivalent ions. And an ion source configured to extract ions including the multiply-charged ions generated by the ion generation unit from an ion extraction port provided in a partition wall facing an ion extraction electrode, wherein the discharge unit and the ion generation unit And a throttle means provided with a flow rate variable mechanism for adjusting the flow rate of the gas from the discharge section to the ion generation section, while providing a difference in the amounts of these gases between the discharge section and the discharge section. An ion source characterized in that the amount of gas in the ion generator is smaller than the amount of gas.