# US 5,352,954 A · Plasma generator and associated ionization method

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- Number: US 5,352,954 A
- Document ID: US5352954A
- Status: Granted
- Kind: A
- Application number: 08/027,403
- Filed: 1993-03-08
- Granted: 1994-10-04
- Earliest claimed: 1992-03-11
- Assignees: Proel Technologie S.p.A.
- Inventors: Gianfranco Cirri
- Web page: https://patentgrep.com/patent/US5352954A

## CPC

- H01J 27/08: using arc discharge
- H05H 1/54: Plasma accelerators
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)
- H05H: PLASMA TECHNIQUE (apparatus or processes specially adapted for producing X-rays H05G2/00); PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS

## Abstract

In the discharge chamber (21) of a device for generating plasma, used in the space sector for ion propulsion or for the discharging of satellites and in applications on the ground, suitable ionizing radiation sources (47) are provided, capable of improving the performance of said device. The radiation emitted by the sources creates constant ionization of the gas with advantages both during the preionization phase, i.e. starting of the device, and during the operating phase, standardizing the performance thereof in particular in terms of continuity and regularity of operation.

## Claims

### Claim 1

A plasma generator comprising:
a chamber;
a hollow cathode extending into said chamber;
means for introducing gas through said hollow cathode and into said chamber;
an anode positioned in said chamber and spaced from said hollow cathode, said anode defining an opening for plasma to pass through;
ionizing radiation source positioned in said chamber between said hollow cathode and said anode to inject radiation into said gas and to pre-ionize portions of said gas by transferring energy from said radiation to said portions of gas.

### Claim 2 (depends on 1)

A plasma generator in accordance with claim 1, further comprising:
another anode positioned spaced from said anode and on an opposite side of said anode from said hollow cathode;
another ionizing radiation source positioned between said anode and said another anode.

### Claim 3

A plasma generator for use in space vehicles, the plasma generator comprising:
a chamber;
a gas inside said chamber;
ionizing means for ionizing said gas in said chamber to form a plasma, said ionizing means including an ionizing radiation source positioned to inject radiation into said gas and to pre-ionize portions of said gas by transferring energy from said radiation to said portions of gas.

### Claim 4 (depends on 3)

A plasma generator in accordance with claim 3, wherein:
said ionizing means includes a plasma field means for accelerating free electrons in said gas with electromagnetic fields in order to ionize said gas and form a plasma.

### Claim 5 (depends on 3)

A plasma generator in accordance with claim 3, wherein:
said plasma field means generates radio frequency electromagnetic fields.

### Claim 6 (depends on 3)

A plasma generator in accordance with claim 3, wherein:
said ionizing radiation source is positioned outside said chamber.

### Claim 7 (depends on 3)

A plasma generator in accordance with claim 3, wherein:
said ionizing radiation source is positioned inside said chamber.

### Claim 8 (depends on 3)

A plasma generator in accordance with claim 3, wherein:
said ionizing radiation source emits one of .alpha., .beta., .gamma. and x radiations.

### Claim 9 (depends on 3)

A plasma generator in accordance with claim 3, wherein:
said ionizing radiation source is a radioactive source.

### Claim 10 (depends on 3)

A plasma generator in accordance with claim 3, further comprising:
gas means for introducing said gas into said chamber;
said ionizing radiation source being positioned adjacent and downstream of said gas means.

### Claim 11 (depends on 3)

A plasma generator in accordance with claim 3, further comprising:
extraction means for extracting charged particles from said chamber.

### Claim 12 (depends on 11)

A plasma generator in accordance with claim 11, wherein:
said ionizing means produces plasma when said chamber is in communication with an outer space environment, and said extraction means extracts said charged particles from said chamber into the outer space environment.

### Claim 13

A method for generating plasma in space vehicles, the method comprising the steps of:
providing a chamber in communication with an outer space environment;
introducing a gas into said chamber;
ionizing said gas in said chamber to form a plasma, said ionizing including injecting radioactive radiation from an ionizing radiation source into said gas to pre-ionize portions of said gas by transferring energy from said radiation to said portions of gas.