DE9007390U1 - Device for cleaning laser gas - Google Patents

Description

WUFSTHOFI--& WUESThOFF

PATENT AND LAWYER!!

PATENT ATTORNEYS

EUROPEAN PATENT ATTORNEYS

FRANZ WUESTHOFF, DR. ING. FREDA WUESTHOFF, DR PHIL. (1927-1956) Phueilf E.FREIHERRVONPECHMANN.DR.DIPLCHEM

7^&Idigr;2 co* ^{DIETER BEHRENS} · ^{DR ING}

1G-66 834 JÜRGEN BRANDES, DR DIPL CHEM.

26 March 1991 Rupert Goetz, dipl.ing dipl.wirtsch. ing

AXEL VON HELLFELD, DR. DIPL-PHYS.

ATTORNEY GERT WÜRTENBERGER

SCHWEIGERSTRASSE 2 D-8000 MUNICH

FAX (089)663936 TELEX 524070 TELEPHONE (089) 662051

Device for cleaning laser gas

The invention relates to a device for cleaning laser gas.

With gas lasers, especially excimer lasers or CO^ lasers, the laser gas becomes contaminated during operation. The laser gas is excited by a gas discharge, whereby dirty gases and substances can be formed by chemical reactions, removal from the laser electrodes, reactions on the walls, etc.

The dirty gases and substances impair the laser performance. Especially for long-term operation of the laser, it is necessary to remove the contaminants from the laser gas.

Devices for cleaning laser gas are known in the state of the art. For this purpose, laser gas is led out of the resonator, transferred to a cleaning device and returned to the resonator in a circuit in a cleaned state.

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However, especially with sensitive laser gases such as F_, ArF and at high pressures of more than 3.5 bar, conventional devices for cleaning laser gas are insufficiently effective.

Coaxial heat exchangers with a pre-cooling stage to increase efficiency are known from DE-OS 39 19 771. A coaxial heat exchanger enables good heat exchange between the warm, uncleaned laser gas and the cold, cleaned laser gas due to the large surface area of the barrel tube and, if necessary, additional surface shaping (ribbing, etc.). The laser gas cleaner known from DE-OS 39 19 771 has a relatively complicated gas routing system.

The invention aims to create simple and thus cost-effective devices for cleaning laser gas that have a high degree of efficiency despite their compact design.

According to one embodiment of the invention, a device for cleaning laser gas, which has a cold trap and a heat exchanger connected upstream of it, is designed so that the heat exchanger surrounds the cold trap. This enables a compact design with high efficiency.

Preferably, the heat exchanger upstream of the cold trap is formed from two helical, coaxial tubes of different diameters, with warm laser gas entering one of the tubes, entering a cold trap after passing through the tube, and entering the other of the two coaxial tubes after passing through the cold trap.

According to a further preferred embodiment of the invention, the cold trap is cylindrical and has a central cooling body around which the gas flows. This variant

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The invention is particularly suitable for use with a cryostat as a cold source.

According to a further preferred embodiment of the invention, the cold trap is formed from two concentric, cylindrical tubes. Pre-cooled gas emerging from the heat exchanger enters the outer of the concentric tubes of the cold trap near its upper end, flows downwards in the outer tube and from there reaches the inner of the concentric tubes near its lower end, from there flows upwards around a cooling body and then re-enters the heat exchanger as cleaned and cooled gas, where it pre-cools gas coming from the laser.

An embodiment of the invention is explained in more detail below with reference to the drawing. It shows:

Fig. 1 shows a vertical section through an embodiment of a device for cleaning laser gas.

Fig. 1 shows a device for cleaning laser gas, which has both a cold trap and a heat exchanger. The device is preferably used when using a cryostat.

In an insulation chamber 40, the components shown are arranged in a largely thermally insulated manner. For this purpose, the insulation chamber 40 is either evacuated or filled with a low-temperature insulation material.

Gas coming from the laser (not shown) enters the device in the direction of arrow 42 and leaves the device in the direction of arrow 44 to the laser.

s &igr; &eegr;

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The device according to Fig. 2 can be roughly divided into a heat exchanger and a cold trap. The heat exchanger consists of concentric, spirally arranged tubes 46, 48. The spiral-shaped tubes 46, 48 of the heat exchanger surround the cold trap, which essentially consists of the hatched components 52, 54 and 56.

A cold head 50 of a conventional cryostat is connected in good thermal contact with a heat sink 52, which serves as a cooling source for the cold trap.

Furthermore, the cold trap has an inner tube 54 which is concentric with the central cooling body 52 and which is provided on the outside with helical fins 58. The helical fins 58 extend between the outer casing of the inner tube 54 and an outer tube 56 of the cold trap, so that a flow path for the gas is formed between the tubes and the fins. Only the upper and lower fins are shown in Fig. 4.

At the lower end of the inner tube 54 there is a passage 60 which leads to a flow path 62 between the heat sink and the inner tube 54. This flow path 62 is spiral-shaped, with only the lower and upper spiral sections being shown in Fig. Λ .

At the vertically upper end of the cold trap, an inner cover 64 for closing the inner space of the inner tube 54 and an outer cover 66 for closing the space between the inner tube 54 and the outer tube 56 are provided.

The flow path of the gas is as follows:

90

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In the direction of arrow 42, warm gas coming from the laser, which is to be cleaned, enters the device and flows upwards in the inner tube 48 and then in the direction of arrow P into the cold trap. As it passes through the tube 48, the gas is pre-cooled, as described in more detail below. In the direction of arrow P, the gas enters from above into the flow path formed between the inner tube 54 and the outer tube 56 by the helical ribs 58 and flows downwards through the passage 60 and then into the flow path 62 between the heat sink 52 and the inner tube 54. There, the gas flows upwards and then enters in the direction of arrow P as cleaned and cooled gas into the outer tube 46 of the heat exchanger formed from the concentric tubes 46 and 48. There, the gas flows from top to bottom and then leaves the device in the direction of arrow 44. As it flows through the pipe 46, the cleaned and cooled gas pre-cools the gas entering the inner pipe 48 in the direction of arrow 42 in a countercurrent process.

The heat exchanger consisting of tubes 46 and 48 shown in Fig. 1 can also be combined with a cooling trap other than that shown in Fig. 2, e—•

π ■:

Claims (6)

WUFSfHOF: ⁷ & WUFSTHOF F PATENT AND LAWYERS PATENT ATTORNEYS EUROPEAN PATENT ATTORNEYS FRANZ WUESTHOFF, DR. ING. FREDA WUESTHOFF, DR PHIL (1927-1956) T>Vi\rciV E. FREIHERR VON PECHMANN, DR. DIPLCHEM 7&ogr; ~ &ogr; öS ⁷ DIETER BEHRENS, DR ING 1G-66 Ojy JÜRGEN BRANDES, DR DIPL CHEM. 26 March 1991 Rupert Goetz, Dipl. Ing. Dipl.Wirtsch Ing DIPL PHYS. ATTORNEY GERT WÜRTENBERGER SCHWEIGERSTRASSE 2 D-8000 MUNICH 90 FAX (089) 663936 TELEX 524070 TELEPHONE (089) 662051 S c hu t &zgr; a &eegr; sayings 1. Device for cleaning laser gas with a cold trap (52, 54, 56, 58, 60) and a heat exchanger upstream of this (46, 48), in which the gas is pre-cooled before entering the cold trap, characterized in that the heat exchanger (46, 48) surrounds the cold trap (52, 54, 56, 58, 60). 2. Device according to claim 1,
characterized in that the heat exchanger (46, 48) is formed helically from coaxial tubes. 3. Device according to one of claims 1 or 2, characterized in that the cold trap (52, 54, 56, 58, 60) is cylindrical and has a central cooling body (52) around which the gas flows. 4. Device according to claim 3,
characterized in that the cold trap (52, 54, 56, 58, 60) has two concentric - 2 - lG-66 cylindrical tubes (54, 56), wherein the cooling body (52) is arranged in the inner tube (54) and leaves a curved flow path (62) for the gas. 5. Device according to claim 4,
characterized in that pre-cooled gas from the heat exchanger (46, 48) enters the lower (56) of the concentric tubes (54, 56) near its upper end, flows downwards in the outer tube (56), then enters the lower (54) of the concentric tubes (54, 56) near its lower end, flows upwards around the heat sink (52) and then enters the heat exchanger (46, 48). 6. Heat exchanger for a device for cleaning laser gas, marked by two coaxial, helical tubes (46, 48), wherein warm laser gas enters one (48) of the tubes (46, 48), after passing through this tube (48) enters a cold trap (52, 54, 56, 58, 60) and after passing through the cold trap enters the other (46) of the two coaxial tubes (46, 48).