The valve and the pressure gauge of a gas ion laser were electrically insulated from the laser discharge path by connecting them in series with the cathode of the laser. The laser cathode can be grounded and preferably is a cold cathode although a hot cathode may be used instead. The cold cathode was provided with a central aperture to which was connected both the pressure gauge and the gas pressure reservoir through the valve. This will effectively prevent electric discharges from passing either to the pressure gauge or the valve which would otherwise destroy the pressure gauge

Witte, R. S.

Wood, C. E.

English

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FROM: GP-4/Office of Assistant General
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SUBJECT: Announcement of NASA-Owned U.S. Patents in STAR
In accordance with the procedures agreed upon by Code GP-4
and Code NHB, the enclosed NASA-owned U.S. Patent is being
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The following information is provided:
U.S. Patent No.
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA Patent Case No.
3,882,417
TRW, Inc.
Redondo Beach, CA
MFS-22,597-
NOTE - Is this an invention made by a corporate employee
of a NASA contractor? YES |
 x | NO [ " "|
If "YES" is checked, the following is applicable: Pursuant
to Section 305(a) of the National Aeronautics and Space Act,
the name of the Administrator of NASA appears on the first
page of the patent; however, the name of the actual jnventor
(author) appears at the heading of column No. 1 of the
Specification, following the words "...with respect Lo an
invention of ..."
Elizabeth A. Carter/
Enclosure
(NASA-Case-MFS-22597) GAS IOH LASEB
CONSTRUCTION FOB ELECTBICALIX ISOLATING THE
P8ESSURE GAUGE THEREOF Patent (NASA) 5 p
CSCL 20E
00/36
N78-17366
Unclas
05403
https://ntrs.nasa.gov/search.jsp?R=19780009423 2020-03-20T12:51:20+00:00Z
United States Patent 1191
Wood et al.
(in 3,882,417
[45] May 6, 1975
[541 GAS ION LASER CONSTRUCTION FOR
ELECTRICALLY ISOLATING THE
PRESSURE GAUGE THEREOF
[75] Inventors: Charles E. Wood, Manhattan Beach;
Robert S. Witte, Redondo Beach,
both of Calif.
[73] Assignee: TRW Inc., Redondo Beach, Calif.
[22] Filed: Sept. 10, 1973
[21] Appl. No.: 395,895
[52] U.S. Cl 331/94.5 T; 315/108; 331/94.5G
[51] Int. Cl HOls 3/22
[58] Field of Search 331/94.5; 330/4.3;
315/108
[56] References Cited
UNITED STATES PATENTS
3,424,997 1/1969 Lopez et al 331/94.5 G
3,745,483 7/1973 Huchital et al 331/94.5 G
Primary Examiner—Robert }. Webster
Attorney, Agent, or Firm—Daniel T. Anderson, Esq.;
Edwin A. Oser, Esq.; Jerry A. Dinardo
[57] ABSTRACT
A gas ion laser of the type provided with a pressure
gauge and a gas pressure reservoir connected to the
laser through a valve. The valve and the pressure
gauge are electrically insulated from the laser dis-
charge path by connecting them in series with the
cathode of the laser. The laser cathode can be
grounded and preferably is a cold cathode although a
hot cathode may be used instead. The cold cathode is
provided with a central aperture to which is connected
both the pressure gauge and the gas pressure reservoir
through the valve. This will effectively prevent electric
discharges from passing either to the pressure gauge
or the valve which would otherwise destroy the pres-
sure gauge.
5 Claims, 3 Drawing Figures
24
r
PATENTED HAY 61975 3,882.417
13
10 30
14
15
24
Fig. 1
I6
Fig. 2 Fig. 3
3,882,417
1 2
GAS ION LASER CONSTRUCTION FOR Another object of the present invention is to provide
ELECTRICALLY ISOLATING THE PRESSURE a gas ion laser of the type disclosed which permits to
GAUGE THEREOF ground not only the pressure gauge but the valve inter-
The invention described herein was made in the per- posed between the gas reservoir and the laser discharge
formance of work under a NASA contract and is sub- 5 tube.
ject to the provisions of Section 305 of the National A further object of the present invention is to provide
Aeronautics and Space Act of 1958, Public Law a gas ion laser having a cold cathode and having means
85-568 (72 STAT. 435; 42 USC 2457). for protecting the pressure gauge of the laser from an
e
'
eCtric gUSBACKGROUND OF THE INVENTION
 10
This invention relates generally to gas lasers, and par- SUMMARY OF THE INVENTION
ticularly relates to a gas ion laser of the type requiring In accordance with the present invention there is pro-
a pressure sensing gauge as well as a gas reservoir for vided a gas ion laser which comprises a main envelope
controlling the pressure of the gas in the laser. for the gas discharge which consists of an insulating
It is well known that gas ion lasers usually require a 15 material and includes an ionizable laserable gas. A
gas reservoir which is arranged in parallel with the laser cathode and an anode are disposed spaced from each
discharge tube. Such gas ion lasers are shown for exam- other and in communication with the main envelope. A
pie in in the patent to Neusel U.S. Pat. No. 3,466,567 pressure gauge is provided for measuring the pressure
and the patent to Witte U.S. Pat. No. 3,699,470, both in the main envelope. A connection is provided for in-
being assigned to the assignee of the present applica- terconnecting the pressure gauge with the main enve-
tion. As pointed out in these prior patents it is neces- lope through the cathode in such a manner that a series
sary to prevent the electric discharge which normally connection is formed between the anode, the cathode
passes through the laser tube from also passing through and the pressure gauge in the order named. Finally
the gas reservoir. .. there is a restricted metallic connection interposed be-
In order to minimize this undesired gas discharge tween the cathode and the pressure gauge for prevent-
through the gas reservoir of the laser the Neusel patent ing the discharge which normally passes through the
above referred to has suggested the use of a hold-off main envelope to the pressure gauge.
electrode in the tube interconnecting the laser dis- Accordingly, one of the features of the present inven-
charge tube to the gas reservoir. The Witte patent ^Q tion is to arrange the pressure gauge as well as the gas
above referred to has solved the same problem by in- reservoir, if required, in series with the cathode and the
serting an electrically conductive tube in the passage main envelope through which the gas discharge of the
interconnecting the laser discharge tube with the gas laser passes. This in turn makes it possible to maintain
reservoir of the laser. the cathode at a fixed reference potential, that is at
Both of these prior art ion lasers have been found to 35 ground. Accordingly, the pressure gauge may also be
be very effective for the purpose for which they were maintained at ground as well as a valve which may be
designed, i.e., for substantially preventing a gas dis- provided between the gas reservoir and the remainder
charge through the gas reservoir. However, the provi- of the laser. This will protect the operator from electric
sions of an electrically conductive tube between the gas shocks when touching the valve.
reservoir and the laser discharge tube has the disadvan- 40 Additionally, the cathode may be a cold cathode as
tage of providing a high impedance to the flow of gas. disclosed in the patent to Witte et al. U.S. Pat. No.
On the other hand, the hold-off electrode adds to the 3,555,451 and in a second patent to Witte et al. U.S.
complexity of the laser construction. Pat. No. 3,688,217. Both of these patents are assigned
Additionally, both of these constructions may still to the assignee of the present invention. The first one
permit agas discharge to pass occasionally through the 45 of these patents discloses the use of indium, gallium,
gas reservoir. This does not impede the proper opera- bismuth, tin and lead as suitable for a cold cathode.
tion of the laser. However, if such a gas discharge The second patent discloses the use of aluminum, cop-
should pass to the pressure gauge of the laser it will de- per, nickel, silver and tungsten as suitable for a cold
stroy the pressure gauge. Furthermore, the gas reser- cathode. In accordance with the present invention, the
voir usually is connected to the laser through a valve 50 cold cathode is provided with a central aperture which
and it is desirable to maintain this valve at ground po- in turn is connected with the pressure gauge through a
tential so as to minimize any danger to the operator due suitable tube.
to the high voltage which normally exists between the The novel features that are considered characteristic
laser electrodes. of this invention are set forth with particularity in the
On the other hand, the provision of the pressure appended claims. The invention itself, however, both as
gauge in communication with the laser discharge tube to its organization and method of operation, as well as
is vital for the operation of certain types of lasers. They additional objects and advantages thereof, will best be
usually have to be run in at a relatively high gas pres- understood from the following description when read
sure and therefore the pressure must be carefully in connection with the accompanying drawing.
watched. On the other hand, particularly at higher than
 g p DESCRIpT,ON QF JHE DRAW,NG
normal pressures the gas discharge has a tendency to
pass through the gas reservoir which in turn would de- FIG. 1 is a sectional view of a gas ion laser having a
stroy the pressure gauge. cold cathode and embodying the present invention;
It is accordingly an object of the present invention to ,, FIG. 2 is a sectional view on enlarged scale of the
provide a gas ion laser having means of protecting the cold cathode of the laser of FIG. 1 illustrating a metal-
pressure gauge of the laser which must be in communi- lie tube extending partly through a central aperture in
cation with the laser discharge tube. the cathode; and
3,882,417
3 4
FIG. 3 is an enlarged sectional view similar to that of The central opening 27 through the cold cathode 18
FIG. 2 and illustrating a hot cathode which may be used is small in diameter compared to the diameter of the
with the laser of the invention. main discharge tube or main envelope 10. This will also
minimize the danger of a discharge passing through the
DESCRIPTION OF THE PREFERRED
 5 tube 21 to the pr|ssure gauge 2|.
EMBODIMENT
 The iaser jnustrated jn FIG: 1 operates in a conven-
Referring now to the drawing and particularly to FIG. tional manner. A relatively high voltage is applied be-
1, there is illustrated a gas ion laser embodying the tween the anode 17 and the cathode 18, that is a high
present invention. The laser may, for example, include positive voltage is applied to the anode 17 since the
an ionizable laserable gas such as argon, krypton, xe- 10 cathode 18 is grounded. Such a gas laser can be made
non, and the like. The laser includes a main envelope to operate without a trigger electrode as long as a high
10 through which the gas discharge may be permitted enough voltage is applied between its two electrodes,
to pass. The envelope 10 preferably consists of an insu- As long as the tube is operated above the breakdown
lating material such for example as glass, quartz or a voltage of the gas it will fire, but usually at random,
suitable ceramic. The envelope 10 is provided with two 15 Therefore, in some cases it may be desirable to pro-
windows, 11 and 12, which are transparent to the light vide a tr'gger electrode which will preionize the gas in
produced by the laser. They may be disposed at the the ma™ envelope 10. This discharge may then be
Brewster angle which is such that the light passes maintained by a lower voltage applied between the
through substantially without reflection losses. The electrodes 17 and 18. In other words, this will separate
Brewster windows 11 and 12 will also incidentally po- 20 the funct'on of maintaining the discharge as compared
larize the light to t'le function of preionizing the gas which in turn per-
There are also provided two mirrors, 13 and 14, mits the discharge to take place. Accordingly, a trigger
forming a resonant cavity or mode selector for the laser electrode permits to control mdependently breakdown
radiation. As shown the mirrors 13 and 14 may be „ and discharge functions. Accordingly, a trigger elec-
spherical to minimize the problems of adjustment. One 25 trode 30 may be disPosed about the main envelope 10
of the mirrors, say mirror 13, may be designed to re- and may extend to a region below the anode 17. As
fleet substantially all of the radiation, while the other sKhown schematically in FIG. 1, a positive pulse 31 may
mirror, say mirror 14, may be arranged to pass a prede- be aPPlled to the transformer 32 haying one terminal
, ,,./ .. .... . . of the pair of windings grounded. This in turn will een-termmed percentage of the light to generate an output ->n . , .6 & . ,. „ * * • • , ? • ,
, D O j u
 erate m t h e secondary winding 3 3 a sufficiently high
_,' . . ,.. , -_i _i • i_ positive pulse which is applied to the trigger electrodeThe main envelope 10 may be provided with two ap- !,„ . . . ., S, . -Jr , , ,
, ,_ , ,, ,.
 J
. . ,.
 r
, 30 to preionize the gas. However, as indicated beforependaees 15 and 16 which as shown are disposed ... . . , , ,K
 f - , , , . . . . , , such a trigger electrode is not always necessary and
spaced from each other and in communication with the . . . 3
• , . / » . , ,-, ,j- j • , may be omitted,
mam envelope 10. An anode 17 may be disposed m the 35
 The central rture 27 th h the cold cathode 18
appendage 15. The anode 17 may, for example, consist
 does nQt . jf ^ function and tion of the cold
of a tungsten wire extending through the appendage 15.
 cathode This js due tQ ^  fact that ^ emjssion takes
The cathode 18 may, for example, be a cold cathode
 p,ace primarily around the edge of the cold cathode>
consisting of any of the materials referred to in the two
 that js around the jon adjacent to the wal, of the
Witte et al. patents and previously referred to. Thus, by 40
 pendage 15
way of example, the cold cathode 18 may consist of in- ^^
 has been indicated by the arrows 35 in FIG 2
"ium. which indicate the emission from the edge of the cold
The appendage 16 extends into a conductive tube 20
 cathode 18. FIG. 2 does show a modification of the
which may consist of any suitable metal. Preferably,
 cold cathode of FIG. 1. Here a tube 16 is shown which
however, the tube 20 is an alloy consisting of iron, 45
 may consist of some insulating material such as glass or
nickel and cobalt which is sold under the trade name quartz while the lower tube 20 may consist of Kovar.
"Kovar. " Such an alloy has substantially the same co-
 The coid cathode 18 may consist of indium. A graded
efficient of expansion as does glass and may therefore
 seai 37 may interconnect the Kovar tube 20 to the
be readily sealed by means of an interconnecting por- quartz or glass appendage 16. Otherwise, the modifica-
tion or graded seal to the appendage 16. Such an inter- 50
 tjon of tne cathode of FIG. 2 does not change the oper-
connecting portion may consist of a plurality of differ- ation of the laser previously disclosed,
ent glasses joined together to form a graded seal which However, it is not necessary that the cathode consist
matches the coefficient of expansion of tube 20 to that
 of a cold cathode. It is feasible to provide a hot cathode
of the remainder of the appendage 16. Connected to for the laser of the invention. This has been illustrated
the tube 20 by another interconnecting tube 21 is the 55 jn FIG. 3 to which reference is now made,
pressure gauge 23 which may, for example, consist of Here the hot cathode is shown schematically at 40 as
a heated wire and which is conventional. The tube 21 a wire having one end grounded as shown. The append-
may again consist of glass or quartz or alternatively of age 16 continues to connect to a metal tube 20 of much
a suitable metal. A gas reservoir 24 may be connected reduced diameter which may be grounded as shown,
to the tube 21 through a valve 25 shown schematically However, the operation of the laser is the same as that
in FIG. 1. The valve 25 may be grounded as shown as previously explained,
is the pressure gauge 23. There has thus been disclosed a gas ion laser having
The tube 21 if made of metal may be connected to provision for positively protecting the pressure gauge
the tube 20 made of Kovar by silver solder. If the tube .. of the laser from any accidental discharge. This is ef-
21 is made of metal it preferably consists of oxygen- fected by connecting the pressure gauge as well as a gas
free copper. This will minimize the danger of contami- reservoir when needed serially with the main laser en-
nation of the ionizable gas. velope. The connection is made through the cathode.
3,882,417
The cathode may, for example, be a cold cathode hav-
ing a central aperture interconnecting the pressure
gauge to the main envelope. Alternatively, a hot cath-
ode may be used which continues through a metallic
connection of reduced diameter to the pressure gauge. 5
The resultant construction is simple and may easily be
made without substantially increasing the price of the
instrument. The laser of the invention has been oper-
ated successfully.
What is claimed is: 10
1. A gas ion laser comprising:
a. a main envelope consisting of an insulating mate-
rial and including an ionizable laserable gas;
b. a first appendix in communication with said main
envelope; 15
c. an anode disposed in said first appendix;
d. a second appendix in communication with said
main envelope;
e. a cathode disposed in said second appendix, said
cathode being a cold cathode formed by a slug of 20
metal substantially filling said second appendix and
having a central aperture therethrough;
f. a pressure gauge for measuring the pressure in said
main envelope;
g. a metallic tube interconnecting said central aper- 25
ture in said cathode with said pressure gauge,
whereby said anode, said cathode and said pressure
gauge are interconnected in series to permit a con-
tinuous gas movement therein, said metallic tube
extending partially through the central aperture in
said cathode;
h. means coupled to said anode and to said cathode
for applying an electric potential thereto and for
creating a discharge through said main envelope in
the laserable gas; and
1. means optically coupled to said main envelope for
stimulating a coherent beam of radiation from the
laserable gas.
2. A laser as defined in claim 1 wherein said cold
cathode consists of indium.
3. A laser as defined in claim 1 wherein a gas reser-
voir and a valve are connected to said tube.
4. A laser as defined in claim 1 wherein means is pro-
vided for maintaining said cathode at a fixed reference
potential.
5. A laser as defined in claim 1 wherein a trigger elec-
trode is provided which substantially surrounds said
main envelope and said anode for preionizing said la-
serable gas to facilitate lasing action thereof.
30
35
40
45
50
55
60
65


Gas ion laser construction for electrically isolating the pressure gauge thereof

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