A rapid pulsing, high intensity, incoherent light is produced by selectively energizing a plurality of discharge lamps with a triggering circuit. Each lamp is connected to a capacitor, and a power supply is electrically connected to all but one of the capacitors. This last named capacitor is electrically connected to a discharge lamp which is connected to the triggering circuit

Brandhorst, H. W., Jr.

Evans, J. C., Jr.

English

NASA Technical Reports Server

* S
REPLY TO
ATTN OF: GP
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546
MAY 1 1974
TO: KSI/Scientific & Technical Information Division
Attn: Miss Winnie M. Morgan
FROM: GP/Office of Assistant General
Counsel for Patent Matters
SUBJECT: Announcement of NASA-Owned U.S. Patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, the attached NASA-owned U.S. Patent is being
forwarded for abstracting and announcement in NASA STAR.
The following information is provided:
U.S. Patent No. :
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA Patent case No.
o o e/- A
'- a 5*3^ -
NOTE - If this patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:
YES /— / NO
Pursuant to Section 305 (a) of the National Aeronautics and
- Space-Act ,_the_nam^ jof the Administrator of NASA appears on
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inventor (author) appears at the heading of column No. 1 of
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an invention of ..."
C
Bonnie L. Woerner
Enclosure
https://ntrs.nasa.gov/search.jsp?R=19740012746 2020-03-17T14:49:12+00:00Z
United States Patent
* «
Evans, Jr. et al.
[in 3,806,835
[45] Apr. 23, 1974
[54] RAPIDLY PULSED, HIGH INTENSITY,
INCOHERENT LIGHT SOURCE
[75] Inventors: John C. Evans, Jr., Kent; Henry W.
Brandhorst, Jr., Berea, both of Ohio
[73] Assignee: The United States of America as
represented by the Administrator of
the National Aeronautics and Space
Administration, Washington, D.C.
[22] Filed: Sept. 13, 1972
[21] Appl. No.: 288,856
Related U.S. Application Data
[62] Division of Ser. No. 848,403, July 29, 1968, which is
a division of Ser. No. 487,929, Aug. 16, 1965,
abandoned.
[52] U.S. Cl 332/7.51, 331/94.5 D, 315/211,
315/228
[51] Int. Cl H01s3/09
[58] Field of Search 331/94.5 D; 315/241 R,
315/228,223,211; 332/7.51
[56] References Cited
UNITED STATES PATENTS
2,835,850 5/1958 Morel 315/211
3,311,844 3/1967 Curcio 331/94.5 P
3,270,296 8/1966 Maurer 331/94.5 P
3,569,861 3/1971 Tucker et al 331/94.5 R
3,413,567 11/1968 Hanwacker et al 332/7.51
FOREIGN PATENTS OR APPLICATIONS
947,568 1/1964 Great Britain :... 331/94.5 A
Primary Examiner—Maynard R. Wilbur
Assistant Examiner—N. Moskowitz
Attorney, Agent, or Firm—N. T. Musial; G. E. Shook;
J. R. Manning
[57] ABSTRACT
A rapid pulsing, high intensity, incoherent light is pro-
duced by selectively energizing a plurality of discharge
lamps with a triggering circuit. Each lamp is con-
nected to a capacitor, and a power supply is electri-
cally connected to all but one of the capacitors. This
last named capacitor is electrically connected to a dis-
charge lamp which is electrically connected to the
triggering circuit.
6 Claims, 3 Drawing Figures
'ATENTOiAPK23IQ7' i
SHLEI 1 OF 2
3.806,83.5
27
41
FIG. I
J'ATI:NTEOAPfi23i974
SHEET 2 OF 2
.806,6353 Q
177
nnn
FIG. 3
- • - 3,806,835
1 2
RAPIDLY PULSED, HIGH INTENSITY, of these pulses yields a higher average power than a
INCOHERENT LIGHT SOURCE • single giant pulse which, in turn, results in an increased
laser output.
REL ATED APPLICATION Several embodiments of the invention may be uti-
t KC.LA i tu /\»-rLi^A i IUIN 5 Iized tQ achieve repetitive pulsing wherein the laser is
This application is a division of copending applica- fired more times per unit. In one embodiment a plural-
i tion Ser. No. 848,403, filed July 29, 1968 which, in ity of six xenon flash tubes are circumferentially dis-
•J turn, is a division of application Ser. No. 487,929, filed posed around a laser rod and are fired repetitively in
Sept. 16, 1965 and now abandoned. succession by the use of high speed motor connected
ORIGIN OF THF INVENTION '° l° a" a1"01"01''16-^  distributor which triggers a suit-ORIGIN OF THE INVENTION
 ab,e firing drcuit -^ flash tubeg ^  ^^4 through
The invention described herein was made by employ- a bank of fast charging capacitors. The apparatus is so
ees of the United States Government and may be man- arranged so that while one of the capacitors is discharg-
ufactured and used by or for the Government for gov- ing into one of the flash tubes and causing it to fire the
ernmental purposes without the payment of any royal- 15 other five capacitors are being charged,
ties thereon or therefor. Another embodiment of the invention involves an ex-
^.^.,^,^^, »,~ ~- .,.,..-. .»„ -,. .~ ploding wire mounted on a reel which is moved by highBACKGROUND OF THE INVENTION
 s
P
peed *riving motor ^ wjre fa mounted SQ as ^  ^
This invention is concerned with a method and appa- through one of two electrodes and is movable towards
ratus for producing a source of incoherent light capable 20 the other electrode. When the wire comes into contact
of initiating laser action in laser material. The word with the other electrode, a circuit is closed, producing
laser is an acronym for the phrase "light amplification thereby a high intensity flash of light,
by stimulated emission of radiation." The instant inven- Repetitive pulsing or increasing the output pulses per
tion is intended for particular use with lasers utilizing unit time results in a high power density beam for an
a solid laser material such as ruby to produce a narrow 25 extended period of time. By way of example, a repeti-
beam of coherent light. tion rate" of 20 pulses per seconcTFor a 50 joule pulse
The operation of the laser is based on the fact that will issue a kilowatt of laser power. However, a flashing
the atomic systems represented by the molecules of the rate of 1000 per second will result in a power output
laser material can exist in any series of discreet energy of 50 kilowatts.
levels or states. These systems absorb energy when 30 ,^.,.,-^™, ^^-^...^ ,,,,,.-..,-r..~.,
going to a higher state and emit energy when going to OBJECTS OF THE INVENTION
a lower state. The atomic systems are raised from the It is, therefore, an object of the present invention to
lower or ground level to the higher of the three levels provide an improved method and apparatus for pro-
by irradiation from a strong light source which need not ducing incoherent light. When this incoherent light is
be coherent but should preferably have a high concen- 35 used for pumping a laser material, a high intensity light
tration of energy in the shorter wave length. The opera- having a high pulsing rate is produced,
tion of raising the energy level of the laser to produce Another object of the invention is to provide an im-
the desired photon emission is referred to in the art as proved incoherent light for producing a laser output
optical pumping. having a high average power density.
Optical pumping may be achieved by, for example, 40 A further object of the invention is to provide an ap-
discharging a conventional capacitor into a xenon- paratus for easily controlling the output of a laser,
filled flash lamp. The light output of the lamp is then A still further object of the invention is to improve a
sufficient to promote laser action. At the present time laser apparatus having modest energy storage require-
the light output of flash lamps is rated generally be- ments and wherein capacitors forming a part of the
tween 100-100,000 joules depending upon construe- power supply for the light source are capable of opera-
tion and design details. Conversion of this light into tion at higher frequencies.
laser'dutput is around 4~percent efficient and hence, A still further object of the invention is to provide for
laser beams up to 4000 joules can be obtained. Simulta- a laser apparatus wherein the size of the capacitor
neous flashing of several lamps is also in use. banks or the power supply are relatively small.
Certain desired uses for lasers such as point to point These objects and advantages of the invention will be
power transmission, welding, rock drilling, and materi- apparent from the specification which follows and from
.. als cutting would appear to require high energy density the drawing wherein like numerals are used throughout
in the laser beam. - - - - - to identify like parts.
It has been proposed to increase the power output of nFsrRlPTlON OF THF lip AWiNr.<;
• a laser beam by increasing the power density of a single 55 DESCRIPTION OF THE DRAWINGS
pulse laser. However, it would appear to be difficult to FIG. 1 is a combination pictorial and schematic view
handle the giant pulse thus produced, and hence, such of one embodiment of a laser-type energy transmitter;
an arrangement would have very limited application.
,~.,^, *n FIG. 2 is a pictorial representation of a power trans-SUMMARY OF THE INVENTION 60
 mission system ^  the
H
energy transmitt£r of FIG ,.
These problems have been solved in accordance with and
the present invention by increasing the flashing rate of FIG. 3 is a view in elevation of another embodiment
the source of incoherent light. More particularly, the of a laser-type energy transmitter,
lasers are fired more times per unit time interval. In-
 65 DESCRIPTION OF THE PREFERRED
creasing the flashing rate or firing rate of the source of EMBODIMENT
incoherent light results in a series of low amplitude out-
put pulses. The time integration of the energy content Referring now to FIGS. 1 and 2, there is shown in
3,806,835
FIG. 2 a cylindrically-formed crystal or rod 11 of a
laser material, such as ruby. The crystal or rod 11 is
preferably of the type shown in application Ser. No.
442,548 which was filed Mar. 24, 1965 and is now
abandoned. This laser material is activated by a rapid
pulsing light source.
In the preferred embodiment, the light source in-
cludes the plurality of six xenon discharge lamps 21
through 26, circumferentially surrounding the laser
rod 11 and mounted on a common lamp bank 27. The
. six xenon discharge lamps 21 through 26 are each rated
at 3000 watt seconds. The xenon discharge lamps 21
through 26 are arranged by a mechanical switching
means so as to repetitively fire in succession.
The xenon discharge lamps 21 through 26 are ener-
gized by means of a capacitive-type discharge circuit
and are triggered by means of an induction coil circuit.
The capacitor-type energizing circuit and the induction
coil triggering circuit are mechanically coupled to the
xenon discharge lamps 21 through 26 so as to provide
for repetitive firing in succession.
The capacitor energizing circuit includes six capaci-
tors 31 through 36 connected to a common bank 37.
Each one of the capacitors 31 through 36 is electrically
connected to one of the xenon discharge lamps 21
through 26; i.e., capacitor 31 is electrically connected
to xenon discharge lamp 21, etc. The capacitors 31
TTcv"with a selftEFough 36 are preferably^ 15 mfd at 2
inductance of 0.06 microhenries. The energy content
of each capacitor 31 through 36 is approximately 3000
joules.
The capacitor bank 37 is powered by means of a
power supply circuit including a high voltage power
transformer 41 connected to a full bridge rectifier 42
which in turn is connected to a charging reactor 43.
The full bridge rectifier 42 converts the alternating cur-
rent to direct current and the charging reactor 43 limits
the charging current to a safe value. Power from the
charging reactor 43 is transmitted to the capacitor
bank 37 through a commutator-type switch 51. Diodes
44 through 49 prevent current from flowing back to the
power supply. The switch includes a rotating member
52 having a cutaway portion 53 and adapted thereby to
contact and transmit current to all but one of the ca-
pacitors. The rotating member 52 is mounted on an
electrically conductive shaft 54.
The induction coil triggering circuit has a plug 60 and
includes a step down transformer 61, an interrupter 62,
By means of this coupling arrangement at any one in-
terval of time, one of the xenon discharge lamps 21
through 26 will be firing.
For example, with the switches in the position shown
5 in the embodiment in FIG. 1 capacitors 31, 32, 33, 35
and 36 are being charged. At the same time the induc-
tion coil triggering circuit is connected through the au-
tomobile-type distributor switch 71 to trigger coil 84
which is connected to the xenon discharge lamp 24.
10 The gas in the lamp 24 is ionized providing an electrical
path and causing the capacitor 34 connected across
said lamp 24 to discharge and the lamp 24 to thereby
flash brightly. During this flashing time all the other ca-
pacitors, i.e. 31, 32, 33, 35 and 36 are charging and as
15 the distributor shaft 91 rotates, another trigger coil is
energized and another lamp is fired.
In FIG. 2 is shown in simplified form an entire system
for transmitting power utilizing the laser apparatus of
FIG. 1. It should be noted however, that the laser appa-
20 ratus of FIG. 3 could also be employed. Although not
shown in FIG. 2 the distributors and attendant power
supplies are physically located in the center of the ca-
pacitor bank. The capacitor is enclosed within a cool-
ant tank 38. Circumferentially disposed around the
25
 laser rod 11 are the six flash tubes 21 through 26. The
entire laser assembly is also enclosed within a cooling
chamber 28. Recirculating pump 39 connects the cool-
. ant tank 38 to the laser chamber 28.
The coherent light emitted from the laser transmitter
30
 is collected at a distant point by an energy collector in
the form of a parabolic reflector 171 having at its focus
a plurality of high current solar cells 172. These solar
cells 172 are mounted at the focal plane of and sup-
ported from the reflector by means of tubes 173 and
174 which also serve as coolant channels. These chan-
nels 173 and 174 carry a coolant from a pump and tank
175. The coolant is transmitted to channel 173 through
a mirror support 176 which is also a channel and is car-
ried back from this channel 174 through mirror support
177.
DESCRIPTION OF AN ALTERNATE
EMBODIMENT
In FIG. 3 is shown another embodiment of the instant
invention wherein repetitive flashing is obtained by
means of an exploding wire. In this embodiment a
length of wire 111 mounted on a wire reel 121 is fed
through a pair of rollers 122,123 and moved in a direc-
tion of a firing block 124 which is spaced apart from
35
40
45
a capacitor 63, and an induction coil 64. The plug 60 50 the rollers 122, 123. When the wire 111 comes into
is adapted to be connected to a source of voltage. contact with the firing block 124 a circuit consisting of
Power from the induction coil triggering circuit is se-
lectively transmitted through an electrical conductor
65 from a switch 71 to a plurality of six trigger coils 81
through 86 which are connected respectively to the six
discharge lamps 21 through 26.
The switch 71 which may be in the form of an auto-
mobile distributor-type switch which is electrically con-
ductive and the power supply (or commutator) switch
51 are mechanically coupled by means of a drive shaft
91 which is turned by means of a variable speed motor
92 which may be regulated by a variable speed control
means 95 such as silicon controlled rectifiers or thyra-
trons. Couplings 93 and 94 electrically separate the
commutator switch 51 and the distributor switch 71.
The switch 71 includes a disc 72 mounted on an electri-
cally conductive shaft 73.
55
a bank of rapid cycling high voltage capacitors 131
connected to the firing block 124 and the rollers 122,
123 is completed and the bank of high voltage capaci-
tors 131 are discharged causing the wire 111 to ex-
plode. While the free end of the wire 111 is moving
toward the firing block 124, the bank of high voltage
capacitors 131 is being charged through a high fre-
quency power supply 141. The feed system includes a
drive motor 151 mechanically connected to the rollers.
A blocking diode 142 is connected between the high
frequency power supply 141 and the bank of high volt-
age capacitors 131. The wire 111 and laser rod 161 are
enclosed in a vacuum chamber 162.
Obviously, many modifications and variations of the
present invention are possible in light of the above
teachings. It is therefore to be understood that, within
3,806,835
the scope of the appended claims, the invention may be
practiced other than as specifically described.
What is claimed is:
1. Apparatus for producing rapid pulsing, high inten-
sity, incoherent light for use in optically pumping a 5
body of laser material comprising
a plurality of gaseous discharge lamps surrounding
said body of laser material, and
electromechanical means connected to said gaseous
discharge lamps for continuously firing each of said ] o
gaseous discharge lamps in succession, said elec-
tromechanical means including
a capacitor electrically connected to each of said gas-
eous discharge lamps,
triggering circuit means for providing a high voltage 15
and adapted to be selectively connected to each
one of said gaseous discharge lamps,
power supply means electrically connected to each
one of said capacitors for charging said capacitors,
and 20
mechanical switching means for simultaneously
opening the circuit between the power supply
means and one of said capacitors while closing the
triggering circuit means connecting said gaseous
discharge lamp to said same capacitor. 25
2. Apparatus for producing rapid pulsing, high inten-
sity, incoherent light as claimed in claim 1 wherein said
mechanical switching means comprise
a drive shaft,
variable speed motor connected to said drive shaft 30
for turning said drive shaft,
a distributor mounted on each end of said drive shaft,
means connecting one of said distributors to said plu-
rality of capacitors, and
means connecting said other distributor to said plu-
rality of gaseous discharge lamps.
3. Apparatus for producing rapid pulsing, high inten-
sity, incoherent light as claimed in claim 2 including
means for electrically connecting the power supply
means to said distributor shaft, and
means for electrically connecting the triggering cir-
cuit means to said distributor shaft.
4. Apparatus for producing rapid pulsing, high inten-
sity, incoherent light as claimed in claim 1 wherein the
energy content of each capacitor is about 3000 joules.
5. Apparatus for producing rapid pulsing, high inten-
sity, incoherent light as claimed in claim 4 wherein
eacffcapacitbr is 15 mfd aT20 kvr with" a~self induct-
ance of 0.06 microhenries.
6. A method of producing rapid pulsing, high.inten-
sity, incoherent light for optically pumping a body of
material capable of producing coherent light compris-
ing the steps of
electrically connecting a capacitor to each of a plu-
rality of gaseous discharge lamps,
repetitively firing each of said gaseous discharge
lamps in succession at a high rate around said body
of material capable of producing coherent light by
sequentially discharging the capacitors into their
. respective gaseous discharge lamps thereby caus-
ing said lamp to fire, and
charging the remaining capacitors while each capaci-
tor is being fired. .
35
40
45
50
55
60
65



Rapidly pulsed, high intensity, incoherent light source

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