eng n2tealaser

8/12/2019 Eng n2teaLaser

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. : Homemade Air Nitrogen Laser (Guide) : .

Nitrogen laser operates on transitions of second positive system of.... blah...blah...blah... All this junk is

not required to make a laser. This type of laser is attractive due to the fact that it can be constructed with

resources all easy to get. You will not overheat Yuour brain by the queations like 'where to get ruby' or

neodimium glass or rare and !A controlled dyes. You won't need rare mirrors and twisted alignment.

The laser is superradiant i.e. works mirorrless. At last it operates in the ultraviolet range. "ractically this is

almost as good as if it was in visible # many things are luminiscent under $% so the laser spot is easily

observable. &That cannot be said about () laser # until it burns something You never know if it operates

at all.*

This laser or either its design aren't invented by me. The guide is made by steps of the one at

http+,,www.sparkbangbu--.com,tealaser,tealaser.htm/or a while 0 thought that sparkbangbu--'s guide is

perfect and there's no need to translate my version into english. 1owever after a long time of work with

gas lasers and high voltages a new step of understanding came2 so some new information appeared in thisguide that may be interesting for english#speaking people too. Never say 3never32 lol.

I. Resources.

4e will need+

5. 6omething plane and hard enough &for basement*. The si-es of the plate should be about of A7

printing format. 0've got a glased tile )889:88 mm si-ed.

(ne could also take a thick te9tolite sheet or &even better* a plane sheet of iron &it is handy to use

magnets to attach all things to the iron*. on't use wood. 0t is very unstable when humidity

changes.
http://www.sparkbangbuzz.com/tealaser/tealaser7.htmhttp://www.sparkbangbuzz.com/tealaser/tealaser7.htmhttp://laserkids.getenjoyment.net/http://www.sparkbangbuzz.com/tealaser/tealaser7.htm


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). dielectric foil &film* with thickness at about 588 mcm2 (ne may use transparent printer sheets2

garden polyethylene &fresh one is better*2 overhead plastic2 etc... etc... The best choice is of course

th mylar &can easily be found as laminating pouches*2 however this guide will be oriented to the

'poor man's solution' utili-ing polyethylene sheets. 4hen the foil is unknown2 You should measure

its thickness beforehand.

:. fresh &clean and level* aluminium angle stock &better when directly from the shop*. The required

amount of the aluminium angle should allow You to cut three pieces )8 cm long each. 6ide of the

angle should be 5;..); mm2 wall thickness 5..5.; mm

As the e9perience shows2 the aluminium angle stock is the most hard to get part. 0f You have one2the rest will be easy. Also 0 should note that it is almost impossible to say how to replace it in case

if You can't obtain it.


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the thicker the better

;. aluminium duct tape &78..;8 mm wide* (f course You may avoid it and use only kitchen foil. =ut

with sticky aluminium strips all becomes easier.


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>. power supply rated at above > kv &easy check # it must be able to give ? mm long spark between

pins*

You can obtain one by+

scavenging from an old laser printer &where it is used to charge printing drum*

e9tracting a hori-ontal trace generator from an old tv set &the @T one2 not


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(ne more note. 0f You are going to feed the laser by an electrostatic machine be sure to take all

measures to eliminate corona discharge. The electrostatic machine gives output barely enough to

feed an air laser with rude design &in most cases just not enough*

The power supply may look like that+

. some weights &or magnets if you do assemblage on a steel sheet*.

The weights should be rather heavy &)8 g or above* otherwise You will not be able to make good

contact.


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?. @esistor rated to 58 k(hm or more. The resistor should be able to endure feeding voltage. 0n thesimpliest case choose rather high power one. 8.; 4 should be enough if dry or 8.); 4 if varnished.

The resistor can easily be replaced by an induction coil &see pictures a bit further below*

. @esistor &ballast* rated to :88 k(hm or above

This one will be used to limit the laser's repetition rate and also will protect power supply from

shortenings and voltage shocks which appear e9tensively when laser works.

58.4hite &very white* paper. 0t will serve as visuali-er of $% light. 0f You have no sheet of bright

white paper &like datacopy&tm** then use any other paper2 however You have to paint it with a

fluorescent marker.

55."lastic bottle lid2 piece of :89:89:8 angle2 B? screw2 and a nut to pair with it. This stuff will

become a spark gap in future.


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4e will also need the ne9t tools+

5. 6cissors

). Betal working hacksaw

:. /ine grit filer or sandpaper

7. 6crewdriver with a large dielectric handle

;. ruler

>. marker

. a glue &fast curing epo9y one is best*

II. Assemblage.

5. $sing the hacksaw cut : pieces of aluminium angle stock2 )8..)5 cm long each.

Those will be the laser electrodes. 0B"(@TANT not to defrom the angle stock. 6aw it slowly and

with only soft hits. 0t is also important not to make scratches on the working edges of the

electrodes.

). @ound the sharp corners with the filer.


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Bark it # near the middle draw two parallel straight lines2 spaced by :..7 mm from each other.

7. ut &with scissors* si9 equal pieces of the aluminium duct tape2 5 cm long.

The foils of laser's capacitor should be by )..: cm shorter than electrodes # it helps to supress the

sparks at ends of the electrodes. Those sparks are usually very annoying.

;. Turn the polyethylene for the drawing be underneath. &0n order to marker's dye not to char2 and to

avoid flashovers throug those charrings.* 6tick the first two strips of alunminium duct tape parallelto each other with a gap of :..7 mm. Thats where the marks come in use.


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ATTENTION! Te ga and arallelism are critical!.0n principle the laser does work

with gaps from ) mm to > mm and when the foils &but not the electrodes* are unparallel up

to C) mm per their length. =$T. Ba9imum power will be only with gap lying between

:mm to 7mm and when it is equal all along the electrodes. Too wide2 too narrow or slopped

gap will drastically reduce laser output. /urther reading will make it clear why it happens.

0n principle one can make top plates &wings* without using the aluminium duct tape2 just using the

kitchen foil. =ut

0t bugs to adjust the spacing between foils anytime

The foil lies non uniformly2 that leads to more often breakdown of the polyethylene

0 tried many combinations+ upp and down # sticky aluminium2 up # kitchen foil bottom # sticky

aluminium2 up and down # kitchen foil up # sticky down # kitchen foil. =etter resultsa are when

aliminium duct tape is up and kitchen foil is down.

>. !9tend wings by sticking another aluminium strips.


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4ider than 58 cm is senseless # laser would not light brighter. /urther on it is needed to make an

electric contact between aliminium strips in pairs. 0t seems to be simple to stick another strip above.

1owever the glue on the aluminium duct tape is dielectric. And even when it easily breaks down

under the feeding voltage of the laser2 the repeated sparks provide heat enough to melt

polyethylene. 6uch laser works but degrades easily. 0n order to avoid it we'll make better contact.


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. ut the lower plate from the kitchen foil. &(r either it may be named as 3grownd plate3 or

3common wire3.* 0t si-es should be nearly the same as the upper wings contour has. &Baybe a bit

larger to avoid voltage overstress at edges.* The corners should be rounded. Also leave some lead

for power supply connection. /latten the foil on the laser's base plate.

?. "ut the polyethylene leaf with the upper wings over the bottom foil.


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Take one of the &three* ready electrodes. "ut it above one of the top foils setting the vertical side of

the angle towards the inner side of the foil &towards the gap between wings*2 press it with weights

and align the electrode carefully along the edge of the gap between wings.


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on't bother now about careful aligning of this electrode. 0t will be done at the stage of laser

tuning. The electrodes should be placed as shown on the picture.

Note that the right &on the photo* electrode forms a3wall3 aligned to a side of the gap between top

wings. And the left electrode forms a 3blade3 turned towards the wall. The blade is set at C5 mm

above the dielectric with a help of au9iliary aluminium angle.

.


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there. (r even better glue there not the lid itself but that part of the bottle2 where the lid is screwed.

Bake the end of the B? screw to be round. &=all type spark gaps have less discharge length and

thereafter have the less resistance and inductivity. Take a strip of aluminium from a beer can to

make a wide lead. You may even fold the kitchen foil to make multilayer shim. 4idth of the strip

should be not less than 5; mm to provide low resistance and low inductance. Bake holes &>mm in

diameter* in both plastic lid and contact strip. The B? screw will itself make the other work on

threadening these parts2 when You will screw it in.

The assembled spark gap will look like this+

ertainly one could use a more simple discharger+


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1owever the open spark gap cries out too loud. You may feel it enjoyfull at first. =ut later on You

won't like it too. That's why we make not just a simple air laser2 but air laser with muffler.

58.6et the spark gap as so its foot stays on the top wing of the laser2 and its bending tail goes under the

polyethylene and lies on the bottom &ground* foil


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55.Attach laser to high voltage power supply. 0t's suitable to use loads instead of alligator cilps in

order not to damage thin foils. "ut Your high voltage resistor between laser electrodes.

You will obtain this+

6ometimes they use and inductance coil to make contact for the direct current between laser wings.

/or e9ample like this+


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5).arefully set the distance between electrodes at )mm. Deep an eye for not to displace the 3wall3

electrode. As it was noted above it must always be aligned to the edge of the gap between wings.

6et the spark gap to 5 mm sparklength. You may use the ne9t sequence of actions+ screw the bolt

until it touches the metal wall. &0f You don't feel or see this2 You may use a multimeter &having

been set to ohms measurement* to detect fact of touch.* Then unscrew the bolt back by 5..5.; turns.

&0f You use not B? screw or its thread is not standart the number of turns may vary.*

Thats all with assembling. Time to turn the device on and tune it up.

III. Tuning.

The 'mature' lasers usually have mirrors to be aligned. 0t's pity2 but our 3airgun3 has also something to

align. That's the electrodes.

6A/!TY @!B0N!@+ 0f You use a low power unit with a small flyback transformer2 and if it feeds from

5) volts then the probability to die from electrocution is not higher than probability to die by flu. "#T IT

I$ NOT %ERO!(n the other hand if You are using a powerfull source &like microwave oven transformerwith a voltage multiplier*E then every uncarefull approach to high voltage parts # and You're finished. You

don't even need to touch. There can jump a spark and hit deadly.

/or safety reasons 0 recommend You to use a low power voltage supply. @emember that voltage itself does

not kill. The electic current kills .

Then attach laser to voltage supply. $se a ballast resistor to limit the feeding current and repetition rate of

the laser. %ery low power units resistive to shortenings &such as electrostatic machine* may be attached

directly # without a ballast.

The electric scheme of laser is given below in part with comments.

5. 6witch on the laser. &Turn on the high voltage.*

Adjust the gap in discharger for the repetition rate &as You hear it* to be at ;8..588 1-.

&O# 'A& T#RN THE $AR GA $*RE+ ONL& +HEN HIGH ,OLTAGE I$


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T#RNE- O!!!

). 4acth the sparks in the laser gap. $sually it is either absent at all &the electrodes are too far from

one another* or a bunch of sparks concentrates near one of the ends.

To adjust the electrodes You will use the screwdriver with a large dielectric handle. Deep it as a

pendulum2 make soft easy hits to move electrode towards another one.

6parks -one will begin to creep towards the side where You hit.

4hen the sparks will become spread almost uniformly along the electrodes and when they will


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coe9ist with uniform purple glowing2 it now abot to lase. Take a fluorescent paper # visuali-er and

place it near one of laser's ends. 0t's unpredictable what end will emerge the ray for the first time.

4hen laser works correctly one should see uniform purple glowing in the laser gap along with

rather weak sparking2 also uniformly distributed over the electrodes.

0f the glowing does not want to appear &You see sparks only* 0t means that the &laser* gap is either

too narrow &less than 8.; mm* or too wide &over ) mm*. 0f the purple glow still does not want to

show itself &at any gap widthes*2 it meands that the electrodes are too dirty or scratched. (ne

should discard such electrodes.

4hen the laser gap glows correctly place the visuali-er paper opposite one and another laser ends.6urely You'll find the laser spot. $sually it has a form of small bright point in the place2 where a

shadow of laser electrodes falls onto the paper.

4hen laser spot is found2 tune the laser to ma9imum output using very tender hits to electrodes.

The spot will grow in area and brightness. on't forget to watch the laser spot at both ends of the

laser. 6ometimes the spot may 3creep3 to another side during tuning process. 0f the spot refuses to

appear2 try to decrease the laser gap &keep an eye for not to kill the purple glow* and increase

voltage &by increasing the sparklength in the spark gap*.

%oltage increasement should be done %!@Y gradually. The laser operates near the breakdown

threshold of the polyethylene film. 0n case of failure You will need to remake the wings of laser.

$*RE+ THE $AR GA ONL& +HEN HIGH ,OLTAGE I$ T#RNE- O!!!

:. 4ell tuned laser gives bright fluorescent spot C5 mm si-ed on a paper near the laser. The spot

should remain clearly visible when having si-es )9; cm &; meters apart from laser* even in not

darkened room

0t is a pain to photo the woking laser2 because it does not light most of time. 0t flashes only ;8#588

times per second. The chance it burst e9actly when camera shots is almost -ero. And 0've got no

laser#to#camera synchroni-ing circuit yet. Therefore 0 use the video mode and salvage frames fromthe movie. 0t defines lower resolution and lower quality2 sorry about this.


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I,. $ilencer.

0n tuning process You have probably already noted that laser sounds loudly. This sound is enough to

summon Your neighbourers if You live in multi#quarter house. !nclosure of the spark gap almost halves

the sound but not eliminates it.

The discharge in the laser gap is noisy itself.

0n order to gain some more time for laser operation without attracting ill attention of surrounders we

should make a kind of muffler for our laser airgun.Take some sponge material2 felt2 polyfoam or any other sound insulation dielectric substance.

Bake a cover for the main discharge gap. 0f the material is thin # use several layers &not less than a

centimeter total*.

arefully &in order for not to break the alignment* put the cover above the electrodes and press it &the

cover* by loads.

0f the tuning remains unchanged2 the silenced laser shines almost as brightly as it did without a muffler.

=ut less noisy.


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$sually the silenced laser does not become suffocated. 1owever if Your laser shows power decrease # try

to use less dense material for the cover.

Thats all.


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The first one represents wings of laser as capacitors and the other one # in form of delay lines. The

first scheme describes low frequency behaviour of laser. The second one tends to describe high

frequency characteristics.

/or the laser to be optimal it is needed that @FGG@52 then wings of laser will be equally charged.

0t is also needed that @5)GG5ns. 0t is easily obtainable when @5 is several tens...hundreeds ofohms. 6ince that even at high repetition rates the resistor dissipates not much of heat so the real

nececcity to replace it with induction coil is only aestethic intentions.

@> regulates rep rate &at least in theory* frep+ @FH5,&frep&5I)**.

4hen foils are 589)8 cm and polyethylene is 8.5 mm thick 5I)H?888 pf.

@F needs to be 5.) Begaohms for 588 1- repetition rate. &0n the reduction to practice it usually has

lesser values2 due to power supply internal resistance2 due to different kinds of leakages and so on.*

The repetition rate does also strongly depend to the ratio of power supply voltage to the spark gap

breakdown voltage. 0f they are nearly equal the rep rate is low even with small ballast resistor.

The spark gap should have lowest possible resistance when switched on2 high speed and good

stability. All those properties &e9cept maybe stability* are obtainable when the spark has lowes

possible length. Thus the discharger should be designed as ball#to#ball or ball#to#plane. 6harp edges

and pins should be avoided.

oncerning the high frequency operation of the scheme2 there ia a lot of misunderstanding in

articles and internet posts. Afew ones say that the laser ha =lumleign like circuit and transmission

lines begin to form waves when the spark gap fires. (thers say that it works like


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be usefull. 0t is due to the fact that at higher frequences the 'skin layer' becomes so thin2 and the

resistance of wirings becomes so high2 that 3


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The seen by eye divergency is slightly less than 8.85 &:.;95 cm spot at 7.; meters*. Not so bad for

the superradiant one.

0f You need to light up far2 You can use a collimator lense2 thanks godness2 it appears that usual

glass e9ellently transmits the $% from the laser. &Jood news+ You don't need silica*

=y means of the electrodes alignment one can get the laser to radiate only towards 3forward3 side2

or 3backwards3 or either equally to both sides. 1owever the laser has a 3preferrable3 direction.

4hen the electrodes are aligned for ma9imum output in that direction the output is considerably

higher than in case when You 'force' laser to radiate into the opposite direction. Bost lasers have

3face3 at that side2 where the driving spark gap is placed. 6ome 'e9traordinary' samples howeverprefer to lase in the opposite direction. The 'anomaly' is probably caused by non uniformities of

dielectric and foils layout.

;. The electrodes.


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1owever the beam becomes even brighter if You add lil wings &C: cm wide each*. The electrodesare+ the left one on the picture is made of alumimium floor molding with a sharpened edge2 the

right one is made of the usual aluminium agle as we did before. The riht electrode is being put

directly onto dielectric without putting anything to rise it up. The discharge is skew between edges

of the electrodes. The floor molding should be sanded &usually it comes in anodi-ed state* and its

working edge should be polishedM the second electrode utili-es the aluminium angle 'as is' in the

shop saled condition.

0t is interesting that when trying to apply wings to that electrodes configuration2 one can see that

the output power does not increase. 0t even starts to drop whwn wings are wide enough &C)8 cm

span*. Taking into account the enegry stored in the under#the#electrode capacity one may estimate

laser efficiency at C5. 0t is very well for nitrogen lasers. 0n addition such a laser is less noisy and

better suits for high repetition rates.0t also is very suitable for making a stable design. 0t may look like this+

&for this e9ample it is fed by a #disc electrostatic machine*


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Jenerally it seems that laser likes sharp edged electrodes. And it is very e9pected since the !,p

ratio is below optimum.

>. !lectrodes refurbishing.

The electrodes having been broken during making &scratched by filer*2 the anodi-ed ones2 the ones

burned by sparks2 and simply old dirty ones may be brought to life by grinding on a fine grit

sandpaper with further polishing with a polishing paste on a felt disc &usig a drill # not by hands ofcourse*. 1owever such a rude polishing gives not uniform discharge along the electrodes and the

output will be weaker. (ne may process the electrodes better # by fine milling with following

grinding and polishing on a flat glass plate... =ut it is not for home e9periments.

. The gap between the wings.

The principles of this laser are far more complicated than one might thought. "articularly it uses the

so called 'sliding' discharge to preioni-e the main laser volume. &And the e9periments with low

pressure nitrogen lasers prove that profoundly.*

/or the laser to operate smoothly this sliging discharge is needed to be strong enough to provide

sufficient amount of $% radiation to peioni-e the main gap. =ut it should be kept weak enough for

not to pass the sufficient part of pumping electric current. 4ith the laser described here it can be

achieved when the gap between wings is about : mm. 4hen scaling the laser &especially whenchanging feeding voltage* one should try to optimi-e the width of this gap too.

?. 6caling.

The laser appears to be workable with length of electrodes in range between C cm and C:8 cm.

6erious efforts directed to build up the travelling wave mode of operation allow to succeed in

building 5 meter long laser. &The required electrode alignment angle gives inter electrode spacing at

about C:..7 mm near the output end. 0n its order this requires feed voltages over ); kv. You will

need strong dielectric and face severe problems with avoiding flashovers.* The output power rises

almost linearly with length of the laser and with its supply voltage.

The wings span should be at least enough to provide the energy2 necessary for the laser to reach

threshold. &$sually it is C: cm per wing2 but as it was mentioned above some lasers can operate

without wings at all.* There also is a saturation when the wings span is increased. 4hen it is overC58cm per wing the discharge time becomes slow enough to feed the laser and the output stops to

increase. 4hen it is over C)8cm per wing You can hit the area of thermal instability of the

volumetic discharge. 0n this case laser wil tend to show sparks and its output will decrease with

further wings enlargement.


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ielectric thickness. The laser requires a certain energy to be put in gas to become superradiant.

The energy stores in the capacitors can be estimated as $O),)2 where # its capacity2 and $ #

supply voltage. The capacity is reversely proportional to the dielectric thickness. 6o when varying

the thickness adjust the supply voltage accordingly &proprtional to the square root of the thickness

change. Deep in mind however2 that too low voltage would not allow You to obtain the volumetic

discharge in a reasonably wide gaps. &And too narrow gaps will make laser inoperational due to

diffraction losses.* (n the other hand the laser feels friendly to voltage increasement. 0ts output

rises greatly. And even small lasers when being fed by :8I kv2 produce output comparable to one

from low pressure nitrogen lasers. 6o feel free to rise voltage and dielectric thickness until You canhold it up &keep it from breakdowns and flashovers*. (ne should remember that the obtainable

width of the volumetic discharge rises slowly with voltage increasement. 6o don't e9pect > mm

spacing at :8 kv. &0 only succeeded with 7 mm at 7; kv. 1owever the beam was fantasticP*

. ommercial capacitors.

0ts sad2 but A


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55.Applications.

The laser is interesting for+

Alignment of long thin things. The $% diffraction divergency is a half of one for the red

&1e#Ne* rays. espite the low quality of its radiation2 one can always use a small aperture to

'clean up' the beam. !ven then its intensity is enough for the alignment purposes.

/or the pinpoint curing of photo sensitive glues. /or the dye lasers pumping. &0ndeed it's one of the most attractive applications. And the dye

lasers are the most entertaining ones.*

/or homemade spectrograph claibration &including ones made of #disc and photo

camera* The :: nm line of this laser is a good &and sometimes crucial* addition to the 1e#

Ne line2 obtainable at home.

There are some messages that the natural width of the line2 this laser operates at2 is narrow

enough to provide up to : cm of coherence length. 6o this laser may be of some holographic

use.

And just for fun.

The laser is not interesting for rilling2 scribing and other material processing &too low output*

eng n2tealaser

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