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Welcome to another Lightblade learning
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. Today we’re going to give you a bit
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of a look at the anatomy of this vital
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part of the machine which is the laser
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tube itself now it’s quite important that
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you understand how this basically works
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because you need to look after it, now you haven’t
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got to do anything to it other than treat
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it well but why do you have to treat it
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well if you understand how the tube works
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you will understand how you can abuse it
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and that’s the last thing I want you to
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do because if you abuse that tube it’s going
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to cost you several hundred pounds to
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replace it and it won’t be under
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warranty
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you might be interested in a couple of
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lights that I’ve got stuck in here at
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the moment
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these are just what i call my
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winterizing kit tacked down here i have
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a small temperature controller or a
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temperature-controlled relay which is
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looking at the air temperature inside
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the Machine this workshop that I mean is
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totally unheated and during the winter
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months
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I’m fearful that the water that’s inside
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this tube may freeze so I’ve taken
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special precautions of adding a hundred
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watts of heating into this machine and a
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hundred watts of heating down there to
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the chili unit as well so that during
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the cold winter months as a completely
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separate supply this machine will heat
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up water in this tube and circulated
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through the pumping so there is
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absolutely no chance of anything will
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ever fries okay now this tube is
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actually made up of three glass tubes
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the first actor tube which is what I’m
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tapping at the moment is the container
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for the guests
Transcript For Laser Tube and Hazards (Cont…)
02:00
that’s a gas reservoir now inside there
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you’ll see there is another tube and if
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you look carefully you can see along the
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top of that tube some little air bubbles
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well that’s the water jacket that sits
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inside this altitude here and then if
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you look a little bit closer you may
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find through the reflections that there
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is a third inner tube you can see
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now the third inner tube is the
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containment tube for the ionized gas
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ok they don’t this end of the tube we’ve
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got this red cable very thick red cable
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which is capable of taking I think about
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40,000 volts but it’s a 25,000 volts
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cable this one and this cable goes to
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that blue electrode there which is the
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anode but when this too was working the
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guests tends to flow towards this
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positive electrode it returns and comes
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back
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can you see that pipe there that’s going
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across the top you can see the spiral
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tube here now that basically is spinning
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the gas round and then it deposits it
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just underneath this label here
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the gas is spinning around at that point
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in time and it travels back along the
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reservoir to the other end of the tube
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so there’s always a circulating flow of
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gas through this tube
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ok now I talked about a gas reservoir
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this out to to being a gas reservoir
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trace gases like hydrogen and then on
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and one or two other mixes maybe in
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there as well to help certain aspects of
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the tube but these are the Prince of
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gases you need to imagine operating
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within this tube the nitrogen is
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actually the most important guess he
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might say what is a carbon dioxide laser
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surely the carbon dioxide is the
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important gasps well yes it is but let
Transcript For Laser Tube and Hazards (Cont…)
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me explain that the nitrogen is
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absolutely fundamental to the way in
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which this tube operates now I’m not
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going to turn the tube on at the moment
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but when we turn the tube on you will
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notice it there as I’ve shown you in the
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first introduction you will notice that
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is a pink glow along the tube now that
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pink glow is actually ionized nitrogen
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all of these gases are non-conductors
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naturally even as it’s sitting there
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this tube is being bombarded by cosmic
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rays from the Sun I know it’s nighttime
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but they pass through the earth they
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pass through anything and everything and
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there will be some cosmic rays which
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will actually be colliding with some of
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the nitrogen atoms that are in that tube
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there might only be one or two or three
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that’s enough to start a chain reaction
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off at any point in time that we wish to
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turn the laser on now to get current
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flow you need basically some free
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electrons or electrons that are knocked
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out of their orbital shells
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let’s not get too involved with the
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atomic physics because i’m certainly not
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a physicist
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so what’s going to happen is to get this
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to kicked off into action at the end of
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the tube over there
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we’re going to put 25,000 volts DC and
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that means that they’re 25,000 volts
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difference between that end of the tube
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and this end of the tube here which is
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the cathode now that means that any
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negative electron which is floating
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around in that tube and as I said there
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will be some floating around in there
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just because of the natural action of
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cosmic rays those free electrons will
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immediately start flying a very high
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rate of knots along the tube towards
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that electrode at the other end there
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and in doing so it’s like a fat man at
Transcript For Laser Tube and Hazards (Cont…)
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the back of the room rushing to the
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front of the room to get these free
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hamburger as he goes he’s going to knock
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people out of the way he doesn’t care
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and that’s exactly what happens to these
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free electrons they’re going to rush
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towards the end of the tube there and in
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doing so they’re going to not some more
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electrons off of other nitrogen atoms
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and what that’s going to do is cause a
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cascade action which sets the whole
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thing in motion and we can start to get
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this process called ionization now when
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the gas starts to ionize which is
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basically lightning the gas changes from
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a nonconductor into a conductor and can
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conduct huge amounts of current we can’t
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afford to let that to happen because the
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two but just pop so built-in
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to the built into the system there’s a
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control system in the power supply which
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limits the current to a very small value
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so we get very small controlled currents
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running through this very conductive
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gasps okay so we’ve got nitrogen which
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is no a conductor but it’s more than a
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conductor because it’s no an ionized gas
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and you don’t get ionized gas for free
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it requires energy and energy produces
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heat no lightning sets fire to trees
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what we’ve got is controlled lightning
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effectively i’m exaggerating slightly
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but we’ve got controlled lightning in
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that tube there the ionized gas can get
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up to thousands of degrees C to try and
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control that temperature what we’ve got
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is two things the first thing we’ve got
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is helium and we have huge amounts of it
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in that mixture helium is a very very
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good conductor of heat so the helium
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will carry the heat out to this water
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jacket and we’ve got water flow that
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passes through the system to take the
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heat away so that’s where the water
Transcript For Laser Tube and Hazards (Cont…)
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jacket comes into play so the helium is
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very important the nitrogen is very
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important and we haven’t mentioned the
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co2 yet let’s just go back to the
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nitrogen for a second because I said it
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was the most important gas without the
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nitrogen ionizing we don’t get anything
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happening the nitrogen atoms are in fact
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being that let’s imagine excited my hand
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is moving to imply excitement our height
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and when this is running at a controlled
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current let’s just say for milliamps we
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got controlled excitement but as we
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increase the current in that tube the
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excitement level of the nitrogen starts
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going up and so can she go to get higher
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and higher energy levels and vibration
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levels within the nitrogen itself and we
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can control the level of that excitement
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with the current flow that we put
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through the tube
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I can he get your patient yes i know i
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don’t hear about night
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you don’t want to know where the carbon
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dioxide comes in and I like to imagine
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the carbon dioxide is a very lazy gas it
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doesn’t really want to do much but
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unfortunately the nitrogen doesn’t want
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to work that way
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it’s getting very very excited and as it
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gets excited so from time to time some
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of these nitrogen atoms will collide
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with the carbon dioxide molecule and as
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it hits the carbon dioxide molecule it
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will impart some of its energy to the
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carbon dioxide and so the carbon dioxide
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will all of a sudden have to be raised
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up to a slightly higher energy level
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yeah it doesn’t want to be there it’s
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naturally lazy and so consequently what
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will happen is once it gets excited
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it says don’t be here and it finds any
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and every opportunity to get rid of its
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extra energy and go back to sleep again
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now it is that process of getting rid of
Transcript For Laser Tube and Hazards (Cont…)
10:00
the energy and it gets rid of the energy
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in the form of light photons of light
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that process of giving off its energy is
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basically the emission of photons to
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give off energy three other parts of
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this word laser and it’s called light
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amplification by stimulated emission of
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radiation well the stimulated bit is the
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nitrogen raising the level the emission
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is when it drops back down again and it
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gives off this radiation which is light
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in the form of 10.6 micron radiation
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we’ve got this bit at the frontier
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called light amplification so how’s that
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been working hiding behind this water
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jacket here right on the end of the tube
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we have a mirror it’s a mirror that is
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perfectly aligned with another mirror
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right at the other end
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now this is a hundred percent reflecting
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mirror not this end of the tube
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we’ve got a brass water jacket but
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behind that brass water jacket just here
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is another mirror that this mirror is
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not quite the same as the mirror the
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other end this one is a partially
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reflecting mirror
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I don’t know exactly what degree of
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partially it may will be 70 it may will
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be eighty percent reflecting but that
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means that twenty percent of the energy
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that hits this will come out of here and
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will be the laser beam that we are going
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to use we talked about the fact that the
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co2 gets raised to a higher energy level
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and then wants to get back down to its
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lazy level now it only needs one of the
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co2 molecules to lose its energy and
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emit a photon and that photon will start
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traveling along this tube in a direction
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and will automatically persuade another
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photon to come enjoy it
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ye it will trigger a chain reaction and
Transcript For Laser Tube and Hazards (Cont…)
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that chain reaction will trigger more
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and more photons to join in and travel
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in this direction all those photons will
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start rapping along the tube and as they
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travel they will gather more and more
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photons and all traveling in that
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direction so they get to that mirror at
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the end there and then they start all
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coming back now there’s a lot more
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coming back then went down so those
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coming back by this time of course we
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should have more and more collisions
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with nitrogen atoms which has promoted
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more and more co2 Adams up to high
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levels so as they come back they will
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trigger more and more photon release and
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you will get a bulk of photons that will
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gradually be amplified every time they
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bounce back and forward off this mirror
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so we get this amplification of light
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going backwards and forwards in this
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tube it’s nothing to do with the light
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that you see coming out of the center
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tube which is the pink light from the
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ionized nitrogen is completely separate
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from this other invisible light which is
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bouncing backwards and forwards inside
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this tube so there’s several strange
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processes going on here if you remember
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this conversation beginning I said to
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you that the current is being controlled
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by the power supply and you in fact are
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controlling the power supply through the
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percentage power that you input through
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the keyboard now if you put to higher
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percentage power you will
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more character flow through that tube
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what’s actually going to happen is the
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nitrogen is no longer going to do that
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it’s going to do this it’s going to go
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absolutely bonkers the more current you
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put through it the harder it vibrates
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the more energy it has now you get to a
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certain critical point and that is the
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limit specified by the manufacturer of
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that tube and their energy level in the
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nitrogen is so high that it won’t just
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encourage the carbon dioxide to go up
Transcript For Laser Tube and Hazards (Cont…)
14:02
and not be lazy and have a little bit of
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extra energy it will have so much energy
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that when it collides with the carbon
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dioxide molecule it’ll break it down
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into carbon monoxide and a free oxygen
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etem no carbon monoxide is not a lacing
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gas oxygen is not a lacing guess so
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now because of your enthusiastic use of
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hundred percent power ninety percent
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power at the keyboard you’re actually
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destroying the tube itself the gases
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inside the tube by overdriving the
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nitrogen and making it far too excited
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so that actually has killer powers I
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don’t exaggerate that too much because
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built into the system there is probably
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some hydrogen is probably in that
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particular to a catalyst which is gold
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which actually partially reunites these
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two back together to make that so there
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is a hailing process that’s built into
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some of the better quality tubes and
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that helps to promote a longer life tube
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the principle of a tube dying over a
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period of time is basically this one
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because even when you’re running the
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tube under manufacturers specified
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control limits there is a very small
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amount of this association as they call
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it taking place both gold and the
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additional gas which is generally hiker
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water vapor has got a catalytic effect
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of recombining these two back to carbon
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dioxide but
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drive it too hard for too long and you
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will permanently destroy the carbon
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dioxide and what will happen is the
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oxygen will tend to collect on the
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cathode in there and change the color of
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cathode and so it will be obvious that
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you’ve been a naughty boy and you have
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destroyed your tube x over driving it so
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I can’t say any more than that now you
Transcript For Laser Tube and Hazards (Cont…)
16:01
know how the Tool Works and why you can
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overdrive the tube you can make the
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mechanism work harder than it should do
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there’s a balance point that you must go
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beyond I have to know that this tube is
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made by FR laser and it’s a 1200 CL so
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we can go to the website and we can find
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out what current specification they
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recommend for this tube now my guess
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it’s somewhere in the region of 20 to 25
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milli amps one of the quickest ways of
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finding out the relationship between
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this 22 milliamps and the amount of
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power that we’re allowed to use is to
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probably just use the pulse button we
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can set the maximum power here to some
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value and i will show you how to do that
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shortly and we can check whether or not
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the power that’s on here equals
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twenty-two milliamps so it may be that
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will only be able to put sixty percent
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power into here and we should get 22
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million amps now what that means is
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you’ve already reached the limit at
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sixty percent power at no time can you
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ever program into this machine more than
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sixty percent power
