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nbk2000
June 9th, 2002, 09:21 AM
As we all know, making a decent det-cord is a pain in the ass. And detcord is so useful (and neccessary) for setting off multiple charges simultaneously.

However, for us pyros, electric is the most convenient means of doing so. But this is also a hazard. You must worry about electrical or radio energy possibly setting off your charges prematurely. This isn't a common risk, but it all depends on your targ...uh...TEST!...yeah, test, that's it...area. <img border="0" title="" alt="[Wink]" src="wink.gif" />

Knowing that there are light sensitive primaries (NCl3, for instance), I had the idea of detonators that use such light sensitive primaries with a fiber-optic cable that carries a pulse of high UV light from a (device of unspecified nature) that would initiate the primary.

Advantages of FO over electrical wiring is no metal content to be detected by metal detectors, immune to EMP/static/RF, very lightweight, can be as thin as a human hair and thus invisible to detection (though there may be technical constraints on the smallest feasible diameter).

I'm thinking the "detonator" that would be used to initiate the light-caps would be either a flash type device using a magnesium photoflash, a laser, or an electronic flash. Something that would put out a sudden and intense pulse of UV rich light to "shock" the fragile bonds of a light sensitive primary, causing it to explode.

Anyways, comments and criticism wanted.

imported_reodor_felgen
June 9th, 2002, 10:07 AM
All I know is that fiber optic cabels are really expensive and that NCl3 is way too sensetive in my experiense, maybe i had too many contaminents in it or something. Any other light sensetive explosives? I know theese are, but they are also very sensetive to friction, shock and heat:

Fluminating silver (NAg3 or NHAg2)
Silver fulminate (AgONC)
Diaminesilver (II) Chlorate

But if one found a reliable light sensetive explosive, this would be a very good idea! I don't know, maybe you could use NCl3?

Fl4PP4W0k
June 9th, 2002, 10:10 AM
The most complicated (and most expensive) method would be to set up a simple light activated relay circuit. Using, for instance, either an LDR or phototransistor hooked to a relay and a 6v battery. A laserpointer or LED would be at the opposing end of the optic fiber, and trigger whenever.

Also, are highly light sensitive explosive compound only sensitive to UV light?
If they are sensitive to around 650\700 nm, I know a VERY cheap source of 10mw 650nm lasers...

Otherwise, the UV Light used inside those PCB UV Exposure boxes is pretty potent. If you were to maybe use an LED of the appropriate wavelength, or somehow focus those tubes output, Im sure that could be sent through the cabling.

l8r,
rob

xoo1246
June 9th, 2002, 11:20 AM
Great idea NBK, good initiative.
If your laser is powerfull enough, you could probably initate most primaries. Would be great to have data on diffrent primaries.
Another use could be to set of shaped charges from many angles, making it more effective. I belive I read a patent on that.
Here are some laser modules sold by a swedish company:
<a href="http://www.algonet.se/~laseropt/dilas/modules.html" target="_blank">http://www.algonet.se/~laseropt/dilas/modules.html</a>
I checked ELFA for fiber optic cable and it cost around 1-1.7$/m if you order above 100 meters.

<small>[ June 09, 2002, 10:51 AM: Message edited by: xoo1246 ]</small>

Fl4PP4W0k
June 9th, 2002, 11:25 AM
lol... UV lasers = $$$

Basically, the lower on the spectrum you go, the more cash it costs for a laser\LED :(

I can get an ENTIRE 650nm 10mw rig for less than $50US :D
How does THAT sound.
In comparison, a UV laser with a wavelength of around 385nm or so would cost at LEAST $500US+ <img border="0" title="" alt="[Eek!]" src="eek.gif" />

xoo1246
June 9th, 2002, 11:54 AM
You are right, I did some research and they are really expensive.

A-BOMB
June 9th, 2002, 01:06 PM
If you had a strong enoth laser you might not even need the fiber optics you just aim the laser beam throught all the detonators. And did anyone else notice that they were comparing the size of those laser modules to a .22long rifle shell.

PYRO500
June 9th, 2002, 04:21 PM
I don't know about using NCl3 that kind of has a bad wrap for a good reason. In my opinion fiberoptics would better be used in a vibration detector proximity circuit, in witch the fiber optic cable is wound around 4 bolts in a spiral at one end it is connected to a stable led. On the other end a photo detector. Any slight vibration can be interpreted as a clicking noise on an audio amplifier and when the clicking gets loud enough (such as a near person or a slaming door) the voltage rises high enough to reverse bias a zener diode and trip a one shot triggering circuit. It may be a bit complicated but for what it acomplises it blows away any design i've seen.

xoo1246
June 9th, 2002, 05:21 PM
Sure, It's a good idea, but it doesn't help you much if you have to detonate several charges at the same time .
Here is a patent:
5,148,748 (Laser detonated blasting cap, still requires a powerfull laser)
5,052,011 (Explosively pumped laser light, found it interesting though not directly related)
A question, what happens if you send a too high voltage into a laser module that has only a say 10mW effect. I don't know how they are constructed, are there a diode? Would it give of a laser flash before it's beeing destroyed?
Edit:
4,862,804 (another patent discussing a shaped charge initated by several "Laser Initiated Microdetonator")
Damn it, I wish those 5W laser modules weren't that expensive. <img border="0" title="" alt="[Wink]" src="wink.gif" />

<small>[ June 09, 2002, 04:29 PM: Message edited by: xoo1246 ]</small>

nbk2000
June 9th, 2002, 09:03 PM
Guys...no electronics. That'd defeat the whole purpose.

I'm thinking a flashpowder charge with an additive for extra UV "oomph". This is connected to the FO cables which go the to LS (light sensitive) detonators. When it's set off, the light goes through the cables to set them off.

The beauty of this is that the charges will get initiated at the same instant, regardless of cable length, because it's (litteraly) light speed fast. Unlike detcord that has to be trimmed to exact lengths for synchronizing charges.

NCl3 may not be the ideal material, but it does have the advantage of being easily made by the home hobbyist. And it's sensitive to any bright light, which makes it suitable for use in this concept. I'm sure a thourough literature search could come up with any number of more stable, but still LS explosive compuounds.

There's UV laserlaser diodes available for &lt;$200. Regualer UV LEDs are &lt;$20 each. But I don't know if milliwatt range energy levels would do the trick. I mean, full daylight is equivalant to 400 watts/meter I believe. But a magnesium pyro flash compound with a condenser lens should be easily bright enough to do the trick.

Also, FO cable can be just a few cents a foot if you use low grade plastic fiber, like that used for those novelty flashlights with the wavy FO brush on the end. Remember, you're not trying to send high-speed data streams over the shit, just a pulse of intense light. It's very fault tolerant. :D

Microtek
June 10th, 2002, 05:35 AM
Many silver primaries such as silver azide, -acetylide and double salts are degraded by daylight. Perhaps a sufficiently powerful UV pulse would be able to initiate these rather stable primaries
( at least in my experience they are quite stable; I know some say that the acetylide is very shock sensitive ).

Flake2m
June 11th, 2002, 12:18 PM
This will be giving all of those potenial terrorists out there an idea.
A terrorist could have give a present to someone earlier on in the day (teddy bear in this example), the person ends up putting the teddy bear near a window. Unkown to them, the teddy bear contains some NCl3 in its eyes and HE is contained in its stuffing. Later on that night, a terrorist mounts a scope on a powerful UV laser. He firstly looks for the teddy bear and then he aims for the eye of the teddy and switchs on the laser from a distance of 75m+.The office containing the teddy is destroyed and the terrorist gets away with this act.

Fibre optic cables would work especially since you could put your primary at one end of some severed fibre optic cable from an office and then send the signal from within the office with a laser a few mins later.

xoo1246
June 11th, 2002, 01:47 PM
That's what I call over-complicating stuff. <img border="0" title="" alt="[Wink]" src="wink.gif" />
The person who recieves the present gives it to his/her daugther/son who dangs the teddy in the wall a couple of times. The kid is reduced to small meat chunks.
What would you do if you got a teddy bear from a un-known person?
I thought terrorism was to kill people to get your will through. Nowdays, the word can be applied in any sentence.

<small>[ June 11, 2002, 12:50 PM: Message edited by: xoo1246 ]</small>

Tyler_Durden
June 11th, 2002, 10:13 PM
Flake... that's a silly idea... there are better ways to accomplish such a task than the one you described. Timer, remote detonation, etc etc.

Also, terrorism doesn't necessarily have to be killing people, it is more essentially instilling terror. Sure, the 'terrorists' won't kill every single American, but instilling the fear of being a victim into as many people as possible is what they are striving for. And you are correct that terrorism supports a political cause.

Anyway, let's try to get back on subject...

I am surprised fiber optic cable is that expensive. I have a little room decoration that is a light thing.... it is a base with hundreds of (supposedly) fiber optic wires flowering out of it. You all may have seen similar things. It probably has about 10 meters of this wiring, and the whole thing only cost a couple bucks. What's the deal? is it not really fiber optic stuff? Or is it just because they are very thin wires? It doesn't seem to add up to me.

megalomania
June 12th, 2002, 01:43 AM
I think those are just translucent plastic fibres on the lights. Check out the new fibre optic lighting systems they have for outside your home, Home Depot has a nice setup. The cable is very expensive, over $2.00 a foot IIRC. The cable is not sold by the foot, but in lengths of 50,75, and 100 feet. The price tag is of course a shocker. Jeez, for that much you could hire an electrician to install an electric one and still save. They sell these to people who don't want to bother installing an electric one, of course fibre optics are much cooler... but I digress.

PYRO500
June 12th, 2002, 02:37 AM
Those fiber optic lamps are indeed true fiber optic conduits although their un jacketed and they aren't very efficitent (not as transparent as pro data cable) but there cheap and work fine for display purposes they are usually made out of plastic although you can get better glass fibers that are alike these. The professional fiber optic cables that aree used in high speed data link or high quality digital A/Vequipment are actually a special glass fiber coated in plastic for protecton.

Flake2m
June 13th, 2002, 10:56 AM
My point with the hypothetical terrorist attack is;

A terrorist could detonate an explosive with out using a fuse or a detonator device that is actually attached to the explosive itself. A terrorist could make one of these devices, and not use metal or anything that would raise suspection to security. All the terrorist(s) need is a transparent area that is large enough to be targeted with a UV laser. This is what makes the idea scary.

<small>[ June 13, 2002, 10:00 AM: Message edited by: Flake2m ]</small>

Tyler_Durden
June 13th, 2002, 10:16 PM
Why is that any more scary than any other of a million possible terroristic scenarios?

ie a bomb in any public place

PYRO500
June 13th, 2002, 10:44 PM
In general I find "bombs" only scare women and children the most what scares the sheeple isdamage and anything that contains the words "chem warfare" or anything biolgical or genetic for example "biological warfare" or "genetic engineering" terrifys them.

Magas
June 17th, 2002, 09:12 AM
Guys Guys Guys

Nonel initiation systems have been around for years. They use a thin plastic Spagetti pvc internally coated. You use a Nonel initiator which is like a ordinary staters cap the flash then travel up the tube to the Nonel dets. Its made by Nobel & various other manufacturers. Been using it for years relatively cheap impervious to all forms of external det sources. comes in a wide variety of trunk line delays & connectors.

PYRO500
June 17th, 2002, 06:49 PM
I am not sure what you are talking about but I think you are referring to shock tube initiation systems where you have a thin plastic tube and you fire a device like a blank through it, this is a little bit more complicated than fiber optic detonation and requires explosives at both ends.

Bignutsami
June 18th, 2002, 03:17 AM
When ive seen it nonels (as in non-electric)uses a shotshell primer for initiation, whether its more complicated then a high power laser, sensitive primaries and $100's of dollars worth of cable, i dought it.

Of course wouldnt think it will be availabe to everyone.. and making detcord itself would probably be easier to make then nonels. Spose thats the point in looking for alternatives.

nbk2000
June 18th, 2002, 08:40 AM
There's another idea I've been kicking around for ages...an X-ray sensitive detonator.

Certain materials glow when exposed to X-ray radiation. Thus, such a material inside of a detonator loaded with light sensitive primaries could be used as a simple boobytrap initiator that would explode when an EOD tech X-rays the bomb or when it's passed through a security scanner.

Now, since I don't know how intense the X-ray machines at airports and such are, I don't know if there's any materials sensitive enough to build such a detonator, but it'd be worth looking into.

The whole point of this thread is for possible alternatives to shock-tube and det-cord initiation trains. What's impractical for industry may be suitable for the hobbyist.

That and just to know if it can be done. Knowledge just for the sake of knowing. :)

But if you have a way to duplicate a Nonel system, please post it.

Magas
June 19th, 2002, 11:38 AM
I think that is what its called in the US. Shocktube / Nonel does use a shotgun primer for initiation. And yes it does cost a few hundred dollars for a blast line. But far less than the cost of the lazer to initiate an explosive or even the fibre optic cable to detonate. Nonel is very cost effective for a controlled blast environment especially with permitted class explosives. I thought the thread was alternatives to electric detonation.

PYRO500
June 19th, 2002, 06:16 PM
I have had the idea of making a "trigger" or "gotcha" as the bomb squad calls them that can detect x-rays and detonate when they are present. The good thing about x-rays is that they fall under the catagory of ionizing radiation meaning that they are more than EM waves they can strip electrons from atoms making detection much simpler. in fact any giger counter or other radiation detector that can pick up gamma rays can also pick up x-rays this includes scintillator devices and other semiconductors in fact some npn transistors can detect radiation if you take the tops off of their metal can but are also effected by light connecting one to a audio amp is proof enough. you could concevably design a device that wouldn't bee to difficult to construct or use much power but it would detonate when they scanned it. I found this page witch explains their detection better than I can. <a href="http://www.chem.vt.edu/chem-ed/optics/detector/xray.html" target="_blank">http://www.chem.vt.edu/chem-ed/optics/detector/xray.html</a>

pyromaniac_guy
June 20th, 2002, 06:26 PM
NBK...
the problem you are going to have with this idea is that most otical fiber, especially the kind you are going to find cheap at optical surplus dealers and or ebay, is that they are not intended to propagate uv light. most 'generic' fiber, even sillica fiber(most transmissive to uv) is going to have a very steep cut off starting at about 500nm... losses may be as high a 1 db per meter at 400 nm.... there are specialty fibers that have excellent transmission caracteristics in the uv, all the way down into the low 300nm range, but that stuff is very expensive... 10+ $$ per foot, and probably a few thousand bucks per km.... I think what would be better would be to have a deflagerant that sets off a primary explosive... ordiniary multimode telecommunication fiber can carry the light impulse then, however the 'initiator' ie the laser diode source would be rather expensive... I could put together a few watt diode coupled laser for a few hundred bucks, or one could be had off ebay, if you get lucky, for a fair bit less... telcom grade fiber will have a transmission loss on the order of a few db per km at 800nm (very common wavelength for a high power diode laser). a deflagerant could be set initiated after a few km worth of optical fiber....

nbk2000
June 20th, 2002, 11:44 PM
Well, the other way to use FO would be to transmit a light pulse to trigger a photosensitive circuit connected to the device. This setup would be immune to any type of jamming or triangulation, and is impossible to detect, unlike a radio or laser beam.

Obviously, FO detonators would be a highly specialized application, thus I'd assume anyone trying to use it would have a purpose in mind and be willing to pay for the needed equipment.

pyromaniac_guy
June 21st, 2002, 03:21 AM
actually, if you just wanted an initiation method that was not easy to detect, you could use a pulse laser diode operating at 1500nm.. such devices are becomming more and more common and practicle. a band pass filter ont eh reciver and a coded pulse train from the trigger mechanism would make the system fool proof for all intents and purposes... 1500nm cant be seen by regular night vision or silicon based detectors, however it COULD be seen by any near ir thermal imager.. however such equipment is much less 'run of the mill' than normal night vision or ir intensifiers... this way the fiber optic can be disposed of entierly... you your trying to do things covertly having a km of cable running out of your bedroom window probably isnt the way to go :)

PYRO500
June 21st, 2002, 04:39 AM
How about a wide beam pulsed IR laser with a pair of basic stamps programmed for one way data transmission, you could acivate the device from it's long term dormant phase and put it on a timer or such that was programmable by the little laser gun you have in your hand, that way you could program a mission weeks or months (possibly years) that could be adjusted/aborted at any time. such a device could be imbedded in a wall or in a car or anything else it could be concealed into.

pyromaniac_guy
June 21st, 2002, 05:21 AM
it's a rather simple matter to collimate most any laser diode to a few degrees divergance in the fast and slow planes (most laser diodes have output that do not uniformy diverge, ie it might diverge at 10 degrees in one plane, and 40 in the other)... with a few degree beam it would be possible to have a half way decent field of view on the target area so hitting the targets detector would be easy... there are commercially avalible laser diode drivers that accept ttl modulation, so that would be rather straight foward as well... if one were to use a high power pulsed laser source like a pulsed laser diode bar, the range of the device without exotic or bulky optics could be phenominal, maybe even many miles in clear weather, line of site dependant naturally...

PYRO500
June 21st, 2002, 05:54 PM
I was thinking more along the lines of a laser tube that would have a long range even in bad weather.

pyromaniac_guy
June 21st, 2002, 07:14 PM
unfortunatly there really isnt way of doing that... the only way to burn through bad weather is to literally do just that, have a beam of such high intensity it cooks through clouds or rain.... if you are only talking about light rain, then a low power laser diode would still work.. the problem with bad weather is that fog and especially rain scatter the laser beam very effectivly. in dense rain or fog a laser beam will propagate through much less of a distance... reduction of range might be an order of magnitude or more for seriously bad weather...

PYRO500
June 21st, 2002, 10:43 PM
fog and rain do not scatter IR light nearly as much as visable light thus making it a better choice.

pyromaniac_guy
June 22nd, 2002, 12:44 AM
actually, in the near ir, where you would find most commericailly avalible laser diode sources there is plenty of absorption due to water.... thats actually besides the point, what I was reffering to was physical scattering of light by particulas and or water droplets.. next time there is aheavy fog out, take a laser pointer outside and see what a diffrence the scatter makes... you will be able to see the beam much more readily... inorder to see the beam there must be scatter... if light is being scattered there is that much less to reach the target...

PYRO500
June 22nd, 2002, 04:52 AM
I know that, I am talking about a true IR laser tube, a bit further into the spectrum than near infered leds I just managed to get an IR laser module out of a printer witch if I can ever find a power supply will conduct some experements.

pyromaniac_guy
June 22nd, 2002, 04:07 PM
an ir laser diode out of a printer is most likely 780 nm.. the atmospheric 'window' is right around 3 microns... unfortunatly there really arent any convinient sources of laser light at that wavelength.... unless you consider building a chemical laser convinient.... if you were to do that you might as well set your charge off with thermal energy instead of a coded pulse of light :)

TRUTHSEEKER
November 10th, 2003, 12:59 AM
LASER initiation of explosives has been around for a few years now in Aerospace applications. The primary reason for the move to lasers from bridgewires is SAFETY and RELIABILITY.

Some spec listings for explosive materials will list the "LASER Initiation Threshold" in (energy per unit area per unit time - J/cm^2/.250 us (microsecond?). This threshold data is from Robert Weinheimer's personal notes - he is/was the chairman of the International Pyrotechnics Society WAll Chart Commitee (1992).

For example: the "LASER Initiation Threshold" for RDX is 3.1 J/cm^2/.250 us @ 1.64 g/cc (density). This is the lowest threshold that I know of, but I know of a couple of others.

There appears to be a link between the material's "autoignition temperature" and the "LASER initiation threshold", but I do not have the particulars.

LASER initiation is rather inpractical for a solo show, but quite attractive for repeated performances. No bridgewire failures, no sparks to cause premature detonation. Nice and safe.

Tuatara
November 10th, 2003, 03:59 AM
That figure you're quoting is equivalent to 12 megawatts per cm^2! Are you certain of your units?

TRUTHSEEKER
November 10th, 2003, 03:46 PM
That's what the report says. I'll research it further and report back.

I also found this in a report titled:

Methods of protecting electro-explosive devices from the effects of RF radiation and ESD.
AIAA Paper 97-2695 (AIAA Accession number 36042)
Kenneth E. Willis (Quantic Industries, Inc., San Carlos, CA)
AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 33rd, Seattle, WA, July 6-9, 1997

(you can view the first page for free on the web)


Recent developments in diode lasers have achieved
power levels over 1 watt CW. When this optical
energy is delivered through a 100 micron diameter
fiber, the power density at the laser initiator is 100
watts per square millimeter or more; a level that can
reliably initiate many pyrotechnic materials. These
developments have made diode laser ordnance
initiation systems practical and cost effective.

The laser initiator and its connecting fiber optic
cable are practically immune to the effects of ER,
ESD, and BMP. However, the diode laser itself
generates significant optical energy with input
currents of less than one ampere. Low voltage
ground loops or injected RF radiation can generate
optical energy. Therefore, if the system will
encounter severe ER, ESD or EMP environments,
the diode laser and its drive circuit must be protected
electronically or electromechanically.

Diode laser initiation systems have been or are
being developed and tested for applications in motor
ignition safety devices, missile ordnance initiation
systems, space launch systems and flight termination
systems.

Also see these links:
http://pdf.aiaa.org/preview/1997/PV1997_2827.pdf

and

http://pdf.aiaa.org/preview/1997/PV1997_2695.pdf (source mentioned above)

***EDIT***

Units are correct. The laser is focused on a VERY small region of the explosive material and this is sufficient to cause detonation. (By focusing on a smaller region the power available is concentrated on that spot.)

Assume that our 10 watt laser is focused to a 0.01 cm diameter spot size. This translates into a 7.9 x 10~ cm2 area. There are several methods of calculating the approximate watts/cm2 of this spot. One is to use the incoming (laser output) beam area to focused spot area ratio. For example:.

1 cm2 ÷ 7.9 x 10~ cm2 = 12,658.2 (ratio)

Then:
Laser Output Power watts/cm2 x ratio = Focused Spot Power watts/cm2

Or:
10 watts/cm2 x 12,658.2 = 126,582.2 watts/cm2

Another method to achieve the same result is to calculate the laser beam average power density (power/unit area) by dividing the laser output beam watts by the focused spot area. For example:

10 watts ÷ 7.9 x 105 cm2 = 126,582.2 watts/cm2

Boomer
November 11th, 2003, 09:53 AM
The units are in the right range. 126 kilowatts for primaries and 12 megawatts for PETN sounds feasible. If you consider the brisance value used by Kast (energy/g x density x VoD), it also equals watts per square centimetre. And this is 900 megawatts for TNT and 1800 megawatts (per square cm) for PETN IIRC, being 100 times more than what is needed for initiation!
For exploding bridge wire caps you also need same megawatts for a very short time. (I built some and did tests, but this will be posted another time and where it belongs.)

BTW a fellow engineer in my company used to work in a mining university in Russia. They developed a fibre optic system for up to 1 km range. It was triggered with a hollow cylinder of HE with a high aluminium content, and a laser crystal in the centre. The light output was so high that the first meters of the fibre melted, and naturally it was one-time-use only. But compared to the cost of drilling and loading holes for a week, this did not matter. He does not know whether the tests were stopped or if it is in use today, but it worked and was lightning/ground current safe. He has no idea why they did not simply use 1km of det cord, as it was used between charges anyway.

P.S. Funny to be a newbie again after 20 years of ‘blasting around’….

Jacks Complete
November 11th, 2003, 03:20 PM
Interesting topic.

To confirm what another poster said, UV light doesn't travel well through much. Of course, visible light doesn't either, if it is comms grade stuff, since the fiber is tuned for IR at either 1.3 or 1.55 microns. However, for short runs, like less than 1km, you probably wouldn't notice.

NBK2000 had the right idea, though. If there is an explosive primary that will go off under bright light (rather than from thermal shock from IR or from UV decomposition) then it should be almost trivial to get this system working. (Having re-read my post, it is trivial in THEORY only!)

Stupid energy densities can be got from just a simple diode laser, since you can focus a spot down to about 1.5 wavelengths of the light with just a lens or two.

If you have a suitable primary (I have never even heard of NCl3 before) it should be easy to do.

All that is needed, as far as I can see, is a fibre optic that can carry the energy that we want, and that has a small enough end diameter. Mono-mode comms fibre isn't mono-mode at optical frequecies, but it will still only be a little bigger. Score and break the end for a sharp cleave, then apply your ultra sensitive primary with care (tape over the other end first?) and then cover/dry/adapt. (Read the rest before you do this! This is the easy end!)

Now, launching the fibre might be a problem. You need to focus the laser down to a very small spot with something like a microscope eyepiece to get it into the fibre with any kind of energy density. There really isn't an easy way to do this. You need a translation stage with at least 4 degrees of freedom for best results. You could make one, though. It would be fiddly, but using something like Meccanno, it could be done.

First, you need to wrap the end of the fibre so that it sits in your neat V-groove, then lightly clamp it. Now, turn your laser on, and aim the laser into your eyepiece, then clamp that too. You might want to make your stage so that the laser and the fibre have good positive locking, in roughly the right place.

Now, scan your translation stage back and forth, whilst watching...

Ok, so I am going to give up here. This is actually a non-starter given the practicality of doing this, and the fact you will have no fun trying to set off multiple things without multiple translation stages and lasers, each carefully aligned before hand and not knocked or allowed to expand or contract in the heat or not of where you are doing this.

Sod it. I will finish. I have been typing for at least 30 minutes.

Right, watch the end of the fibre so you can see the output, preferably with a good laser power meter, but a load of neutral density filters would work too, as long as you could flick them in and out easily, while still being able to see the projection on the screen (white paper will do)

Scan back and forth till you get some light coming through. Now carefully work the X & Y dials so you get as much light through as possible (use the filters to help you judge), then tweak the Z axis. Work X & Y again, and repeat until you feel you have the best you can get.

(For reference, Melles Griot sell automatic systems for many thousands of £ that do this automatically.)

Perhaps now would be a good time to point out that the whole thing is prone to dying if it moves more than about 2 microns (consider the spot sizes!) so you should do this where it is to be used. You can trap the fibre under a rock or whatever, and spool it out afterwards if you want, as long as you don't twist or move the fibre launch. Set it up, then when ready, move your safety shutter, and toggle the laser (you would want a remote switch, as pressure on the side of the laser would cause mis-alignment before the laser came on...)

Anyway, the other way would be to use a plastic FO and then you can launch it far more easily. The problem with that is the laser would need to be very, very powerful for that as it is a larger exit diameter, and you would most likely still need a carefully aligned lens on the other end of the fibre, to focus the light onto the primary.

If anyone cares, I can post a diagram and description of how to make a translation stage, or you might get some hits off Google. Or you might get one off eBay.

Anyway, in summary, it is likely to cost you lots of money unless you have a good home optics lab and lots of skill and ingenuity. And it still might kill you if the sun comes out!:eek:

Edit: Typo, plus: If you did need UV, a white phosphor, as found in most white LEDs would perhaps work?

Bert
November 11th, 2003, 03:29 PM
Boomer-

Do you have any numbers to put with that description of a pyrotechnicaly pumped LASER? It's something I've been dreaming about for years.

BTW, some information on fiberoptic/LASER initiation of devices is to be found in Hardt's Pyrotechnics- And for real world use, so far shock tube is cheaper, simpler and all around easier. It can be bought (for far too much) from SFX suppliers, it's used for popping balloons on cue and other stage effects. For blasting, it is often initiated with an electrical arc rather than a shotgun type primer. Pyrotechnic (flame) initiators and shock to flame output converters are also available- Ever wanted to set a fireworks show on the top of a building next to a commercial radio transmitter?

The side thread about X-ray detection/initiation by devices will obviously not please those in the EOD field.

Tuatara
November 11th, 2003, 04:53 PM
I doubt the x-ray idea would work. Airport scanners use really low levels to avoid damage to cargo or people. It's too weak to fog photograhic film, so it wont do didly to a primary.

A simpler method than messing about with microtranslation stages is to buy a 1300nm laser diode with a fibre connector built in. Then you just chop, polish and insert the fibre :)

Whether the fibre runs single mode or multimode is irrelevant, as we're simply using it as an energy delivery system, not trying to cram 100Gb/sec of data down it. For the kind of distances we're after (a few hundred metres) cheap plastic fibre should be fine. remember you're going to lose the last 20m so you don't want stuff thats $10 /m

The Russian device probably had a ruby laser at its heart, though these are usually optically pumped using a xenon flash because you get to keep the ruby :rolleyes:

Other possibilities for optical pumping include Nd:YAG, and Nd glass. Peak output for Nd:YAG is 1064nm IIRC - ideal for fibre.


For those who haven't seen it yet
Sam's Laser Faq (http://www.repairfaq.org/sam/lasersam.htm)
is one of the best resources for home built lasers I've ever found on the web

Jacks Complete
November 11th, 2003, 06:22 PM
The problem with using the plastic stuff is that you are really going to have problems with powerful lasers destroying it, and if you don't use the powerful laser (which needs mains probably, plus cooling) you won't get the energy density to set off the primary.

An Nd:YAG pulsed laser from a telecomms surplus place would be great, but they tend to be expensive. I haven't looked for a long while, but the laser units from Challenger tanks used to be available. They were powerful, and ran from a decent car battery as standard(ish) units. They went for about (IIRC) £150 each. But even if the price has dropped a lot, you will still have fun getting it all to work.

I would rather use a really powerful visible laser than an IR one, too, since at least I would be able to see the thing that blinded me. With strong collimation on an IR source, and a decent power output, you won't know you are cooking your eye till you wake up blind the next day.

Of course, that might be better than a pyro solution to the problem...

As for the costs of the fibre, surplus comms stuff is available really cheaply. You could get 10km worth, and just lose the last 10 meters for a long time before it was an issue. That plastic stuff is here at Maplin (http://maplin.co.uk/products/module.asp?CartID=031111221537633&moduleno=2275&Products=1) . You will notice that it "supports combustion" at 75mm a minute. It might make good fuse on its own! I was very un-impressed with it, and it is quite pricey, too.

Anyway, if you want to try it, go ahead. I think it would be better to try a thinner fibre and a pocket laser diode for a light source, that's all.

Good luck, and let us all know whether you get anywhere. I will play around with mine if I get time.

Zeitgeist
November 27th, 2003, 03:49 AM
Actually, high power UV lasers can be made your self piss easily.

You see, atmospheric N2 is a very high gain lasing medium, and has strong emmission lines in the UV wavelength range.

TEA Nitrogen lasers. Do the Google.

Tuatara
November 27th, 2003, 05:15 AM
Not very portable though. Beam quality is also a problem, which would make it tricky to couple into a fibre. Also, though the peak power output is in the MW range, the energy per pulse is only milli joules, as the pulse is only 6nS or so. And it takes considerable effort to get more than a few pulses per second (read 'transverse gas flow'). Still, it might work with the right primary.

pyromaniac_guy
October 13th, 2004, 02:48 AM
Whether the fibre runs single mode or multimode is irrelevant, as we're simply using it as an energy delivery system, not trying to cram 100Gb/sec of data down it.

For those who haven't seen it yet
Sam's Laser Faq (http://www.repairfaq.org/sam/lasersam.htm)
is one of the best resources for home built lasers I've ever found on the web


actually it DOES matter if you use single vs multimode fiber -single mode fiber has a core of a few microns - wereas multimode fiberis normaly 62.5u or 125u - hugely higher surface areas at the fiber. if you try and cram the pulse of a passibly q switched yag - ie a tank rangefinder off of ebay down a single mode fiber the only thing you will suceed in blowing up is the input end of your fiber :)

on a side note - do any of the sources on light initiated explosiveslist a power density AND a total energy per pulse? power density doesnt mean much if it requires a few joules of laser energy to initiate the explosives - or if conversely you can get away with with only using a few microjoules for initiation..

And it takes considerable effort to get more than a few pulses per second (read 'transverse gas flow').

well, you only need one pulse to initiate your explosives, so rep rate is a non issue :) at that point, if you had acess to glass blowing equipment or could build a leak proof enclosure you could simply build a sealed nitrogen laser that only operated for a pulse or two between 'breathers'

-from one of the orignal contributing authors of sam's FAQ :)

Silentnite
January 11th, 2005, 02:38 AM
Wow, I was actually going to ask if this was the right place to post this but it looks like it is the more I read through it. There was a place at Lasershoppe.com that sold a Green Laser with very high output for 600 bucks. It was capable of burning through a cup 20 meters away, I believe. Unfortunately due to popular bush-itis, and the recent scare for the pilots, he stopped selling them. It was handheld and rather neat. And as he could make them handheld, I doubt it would be extremely impossible to figure out how to replicate them.

VasiaPupkin
January 11th, 2005, 08:38 PM
Detonators initiated by impulse diode or Nd laser (1.06mkm) through the fibre optic system is use in stage separation system of rocket.
Also it is developed for mining. For common laser sensitive explosive the level of laser energy is: (1.06mkm T=50ns): Pb azide >100mJ/cm2, Ag azide >20mJ/cm2, Cd azide >15mJ/cm2 (For comparision mercury fulminate >1000mJ/cm2).
Also some complex metal salts is useful. For example CP (and also very safe).
The most laser sensitive thing at this time is complex perchlorates with hydrazino-tetrazole and hydrazino-aminotetrazole. >5mJ/cm2 (1.06mkm T=30ns) for [Hg(H2NNH-CN4H)](ClO4)2 (This thing is used for special film charges for metal treat).
As a whole there is a tendency to use a more safe complex metal salts like CP and BNCP (in spite of high laser initiation energy) instead of common explosives like LA.

Altroman
September 8th, 2006, 06:21 PM
I suspect that there is a large difference in initiation energy between thermochemical initiation and photochemical initiation. If you are trying to heat a compound in order to initiate it, that takes a lot of energy. But if you can exploit a spectral absorption band, then you can achieve a much more efficient coupling between "light" and "reaction." Think of it like the quantum yield of a fluorophore vs. heating it to incandescence. For this same reason, fluorescent lights are much more efficient than incandescent lights.
So the question, in my mind: What initiating substances are photosensitive (in a chemical sense, not a thermal sense), and at what wavelengths? Or, can chemistry be used to add photosensitivity to known primaries?

Cobalt.45
September 8th, 2006, 11:20 PM
A while back, when TAD- PNVS was first being installed on the Apache, I used a UV activated adhesive to bond prism assemblies.

Today, there's UV activated repair compounds for BB'ed windshields and the like.

What I'm wondering, is if there's any useful reaction that's occurring that cures these adhesives. Something that could be exploited to initiate a primary.

We also used super fast-set epoxy. Very exothermic- to the point that you'd not be able to hold the bottom of the small "condiment cup" it was mixed in. Set in <20 seconds.

I never tried to combine the two properties, so the idea might well be impossible...

simply RED
September 10th, 2006, 06:20 AM
Slightly out of topic but did not want to open a new thread just for this.

This is the shematics of laser pointer remote control device.
Range 300 meters within the visible radius.
The transmitter is visible on the picture "TransPic". I already blew up the receiver and can not shoot it.

Transmitter: Multivibrator with one transistor amplifier modulates the laser pointer (chinese one for 0,5 euro).

Receiver: 9V consumation (forget to type it on the pic). Simplest possible. Just amplifier with one key transistor and relay at the end. The photoresistor is placed in white box (like film canister). Digital or "frquency" encoding maybe added to increase sensitivity and safety.
R1 is crucial for schematic adjustment. With 200 ohms it is not so sensitive. With 500 ohms it is too sensitive...

Enjoy!

Meawoppl
September 10th, 2006, 02:40 PM
A couple of patents I dug up on the subject:

http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=5179247.PN.&OS=PN/5179247&RS=PN/5179247

http://patimg1.uspto.gov/.piw?Docid=03408937&homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fn ph-Parser%3FSect2%3DPTO1%2526Sect2%3DHITOFF%2526p%3D1 %2526u%3D%25252Fnetahtml%2525%25252FPTO%2525%25252 Fsearch-bool.html%2526r%3D1%2526f%3DG%2526l%3D50%2526d%3DP ALL%2526S1%3D3408937.PN.%2526OS%3DPN%2F3408937%252 6RS%3DPN%2F3408937&PageNum=&Rtype=&SectionNum=&idkey=NONE&Input=View+first+page

http://patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=%2Fnetahtml%%2FPTO%%2Fsearch-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN%2F3911822

http://patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=%2Fnetahtml%%2FPTO%%2Fsearch-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN%2F4343242

There is a TON of other related literature linked in to all of those. It is a good idea, you can tell because somebody has already done it.

Ygarl
September 11th, 2006, 06:56 AM
There's UV laserlaser diodes available for &lt;$200. Regualer UV LEDs are &lt;$20 each. But I don't know if milliwatt range energy levels would do the trick. I mean, full daylight is equivalant to 400 watts/meter I believe. But a magnesium pyro flash compound with a condenser lens should be easily bright enough to do the trick.


Brave step here - but here goes...

Full Sunlight is 400w/f^2 or 1020 w/m^2.
However, this is full-spectrum sunlight - of which UV light is in fact a very small component.
Only about 5% of sunlight is in the UV spectrum. Of this light about 98% is in the 320 - 400 nM UVA spectrum. 2% is in the 280 - 320nM.

I'm not an explosives or chemistry expert - I'm a neophyte and only moderately experienced respectively - but electromagnetic spectra I do know.

Basically, I'm not sure what level of UV radiation you need to set off your explosive, but if you are looking in the 10mW range of the UV spectrum, and are in a reasonably decent latitude on earth in full sunlight you are looking at finding some way to collect the sunlight.
Perhaps a small Fresnel lens would work - bearing in mind that glass absorbs UV light so a glass lens would be useless. That's why you can't get a suntan through a glass window. :cool:

If you had about a 1-inch Fresnel lens, at about 10% efficiency in optimum conditions you'd get some 100 to 150 mW. You'd need a pretty decent grasp of the use of "proper" fibre optics to splice your collector to the cable and detonator setup. Fortunately, modern fibre optics have easy-to-fit connectors - though in the spirit of the do-it-yourself chemist/demo explorer, you might want to splice the lot yourself.

I wouldn't, but that's just me.

Anyway, I would not rely on sunlight unless truly desperate. If you needed - say - 10mW, and you're running on energy budget of about 100 mW (say - in the 50 degrees North area of Europe), you can start adding some factors in:
1) Morning: 30% efficiency due to oblique angle - down to 30mW
2) Light haze: 75% efficiency - down to 22.5mW
3) Cirrus Cloud: 50% efficiency - down to 11.25mW

You don't even want to know the numbers if you have a cloudy day, smoke (a killer for UV light!), smog etc.

You could find yourself carring around a 12-inch Fresnel lens from an old Seawolf game (not that I know anything about playing with giant Fresnel lenses and - say - Aluminium filings or charcoal mixtures...) just to make sure you have enough sunlight to achieve what a nice new £25 UV blue-light LED from one of those nifty new DVD recorders due out this month.

I'd stick with a UV LED or laser if you wanted to to this...