SBIR-STTR Award

It is well documented that primary explosives like Pb(N3)2 can be initiated (detonated) by high level laser pulses. The high power of the lasers is required because the laser power is utilized to initiate Pb(N3)2 - only indirectly. The ir and near ir radiation of the laser is absorbed by PbNaB or Pb(N3)2 blended with carbon black giving rise to vibrational excitation which, in turn, results in thermal energy which finally initiates Pb(N3)2. The initiation of Pb(N3)2 has also been accomplished by radiation of wave-lengths 347 microns and 265 microns by direct photoexcitation of the azide ion. However, the radiations 347 microns and 265 microns have been obtained from ruby and nd lasers indirectly by frequency doubling from visible and frequency quadrupling from ir respectively resulting in very low efficiency. The objective of this proposal is to modify Pb(N3)2 at a molecular level so that low level laser pulse can initiate Pb(N3)2 directly by photoexcitation. Our unique approach is to move the electronic excitation region of Pb(N3)2 crystals (powder), at a molecular level, with 10-2 - 10-1 weight percent colored dopants like red Fe(N3)3, red PbCr2O7 and black brown Pb3 [Fe(CN)6]2.

In Phase I PAI Research Ltd. (PRL) has drastically reduced the laser energy required to initiate lead azide by employing doping techniques. Thus, the cw IR power requirement has been brought down from 200 mw to 30 mw and the pulse energy from 2.5 mj to 0.21 mj for dopant concentration as little as 0.2 wt%. We have also successfully initiated our doped lead azide samples simply by focusing the sun's radiations. If the threshold initiation power requirement is further brought down from 30 mw to l0 mw, the cost goes down from $300 to $30. (Costwise, our present Phase I efforts have already brought the cost from $1200 to $300-$150). In Phase II, PRL is proposing improvements in doping techniques which will enable the doped lead azide to be initiated by l0 mw laser diode. We will also carry out experiments to understand our Phase I observation that green light is ten times more efficient than IR in initiating lead azide and further extend the concept to blue light initiation.