Lenses, explosive

An explosive lens is used to generate a flat detonation wave. The explosive lens consists of two cone-shaped segments of explosives, an inner cone and an outer cone, which are fitted together as shown in Fig. 9.2. When detonation is initiated by an electric detonator, a booster charge positioned at the top-center of the inner-cone explosive detonates. Then, the inner cone detonates and the detonation wave propa-... 

Fig. 9.2 Formation of a flat detonation wave by an explosive lens.

Fig. 9.3 Formation of a strong one-dimensional detonation wave with an explosive lens.

Personnel involved in the handling of methanol require eye and skin protection from the irritating properties of methanol in the event of a spill. Contact lenses should not be worn, since plastic lens materials may absorb and concentrate methanol against the eye. Additional respiratory protection is not required with adequate local explosion-proof ventilation. 

Optical detectors shall be used in more open configurations where ressure buildup due to the incipient explosion is limited. Optical etectors shall not be used where high dust concentrations limit the reliability of the suppression system. Both uv and ir detectors are available for optical detection. The use of daylight-sensitive sensors shall be avoided to avoid spurious activation. The sensor shall be mounted such that the angle of vision allows it to cover all the protected hazard area. The performance of an optical detector will also be affected by any obstacles within its vision, and this shall be overcome by the introduction of more detectors. Optical detectors shall be fitted with air shields to keep the optical lens clean. 

An optical flame sensor installed at the beginning of the pipeline is the most suitable device for such an isolation system, since the propagating flame from the explosion has to be detected and extinguished. Pressure detectors alone are, in principle, not suited to the case on hand because there is no distinct separation between the pressure and flame fronts for explosion in pipelines. Optical ir sensors that have a relatively low sensitivity to daylight are normally chosen and have proved themselves amply in industrial practice. Therefore, daylight into the pipe in the vicinity of the sensor must be avoided. It is necessary to flush the optical lens with gas (e.g., nitrogen, air) to keep it dust-free. 

Nonexpendable light sources, such as a Q-switched pulsed laser can be protected. from destructive forces encountered in the photography of explosive material by piping the light through fiber optics, to the experimental zone. Occasionally lens systems are used to relay the light from mirrors located near a protective barrier shielding the laser (Ref 16)... 

The x-ray beam axis is perpendicular to the direction of detonation in a 10 cm cube of Composition B-3 explosive (the HE) which is initiated by a large diameter plane-wave lens. (Since the machine can be flashed only once during the passage of the detonation wave, the time sequence is obtained from repeated experi-... 

The booster-and-attenuator system is selected to provide about the desired shock pressure in the sample wedge. In all but a few of the experiments on which data are presented here, the booster-and-attenuator systems consisted of a plane-wave lens, a booster expl, and an inert metal or plastic shock attenuator. In some instances, the attenuator is composed of several materials, The pressure and particle velocity are assumed to be the same on both sides of the attenuator-and-sample interface. However, because initiation is not a steady state, this boundary condition is not precisely correct. The free-surface velocity of the attenuator is measured, and the particle velocity is assumed to be about half that. The shock Hugoniot of the attenuator can be evaluated using the free-surface velocity measurement. Then, the pressure (P) and particle velocity (Up) in the expl sample are found by determining graphically the intersection of the attenuator rarefaction locus and the explosives-state locus given by the conservation-of-mom-entum relation for the expl, P = p0UpUs where Us = shock velocity and p0 = initial density. The attenuator rarefaction locus is approximated... 

Photographs of the detonation of ammonium nitrate explosives with an open lens camera were taken by T. Urbariski [28], The image was composed of light and dark bands with a sinusoidal shape. An hypothesis was advanced by the author of the possible spiral way of the detonation. At the same period British authors - Campbell, Bone et al. [29, 30] published a number of papers in which they indicated the spiral way of the propagation of detonation of gas mixtures. Their results were substantiated by Laffitte et al. [31],... 

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