The apparatus used in the DDT tube experiments is shown schematically above. The DDT tube used was a thick walled 77.6 mm o.d. stainless steel 304 tube with a 96.5 mm length and 6.4 mm i.d. The 143:1 inner to outer cross sectional area provided enough inertial confinement to contain the DDT event radially. The piston was loaded into the bottom end of the tube and set flush with the bottom surface. HMX was incrementally loaded directly into the tube in 3 mm lengths, and a lexan plug was set in the end to temporarily confine the bed.
The ignitor block was made of vascomax 250 maraging steel. A PYROFUSE¨ was set into the bottom of the chamber with a thin mixture of titanium and boron, a gasless pyrotechnic, covering the bridge wire. A load of loose HMX in the burn chamber was ignited by the burning titanium and boron and the burning HMX powder raised pressures enough to drive the piston into the bed of HMX leading to initiation. A pressure transducer (PCB 109A02) was mounted into the side of the burn chamber, and in the first two tests, side closure pins were positioned at four locations near the bottom of the tube. The mating lip between the ignitor block and main tube was sealed with a thin copper washer to prevent venting, and the entire assembly was held together with four one inch thread bolts. A small hole in the upper confinement plate allowed visual inspection of tube for residual explosive before disassembly. On the four later shots, a capped pin was set in the top of the tube as an indicator of when the detonation had reached the end of the tube. All pressure data were collected using a pair of LeCroy 9400A Dual channel oscilloscopes. The PYROFUSE¨ was ignited by a low voltage CDU, and the capped pin data were collected by a time interval meter.
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Last Modified 8/22/97