Data acquisition techniques for explosive high current generators

The Hydrodynamic and X-ray Physics Group (P-22) at Los Alamos National Laboratory has developed hardware, software, and procedures to work with explosively driven high current generators to obtain time resolved data. Data recording in this physically and electrically harsh environment requires special equipment, techniques, and processes. To avoid ground loops and EMI noise problems, fiber optic techniques are used to deliver the data from the shot pad to the recording area in the bunker. Data from electrical B-dot, V-dot, Rogowski, X-ray diodes, Faraday rotation current measurements, are all part of the diagnostic probes that are routinely recorded by our data acquisition systems. Shielded 50 Ohms coaxial cables deliver the electrical probe signals to an area close to the device, generally about 50 feet, behind a blast shield. Behind the blast shield are several EMI shielded boxes containing fiber optic transmitters and proper attenuation for the probe signals. These fiber optic transmitters are battery powered and are allowed to float electrically. The bunker area contains the fiber optic receivers, waveform digitizers, triggering equipment and data acquisition computers. From the shot pad area optical fibers provide the signal path into the bunker and the fiber optic receivers. Where necessary the bunker ground loops are broken with fiber optic trigger hardware and large-scale uninterruptable power supplies (UPS). These units have storage batteries to provide clean AC power to operate the data recording equipment during the experiment.