Electric pulse disintegration
|The Marx circuit of the WHOI electric pulse disaggregator. Here, the electric heart of the EPD is lifted out of the holding tank that is filled with transformer oil. On top (from left to right) the trigger pulse generator (with red warning light) and the high-voltage generator are visible. The clear tank to the right of the Marx generator is filled with water and accepts the sample holder with the steel plates (small white box inside the clear tank). (Jud Hammon, Mike Ingram, Mike Klatt and Tom Tatman)|
Maxwell Technologies/Physics International (now Tital Corg.), San Leandro, CA
With support from the US National Science Foundation and WHOI, Maxwell Technologies/Physics International (now: Titan Corporation/Physics International) built a prototype electric pulse disintegrator (EPD) for my laboratory. This instrument uses high voltage discharges to disintegrate polymineralic rocks.
The EPD consists of a high voltage generator that charges a series of capacitors that are separated by spark gaps (Marx curcuit, see picture). Once fully charged, a trigger pulse is send to the first capacitor bank, resulting in discharge across the first spark gap. Subsequent capacitors are discharged in series across spark gaps. The final discharge occurs between two steel plates that are submerged in water and hold the sample. If the conditions are suitable for disintegration, the discharge travels through the sample and splits the rock apart (an effect created by the expansion of a high-density plasma and/or sound waves). The disintegration occurs preferentially along grain boundaries and other zones of weakness. The disintegrated material falls through the gap between the steel plates and accumulates at the bottom of the holding tank (clear containment in Figure). Disintegration of kg-sized rock fragments typically occurs within minutes. Due to the fact that EPD uses dilatant instead of compressive force, minerals are left intact and the amount of overcrushing (production of fine fraction) is minimal. EPD is an ideal tool for generating clean minerals for further analysis.
My EPD was built by Jud Hammon, Doug Howood, Mike Ingram, Mike Klatt and Tom Tatman (then with Maxwell Technologies/Physics International) and installed at WHOI in late 2000. It has been operational since and accumulated nearly 125,000 high-voltage discharges. The instrument is accessible to colleagues at WHOI and outside users. Please contact me if you are interested in exploring this technology for your research.