New Field And Modeling Results From A Simulated Waste Pit Using The Enhanced Very Early Time Electromagnetic (Vetem) Prototype System

Tests in July, 1998, of an improved version of the prototype VETEM system demonstrated<br>improved depth of investigation at the Cold Test Pit (CTP) at the Idaho National Environmental<br>and Engineering Laboratory (INEEL). The improved depth of investigation is due primarily to<br>the development of larger loop antennas and a new transmitter capable of driving up to 30 times<br>more current than the original transmitter into the larger loop. An overlapped antenna<br>configuration was tried and proved effective in detecting buried objects. New display software<br>allows us, for the first time, to generate area1 time-slice displays of our data in the field for fast<br>qualitative evaluation. Comparisons of results using two different antenna configurations over<br>the Large Object Pit portion of the CTP show generally good agreement, but show an apparent<br>position offset of the two data sets from each other. The test over the Calibration Cell portion of<br>the CTP using the overlapped antenna configuration successfully located most of the indicated<br>targets in the cell. Results over both portions of the CTP suggest that the indicated locations of<br>some of the buried objects may not be completely accurate. New antenna and 3D forward<br>modeling codes run using an input waveform, antenna size and configuration, and system<br>bandwidth matching those of the VETEM system produce waveforms and show sensitivities<br>similar to those seen in recorded field data.