Project ID: 60162 Project Title: Enhancements to and Characterization of the Very Early Time Electromagnetic (VETEM) Prototype Instrument and Applications to Shallow Subsurface Imaging at Sites in the DOE Complex

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