Results And Discussion

In addition to the high sensitivity, the ability to rapidly switch in additional feedback capacitance inherently gives the device a large dynamic range.

Detection sensitivity for explosives has been increased dramatically. Figure 9 shows a peak produced by 12.5 picogram of TNT. While the detection limit (signal 3* the rms of the noise) in a similar miniature drift system, using a conventional operational amplifier for current to voltage conversion, was calculated to be 10 nanograms, the detection limit in this case is below 0.9 picograms.

Figure 9. Showing the trace made by a 12.5 picogram sample of TNT. The detection limit is calculated to be approximately 0.9 pg. In the 3D trace, the left to right horizontal axis is drift time in milliseconds, and the front to rear horizontal axis is the scan number, with the sample being introduced at scan 82.

12.5pg TNT 96C. Filament. 1200 us Pulse. B.C

Figure 9. Showing the trace made by a 12.5 picogram sample of TNT. The detection limit is calculated to be approximately 0.9 pg. In the 3D trace, the left to right horizontal axis is drift time in milliseconds, and the front to rear horizontal axis is the scan number, with the sample being introduced at scan 82.

Unlike the operation of many focal plane arrays, integration times are very short (30-50 milliseconds), so dark current effects at room temperature are negligible. In fact, to evaluate operation in hostile desert environments, the detector was operated over a range of temperatures up to 80°C. The device operated properly and the read noise increased to < 6 electrons.

This initial application of a CMOS-CTIA device designed for IMS indicates that such devices may play a major roll in improving the sensitivity of IMS systems, which could have a dramatic impact on detecting improvised explosive devices.

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