188
K. A. S. Fessler et al.
loop(typically 70 torr), valve 4 is closed and the sample is introduced into the sample
cell by opening valve 1. The final pressure in the sample cell is typically about 80%
of the initial sample loop pressure. If sample purification is needed, valve 3 can be
opened and UF 6 is condensed in the cold trap. The cold trap is typically operated
at temperatures below 225 K where the partial pressure of UF 6 is less than 0.2 torr.
Common impurities have vapor pressures higher than UF 6 and are then removed by
opening vacuum isolation valve 2 and pumping the system. A typical purification
cycle lasts 30 min. The purified sample is reintroduced into the manifold by closing
the vacuum isolation valve 2 and allowing the cold trap to warm to room temperature.
The final target pressure in the multipass sample cell is 50 torr. The total pressure
was measured using an MKS 628C Baratron capacitance manometer in the sampling
loop. An ABB MB-2000 Fourier transform infrared spectrometer (FTIR) was used
to measure the partial pressure of uranium hexafluoride and any volatile impurities
in the sampled gas. The recorded sample measurement pressure was acquired from
the uranium hexafluoride partial pressure observed in the infrared spectrum at 1157
and 1290 cm
−1 using laboratory calibrations of uranium hexafluoride and volatile
impurities.
Absorbance spectra are generated by scanning the quantum cascade laser at 2.5
wave numbers/sec over a span of 25 wave numbers. Quantum cascade laser scanning is controlled through Daylight Solutions Sidekick graphical user interface. The
quantum cascade laser controller triggers the mercury cadmium telluride detector
readouts at the start of scan. The detectors are read using a Measurement Platform
consisting of custom electronics hardware designed by Savannah River National
Laboratory. The Measurement Platform hardware can control the laser trigger, data
collection and storage, data processing, and the displaying of the results. However,
the software thus far has been developed to initiate data acquisition upon triggering from the quantum cascade laser and transfer the data to a computer via
universal serial bus for processing. The completed hardware design is encased in
a 3D printed enclosure with a liquid crystal display for sensor status readout. The
processing features include a 400 MHz processor, 16-bit analog-to-digital converter
(ADC), two differential simultaneous sampling channels, 1 ns sample-time accuracy,
programmable gains, electrically erasable programmable read-only memory, and
16-megabyte synchronous dynamic random-access memory. These features allow
for low electronic noise (8.3 μV), 10
6 samples/sec readings, and data storage. A
Visual Basic program (HPIR-1B) configures the readout electronics and accepts the
reference and sample voltage readings. The HPIR-1B program writes the sample
and reference arrays to an Excel spreadsheet (HPIR-Process) for automatic data
processing, analysis, and archiving using Excel Macros. A typical total acquisition
and transfer time is 32 s/scan. The electronics hardware also includes multiple interfaces (2x configurable input/outputs, 2x PT100 resistance temperature sensors, 2x
pressure sensors, 2x mercury cadmium telluride infrared sensors) for temperature,
pressure, and mercury cadmium telluride detector control and readouts. The electronic system can be powered with a 12 V battery, which enhances the portability
and remote operation of the overall measurement system.
K. A. S. Fessler et al.
loop(typically 70 torr), valve 4 is closed and the sample is introduced into the sample
cell by opening valve 1. The final pressure in the sample cell is typically about 80%
of the initial sample loop pressure. If sample purification is needed, valve 3 can be
opened and UF 6 is condensed in the cold trap. The cold trap is typically operated
at temperatures below 225 K where the partial pressure of UF 6 is less than 0.2 torr.
Common impurities have vapor pressures higher than UF 6 and are then removed by
opening vacuum isolation valve 2 and pumping the system. A typical purification
cycle lasts 30 min. The purified sample is reintroduced into the manifold by closing
the vacuum isolation valve 2 and allowing the cold trap to warm to room temperature.
The final target pressure in the multipass sample cell is 50 torr. The total pressure
was measured using an MKS 628C Baratron capacitance manometer in the sampling
loop. An ABB MB-2000 Fourier transform infrared spectrometer (FTIR) was used
to measure the partial pressure of uranium hexafluoride and any volatile impurities
in the sampled gas. The recorded sample measurement pressure was acquired from
the uranium hexafluoride partial pressure observed in the infrared spectrum at 1157
and 1290 cm
−1 using laboratory calibrations of uranium hexafluoride and volatile
impurities.
Absorbance spectra are generated by scanning the quantum cascade laser at 2.5
wave numbers/sec over a span of 25 wave numbers. Quantum cascade laser scanning is controlled through Daylight Solutions Sidekick graphical user interface. The
quantum cascade laser controller triggers the mercury cadmium telluride detector
readouts at the start of scan. The detectors are read using a Measurement Platform
consisting of custom electronics hardware designed by Savannah River National
Laboratory. The Measurement Platform hardware can control the laser trigger, data
collection and storage, data processing, and the displaying of the results. However,
the software thus far has been developed to initiate data acquisition upon triggering from the quantum cascade laser and transfer the data to a computer via
universal serial bus for processing. The completed hardware design is encased in
a 3D printed enclosure with a liquid crystal display for sensor status readout. The
processing features include a 400 MHz processor, 16-bit analog-to-digital converter
(ADC), two differential simultaneous sampling channels, 1 ns sample-time accuracy,
programmable gains, electrically erasable programmable read-only memory, and
16-megabyte synchronous dynamic random-access memory. These features allow
for low electronic noise (8.3 μV), 10
6 samples/sec readings, and data storage. A
Visual Basic program (HPIR-1B) configures the readout electronics and accepts the
reference and sample voltage readings. The HPIR-1B program writes the sample
and reference arrays to an Excel spreadsheet (HPIR-Process) for automatic data
processing, analysis, and archiving using Excel Macros. A typical total acquisition
and transfer time is 32 s/scan. The electronics hardware also includes multiple interfaces (2x configurable input/outputs, 2x PT100 resistance temperature sensors, 2x
pressure sensors, 2x mercury cadmium telluride infrared sensors) for temperature,
pressure, and mercury cadmium telluride detector control and readouts. The electronic system can be powered with a 12 V battery, which enhances the portability
and remote operation of the overall measurement system.