Located in Chauvenet Hall on the Colorado School of Mines campus, the CESEP experimental labs occupy over 4000 square feet. They include a high-bay area suitable for large-scale experimental tanks and flow cells, two analytical labs, and a dedicated X-ray room. The labs and major analytical devices are described in the following paragraphs.
X-ray attenuation system for measuring phase saturations in multiphase systems
The CESEP X-ray attenuation device is contained within a custom-designed mobile frame capable of precise vertical and horizontal positioning. Three motors together control the horizontal axis, the vertical position of the X-ray tube, and the vertical position of the detector over a 10ft by 5ft vertical plane. All of the motors are controlled by a Baldor Smartmove embedded controller which in turn responds to commands sent from custom LabVIEW driver programs running on a host computer.
The X-ray source is a Pantak model HF100 device which is capable of producing photons with energies up to 100keV. The intensity (voltage and amperage) of the X-ray source is manually controlled. The X-ray source enclosure is designed to hold numerous X-ray filters and an integral, fail-safe shutter. The beam is collimated with adjustable aperatures typically ranging from 1mm diameter to 10x10mm square. Given the dimensions of the frame, flow cells up to 33cm in width can fit between the X-ray source and the detector.
The X-ray detector used here is a liquid-nitrogen-cooled Princeton Gamma Tech (PGT) High-Purity Germanium (HPGe) device coupled with a PGT SYS4004 multichannel analyzer. The detector has 4096 channels and is capable of 0.5 keV energy resolutions (FWHM) at 60keV. The detector is controlled by the host computer over a serial line through custom LabVIEW software.
Overall, the X-ray system has been optimized for throughput. Individual measurements have been made in less than ten seconds, including both the detector counting times and the waits necessary for motor positioning.
Dual-Gamma Attenuation Device
Located the high-bay area, the CESEPs dual-gamma device is mounted on a frame similar to the X-ray system. It is capable of precise positioning in a vertical plane that is over 35ft long and 5ft high. The motor positioning is set and recorded by custom LabVIEW programs which communicate (over RS-232) with a Baldor embedded controller.
Gamma rays are produced by two sealed radioisotope sources:
- 200 mCi of Americium-241 with a primary peak at 60keV
- 50 mCi of Cesium-137 with a primary peak at 662keV
which are contained within a collimated source enclosure. The relative strengths of the two gamma sources can be tuned through selective filtering to provide maximum accuracy/precision for the simultaneous measurement of water and oil saturations.
The detector used for the dual-gamma system is a photomultiplier device coupled with an Ortec 918A multichannel buffer. The detector is controlled by custom LabVIEW programs that communicate with the MCB over a serial line (RS232).
GC and HPLC Chromatography
The CESEP analytical laboratory is equipped with a variety of analytic instruments. Gas chromatographs are used to determine regular to trace amount different kinds of organic chemicals and chlorinated solvents. IC/HPLC Systems have both conductivity and UV detectors, capable to quantitatively analyze for different anions (Br-, PO43-, SO42-, Cl-, etc.) cations (Li+, Na+, NH4+ , K+, Ca+, Mg+ etc.,) and organic acids. With the UV detector, this system also is able to measure organic compounds (include: PAHs, PCE, TCE, etc.). This system have been routinely used for measuring Br and five basic anions (F-, Cl-, NO3- , PO43- and SO42- ) and six basic cations (Li+, Na+, NH4+ , K+, Ca+ and Mg+) of samples from column, 2D cell and 3D tank experiments.
Soil columns and small 2d cells instrumented with soil moisture sensors, air and water pressure measurement probes and thermal sensors.
Soil columns are used to study problems involving soil water and temperature variability.
Various intermediate scale test tanks
The test bed facility has a number of 2-D and 3-D tanks. Pre-fabricated tank wall units of dimension (8 ft x 4 ft) can be arranged up to 32 feet long.
Temperature controlled test tanks
8 ft long insulated test tanks to study vapor and air flow through unsaturated soils are available. The tanks are instrumented with soil moisture, relative humidity and temperature sensors. Heat flux can be applied at the soil surface.