Medical-based HD-350 scanner
Our Universal HD-350 scanner is based on a medical scanner modified to allow tuning to materials other than water and for extraction of raw image data for offline analysis. It allows in-plane pixel sizes from 0.25 to 1 mm on a side on objects from 120 to 480 mm in diameter. Slice thickness can be varied from 1 to 10 mm. It uses excitation voltages from 80 to 140 kV with maximum power of about 13 kw. The images are 512 x 512 pixels.
Industrial HD-600 scanner
Our Universal HD-600 scanner is a unique system designed for high resolution and maximum flexibility. Its main features include dual X-ray sources, 1024 x 1024-pixel area detector with image intensifier, and a continuously tiltable gantry for horizontal or vertical sample orientation. The micro-focus source is an X-tek 225 kV, 225 watt tube with a minimum focal spot size of about 5 microns at 8 watts. The higher-power source is a Pantak 1600 watt sealed x-ray tube capable of 320 kV with the minimum focal spot of about 100 microns. The HD-600 is capable of continuously variable magnification with pixel sizes approximately 1/1000 of the sample diameter.
Experimental Support Facilities
Much of the emphasis at the Center for Quantitative Imaging is on monitoring of internal processes. Examples are changes in porosity distribution during mechanical deformation, changes in fluid phase distribution during multi-phase flooding of a porous medium, water migration in curing cement, and diffusion of contaminates in fruit. Frequently the processes studied depend on environmental conditions, typically temperature and pressure. To accommodate these studies, the center has a range of chambers, condition controllers and transducers.
The facility possesses eleven X-ray transparent core holders covering sample diameters from 1 to 4 inches, and lengths up to 24 inches. These vessels can apply confining pressures up to 10,000 psi and temperatures up to 150 degrees C. Two of the vessels can apply independent axial loads for triaxial testing. Most of these have fluid access ports for multiphase fluid flow observations and can be made to accommodate additional instrumentation such as strain gages or other transducers.
Fluid pressure injection equipment consists of a range of pump systems:
- Five precision computer-controlled dual-piston syringe pumps capable of pressures up to 3000 psi and flow rates up to 100 cc/min
- three additional manually controlled syringe pumps
- three HPLC piston pumps
- A hydrostatic flow system for very low constant pressure injection
Transducers and data acquisition
Confining Pressure, differential pressure, and temperature can be monitored and recorded through a system of transducers and data acquisition software. Transducers include several resistance-bridge diaphragm models ranging from 1000 to 10000 psi gauge pressure, similar differential pressure gauges with 50 to 100 psi range, additional variable reluctance differential pressure transducers with replaceable diaphragms covering a wide range of pressures, and three high-precision quartz absolute and differential pressure transducers. These can be calibrated in house against dead weight testers or high-accuracy Heise gauges. Data are recorded using dedicated software or separate DAQ systems. Flow rates are controlled by the precision pump system or by a timed fluid collection system.
Computation and Archiving Facilities
The Center has dedicated computational facilities for reconstructing, visualizing, analyzing and archiving CT data. High-resolution reconstruction is handled offline from the data acquisition computer using a combination 25-CPU unix computer system and 12-CPU Linux machines. A new firmware-based reconstruction machine is expected to be on line shortly. This system has 3.5 terabytes of fully mirrored storage and is additionally backed up by a College-operated nightly backup system. Older data are archived on two tapes, one stored remotely from the facility.
Data are manipulated, analyzed and visualized using combinations of PV-Wave, Avizo (Amira), ImageJ, and other software. These packages are run on the Unix system and on two additional Linux workstations with 12 and 16 GB RAM. These systems and software are available for student and faculty use and Avizo licenses are available to Penn State users at much reduced cost.