Mineral and Materials Characterization Facility – Instrumentation
TESCAN Integrated Mineral Analyzer
TESCAN MIRA3 LMH Schottky Field Emission-Scanning Electron Microscope
The FE-SEM laboratory in the Department of Geology and Geological Engineering serves students and faculty within the department as well as the broader research community at CSM and the Front Range region. The laboratory provides imaging and analytical services.
Users at all levels of experience are welcome. The FE-SEM forms an integral part of our undergraduate education in petrology and mineralogy and can be accessed by undergraduate students during scheduled class and laboratory activities or as part of their supervised research. The instrument is widely used by graduate students in economic geology, petroleum geology, geological engineering, and hydrogeology. Diverse research is conducted by CSM faculty members. The FE-SEM laboratory also serves the research needs of external users, including government agencies, museums, and private businesses.
The FE-SEM can be used for imaging at magnifications of 10x to over 300,000x at a spatial resolution down to the nanometer scale. In addition to imaging, semiquantitative chemical analysis can be performed by energy-dispersive X-ray spectroscopy.
The FE-SEM was aquired by Drs. Thomas Monecke and Katharina Pfaff in September 2015. Purchase of the instrument was made possible through a partnership agreement between TESCAN and Mines. Major donors who contributed to the instrument purchase included Apache Corporation, Tim Bartshe, Marshall and Jane Crouch, Hugh and Michelle Harvey, John and Erica Lockridge, and Jim Weber.
Important instrument specifications are given in the table below.
|Internal size of chamber:||230 mm|
|Width of door:||148 mm|
|Maximum specimen height:||81 mm|
|Stage:||Compucentric, 5-axis fully motorized|
|Resolution of SE detector:||1.2 nm at 30 kV and 2.5 nm at 3 kV|
|Resolution of In-Beam SE detector:||1 nm at 30 kV;|
|Chamber vacuum:||<9×10-3 Pa|
|Gun vacuum:||<3×10-7 Pa|
|Field of view:||6.4 mm at working distance of 10 mm (Easy Mode training level)|
|Electron gun:||High-brightness Schottky emitter|
|Acceleration voltage:||200 V to 30 kV (20 kV in Easy Mode training level)|
|Probe current:||2 pA to 200 nA|
Backscatter Electron Imaging
Backscatter electrons are high-energy electrons used to obtain high-resolution images show variations in the mean atomic number in the sample region imaged. Backscattered electrons occur as a result of the elastic scattering of electrons in the primary beam with atoms in the sample.
The FE-SEM features a TESCAN motorized retractable annular, single-crystal YAG backscatter electron detector. The full functionality of the BSE detector is available to user at the Easy Mode training level. At this level, users are able to acquire high-resolution images at a working distance of 10 mm with an acceleration voltage of 20 kV. The image to the left shows a view of the sample chamber. The retractable BSE detector in operating position is located immediately below the pole piece of the FE-SEM. The EDS detector can be seen in the left behind the pole piece.
In-lens Secondary Electron Imaging
The FE-SEM is also equipped with a TESCAN In-BeamTM in-lens secondary electron detector. This detector is not available to users at the Easy Mode training level.
Energy-dispersive X-ray Spectroscopy
The FE-SEM is equipped with a Bruker XFlash® 6/30 silicon drift detector for energy-dispersive X-ray spectroscopy (EDS). The full functionality of the EDS system is available to users at the Easy Mode training level. The table below lists some of the key specifications.
|Active area:||30 mm2|
|Silicon thickness:||0.45 mm|
|Window material:||Super-light element window|
|Collimator:||Multi-layer, 6.0 mm aperture|
|Working distance:||10 mm|
Training Level policy
Based on the level of experience in electron microscopy and familiarity with the instrument and laboratory-specific procedures, users are given access to the software of the FE-SEM at different training levels. Most users of the laboratory facility have access privileges at the Easy Mode training level, which provides full functionality of the instrument at a fixed working distance of 10 mm and an acceleration voltage of 20 kV. Training of new users is currently only provided at the Easy Mode training level. A presentation for new users at the Easy Training level can be downloaded here.
To minimize the risk of a collision between the sample/stage with the detectors, only users with significant experience are given full software access to all five motions of the motorized sample stage (i.e., z-axis and stage tilting). Similarly, usage of the BSE and in-beam SE detectors at working distances below 10 mm is restricted to a limited number of users only. Users will be granted higher access privileges on a case by case basis.
Sign-up and Billing policy
After users have been authorized to operate the instrument, users will be granted access to the online calendar to schedule time on the instrument. Users at the Easy Mode training level can only sign-up during prime time hours, which are 9 am to 5 pm Monday through Friday. Certain prime time slots are reserved for teaching and instrument development work and cannot be booked using the online calendar. Users are strongly encouraged to sign-up only for the amount of instrument time required. Users may reserve time only for themselves and are not allowed to turn-over time slots to other users without permission.
Reserved time will be forfeited if a user does not begin within 10 minutes of the scheduled start time. If users cancel a reservation less than 24 hours prior to a scheduled start time or do not use reserved time, they will be charged for a minimum of one hour of instrument time. Billing is performed in 30 min increments and commences at the reserved starting time. When reserving time, users should leave 30 min between the end of the previous session and the start of their own session to allow sufficient time to get ready (mounting of samples etc.).