SIMS Cameca 1280-HR
Our facility's core instrument is a Cameca 1280-HR mass spectrometer (s/n 23) which was delivered in March 2013. It is equipped with a 5 trolley multi-collection system, which can have up to 5 electron multipliers or 5 Faraday cups. We also have a Resistive Anode Encoder for mapping the distribution of low concentration elements. We have an up-graded vacuum system, including oil-free roughing pumps, a vibration damped 550 l/s turbo pump on the sample chamber and an NMR field controller for high stability magnetic field control during multi-collection analyses. This instrument is housed in a thermally stabilized laboratory which has a temperature range of only +/- 0.3 C. For most applications instrument operation is done from an adjoining room via a desktop duplication system.
The Potsdam1280-HR has been demonstrated to be one of the most stable such instruments world-wide for isotopic ratios determinations, having achieved a repeatability on d18O determinations of 0.09 ‰ over 17 hours of automatic data collection (N = 100). We interpret this excellent level of performance as partly due to the careful detail and innovative design elements that were incorporated during the facility's planning. An overview of our laboratory design was presented the 7th Biennial Geo-SIMS Workshop held in August 2013. <Download powerpoint presentation, 32 MB>
1280 Instrument Upgrades
Enlarged LN2 Dewar on Sample Chamber -- By cooling a ring located in the sample chamber to liquid nitrogen temperature (-196°C) it is possible to improve the vacuum within the secondary ion source by a factor of two or three. The standard LN2 tank for the 1280-HR tool requires refilling roughly every 6 hours, making continuous operation difficult. Installed in December 2014, our 7.5 liter LN2 tank can remain cold for up to 10 days without refilling. This upgrade significantly improves our analytical capabilities, and in particular suppresses unwanted hydride molecules that are formed from vacuum contaminants. The tank must be warmed prior to using oxygen flooding, and for this we have a house nitrogen gas line delivered via Tygon tubing.
Peripheral Instrumentation in the Potsdam SIMS Lab
In addition to our SIMS tool we also have other instruments which support our operation.
White Light Optical Profilometer: ZYGO New View 7100 -- Without making any contact with the sample surface, this instrument can determine surface topography with a spatial resolution of 500 nm in X and Y and 0.5 nm in Z . It can determine the depth of SIMS profiles and the surface roughness parameters both of the original sample and the regions that have been sputtered with the SIMS primary beam. It can also calculate the absolute volume of a SIMS crater from which the test portion mass of the method can be derived. Sample flatness and tilt parameters over larger areas areas can measured using an image stitching function. An analysis involves moving the measurment head vertically at a very controlled rate, with a total travel of between 40 and 100 µm. A single measurment requiares around 40 seconds and with our two objectives we can provide either a 1 mm or a 200 µm wide field of view. <Download example of profilometer data, 191 kB>
Motorized Optical Microscope: Nikon Eclipse -- Many stable isotope analyses (e.g., d18O determinations on silicates) can be completed by the 1280-HR tool in a matter of few minutes. This means that the actual moving of the SIMS sample stage and centring of individual points, typically taking a minute or two per point, becomes a significant factor influencing the overall data production rate. We have a fully motorized in X-Y-Z optical microscope which is being developed for off-line coordinate pre-selection. A sample mounted in a SIMS sample holder is placed under the microscope and the locations of up to several hundred points can be defined, thereby saving a large amount of SIMS instrument time. Also, thanks to the motorized Z-axis, it is possible to create 3-dimensional topographic maps of a sample surface. This microscope's filed of view ranges from roughly 12 mm to 200 µm, depending on which objective us in use.
Gold Sputter Coater: Edwards Scancoat Six -- SIMS analyses using the 1280-HR instrument require the sample to be electrically conductive. As most geological materials (e.g., silicates, carbonates, phosphates) are electrical non-conductors, it is necessary to coat our samples with a conductive thin film prior to placing the sample in the SIMS sample holder. Our gold coater is able to coat up to 3 samples simultaneously, requiring around 15 minutes for the complete vacuum pump-down and coating operation. Our Edwards gold coater monitors the coating thickness during the process. For most SIMS applications we use a 35 nm thick gold coat. The system is pumped by an oil-free scroll pump and is supplied by house argon.
Vacuum Oven: Heraius Vacutherm
The quality of the SIMS vacuum depends strongly on minimizing the presence of water molecules adhering to surfaces within the 1280-HR vacuum system. Of particular importance is an ability to keep H2O away from the primary ion sources. Our vacuum oven can be maintained at a few mbar pressure, which we flush occasionally with dry nitrogen. Storing our reserve duoplasmatron ion source at 40° C under such dry conditions reduces contaminants in our oxygen primary ion beam.
Flat-bed Sample Scanner: Epson 4180 Photo
Certain SIMS applications are best performed interactively, where the results from a current measurement may influence which locations on the sample are subsequently selected for analysis. The Cameca point-logger software allows images of a sample mount (typically .jpg format) to be calibrated against the 1280-HR sample stage. After having been calibrated, it is possible to use the SIMS' mouse courser to click on the scanned image to move the sample to the next region of interest. Our flat bed scanner produces images with 2 µm pixel resolution and the images can be acquired in the matter of a few minutes.
Petrographic Microscope: Zeiss Jena
Cathode Luminescence Imaging Chamber:
Other Infrastructure available at the GFZ
Electron Microprobes: The GFZ has two Jeol electron microprobes, one using a field emission electron source and the second operating with a LaB6 electron emitter. These are used both for quantitative analysis as well as imaging at the micrometer or sub-micrometer spatial scales. A specialty of the EPMA facility is the quantification of light element concentrations using large lattice spacing defraction crystals.
Scanning Electron Microscope: Section 4.1 of the GFZ operates a Zeiss Ultra 55 Plus field emission SEM. It is able to image at spatial resolution reaching down to low nanometer range and can also operate in low vacuum mode. It is equipped with an EDS and a monochromatic CL detector.
Focused Ion Beam Tools: Two FIB instruments are available at the GFZ which are capable of imaging and milling of polished sample specimens at spatial precisions reaching down to the low nanometer range.
Sample Preparation Facilities: The GFZ has a wide spectrum of sample preparation laboratories capable of working with nearly all solid geomaterials. Specifically within Section 3.1, we have facilities dedicated to rock crushing and milling, mineral extraction and thin section and grain mount preparation.
High Pressure Development Laboratory / Machine Shop: The SIMS Laboratory works closely with the High Pressure Development Laboratory within Section 4.3. This cooperation not only supports the smooth operation of the SIMS facility but also uses the HPDL's expertise in CAD-based designing of new parts in conjunction with a wide variety of both computer controlled and manually operated machining tools.