The Michael J. Drake
Electron Microprobe Laboratory
University of Arizona

User Information (FAQ)

How do I sign up for time on the microprobe?
How does the web based signup work?
Who does the calibrations for WDS analysis?
What do I need to know (or tell Ken) before my session in order to calibrate for WDS?
How do I find my analysis spots?
When can I carbon coat my samples?
Who does the analyses?
What time should I show up?
What time do I need to be finished?
How do I get my data?
How are the quantitative analysis results formatted?
What is the x-ray map format?
When should I pick up my samples?

Arranging for Instrument Time

New users who have not used the microprobe before should contact us to discuss their projects and arrange for time on the instrument.
Experienced users should sign up for time using our web-based signup procedure.
People who need to schedule more than two weeks in advance because they are traveling from out of town to use the microprobe should contact us to arrange for time.

Web Signup

The web based microprobe signup for experienced users (new users and visiting users see the above paragraph) is held every other Monday beginning at 8am. It is open for 48 hours and allows you to sign up for up to two days during the two week period that begins the following week. The signup page, the date of the next signup, and the period covered by the signup are displayed here.
If there is still time open after the signup closes (Weds. 8am) you can sign up for the open time (regardless of how many days you are already signed up for) by contacting us.
You'll need a password in order to sign up. You can get the password by contacting us.
If you need help calibrating or otherwise using the microprobe during your probe session, please try to sign up for a non-holiday weekday. If that is not possible please contact Ken Domanik either before signing up or as soon as possible afterwards to check if Ken can be available on the day or days you are interested in.

Calibration and Calibration Training

If you plan to do quantitative (WDS) analysis you can either have us calibrate for you or (after receiving the appropriate training) calibrate the instrument yourself. Either way is acceptable and the choice is completely up to you.
Most people choose to have us calibrate because it allows them to concentrate their time on collecting data. However students majoring in fields in which electron microprobe use is routine (e.g. geosciences, meteorite science, physical anthropology, etc.) should consider getting at least some experience in calibrating the machine themselves.
If you would like training in calibrating the machine, let us know before your probe session (or sessions) and we will cover it as we prepare for your analyses on those days.

Calibration Planning

If you are going to calibrate yourself, the following list contains some questions that you'll need to answer in order to do it.
If you would like us to calibrate for you, and it is a new calibration¹, we also need this information. Please contact Ken Domanik before your scheduled probe session (an email the day before your probe day is best) and provide as much of the following information as you can. If we need additional information or clarification we'll contact you. The more of this information you can provide in advance, the faster we can get you going collecting your data.

Data needed for calibration:

What elements you plan to analyze for and what type of minerals or materials these elements are contained in (e.g. anhydrous silicate minerals, hydrous silicate glasses, chrome alloy steels, etc.)?²
What is the general composition (roughly) of these matrix minerals or materials.³ (This information is needed primarily to determine if peak or background interferences may be present).
Are the minerals or materials of interest small (< 6 痠) in size.
Are any of the elements you plan to analyze of more importance than the others (e.g. as in geothermobarometry) or do you need to know their concentrations accurately at trace levels (< 0.1 wt%)?
What are you trying to determine (e.g. general composition of all phases present, trace Ni partitioning between metal and olivine, age dating of monazite, Sb content of archaeological artifacts, etc.)?

¹If you have run the same type of analyses on our microprobe before, specifying "same calibration as last time" or something to that effect is usually sufficient.
²Some types of analyses are so common, particularly for geological and meteorite samples, that we can guess what elements you need and make any necessary adjustments during your probe session. For example, general analysis of all major silicate minerals in a rock section (standard silicate analysis), general analysis of all major metals and sulfides in a chondritic meteorite (standard metals and sulfides), etc. In cases like these a brief specification (e.g. standard silicates) is generally enough.
³In some cases, especially for a completely unknown sample, it may be necessary to actually get the sample on the microprobe in order to answer the above questions. However a good guess prior to starting is usually better than nothing.

Analysis Planning - Sample Navigation

The optical and BSE images on our CAMECA SX50 have a relatively small field of view. If you intend to analyze specific areas on a complex sample such as a rock thin section, it is often very helpful to have some type of map or guide handy indicating the location of the areas you are interested in. Circling the areas of interest with a felt tip pen and connecting the circles (making sure not to get fingerprints on the surface in the process) or marking the locations on a large scale picture made by optical microscope, scanner, or BSE map all work well for this purpose.

Carbon Coating

To get the best quantitative analysis results, we encourage users to carbon coat their samples using the Denton 502A carbon evaporator at our facility.
Carbon coating times are currently 10 - 15 minutes. However, coating time can vary significantly and it is best to budget 30 - 40 minutes for each set of samples coated.
Our carbon cater can accommodate 2 standard thin sections or 4 one inch round samples at a time.
If you only have one or two samples, we can usually coat them the morning of your probe session without holding things up too much. However, you can coat your samples any time before your probe day that's convenient for you provided the carbon coater is not in use.
Old carbon coats often produce bad analyses. If your sample was coated over a month previously it is probably best to remove the old carbon coat and recoat the sample.

Hours and Procedures

We encourage microprobe users (particularly students) to perform their own analyses, this is the default mode of operations for academic users of our lab. Training and full-time assistance are available any weekday unless otherwise specified. By special arrangement, we can perform the analyses in special cases (usually outside users who can't physically make it to the lab) for which we typically charge an additional fee.
You should come to the lab around 9am. If you are calibrating for yourself you will probably want to come earlier (any time after 7am).
If you are setting up programmed analyses, maps, etc. to run overnight (as most people do), and someone else is scheduled for next day, please make sure your analyses will finish by 7am.

Collecting your Data

For overnight runs, we try to have the data posted by 11am the next weekday.
The easiest way to collect your data is to download it using a SSH ftp program. Contact Ken Domanik for login and password information. If you use a PC type computer, we can also supply a small that will work for this purpose.
You can also get your data by bringing a flash drive or CD to the lab.

Quantitative Analysis Data Format

Typically you will receive 4-5 report for each analysis label. All reports have a .asc extension and are in tab delimited format for importing into spreadsheet programs.
The reports types are usually:

full - All available information about standards and calibrations as well as the results, standard errors, etc. for all analyses. Note: beam size is not recorded and should be noted separately by the user during their probe session.
el - Element concentrations in wt% for all analyses.
ox - Oxide concentrations in wt% for all analyses. Only available if oxygen was calculated by stoichiometry.
det - Element concentrations in wt% and CAMECA calculated detection limits (95% probability) for all analyses.
at - Atomic percent of each element. Note: not recommended as analyses are normalized to 100% introducing some degree of error.

Other types of analyses (e.g. trace, geo, etc.) will have different style reports.
Other custom reports are available or can be developed on request.

X-ray map format

X-ray maps are in tif format.

Picking up Your Samples

The lab does not have facilities for long-term sample storage. Please take your samples with you when you are done with your probe session. In the case of overnight runs please come and pick up your samples as soon as possible.
Be advised that we take no responsibility for samples left in the probe lab after your probe session except by prior arrangement.

The Michael J. Drake Electron Microprobe Laboratory University of Arizona