XRF Wiki
Welcome to the XRF Wiki. This Wiki is a repository of information contributed by members of [email protected]. Members can view and edit the pages. The pages are currently not viewable by the public. The pages below represent a rough overview of the technology and techniques associated with X-Ray Florescence Spectroscopy as well as serving as a place for members to organize the spectra that they have contributed to the forum.?
As a starting point, the pages will be populated by information taken from member posts from the past few years - with references/attribution. Perhaps in time, these pages can be edited by members to make them more complete and less choppy. Members can also edit this page, making the structure of the content more organized.?
Pages can contain information about a particular topic, links to relevant resources (such as manuals, research papers, etc.), links to relevant forum discussions on the topic, book titles, or anything that might be useful.
What follows is very much a work in progress.
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Adding to the Wiki
For those unfamiliar with the Wiki phenomenon, it is basically a user editable encyclopedia. The idea is that there are pages with different articles, which the user can read and also choose to edit if desired. If a piece of information is incorrect, a link outdated, or the presentation choppy or unclear, the user can just click "Edit Page" at the bottom and then fix the mistake. There is also a "Page History," so if you a user were to make a mistake or maliciously destroy a page (which wouldn't happen here) an editor can come along and restore the page to a previous version.?
If you have used MediaWiki (the engine that runs behind the scene of Wikipedia.org) you will be familiar with a certain style of creating an article. There are tags that one uses to change the formatting of the parts of the article. The Wiki on Groups.io uses a different background engine and so the standard MediaWiki syntax does not apply here. Rather, the page is edited using the same tools as one would use to compose a message on the forums. If you are a programmer or someone who likes using the tagged syntax directly, you can access the underlying page source code, be activating the advanced editing toolbar (the icon with three lines on the far right of the basic toolbar) and then clicking on the source code icon <> on the far right of the Advance Editing Toolbar. You will immediately notice that the underlying source code is HTML. Most things can be done just by using the various icons, but advanced features like table can only be implemented by manually writing the source code. (Although there are website available that will generate the source code for you through a graphical interface.)
Here are some useful resources from Groups.io:?
Wiki Guide for Users and Editors
Message Composition Tips and Tricks
Overview of XRF
X-Ray Florescence vs. X-Ray Diffraction
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Hardware
This section describes the hardware used for XRF. We will describe the basic theory of operation of each stage in the processing tool chain and then present different commercial systems that are available as these systems are often integrated together.
[Editor note: General theory needs to be in an independent page separate from specific manufacturer information.
[Editor note - question: Should this be arranged by category, e.g detectors, preamps, etc or by manufacturer with the manufacturers product line on one page. Perhaps it's best to put a list of products with theory but the details of the products on a manufacture page...]
Detectors?- what's available, theory of operation, tradeoffs
Detector Cooling?- keeping detectors cool to avoid thermal noise and keeping the TEC from overheating
Preamps?- theory of operation, brief summary of what out there (and what not to do - such as trying to use a PMT preamp for a SiPIN diode...)
Pulse Processing Theory - high level overview of the stages of going from detector pulse to channel peaks on the computer
Commercial Systems - many commercial systems are integrated so it seems to make sense to present, for example all Amptek products together. [question: are their other affordable integrated systems besides Amptek?]
Amptek XRF System
Activation Sources - what do you use to make the sample fluoresce (that's within the amateur budget and doesn't require special licensing)
Software
- Device Control Software - what do you use to collect the data from the detector system
- XRF Analysis Software - what do you use to analyze the data, especially for quantitative measurements (composition percentages, thin film measurement)
- Free Software Tools
Note: there may be software packages that possess some or all of these characteristics.
Materials Spectra
Metals Spectra
Historic/Archeological Spectra
Reference Materials Spectra
Household Objects Spectra
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Resources
Videos
Articles
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Non-XRF Techniques
Gamma Spectroscopy
Raman Spectroscopy
FTIR - Fourier Transform Infrared Spectroscopy
Atomic Emission Spectroscopy
Inductively Coupled Atomic Emission Spectroscopy
Spark Emission Spectroscopy
Atomic Absorption Spectroscopy
LIBS - Laser Induced Breakdown Spectroscopy
Photoacoustic Spectroscopy
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Re: Small Sample Size XRF with low power (OTHER) excitation
12 hours in to the TXRF run:
Pb still present of course, we will attend to that and other details subsequently. Ag- Well formed Ka and Kb peaks. Interference from exciter- detectable but nil- not a problem with this Total Reflectance (of exciter beam) XRF. Geo |
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Re: Small Sample Size XRF with low power (OTHER) excitation
Phase II
Now moving on to OTHER excitation. Transferring our new-found technical knowledge to other sources of excitation, basically starting all over from the previous TUBE tests. First up- AmX1? Amptek Si-PIN 25mm^2 NO Collimator, but a Kapton safety cap. Source pointed straight up, sensor is at 90 degrees to the source beam. Sample intersects the beam at 45 degrees. Pretty much a standard setup, to establish a baseline. Geo |
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Re: Small Sample Size XRF with low power (tube) excitation
¿ªÔÆÌåÓýGood view of the setup. That really is a small angle. Dud ? From:
[email protected] [mailto:[email protected]] On
Behalf Of GEOelectronics@... ? Paper Sample Holder MKIII |
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Re: Small Sample Size XRF with low power (tube) excitation
Paper Sample Holder MKIII
Smaller disc, kept bigger viewing hole, reduced sample size again, kept spacing between sample and sensor collimator. Sample a maybe 1 or 2 square mm piece of 0.998% silver metal, .004" thick. 1mm beam set to 37kV for 30 seconds..One picture shows results and views of the important setup features. Geo |
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Re: Small Sample Size XRF with low power (tube) excitation
Follow-up on the paper sample holder calibration samples idea.?
The paper disc was made bigger as was the hole in the middle. For a this one I wanted a Silver metal sample. Punched a 1/8" disc of 0.998% Ag 0.004" thick as the sample and attached it to Scotch tape "window" that covers the hole from the rear leaving the sticky material inside the hole. No front cover placed over the sample "dot" at this time. The sighting is improved as expected, while the scans, for all practical purposes, remained the same as they were before when using a much larger postage sized sample of the same material. Geo |
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Re: Small Sample Size XRF with low power (tube) excitation
For the last scan (previous post), the sample size was dramatically reduced from a few milligrams to just a few dust particles.
Pick any 1mm circle near the middle of the watch-glass-"sample holder" we used.to see the orders of magnitude reduction we're analyzing. It's a small portion (1mm) of the dust clinging to the watch glass after returning the hematite flakes to their storage container. Geo |
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Re: Small Sample Size XRF with low power (tube) excitation
Deadtime taken care of.
Changed sample holder and sample, lowered current., increased count time to 10 mins. We were overdriving everything, too big an entrance hole, too big a target! Will change from 25mm^2 sensor to a 13mm one for this setup only. Right now here is the first run with the original setup and new sample holder, sample and settings. Still higher rates but deadtime is not an issue now. Comments welcome. Geo |
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Re: Small Sample Size XRF with low power (tube) excitation
Next up is the HV being varied and everything else remaining the same.
Obviously the filter is messing up the expected output, as we suspected. A few observations- No signal at all below 15kV or so Therefore .I did a series of 1kV steps to find where the edge of the filter was, and again as expected it is right around 20 kV. Over 20 kV the increasing the HV did increase the counts recorded, but not in a linear fashion that I could fine. Not to mention the increased noise on the pattern. Deadtime jumps from zero to 99.8% almost instantly when the correct angles are achieved. Turning down the beam, either the HV or current does not alter that at all, only moving the sensor farther away starts to reduce it, but that won't be the answer.. For this particular sample the optimum setting for the exciter was somewhere around 30kV and 30 uA. That seemed to give adequate peak height without undue noise. Data ..mcas and scan pic showing lab setup attached |
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Small Sample Size XRF with low power (tube) excitation
The sample is Rainbow Hematite, weight 5 mg. Longest dimension is about 1mm, thickness is a fraction of that. Like a flake. It was a free sample from a supplier, as shown in the watch glass, a total of 0.065g, from dust to small flakes.
The sample holder today is a punched disc of cardboard (3X5 card, extra heavy) with a central hole punched to hold the sample. A piece of clear Scotch tape covers the hole from the back side and onto the sticky side of that we affixed the sample, in the middle of the hole. Over the top of the sample is a cover layer also of clear Scotch tape. The idea was to be able to see through the sample holder to get it positioned over the 1mm hole in the collimator. It works but next time I'll? make the hole in the middle larger for better viewing through it.. The picture is of the sample holder ready to be positioned in the XRF tester stand.? I can report that the holder works fine at the energies we are using for this test series (Fe Ka1 @ 6.40keV,? Fe Kb1 @7.06keV). We are testing the equipment assembled into our current XRF demonstrator. as well as the optimum level of energy in the beam required to produce specific results. On the beam port is a 1mm shielded collimator, on the detector, an Amptek Si-PIN, is a tungsten collimator with a 1mm hole for a window. Geo |
