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
And here's the finished 30 minute run of the 45 degree angle sample run. With no beam shaping or collimators we were getting 92% deadtime.
Now we re-adjusted the angle for TXRF, this may take a while to get it working, if indeed it does work.
EDIT It does work.?The good and the bad both. Both .mca's attached, one (now correctly labeled) is the 45?degree?target and the other one is the full TXRF mode. The latter shows significant reduction in 59.5 and Np X-Ray interference, but a boatload of? XRF for the added Pb shield. This we can deal with. The main thing is the reduction of actual exciter interference and still enough signal from the sample that can be increased with various means.
Now the real work begins, testing those "various means".
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
Good view of the setup.
That really is a small angle.
Dud
?
?
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
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
Same setup and variable as preceding post. This time the sample is Mo metal "stamp". Note: The deadtime is better controlled? by moving sensor away from sample. In a permanent setup IN AIR- it would be better to leave it close but have a smaller diameter entrance hole.
Samo-Samo.
Note there are two possible sources for the tungsten L line contamination, one is of course the
W collimator on the sensor, the other is the W target in the exciter tube. Normally when using 45 degree excitation and no collimator of the sensor, it is not noticed.
Geo
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Re: Small Sample Size XRF with low power (tube) excitation
Followup-1 replaced Mo-Re alloy with a 1/4" X 1/4" flat piece of thick Mo metal. Same setup as Mo-Re, namely 37kV 4.7 uA and 300 seconds.
This time there were 3 identical test runs, the changes to each were only in the area of lower level Discriminator settings. Might as well kill 2 geese with 1 stone.
Normally the auto threshold set with no source for this sensor comes back with around 0.58% as the setting. I have been recommending to users of my GEO-1-2-3 to add 1% to that number.
These 3 tests show why I did and still do recommend that.
One is with LLB set to 0.0%, the next to the nominal 0.58% then to my empirically derived 0.58 + 1= 1.58%.
To my eyes the ONLY difference is in the unusable and interference/ confusing left hand noise, what we call "electronic noise". It is all below 1 keV and Si-PIN don;t even work in that area so why bother showing it in every scan?
Load all 3 scans, switch back and forth to view this effect, or stack and SHOW them all at once.
2 birds + 1 myth = Busted
Next post will be of Mo metal "stamp" which is identical in size to the Mo-Re alloy "stamp" just for the record.
Geo
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Re: Small Sample Size XRF with low power (tube) excitation
Geo,
To tell what¡¯s going on in
the real low energy region you need a lot of counts to separate noise from
closely spaced elements that may be separated by 100ths of a keV. Mo is 2.293, 2.395
while S is 2.308 so they are 0.015 keV apart and your channel resolution is
0.030 keV. You¡¯ll need confirming lines to be certain, but with the high
percentage of Mo I¡¯d go with Mo. ?Spikes are the jagged single channel noise on
the side of what should be a nice smooth Gaussian peak.
Your mca file has all that
data in it open it with note pad and look at the very bottom.
Fast Count: 6272
Slow Count: 2176
GP Count: 0
Accumulation Time:
300.000000
Real Time: 300.294000
Dead Time: 65.31%
HV Volt: 188V
TEC Temp: 229K
Board Temp: 46¡ãC
<<DPP STATUS
END>>
And I wonder what that 65%
is due to although it may be the LLD is set at 0, but I do see the real and
live time fighting pile up so something is getting noise in there. Try setting
the LLD .cut off below 0.74 keV
GAIN - 3
THRESHOLD - 0
LIVE_MODE - 0
PRESET_TIME - 0
LIVE_TIME - 104.070000
REAL_TIME - 300.000000
START_TIME - 02/03/2021
16:08:09
You¡¯re almost optimized except
for the darn x-ray tube cut off at 15kV
Dud
?
?
" While Sulfur is at 2. so is Mo La1,2.and in that you
have a lot of Mo I¡¯d have to call this Mo La1,2."
Will
check that tomorrow against a Mo only stamp with same setup.
" counts are closer together yet it still has a 65%
dead time"
How are
you getting 65%> There is zero deadtime showing on the readout, right?
Can you
point out the spikes on the peak you mentioned?
The 27kV
was set by adjustment, as was the current. By that I mean they were adjusted
while running, then the setting decided, and only then the real test run was
started. Don't forget, there is no energy in the beam to speak of anywhere
below 20 or so kV. The internal filter knocks that way back. Only the vestigial
tungsten L Lines, and those are greatly attenuated. I posted? a test
series only a few days ago with that data.
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Re: Small Sample Size XRF with low power (tube) excitation
" While Sulfur is at 2. so is Mo La1,2.and in that you have a lot of Mo I¡¯d have to call this Mo La1,2."
Will check that tomorrow against a Mo only stamp with same setup.
" counts are closer together yet it still has a 65% dead time"
How are you getting 65%> There is zero deadtime showing on the readout, right?
Can you point out the spikes on the peak you mentioned?
The 27kV was set by adjustment, as was the current. By that I mean they were adjusted while running, then the setting decided, and only then the real test run was started. Don't forget, there is no energy in the beam to speak of anywhere below 20 or so kV. The internal filter knocks that way back. Only the vestigial tungsten L Lines, and those are greatly attenuated. I posted? a test series only a few days ago with that data.
Geo
From: "DFEMER" <dfemer@...> To: [email protected]Sent: Wednesday, February 3, 2021 6:26:50 PM Subject: Re: [XRF] Small Sample Size XRF with low power (tube) excitation
Geo,
Lookin' better, PUR is on
and fast/ slow counts are closer together yet it still has a 65% dead time and
it? still has some low energy noise below 0.62 keV that could be taken out. Getting
rid of that will increase the number of valid counts you¡¯re getting per unit
time. A gain of 2.9 in the number of valid counts for the 300 sec count.
The data are still noisy
with no defined baseline and spikes still showing on the peaks but still
usable.
While Sulfur is at 2. so
is Mo La1,2.and in that you have a lot of Mo I¡¯d have to call this Mo La1,2. ?The
¡°P¡± at 2.0 is not on centered on P 2.0 but shifted 5 channels back to 1.87.(this
is why you max the gain resolution to be able to see this stuff) this peak is under
counted and unresolved so to say anything the ¡°peak¡± looks like it could be Mol
at 2.0 trying to come up, but it¡¯s too under countered to say anything about it
on the record.
The Mo binding energy of
Mo is 20keV so a beam 1.5 x that or 10 kV above is about optimal so that¡¯s set
perfect at 27kV, but with that amount of Mo anything would work. Try a shot at 10
or 15 kV and see if 1.8 and 2.3 become better resolved with a better number of
counts
Dud
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Re: Small Sample Size XRF with low power (tube) excitation
Geo,
Lookin' better, PUR is on
and fast/ slow counts are closer together yet it still has a 65% dead time and
it? still has some low energy noise below 0.62 keV that could be taken out. Getting
rid of that will increase the number of valid counts you¡¯re getting per unit
time. A gain of 2.9 in the number of valid counts for the 300 sec count.
The data are still noisy
with no defined baseline and spikes still showing on the peaks but still
usable.
While Sulfur is at 2. so
is Mo La1,2.and in that you have a lot of Mo I¡¯d have to call this Mo La1,2. ?The
¡°P¡± at 2.0 is not on centered on P 2.0 but shifted 5 channels back to 1.87.(this
is why you max the gain resolution to be able to see this stuff) this peak is under
counted and unresolved so to say anything the ¡°peak¡± looks like it could be Mol
at 2.0 trying to come up, but it¡¯s too under countered to say anything about it
on the record.
The Mo binding energy of
Mo is 20keV so a beam 1.5 x that or 10 kV above is about optimal so that¡¯s set
perfect at 27kV, but with that amount of Mo anything would work. Try a shot at 10
or 15 kV and see if 1.8 and 2.3 become better resolved with a better number of
counts
Dud
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Re: Small Sample Size XRF with low power (tube) excitation
Uh oh.
Can we ask everyone to
chip in to delay the issue till we find an alternative? What would that take?
Dud
?
?
?
"
Geo,
When you reply can you
please leave the post attached Its hard to reply without knowing which we¡¯re
replying to.
I think this post was what
you¡¯re referring to.:"
Doing so has run up our
Groups.io to the point that no more attachments are being accepted. Twice today
I had to delete messages so I could post my latest findings.
Our next step is to move
to XRF-Page-2 like we had to do on Yahoo groups years ago. We evidently get
only 1GB of memory free. It might be the XRF WIKI is taking up space? As it
stands this list is ready to crash.
Geo
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Re: Small Sample Size XRF with low power (tube) excitation
Mo-Re alloy "stamp" .002" foil, with slight corrosion on one side.
27kV @ 4.7uA 5 min. Beam and sensor collimated to 1mm circle. We are analyzing 0.785 mm^2 of the sample.
Sensor moved away from target by 1/4" to lower count rate. Sulphur and Phosphorus peaks assumes to be due to the corrosion. LL Threshold set by auto-program.
Geo
.mca only attached.
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Re: Small Sample Size XRF with low power (tube) excitation
" Geo, When you reply can you please leave the post attached Its hard to reply without knowing which we¡¯re replying to. I think this post was what you¡¯re referring to.:"
Doing so has run up our Groups.io to the point that no more attachments are being accepted. Twice today I had to delete messages so I could post my latest findings.
Our next step is to move to XRF-Page-2 like we had to do on Yahoo groups years ago. We evidently get only 1GB of memory free. It might be the XRF WIKI is taking up space? As it stands this list is ready to crash.
Geo
|
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
Here is the series of .mcas I ran keeping the HV and current th same, but varying the Peaking Time to see if that had an effect on the deadtime.(it didn't)
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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Re: Small Sample Size XRF with low power (tube) excitation
This first data set are the individual test runs with the beam kV set to 30 kV for all tests, varying only the current of the beam to find the relationship between current and peak counts.?. We have infinite adjustment of the kV and current within the limitations of the tube and power supply (50kV @ 100uA)
The "Beam" refers to the thermionic electron beam within the exciter tube.? >99% of that energy is converted into heat when the beam strikes the target at the other end of the exciter tube. Of the <1% that is converted to photons, only a tiny fraction exits the tube in the correct direction to pass through the exit window, and in that path for this tube there are non removable filters. For the tube in this lab setup, the filters limit all energies below approximately 20keV which included the tungsten target's L Lines, and the power supply's maximum kV precludes any tungsten K lines.. Therefore the voltage threshold is much higher than on a non regulated tube. For practical measurements we must start at 20 kV and that pretty much eliminates the K-edge tuning range to 20+ to 50 keV. Our next lab series will be using a copper target tube with no filters, therefore strong Cu K lines carry much of the total energy available..
This first data set are the individual test runs with the beam kV set to 30 kV for all tests, varying only the current of the beam to find the relationship between current and peak counts. . We have infinite adjustment of the kV and current within the limitations of the tube and power supply (50kV @ 100uA)
Beam currents as low as 3.75uA will give readable results in the set test time of 20 seconds.
The following chart shows the levels and the peak counts obtained.
kV= 30 all tests.
T= 20 seconds, all tests
Current (uA)? vs? Peak Counts (area under peaks can be calculated by using the attached .mca files)
? ? ? ? ? ? ? 3.75? ? ? ? ? 22
? ? ? ? ? ? ? 5? ? ? ? ? ? ? ?37
? ? ? ? ? ? ? 7.5? ? ? ? ? ? 61
? ? ? ? ? ? 10? ? ? ? ? ? ? ?77
? ? ? ? ? ? 15? ? ? ? ? ? ? 118
? ? ? ? ? ? 20? ? ? ? ? ? ? 156
? ? ? ? ? ? 25? ? ? ? ? ? ? 199?
? ? ? ? ? ? 30? ? ? ? ? ? ? 236
? ? ? ? ? ? 40? ? ? ? ? ? ? 319
So it can be seen that the relationship, once a threshold is reached, somewhere between 5 and 7.5 microAmperes), the relationship becomes linear.
A doubling of current doubles the peak count.
With a fixed HV, doubling the current doubles to power of the beam.
This is in compliance of Ohm's Law of P= IE
Geo
? ? ? ? ? ? ? ? ? ? ? ?
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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 
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