Related RG & Linkedin discussions:

https://www.linkedin.com/groupItem?view=&gid=2683600&type=member&item=5939654519540445188&trk=groups_most_recent-0-b-ttl&goback=.gmr_2683600

https://www.researchgate.net/post/Bloody_Murder_Why_is_there_nearly_such_a_visceral_response_to_any_disruption_to_alignment_of_existing_diffractometers_by_XRD_users_technicians#54692cf7d039b1c7528b45e3

Do you have a twist tube, a glass slit, a collimeter aligner ( a holder with a rod sticking up with a small hole in it) and a divergent secondary  slit assembly availible?

I'm unfamiliar with such tools except "divergent secondary slit assembly". Would you please post some photos and other details when convenient. Thanks!

Would such information be available on the Rigaku web site or other supplier web sites for such contraptions?

with a twist tube you can change between line focus and point focus by rotating the tube 90 degrees a glass slit is two pieces of glass mounted on top of each other, between them is a narrow slit. those are usually suplied when you buy your diffractometer. The collimeter aligner is also ussually there. 410 is the collimeter aligner 411 is the glass slit

So how does one use the above apparatus to achieve the alignment objectives proposed earlier?

1. The collimator aligner gives you a point on the diffractometer axis, I suppose. Then what? BTW do you continue the alignment with the 0D point counter at this point or do you switch to photo film?

2. What is the purpose of the "glass slide" tool? Is the slit the gap between the two glass plates? I don't quite understand the purpose of gluing 2 glass plates together yet:-) Will learn.

The glass slit har a small opening between the plates.

 #1 Go to line focus, plug the glass slit at z=0 at the sample holder, attach div slit assemply to the detector and open slit fully. set detector to 0d. perform a rocking curve scan (theta scan) from -1 to 1. detector at 0. remember to put in an absorber Cu or several layer of Alu foil. Now adjust the tilt screw on the source to max intensity by repeated scans This can be trcky, since the tilt alignment very often is "sloggish". When you reach max intensity, operate the translation screw ( if availible ) the same way to max intensity. This will set the beam to your desired  eucentric position.

#2 go to point focus with polycap ( if availible ) and collimeter, plug the collimeter aligner. perform a detector scan -1 to 1. adjust your collimeter alignment screws to max intensity. this will center your point focus beam to the center.

It is important, that you realign your theta/2theta position after the procedure

If this does not make sense. Try wtriting me your hardware set up

Best regards Flemming

Thanks Fleming!

Step #1: The glass plate slit ensures the "line source" is coplanar with the "z-axis". Correct? At least collinear within the size of the glass slit (gap). What is the typical "gap" between the glass plates that you use? May I assume that the bottom plate sandwich surface is placed where sample surface should be? So, the gap is  above where the sample surface would be. Yes?

Step #2: What is the typical size of the "small hole" in the "collimator aligner"? What would this approximate size be if recorded on a photo film placed at the detector surface? I mean, including any potential beam divergence. What is "polycap"? Sorry for the naivete. I intend to learn better.

A. How much time would Steps #1 and Step #2 take just to verify present alignment?

B. How much time for Step #1 from an initial "by sight" or other laser assisted alignment? Meaning from "scratch", let's say a brand new machine just installed?

C. "It is important, that you realign your theta/2theta position after the procedure". Do you mean the "zero" position or those from the standards or both?

I'm trying to ascertain these time elements for the conventional method to compare with the real time 2D imaging techniques we recently used to verify alignment of a Bruker D8 Bragg-Brentano setup. I've never suffered through the alignment procedure with a point counter (0D) or a LPSD (1D). I went to photo film instead in the past before real time 2D in the mid 1980's. I'll be glad to share the information to help us all. Real time 2D XRD is a lot more precise, unambiguous and FUN! Cost effective high resolution "stand-alone" attachments are available for most existing diffractometers. I never take alignment for granted on the multitudes of XRD equipment that I've used. I always verify prior to recoding meaningful ultra-high resolution 3D reciprocal space data. Incident beam profile, background signal, sample position in the beam, standard Bragg profile, and sample data (Bragg profile) are all a part of one data set under identical conditions to minimize equivocation.

A simple check (which assumes the beam is aligned but the sample height is not): If you put your detector at 0 degrees th and the sample at 0 tth (and attenuate the beam so you don't damage your detector) you can adjust the sample height until you cut half of the incident intensity.

Yes! Thanks Larry! That's what we do, but then there are issues with edge scattering that crop up as well. However, when doing so in real time it is a piece of cake to "bracket" (rock) about the "0 position" and find the optimal "edge" or sample surface at the center of the beam approximately (within a few pixels). Now, making sure that surface is also parallel to the length of the "line source" (slit) is a different challenge altogether. How does one achieve this with a "point counter" in practice?

 "adjust the sample height until you cut half of the incident intensity". Kind of like this Larry? I'm checking if my bulky ".avi" video file will up load on to RG. 47-50 MB each. The playback quality seems to be fairly close to the original video file contrasted with the YouTube counterpart. Great!

Incident Beam AFRL 30kV,10mA: https://www.youtube.com/watch?v=m5vFgXCp_LI&feature=youtu.be

Sample surface zero alignment in incident beam AFRL 20kV, 10mA: https://www.youtube.com/edit?o=U&video_id=AkaaYcxOUAE 

https://www.youtube.com/edit?o=U&video_id=AkaaYcxOUAE

https://www.youtube.com/watch?v=m5vFgXCp_LI&feature=youtu.be

I think there should be a calibration technique "embedded" within the diffractometer apparatus, i.e. using a standard sample to narrow down the error. Then the XRD taken should include such a correction. 

You could control the right position of the sample surface on the axis (if the beam is well aligned) by setting the sample at tth=0 and measure the "profile of the beam" around th=0 with the detector (if this is possible without damaging the detector!). Then rotate the sample to  tth=180° and measure the "beam profile" again. The th-coordinate of the point of intersection of these profiles should be at th=0. The position of the sample surface should only have an influence on the intensity of the intersection point between the measured "profiles". I stop the sample alignment when the intensity of the intersection point is half of the maximum profile intensity which is measured without the sample.       

Step #1: The glass plate slit ensures the "line source" is coplanar with the "z-axis". Correct?

thats true, but it also ensures, that the beam stays at the same spot at Z=0 on your sample in the full theta range

What is the typical "gap" between the glass plates that you use?

I m not sure but I guees its around 100 Microns

 May I assume that the bottom plate sandwich surface is placed where sample surface should be? So, the gap is  above where the sample surface would be. Yes?

correct!

Step #2: What is the typical size of the "small hole" in the "collimator aligner"?

typically around 500 Microns to 1 mm

What is "polycap"? Sorry for the naivete. I intend to learn better.

a polycap is  made up of several hundred capillary glas tubes and is is to guide a point focus beam in a small divergenges. You might not have one, and it is not essential

A. How much time would Steps #1 and Step #2 take just to verify present alignment?

I can do it in an hour, but as a novice you probarbly have to practice :-)

B. How much time for Step #1 from an initial "by sight" or other laser assisted alignment? Meaning from "scratch", let's say a brand new machine just installed?

Approx. the same, do you laser pointers for the positioning?. If you have they must be set after the alignment

C. "It is important, that you realign your theta/2theta position after the procedure". Do you mean the "zero" position or those from the standards or both?

Start with the zero, do that also in the glass slit, and correct slightly with a reference if nessesary.

The method Larry suggested is often used for accurate z height determination, but as he also said " (which assumes the beam is aligned but the sample height is not):"

The method I described is a goniometer centering procedure, which will eliminate the problem descibed by you

best regards Flemming

Here is an example of flat sample surface alignment for thin films on flat substrates using "Chi" scan to maximize the XRR signal from the thin film. The trick here is to precisely determine the "zero" degree 2Theta :-)

https://www.youtube.com/watch?v=yTfKh3CGJGc&list=FL7-u3nABX4YMdHDugoPsYcA

"I stop the sample alignment when the intensity of the intersection point is half of the maximum profile intensity which is measured without the sample"

This would work if the beam was spatially uniform or at least symmetric about the diffractometer axis. Especially, using the archaic 0D technique of integrating XRD data spatially. It is more of a challenge with high resolution diffractometers & spectrometers equipped with advanced beam conditioners. In these cases, the Nano structure of the beam conditioner is convoluted on the beam as well. All 2D beams we've seen to date are anything but symmetric or uniform. Haven't done so with the Synchrotron yet :-)

• stats as of today 2/6/16 Views 968, Followers 10, Answers 13