Using the 2-D Wire X-ray Detector

     Basics

There are basically three parts to the system. Detector, Driver, and Computer. The detector is in the enclosure, the driver is to the left, next to the computer, which is dedicated to the system and will soon be networked.
The detector has a bias setting on top. It is set to "9" and should be left alone; any change to the bias is now done in the software.

The driver has three buttons:

       BIAS     ...    SOURCE SELECTION    ...     ON/OFF

The power should be left on, or allowed to warm up for a half hour. The source selector should always be set to Auto. The bias is the switch you must turn off ANY time you need to touch the detector or anything near it.

The computer runs windows NT. The software you need to run our system is GADDS offline

     GADDS Software

To collect an image, start the GADDS offline software, go to [Collect] in the menubar, and select [Add...]. It will give you a window to choose exposure time, etc.
To save an image, go to [File] and select [Print]. Then print to a file. I choose grayscale .tif so that it translates to Macs. There is also a translation program, but I have yet to see how, or if, it works.

The monochromator works well with enough intensity that the straight pipe shouldn't be needed. In case that statement is wrong, like for a thick/dense sample, a simple set up is shown here to get full beam intensity. You might want to add a Ni filter foil to clean up the Cu K-beta.

     Do's & Don'ts

Don't force any of the screws. Copper and Aluminum are very soft compared to the steel screws.

Don't overtighten the "shutter pressure rod" (detail C). It is there to hold the copper column against the manual shutter disc (detail D), which should seal flush to be safe during the alignment procedure. The column stand only needs a bit of pressure to hold the shutter open.

Be careful attaching a sample to the sample holder (detail B), it is lead -very soft- and the hole is approx. 0.7 mm- don't dent it or clog it, or you will have to make another.

Adjust the maximum intensity by changing the three setscrews near the sample. Leave the other three near the source alone once they are centered on the source.

Copper collimator is just a simple tube, it is set up at a distance of 120 mm from source to sample.

I tried to make all the holes I tapped ¹/₄-20 thread. The exceptions are the adjuster thumbscrews (metric 1.5-10 mm) and the sample holder setscrew (?-?, ³/₃₂ allen hex.) The Collimator set screws use a ¹/₈ allen.

     Startup Alignment

The last person to use the detector should have left it in working order, but I wouldn't bet on it. Regardless, check the placement of the beamstop using a setting of 40 kV, 1 mA and the Zr foil over the end of the sample holder and collect for ONE (1) second. If you can't see any intensity upon collection, make sure that the shutter is open and the bias is on, and if you still can't see any, turn up the current to 5 mA. Repeat with 10 and 20 mA, then collect for about 20 s. If at any time the beamstop is visibly centered on the stop, move the stop by bending the arms (Sorry, that is the best under the given circumstances) then begin again at 40 kV, 1 mA, and 1 s. This may sound tedious, but it isn't, these are collections times well under a minute, and the alternative is a burnt out detector. Once it is in line, there shouldn't be any reson to move it, so will be good for you and the next guys untill someone changes something.
    N.B. I tried to get the bed lined up as well as I could withthe beam, so moving the detector and beamstop shouldn't put anything too far out of alignment. And, yes,you still need to check the intensities from the start: 40 kV, 1 mA, and 1 s.

     Running

Once the beamstop is set, a real experiment can be done, including a background airscatter run. in the software, start collecting an image. We have preliminarily found that a visible pattern shows in about 5 seconds, but statistically smooth will take more like an hour.

     Shutdown

This is easy. Make sure to do all these, and in order

• Bias Off
  
• Shutter closed
  
• current down
  
• voltage down
  
• Off lever (red)
  
• replace brass and aluminum plates CAREFULLY
  
• Clean up any mess
  
• Backup your files
  

     Overall Alignment

Requires bypass of safety locks

This list may not be perfect, so THINK about every step you take.

This is for when the monochromator was removed and needs to be put back on. It took me half a day, so don't expect too much less time.

Bias should already be Off

If the base plate needs to be put back to the 26° angle, remove the detector from the dovetail rail
Remove the plate from the straight setup (just two small 6-32 screws)
Attach the monochromator to the source base with the 5mm-0.8 screws being careful to get the shutter disk inside the square cutout.
Attach the base plate to the source post at 26° (1 screw, 6-32)
Make sure the collimator tube is clear of the monochromator
Put the lead shield (with the hole) over the shutter/monochromator gap
Make sure the lead glass fluorescent indicator is on the output hole of the monochromator.
Tape up the mechanical switches at the top of the doors
Close doors and turn on beam to 40 kV, 10 mA.
Open shutter
If you think the angle is still set correctly on the monochromator, skip to the next step with the *, if not, continue
Turn thumbscrew to get graphite crystal to 0°
Set the output angle to zero (6° on the top scale, don't ask me.)
Turn the tiny setscrews on the miniature dovetail on the monochromator to change the position of the crystal until the glow is a half circle - the crystal is centered. Turn the thumbscrew to set the 13.53° crystal angle
Turn the output hole to 27°
*Check the intensity by turning the thumbscrew at the back of the monochromator a couple degrees and maximize the intensity. Readjust the output angle as needed.
Close the shutter
Remove the protective lead glass indicator and bring the column up to the output hole
Clamp the stand firmly and set the angle with the "shutter pressure rod" Don't move it again if you can help it.
Adjust the three setscrews so that the copper tube is in line with the output hole
Mount the Detector very carefully
Eyeball the angle to the Detector
Close doors and Remove tape from safety circuit switches and set up for regular data collection
Hang the Zr foil over the end of the open end of the copper tube and take a 40 kV, 1 mA, 1 s pattern with the detector to check for rough alignment of tube and beam
Adjust the OTHER three setscrews to bring it in line. I put a post-it note corner on the computer screen at the center. You'll have to move the beamstop
Put the sample holder on, set screw on top, and Zr flim over the end and take another pattern to check for alignment. If nothing is visible, it is either the beamstop is well aligned, or more likely the sample holder isn't.
Adjust the 3 set screws near the sample holder until the aperture is correctly in the middle of the beam, as always, at 40 kV, 1 mA, 1 s with the Zr foil.
Align the beamstop
Go to alignment sequence above

These setups are mostly going to be used for fiber patterns. The detector can possibly be moved to the Furnas box (without vacuum, back plate removed) for SAXS

Manual for the Detector is in the Martin lab. Two users manuals, one for the system, one for the software.

Manual for the monochromator (English version) is stored in the Martin lab, and one copy should be with Anne Huber (2220 H. H. Dow)

Cullity, B. D., Elements of X-ray Diffraction, Addison Wesley, Reading, Mass, 1978.

Vainstein, B. K., Diffraction of X-rays by Chain Molecules, Elsevier, Amsterdam, 1966.

Gunier, A., Fournet, G., Small Angle Scattering of X-rays, John Wiley & Sons, London, 1955.

Baumg, P. K., "Electr"J. Col Sci.,36 (1), 71-79, (1971).