Kratos Monochromator adjustment

This Kratos monochromator adjustment procedure is used on the Kratos Axis, 165, Ultra and Nova monochromators.

Steps involved in optimizing the performance of the Al Monochromatic x-ray source:

First, load a sample bar containing a grid alongside a clean Ag foil sample at the same height.

  1. Using the Mg source image the grid to locate the height of the auto stage that gives the best focus. Move across to the Ag foil sample.
  2. Using the Mg anode find the BE position of the Ag 3d 5/2 peak. This method requires that the calibration of the energy scale of the instrument is correct.
  3. Using the BE position obtained with the Mg dual anode switch to the mono source and begin tuning the source position in conjunction with the crystal settings as detailed below.
  4. The image below shows the mono crystal adjustment mechanism. First undo the locking screw. (Rather than just loosening the locking screw, it sometimes helps to use the locking screw as a counter drive against the micrometers to enable a finer adjustment on the crystal mechanism). Micrometer A tilts the crystal left and right moving the mono spot in the x-axis on the auto stage. This can be carefully adjusted to optimize the count rate on its own (no interaction with other parameters). Similarly, there is a tilt adjustment on the mono source that changes the source to crystal distance that can be adjusted for maximum count rate at this point.
  5. The micrometer on top of the mechanism (marked “Do not adjust” in the image) changes the distance between the crystal and the sample. (After initial factory set up …i.e. for normal maintenance procedures…anode changes etc… this will not need re-tuning).
  6. Micrometer B tilts the crystal to move the mono spot along the y-axis of the auto stage (towards and away from the dual anode source). This micrometer always needs to be adjusted in conjunction with the linear movement of the mono x-ray source itself. When the mono source position is changed it moves the refracted beam on the sample so the tilt adjustment is required to move the mono spot back to the analysis position to maximize the count rate.
  7. The linear drive on the mono source itself should be adjusted in small increments. At each new position micrometer B is used to move the beam spot back to the analysis position (by maximizing the count rate). The best method is to tilt the crystal carefully through the maximum once or twice and make a note of the best count rate obtained.

Next, move the mono source a short distance (this will decrease the count rate). Now repeat the adjustment on Micrometer B to bring the count rate to a new maximum. If the new maximum is higher than the previous one continue the process moving the source in the same direction until the new maximum is lower than the previous one. Then move the source back to the previous setting and re-optimize.

If at the start of the procedure the second maximum is lower than the first, reverse the direction of movement of the mono source and continue the process in that direction to find the best “maximum” count rate.

Once the set up is close to optimum performance more improvement can sometimes be obtained by setting up the tuning using the 110um selected area instead of large area “hybrid” mode. (Starting with the 110um aperture is sometimes difficult due to the lower counting rates).

The locking screw should finally be re-tightened in conjunction with small final adjustments of the micrometers to maintain the maximum count rate. The locking screw may push the crystal position slightly as it is tightened.

monochromator-micrometers

Installing parts using Au seals.

When installing using Au wire seals it is essential to locate the seal in the correct position. The seal should be resting snugly on the shoulder formed above the main flange.

monochromator-gasket

 

 

 

This way when the 2 surfaces come together the Au wire is ‘boxed” in and compressed.

monochromator-gasket-compressed

 

 

If the Au seal is stretched or is not a tight fit on the shoulder and therefore “hangs” over the edge of the shoulder above the flange it will be pinched as the flanges are pulled together and NO SEAL CAN BE ACHIEVED NO MATTER HOW MUCH YOU TIGHTEN THE BOLTS!

Since the seal cannot be seen after mating up the flanges the only indication of whether the Au seal is in place is the gap between the 2 flanges when they are pushed together. There should only be a very small gap between the flanges <~1mm. If the gap is larger it means the Au seal is pinched.

monochromator-gasket-incorrect

 

 

 

Water Box Maintenance

Kratos-water-box

With 15kV applied at the anode the water lines act as a conductive path to ground. The first point of contact to ground is at the outlet pipe from the solenoid valve (above the valve in the water box. (The water tube goes from there to the supply pipe on the anode). The other point is where the return line from the anode attaches to the flow switch (below the flow switch)

Kratos-anode-corrosion-points

 

 

 

 

These are the most like places for corrosion due to the voltage difference. Check and clean out or replace these fittings to bring up the flow rate.

Also remember to check the in-line filter. If there is a drop in pressure across the filter as indicated by the pressure gauges, the filter may need to be replaced.

 NEVER LOWER THE SLIDER ON THE FLOW SWITCH TO GET BACK INTO OPERATION IF THE X-RAY SOURCE HIGH VOLTAGE WON’T COME ON. OPERATING THE SOURCES AT LOWER FLOW THAN THE FACTORY RATING WILL CAUSE SHORTENED ANODE LIFETIMES.

Installing the Old Style Filaments in an 04-500 or 04-548 X-ray Source

Gallery

This gallery contains 10 photos.

Print PDFIn my previous two posts about the 04-500 and 04-548 X-ray source I showed you all the steps necessary to completely disassemble and reassemble the source and also how to install the new style filaments. This post will explain … Continue reading

Installing new parts in a PHI 04-548 or 04-500 X-ray Source: New Style Filaments

This procedure and video will explain and show the steps required to reassemble the X-ray source that has the new style filaments.

04-548 Filament Installation Video

Refer to this RBD TechSpot blog post for the disassembly procedure and tools required.

04-548 X-ray source reassembly procedure

This procedure assumes that you have disassembled the source completely. If you only needed to replace the filaments, anode or window then you will have only partially disassembled the source and only need to follow the parts of the procedure that apply.

1. Let’s also assume that you have removed the filament feedthrough as shown in the video. Use a new copper gasket and install the flange on the shorter of the two 2.75″ flanges with the couplers facing towards the top of the source. Initially, tighten the bolts finger tight and check the spacing of the couplers with respect to the inner wall of the source tube. If necessary, remove the flange and adjust the height on the coupler mounts (loosen the screw and nut) up or down in order to maximize the spacing between the anode and the couplers as shown in the drawing below. Then install the feedthrough and tighten the bolts. Use anti-seize lubricant on the ends of the bolts if they are dry.

x-ray source tube
Looking inside the X-ray tube

2. Install the football ceramic. If you are installing a new football ceramic (RBD Part Number 602229PR) then you may need to file the edges of the moly blocks that are attached to the ceramic in order for the ceramic to fit inside the tube. It is a snug fit, if necessary use isopropanol as a lubricant.  Line up the 4 holes inside the moly blocks with the holes in the x-ray tube and use the 0-80 screw or tool to insert the football ceramic retainer pins. If necessary, tap the pins gently until they are flush with the tube.

3. Install the moly shield. This is also a snug fit. You will need to work the moly shield back and forth to get it to slide inside the tube. Use isopropanol as a lubricant if needed. Line up the 4 holes in the moly block with the holes in the x-ray tube and using the 0-80 screw or tool, insert the beryllium copper retainer pins into the holes and press them in until they are flush with the outside of the tube. The thread side of the retainer pins face out from the tube.

4. Cut the new filament wires. Lay the new filament next to the old filament on the clean working surface so that you can compare the length of the old filament wire with the new one. You can also remove the ceramic tube (and metal tube) from the old filament and move those over to the new filament, then cut the excess filament wire. Typically, the wires extend about ¼” past the end of the ceramic. It is very important that you cut the wires the same length and same orientation as the old filament. One wire is longer than the other wire and it you cut them incorrectly then the filament will not be able to connect to the coupler and it will unusable. To reiterate, the length of the wires are not the same on both filaments, they are mirrored.

5. Install the filaments. With the ceramics and metal tubes installed on the filament wires, carefully slide the filament wires into the holes in the moly block and guide the filament wires into the couplers as you slide the filament all the way in. The set screws in the couplers should be loose but not all the way out. I have found that a dental tool with a hook on the end is very helpful for positioning the wires into the coupler. RBD Part Number 622275RE

6. Install the filament retainer pins. Once you have the wires guided into the filament couplers, then use the 0-80 screw or tool and install the filament retainer pins.

7. Tighten the filament coupler set screws. Use the needle nose pliers to hold the coupler and then tighten the set screw using the 048-4 Bristol wrench. The set screws need to be very snug, but not too tight. You will feel the wire compress as you tighten the screw. Also note that the wires should stick out about 1/8″ from the back of the couplers and that the couplers should be parallel with the tube body.

8. Install the anode. Clean the anode if needed with a wire brush – note that the coating is only about 10uM thick so you do not want to use very much pressure on the brush. Just finger tight and only a few strokes. You may not be able to clean it completely, but getting most of any back carbon deposit off will increase the x-ray flux and give you a higher count rate. If you are too aggressive then you will take the anode down to the copper and it will need to be replaced. The anodes will naturally wear down to the copper with normal usage. If you need an exchange anode or want to recoat yours, use RBD Part Number 04548ANODWEXRE Slide a new copper gasket over the anode and insert it into the source all the way into the football ceramic. It should extend past the moly block by .010 to .020 inches and there should be a little bit of spring in the anode when it is all the way into the football ceramic. See the video for more details and adjust the anode if necessary before installing the 6 cap head screws. Use anti-size lubricant on the ends of the screws if needed.

9. Install a new window in the end cap. I recommend that you use the old window to practice on until you get the hang of it. Install the window into the end cap with the mesh facing down. Install the C clip to hold the window in place. Use a sharp tipped tweezers. I also use an exacta knife to help guide the clip and hold the window down. This part of the procedure is best performed without previously consuming excessive amounts of caffeine. RBD Part Number 602508PR

10. Install the end cap over the filaments and secure it using the 4 cap head screws.

11. Use a new gasket and install the 2.75″ filament coupler access flange. Once the source is mounted on the chamber, tighten this flange some more (as you will be able to apply more force when it is mounted on the chamber than when the source is on the bench). Also recheck the tightness of the anode screws.

12. Finally, once the system is pumped back down, bake out the system to remove all the water vapor from the x-ray source. Follow the outgas and high voltage conditioning procedures in the 04-548 manual. Contact RBD Instruments if you need more information.

To place an order for replacement parts, please visit our website at www.rbdinstruments.com or by calling us at 541 550-5016