This Kratos monochromator adjustment procedure is used on the Kratos Axis, 165, Ultra and Nova monochromators.<\/p>\n
Steps involved in optimizing the performance of the Al Monochromatic x-ray source:<\/p>\n
First, load a sample bar containing a grid alongside a clean Ag foil sample at the same height.<\/p>\n
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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.<\/li>\n
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.<\/li>\n
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.<\/li>\n
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.<\/li>\n
The micrometer on top of the mechanism (marked \u201cDo not adjust\u201d in the image) changes the distance between the crystal and the sample. (After initial factory set up \u2026i.e. for normal maintenance procedures\u2026anode changes etc… this will not need re-tuning).<\/li>\n
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.<\/li>\n
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.<\/li>\n<\/ol>\n
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.<\/p>\n
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 \u201cmaximum\u201d count rate.<\/p>\n
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 \u201chybrid\u201d mode. (Starting with the 110um aperture is sometimes difficult due to the lower counting rates).<\/p>\n
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.<\/p>\n
![\"monochromator-micrometers\"](\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2015\/09\/monochromator-micrometers.jpg?ssl=1\")