The collimators before and after the sample are made of non-magnetic materials to be compatible with polarized beam operation. With all blades in the collimators, they have a calculated acceptance of 5', 10' and 20' FWHM, respectively. Larger angular acceptances can be obtained by (CAREFULLY!) removing blades (from the 20' collimator only!) as necessary. The Monochromator-to-Sample collimator is 22" long, and the Sample-to-Analyzer collimator is 11". Taking into account the width of the blades, the calculated collimations are:
Number of Cd Blades M-S Collimator S-A Collimator All slots occupied 20' 20' Every other blade 41' 42' Every third blade 62' 64' Every fourth Blade 83' 87'
There is also a radial S-A collimator which is used in conjunction with the horizontally focusing analyzer.
The blades for these collimators were constructed from brass shim stock, with a few mils of Cd electroplated onto the surface, and then cut and finished to size. They are delicate, as well as difficult and expensive to replace. PLEASE use them ONLY in the collimators. Blades not in immediate use should be stored in the cabinet (not left on the spectrometer where they can be damaged).
The blades slide easily in the collimators. If they do not slide easily, STOP and find out why---there must be something wrong. DON'T force the blades.
Three, 3" long detector collimators are available.
20' FWHM (Do NOT remove these blades!)
40' FWHM collimator with fixed blades
20' collimator with adjustable blades.
This collimator is usually set for 80' or 120' collimator; there is no reason to put all the blades in anymore, as fixed 20' and 40' collimators are now available.
These collimators fit in the holder, and there are two bolts to hold them in place. These bolts should be hand-tightened only; the only exception is in polarized beam mode, where the collimator needs to be securely held to prevent it from moving into the magnet of the analyzer.
There are also three different detector shields available. A rigid poly+Cd block that fits tightly over the collimator, a separate Cd "hat" that is easy to use, and a smaller rigid poly+Cd aperture that is typically used for the horizontal focusing analyzer.
Source to Monochromator: 165"
Monochromator to Sample: 60"
Sample to Analyzer: 33"
Analyzer to Detector: 8"
Last modified 25-August-2003 by website owner: NCNR (attn: Jeff Lynn)