|Normal Incidence Monochromators
for synchrotron beamline applications
McPherson Normal Incidence Monochromators (NIM) have a long history in physics research applications. McPherson patented a mechanical, cam based technique that tilts the grating and compensates for best focus simultaneously. This auto focusing feature sometimes results in normal incidence instruments being called 'McPherson 15-degree' instruments. With the advent of synchrotron storage rings the normal incidence monochromators found ready acceptance. Early implementation included a 2-meter folded or 'straight through' instrument at NIST SURF and a 5-meter focal length instrument at DESY. The included angle of these instruments is not always the 15-degrees popularized with the 1-meter focal length instrument. Angles as small as 1.5-degrees have been used for 6-meter instruments, intermediate focal lengths have used a variety of intermediate, included angles. We continue to manufacture the 1-meter (called McPherson Model 225) focal length instrument with cam corrected auto focusing for general laboratory and occasionally synchrotron uses (PTB / BESSY, UVSOR.) Instruments for synchrotron applications often ship with decoupled focus and grating rotation mechanisms. This allows more articulate computer control of the grating position and enables research with specialty, varied line space gratings.
PDF format sheet with a little history about NIM monochromators available here
McPherson Model 225 1-meter focal length, ultra high vacuum normal incidence monochromator. Versions of this instrument are working at PTB / BESSY and at UVSOR. Built in psuedo- UHV and o-ring sealed versions this is a popular instrument for all manner of laboratory based plasma physics research
4-meter focal length, ultra high vacuum, normal incidence beamline monochromator with vertical deflection (installed at CAMD)