Normal Incidence Monochromators
for synchrotron beamline applications
  • 5 to 40-eV
  • 1, 2, 3, 4, 5 and 6.6-meter focal length
  • Index between 3 or 4 gratings under vacuum
  • Internal or heat sink grating cooling
  • UHV construction for 10^-10 torr operation
  • Bakeable to 150-degrees C
3-meter NIM as built for CAMD Louisiana

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

Normal Incidence Monochromator Specifications, with 1200-g/mm grating for more popular focal lengths
Focal Length1-m2-m3-m5-m
Resolution, FWHM0.015-nm0.007-nm0.005-nm0.003-nm
Dispersion0.83-nm/mm0.42-nm/mm0.28-nm/mm0.17-nm/mm


Recent installations of McPherson normal incidence monochromators include ALS, CAMD, NSLS (beamline page), SRC, SSRL (beamline page), Photon Factory (beamline page) and UVSOR.

Current McPherson ultra high vacuum (UHV) instruments are baked and RGA tested prior to shipment. Unique proven McPherson designs separate support members for chambers and precision grating mechanism. This for reduced sensitivity to vibration and thermal environmental factors. Scan grating angle by computer control and use rotary or laser tilt encoders for absolute feedback. Index gratings under vacuum, manually or by motor control. We have a variety of beam line instruments and accessories available.




the 'McPherson 15-degree 1-meter focal length, ultra high vacuum normal incidence monochromator

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 normal incidence beamline monochromator with vertical deflection

4-meter focal length, ultra high vacuum, normal incidence beamline monochromator with vertical deflection (installed at CAMD)

Sales@McPhersonInc.com, Telephone (978)256-4512, Fax (978) 250-8625
McPherson, Inc. - 7A Stuart Road, Chelmsford, MA 01824 USA