One meter focal length McPherson 15° autofocusing spectrometer

McPherson 15° Vacuum Ultraviolet Monochromator

The Model 225 one-meter normal incidence (NIM) vacuum ultraviolet monochromator is sometimes referred to as the “McPherson 15°.” The tight angle between entrance and exit slits results in an optical design with reasonable imaging and low polarization. Its unique wavelength drive translates the grating during rotation to maintain best focus at wavelength. This is an ideal high-resolution instrument for use with microchannel plate intensifiers or CCD detectors. It is a very clean design; the wavelength drive is outside the stainless steel vacuum vessel. We deliver it with single gratings, or double- or triple-grating turrets. It can be mounted horizontally or on its side, to save space.
The Model 225 is a high-vacuum instrument (10E-6 torr) and ultra-high vacuum (10E-10 torr) versions are available. We also make it with two, three and even 6-meter focal lengths that achieve resolving power 78,000 at 46.4nm.

Model 225 PDF Data Sheet

Specifications & Additional Information:


Optical DesignNormal Incidence, McPherson-15°
Angle of Incidence7.5 degrees
Focal LengthOne meter
f/no.10.4 horizontal
Wavelength Rangerefer to grating of interest for range
Wavelength Accuracyr+/-0.10 nm (with 1200 g/mm grating)
Wavelength Reproducibility+/- 0.005 nm (with 1200 g/mm grating)
Grating Size56 x 96 mm (single kinematic grating holder, two- and three-grating turret optional)
SlitsContinuously variable micrometer actuated width 0.01 to 2 mm. Settable height.
VacuumHigh vacuum 10E-6 torr standard, UHV optional
Focal Plane40 mm max. Multiply dispersion of the selected grating by width of your CCD or MCP to determine simultaneous range

Performance with various diffraction gratings:

Grating Groove Density (g/mm) 3600 2400 1200 600 300
Spectral Resolution (nm,FWHM) 0.005 0.008 0.015 0.03 0.06
Dispersion (nm/mm) 0.28 0.42 0.83 1.66 3.33
Wavelength Range up to (nm) 100 150 300 600 1200
Holographic or Blaze Optimization: (nm) Holo 80 45** 90 Holo
80 150 700
120 200
150 300

* gratings work best from 2/3 to 3/2 the optimized wavelength, ** reduced 30 x 50 mm ruled area

Outline Drawing

McPherson Model 234/302 Aberration Corrected Vacuum Monochromator

Modes of Operation

Ultra High Vacuum 1m Model 225
Ultra-High-Vacuum 1m Model 225
Ultra High Vacuum three meter focal length Model 225
Ultra-High-Vacuum three meter focal length Model 225
225 with Plus-One entrance port and Conflat seals
225 with Plus-One entrance port and Conflat seals

Select Publications

Abstract: The electron storage ring BESSY is a primary radiometric standard of spectral irradiance, which has been used for the calibration of deuterium lamps as radiometric transfer standards of spectral radiance in the wavelength range 115-350 nm. The radiometer used for these measurements is described in detail. For λ > 165 nm the uncertainty of the spectral radiance of the calibrated lamps is if > 3%.
Tegeler, Erich
Nuclear Instruments and Methods in Physics Research Section A, Volume 282, Issue 2-3, p. 706-713.
Abstract: The population dynamics of molecular hydrogen in its electronic ground state is of particular interest for the understanding negative ion production. The favored process is dissociative attachment of low energy electrons to highly excited electronic ground state molecules. We report on in-situ measurements of the population of these states in a pulsed hydrogen plasma using LIF in the VUV. The measurements are taken after the fast interruption of the discharge current. In the current range investigated the population of the vibrational states is highly suprathermal, and the theoretically predicted plateu in the distribution is clearly observed.
Thomas Mosbach and H. F. Dobele
Institut fur Laser und Plasmaphysik, Universitat GH-Essen, D-45117 Essen
Abstract: Spectroscopic instrumentation is one of the keys to the exploration of high-temperature plasmas. The electron beam ion trap EBIT can serve as a tool for precise studies of highly charged ions in the laboratory and can help in setting spectroscopic standards for plasma studies. Recent efforts have focused on investigating the EUV, vacuum ultraviolet VUV , and UV regimes. We present here the implementation of a 1 m normal incidence spectrometer for use on the Lawrence Livermore National Laboratory high-energy EBIT Super-EBIT for spectral analysis of line emission of highly charged ions. Using two different gratings, our study encompasses a wide range of wavelengths spanning the VUV through the visible. Examples of measurements of optical spectra from krypton and argon are given.
S. B. Utter, P. Beiersdorfer, J. R. Crespo Lapez-Urrutia and E. Traebert
Review of scientific instruments 1999, vol. 70 (2), no1, pp. 288-291
Abstract: The observation of photon-cascade emission (PCE) in Pr3+ activated SrAl12O19 under vacuum ultraviolet excitation (VUV) is reported and discussed. In this host lattice, the lowest-energy component of the Pr3+ 4f5d excited configuration is located above the 1S0 state. The excitation of the Pr3+ 4f5d state by VUV photons results in radiative emission originating from the 1S0 level state. The subsequent radiative emission from the 1P0 state confirms the photon-cascade emission of Pr3+ activated SrAl12O19. To the best of our knowledge this is the first observation of PCE in an oxide matrix.
A. M. Srivastava and W. W. Beersb
Journal of Luminescence Volume 71, Issue 4, May 1997, Pages 285-290
Abstract: Front-illuminated PtSi-n-Si Schottky barrier photodiodes have been developed for the ultraviolet and vacuum ultraviolet spectral range. Their spectral responsivity was determined in the 120-500 nm spectral range by use of a cryogenic electrical substitution radiometer operated with spectrally dispersed synchrotron radiation. For wavelengths below 250 nm, the spectral responsivity is about 0.03 A/W, comparable to that of GaAsP Schottky photodiodes. Unlike the GaAsP diodes, the new PtSi-n-Si diodes have a spatially uniform response which is virtually stable after prolonged exposure to short wavelength radiation. Even after a radiant exposure of 150 mJ cm-2 at wavelength 120 nm, the relative reduction in spectral responsivity remains below 0.2%. Due to these features, this type of photodiode is a promising candidate for use as secondary detector standard in the ultraviolet and vacuum ultraviolet spectral ranges.
K. Solt, H. Melchior and U. Kroth, P. Kuschnerus, V. Persch, H. Rabus, M. Richter, and G. Ulm
Applied physics letters 1996, vol. 69, no24, pp. 3662-3664
Abstract: We have recently reported that bound electron-hole pairs (Mott-Wannier excitons) are the dominant source of photoelectron emission from specially prepared [as-polished C(111)-(1×1):H] negative-electron-affinity diamond surfaces for near-band-gap excitation up to 0.5 eV above threshold [C. Bandis and B. B. Pate, Phys. Rev. Lett. 74, 777 (1995)]. It was found that photoexcited excitons transport to the surface, break up, and emit their electron. In this paper, we extend the study of exciton-derived emission to include partial yield (constant final-state) analysis as well as angular distribution measurements of the photoelectric emission. In addition, we find that exciton-derived emission does not always dominate. Photoelectric emission properties of the in situ ‘‘rehydrogenated’’ (111)-(1×1):H diamond surface are characteristically different than emission observed from the as-polished (111)-(1×1):H surface. The rehydrogenated surface has additional downward band bending as compared to the as-polished surface. In confirmation of the assignment of photoelectric yield to exciton breakup emission, we find a significant enhancement of the total electron yield when the downward band bending of the hydrogenated surface is increased. The functional form of the observed total electron yield demonstrates that, in contrast to the as-polished surface, conduction-band electrons are a significant component of the observed photoelectric yield from the in situ hydrogenated (111)-(1×1):H surface. Furthermore, electron emission characteristics of the rehydrogenated surface confirms our assignment of a Fan phonon-cascade mechanism for thermalization of excitons.
C. Bandis and B. B. Pate
Surface science 1996, vol. 350, no1-3, pp. 315-321
Abstract: A 1-m normal incidence spectrometer has been modified for use as a diagnostic of ion diode plasmas. To improve instrumental sensitivity, an elliptical mirror images an anode surface plasma onto the entrance slit of an f/10 normal incidence spectrometer. The detector is a time-resolving copper iodide coated microchannel plate stripline framing camera with 60-µm resolution, limiting instrumental resolution to 0.1nm with a 600 l/mm grating in first order. Reflectivity of optics and photoelectron efficiency limit the spectral range from 400 to 2000 Ã…. With a 600- l/mm grating the detector spans a 600-Ã… range. Applications of the instrument may include ion source divergence measurements from Doppler broadening, electric field measurements from Stark splittings or shifts, electron temperature from mean ionization state, and magnetic field measurements on high-power Z pinches from Zeeman splitting.
T. Nash, D. Noack, and A. B. Filuk
Review of Scientific Instruments; Journal Volume: 64:9, Pages: 2493-2495
Abstract: Special electronic scanning circuits have been built to increase the resolution time of an intensified photodiode array assembly used for detecting EUV emission. The system can operate at 1-MHz sampling rate to provide data readout on two parallel output lines. The scanning time of a 1000-element array can be reduced to 500 µs. The system is programmable and can function sequentially at three different frequencies within a single scan. The device is CAMAC compatible and operated remotely by computer. It has been used to record spatial as well as temporal development of EUV radiation from the TEXTOR tokamak plasma.
H. H. Mai, J. M. Larsen, K. Dimoff and J. Castracane
Review of Scientific Instruments, Volume 57, Issue 5, May 1986, pp.866-873
Abstract: A space-resolved vacuum ultraviolet (VUV) spectroscopy using a 3 m normal incidence spectrometer has been developed to measure the impurity profile in the edge ergodic layer composed of stochastic magnetic field by which the edge plasma in the large helical device (LHD) is uniquely characterized. It vertically measures the spatial profile of VUV lines emitted from impurities in the wavelength range of 300–3200 Å. The wavelength interval, Δλ, which can be measured in a single discharge, is about 37 Å. A spectral resolution of 0.153 Å, which results from an entrance slit width of the spectrometer of 20 μm, is adopted. The vertical observation range, ΔZ, can be switched by taking a convex mirror in and out, which enables both the edge profile measurement focused on the ergodic layer and the full profile measurement covering an entire vertical size of the LHD plasma, e.g., 165 ≤ ΔZ ≤ 200 mm and 1000 ≤ ΔZ ≤ 1250 mm for the Rax 3.6 m configuration, respectively, which shows a slight wavelength dependence. Precise calibrations on the line dispersion, spectral resolution, vertical range of the observable region, and the spatial resolution have been performed with a unique method. As a preliminary result, the ion temperature profile is obtained for CIV at 1548.20 Å in the second order (denoted as 1548.20 × 2 Å) in high-density helium discharges in addition to the emission profile with a time resolution of 100 ms in a multitrack CCD operation mode. The poloidal flow in the ergodic layer based on the Doppler-shift measurement of CIV at 1548.20 × 2 Å is also observed in high-density hydrogen discharges.
Tetsutarou Oishi, Shigeru Morita, Chunfeng Dong, Erhui Wang, Xianli Huang, Motoshi Goto, and LHD Experiment Group
APPLIED OPTICS / Vol. 53, No. 29 / 10 October 2014
Abstract: A 4 m normal incidence monochromator for use at the Tantalus storage ring is described. A general description of the instrument is given, together with a brief discussion of the optics required to match the angular acceptance of the monochromator to the angular spread of the source. With a 3600 lines mm−1 grating the estimated flux at the blaze wavelength of 304 Å with a bandwidth of 0.01 eV and 100 mA of circulating current, is 6 × 109 photons s−1.
Nuclear Instruments and Methods, Volume 172, Issues 1–2, 15 May 1980, Pages 181–183
Abstract: In the present contribution the two normal-incidence monochromator beam lines of the Physikalisch-Technische Bundesanstalt (PTB) for the calibration of radiation sources and detectors and the characterisation of optical components are briefly described. After shut down of BESSY I these bending magnet beam lines have been transferred to the radiometry laboratory of PTB at BESSY II. Emphasis is laid on the technical aspects linked with the change from BESSY I to BESSY II such as, e.g., the out-of-plane acceptance of the synchrotron radiation to reduce the heat load on the normal-incidence optics caused by the higher characteristic energy of BESSY II bending magnet radiation compared to BESSY I.
M Richter, , J Hollandt, U Kroth, W Paustian, H Rabus, R Thornagel, G Ulm
Abstract: The study of tokamak plasma light emissions in the vacuum ultraviolet (VUV) region is an important subject since many impurity spectral emissions are present in this region. These spectral emissions can be used to determine the plasma ion temperature and density from different species and spatial positions inside plasma according to their temperatures. We have analyzed VUV spectra from 500 Å to 3200 Å wavelength in the TCABR tokamak plasma including higher diffraction order emissions. There have been identified 37 first diffraction order emissions, resulting in 28 second diffraction order, 24 third diffraction order, and 7 fourth diffraction order lines. The emissions are from impurity species such as OII, OIII, OIV, OV, OVI, OVII, CII, CIII, CIV, NIII, NIV, and NV. All the spectra beyond 1900 Å are from higher diffraction order emissions, and possess much better spectral resolution. Each strong and isolated spectral line, as well as its higher diffraction order emissions suitable for plasma diagnostic is identified and discussed. Finally, an example of ion temperature determination using different diffraction order is presented
M.Machida; A.M.Daltrini; J.H.F.Severo; I.C.Nascimento; E.K.Sanada; J.I.Elizondo; Y.K.Kuznetsov
Abstract: Vacuum ultraviolet region, 50nm to 320nm, of tokamak plasma light emission from NOVA-UNICAMP and TCABR has been analyzed using one-meter focal length VUV spectrometer and open MCP/CCD detector. About 86 spectral emissions are detected, where 35 lines are from first diffraction order and others are from second, third and fourth diffraction order. The first order spectral lines are mainly emitted below 150 nm, and the region from 100 nm to 320 nm is useful to observe higher diffraction order lines. Impurity species such as OII, OIII, OIV, OV, OVII, CII, CIII, CIV, are very common lines also present in the larger tokamak plasma. The use of higher diffraction order emissions and the control of pixel distribution over Gaussian profile show to be very important in order to obtain correct ion temperature, due to the narrow Doppler broadening in the VUV region and large instrumental broadening. We conclude that the effect of Gaussian width difference is caused by the wavelength interval covered by each pixel on the Gaussian fit
Abstract: Spectral emissions in the vacuum ultraviolet region from 50 nm to 320 nm have been measured on TCABR tokamak using an one meter VUV spectrometer and a MCP coupled to a CCD detector. Among the 98 emissions classified, 37 are from first order diffraction, 29 are from second order, 24 are from third order, 7 from fourth order, and one from fifth order diffraction. Main impurity lines are OII to OVII, CII to CIV, NIII to NV, FVII, besides working gas plasma hydrogen Lyman lines
M. Machida, A. M. Daltrini, J. H. F. Severo, I. C. Nascimento, E. K. Sanada, J. I. Elizondo, Y. K. Kuznetsov, R. M. O. Galvão
Abstract: A grazing-incidence flat-field extreme ultraviolet (EUV) spectrometer has been newly developed in HL-2A tokamak. Typical spectral lines are observed from intrinsic impurities of carbon, oxygen, iron, and extrinsic impurity of helium in the wavelength range of 20 Å-500 Å. Bremsstrahlung continuum is measured at different electron densities of HL-2A discharges to calibrate absolute sensitivity of the EUV spectrometer system and to measure effective ionic charge, Z(eff). The sensitivity of a vacuum ultraviolet (VUV) spectrometer system is also absolutely calibrated in overlapped wavelength range of 300 Å-500 Å by comparing the intensity between VUV and EUV line emissions
Zhou H1, Cui Z, Morita S, Fu B, Goto M, Sun P, Dong C, Gao Y, Xu Y, Lu P, Yang Q, Duan X
Abstract: This paper investigates in detail the vacuum UV photoabsorption spectrum of trans-1,2-C2H2Cl2 in the 5–20 eV range using synchrotron radiation. Quantum chemical calculations are applied to the electronic transitions. Particular attention has been paid to the 2au(π)→2bg(π*) transition included in the broad band observed at 6.30 eV. The Rydberg 2au(π)→R3s transition is presumably observed at 6.27 eV. Below 6.0 eV the structure(s) are assigned to π→σ* transition(s). The abundantly structured spectrum observed between 7.0 eV and 12.0 eV has been analyzed in terms of vibronic transitions to ns- (=0.844) and nd/4f- (=0.03/0.011) Rydberg states, converging to the 2au−1 ionization continuum, to two series of np- (= 0.66 and 0.40) states converging to the 5ag−1 continuum, to ns- (=0.983) and nd- (= –0.06) states converging to the 4bu−1 continuum and to two np-type (= 0.51 and 0.26) series converging to the 1bg−1 continuum. These data are complemented by an analysis of the vibrational structure of the individual Rydberg states. Comparisons with previously reported values are provided. Several other spectral features Table S2 (see Supplementary Material) in the 12–20 eV range are tentatively assigned to transitions to Rydberg states converging to higher ionic excited states of trans-1,2-C2H2Cl2. Assignments of the vibrational structure of some of these transitions are also proposed.
R.Locht D.Dehareng B.Leyh

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