200mm focal length aberration corrected spectrometer

Aberration Corrected Vacuum Monochromator

The Model 234302 is a compact and versatile vacuum ultraviolet monochromator. A selection of aberration-corrected diffraction gratings is available so you can tailor the instrument to your wavelength of interest and application. Connect this instrument directly to your vacuum plasma physics experiment or build an intense UV tunable source. It is available as a scanning monochromator, as a spectrometer, or as a spectrograph with microchannel plate or direct-detection CCD. The Model 234/302 is popular in systems due to its compact design, high throughput and resolution. It is also available with an additional entrance or exit port.

Model 234302 PDF Data Sheet

short GIF clip of an atmospheric plasma jet of Helium gas 20kV 13kHz in air Click on Sample Spectra tab below to see Helium emission spectrum measured with Model 234/302

Specifications & Additional Information:


Optical DesignAberration Corrected Seya-Namioka
Angle of Incidence32 degrees
Focal Length200 mm
Wavelength Rangerefer to grating of interest for range
Wavelength Accuracy+/- 0.10 nm (with 1200 g/mm grating)
Wavelength Reproducibility+/- 0.05 nm (with 1200 g/mm grating)
Grating Size40 x 45 mm (single kinematic grating holder, turret optional)
SlitsContinuously variable micrometer actuated width 0.01 to 3 mm. Settable height.
VacuumHigh vacuum 10E-6 torr standard, UHV optional
Focal Plane25 mm microchannel plate or direct detection CCD

Performance with various diffraction gratings:

Grating Groove Density (g/mm) 2400 1200 600 300
Spectral Resolution (nm,FWHM) 0.05 0.10 0.2 0.4
Dispersion (nm/mm) 2 4 8 16
Wavelength Range up to (nm) 225 550 1100 2200
Holographic Optimization: (nm) 80 140 140 140
140 300

* gratings work best from 2/3 to 3/2 the optimized wavelength

Outline Drawing

McPherson Model 234/302 Aberration Corrected Vacuum Monochromator

Modes of Operation

Model 234302 variants

Some example / test spectra

The deuterium spectrum was collected with the Model 234/302 aberration corrected grating on direct detection CCD. Light source is deuterium lamp with magnesium fluoride window. For the hydrogen, helium and neon the light source is hollow cathode Model 629. The ionized HeNe scan with VUV Silicon diode shows relative response of concave aberration corrected monochromator gratings (2400 g/mm Platinum coated and 1200 g/mm Aluminum Magnesium Fluoride coated)
Call 1-978-256-4512 to discuss your application today.

Select Publications

Abstract: Read at NATURE website A structurally simple dielectric barrier discharge based mercury-free plasma UV-light source has been developed for efficient water disinfection. The source comprises of a dielectric barrier discharge arrangement between two co-axial quartz tubes with an optimized gas gap. The outer electrode is an aluminium baked foil tape arranged in a helical form with optimized pitch, while the inner electrode is a hollow aluminium metallic rod, hermetically sealed. Strong bands peaking at wavelengths 172 nm and 253 nm, along with a weak band peaking at wavelength 265 nm have been simultaneously observed due to plasma radiation from the admixture of xenon and iodine gases. The developed UV source has been used for bacterial deactivation studies using an experimental setup that is an equivalent of the conventional house-hold water purifier system. Deactivation studies for five types of bacteria, i.e., E. coli, Shigella boydii, Vibrio, Coliforms and Fecal coliform have been demonstrated with 4 log reductions in less than ten seconds.
Ram Prakash, Afaque M. Hossain, U. N. Pal, N. Kumar, K. Khairnar & M. Krishna Mohan
Abstract: Application of multilayer technology is extended to high extinction coefficient materials, which is introduced into metal-dielectric filter design. Metal materials often have high extinction coefficients in far ultraviolet (FUV) region, so optical thickness of metal materials should be smaller than that of the dielectric material. A broadband FUV filter of 9-layer non-periodic Al/MgF2 multilayer was successfully designed and fabricated and it shows high reflectance in 140-180 nm, suppressed reflectance in 120-137 nm and 181-220 nm
Xiao-Dong Wang, Bo Chen, Hai-Feng Wang, Fei He, Xin Zheng, Ling-Ping He, Bin Chen, Shi-Jie Liu, Zhong-Xu Cui, Xiao-Hu Yang and Yun-Peng Li
Abstract: The photoinduced room-temperature-stable increase in the refractive index by ~5x10E4 at a wavelength of 1.55um was observed in phosphosilicate fibers without their preliminary loading with molecular hydrogen. It is shown that irradiation of preliminary hydrogen-loaded fibers by an ArF laser at 193 nm enhances the efficiency of refractive-index induction by an order of magnitude. The induced-absorption spectra of preforms with a phosphosilicate glass core and optical fibers fabricated from them are studied in a broad spectral range from 150 to 5000 nm. The intense induced-absorption band (~800 cm-1) at 180 nm is found, which strongly affects the formation of the induced refractive index. The quantum-chemical model of a defect related to this band is proposed.
A.A. Rybaltovsky, V.O. Sokolov, V.G. Plotnichenko, A.V. Lanin, S.L. Semenov, A.N. Gur'yanov, V.F. Khopin, E.M. Dianov
Abstract: The performance of cesium iodide as a reflective photocathode is presented. The absolute quantum efficiency of a 500nm thick film of cesium iodide has been measured in the wavelength range 150nm-200nm. The optical absorbance has been analyzed in the wavelength range 190nm-900nm and the optical and gap energy has been calculated. The dispersion properties were determined from the refractive index using an envelope plot of the transmittance data. The morphological and elemental film composition have been investigated by atomic force microscopy and X-ray photo-electron spectroscopy techniques.
Triloki, R. Rai, Nikita Gupta, Nabeel F.A. Jammal, B.K. Singh
Abstract: We demonstrated efficient generation of ultrafast extreme ultraviolet (XUV) pulses at 89 nm from an intense 267 nm UV femtosecond filamentation in argon gas. The XUV pulse generation efficiency was significantly enhanced through UV filament termination from the argon gas into the background vacuum that prevented backconversion of the generated third-harmonic XUV to the fundamental-wave UV pulses. This was further combined with noncollinear UV filament interaction that produced volume-plasma to pre-extract XUV pulses from the filament core, resulting in further XUV enhancement. The generated 89 nm XUV pulses reached what is so far, to our knowledge, the highest pulse energy of 190 nJ
Wang D, Li W, Ding L, Zeng H
Abstract: A large number of current and future experiments in neutrino and dark matter detection use the scintillation light from noble elements as a mechanism for measuring energy deposition. The scintillation light from these elements is produced in the extreme ultraviolet (EUV) range, from 60 - 200 nm. Currently, the most practical technique for observing light at these wavelengths is to surround the scintillation volume with a thin film of Tetraphenyl Butadiene (TPB) to act as a fluor. The TPB film absorbs EUV photons and reemits visible photons, detectable with a variety of commercial photosensors. Here we present a measurement of the re-emission spectrum of TPB films when illuminated with 128, 160, 175, and 250 nm light. We also measure the fluorescence efficiency as a function of incident wavelength from 120 to 250 nm.
V. M. Gehman, S. R. Seibert, K. Rielage, A. Hime, Y. Sun, D.-M. Mei, J. Maassen, D. Moore
Abstract: We report on the photoemission properties of 300 Å thick transmissive- and 5000 Å thick reflective UV-sensitive CsBr photocathodes. Following post-evaporation heat treatment at 70°C the absolute quantum efficiency is 35% at 150 nm, with a red boundary cut-off at about 195 nm. Extensive aging studies of CsBr and CsI photocathodes, under high photon flux and under ion bombardment in gas avalanche multiplication mode, were carried out for the first time without exposure to air. The results are compared with the previously published data on CsI aging and the methodology of the aging tests is discussed in details.
B. K. Singh, E. Shefer, A. Breskin, R. Chechik and N. Avraham
Abstract: We demonstrate compression of ultrashort light pulses in the ultraviolet (UV) by impulsively excited molecular wave-packets in nitrogen filled in a 25 cm long hollow waveguide of 128 µm diameter. After compression with CaF2 prisms the pulse duration was determined by XFROG to be 23 fs with a time-bandwidth product of 0.50. The advantages of our technique are high efficiency and the possibility to use it also for pulses at wavelength shorter than 200 nm. The experimental observations are explained by a theoretical model.
Noack, F.; Steinkellner, O.; Tzankov, P.; Ritze, H.-H.; Herrmann, J.; Kida, Y.
Abstract: Recent fluorescence studies suggest that ultrashort pulse laser excitation may be highly selective. Selective high-intensity laser excitation holds important consequences for the physics of multiphoton processes. To establish the extent of this selectivity, we performed a detailed comparative study of the vacuum ultraviolet fluorescence resulting from the interaction of N2 and Ar with high-intensity infrared ultrashort laser pulses. Both N2 and Ar reveal two classes of transitions, inner-valence ns←np and Rydberg np←n'l'. From their pressure dependence, we associate each transition with either plasma or direct laser excitation. Furthermore, we qualitatively confirm such associations with the time dependence of the fluorescence signal. Remarkably, only N2 presents evidence of direct laser excitation. This direct excitation produces ionic nitrogen fragments with inner-valence (2s) holes, two unidentified transitions, and one molecular transition, the N+2 :X 2∑+g←C 2∑+u . We discuss these results in the light of a recently proposed model for multiphoton excitation.
Coffee, Ryan N. and Gibson, George N.
Abstract: We develop and implement an experimental strategy for the generation of high-energy high-order harmonics (HHG) in gases for studies of nonlinear processes in the soft x-ray region. We generate high-order harmonics by focusing a high energy Ti:Sapphire laser into a gas cell filled with argon or neon. The energy per pulse is optimized by an automated control of the multiple parameters that influence the generation process. This optimization procedure allows us to obtain energies per pulse and harmonic order as high as 200 nJ in argon and 20 nJ in neon, with good spatial properties, using a loose focusing geometry (f#≈400) and a 20 mm long medium. We also theoretically examine the macroscopic conditions for absorption-limited conversion efficiency and optimization of the HHG pulse energy for high-energy laser systems
Rudawski P, Heyl CM, Brizuela F, Schwenke J, Persson A, Mansten E, Rakowski R, Rading L, Campi F, Kim B, Johnsson P, L'huillier A.
Abstract: The Southwest Research Institute Ultraviolet Reflectance Chamber (SwURC) is a highly capable UV reflectometer chamber and data acquisition system designed to provide bidirectional scattering data of various surfaces and materials. The chamber provides laboratory-based UV reflectance measurements of water frost/ice, lunar soils, simulants, and analogs to support interpretation of UV reflectance data from the Lyman Alpha Mapping Project (LAMP) Lunar Reconnaissance Orbiter (LRO). A deuterium lamp illuminates a monochromator with a nominal wavelength range of 115 nm to 210 nm. The detector scans emission angles -85° to +85°in the principal plane. Liquid nitrogen passed through the sample mount enables constant refrigeration of tray temperatures down to 78 K to form water ice and other volatile samples. The SwURC can be configured to examine a wide range of samples and materials through the use of custom removable sample trays, connectors, and holders. Calibration reference standard measurements reported here include Al/MgF2 coated mirrors for specular reflection and Fluorilon for diffuse reflectances. This calibration work is a precursor to reports of experiments measuring the far-UV reflectance of water frost, lunar simulants, and Apollo soil sample 10084 in support of LRO-LAMP.
Proc. SPIE 8859, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XVIII, 88590R (September 26, 2013); doi:10.1117/12.2024460
Preston L. Karnes ; Kurt D. Retherford ; Gregory S. Winters ; Eric C. Bassett ; Stephen M. Escobedo ; Edward L. Patrick ; Amanda Richter ; Michael W. Davis ; Paul F. Miles ; Joel W. Parker ; G. Randall Gladstone ; Thomas K. Greathouse ; Eric R. Schindhelm ; Lori M. Feaga ; S. Alan Stern
Abstract: We study thorium-doped CaF2 crystals as a possible platform for optical spectroscopy of the 229Th nuclear isomer transition. We anticipate two major sources of background signal that might cover the nuclear spectroscopy signal: VUV-photoluminescence, caused by the probe light, and radioluminescence, caused by the radioactive decay of 229Th and its daughters. We find a rich photoluminescence spectrum at wavelengths above 260 nm, and radioluminescence emission above 220 nm. This is very promising, as fluorescence originating from the isomer transition, predicted at a wavelength shorter than 200 nm, could be filtered spectrally from the crystal luminescence. Furthermore, we investigate the temperature-dependent decay time of the luminescence, as well as thermoluminescence properties. Our findings allow for an immediate optimization of spectroscopy protocols for both the initial search for the nuclear transition using synchrotron radiation, as well as future optical clock operation with narrow-linewidth lasers.
Simon Stellmer, Matthias Schreitl, and Thorsten Schumm
Abstract: Read at NATURE website Novel table-top sources of extreme ultraviolet (XUV) light based on high-harmonic generation (HHG) yield unique insight into the fundamental properties of molecules, nanomaterials, or correlated solids, and enable advanced applications in imaging or metrology. Extending HHG to high repetition rates portends great experimental benefits, yet efficient XUV conversion of correspondingly weak driving pulses is challenging. Here, we demonstrate a highly-efficient source of femtosecond XUV pulses at 50-kHz repetition rate, utilizing the ultraviolet second-harmonic focused tightly into Kr gas. In this cascaded scheme, a photon flux beyond ≈3×1013 s-1 is generated at 22.3 eV, with 5×10-5 conversion efficiency that surpasses similar directly-driven harmonics by two orders-of-magnitude. This enhancement exceeds the predicted dipole wavelength scaling, evidencing improved phase-matching for ultraviolet-driven HHG under tight focusing as corroborated by simulations. Spectral isolation of a single sub-80 meV harmonic renders this bright, 50-kHz XUV source a powerful tool for ultrafast photoemission, nanoscale imaging and other applications.
He Wang, Yiming Xu, Stefan Ulonska, Predrag Ranitovic, Joseph S. Robinson and Robert A. Kaindl
Abstract: Specialized soft x-ray and vacuum ultraviolet ~VUV! diagnostics used to monitor impurity emissions from fusion plasmas are often placed in a very challenging experimental environment. Detectors in these diagnostics must be simple; mechanically robust; immune to electromagnetic interference, energetic particles, and magnetic fields up to several tesla; ultra-high-vacuum compatible; and able to withstand bakeout temperatures up to 300 °C. The design and the photometric calibration of a detector consisting of a P45 phosphor (Y2O2S:Tb), two incoherent fiber-optic bundles coupled with a vacuum feedthrough fiber-optic faceplate, and a photomultiplier tube (PMT) are reported.We have successfully operated the detectors of this type in novel soft x-ray and VUV diagnostics on several fusion plasma facilities. Measurements of the visible photon throughput of the silica/silica incoherent fiber-optic bundle, and the light loss associated with the coupling of the two fibers with the faceplate are presented. In addition, improved absolute measurements of the conversion efficiency of the P45/PMT photodetector based upon the use of a PMT with a bialkali photocathode instead of a multialkali one are presented for the soft x-ray and VUV range of photon wavelengths. The conversion efficiency is defined as the ratio of the photoelectrons ejected from the photocathode of a visible detector, which are excited by the scintillated photons that are emitted from the phosphor in a solid angle of 2p, to the number of soft x-ray photons incident on the phosphor. Sensitive electronic gain measurements of the PMT using the visible scintillated light from the P45 phosphor are compared with the gain measurements supplied by the manufacturer of the PMT, which were performed with a tungsten filament lamp operated at 2856 K.
V.A.Soukhanovskii, S.P.Regan, M.J.May, M.Finkenthal, and H.W. Moos
Abstract: We propose a simple approach to measure the energy of the few-eV isomeric state in 229Th. To this end, 233U nuclei are doped into VUV-transparent crystals, where they undergo α decay into 229Th, and, with a probability of 2%, populate the isomeric state. These 229mTh nuclei may decay into the nuclear ground state under emission of the sought-after VUV γ ray, whose wavelength can be determined with a spectrometer. Based on measurements of the optical transmission of 238U:CaF2 crystals in the VUV range, we expect a signal at least two orders of magnitude larger compared to current schemes using surface implantation of recoil nuclei. The signal background is dominated by Cherenkov radiation induced by β decays of the thorium decay chain. We estimate that, even if the isomer undergoes radiative de-excitation with a probability of only 0.1%, the VUV γ ray can be detected within a reasonable measurement time.
Simon Stellmer, Matthias Schreitl, Georgy A. Kazakov, Johannes H. Sterba, and Thorsten Schumm (see also nuClock.com)

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