VUV Monochromator Research Articles

Cathodoluminescence and Photoluminescence of YPO4:Pr3+, Y2SiO5:Pr3+, YBO3:Pr3+, and YPO4:Bi3+

Herein we describe the synthesis, characterization, and cathodoluminescence of the UV emitting phosphors YPO4:Pr3+, Y2SiO5:Pr3+, YBO3:Pr3+, and YPO4:Bi3+. These photoluminescent UV phosphors exhibited strong luminescence in the UV part of the electromagnetic spectrum when excited by electron bombardment. Spectra have been recorded between 210 and 650 nm at electron beam energies of 5, 10 and 15 keV. The energy efficiencies of YPO4:Pr3+, Y2SiO5:Pr3+, YBO3:Pr3+ and YPO4:Bi3+ in the UV range were 9.2%, 2.7%, 5.1%, and 7.2%, respectively at 15 keV. UV photoluminescence measurements were conducted using 160 nm excitation generated by combining a VUV monochromator with a deuterium lamp.

Optical emission spectroscopy system operating in the vacuum-ultraviolet spectral range λ < 100 nm—a semi-empirical determination of sensitivity

We have determined the wavelength dependent response of an optical emission spectroscopy system operating in the vacuum-ultraviolet region between λ = 30–100 nm, where broad-band light sources with calibrated spectral irradiance are generally unavailable. The system incorporates a constant-deviation VUV monochromator which utilises a single-element concave diffraction grating. An optical surface profiler is used to measure the groove geometry of the diffraction grating to provide detailed information for subsequent 2D numerical modelling of the diffraction efficiencies and the overall wavelength-dependent response curves.

The Distribution of CH3 Over the Film Thickness and Shrinkage of H2 Plasma‐Modified PDMS Films

AbstractThe H2 plasma modification of polydimethylsiloxane (PDMS) films of initial thickness up to 600 nm was studied. The main plasma component modifying the films is the VUV plasma radiation measured by a VUV monochromator. By variation of the plasma processing parameters, such as H2 pressure, RF forward power and treatment time, the optimum parameters are defined for the plasma chemical modification of liquid PDMS films. The thin films were analysed by Infrared Reflection Absorption Spectroscopy. Gradually changes in the vertical films structures is found with a top methyl‐free SiOx layer (≤60 nm), followed by a cross‐linked bulk material with a gradually increasing CH3 concentration over the film depth. Additionally, the PDMS plasma modifications results in films shrinkages as measured by Spectroscopic Ellipsometry (SE). magnified image

Spectroscopic measurements of temperature and plasma impurity concentration during magnetic reconnection at the Swarthmore Spheromak Experiment

Electron temperature measurements during counterhelicity spheromak merging studies at the Swarthmore Spheromak Experiment (SSX) [M. R. Brown, Phys. Plasmas 6, 1717 (1999)] are presented. VUV monochromator measurements of impurity emission lines are compared with model spectra produced by the non-LTE excitation kinematics code PRISMSPECT [J. J. MacFarlane et al., in Proceedings of the Third Conference on Inertial Fusion Science and Applications (2004)] to yield the electron temperature in the plasma with 1 μs time resolution. Average Te is seen to increase from 12 to 19 eV during spheromak merging. Average C III ion temperature, measured with a new ion Doppler spectrometer (IDS) [C. D. Cothran et al., Rev. Sci. Instrum. 77, 063504 (2006)], likewise rises during spheromak merging, peaking at ∼22 eV, but a similar increase in Ti is seen during single spheromak discharges with no merging. The VUV emission line measurements are also used to constrain the concentrations of various impurities in the SSX plasma, which are dominated by carbon, but include some oxygen and nitrogen. A burst of soft x-ray emission is seen during reconnection with a new four-channel detector (SXR). There is evidence for spectral changes in the soft x-ray emission as reconnection progresses, although our single-temperature equilibrium spectral models are not able to provide adequate fits to all the SXR data.

Behavior of CIII to CVI Emissions during the Recombining Phase of LHD Plasmas

Carbon emissions of CIII-CVI during the recombining phase of the Large Helical Device (LHD) plasma are studied to understand their behaviors. To achieve this, four resonance transitions of CIII (977 A: 2 s2 1S-2s2p 1P), CIV (1548 A: 2s 2S-2p 2P), CV (40.27 A: 1s2 1S-1s2p 1P), and CVI (33.73 A: 1s 2S-2p 2P) are observed using absolutely calibrated VUV monochromators and EUV spectrometers. A one-dimensional impurity transport code has been used to calculate spectral emissivity under the consideration of measured ne and Te profiles. The temporal evolution of line emissions has been calculated and compared with the measured data. The comparison shows that the carbon density is 3 % of the electron density. However, a discrepancy between the calculated and measured values has been noticed in CIII and CIV emissions. It has been argued that three-dimensional structures of CIII and CIV emissions are likely to be the reason for this difference, which is based on the presence of relatively high-density and high-temperature plasmas in edge ergodic layer in LHD. It is also found that the CV and CVI emissions during the recombining phase increase with electron density, whereas these are nearly constant during steady state phase. This strongly suggests the disappearance of the edge particle screening effect in the recombining phase.

Tunable light sources based on high harmonics generation for time-resolved VUV spectroscopy

The project of set-up for time resolved femtosecond VUV spectroscopy, which is based on a high harmonic generation source and a VUV monochromator is presented. We discuss the generation conditions of quasi-continuous VUV spectrum via HHG in Ar using the intense chirped IR fundamental pulse and the relatively weak second harmonic of IR fundamental. The desired narrow VUV spectral range is selected by time compensated double monochromator with concave spherical diffraction gratings.

Analytical representation of spot diagrams and its application to the design of monochromators

Abstract A new method has been developed for the design of a highly sophisticated monochromator equipped with a holographic or a ruled grating with variable spacing and curved grooves. The method utilizes analytical expression of the spot diagrams, as well as a merit function which closely represents the rms spread of the spots formed when an infinite number of rays are traced. Unlike other design methods based on the light path function, the present method takes into account all the possible aberrations (up to third order) in spectral images, the ruled area, and the slit height. Also given are design examples of a high-resolution VUV monochromator.

HIGHLY CHARGED ION N6+ COLLISIONS WITH ATOM He INTO EXCITED STATES

The excitation processes in collisions between N6+ and He have been investigated by using the ECR ion source and the LHT-30 VUV Monochromator. The emission spectra shows that there are three channels of excitation in the N6+ and He collision system: (1) Single-electron capture into excited states. (2) Double-electron capture into excited states. (3) Direct excitation of indicident ions.

The design and construction of a VUV Ar-arc source and a VUV monochromator

The design and construction of a VUV source and a VUV monochromator is reported. The reliability of the VUV source suggests that it can be used as a VUV high radiance transfer secondary standard. A VUV window is used to isolate the high pressure argon-arc source from the VUV monochromator. The spectrum is therefore limited by the transmission cut-off of the window. Alternatively, a differential pump could be used to extend the wavelength range to the extreme UV and eliminate the uncertainties associated with the aging effects of the VUV window. The apparatus is to be used to measure the VUV spectra of certain glass samples.

Integrated accelerator—monochromator apparatus for time-resolved vacuum-ultraviolet spectroscopy

A custom-built computer controlled VUV monochromator and scanning mirror assembly were integrated with a 32-kV accelerator and target chamber for measurements of radiative lifetimes of VUV transitions with the beam-gas method. The monochromator has been calibrated and used to measure wavelengths and instrumental linewidths of the Ly-α and Ly-β lines of atomic hydrogen and of a number of mercury lines in preparation for a systematic program of lifetime measurements in the vacuum ultraviolet.

Sensitivity Calibration of a VUV System by Branching Line Pairs of Highly Ionized Atoms

Eight vacuum ultraviolet branching line pairs from C IV, O V, O VI, O VIII and Fe XXI are selected to perform in situ relative sensitivity calibration of a VUV monochromator installed on the JIPP T-IIU tokamak. Details of the behavior of these line pairs in a tokamak plasma are described and discussed. Relative sensitivity calibration in the wavelength region from 75 Å through 1230 Å is conducted by measuring the intensity ratios of these line pairs and by arranging them by the simple proportional allotment method.

Synchrotron radiation apparatus for supersonic jet experiments

In this article, we report the layout of our VUV beamline including a VUV monochromator and a molecular-beam photoionization apparatus. This experimental system has recently been completed at a UVSOR Facility of this Institute for studying van der Waals complexes produced by supersonic expansion. Several experimental results are also presented to show the characteristics of the apparatus.

Stigmatic monochromators for synchrotron sources

In this paper I describe new stigmatic VUV and XUV monochromators specially designed to match the “etendue” of Super ACO. Fixed horizontal and vertical diffracted beam divergences, as well as uniform sample illumination are allowed; moreover, particular gratings delivering diffraction limited monochromatic convergent beams also allow image evaluation of optical instruments.

Energy Level Determination Using Two-Photon (Vacuum Ultraviolet and Visible) Resonance Spectroscopy*

With the use of a Nd:YAG laser and a dye laser, energy levels in argon and krypton have been measured. This technique can examine energy levels in the range of 11.9 eV to 16.4 eV, with the accuracy rivaling methods that employ very long VUV monochromators. The amount of photoionization has been calculated and agrees well with the experiment.

Dedicated undulator monochromators

In this paper we describe new types of VUV monochromators using only spherical or plane type V holographic gratings. New design rules using physical optics associated with the phase balancing method are suggested to achieve diffraction limited performances.

Measurement of absorption line intensities with VUV monochromators

Problems involved with the use of VUV scanning monochromators in the measurement of absorption line intensities are discussed. Instrument modifications enabling the accurate determination of equivalent widths at maximum wavelength resolution are described.

VUV and soft X-ray monochromators for use with synchrotron radiation

The development of VUV and soft X-ray monochromators from the very first design us generation installed at dedicated storage rings is reviewed. Several instruments in operation at synchrotron radiation laboratories are discussed, together with the performance achieved. Most of the progress concerning monochromators is based on the rapid improvement in mirror and grating technology. The close connections between monochromator, beam-line optics and light source for the photon flux and spot size at the sample are emphasized.

Focusing cam design for normal incidence VUV monochromators

The design of a focusing cam suitable for use in McPherson-type normal incidence VUV scanning monochromators is described. An approximate analytic procedure is given which enables the rapid calculation of cam shape to a sufficient accuracy to maintain an accurate focus over the operational wavelength range of such monochromators.

On-blaze scanning monochromator for the vacuum ultraviolet

The Rowland circle mounting for scanning VUV monochromators with concave blazed diffraction gratings can be adapted so that the operation is always on-blaze; that is, the monochromator always operates at maximum efficiency. In principle, this adaptation works at any angle of incidence, but in practice only grazing incidence monochromators are practical. The scanning range of such a monochromator is less than for a conventional monochromator but can be extended by storing gratings with different groove densities on a carousel and rotating them into position as necessary.

Measurement of transmission of VUV monochromators and electron spectrometers using photoemission spectroscopy

In many applications of photoemission spectroscopy it is necessary to know the relative photoelectron yield from a sample as a function of energy. Two aspects of this measurement are specific to synchrotron radiation sources. We first present a method of extracting the monochromatic contribution from an absorption measurement which includes harmonics of the primary frequency aas well as scattered light. In addition, this measurement is a useful way to characterize VUV monochromators. Secondly, we present an analysis of the transmission of electron spectrometers when viewing a source of the dimensions of a synchrotron radiation source. This is midway between the well-characterized cases of flooded sources (such as an X-ray source) and point sources (such as an electron gun).