摘要:

The superioretenduavailable from a Fabry–Perot spectrometer is also accessible when used in reflective mode in producing a narrow bandwidth rejection, or ‘‘notch,’’ filter. We consider the instrumental defects and the practical effects involved in realizing a useful device. A simple figure of merit is obtained which allows the Fabry–Perot characteristics to be specified according to the desired performance of the rejection filter. A comparison is made between calculations and a prototype Fabry–Perot notch filter.

ISSN:0034-6748    

DOI:10.1063/1.1143467

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A diagnostic has been designed to study edge plasma velocities in (JET) with good space and time resolution. To eliminate ambiguities in the measurement arising from atomic physics effects opposing views are provided. Each viewing direction incorporates ten fibers imaged on the path of a neutral heating beam with a channel spacing of 1.5 cm. The chord views are imaged onto a spectrometer with 20 individual entrance slits arranged in a rectangular array. The dispersed spectra from adjacent slits form linear images 25 mm long that are recorded using four fast optical multichannel analyzers. To prevent crosstalk of signals from adjacent slits the instrument incorporates a low dispersion spectrometer to limit the bandpass of the system. The principal advantage of this design is the ability to match thefnumber of the fiber optic arrays. This results from the rectangular arrangement of the slits which allows for a 4× magnification of the fiber images without requiring an exceptionally long (70 mm) entrance slit. This matching optimises the light collection efficiency of the complete diagnostic which ultimately sets the shortest time resolution. The minimum readout time for all 20 channels is 0.5 ms, although longer integration times are generally needed in JET.

ISSN:0034-6748    

DOI:10.1063/1.1143468

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A multichannel spectrometer with high spectral resolution (0.01 nm) and high temporal resolution (0.5 ms) has been configured to collect data simultaneously from eight viewchords spanning the divertor region of DIII‐D. Fiber optically coupled to a wide‐field lens with a vertical view of the vessel floor, the instrument will be capable of differentiating the behavior of impurity line emission at the inner and outer divertor strike points, on and off the Advanced Divertor Program ring, on the face of the Divertor Material Exposure System probe, and in the region of the lower centerpost. Used with a coarse grating (300 grooves/mm), spectral coverage of each spatial channel is 15 nm with 0.3 nm resolution; used in high order with a 1200 groove/mm grating, the instrument is capable of resolving Doppler profiles. Spatial variation of gas recycling and impurity influx will be studied for both single‐ and double‐null divertor configurations in low and high density operating regimes.

ISSN:0034-6748    

DOI:10.1063/1.1143469

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Recent studies have shown that fairly weak dilution of the D‐T fuel mixture by the thermal alpha particle population may quench ignition in ITER. The alpha particle exhaust issue is not well understood experimentally, especially in H mode. On DIII‐D, a large set of diagnostics for studying alpha particle thermalization and exhaust are being developed. Helium density profiles in the core plasma are inferred from data obtained by the existing DIII‐D charge‐exchange recombination spectroscopy system which has 32 chords that span the plasma cross section and has been absolutely calibrated so that absolute emission intensities can be inferred from the measured data. Relative chord‐to‐chord intensity calibrations have been made by injecting neutral beams into neutral gas with no magnetic fields. A multifiber system viewing the divertor floor has been absolutely calibrated to measure the hydrogen and helium recycling profile across the divertor floor. Other diagnostics in development include a Penning discharge gauge to measure helium partial pressure under the divertor baffle in DIII‐D. Preliminary measurements from these diagnostics will be presented. This work supported by U.S. Department of Energy (DOE) Contract DE‐AC03‐89ER51114 and by appointment to the DOE Fusion Energy Postdoctoral Research Program administered by Oak Ridge Associated Universities.

ISSN:0034-6748    

DOI:10.1063/1.1143470

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A narrow‐bandpass (∼7 A˚) and high‐throughput (f/5.5) extreme ultraviolet (XUV) camera using layered synthetic microstructure (LSM) coated optics has been built and tested at the Johns Hopkins University laboratory in order to image tokamak plasma emission between 100 and 200 A˚. The LSM camera was tested with a Penning ionization discharge emission source. The test measures the spectral bandpass, the spatial resolution, and the relative photosensitivities. The XUV camera will be used to measure the O vi150 A˚ line brightness on the Phaedrus‐T tokamak with a tangential view to investigate the impurity transport.

ISSN:0034-6748    

DOI:10.1063/1.1143471

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The layered synthetic microstructure (LSM) technology has made two‐dimensional soft x‐ray imaging of a tokamak plasma in a single impurity spectral line emission feasible. The curved LSM is used both as an optical filter, with a bandpass in the range of interest on the order of 1.5 A˚, and as a focusing optic. A detailed design of a narrow bandpass curved LSM‐based pinhole camera, which will image the the region from the scrape‐off layer 26 cm into the plasma in the DIII‐D tokamak plasma in C viLyman &agr; emission at 34 A˚, will be presented.

ISSN:0034-6748    

DOI:10.1063/1.1143472

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Molybdenum, from the vessel wall armor tiles and divertor plates, is expected to be the dominant high‐Zimpurity in the Alcator C‐MOD tokamak plasma. To monitor the molybdenum emission in the extreme ultraviolet (XUV), a monochromator utilizing multilayer mirrors (MLMs) as dispersive elements will be installed on the C‐MOD tokamak with a 10° above the mid‐plane view across the plasma’s center. Much of the strong Mo emission under the C‐MOD experimental conditions will be emitted between 30–50 A˚ and 65–90 A˚ byM‐shell ions (n=3–3 andn=3–4 transitions), at 116 A˚ from MoXXXI and at 127 A˚ from MoXXXII. The monochromator will have three MLMs and either three‐channel electron multipliers or three XUV silicon photodiodes mounted on a single &thgr;‐2&thgr; goniometer. Each MLM and detector unit will simultaneously monitor a separate molybdenum emission range with a 1–10‐ms temporal resolution. The resolution of the MLMs range from 1 to 5 A˚ depending on the wavelength, and each MLM will be optimized for one of the above spectral regions. This low‐resolution monitoring of many charge states will enable radiative power loss estimates and can be used in impurity transport analysis. The design of the monochromator and the expected Mo emission will be presented and discussed.

ISSN:0034-6748    

DOI:10.1063/1.1143473

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A spectroscopic diagnostic for measurement of slowing‐down alpha particles is under development and will be implemented for D–T operation of the Tokamak Fusion Test Reactor. The visible 468.6 nm He+line (n=3–4) is excited by charge exchange recombination of alphas with a heating neutral beam (55 keV/amu), and the distortion of the line profile caused by alphas with energies up to 0.5–1.0 MeV is observed. Expected intensities are 0.1%–10% of the bremsstrahlung background for D–T discharges withQ=0.2–1.0. Because the signal is small, a high‐throughput optical system is needed to achieve the desired signal‐to‐noise ratio of 10–100. Vertical and horizontal arrays of sightlines with five spatial channels will be used. Initially, two spatial channels will be coupled via fiber optics to anf/3.8 spectrometer equipped with a low‐noise charge coupled device detector, with expansion to 5–10 spatial channels planned for D–T operation.

ISSN:0034-6748    

DOI:10.1063/1.1143474

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

An optical spectroscopy diagnostic has been designed to observe emissions from the nonthermal alpha particle population that will be generated during the D–T operation phase on TFTR. The system will observe spectral line emission near 469 nm from the slowing‐down alpha population interacting with the heating neutral beams through charge exchange. The required spectrometer throughput and resolution are obtained by modification of a simple commercial spectrometer system, while a series of measurements indicate that a cooled CCD array is usable as a high‐efficiency detector with photon‐noise‐limited accuracy to roughly a part in 104.

ISSN:0034-6748    

DOI:10.1063/1.1143423

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A system for tomography in the wavelength range 200–1100 nm has been designed for the Rijnhuizen Tokamak Project (RTP). The plasma is viewed from five directions in one poloidal plane with a total of 80 detectors. An optical imaging system consisting of two spherical mirrors for each viewing direction is used to combine a good spatial resolution (1 cm, the minor radius of RTP being 17 cm) with a sufficiently high signal level for the fast electronics (200 kHz). Because of the complexity of the imaging, implementation of the system into common tomography codes is not straightforward. Ray tracing is used to calculate the contribution of the local emissivities in the plasma to the measured signals of the various detectors.

ISSN:0034-6748    

DOI:10.1063/1.1143424

出版商:AIP    

年代:1992

数据来源: AIP