摘要:

We have modeled the temperature and density dependence of the Li‐like satellites of the Ar He &bgr; line by performing NLTE kinetic modeling of level populations in conjunction with Stark broadening calculations. Composite line profiles are computed including resonance and satellite line transitions that have built‐in the temperature and density dependence characteristic of the level populations and Stark broadening of these transitions. These synthetic spectra can be used to analyze experimental data, providing a simultaneous diagnostic of temperature and density.

ISSN:0034-6748    

DOI:10.1063/1.1143458

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We describe a simple method for improving the spectral resolution of soft x‐ray and extreme ultraviolet spectrographs which use electro‐optical detector/intensifiers. In this method, the spectrometer is focused onto a narrow slit which is angled near 90° with respect to the dispersive axis and placed just in front of the detector. Proper choice of the width and angle of the slit is shown to have the effect of expanding the spectrum along the length of the slit to the point where the spatial resolution limitations of the detector are overcome.

ISSN:0034-6748    

DOI:10.1063/1.1143459

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Two‐dimensional, time resolved x‐ray imaging is a principal technique used to study hot plasmas produced in laser heated targets. It can be used to study laser energy deposition within the irradiation spot, the spatial and temporal dependence of laser to x‐ray conversion efficiency, electron transport and density profiles, mass ablation rates as well as x‐ray driven implosions in inertial confinement fusion experiments. We have successfully developed a new soft x‐ray framing camera which will allow us to record two‐dimensional images at different times almost simultaneously. It is a broadband diagnostic (100 eV≤&Dgr;h&ngr;≤400 eV) having three channels which can obtain x‐ray images at four different times from laser driven targets. Its current configuration includes one 500 eV, one 1.0 keV, and one ∼2.5 keV channels. The two low energy channels resulted from pairing transmission filters to grazing x‐ray mirrors. Other channel options can be implemented easily to measure other x‐ray energies. Four different striplines coated on a microchannel plate are gated at different times. Each strip records three different images taken nearly simultaneously, one image per channel. The result is 12 x‐ray images on film, four images per channel taken at four different times, with a nominal resolution of approximately 100 ps per image. The diagnostic’s spatial resolution is approximately 10 &mgr;m. We have already fielded this new instrument during x‐ray conversion experiments, using both low and highZtargets driven by 1–2 ns, ‘‘flattop’’ laser pulses. We will show the details of the instrument design and sample results from conversion experiments.

ISSN:0034-6748    

DOI:10.1063/1.1143460

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We describe the investigations of the plasma behavior in three pulsed‐power systems: a magnetically insulated ion diode, and plasma opening switch, and a gas‐puffedZpinch. Recently developed spectroscopic diagnostic techniques allow for measurements with relatively high spectral, temporal, and spatial resolutions. The particle velocity and density distributions within a few tens of microns from the dielectric‐anode surface are observed using laser spectroscopy. Fluctuating electric fields in the plasma are inferred from anisotropic Stark broadening. For the plasma opening switch experiment, a novel gaseous plasma source was developed which is mounted inside the high‐voltage inner conductor. The properties of this source, together with spectroscopic observations of the electron density and particle velocities of the injected plasma, are described. Emission line intensities during the switch operation are discussed. In theZ‐pinch experiment, spectral emission‐line profiles of various charge‐state ions are studied during the implosion phase. Radial velocity distributions are observed from the line Doppler shifts and widths.  

ISSN:0034-6748    

DOI:10.1063/1.1143461

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Atomic reaction models provide the link by which quantitative diagnostic comments on plasma behavior and parameters may be made from spectral observations of emission by ions in the plasma. This paper reviews progress in this area with emphasis on impurity species in magnetic confinement fusion plasmas. A systematic approach based on generalized collisional‐radiative theory is adopted and items discussed include spectroscopy of edge and divertor environments, beam emission, and charge exchange spectroscopy. Case studies are based on experience at the JET Joint European Torus Experiment.

ISSN:0034-6748    

DOI:10.1063/1.1143462

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The motional electric fieldE=v×B, wherevis the velocity andBis the tokamak magnetic field, produces a strong Stark effect in spectral lines emitted by hydrogenic neutral beams. The tilt angle of the magnetic field line, a quantity related directly to the distribution of the plasma toroidal current, is deduced from a measurement of the direction of polarization of the Stark components. In the DIII‐D tokamak, the Balmer‐&agr; line of deuterium emitted by one of the high‐power heating beams is analyzed. A multichord polarimeter measures the magnetic field pitch angle at eight spatial locations covering ∼0.6 of the nominal plasma diameter at the midplane outboard side. The diagnostic offers 2–8‐cm resolution in the major radius and 1‐ms integration time. The accuracy of the measurement of the polarization direction necessary for an adequate reconstruction of the current profiles is obtained with the use of active polarizing elements which produce high‐frequency intensity modulation with an amplitude related to the direction of linear polarization of the plasma radiation. The current profiles in highly shaped (noncircular) plasmas cannot be determined solely from the tilt angle measurements because they do not provide any information about the shape of magnetic surfaces. Thus, the polarization measurements are used in conjunction with a large set of external magnetic measurements (magnetic field and flux probes, diamagnetic loops, and Rogowski coils) by the magnetic field equilibrium code EFIT, and provide a constraint on the possible solutions for the current profile.  

ISSN:0034-6748    

DOI:10.1063/1.1143463

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The transient internal probe (TIP) diagnostic is a novel method for probing the interior of hot magnetic fusion plasmas. In the TIP scheme, a probe is fired, using a two‐stage light gas gun, through a hot plasma at velocities up to 5 km/s, and makes direct, local measurements of the internal magnetic field structure. The data are relayed to the laboratory optical detection system using an incident laser that is directed through a Faraday rotator payload acting as a magneto‐optic sensor. Ablative effects are avoided by minimizing the probe size, limiting the time that the probe is in the hot plasma, and encasing the probe with a diamond cladding. The degree to which the diamond probe cladding is susceptible to ablative effects will determine the plasma density and temperature regime in which the TIP diagnostic can be used. If the TIP suffers significant ablation it is an indication that the diagnostic is not usable on this hot and dense of a plasma (or that greater velocity must be imparted to the probe to further minimize the time that it is in the plasma). A quantitative experimental study of the ablation rates of diamond is planned as part of the TIP development. The integrated TIP system will be functional in 1992 and installed on the Helicity Injected Torus (HIT) [T. R. Jarboe, Fusion Tech.15, 9 (1989)] at the University of Washington.

ISSN:0034-6748    

DOI:10.1063/1.1143812

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Magnetic field profiles are measured continuously in space and time using Faraday rotation in magneto‐optic glass. A line focused laser beam which undergoes Faraday rotation within the glass element is imaged in one dimension through a polarizer and onto a streak camera. The system is described and used to characterize an exploding diamagnetic plasma cavity.

ISSN:0034-6748    

DOI:10.1063/1.1143464

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The density in a large tokamak such as International Thermonuclear Experimental Reactor (ITER), or any of the proposed future US machines, can be determined by measuring the Faraday rotation of a 10.6 &mgr;m laser directed tangent to the toroidal field. If there is a horizontal array of such beams, thenne(R) can be readily obtained with a simple Abel inversion about the center line of the tokamak. For a large machine, operated at a full field of 30 T m and a density of 2×1020/m3, the rotation angle would be quite large−about 60° for two passes. A layout in which a single laser beam is fanned out in the horizontal midplane of the tokamak, with a set of retroreflectors on the far side of the vacuum vessel, would provide good spatial resolution, depending only upon the number of reflectors. With this proposed layout, only one window would be needed. Because the rotation angle is never more than 1 ‘‘fringe,’’ the data is always good, and it is also a continuous measurement in time. Faraday rotation is dependent only upon the plasma itself, and thus is not sensitive to vibration of the optical components. Simulations of the expected results show that ITER, or any large tokamak, existing or proposed, would be well served even at low densities by a midplane Faraday rotation densitometer of ∼64 channels.

ISSN:0034-6748    

DOI:10.1063/1.1143465

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Although theqprofile plays a key role in theories of instabilities and plasma equilibrium, it has been quite difficult to measure until the recent development of the motional Stark effect (MSE) diagnostic. A multichannel motional Stark effect polarimeter system has recently been installed on the Tokamak Fusion Test Reactor (TFTR). The diagnostic can measure the magnetic field pitch angle [&ggr;p=tan−1(Bp/BT)] at ten radial locations. The doppler shiftedD&agr;radiation from a TFTR heating beam is viewed near tangential to the toroidal magnetic field via a re‐entrant front surface reflecting mirror. The field of view covers from inboard of the magnetic axis to near the outboard edge of the plasma with a radial spatial resolution of 3–5 cm. A high throughputf/2 optics system results in an uncertainty for &ggr;pof ∼0.1°–0.2° with a time resolution of ∼5–10 ms. Initial pitch angle profiles from TFTR have been obtained. The MSE data is consistent with the estimated magnetic axis position from external magnetic measurements and theq=1 radius is in good agreement with the inversion radius from the electron cyclotron emission temperature measurements.

ISSN:0034-6748    

DOI:10.1063/1.1143466

出版商:AIP    

年代:1992

数据来源: AIP