摘要:

Measurement of intrinsic and injected impurity concentrations and transport in tokamak plasmas by x‐ray pulse‐height analysis (PHA) and x‐ray imaging (XI) diode arrays requires reliable excitation rates for a number of charge states of a range of elements (Al, Se, Ti, Cr, Fe, Ni, Ge, etc.). Previous PHA measurements at Princeton have relied on a coronal‐equilibrium average of excitation rates for iron, and a prescription for scaling the average rate to nearby elements. For improved accuracy in PHA measurements (using the MIST impurity equilibrium and transport code) and for interpretation of XI data (using an x‐ray simulation code), rates for excitation of dominant charge states by electron impact, dielectronic recombination, and radiative recombination have been calculated from available atomic data and parametrized as a function of atomic number (Z=10–42) and electron temperature (Te=0.1–10.0 keV).

ISSN:0034-6748    

DOI:10.1063/1.1140072

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Time‐resolved measurements from an elliptical crystal spectrograph are used to diagnose x‐ray laser experiments on a gas puff Z pinch. The elliptical spectrograph (1.2‐m working distance, eccentricity 0.9586) observes the 1‐keV region, covering a range of &lgr;/2d= 0.5 to 0.9. A thin filter (0.2 &mgr;m Al on 2 &mgr;m Kimfol) stretched across the spectrograph exit slit acts as a low‐energy x‐ray cutoff and as a vacuum window, allowing the detector to be at high vacuum regardless of the pressure in the experimental chamber. The detector consists of a seven‐frame microchannel‐plate intensifier system. A pulser is used to gate each of seven striplines on the microchannel plate, providing nanosecond resolution. With this instrument we are able to measure the pump radiation from the imploding plasma (Ne or Ar) and converter layer (Al), and to study the lasant ionization state (Ne‐like Ni or Cu).

ISSN:0034-6748    

DOI:10.1063/1.1140073

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A two‐dimensional, tangentially viewing, soft‐x‐ray pinhole camera has been fabricated to provide internal shape measurements on the PBX‐M tokamak. It consists of a scintillator at the focal plane of a foil‐filtered pinhole camera, which is, in turn, fiber‐optically coupled to an intensified framing video camera (&Dgr;t≥3 ms). Automated data acquisition is performed on a stand‐alone image processing system, and data archiving and retrieval take place on an optical disk video recorder. The derivation of the poloidal emission distribution from the measured image is done by fitting to model profiles.

ISSN:0034-6748    

DOI:10.1063/1.1140074

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Target diagnostics on PBFA II will include a time‐resolved x‐ray diode array, an energy‐resolved, time‐integrated x‐ray camera, and a grazing incidence spectrometer. A clean vacuum, independent of that on PBFA II, will be supplied to the detectors to maintain more reproducible calibrations. We also describe the diagnostics and outline the calculations which determined the shielding required. Based on the calculations the background due to bremsstrahlung in the least sensitive diagnostic is 12 eV/pixel. The appropriate shielding is being built to field these diagnostics.

ISSN:0034-6748    

DOI:10.1063/1.1140075

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

XUV diagnostic equipment was designed and utilized on the OMEGA target chamber at the University of Rochester to study high atomic number plasma generation by two‐wavelength laser excitation. Spectral data were collected from silver tracer dot targets irradiated with 1/3 TW of 0.35‐&mgr;m laser light of the multiple‐beam OMEGA laser and the single synchronized 1.06‐&mgr;m beam of the GDL laser for generating energetic electrons. XUV spectral data in the 30–300‐A˚ region were obtained with both a 3‐m grazing incidence spectrograph and a compact 1‐m grazing incidence spectrograph designed for reentrant mounting in the OMEGA chamber. High‐resolution x‐ray spectra were acquired in the 3.6–4.2‐A˚ region with a dual, flat‐diffraction crystal spectrograph. A low‐resolution x‐ray spectrum of silver was recorded with a curved mica spectrograph. Some x‐ray spectral lines appeared only when both OMEGA and GDL beams were used. These were identified as 2p–3s,3dtransitions in F‐like Ag xxxix. F‐, Na‐, and Mg‐like lines were found in the grazing incidence spectra, with F‐like lines appearing only with 1.06‐&mgr;m irradiation.

ISSN:0034-6748    

DOI:10.1063/1.1140076

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A transmission grating streaked spectrograph (SPARTUVIX) has been developed at the Centre d’Etudes de Limeil‐Valenton for measuring the temporal evolution of soft‐x‐ray spectra in laser‐produced plasmas. In this article the ideas behind the instrument are described as well as a description of the actual working diagnostic and its relevant components. This diagnostic has been used to look at the time behavior of x‐ray laser emission, and a number of very interesting results have been obtained. A representative sample of these results will also be shown.

ISSN:0034-6748    

DOI:10.1063/1.1140268

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Biplanar vacuum diodes, long used for the diagnostics of laser‐produced plasmas, have also been used as spectroscopic survey instruments for magnetically confined plasmas. The compact seven‐channel diode array, developed at KMS Fusion, provides broadband (&Dgr;E/E&bartil;1) channels of filtered cathodes to provide the spectral scan from 10 eV to about 5 keV (approximately 130 to 0.25 nm). Preliminary calibration results and calculations for a number of filters and cathodes are used to demonstrate that a satisfactory energy region may be obtained if an absorption edge of the cathode is below the mean energy of the desired channel and an absorption edge of the filter is above that energy. These devices are insensitive to neutron and gamma flux.

ISSN:0034-6748    

DOI:10.1063/1.1140077

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Requirements for continuous operation of photodiodes in the presence of nuclear radiation has led to the development of a novel AlGaAs/GaAs photodiode. Device structure and semiconductor properties of this design were optimized to balance the need for photodetection at &lgr;=820 nm against unwanted excess photocurrents induced by ionizing radiation. To achieve radiation hardness the photodiode employs a double‐heterojunction device structure. The spectral response of this detector, 1 keV–10 MeV, may offer unique opportunities for use in high‐temperature plasma diagnostics compared to typical bare Si:p‐i‐nx‐ray photodiode characteristics. Application of this AlGaAs/GaAs detector in a fiber‐optic link will be reviewed. Also, use of this detector in simple atomic‐absorption‐edge filtered x‐ray detector channels is presented.

ISSN:0034-6748    

DOI:10.1063/1.1140078

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The absolute x‐ray response of 18 EG&G Ortec partially depleted silicon surface‐barrier diodes (SBDs) have been measured at 8 and 17.5 keV. In addition we have examined the x‐ray response of four Tennelec and two United Detector Technology partially depleted SBDs. The variation in response to 8 keV x rays, for which the optical depth is about five, is comparatively slight (≲12%). The variation in response to 17.5 keV x rays, for which the optical depth is only ∼0.7, is comparatively large (∼100%). These variations are mainly attributable to differences in the SBD physical thicknesses, and thus to differences in optical depth. At both 8 and 17.5 keV the diodes respond linearly to large variations in incident flux (over three orders of magnitude). This linearity, and the diode x‐ray response in general, is insensitive to large changes in the detector bias voltage; thus the depletion depth, proportional to the square root of the bias voltage, does not play a critical role in determining the x‐ray sensitive depth. It is important to emphasize that this finding is contrary to the commonly held belief that the x‐ray sensitive depth is equivalent to the depletion depth. In addition this result has a direct bearing on both SBD and PIN detectors intended for fully depleted operation, but used in an underbiased mode such that they are actually partially depleted. We conclude that SBDs have attractive features for quantitatively measuring x radiation from high‐intensity sources for whichh&ngr;≳10 keV.

ISSN:0034-6748    

DOI:10.1063/1.1140080

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Laser‐target interaction was studied to make an efficient soft‐x‐ray source with a table‐top laser system. A 1‐J, 20‐ns ruby laser was focused on various planar targets (Z=6 to 82). The laser power intensity on the targets was about 1011–1012W/cm2. Spectra (2–35 nm) and intensities of soft x‐ray radiation from target plasma were measured by using a 2‐m grazing incidence spectrometer and a x‐ray diode. Even at this low laser power intensity, high‐energy radiation of 0.5–3 keV was obtained. Spectra from low‐Zmaterials show strong line radiations over a weak continuum and those from high‐Zmaterials consist of a continuum predominantly. The targetZ‐number dependence of the intensity of 0.5–3‐keV radiation has a periodic structure and relates to atomic shell structures. In this experiment the maximum x‐ray conversion efficiency was obtained from a22Ti target.

ISSN:0034-6748    

DOI:10.1063/1.1140082

出版商:AIP    

年代:1988

数据来源: AIP