摘要:

An improved version of the initial x-ray ultraviolet spectrograph SPARTUVIX1 has been developed to record the time evolution of spatially resolved spectra in the soft x-ray range (from 30 to 300 Å). This diagnostic can be applied to the new class of laser produced plasma experiments now performed in order to better understand the physical evolution of x-ray indirect drive plasmas. Instead of a one-dimensional streak camera used for the first version, a new widely used 2-D soft x-ray time gated imager allows us to follow the time evolution of the spatially resolved soft x-ray spectra. This instrument was designed for plastic foam soft x-ray opacity measurements. The soft x-rays, emitted by an auxiliary radiography laser plasma source, are transmitted through the foam and dispersed into two parts (+1 and −1 order of the transmission grating). Each dispersed spectrum is placed on two different gated striplines of the soft x-ray imager and thus recorded at two different times (exposure time 300 ps, adjustable interframe 600 ps). The spatial resolution is obtained with a slit added in front of the spectrograph, that images the plasma onto the detector with a magnification ratio of 15 and a spatial resolution of 50 &mgr;m. A detailed description of this instrument and the main results obtained for two different plastic foam opacity measurements (undoped and doped with chlorine) will be presented. This work is supported by European Community Contract No. CEE/CHGF-CT-92-0016. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147922

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A number of diagnostics utilizing the radiation emitted from high-temperature plasmas have been developed at Los Alamos. Photoemissive x-ray diodes with photon energy bandpass filters provide time-resolved rough spectral data from about 6 eV to >10 keV photon energy. Filtered silicon photodiodes can be used down to 1 eV and offer the advantages of nominally flat response and ability to operate in poor vacuum conditions. Both types of diodes will provide a rough time-resolved spectrum and both are relatively inexpensive, reliable, and passive (i.e., no synchronization problems). For higher-energy resolution, bent crystal spectrographs are used in the x-ray region. With the addition of streak cameras or gated microchannel plates these systems provide data with high energy and high time resolution. To measure the total energy output, a thin foil bolometer is used that measures the change in foil resistance as it is heated by the plasma radiation. By combining these diagnostics into a complementary set good diagnostic information can be guaranteed on any plasma experiment.

ISSN:0034-6748    

DOI:10.1063/1.1147789

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

FoamZ-pinch experiments have recently been performed on SATURN to study issues associated with the initiation, acceleration, and stagnation phases of the pinch. Time-integrated x-ray crystal spectra have been recorded from experiments with 5 mg/cc Si aerogel loads and 10 mg/cc agar loads. In this article, we describe results from collisional-radiative equilibrium calculations performed to analyze the Si, Na, and SK-shell emission observed in the spectra. Particular attention is paid to density and opacity effects on intensity ratios involving He&agr;, He intercombination, and Li-like satellite lines. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147790

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Polarization spectroscopy of x-ray lines represents a diagnostic tool to ascertain the presence of electron beams in high-temperature plasmas. Making use of the Livermore electron beam ion trap, which optimizes the linear x-ray line polarization by exciting highly charged ions with a monoenergetic electron beam, we have begun to develop polarization diagnostics and test theoretical models. Our measurement relies on the sensitivity of crystal spectrometers to the linear polarization of x-ray lines which depends on the value of the Bragg angle. We employed two spectrometers with differing analyzing crystals and simultaneously recorded theK-shell emission from heliumlike Fe24+and lithiumlike Fe23+ions at two different Bragg angles. A clear difference in the relative intensities of the dominant transitions is observed, which is attributed to the amount of linear polarization of the individual lines. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148222

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A very high resolution vacuum flat-crystal spectrometer was constructed for analyzing soft x rays emitted by an electron beam ion trap. The spectrometer was designed to operate at large Bragg angles (&thgr;⩽85°) in order to maximize the spectral dispersion and thus the resolving power. Using a quartz (100) crystal at a Bragg angle of 82°, a measurement of the2p1/2,2p3/2→1s1/2transitions in hydrogenic Mg11+situated near 8.42 Å was made. The nominal resolving power of the instrument was better than 30 000 allowing us to infer the ion temperature (246±20 eV) from the observed line widths. A comparison with an existing flat-crystal spectrometer demonstrates the great improvement in resolving power achieved. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147791

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have performed high resolution extreme ultraviolet (EUV) photon and Auger electron measurements to elucidate single and double capture processes in Ne8++He single collisions at 80 keV impact energy. Numerous new transitions both in the Auger and the EUV spectra have been identified by means of extensive theoretical calculations and correlation diagrams. These data are of importance for the modeling of impurities in plasma and for future plasma diagnostics. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147792

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Solid and annular silicon aerogel and agar foams were imploded on the SATURN accelerator to study plasma initiation, acceleration, and stagnation. SATURN delivers 7 MA with a 50 ns rise time to these foam loads. We fielded several spectroscopic diagnostics to measure plasma parameters throughout thez-pinch discharge. A spatially resolved single frame time-gated extreme ultraviolet spectrometer measured the extent of plasma ablation off the surface of the foam. A time integrated crystal spectrometer showed that characteristicKshell radiation of silicon in the aerogel and of sulfur and sodium impurities in the agar were attenuated when the foam loads were coated with a conductive layer of gold. A time-resolved pinhole camera showed that in general the quality of the pinch implosions was poor but improved with increasing efforts to improve current continuity such as prepulse and conductive coatings. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147740

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

High-resolution reflection-type crystal spectrometers have been used for x-ray energies up to 13 keV, e.g., theK-shell radiation of heliumlike Kr. In order to extend crystal spectrometer measurements to higher energy x rays from higher-Zelements, we employ the crystal in transmission. The geometry we use is known as DuMond geometry. Using such a transmission-type crystal x-ray spectrometer, we have measured theK-shell radiation of various highly charged high-Zions. In particular, we present a measurement of the1s2p 1P1→1s2 1S0transition in heliumlike xenon, Xe52+. For this transition, we measure a linewidth of 34 eV, which demonstrates that the resolving power we achieved with the new spectrometer is on the order of 1000. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147793

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have applied a new, more efficient diagnostic technique for studies of extreme ultraviolet (EUV) radiation from multicharged ions interacting with He gas. Following single and double electron capture and one electron capture plus target-ion excitation in He2++He and Ar8++He collisions, the subsequent emitted EUV photons are analyzed with a high-resolution 2.2 m grazing incidence monochromator in conjunction with a new type of glass capillary converter (GCC) specifically designed for the EUV wavelength region. This new optical device images a horizontal cylindrical ion beam segment onto the vertical entrance slit of the monochromator. With this new imaging technique a spectral intensity enhancement of about 10 has been achieved over a distance of about 60 cm. By further optimizing this method an enhancement of the flux density of EUV radiation of about 20–30 is expected. As prototype examples, new advanced EUV spectra arising from He2++He and Ar8++He collisions are presented and discussed. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147794

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have calculated the polarization properties of dielectronic satellite lines in Li- and Be-like Fe ions excited through resonance electron capture by a monoenergetic electron beam. Following the density matrix formalism, we have computed the degree of polarization and the spectral intensity distribution of dielectronic satellites associated with a given polarization state. Theoretical results were compared with experiments performed at the Livermore Electron Beam Ion Trap where satellite line emission from Fe ions was simultaneously recorded with two crystal spectrometers. These results are relevant to diagnostic applications of x-ray line polarization spectroscopy in plasmas. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147795

出版商:AIP    

年代:1997

数据来源: AIP