摘要:

In order to deduce the experimental beam conditions from the observed x‐ray line emission spectrum of highZelements, atomic radiative data for transition energies and oscillator strengths, ion‐atom impact ionization cross sections, Coster–Kronig yields, and fluorescence yield are needed. In this paper, we report on calculations to study the dependence of these atomic data on ionization stage. It has been found that proton impact ionization cross sections decrease slowly with increasing ionization stage, and the fluoresence yields have discrete jumps when the dominant Auger, Coster–Kronig transitions become energetically forbidden. Our study indicates that thermal ionization effects are not important for the dominantK‐,L‐, andM‐line emissions for plasmas withTe∼ 102eV.

ISSN:0034-6748    

DOI:10.1063/1.1143491

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

K&agr;satellite line emission from targets irradiated by intense light ion beams can be used to diagnose plasma temperatures and densities. The fluorescence lines are created as 2pelectrons drop down to fill 1svacancies that result from ion beam‐induced ionizations. We present results from collisional‐radiative equilibrium calculations for thin Al diagnostic layers to illustrate the dependence of theK&agr;emission spectrum on temperature, density, and layer thickness. We also discuss the effects of opacity on the spectrum and the contribution fromK&agr;transitions involving excited states.

ISSN:0034-6748    

DOI:10.1063/1.1143492

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Recent proton experiments on Particle Beam Fusion Accelerator II used a 2 &mgr;m gold foil cone to characterize the ion beam. Using the ion beam images obtained by viewing beam‐induced characteristic line radiation emitted by such foils with time‐integrated x‐ray pinhole cameras, the beam centroid axial location and azimuthal symmetry have been analyzed for a recent series of target shots. Azimuthal symmetry on the target midplane on individual shots varied from 6% to 29%. Averaged over the entire series of shots, inferred intensities on the target midplane varied by 24% to 37% from quadrant to quadrant. The beam profiles and beam reproducibility are vital to the interpretation of the results of these target experiments.

ISSN:0034-6748    

DOI:10.1063/1.1143493

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We performed experiments using proton beams to heat foam‐filled cylinders on the Particle Beam Fusion Acceleration II. Preliminary analysis of these diagnostic results provides reasonable agreement between prediction and experiment. The diagnostic package allowed us to benchmark target response as well as diagnose driver performance. Soft x‐ray images, both time and space resolved, and the results of broadband spectral measurements on bolometers and x‐ray diodes provide qualitative agreement with LASNEX predictions of target features such as Au motion and soft x‐ray emission profile. The analysis is consistent with a total beam deposition of 40–50 kJ and power depositions of approximately 180 TW/g. Estimates of target motion confirm the ability of the foam to retard wall motion.

ISSN:0034-6748    

DOI:10.1063/1.1143494

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Gating of microchannel plates (MCPs) can produce shutter times of less than 40 ps. This is accomplished with high‐fidelity electronic circuitry and short pulse (sub 80 ps) high‐amplitude electronic drivers. Measurements have shown that the fidelity of the electrical circuitry is one of the limiting factors in producing shorter x‐ray gating.

ISSN:0034-6748    

DOI:10.1063/1.1143495

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A streaked multiple pinhole camera technique, first used by P. Choi and co‐workers [C. Deeney and P. Choi, Rev. Sci. Instrum.60, 3558 (1989); P. Choi and R. Aliaga,ibid.61, 2747 (1990)] to record time‐ and two‐dimensional space‐resolved soft x‐ray images of plasma pinches, has been implemented on laser plasmas at NOVA. The instrument is particularly useful for time‐resolved imaging of small sources (<150 &mgr;m in size) such as implosions for which the necessary alignment accuracy is relaxed from ≤10 &mgr;m for a single pinhole, to 200 &mgr;m for a nine‐pinhole column. Results at 20 &mgr;m, 30‐ps resolution are presented for ≳2.5‐keV imaging, complementing the existing 1–3‐keV streaked x‐ray microscope capabilities at NOVA.

ISSN:0034-6748    

DOI:10.1063/1.1143496

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The capability for making ongoing characterization measurements of the spatial resolution and spectral reflectance of the Wo¨lter x‐ray optics used at Nova is essential for the interpretation of data taken with these imaging diagnostics. Equally important is an assessment of the long‐term performance of grazing incidence x‐ray optics used in the harsh environment of an ICF target chamber. We have designed and are currently building an off‐line facility for such a characterization. The facility will consist of an x‐ray source with specially designed pinhole‐target foil array, the Wo¨lter optics housing, monitoring and measuring detectors, a data acquisition system, and aninsitualignment system for rapid periodical verification. Each component of this lab will be discussed, along with possible initial results. This work was performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under contract No. W‐7405‐ENG‐48.

ISSN:0034-6748    

DOI:10.1063/1.1143497

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We have madeinsitumeasurements of the spatial resolution function for two sectors of the 22× magnification Wo¨lter x‐ray microscope. Our experimental technique using backlit grid shots on the Nova laser and our method of analysis are described.

ISSN:0034-6748    

DOI:10.1063/1.1143498

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We have developed a diagnostic suitable for high photon energy (∼7 keV) time resolved one‐dimensional x‐ray imaging on Nova. This diagnostic uses a 12 &mgr;m wide, 750 &mgr;m long imaging slit mounted on a 20× magnification snout which is coupled to an x‐ray streak camera of variable streak speed. The diagnostic fits into retractable manipulators on the ten‐beam chamber at Nova.Insitubacklit grid experiments using a large‐area backlighter give a spatial resolution full width at half‐maximum of about 15 &mgr;m with high brightness.  

ISSN:0034-6748    

DOI:10.1063/1.1143499

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We use annular apertures to produce coded images of inertial‐confinement fusion targets. The images are formed with 4–9‐keV x rays; they are unfolded to obtain high‐quality estimates of the source spatial distribution. Excellent time‐integrated images have been obtained using x‐ray film as a detector, and we are working to obtain time‐resolved images using a gated microchannel‐plate x‐ray detector. Preliminary resolution‐grid experiments show that the spatial resolution is ≤5 &mgr;m, and further experiments are planned to confirm a predicted resolution of ≤3 &mgr;m. We discuss the apertures, x‐ray detectors, and image‐processing software that forms this novel x‐ray microscope.

ISSN:0034-6748    

DOI:10.1063/1.1143500

出版商:AIP    

年代:1992

数据来源: AIP