摘要:

The properties of synchrotron radiation will be discussed and the outputs and characteristics of the storage rings available in the U.S. will be intercompared. The use of these sources for the radiometric calibration of plasma diagnostic instrumentation will be discussed in some detail. The importance of the proper treatment of polarization, overlapping orders, and solid angle effects will be covered. The experience gained at NBS in the calibration of plasma diagnostics instruments will be examined.

ISSN:0094-243X    

DOI:10.1063/1.33152

出版商:AIP    

年代:1981

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.33146

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Complex, transient, spatially inhomogeneous tokamak plasmas require careful diagnosis. As the reactor regime is approched, soft x rays become more important as a versatile diagnostic tool and an energy‐loss mechanism. Continuum emission provides a measure of electron temperatures and light impurity content. Impurity lines serve as a probe for ion and electron temperature, impurity behavior, and radiative cooling. The entire spectrum yields vital information on instabilities and disruptions. The importance of impurities is illustrated by the extensive efforts toward understanding impurity production, effects, and control. Minute heavy impurity concentrations can prevent reactor ignition. Si(Li)‐detector arrays give a broad overview of continuum and line x‐ray emission (.3−50 keV) with moderate energy (200 eV) and time (50 ms) resolution. Bragg crystal and grating spectrometers provide detailed informaion on impurity lines with moderate to excellent (E/&Dgr;E=100−23,000) resolving power and 1−50 ms time resolution. Imaging detector arrays measure rapid (∼10 &mgr;s) fluctuations due to MHD instabilities and probe impurity behavior and radiative cooling. Future tokamaks require more diagnostic channels to avoid spatial scanning; higher throughput for fast, single‐shot diagnosis; increased spectral information per sample period via fast scanning or use of multi‐element detectors with dispersive elements; and radiation shielding and hardening of detectors.

ISSN:0094-243X    

DOI:10.1063/1.33150

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The light ion fusion program is expected to achieve breakeven conditions in an inertial fusion target in experiments on the PBFA II accelerator. This goal is expected to require ion power densities of ≲1014W/m2. The diagnostics which have been employed to diagnose this deposition are described and some soft x‐ray plasma measurements which have been made on targets on the 200 times smaller Proto I accelerator are presented. Plasma brightness temperatures of 20 eV have been observed in the deposition region and 35 eV (100 eV electron temperature) in the stagnation region of imploding conical Al targets on Proto I.

ISSN:0094-243X    

DOI:10.1063/1.33173

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A ompat, efficient, high‐brightness pulsed plasma x‐ray source has been demonstrated. The source has a conversion efficiency, from electrical input to usable x‐ray energy, of greater than 1%. For example, total radiated yields of 150 joules of neon K‐line radiation have been produced in a single pulse. X‐rays are emitted from a cylindrical volume approximately 1 mm in diameter and 10 mm long. Various wavelengths can be obtained by the choice of appropriate plasma materials. This x‐ray source compares favorably to synchrotron radiators in intensity, and most users of synchrotrons will find this source attractive.

ISSN:0094-243X    

DOI:10.1063/1.33136

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

We present measurements of the sub‐kilovolt X‐ray emission from imploding wire arrays on the 1 TW BLACKJACK 3 pulsed power generator. The plasma is created by driving a 1 MA, 100 ns current pulse through a cylindrical array of 12 fine wires. The wires form individual plasmas which then implode to become a single plasma on the axis of the array; this hot, dense plasma is an intense source of soft X‐rays. Calorimeter measurements show that maximum soft radiation yield is produced from arrays having a linear density of 100 to 200 &mgr;g/cm; for such arrays the implosion occurs within 20 ns of the current peak. The dependence of the total yield on mass is largely independent of wire material. The radiation pulsewidth measured with an unfiltered X‐ray diode increases monotonically with array mass from a 25 ns FWHM observed for 50 &mgr;g/cm arrays.The soft X‐ray spectra radiated by the imploding plasmas approach a blackbody spectrum with increasing wire mass and atomic number. Tungsten and silver plasmas radiate continuum spectra in the sub‐kilovolt range; no lines are discernable in either case. Stainless steel plasmas radiate a similar continuum, but L and M lines are present for lower mass arrays. The continuum radiated by aluminum plasmas is less smooth, and significant K and L lines are present for lower masses. Carbon plasmas radiate intense K and L lines and an optically thin continuum. Similar soft X‐ray emissions can also be achieved with small imploding gas jet plasmas.

ISSN:0094-243X    

DOI:10.1063/1.33142

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Photoemission has been studied for nearly 100 years as both a means of investigating quantum physics, and as a practical technique for transducing optical/x‐ray photons into electrical currents. Numerous x‐ray detection schemes, such as streak cameras and x‐ray sensitive diodes, exploit this process because of its simplicity, adaptability, and speed. Recent emphases on diagnostics for low temperature, high density, and short‐lived, plasmas for inertial confinement fusion has stimulated interest in x‐ray photoemission in the sub‐kilovolt regime. In this paper, a review of x‐ray photoemission measurements in the 50 eV to 10 keV x‐ray region is given and the experimental techniques are reviewed. A semiempirical model of x‐ray photoemission is disussed and compared to experimental measurements. Finally, examples of absolutely calibrated instruments are shown.

ISSN:0094-243X    

DOI:10.1063/1.33143

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Techniques for time‐resolved x‐ray diagnostics will be reviewed with emphases on systems utilizing x‐ray diodes or scintillators. System design concerns for high‐bandwidth (≳1 GHz) diagnostics will be emphasized. The limitations of a coaxial cable system and a technique for equalizing to improve bandwidth of such a system will be reviewed. Characteristics of new multi‐GHz amplifiers will be presented. An example of a complete operational system on the Los Alamos Helios laser will be presented which has a bandwidth near 3 GHz over 38 m of coax. The system includes the cable, an amplifier, an oscilloscope, and a digital camera readout.

ISSN:0094-243X    

DOI:10.1063/1.33144

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A Soft X‐ray Streak Camera (SXRSC) is a fast timing instrument sensitive to x rays from 100 eV to 30 keV. The instrument has excellent time resolution (∼15 ps) and large dynamic range (∼103) which are well suited for measuring x‐ray pulses produced by laser‐fusion targets. The SXRSC uses a thin transmission photocathode to convert x‐rays to a secondary electron signal which is acelerated, focused, and deflected onto a phosphor producing an image of the x‐ray pulse time history. In the past, such instruments have been used only to make relative measurements of the time history. At LINL we have calibrated the SXRSC in order to make absolute intensity measurements of the soft x‐ray flux from laser fusion targets. Such measurements will assist in understanding the laser plasma processes and conditions needed to attain laser‐produced fusion. Because of the nature of the instrument, we have calibrated it in the dynamic mode using a small laser‐produced pulsed x‐ray source. Details of the calibrations will be given. We have measured the SXRSC response to be linear over more than two orders of magnitude with the range limited by the x‐ray source strength. The dynamic range of similar instruments sensitive to optical light has been demonstrated to be greater than 103. Based on first generation calibrations, flux measurements are accurate to ±30% with the largest uncertainty in the calibrations being in determining the source spectrum and intensity. The uncertainties can possibly be reduced by a factor of two by better source characterization. In that case errors in SXRSC measurements would approach those of other x‐ray pulse detectors, such as x‐ray diodes.

ISSN:0094-243X    

DOI:10.1063/1.33145

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

X‐ray detectors which register the position of photon arrival are widely used. Parameters for the characterization and compression of detectors are reviewed prior to a survey of the types of available area x‐ray detectors. Research opportunities for improvement of existing systems and development of new detectors are numerous. Potential x‐ray projects involving adaptation of detectors employed at infrared and visible wavelengths are suggested. The development and characterization of x‐ray detectors is a field full of both intellectual challenges and practical applications.

ISSN:0094-243X    

DOI:10.1063/1.33147

出版商:AIP    

年代:1981

数据来源: AIP