摘要:

In experiments with intense x‐ray pulses, perturbations of the signal in traversing a diagnostic line‐of‐sight channel connecting source and detector can be large, requiring detailed computations to infer true characteristics of the signal. These perturbations fall in the most difficult class, being highly nonlinear (especially with respect to frequency) and time dependent. They cause the transmission of collimators and vacuum windows to change continuously as these apertures heat, ionize, and expand under intense irradiation; similarly the fluorescence efficiency of a scattering foil, the transmission of a filter, the reflectivity of a multilayer mirror, etc., can change significantly over the x‐ray pulse duration. We discuss the problem of modeling x‐ray transport through the ablation plasmas created by the intense signal, focusing on the questions: What are the sources of systematic error in our calculations that limit our ability to correct for aperture closure effects and how can the size of perturbations be minimized by careful design of the line‐of‐sight channel? This work was performed under the auspices of the U. S. DOE by the LLNL under Contract No. W‐7405‐ENG‐48.

ISSN:0034-6748    

DOI:10.1063/1.1140084

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The TFTR vertical x‐ray crystal spectrometer has now been operating with three crystals and position‐sensitive detectors according to the original design specifications. The observed spectra of heliumlike Tixxi, Crxxiii, Fexxv, and Nixxviihave permitted a detailed comparison with the predictions from atomic theories, and they have provided data on the radial profiles of the ion temperature and toroidal rotation velocity, as well as the radial ion charge‐state distribution in TFTR discharges. Central ion temperatures of 20 keV and central plasma rotation velocities of 5×105m/s have been recorded from plasmas with auxiliary neutral beam heating. These experimental results are presented. Also discussed are further instrumental improvements, such as the installation of two additional crystals and detectors and the installation of &ggr; and neutron shielding, which will make it possible to measure under full DD and DT operation with 27 MW of neutral beam injection where neutron production rates of 1019neutrons/s are expected.

ISSN:0034-6748    

DOI:10.1063/1.1140086

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The TFTR horizontal x‐ray crystal spectrometer has been improved by installation of &ggr; and neutron shielding and is now operating in the TFTR Test Cell up to the presently maximum neutron production rates of 2×1016neutrons/s. Further optimization by using a modified detector may assure operation of the spectrometer during the DT phase when TFTR is covered by an igloo. The instrument is set up for simultaneous observation of the entire satellite spectrum of Nixxvii, and it provides data on the time evolution of the central ion temperature and the central plasma rotation velocity. Ion temperatures of 20–30 keV have been measured under ‘‘supershot’’ conditions. The highest rotation velocity observed with unidirectional injection was 1.1×106m/s.

ISSN:0034-6748    

DOI:10.1063/1.1140087

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

X‐ray streak cameras, which can be coupled to a large variety of spectroscopic or imaging devices, provide an important research tool for studying laser fusion plasmas. Generally, several of these instruments are deployed simultaneously on a given experiment to furnish a comprehensive data set of the x‐ray emission spectrum and target hydrodynamics. Of particular importance is the ability to do quantitative analysis with the data set. This allows meaningful comparisons to be made with simulations. The sophistication of the hydrodynamic and atomic physics codes is such that qualitative analysis is insufficient. Various simple parameters in these codes are bench‐marked against experimental measurements before more detailed calculations are performed. As in all diagnostic systems the range of linear response must be well defined. In this article we will discuss some of the constraints inherent in streak camera systems and how they affect the acquisition and analysis of the experimental results. Examples illustrating our current capabilities for diagnosing experiments on the OMEGA laser fusion facility will be presented.

ISSN:0034-6748    

DOI:10.1063/1.1140088

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A review of the diagnostics used at Sandia National Laboratories to measure the parameters of intense proton and lithium beams generated on the PBFA‐II accelerator will be presented. These diagnostics consist of several types, namely:K&agr; x‐ray pinhole cameras, a multiframedE/dxion pinhole camera, ap‐i‐narray ion pinhole camera, Thomson parabola spectrographs, a Rutherford magnetic spectrograph, plasma visible spectroscopy, and several nuclear activation diagnostics. These components, when taken together, enable a rather thorough description of the 5‐MV, 10‐TW ion beams presently being produced. A unique feature of these diagnostics is that they are capable of operating in hard (several MeV) x‐ray bremsstrahlung backgrounds of some 109–1010rad/s. Details of each diagnostic, its integration, data reduction procedures, and recent PBFA‐II data will be discussed.

ISSN:0034-6748    

DOI:10.1063/1.1140089

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Radiation losses from the main plasma of the JAERI Tokamak‐60 (JT‐60) were measured by a 15‐channel bolometer array and those from divertor chambers in the ion and electron drift sides were each measured by two bolometers. The bolometric detector consisting of three layers (5‐&mgr;m‐thick gold absorber, 7‐&mgr;m‐thick polyimide foil, and 0.1‐&mgr;m‐thick gold resistor grid) was developed for this measurement. In typical diverted discharges with NB heating, the ratios of power radiated from the main and divertor chambers to the absorbed power were approximately 10% and 20%, respectively. Intense poloidal asymmetries of radiated power localized near theXpoint outside the torus were observed in diverted discharges. The profiles of the radiated power were reconstructed by an Abel inversion with an asymmetric term. On the other hand, a poloidally asymmetric radiation band localized near the inner wall, ‘‘marfe,’’ was observed for dense plasmas in limiter discharges with neutral beam heating.

ISSN:0034-6748    

DOI:10.1063/1.1140090

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Co‐ and counter‐viewing bolometers aimed along a common tangency chord are being used to study power losses due to charge exchange (CX) of fast ions in neutral beam injection (NBI) heated TFTR plasmas. For unidirectional injection, tangential bolometers oriented to view CX loss of circulating fast ions detect losses from the thermal target plasma (impurity radiation and CX) plus power due to the fast ion CX loss, whereas bolometers oppositely directed measure only the target plasma contribution. The difference between the two signals is a measure of the fast ion CX loss. Additional information is obtained by comparing the tangential bolometer signals with those of perpendicularly viewing bolometer monitors and arrays. The measurements are compared to results of the TRANSP code analysis.

ISSN:0034-6748    

DOI:10.1063/1.1140091

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Designing bolometers for Compact Ignition Tokamak presents difficult, perhaps insurmountable, challenges. Detector environment will be quite harsh, viewing access will be severely limited, and, most importantly, the heating of detectors by neutron and gamma radiation will be larger than that by the radiation losses to be measured. Furthermore, the radiation losses themselves will no longer be dominated by impurity radiation as in earlier machines, but will be a combination of impurity radiation, bremsstrahlung, and synchrotron radiation. Possible approaches to a design have been developed, based on optimizing the response to VUV‐ and x‐radiation, possible local shielding, subtraction of thenand &ggr; heating, constantinsitucalibration, and deployment of the detectors in a tangentially viewing array. The array makes it possible to cover the plasma cross section, as well as to see into the divertors. Estimates indicate that it should be possible to make successful measurements of the two‐dimensional radiation loss profile.

ISSN:0034-6748    

DOI:10.1063/1.1140092

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Local measurements of plasma radiation in the near infrared using the detection system of the ASDEX Thomson scattering device are reported. Comparison with hydrogen bremsstrahlung yieldsZeffprofiles. Good agreement with values from other diagnostics is obtained.Zeffbehavior in a variety of ASDEX discharges is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1140093

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The power flow to the DIII‐D divertor targets is routinely measured using infrared (IR) thermography. An IR television camera sensitive to radiation in the 8–12‐&mgr;m range views the divertor region using a set of germanium optics. Digital signal processing is used to extract the desired surface temperature profiles from the analog data (&bartil;12 Mbytes) stored on videotape. Inversion of these data using a simple matrix formulation of the inverse heat conduction problem then yields the incident heat flux as a function of space and time. Results from a DIII‐D discharge are included.

ISSN:0034-6748    

DOI:10.1063/1.1140040

出版商:AIP    

年代:1988

数据来源: AIP