摘要:

Measurements of polarization of spectral lines emitted by tokamak plasmas provide information about the plasma internal magnetic field and the current density profile. The methods of polarization spectroscopy, as applied to the tokamak diagnostic, are reviewed with emphasis on the polarimetry of motional Stark effect in emissions of hydrogenic neutral beams.

ISSN:0094-243X    

DOI:10.1063/1.42477

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The identification of impurities and the investigations into their behaviour in magnetically confined plasmas as well as the plasma parameter determination belong to the most important applications of x‐ray spectroscopy in the JET and ASDEX tokamaks. Broad‐band flat crystal monochromators—supported by impurity monitors and calibration devices—enable impurity concentration and plasma radiation loss measurements over a wide range of atomic numbers, while high‐resolution spectroscopy offers plasma ion temperature and rotation measurements.

ISSN:0094-243X    

DOI:10.1063/1.42484

出版商:AIP    

年代:1992

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.42478

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Radio frequency (rf) plasmas are utilized in many applications in materials processing, such as semiconductor fabrication, surface modification, and coating. Plasma processing has replaced older techniques, such as wet chemistry, because the latter could not provide the necessary characteristics as process demands increased. A good example of this is the reduction of the feature size in semiconductors. The present critical dimension for semiconductor processing is 0.8 &mgr;m and is anticipated to be ≤0.25 &mgr;m by the year 2000. At present only plasma processing exhibits the potential of producing these line widths.An important factor, as the demands on the processing of materials become more critical, is exactly how to determine that the plasma is actually performing the process as designed. One way that is being investigated is to design control diagnostics that necessarily operate in real‐time,in situ, without significantly perturbing the process. Many such diagnostic methods have been proposed and are vigorously being investigated. They include probing the plasma with lasers, electric and mass selecting probes, and by observing the emission of radiation coming from the plasma. All of these and others must be investigated if the demands of material processing are to be met. Some of the methods being investigated for process control diagnostics are presented.

ISSN:0094-243X    

DOI:10.1063/1.42479

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Coronal elemental abundances are found to change by as much as an order of magnitude relative to those present in the solar photosphere. Observations of modifications in coronal elemenal abundances are reviewed and a tentative model governing the changes is discussed.

ISSN:0094-243X    

DOI:10.1063/1.42471

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Compact X‐ray sources derive their luminosities from the conversion of gravitational potential energy through accretion. A centrally‐produced hard X‐ray continuum photoionizes the surrounding accretion flow, which can produce discrete X‐ray emission. To date, as applied to compact X‐ray sources, a detailed diagnostic approach to the analysis of spectroscopic data has been largely ineffective, owing to the limited quality of available line spectra and the lack of appropriate models of X‐ray line emission in the presence of an ionizing continuum radiation field. We are involved in an atomic modeling program to investigate the discrete spectral response to variations in ambient plasma conditions, with the aim of establishing a new set of plasma diagnostics appropriate to this physical regime. We discuss the physical mechanisms and applications of several of the diagnostics which have been discovered in the Fe L‐shell spectrum, under conditions appropriate to X‐ray photoionized plasmas.

ISSN:0094-243X    

DOI:10.1063/1.42472

出版商:AIP    

年代:1992

数据来源: AIP