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:10.1063/1.1139974

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:10.1063/1.1139975

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Plasma tomographic reconstructions are subject to aliasing ambiguity as a result of the limited angular and radial sampling rates for the line‐integrated data. The two‐view interferometer installed on the Microtor tokamak yields unambiguous information, specifically, a collection of six low‐order alias‐free moments of the 2‐D electron density distribution. The unspoiled coefficients can be related to physically intuitive quantities and so yield information pertinent to the equilibrium and dynamical behavior of the plasma column. Alternatively, they can be used as constraints for a maximum entropy reconstruction of the source to produce an image free of aliasing artifacts.

ISSN:0034-6748    

DOI:10.1063/1.1140265

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

For the past four years, a Fourier transform spectrometer diagnostic system, employing a fast‐scanning polarizing Michelson interferometer (FMI), has been operating on the TFTR tokamak at the Princeton Plasma Physics Laboratory. It is used to measure the electron cyclotron emission (ECE) spectrum over the range 2.5–18 cm−1(75–540 GHz), with a resolution of 0.123 cm−1(3.7 GHz), at a rate of 72 spectra per second. The quasioptical system for collecting the light and transporting it through the interferometer to the detector has been designed using the concepts of both Gaussian and geometrical optics. The commercial FMI was custom made for this project and is the state of the art for this type of specialized instrument. The diagnostic system is described and an error propagation analysis of the absolute calibration process is given. Examples of ECE spectra measured in two polarization directions are given and electron temperature profiles derived from each of them are compared.

ISSN:0034-6748    

DOI:10.1063/1.1139976

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We describe a simple method of determining the plasma density unambiguously with the help of a microwave interferometer. The frequency of the Klystron source is modulated with the help of a staircase voltage pulse. The height of each staircase is adjusted in such a way that the corresponding phase shift is 90°. Signals proportional to the cosine and sine of the phase shift due to plasma are generated, and the plasma density is unambiguously measured. The advantages of the method are highlighted in the text.

ISSN:0034-6748    

DOI:10.1063/1.1139977

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The extraction of H−ions from a volume source is greatly improved by the presence of a weak magnetic field parallel to the plasma electrode that magnetically insulates this electrode from the bulk plasma. When biased positive, the plasma electrode depletes the electron population in the neighboring region. To maintain plasma neutrality, negative ions from the main plasma replace the electrons in this region. Thus a high fraction of negative ions builds up in front of the plasma electrode. The implications of these phenomena for negative ion beam formation are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1139978

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A method is described whereby a beam of positive hydrogen ions incident at grazing angles on an array of cesium‐covered tungsten foils is used to produce H0and H−particles by negative surface ionization. The results of these experiments indicate that the method can provide diagnostic beams of particles to hot plasmas and can also energy‐analyze charge exchange neutrals emerging from hot plasmas.

ISSN:0034-6748    

DOI:10.1063/1.1139979

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Several kinds of bending magnet systems are used in present neutral beam injectors. In these systems the fringe magnetic field due to finite dimensions of the bending magnet plays an important role in the ion beam deflection. The power deposition profile on the ion dump surface is strongly influenced by the exit angles of the reflected ions with respect to the magnet boundary. However, it is not easy to predict the exit angles of the ions because both focusing and defocusing forces act on these ions during their reflections, and hence it is difficult to predict whether the power density on the ion dump surface increases or decreases. In order to investigate the effect of the fringe magnetic field on beam reflection in a 180° bending magnet system, we calculate power deposition profiles on the ion dump surface by applying a Monte Carlo technique. The computational results show that the power deposition profile is very sensitive to change of the magnetic field strength. When the magnetic field strength increases by 5%, for example, the maximum power density shows an increase of 80%. We also compare the calculated power deposition profile with the experimentally measured profile. The measured profiles are in good agreement with the calculated ones without considering the beam expansion due to a space‐charge effect of the reflecting ions.

ISSN:0034-6748    

DOI:10.1063/1.1139980

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Formation of a straight helical magnetic field is attempted by using ferromagnetic material. A shaped ferromagnetic cylinder, which modifies an external uniform magnetic field, is demonstrated to realize anl=3 helical magnetic field that is suitable for plasma experiments. The measured values for the angle of rotational transform and shear length agree with the predictions within a factor of 2, which is calculated without taking account of the self‐demagnetization. This indicates that a rough configuration of magnetic field can be obtained even if the self‐demagnetization is not known accurately. It is also suggested that this method is widely applicable to the formation of other complicated configurations of magnetic field.

ISSN:0034-6748    

DOI:10.1063/1.1139981

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The design and operation of a novel Cs+ion source are described. It consists of a heated tantalum capillary connected to a heatable reservoir containing metallic cesium. Cs vapor streaming from the reservoir through the capillary is surface ionized at its inner wall. The ions emerging from the tip of the capillary are accelerated by a strong electric field between the tip and an acceleration electrode having a central bore. The virtual size of the source is about 10 &mgr;m in diameter. The source delivered a total current of 30 &mgr;A into a solid angle of ∼0.5 sr over a period of six weeks of uninterrupted operation on a charge of 0.5 g of metallic cesium.

ISSN:0034-6748    

DOI:10.1063/1.1139982

出版商:AIP    

年代:1988

数据来源: AIP