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Plasma studies in a low pressure high frequency discharge
215
Abstracts Of perhaps more importance is the question of the stability of such plasma-field configurations, and a detailed description has been prepared of a model experiment designed to test this crucial point. The apparatus will generate and utilize millisecond pulses of RF energy at a power level of one to ten megawatts; conditions which are easily attainable by present engineering methods. The question of energy exchange between reaction products and the field is being studied theoretically, as are other general features of plasma interaction with radio-frequency fields. The latest results of these studies will be incorporated in the final paper. This communicadoi presents joint work by A. J. HATCH. P. J. PERSIANI.A. J. ULRICH. and the author, ail of the Argonne National Ldboratory.
plasmoids, characterized by extremely welldefined boundaries, have been observed by WOODY and others6 in a multipacting plasma. The significance of plasmoids in r.f. thermonuclear work appears to lie in their r.f. shielding characteristics. (3) Penetration of the plasma and plasmoids by r.f. fields in the presence of static transverse magnetic fields. Theoretical studies by M. H. JOHNSON~indicate the possibility of r.f. field penetration and subsequent heating of ions by r.f. in such systems. Methods of investigating these plasma features and preliminary experimental results will be discussed. GILL,
E. W. B. and “ON ENGEL, A. Proc.
Roy.
A192.446(1948). ’HATCH. A. J. and WILLIAMS. H. B.. Jour.
Phys. 25, Ii, 7 (1 OS‘0 ’ WILLIAMS, H. B.. Phys. Rev. 107,145l (1957). 4 WOOD, R. W.. Phys. Rev. 35,673 (1930). ’ HATCH, A. J. and WILL.I*MS, H. B.. unpublished. (Th&e plasmoids appear to be distinctly different from those described by W. H. BOSTICK.) ’ JOHNSON.M. H.. UCRL 4388, especially Lecture 3.
,.. \.__.,.
P/351. Plasma Studies in a Low Pressure High Frequency Discharge. ALBERT J. HATCH (U.S.A.). A basic experimental study of high frequency containment and heating phenomena pertinent to thermonuclear processes has been undertaken at Argonne National Laboratory. The multipatting mechanism of low pressure high frequency discharge is utilized as a plasma source. In this mechanism, also known as secondary electron resonance or electrodeless discharge, electrons have nominal 4 cycle inter-electrode transit times and electron multiplication is by secondary emission at the electrode surfaces.1,2 The mechanism occurs at pressures of the order of 1O-3 mm Hg and lower, a range of interest in thermonuclear work. Electron energies (ordered) are typically in the range of 50 to 5000eV. Previous observations have demonstrated that ions leave the discharge region with energies of the order of l&100 eV. The experimental apparatus to be described incorporates a CW 1 kilowatt 3-50 MC r.f. generator. A demountable double-ended glass bell jar, 30 cm diameter by 45 cm long, contains a pair of 25 cm diameter plane parallel metal electrodes with separation adjustable up to 30 cm. Pressures used are in the range of 10-l to 1O-5 mm Hg. The relatively large plasma volume reduces the problem of plasma disturbance by the probes. Among the plasma features which are being studied are the following: (1) Characteristics of a 3-dimensional potential well for ions due to excess negative space charge produced by the multipacting mechanism. Preliminary studies of this well suggest its possible application as a thermonuclear containment mechanism.3 (2) Characteristics of r.f. excited plasmoids believed to be the result of large scale longitudinal plasma oscillations. Such
Sm. (London)
Appl.
P/352. Experimental Pinch Stabilization with Large Axial Magnetic Field. DAVID F. BROWER, MARTIN
ROBERT STEARNS
E. DUNAWAY,
and
J. MALMBERG,
MARTIN 0.
STERN
(U.S.A.). A solution of the stabilization problem in discharges in gases is one of the primary purposes of experimental work in controlled thermonuclear reactions at this time. The employment of an axial magnetic field contained within the pinching plasma is a means of providing tension in the pinch discharge to counteract the negative tension of the orthogonal magnetic field produced by the pinching current itself. Experimental equipment has been made to produce very high axial magnetic fields of 40,000 gauss so that correspondingly large pinch currents can be employed. An important matter to consider and to test experimentally is the influence of the axial magnetic field not trapped within the pinch discharge. Control of the magnitude and direction of this exterior magnetic field has been attempted and the influence of its magnitude and direction on stability has been studied. Results of experiments now underway will be reported. P/354.
Stability of a Linear Pinch.
SUYDAM
BERGEN
R.
(U.S.A.).
A variation
by I. B. and R. M. KULSRUD for hydromagnetic stability problems, has been applied to the study of a linear, axi-symmetric pinch. It is shown by physical reasoning that a certain class of modes is particularly likely to be unstable, and the class of modes thus singled out is then studied with the
BERNSTEIN,
E.
principle,
A.
FRIEMAN,
developed M.
D.
KRUSKAL
Abstracts Of perhaps more importance is the question of the stability of such plasma-field configurations, and a detailed description has been prepared of a model experiment designed to test this crucial point. The apparatus will generate and utilize millisecond pulses of RF energy at a power level of one to ten megawatts; conditions which are easily attainable by present engineering methods. The question of energy exchange between reaction products and the field is being studied theoretically, as are other general features of plasma interaction with radio-frequency fields. The latest results of these studies will be incorporated in the final paper. This communicadoi presents joint work by A. J. HATCH. P. J. PERSIANI.A. J. ULRICH. and the author, ail of the Argonne National Ldboratory.
plasmoids, characterized by extremely welldefined boundaries, have been observed by WOODY and others6 in a multipacting plasma. The significance of plasmoids in r.f. thermonuclear work appears to lie in their r.f. shielding characteristics. (3) Penetration of the plasma and plasmoids by r.f. fields in the presence of static transverse magnetic fields. Theoretical studies by M. H. JOHNSON~indicate the possibility of r.f. field penetration and subsequent heating of ions by r.f. in such systems. Methods of investigating these plasma features and preliminary experimental results will be discussed. GILL,
E. W. B. and “ON ENGEL, A. Proc.
Roy.
A192.446(1948). ’HATCH. A. J. and WILLIAMS. H. B.. Jour.
Phys. 25, Ii, 7 (1 OS‘0 ’ WILLIAMS, H. B.. Phys. Rev. 107,145l (1957). 4 WOOD, R. W.. Phys. Rev. 35,673 (1930). ’ HATCH, A. J. and WILL.I*MS, H. B.. unpublished. (Th&e plasmoids appear to be distinctly different from those described by W. H. BOSTICK.) ’ JOHNSON.M. H.. UCRL 4388, especially Lecture 3.
,.. \.__.,.
P/351. Plasma Studies in a Low Pressure High Frequency Discharge. ALBERT J. HATCH (U.S.A.). A basic experimental study of high frequency containment and heating phenomena pertinent to thermonuclear processes has been undertaken at Argonne National Laboratory. The multipatting mechanism of low pressure high frequency discharge is utilized as a plasma source. In this mechanism, also known as secondary electron resonance or electrodeless discharge, electrons have nominal 4 cycle inter-electrode transit times and electron multiplication is by secondary emission at the electrode surfaces.1,2 The mechanism occurs at pressures of the order of 1O-3 mm Hg and lower, a range of interest in thermonuclear work. Electron energies (ordered) are typically in the range of 50 to 5000eV. Previous observations have demonstrated that ions leave the discharge region with energies of the order of l&100 eV. The experimental apparatus to be described incorporates a CW 1 kilowatt 3-50 MC r.f. generator. A demountable double-ended glass bell jar, 30 cm diameter by 45 cm long, contains a pair of 25 cm diameter plane parallel metal electrodes with separation adjustable up to 30 cm. Pressures used are in the range of 10-l to 1O-5 mm Hg. The relatively large plasma volume reduces the problem of plasma disturbance by the probes. Among the plasma features which are being studied are the following: (1) Characteristics of a 3-dimensional potential well for ions due to excess negative space charge produced by the multipacting mechanism. Preliminary studies of this well suggest its possible application as a thermonuclear containment mechanism.3 (2) Characteristics of r.f. excited plasmoids believed to be the result of large scale longitudinal plasma oscillations. Such
Sm. (London)
Appl.
P/352. Experimental Pinch Stabilization with Large Axial Magnetic Field. DAVID F. BROWER, MARTIN
ROBERT STEARNS
E. DUNAWAY,
and
J. MALMBERG,
MARTIN 0.
STERN
(U.S.A.). A solution of the stabilization problem in discharges in gases is one of the primary purposes of experimental work in controlled thermonuclear reactions at this time. The employment of an axial magnetic field contained within the pinching plasma is a means of providing tension in the pinch discharge to counteract the negative tension of the orthogonal magnetic field produced by the pinching current itself. Experimental equipment has been made to produce very high axial magnetic fields of 40,000 gauss so that correspondingly large pinch currents can be employed. An important matter to consider and to test experimentally is the influence of the axial magnetic field not trapped within the pinch discharge. Control of the magnitude and direction of this exterior magnetic field has been attempted and the influence of its magnitude and direction on stability has been studied. Results of experiments now underway will be reported. P/354.
Stability of a Linear Pinch.
SUYDAM
BERGEN
R.
(U.S.A.).
A variation
by I. B. and R. M. KULSRUD for hydromagnetic stability problems, has been applied to the study of a linear, axi-symmetric pinch. It is shown by physical reasoning that a certain class of modes is particularly likely to be unstable, and the class of modes thus singled out is then studied with the
BERNSTEIN,
E.
principle,
A.
FRIEMAN,
developed M.
D.
KRUSKAL