THE HARD-CORE PINCH. PART I

Technical Report · Fri Jul 31 04:00:00 EDT 1959

DOI:https://doi.org/10.2172/4207377· OSTI ID:4207377

Birdsall, D H; Colgate, S A; Furth, H P

It is well known that a pinch column with internal H/sub Z/ and external conducting shell can be made grossly stable, but that small-scale instabilities persist; especiaily in the tubular region of maximum current density. To investigate further these small-scale instabilities of the stabilized pinch,'' we are using 12-in.-i.d. linear pinch tube with a 3-in.-o.d. insulated center rod. By controlling a current along this rod, as well as a current along external conducting straps, and a third current in an external H/sub z/ coil, it is possible to create many grossly stable pinch configurations. The small-scale stability of the tubular region of maximum current density can thus be studied for a wide range of internal and external magnetic field vectors. The magnetic field distribution in each discharge is obtained by a string of 10 magnetic pick- up loops. The distribution of plasma density is determined by modulating the inner or outer wall current and measuring the radial velocity of the resultant compressional Alfven waves. In one experiment, an initial H/sub z/ is entrapped in plasma by preionization, and then pushed radially outward from the rod by a rising H/sub theta /. The resultant field distribution, in which H/sub theta / everywhere falls more rapidly than 1/r, should have absolute hydromagnetic stability. The persistence of small-scale instabilities, as observed by the magnetic probes, in this inverse stabilized pinch'' suggests that the basic trouble is nonhydromagnetic. It is also found that, when the magnetic field approximates a vacuum field distribution, perfectly smooth and reproducible probe signals can be obtained. The absolute plasma current densities at which nearvacuum field distributions have been found stable are larger than current densities at which the 'stabilized pinch'' and inverse stabilized pinch'' distributions have been found unstable. (auth)

• Research Organization: California. Univ., Livermore. Lawrence Radiation Lab.
• DOE Contract Number: W-7405-ENG-48
• NSA Number: NSA-13-020012
• OSTI ID: 4207377
• Report Number(s): UCRL-5599
• Country of Publication: United States
• Language: English

Related Subjects

COILS
CONFIGURATION
CONTROL
CONTROLLED THERMONUCLEAR PROCESSES
CURRENTS
DENSITY
DISTRIBUTION
ELECTRIC CONDUCTIVITY
ELECTRIC DISCHARGES
HARD CORE PINCH
HYDROMAGNETIC WAVES
INDUCTION
IONIZATION
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MEASURED VALUES
MODULATION
OSCILLATIONS
PINCH
PLASMA
PROBES
RODS
SHELLS
SIGNALS
STABILITY
TUBES
VELOCITY