Irvine Field Reversed Configuration Ion Density and Flow

Описание: TO USE OR PRINT this presentation click : http://videosliders.com/r/325

==============================================================
Irvine Field Reversed Configuration Ion Density and Flow T. Roche, F. Brandi, E. P. Garate, F. Giammanco, W. W. Heidbrink, W. Harris, R. McWilliams, E. Paganini, E. Trask Slides available at http://hal900.ps.uci.edu/aps2008/
,ABSTRACT: A mach probe has been used to measure the time-evolved, radial ion density profile and ion flow velocity in the Irvine Field Reversed Configuration (IFRC). The probe consisted of four tungsten tips 0.1mm in diameter and about 1.7mm long. An alumina barrier was placed between 2 of the tips to block ions impinging from opposite directions. The blocked tips were biased 30V negative with respect to the plasma floating potential to draw ion saturation current. The temperature of the ions was measured to be ~10eV using doppler broadening spectroscopy. Peak densities were measured to be ~1 x 1014 cm-3. Flow velocity was measured for the plasma source at 5 x 106 cm/s without the presence of magnetic fields. Data gathered during reversal were too noisy to measure the flow velocity of the FRC. These data were compared with two other methods for calculating the density. A Nd:YAG laser interferometer measured a line integrated density of 5 x 1015 cm-2 over an approximately 60 cm chord length. Previously gathered magnetic field data provided a radial density profile under the assumption of pressure balance. The combination of these two methods verifies both the shape and magnitude of the measured signals. An energy analyzer is being designed to measure the ion velocity distribution function in the IFRC.
,Irvine Field Reversed Configuration Plasma Guns
,Brief Description of the Irvine Field Reversed Configuration (IFRC) Coaxial Solenoid Configuration
Inner Solenoid (Flux Coil) r = 10.2 cm
Outer Solenoid (Flux Limiter) r = 38 cm Plasma Properties Cable gun source
Peak density ni = 1 x 1014 cm-3 Plasma Current = 10 kA Peak Field Reversal = ± 250 Gauss ,Formation Uses Inner Flux Coil plasma FRC with a Flux Coil configuration. The plasma forms around the inner coil instead of r=0. Pietrzyk, Vlases, Brooks, Hahn, Raman, Nuc. Fus. 1987
,Goals Measure the time-evolving density profile
Measure Ion Flow Velocity Determine Ion Energy Distribution Function Classify orbit types
Measure plasma drift ,Ion Saturation Current Measured With Floating Double Probe Stationary Plasma Drifting Plasma
,Simple Circuit and Probe 4.2mm 1.7mm 0.9mm 40.0cm The signal tips are biased ~35V negative with respect to the plasma floating potential.
Reference tips float to the floating potential. The current flowing between the tips is measured with two Pearson probes. ,Some of the Mach Probe Revisions Each Probe consists of 4 tips protruding from a 50cm shaft. Two of the tips are completely exposed to the plasma. The other two are separated from each other and only exposed to 180 degrees of theplasma. The probe on the bottom is the final version. The tips are much shorter, made out of tantalum instead of platinum and have a radius of 0.4mm. It is the only version that didn’t suffer from arcing.
,These shots exhibit functionality of the Mach Probe. Probe is located at z=-8cm with tips facing opposite arrays of plasma guns. Flux will be greater and arrive earlier on the tip closer to guns. In all cases larger signal is from expected tip. Here the plasma is not magnetized. This probe works as expected in these conditions. The Mach Probe Works
,Magnetic Field Evolves on 10ms Scale Null Bz at z = 0 cm quickly reverses and maintains reversal until it begins to decay around 70 micro-seconds. Br at r = 25 cm takes on the appropriate shape and decays as the driving flux coil dies. The field null, or B = 0, forms around -10 cm < z < 10 cm and r ~ 25 cm.
,Time evolution of density profile Ion saturation current reaches its maximum at r = 24 cm at 37 us.
The density peak is at the magnetic null. In this sequence the plasma reaches an equilibrium and then quickly decays. These data are an average over both tips wit