Construction and Initial Operation of the Columbia Nonneutral Torus

Pedersen, T. S.; Kremer, Jason P.; Lefrançois, Rémi; Marksteiner, Quinn R.; Pomphrey, N.; Reiersen, W.; Dahlgren, F.; Sarasola, Xabier

doi:10.13182/fst06-a1258

Cited by 27 publications

(29 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1. Details of the CNT design and construction can be found in References [1,2]. CNT was assembled rather easily primarily by graduate students, an advantage of the error field resilience in the design.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Electron-Rich Plasmas in the CNT Stellarator

Pedersen

Berkery

Boozer

et al. 2008

Plasma and Fusion Research

View full text Add to dashboard Cite

Pure electron plasmas and electron plasmas with a finite ion fraction have been studied in the Columbia Nonneutral Torus (CNT) since the end of 2004. Results from the first three years of operation are summarized. Stable, small Debye length pure electron plasmas are routinely created, and have confinement times up to 20 msec. The confinement is limited by radial transport caused by internal rods, as well as electron-neutral collisions. The neutral driven transport rate is indicative of poor particle orbits in CNT, despite the strong radial electric field. Numerical simulations shed light on this issue, demonstrating the detrimental effects of variations in the electrostatic potential on a magnetic surface. With the installation of a magnetic surface conforming electrostatic boundary and the transition to external diagnostics, significantly longer confinement times should be possible. Also presented are observations of sudden confinement jumps that have a hysteretic behavior, and observations of an ion driven instability.

show abstract

Section: Introductionmentioning

confidence: 99%

Dynamics of Electron-Rich Plasmas in the CNT Stellarator

Pedersen

Berkery

Boozer

et al. 2008

Plasma and Fusion Research

View full text Add to dashboard Cite

show abstract

“…Magnetic surfaces are created by two pairs of circular planar copper coils. Although the magnetic field configuration of CNT is not optimized to eliminate trapped particle losses, high-quality magnetic surfaces have been measured experimentally [11] and the long confinement times measured have confirmed the existence of macroscopically stable equilibria of electron plasmas in CNT [1]. A segmented conducting boundary conforming to the shape of the plasma has been recently installed in order to impose the electrostatic potential at the plasma edge.…”

Section: Introductionmentioning

confidence: 99%

“…A φ plasma = −200 V pure electron plasma is characterized by T e between 2 and 7 eV and n e ≈ 3 · 10 12 m −3 . A more complete description of the CNT stellarator can be found in [11,[13][14][15]. Partially neutralized plasmas have not been studied theoretically or experimentally in detail, and there are few predictions as to how the plasma will evolve from single-component to quasineutrality.…”

Section: Introductionmentioning

confidence: 99%

First Observations of Partially Neutralized and Quasineutral Plasmas in the Columbia Non‐Neutral Torus

Sarasola

Pedersen

Brenner

et al. 2010

Contrib. Plasma Phys.

View full text Add to dashboard Cite

The Columbia Non-neutral Torus (CNT) is a stellarator designed to study pure electron, partially neutralized and positron-electron plasmas. CNT usually operates with electron rich plasmas (with negligible ion density) [1]. The accumulation of ions alters the equilibrium of electron plasmas in CNT and a global instability has been observed when the ion fraction exceeds 10%. A characterization of this instability is presented in [2], analyzing its parameter dependence and spatial structure (non-resonant with rational surfaces). A segmented conducting mesh has been installed to impose the electrostatic boundary condition at the plasma edge. Results after the installation of the conducting boundary confirm the presence of an instability in electron rich plasmas with a finite ion content. A new set of experiments is currently underway studying plasmas of arbitrary degree of neutralization, ranging from pure electron to quasineutral plasmas. Basic observations show that the plasma potential decouples from the emitter bias when we increase the degree of neutralization of our plasmas. Partially neutralized plasmas are also characterized by multiple mode behavior with dominant frequencies between 20 and 200 kHz. When the plasma becomes quasineutral, it reverts to single mode behavior (2 -18 kHz). The first results on partially neutralized and quasineutral plasmas in CNT are reported on here.

show abstract

“…Section 3 shows an example where the method is used to follow the trajectory of a weakly magnetized ion in the complicated geometry of the Columbia Non-neutral Torus (CNT) [21,19].…”

Section: Introductionmentioning

confidence: 99%

The use of tricubic interpolation with spectral derivatives to integrate particle trajectories in complicated electromagnetic fields

Marksteiner

2010

Journal of Computational Physics

View full text Add to dashboard Cite

Construction and Initial Operation of the Columbia Nonneutral Torus

Cited by 27 publications

References 13 publications

Dynamics of Electron-Rich Plasmas in the CNT Stellarator

Dynamics of Electron-Rich Plasmas in the CNT Stellarator

First Observations of Partially Neutralized and Quasineutral Plasmas in the Columbia Non‐Neutral Torus

The use of tricubic interpolation with spectral derivatives to integrate particle trajectories in complicated electromagnetic fields

Contact Info

Product

Resources

About