Phase- and Wall-Locked Modes Found in a Large Reversed-Field Pinch Machine, TPE-RX

Yagi, Y.; Koguchi, Haruhisa; Nilsson, J.; Bolzonella, T.; Zanca, P.; Sekine, S.; Osakabe, Toru; Sakakita, Hajime

doi:10.1143/jjap.38.l780

Cited by 8 publications

(5 citation statements)

References 13 publications

(7 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[15][16][17]23 In MST, the dynamo modes, which are responsible for generating the reversed magnetic field, continually exhibit a sawtooth behavior as a function of time 2 as shown in Fig. 1.…”

Section: A Previous Workmentioning

confidence: 99%

“…21 Phase-locked modes were almost always observed to lock to the wall in close proximity to the poloidal gap. ͑Reversed-field pinch devices have a characteristic set of insulating intersecting gaps cutting the vacuum chamber in the toroidal and poloidal directions.͒ In another RFP experiment TPE-RX, 16 it has been suggested that the locking phenomenon may be due 16 to the braking effect of eddy currents induced in the vacuum vessel by the growing, phase-locked modes. In addition, it was also proposed that locking is enhanced by the presence of a ''halo'' current, which is the current that flows through the plasma ''scrape-off'' layer into the vacuum chamber at the locking location.…”

Section: B the Slinky Modementioning

confidence: 99%

See 1 more Smart Citation

The sine-Gordon equation in reversed-field pinch experiments

et al. 2004

View full text Add to dashboard Cite

The focal point of this paper is a nonlinear model which describes localized magnetohydrodynamic modes in reversed-field pinch experiments. To date, nearly all experimental and theoretical work in this area have relied on the use of Fourier decomposition of spatial variations as a function of time. Moreover, due to the complexity of this nonlinear problem, previous work is restricted to the analysis of a relatively small number of modes. In contrast, the model studied in this paper, based on the sine-Gordon equation, addresses the full nonlinearity, does not rely on Fourier decomposition and does not require the range of the nonlinearity to be small. A specific consequence of working with the full nonlinearity is the existence of solitary waves in dispersive media. These solitary waves, a key part of the model, are used to describe the so-called slinky-mode propagating in the plasma. To this end, a remarkable resemblance is seen between the wave forms obtained from experiments and the mathematical predictions of the model.

show abstract

Section: A Previous Workmentioning

confidence: 99%

Section: B the Slinky Modementioning

confidence: 99%

The sine-Gordon equation in reversed-field pinch experiments

et al. 2004

View full text Add to dashboard Cite

show abstract

“…In MST, another large RFP machine, the mode is locked to the wall only when the induced field error exceeds a certain percentage of the poloidal magnetic field at the plasma surface [8]. A locked mode phenomenon quite similar to RFX is observed in TPE-RX [9,10]. The toroidal distribution of the radial magnetic fluctuation shows a toroidally localized bumpy structure locked at the same place throughout the discharge.…”

Section: Introductionmentioning

confidence: 95%

“…Locked mode phenomena have been studied in many RFP machines, but the detailed mechanism for the locked mode is not yet well understood [7][8][9][10]. It is speculated that the locked mode influences the global confinement properties by interacting with the first wall.…”

Section: Introductionmentioning

confidence: 99%

Field error and its effect on the plasma performance in TPE-RX, reversed-field pinch device

Koguchi¹,

Yagi²,

Hirano³

et al. 1999

Plasma Phys. Control. Fusion

Self Cite

View full text Add to dashboard Cite

The effects of field errors at the poloidal gap of the thick shell on the plasma performance and the wall-locking are intensively studied. The coil system of TPE-RX (major/minor radii, R/a = 1.72/0.45 m) has several features for cancelling the field errors at the thick shell gap and for controlling the equilibrium position of the plasma column. It is confirmed that these field error cancellation schemes work well for the normal operating conditions in TPE-RX. It is shown quantitatively that the global performance of the revised-field pinch operation is affected if the shell gap field error exceeds about 5% of the poloidal magnetic field. As expected, the probability of the mode to lock at the shell gap increases as the field error increases.

show abstract

“…In the TPE-RX experiment [9], it was found under certain experimental conditions that the probability of locking decreased by 25% by lowering the plasma current I P , decreasing the plasma current rise time, and decreasing the filling pressure of the deuterium gas.…”

Section: Introductionmentioning

confidence: 99%

Utilization of Logistical Regression to the Modified Sine-Gordon Model in the MST Experiment

Alkhateeb,

Ebraheem,

Al-Otaibi

2024

OJMSi

View full text Add to dashboard Cite

In this paper, a logistical regression statistical analysis (LR) is presented for a set of variables used in experimental measurements in reversed field pinch (RFP) machines, commonly known as "slinky mode" (SM), observed to travel around the torus in Madison Symmetric Torus (MST). The LR analysis is used to utilize the modified Sine-Gordon dynamic equation model to predict with high confidence whether the slinky mode will lock or not lock when compared to the experimentally measured motion of the slinky mode. It is observed that under certain conditions, the slinky mode "locks" at or near the intersection of poloidal and/or toroidal gaps in MST. However, locked mode cease to travel around the torus; while unlocked mode keeps traveling without a change in the energy, making it hard to determine an exact set of conditions to predict locking/unlocking behaviour. The significant key model parameters determined by LR analysis are shown to improve the Sine-Gordon model's ability to determine the locking/unlocking of magnetohydrodyamic (MHD) modes. The LR analysis of measured variables provides high confidence in anticipating locking versus unlocking of slinky mode proven by relational comparisons between simulations and the experimentally measured motion of the slinky mode in MST.

show abstract

Phase- and Wall-Locked Modes Found in a Large Reversed-Field Pinch Machine, TPE-RX

Cited by 8 publications

References 13 publications

The sine-Gordon equation in reversed-field pinch experiments

The sine-Gordon equation in reversed-field pinch experiments

Field error and its effect on the plasma performance in TPE-RX, reversed-field pinch device

Utilization of Logistical Regression to the Modified Sine-Gordon Model in the MST Experiment

Contact Info

Product

Resources

About