Charge-exchange measurements of MHD activity during neutral beam injection in the Princeton Large Torus and the Poloidal Divertor Experiment

Abstract

The horizontally scanning, multiangle charge-exchange analyzers on the Princeton Large Torus (PLT) and the Poloidal Divertor Experiment

Charge-exchange measurements of beam ion thermalization in MHD-quiescent plasmas in the poloidal divertor experiment

“…4, a significant exception occurs at the highest current and beam powers due to the onset of the fishbone instability. Such effects will be discussed in a companion publication [20], and the 400-kA, 12-kG plasma confinement times are not plotted in Fig. 6b, since fast ion losses due to fishbones [11] were not accounted for in the present work.…”

“…Once again, the simplest explanation is that the neutral density doubles during this time, perhaps because of the recycling of plasma particles lost through an instability. This topic will be treated in more detail in a subsequent publication [20].…”

Loss of beam ions to the inside of the PDX tokamak during a fishbone instability

“…Conceivably, variations in neutral density may account for the bursts on the IDE in the high mode, but in the low mode the charge exchange bursts are almost certainly due to an increase in the number of fast ions in the IDE sightline. Because of the relatively gradual decay of the MHD bursts (about 1 ms) the possibility that sawteeth were coincident with the fishbones can be excluded [4,8] and therefore the bursts are not due to the transport of fast ions when sawteeth occurred [9]. Since the IDE sightline skims the inner radius of the plasma, these bursts indicate that fishbones transport beam ions inwards in major radius as well as outwards.…”

Contemporary Instrumentation and Application of Charge Exchange Neutral Particle Diagnostics in Magnetic Fusion Experiments

“…Passive charge exchange measurements were obtained on PDX to investigate "fishbones" [30] as shown in Fig. 2 [31]. The upper panel shows FIDE charge-exchange spectra from PDX device for a no-fishbone discharge (2 beams) compared with a severe-fishbone discharge (4 beams).…”

“…Note that these spectra were obtained by sweeping the energy analyzer in time, so that fishbone spikes appear to be localized in energy but in fact they are localized in time. The lower panel shows simulations of the spectra using a bounce-averaged Fokker-Planck code [31]. ms -1 ).…”