PPPL-4777


<p>
<b> Stochastic Orbit Loss of Neutral Beam Ions From NSTX Due to Toroidal Alfven Eigenmode Avalanches   </b>
</p>

<p>
<b>Authors:</b>  
</p> D.S. Darrow, N. Crocker, E.D. Fredrickson, N.N. Gorelenkov, M. Gorelenkova, S. Kubota, S.S. Medley, M. Podestà, L Shi, and R.B. White

<p><b>Abstract:</b> 
<br>  Short toroidal Alfven eigenmode (TAE) avalanche bursts in the National Spherical
Torus Experiment (NSTX) cause a drop in the neutron rate and sometimes a loss of neutral
beam ions at or near the full injection energy over an extended range of pitch angles. The
simultaneous loss of wide ranges of pitch angle suggests stochastic transport of the beam ions
occurs. When beam ion orbits are followed with a guiding center code that incorporates
plasma's magnetic equilibrium plus the measured modes, the predicted ranges of lost pitch
angle are similar to those seen in the experiment, with distinct populations of trapped and
passing orbits lost. These correspond to domains where the stochasticity extends in the orbit
phase space from the region of beam ion deposition to the loss boundary.   
<br>

__________________________________________________
<br><br>
2013 <em>Nucl. Fusion</em> <strong>53</strong> 013009 <strong><a href="http://dx.doi.org/10.1088/0029-5515/53/1/013009">doi:10.1088/0029-5515/53/1/013009</a></strong><br>
<br>
__________________________________________________
<br><br>
<a href="PPPL-4777.pdf"><b>Download PPPL-4777</b></a> (pdf 275 KB 10 pp)
<br>
__________________________________________________

</p>