PPPL-3791 is available in <a href="PPPL-3791.pdf">pdf</a> format (1.7 MB).

<p>
<b>High-beta, Long Pulse, Bootstrap Sustained Scenarios on the National Spherical Torus Experiment (NSTX)</b>
</p>

<p>
<b>Authors:</b> D.A. Gates for the NSTX National Research Team
</p>

<p>
<b>Date of PPPL Report:</b> February 2003
</p>

<p>
<b>Published in:</b> Phys. Plasmas <b>10</b> (May 2003) 1659-1664.</p>


<p>

Long-pulse, high-beta scenarios have been established on the National Spherical Torus Experiment (NSTX). 
<font face ="symbol"> b</font><sub>t</sub>(<u>=</u>2<font face ="symbol">m</font><sub>0</sub>&#60;P&#62;/B<SUP>2</SUP><SUB>t0</SUB> ~ 35&#37; 

has been achieved during transient discharges. The machine improvements that lead to these results, including error field reduction and high-temperature bakeout of plasma-facing components, are described. The highest 

<font face ="symbol"> b</font><sub>t</sub> 

plasmas have high triangularity (<font face ="symbol">d </font> = 0.8) and elongation (<font face ="symbol">k </font>= 2.0) at low-aspect ratio A <u>=</u> R/a = 1.4. The strong shaping permits large values of normalized current, I<sub>N</sub>(<u>=</u> I<sub>p</sub>/(aB<sub>t0</sub>) <font face ="symbol"></font> approximately, approximately equal to 6 while maintaining moderate values of q<sub>95 </sub> = 4. Long-pulse discharges up to 1 sec in duration have been achieved with substantial bootstrap current. The total noninductive current drive can be as high as 60%, comprised of 50% bootstrap current and ~10% neutral-beam current drive. The confinement enhancement factor H<sub>89P</sub> is in excess of 2.7. <font face ="symbol">b</font><sub>N</sub> &#42; H<sub>89P</sub> approximately greater than 15 has been maintained for 8 &#42;  <font face ="symbol"> t<sub>E</sub> </font> ~ 1.6  &#42;  <font face ="symbol"> t</font><sub>CR</sub>, where <font face ="symbol"> t</font><sub>CR</sub> is the relaxation time of the first radial moment of the toroidal current density. The ion temperature for these plasmas is significantly higher than that predicted by neoclassical theory.




</p>