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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Bootstrap current</span></span>
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<div id="mw-content-text" class="mw-body-content mw-content-ltr" lang="en" dir="ltr"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><p>In a toroidal <a href="Fusion_power" title="Fusion power">fusion power</a> device, a <a href="Plasma_(physics)" title="Plasma (physics)">plasma</a> is confined within a donut-shaped cylinder. If the gas pressure of the plasma varies across the radius of the cylinder, a self-generated current will spontaneously arise within the plasma, due to <a href="Collisions" class="mw-redirect" title="Collisions">collisions</a> between trapped particles and passing particles. This current is called the <b>bootstrap current</b>, and is commonly found in <a href="Tokamak" title="Tokamak">tokamak</a> fusion devices. The tokamak uses a combination of external magnets and a current driven in the plasma to create a stable confinement system. One goal of advanced tokamak designs is to maximize the bootstrap current, and thereby reduce or eliminate the need for an external current driver. This could dramatically reduce the cost and complexity of the device.
</p><p>From a kinetic point of view, the <b>bootstrap current</b> is the effect of trapped particles (which practically lie on <a href="Poloidal" class="mw-redirect" title="Poloidal">poloidal</a> plane) and density gradient: the poloidal current due to trapped particles motion is unbalanced since the density is not constant, therefore the bootstrap current is needed to "close the circuit".
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<div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2></div>
<ul><li><a href="Persistent_current" title="Persistent current">Persistent current</a></li></ul>
<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
<ul><li><a rel="nofollow" class="external text" href="https://fusion.gat.com/images/3/3a/PolitzerAPS04.pdf">"Self Generated “Bootstrap” Current Contains Magnetic Fusion Plasma"</a><a rel="nofollow" class="external text" href="https://web.archive.org/web/20160303224504/http://fusion.gat.com/images/3/3a/PolitzerAPS04.pdf">"Archive"</a>, General Atomics</li>
<li><a rel="nofollow" class="external text" href="http://www.ees.nagoya-u.ac.jp/~web_dai5/english/B.html">"Plasma Dictionary"</a><a rel="nofollow" class="external text" href="https://web.archive.org/web/20181003220902/http://www.ees.nagoya-u.ac.jp/~web_dai5/english/B.html">"Archive"</a>, Nagoya University</li></ul>
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