vacuum

<h1>Vacuum system of tokamak</h1>

<p>System of tokamak exhausting used to be divided into two independent sections. It was believed, that putting an extra <strong>vacuum layer</strong> between the <a href=“/Tokamak/Chamber/Liner/AAAindex”>liner</a> and outer environment would allow more stabilised plasma to be obtained. However, this theory proved to be wrong and after integrating the <a href=“../../Tokamak/Coils/Stabilization/coils_stabilisation”>feedback stabilisation system</a> into the tokamak in <a href=“?p=history”>1985</a>, the <strong>vacuum exhausting system</strong> of the <a href=“../../Tokamak/Chamber/Coating/AAAindex”>coating</a> has completelly been removed. Using of the <a href=“../../Tokamak/Coils/Stabilization/coils_stabilisation”>stabilisation coils</a> proved to be the correct decision for better plasma confinement.</p>

<p>Construction of above mentioned system was designed to reach the <strong>vacuum</strong> better than 10<sup>-6</sup> Torr in <a href=“/Tokamak/Chamber/Liner/AAAindex”>liner</a>. However, it is not possible yet to state the maximum reachable level of <strong>vacuum</strong> after the tokamak was moved to <a href=“http://www.cvut.cz/en?set_language=en”>CTU</a>, since further control measurements are needed. However, we have confirmed so far, that critical damage to <a href=“/Tokamak/Chamber/Liner/AAAindex”>liner</a> did not take place.</p>

<p>System for <a href=“/Tokamak/Chamber/Liner/AAAindex”>liner</a> <strong>exhaustion</strong> is made of heated components. This is because it is well known, that at higher energies of environment, the purging of remainder gasses an even solid particles take place. This helps obtaining better purity of the <a href=“/Tokamak/Chamber/Liner/AAAindex”>liner</a> volume. The switching of <a href=“?p=vacuum_turbo_molecular”>TMP turbomollecular pump</a> of the system is possible only after the opening of <a href=“?p=cooling”>water cooling system</a> of the <a href=“?p=vacuum_turbo_molecular”>turbomollecular pump</a> because of the automatic blocking. The whole <strong>exhausting system</strong> is electrically insulated from <a href=“../../Tokamak/Chamber/chamber”>tokamak chamber</a> by system of ceramical and teflon insulators. Besides, there is also an embedded tombak insulation as shock absorber.</p>

<h3>Liner exhaustion system</h3><p>To reach the <strong>vacuum</strong> of the level we need for our experiments, the <a href=“?p=vacuum_turbo_molecular”>special pumps</a> are needed to be used at exhaustion. However, these pumps do not work properly at higher pressures and thus there is needed to reach some low <strong>level of vacuum</strong> (forevacuum) before they can be switched on and to finish the exhaustion to the required level. The forevacuum better than 10<sup>-2</sup> Torr is to be generated by the <a href=“../../../Infrastructure/VacuumManagement/RotaryPump/RotayPump.MPG”>rotational air pump RV1</a> and via electromagnetic valve is sent into a single <a href=“?p=vacuum_turbo_molecular”>TMP turbomolecular pump</a>.This is blocked by electromagnetic valves B1 and B2. Seasoning valve N1 of rotational air pump RV1 is closed automatically by closing of the air pump. After the air pump is switched off, the N1 valve automatically opens.</i></a>

<p><a href=“?p=vacuum_turbo_molecular”>TMP Turbo molecular pump</a> is mounted to <a href=“/Tokamak/Chamber/Liner/AAAindex”>liner</a> via metallic heatable valve. <strong>Exhausting system</strong> is insulated from <a href=“/Tokamak/Chamber/Liner/AAAindex”>liner</a> by ceramical insulators I1 and I2. For direct foreexhausting of liner by <a href=“../../../Infrastructure/VacuumManagement/RotaryPump/RotayPump.MPG”>RV1 air pump</a> there are mounted biffurcastion with metallic valve K3 and freezer V5. To make the connection between <strong>forevacuum system</strong> and liner possible, mechanical connecting valve SV is integrated. <a href=“?p=vacuum_measurement”>Forevacuum measurement</a> is done by single <a href=“?p=vacuum_measure”>digital measure</a>, to measure high rating vacuum of the <a href=“?p=vacuum_turbo_molecular”>TMP turbo mollecular pump</a> there are used triodes M4 and M5 of the <a href=“?p=vacuum_measurement”>vacuum measurement system</a></p>

<h3>Ordinary exhausting process</h3>

<p>Exhausting system regulation takes place on <a href=“?p=construction”>control panel</a>, which used to be situated on vacuum stander no. 3. We are not exactly sure where it will be placed after we move all the components of the device to its new home on <a href=“http://www.cvut.cz”>CTU</a>. And of course, it cannot be stated the optimal exhaustion process of <a href=“../../Tokamak/BasicCharacteristics/AAAindex”>GOLEM tokamak</a> until more data are obtained. However, in <a href=“../../Introduction/History/GOLEM History”>CASTOR tokamak</a> used to take place the following process of <strong>vacuum exhaustion</strong>.</p>

<p>In case of last exhausting to be done less than one week ago, vacuum in <a href=“/Tokamak/Chamber/Liner/AAAindex”>liner</a> than 10<sup>-2</sup> Torr. So the following exhausting process may take place:

<ul>: <li>All the valves but the saturating rotator N1, are closed. <li>Switch on the engines of rotator for <a href=“../../../Infrastructure/VacuumManagement/RotaryPump/RotayPump.MPG”>RV1</a>, valve N1 is closed automatically during this process. <li>Open valve P1 (by electromagnetics). On <a href=“?p=vacuum_measurement”>M1 (or M2) and M3 gauges</a> monitor the reach of forevacuum at least 10<sup>-1</sup> Torr. <li>Open valves B1, B2 and B3 and after the forevacuum better than 10<sup>-1</sup> Torr is reached, open panel valve of coating VD as well. <li>Switch the heating of <a href=“?p=vacuum_turbo_molecular”>TMP turbomolecular pump</a>. This is possible only after the <a href=“?p=cooling”>water cooling system</a> of pumps is open. <li>After the vacuum of level at least 10<sup>-5</sup> Torr indicated by <a href=“?p=vacuum_measure”>M4, M5 and M6 gauges</a> (high vacuum measure) is reached, open metallic valves K1 and K2. Only one of appropriated valves K1 or K2 is opened. <li>Vacuum level in <a href=“/Tokamak/Chamber/Liner/AAAindex”>liner</a> is measured by gauge <a href=“?p=vacuum_measure”>M7</a>.

</ul>

When switching off takes place, the process is inverted. Valves B1, B2 and B3 are shut down after the <a href=“?p=vacuum_turbo_molecular”>TMP pump</a> is cooled down. E.g. about one hour after <a href=“?p=heating”>the heating system</a> had been shut.</p>

<h3>Current situation of the system</h3><p>Since the tokamak is finally placed into its cellar room, it is possible to start with the <strong>vacuum exhaustion system</strong> reanimation. The process has started by several control exhaustions by <a href=“../../../Infrastructure/VacuumManagement/RotaryPump/RotayPump.MPG”>a rotational pump</a>. These have been done since there was a worry about the possibility of <a href=“/Tokamak/Chamber/Liner/AAAindex”>liner</a> punctuation. <a href=“?p=vysledky???”>The measurements</a> have shown that there actually is a small hole in <a href=“/Tokamak/Chamber/Liner/AAAindex”>the liner</a>, however, its size is still in margins of expected damage during the transportation of the device to FNSPE. The appropriate <a href=“?p=vacuum_turbo_molecular”>turbo mollecular pump</a> is still to be chosen and ordered, so the reanimation is currently in state of reoperating the forevacuum exhaustion by rotational pump. This process is being led by doc. Ing. Zdenek Cespiro, Csc, the department vacuum expert.</p>

<p><a href=“?p=documentation”>Back to the documentation</a></p>

<h3>Gallery</h3>

<table>: <tr> <td><div align=“center”><a href=“P1010029.JPG” rel=“lightbox[img]”><img src=“P1010029.JPG” alt=“vacuum exhaustion” width=“200” height=“150” border=“0”/></a></div></td> <td><div align=“center”><a href=“P1010073.JPG” rel=“lightbox[img]”><img src=“P1010073.JPG” alt=“vacuum exhaustion” width=“200” height=“150” border=“0”/></a></div></td> <td><div align=“center”><a href=“P7310011.JPG” rel=“lightbox[img]”><img src=“P7310011.JPG” alt=“vacuum exhaustion” width=“200” height=“150” border=“0”/></a></div></td> </tr> <tr> <td><p> </p></td> </tr> <tr> <td><div align=“center”><a href=“files/documentation_gallery/vacuum/PA270001.JPG” rel=“lightbox[img]”><img src=“files/documentation_gallery/vacuum/thumbs/PA270001.JPG” alt=“vacuum exhaustion” width=“200” height=“150” border=“0”/></a></div></td> </tr>

</table>