1.2 megavolt <a href="https://en.wikipedia.org/wiki/Cockcroft-Walton_generator" class="extiw" title="w:Cockcroft-Walton generator">Cockcroft-Walton particle accelerator</a> <i>(background)</i> at the <a href="https://en.wikipedia.org/wiki/Clarendon_Laboratory" class="extiw" title="w:Clarendon Laboratory">Clarendon Laboratory</a>, Oxford University, UK in 1948.  It consists of a 6 stage voltage multiplier stack with a large globe to store charge at the top.   The black segments of each column contain <a href="https://en.wikipedia.org/wiki/capacitor" class="extiw" title="w:capacitor">capacitors</a> to store the charge, while the diagonal "crossrungs" contain high voltage <a href="https://en.wikipedia.org/wiki/vacuum_tube" class="extiw" title="w:vacuum tube">vacuum tube</a> rectifiers called <a href="https://en.wikipedia.org/wiki/kenotron" class="extiw" title="w:kenotron">kenotrons</a>, which only conduct current in one direction.  An alternating voltage of several hundred kilovolts is applied between the bottom columns.  The columns function as a <a href="https://en.wikipedia.org/wiki/charge_pump" class="extiw" title="w:charge pump">charge pump</a>, pumping electric charge up the columns until the top terminal is at a potential of 1.2 million volts.  The voltage is applied to opposite ends of an evacuated accelerator tube <i>(not shown)</i> which accelerates charged <a href="https://en.wikipedia.org/wiki/subatomic_particle" class="extiw" title="w:subatomic particle">subatomic particles</a> traveling through it to high speeds.  All the metal parts of the machine must be covered by smooth curved metal "corona rings" to prevent <a href="https://en.wikipedia.org/wiki/corona_discharge" class="extiw" title="w:corona discharge">corona discharge</a>, which can cause charge to leak into the air.   The Cockcroft-Walton accelerator was invented by British physicists <a href="https://en.wikipedia.org/wiki/John_Douglas_Cockcroft" class="extiw" title="w:John Douglas Cockcroft">John Douglas Cockcroft</a> and <a href="https://en.wikipedia.org/wiki/Ernest_Thomas_Sinton_Walton" class="extiw" title="w:Ernest Thomas Sinton Walton">Ernest Thomas Sinton Walton</a> in 1932.
Unknown author<span style="display: none;">Unknown author</span>
Retrieved April 13, 2015 from <a rel="nofollow" class="external text" href="https://books.google.com/books?id=fiYDAAAAMBAJ&amp;pg=PA113">"Britain gets atom smasher" in <i>Popular Science monthly</i>, Popular Science Publishing Co., New York, Vol. 153, No. 5, November 1948, p. 113</a> on Google Books