Lasers could Heat materials to Temps hotter than the Center of the Sun in only 20 quadrillionths of a second
Theoretical physicists from Imperial College London have devised an extremely rapid heating mechanism that they believe could heat certain materials to degrees in much less than a million millionth of a second. The method could be relevant to thermonuclear fusion energy, where scientists are seeking to replicate the Sun’s ability to produce clean energy.
The heating would be ~100X faster than rates currently seen in fusion experiments using the world’s most energetic laser system at the Lawrence Livermore National Laboratory, CA. Researchers have been using high-power lasers to heat material as part of the effort to create fusion energy for many years. In this new study, the physicists at Imperial were looking for ways to directly heat up ions – particles which make up the bulk of matter.
When lasers are used to heat most materials, the energy from the laser first heats up the electrons in the target. These in turn heat up the ions, making the process slower than targeting the ions directly. The Imperial team discovered that when a high-intensity laser is fired at a certain type of material, it will create an electrostatic shockwave that can heat ions directly.
“It’s a completely unexpected result. One of the problems with fusion research has been getting the energy from the laser in the right place at the right time. This method puts energy straight into the ions,” said Dr Arthur Turrell.
Normally, laser-induced electrostatic shockwaves push ions ahead of them, causing them to accelerate away from the shockwave but not heat up. However, using sophisticated supercomputer modelling, the team discovered that if a material contains special combinations of ions, they will be accelerated by the shockwave at different speeds. This causes friction, which in turn causes them to rapidly heat. They found that the effect would be strongest in solids with 2 ion types, such as plastics.
The heating is so fast in part because the material targeted is so dense. The ions are squeezed together to almost 10X the usual density of a solid material as the electrostatic shockwave passes, causing the frictional effect to be much stronger than it would be in a less-dense material, such as a gas.
The technique, if proven experimentally, could be the fastest heating rate ever demonstrated in a lab for a significant number of particles.
“Faster temperature changes happen when atoms smash together in accelerators like the Large Hadron Collider, but these collisions are between single pairs of particles,” said Dr Turrell. “In contrast the proposed technique could be explored at many laser facilities around the world, and would heat material at solid density.” http://www3.imperial.ac.uk/newsandeventspggrp/imperialcollege/newssummary/news_13-11-2015-10-11-57
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