Controlled nuclear fusion has been the dream of many – a clean, seemingly-perpetual source of energy. However, starting the reaction requires an incredibly high temperature (the “ignition” temperature), and although we are already capable of doing this, a new “superlaser” outlined in the journal Nature Communications ups the stakes considerably. This new high-intensity laser is said to be capable of heating material to tens of millions of degrees within a million millionth of a second.
The process of thermonuclear fusion keeps stars burning. Using this method to produce power on our own planet has been the end goal for many physicists for decades; it would be a source of pollution-free power with a highly abundant fuel source. It would simultaneously solve the growing energy crisis and could eventually signal an end to humanity’s enormous contribution to dangerous climate change.
However, one enormous problem has to be overcome first: more energy needs to be gotten out of the process than is put in in the first place. This was achieved last year by the National Ignition Facility (NIF) in the United States, but only just – a vast amount of energy was still required to be invested at the start of the process.
Thermonuclear fusion occurs naturally within the cores of stars under extremely high temperatures – our own Sun, for example, has a core temperature of 15 million degrees Celsius (27 million degrees Fahrenheit). Atoms from lighter elements collide, with their nuclei fusing to form heavier elements; as they do so, energy is released. In order for this process to start, the atoms have to have to be initially “excited” enough in order to be able to effectively collide with each other.
Although there are some physical processes within the Sun that actually lower the ignition temperature required for fusion to begin, the temperature required is still phenomenally high. This new proposal, outlined by a team of theoretical physicists at Imperial College London, aims to somewhat circumvent this problem – their new laser can hypothetically heat materials as hot as the core of our Sun in only 20 quadrillionths of a second. This is a rate 100 times faster than currently seen in fusion experiments conducted by the NIF.
Image credit: The new ultrafast heating technique can cause temperatures to rise by up to 15 million degrees almost instantaneously. Michal Zduniak/Shutterstock
Most lasers target the electrons within a material, exciting them and causing the overall temperature to dramatically rise. This new high-intensity laser targets the ions – electrically excited particles – within the material, using electrostatic shocks to cause them to accelerate. Normally, laser-induced shockwaves simply knock ions out of the way, but this new technique would allow for the ions in certain materials to be knocked away at different speeds. This would cause them to impact each other, generating friction, and producing heat.
This heating technique would work best on a material with two ion types, such as a plastic. As Dr. Mark Sherlock from the Department of Physics at Imperial College London explained in a statement: “The two types of ions act like matches and a box; you need both. A bunch of matches will never light on their own -- you need the friction caused by striking them against the box.”
If this new advanced laser is developed and shown to be effective, it will be the fastest heating rate ever demonstrated in a laboratory; certainly, this will be a great boost to the nuclear fusion reactor industry.
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