Plasma based compact ion sources

Cancer treatment, materials science and energy research are a few areas where energetic ions can be used. Today, the ions must be accelerated in large and expensive facilities, but Swedish researchers are trying to develop a smaller and less expensive method. Lasers are part of the solution. If something is radiated with ions, they have a unique property compared to x-ray radiation or electrons, for example. They release almost all of their energy where they stop, instead of gradually, or at the surface where they penetrate. This means that a very good precision can be achieved, as needed in e.g. cancer treatments. Deeply located tumors can be irradiated without the surrounding tissue being damaged. The technique has been used for several decades, but it has a disadvantage: to produce ions with adequate energy, very large facilities are needed. They are expensive, and patient treatment is presently limited to only a few dedicated facilities in the world. One such facility is now being built in Uppsala, and it will be the first in the Nordic region. With strong electric fields, hydrogen ions, i.e. protons, will be accelerated there, over long distances to reach the energy required for the treatment. But there is another way to produce energetic ions. Around 15 years ago, researchers discovered that if a thin layer of a material, almost any material, is fired at with high power laser pulses, the material’s atoms are ionized: some of their electrons loosen and are thrown off. The material is converted into plasma, kind of like a gas consisting of charged particles. The electric voltage that arises between the electrons thrown off and the positive ions pulls the ions out of the material and gives them high energy. Researchers at Chalmers University of Technology, Umeå University and Lund University will investigate this process in detail in the next few years.