Károly Osvay and Gerard Mourou in the MTA laboratory
Professor Gérard Mourou attended the seminar at ELI ALPS, where Károly Osvay reported on the results of the first five-year phase of research conducted in the National Laser Transmutation Laboratory. The event also provided a platform for the discussion of the perspectives for the next phase of the laser transmutation project with participants including former Minister for Innovation László Palkovics, Minister for Energy Csaba Lantos and Gábor Szabó, Managing Director of ELI ALPS.
Picture 1: from left to right: Minister for Energy Csaba Lantos, Gábor Szabó, managing Director of ELI ALPS, Nobel Prize-winning physicist Gérard Mourou, Picture 2: Gábor Szabó's welcome speech, Picture 3: László Palkovics's online speech
ON THE OCCASION OF THE EVENT, SÁNDOR PANEK INTERVIEWED FRENCH PHYSICIST GERARD MOUROU.
With Professor Toshiki Tajima you proposed a model for a laser-driven neutron source for the transmutation of nuclear waste. Are you satisfied with the results Károly Osvay has achieved so far in his neutron generation experiments?
Yes, absolutely, the project is going in a very good direction, and I am happy to be associated with it myself. The number of neutrons produced in the experiments conducted so far is promising, and no other research group has ever produced such a large number of neutrons by laser. The main goal now is to produce even more neutrons in an energy-efficient way.
What is the ultimate goal of the research project: the management of nuclear waste or the development of a clean nuclear power generation process?
Both. We need to find solutions to the issues around energy production, so we are looking for energy that is clean, cheap and abundant. I myself firmly believe in the future of nuclear energy, but this requires answers to the safety questions that arise. I have long been convinced that the solution lies in ultrashort, ultrahigh intensity laser pulses. Fission-based nuclear power production inevitably produces actinide isotopes that can radiate for hundreds of thousands of years. If they are transmuted by neutron irradiation, they decay into elements with a shorter radiation lifetime. I mentioned power generation, because the operation of sub-critical reactors, which are much safer than the current ones, requires a neutron source. However, neutron beams are currently produced in huge and very expensive linear accelerators and cyclotrons, in extremely costly procedures. We therefore proposed using ultrashort light pulses for neutron generation, and the experiments conducted by Károly Osvay's group have made welcome progress in this, and they have even greater hopes for the upcoming experiments.
During a visit to Szeged in 2018, you allegedly convinced former Innovation Minister László Palkovics to finance the first phase of the transmutation project. In light of the current results, do you propose financial support to the second phase of the project?
Oh, only he could tell whether it was really me who convinced him. Let's just say I had a positive impact on the case. The opportunity presented itself, as ELI ALPS already had world-class laser equipment in Hungary to produce the required ultrashort laser pulses, and the research institute and the University of Szeged had the necessary knowledge for the project. Of course, I do recommend, and now even more strongly urge, government support for the project based on the results. The future of energy production is a huge problem for mankind, and this goal is in line with the shared social responsibility of science and politics. I truly am glad that Hungarian policy-makers have embraced this project. By the way, Minister of Culture and Innovation János Csák will soon join us in a meeting with one of the great proponents of thorium use, former CERN head Carlo Rubbia, an Italian physicist who was awarded the Nobel Prize in Physics in 1984 for his role in the discovery of weakly interacting particles.
You also mentioned in your presentation at the Academy of Sciences that you are proposing thorium as a fissile material instead of uranium. Why exactly this element?
First, it is significantly more efficient than uranium. As an illustration, 8 billion kWh of power can be produced annually by burning 10 loaded trains, or 3 million tons of coal, but during this process one cubic kilometre of carbon dioxide is released into the air. The same amount of energy can be produced through the fission of 300 tons of uranium, while only one ton of thorium would be needed, and of course none of the nuclear energy sources emit carbon dioxide. Furthermore, the fission of thorium leaves much less nuclear waste than uranium, and last but not least, it is more abundant globally. Thorium reactors also need neutrons to operate, so their use fits in with the project's objectives.
How long do you think it will take to launch the first application?
I believe that the project related experiments, planned for late autumn this year, will help us see more clearly. It will become clear whether the experiment regime we have built up so far will produce more neutrons. The use of thorium is being researched by many groups around the world, but neutron irradiation by femtosecond laser pulses, investigated experimentally by Károly Osvay's research group, is a unique topic in the world. The big novelty is not the transmutation itself, but the fact that it is triggered by laser-generated neutrons.
You are known to the scientific community as a great visionary physicist, which is no exaggeration, as you were one of the few who proposed the construction of the ELI infrastructure. Are you satisfied with the results?
The result is impressive! It is a great experience to be in this beautiful and advanced research environment, especially as similar infrastructures have been built in the Czech Republic and Romania. I cannot deny that I am proud of it. Its success is demonstrated by the fact that American researchers want similar facilities and are coming to us in Europe to copy the ELI model and equipment. However, now I have to watch what I say, because there will be someone who will turn my words into reality!
In your speech at the Academy, you envisioned experimental research into a whole new area of physics using high-intensity laser facilities. You anticipate that at intensities in the order of 1025 to 1030 W/cm3 it will be possible to study "ultrarelativistic" optical phenomena, up to the materialization of light. Do you think experimental laser science in the next decades will go this way?
Yes, it was obvious to me from the moment I found out how high peak intensity laser pulses could be produced. Current simulations already show that it will be possible to move even higher up the intensity range. Ultrahigh-intensity lasers will be able to produce fields of even greater intensity, pressure and temperature, and it is already experimentally demonstrated that a whole range of high-energy radiations and particles can be obtained by laser. There will be no need to build huge accelerators to shed light on the unanswered questions of physics. Laser wakefield particle acceleration, which is also studied at ELI ALPS, or surface plasma-based radiation excitation, can now be used to investigate many of these issues in a laboratory setting. I believe that the phenomena that are likely to be studied will include the formation of particle pairs in vacuum. Perhaps this will be the ultimate research goal in the field of high-intensity lasers, which can be achieved in the field of quantum electrodynamics and perhaps quantum chromodynamics.
Does it presuppose the generation of laser pulses shorter than attoseconds?
Today's simulations already demonstrate the feasibility of high-energy coherent pulse generation in the zeptosecond range, namely in the X-ray region. This will open the way to the zettawatt and PeV regime, the next chapter in laser-matter interaction.
When you proposed CPA laser amplification, which won you and Donna Strickland the Nobel Prize in 2018, did it occur to you that one day you would be talking about such high intensities?
No, not at all, initially. I was simply curious about the maximum intensity of laser pulses that could be produced. But later we could see that above certain intensities the electric field strength could reach a critical value. As far as I can see, two major groups of application have emerged from the research of the past decades: the generation of extremely fast attosecond pulses and the observation of extremely fast atomic and subatomic events; for which my dear friends Ferenc Krausz and Anne d'Huillier, and Pierre Agostini, who is also close to me, were awarded this year's Nobel Prize. The other major field of application is the one that I myself have proposed, namely to achieve very high peak intensities with very short laser pulses. To achieve high energies, it was not necessary to build huge lasers; it was enough to shorten the duration of the pulses. In the same context, ultrashort pulses have also been shown to be capable of particle acceleration and radiation.
How would you encourage secondary school students to pursue a university degree in physics?
They should feel free to follow their intuition and curiosity! We're all different, I, for one, would not have liked to be given advice. I became a physicist because I was intrigued by the different phenomena. When the first laser was put into operation on 16 May 1960, I was still at secondary school. I knew nothing about lasers! But I was attracted to them, because I was eager to know how they could be produced. I never regretted my choice, not even for a minute. There is no single recipe for inventions. We simply have to remain passionately curious, stop counting the years and patiently keep searching.