The Extreme Light Infrastructure beamlines work
The ELI Beamlines Institute near Prague (Czech Republic) with an international team of more than 300 people is now operational.
"When the ELI project was started, we attempted to make everything at least ten times better than the state of the art," Pavel Bakule told me about the founders' intention when they planned the Extreme Light Infrastructure Institute in the Czech Republic ten years ago. This was a very ambitious plan, but now they are almost there.
For those who haven't yet heard about this initiative, the Extreme Light Infrastructure is a European project to establish new laser institutes, preferably in Eastern Europe. The actual idea was conceived by Gerard Mourou, who shared the 2018 Nobel prize with Donna Strickland for achievements in the field of ultrastrong laser science. In an early interview he was already very clear about the program for ELI: "ELI aspires to be the most intense laser in the world," he said.
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With €820 million initial funding, three sites were chosen and separate institutes built in the Czech Republic (ELI BL Beamlines in Dolní Břežany near Prague), Hungary (ELI ALPS Attosecond Light Pulse Source in Szeged), and Romania (ELI NP Nuclear Physics in Magurele near Bucharest). In an early overview Mourou said that Hungary will focus on attosecond physics, the Czech lab on beams of radiation produced by intense laser-matter interactions and laser acceleration, and the Romanian lab on nuclear interactions.
The status quo at ELI BL
The buildings for ELI Beamlines in the village of Dolní Břežany were officially inaugurated in 2015. I attended that ceremony and I was impressed to see huge – and mostly empty – halls afterwards. In May 2019 I had a chance to revisit the institute and found that now the halls are filled with the most sophisticated laser technology I have ever seen, as well as a highly motivated staff.
"Building up something new from scratch is an amazing job," Georg Korn, the scientific director at ELI BL, told me. "Our goals are ambitious, but we are on track." This means that all four major laser systems are in house with continuous upgrades in progress to reach their nominal output.
It should be mentioned that the ELI organizers came up with a clever plan to get the most advanced laser systems in a rather short time: Most of the laser systems were developed at leading research institutions such as Lawrence Livermore National Laboratory (USA), or the Rutherford Appleton Laboratory (UK). At DESY in Hamburg, Germany, the joint teams developed a laser undulator beamline (LUX), which may lead to a laser-driven free-electron laser (FEL) in the future. A close collaboration between the various teams ensured an effective knowhow transfer during the development phase; this collaboration persists today.
The figure below shows a scheme of the laser systems L1 (ALLEGRA 1 kHz), L2 (AMOS), L3 (HAPLS 1 PW), and L4 (ATON 10 PW) along with their design parameters. All laser systems are located on the ground floor, whereas experimental stations are erected right underneath in a well-protected underground hall. The four major laser systems of ELI Beamlines each have different coupling options.
As for available systems and parameters, Pavel Bakule, leader for the L1 team laser, gave me some numbers on the systems as they are available now. Accordingly, the 10 PW (1015 W) system L4 showed energies of more than 1000 J in nanosecond pulses in December 2018. This system is planned to be upgraded to 1500 J and 150 fs by December 2020. This implies the full functionality of the compressor chamber, which is a vacuum chamber of 18 m length and 4.2 m height -- the size of a locomotive.
L3, the HAPLS system made at LLNL, has already demonstrated 28 fs pulses with 12 J energy in Summer 2018. By the end of 2019, it will be running with 30 J at 3 shots per second. This laser system will be gradually ramped up to its full design parameters of 30 J and 1 PW peak power at 10 Hz repetition rate.
L2 is a development system where several stages are tested; full operation at the design specifications is planned for 2021.
L1, the ALLEGRA system, is already available for experiments. Since March 2019, the system has been delivering 30 mJ in 14 fs pulses at 1 kHz. It has a contrast of at least 1:1011, which is very important for experiments. Further upgrades to 50 mJ (Dec 2019) and 100 mJ (Dec 2020) are scheduled.
Below the laser hall, with a total length of more than 100 m, is the experimental hall. ELI BL is designed for a wide range of experiments, in particular those using the laser as a secondary source of x-rays, electron beams, or proton bunches. Daniele Margarone, head of the ELIMAIA program, showed me the setup for proton acceleration. Using light from the L3 source (10 Hz) they want to convert PW (1015 W) laser pulses into a focused beam of high-energy proton bunches. After the laser target chamber, several magnet stages akin to those used in particle accelerators are used to clean the proton beam to less than 1° divergence. While the laser experts are still optimizing the parameters, this will be highly interesting for a range of applications in medicine, biology, and material science.
For all applications, an additional 100 m hall, which is grouped into six research projects, is rapidly filling up.
Although built under the auspices of the ELI Delivery Consortium, the whole structure will become part of the European Research Infrastructure Consortium (ERIC). ELI is designed as a user facility where external partners can apply for beam time. Cooperative agreements with other European and international research institutions have been signed, and the exchange is already vibrant.
A zero call for beam-time application is out now: The ELI Beamlines Facility invites the scientific community to submit proposals for the commissioning of instrumentation and early experiments in the E1 Experimental Hall for Applications in Molecular, Biomedical, and Materials Sciences. User-assisted commissioning and early experiments will take place between February and August 2019. Further calls will be added as available.
In 2003, Gerard Mourou and his team achieved a record laser intensity of 2x1022 W/cm2; now, ELI is set to go beyond. Creating and measuring intensities beyond 1022 W/cm2 is an enormous challenge, but it looks as if it is just a matter of time that ELI will get there. If higher intensities are reached, a new area of physics will be opened up where laser light interacts with vacuum oscillations -- or, in other words, with particles out of nowhere. That is thrilling.
Details of current and future projects will be discussed at the third International Conference on Extreme Light (ICEL). After recent meetings in Bucharest, Romania (2015), and Szeged, Hungary (2017), ELI Beamlines will host ICEL 2019 in the Czech Republic from 21 to 25 October 2019.
Trouble in paradise
While ELI Beamlines is moving ahead full steam, several unsolved problems exist at the other institutes, as a recent news feature in Nature revealed.1 The Romanian scientists have completed their laser system; however, a conflict with the Italian partner prevents the completion of a major detector. Moderation attempts have failed and the case is now the subject of a legal dispute.
In Hungary, a dispute over relations with two other research projects have escalated. According to the Nature report, three German and Hungarian scientists resigned from the International Science Advisory Committee of the ELI-ALPS in March. The remaining question is: Will this delay the work of the multinational user consortium ERIC?
As Georg Korn from ELI Beamlines confirmed, the Czech and the Hungarian partners, as well as the nonhost countries Germany, Italy, France, and the UK, within the ELI Delivery Consortium aim to first establish the ERIC organization relying on ELI Beamlines and ELI ALPS, with the expectation that ELI NP will join later. "The application submission is expected during this summer with the effective establishment of ELI ERIC in the second half of 2019," Korn said.
1. Alison Abbott, Nature 569, 607-608 (2019); doi: 10.1038/d41586-019-01607-7.