ELI

Extreme Light Infrastructure - Nuclear Physics facility (ELI-NP) will consist of two components:

- A very high intensity laser, where the beams from two 10 PW Apollon type lasers are coherently added to the high intensity of 10²³-10²⁴W/cm2 or electrical fields of 10¹⁵V/m.
- A very intense (10¹³γ/s), brilliant γ beam, 0.1 % bandwidth, with Eγ = 19 MeV, which is obtained by incoherent Compton back scattering of a laser light off a very brilliant, intense, classical electron beam (Ee = 600 MeV). The brilliant bunched electron beam will be produced by a warm linac using the X-band technology.

This infrastructure will create a new European laboratory with a broad range of science covering frontier fundamental physics, new nuclear physics and astrophysics as well as applications in nuclear materials, radioactive waste management, material science and life sciences. For the realization of ELI-NP we envisage the following two principles as guideline:
- a staged realization of ELI-NP
- a flexible design of the ELI-NP facility.

The first principle allows for a sequential buildup of the facility according to the available resources. For example, the first stage, 2011-2015, may target only the most basic physics topics and the basic facility components that need to be started immediately. The second stage might start from 2016 for five years, including new experiments and upgrading the laser power and gamma beam intensity and energy. Subsequently the third stage might start from 2021 for ten years. This stage might include the most ambitious and far reaching projects as well as the ones that are yet to be discovered by the preceding investigations till 2020. It may include an upgrade of the γ beam facility, using a superconducting energy recovery linac reaching to higher intensities of 10¹⁵ γ /s and improved bandwidth. For such a staged approach, it is necessary to build the first stage facility in such a way as to accommodate the future growth of the above.

ELI-NP will allow either combined experiments between the high-power laser and the γ beam or stand-alone experiments.

The γ beam will have unique properties in world wide comparison and opens new possibilities for high resolution spectroscopy at higher nuclear excitation energies. They will lead to a better understanding of nuclear structure at higher excitation energies with many doorway states, their damping widths, and chaotic behaviour, but also new fluctuating properties in the time and energy domain. The detailed investigation of the pygmy dipole resonance above and below the particle threshold is very essential for nucleosynthesis in astrophysics. In ion acceleration the high power laser allows to produce 10¹⁵ times more dense ion beams than achievable with classical acceleration. The cascaded fission-fusion reaction mechanism can then be used to produce very neutron-rich heavy nuclei for the first time. These nuclei allow to investigate the N = 126 waiting point of the r-process in nucleosynthesis. With this type of new laser acceleration mechanism very significant contributions to one of the fundamental problems of astrophysics, the production of the heavy elements beyond iron in the universe can be addressed. According to a recent report by the National Research Council of the National Academy of Science (USA), the origin of the heaviest elements remains one of the 11 greatest unanswered questions of modern physics. The γ beam also opens many new possibilities for applications. The γ beam itself can be used to map the isotope distributions of nuclear materials or radioactive waste remotely via Nuclear Resonance Fluorescence (NRF) measurements. At lower energies around 100 keV the high resolution of the beam is very important for protein structural analysis. In addition it will be produced low energy, brilliant, intense neutron beams and low energy, brilliant, intense positron beams, which open new fields in material science and life sciences. The possibility to study the same target with these very different brilliant beams will be unique and advance science much faster.

The high power laser allows for intensities of up to 10²⁴W/cm². Here very interesting synergies are achievable with the γ beam and the brilliant high energy electron beam to study new fundamental processes in high field QED. The use of the very high intensity laser and the very brilliant, intense γ beam will achieve major progress in nuclear physics and its associated fields like the element synthesis in astrophysics and many new applications or even to observe in fundamental physics the first catalysed pair creation from the quantum vacuum. In the field of basic nuclear physics, a better theoretical understanding of compound nuclear resonances in comparison with much improved experiments will also lead to better models for the element synthesis in astrophysics. Compared to former γ facilities, the much improved bandwidth is decisive for this new γ beam facility. Several experiments, like the parity violation experiment, only become possible due to this much better bandwidth. The large majority of γ beam experiments will profit proportionally from the better bandwidth, because the widths of the studied nuclear levels are significantly smaller than the width of the beam. Thus the ratio of "good" γ quanta within the nuclear linewidth compared to the "bad" γ quanta outside, which undergo Compton scattering and cause background in the detectors, will be significantly improved. Besides a wide range of fundamental physics projects also a variey of applied research will be enabled at ELI-NP. The project to develop techniques for remote characterization of nuclear materials or radioactive waste via NRF will gain large importance for society in Europe. The unsolved problems of long-term storage of radioactive waste from reactors, while having to deal with large amounts of old, insufficiently characterized radioactive waste requires a precise isotopic characterization in the first place. It may even turn out that a detailed in-situ characterization of partially used reactor fuel elements may result in producing more usable energy in reactors for the same amount of radioactive waste. On the other hand also the new production schemes of medical isotopes via (γ,n) may also reach socio-economical relevance. The new types of neutron sources and positron sources man reach large importance in material and life sciences.