Abstract
The development at ELI-NP of a new laser-based Inverse Compton
Scattering gamma beam system, featuring extremely high intensities at
very narrow bandwidths, opens new and important opportunities in nuclear
science research. Nuclear photonics is undergoing a revival, the gamma
beams with unprecedented features delivered at ELI-NP paving the way for
high accuracy and detailed nuclear physics studies. A wide range of
industrial, homeland security and healthcare applications will also
experience an important boost. The combination of nuclear photonics with
the technique of Nuclear Resonance Fluorescence (NRF) allows for the
recovery of several physical quantities characterizing the excited
nuclear states in a completely model independent way. These observables
include the excitation energies, level widths, gamma decay branching
ratios, spin quantum numbers, and parities.
In the last decade, the NRF technique allowed for the discovery and
detailed study of various phenomena in atomic nuclei. Examples are the
collective magnetic dipole Scissors Mode in deformed nuclei, quadrupole
excitations with mixed proton neutron symmetry, the electric Pygmy
Dipole Resonance, octupole coupled excitations, or alpha-cluster states.
The present Technical Design Report (TDR) deals with the application of
the NRF technique at ELI-NP to study forefront nuclear structure
research topics. The document presents some of the physics cases to be
investigated and discusses the feasibility of the proposed experiments.
The advanced characteristics of the gamma beams available at ELI-NP and
the use of high efficiency detection systems will offer a powerful
combination, unique in the world, for the investigation of the proposed
physics cases.
The main detection system for the NRF studies is a multi-detector array
(ELIADE - ELI-NP Array of DEtectors) based on the use of composite
high-purity Ge detectors and large volume LaBr3 scintillator detectors
able to detect with high efficiency gamma rays with energies up to
several MeV in the presence of the high radiation background produced by
the gamma beams. Gamma-ray energies and angular distributions will be
measured with high accuracy. The design of the array is made highly
flexible to allow for an easy transposition in different locations in
the high- and low-energy gamma beam areas, a fast change of
configuration based on the needs of the experiments, the use of the
detectors in other setups and easy maintenance to reduce the downtimes.
NRF measurements will be possible starting from early stages of the
Gamma Beam System operation at ELI-NP with both low- and high-energy
gamma beams. Already in the initial phase of operation at low-energies
below 3.5 MeV the gamma beams at ELI-NP will be competitive with the
present state-of-the-art gamma beam systems.
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