Targets for high repetition rate laser facilities: Needs, challenges and perspectives

A number of laser facilities coming online all over the world promise the capability of high-power laser experiments with shot repetition rates between 1 and 10Ã\u82 Hz. Target availability and technical issues related to the interaction environment could become a bottleneck for the exploitation of such facilities. In this paper, we report on target needs for three different classes of experiments: Dynamic compression physics, electron transport and isochoric heating, and laser-driven particle and radiation sources. We also review some of the most challenging issues in target fabrication and high repetition rate operation. Finally, we discuss current target supply strategies and future perspectives to establish a sustainable target provision infrastructure for advanced laser facilities

On the possibility of laser-plasma-induced depopulation of the isomer in ⁹³Mo at ELI-NP

High-power PW laser systems (HPLS) provide intense beams of accelerated reaction-driving protons simultaneously with spatially localized keV-plasmas. We herein depict our groundwork and strategy to use these unique features of the HPLS at the Extreme Light Infrastructure (ELI-NP) by exposing the long-lived nuclear isomer 93mMo at 2.425 MeV (t1/2 = 6.85 h) to plasma facilitating the local petawatt beamlines. An intermediate short-lived (t1/2 = 3.52 ns) state situated only 4.85 keV above 93mMo constitutes a gateway to allow for its prompt release. The controllable release of the nuclear isomer energy will henceforth enable harvesting energy densities in the nuclear regime of GJkg-1 (‘Nuclear Battery’). The campaign was inspired by the observation of the triggered release of via the intermediate state by Chiara et al. [1] published in Nature. They assigned the hitherto elusive Nuclear Excitation by Electron Capture (NEEC) as the driving process and claimed a very high probability of PexpNEEC= 0.010(3). However, these claims are challenged by experimentalists [2, 3] and theory [4]. We herein outline our strategy following bespoke theoretical guidance in the quest to unambiguously and independently demonstrate the onset of NEEC in 93mMo. With the yield estimations derived for our forthcoming HPLS experiment at ELI-NP, we draw optimism to resolve the current conundrum between the conflicting experimental observations and theoretical interpretations as discussed in world-leading journals and to pave the way for the future utilization of isomer depopulation in applied physics

Laser driven nuclear physics at ELI-NP

The Laser Beam Delivery (LBD) system technical design report covers the interface between the High Power Laser System (HPLS) and the experiments, together with the pulse quality management. The laser transport part of the LBD has a number of subsystems as follows: the beam transport lines for the six main outputs of HPLS, the additional short and long pulses and the synchronization system including the timing of the laser pulses with the Gamma Beam System (GBS) and the experiments on femtosecond timescale. Pulse quality management, discussed further here, consist in the generation and delivery of multiple HPLS pulses, coherent combining of the HPLS arms, laser pulse diagnostics on target, laser beam dumps, shutters and output energy adaption

NUCLEAR RESONANCE FLUORESCENCE EXPERIMENTS AT ELI-NP

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

Laser driven nuclear physics at ELI–NP

High power lasers have proven being capable to produce high energy γ-rays, charged particles and neutrons, and to induce all kinds of nuclear reactions. At ELI, the studies with high power lasers will enter for the first time into new domains of power and intensities: 10 PW and 1023 W/cm2. While the development of laser based radiation sources is the main focus at the ELI-Beamlines pillar of ELI, at ELI-NP the studies that will benefit from High Power Laser System pulses will focus on Laser Driven Nuclear Physics (this TDR, acronym LDNP, associated to the E1 experimental area), High Field Physics and QED (associated to the E6 area) and fundamental research opened by the unique combination of the two 10 PW laser pulses with a gamma beam provided by the Gamma Beam System (associated to E7 area). The scientific case of the LDNP TDR encompasses studies of laser induced nuclear reactions, aiming for a better understanding of nuclear properties, of nuclear reaction rates in laser-plasmas, as well as on the development of radiation source characterization methods based on nuclear techniques. As an example of proposed studies: the promise of achieving solid-state density bunches of (very) heavy ions accelerated to about 10 MeV/nucleon through the RPA mechanism will be exploited to produce highly astrophysical relevant neutron rich nuclei around the N~126 waiting point, using the sequential fission-fusion scheme, complementary to any other existing or planned method of producing radioactive nuclei. The studies will be implemented predominantly in the E1 area of ELI-NP. However, many of them can be, in a first stage, performed in the E5 and/or E4 areas, where higher repetition laser pulses are available, while the harsh X-ray and electromagnetic pulse (EMP) environments are less damaging compared to E1. A number of options are discussed through the document, having an important impact on the budget and needed resources. Depending on the TDR review and subsequent project decisions, they may be taken into account for space reservation, while their detailed design and implementation will be postponed. The present TDR is the result of contributions from several institutions engaged in nuclear physics and high power laser research. A significant part of the proposed equipment can be designed, and afterwards can be built, only in close collaboration with (or subcontracting to) some of these institutions. A Memorandum of Understanding (MOU) is currently under preparation with each of these key partners as well as with others that are interested to participate in the design or in the future experimental program