Brilliant Gamma Beam Research Articles

Experimental programme with high-brilliance gamma beams at ELI-NP

The emerging experimental program with brilliant gamma beams at the Extreme Light Infrastructure – Nuclear Physics (ELI-NP) facility is presented with emphasis on the day-one experiments which are under preparation. Experiments at ELI-NP will cover nuclear resonance fluorescence (NRF) measurements, studies of large-amplitude motions in nuclei, photo-fission and photonuclear reactions of astrophysics interest, and measurements of photonuclear reaction cross-sections. The physics cases of the flagship experiments at ELI-NP and the performance of the related instruments, which are under construction for their realization, are discussed.

An overview of the design of ELIPS—A new slow positron beam line

Abstract In this work, the progress made by the positron group from ELI-NP in the design of a new slow positron beam line is summarized. The rays of a brilliant gamma beam will be used to produce a slow positron beam of high intensity. The main results of the simulations, done for the geometry optimization of the Converter/Moderator Assembly (CMA) for γ -to-slow e + conversion, are reported. By using the γ -beam with energy of up to 3.5 MeV and intensity of 2 . 4 × 1 0 10 γ s − 1 , the slow e + beam can be obtained with a maximum intensity of ∼ 2 × 1 0 6 s−1 with tungsten or platinum CMA. Solid neon moderation is applicable, and a successful implementation will result in a slow e + beam of intensity > 1 0 7 s − 1 . The CMA can be operated with a central hole ( ⌀ = 2 . 5 mm) in the foils in parasitic mode, i . e . , simultaneously with other γ -beam experiments, at the cost of reduced intensity by 18%. Furthermore, details on the slow positron transport and the spectroscopic systems, which are under construction, are provided.

Highlights of the day-one experimental program at the gamma-beam system of ELI-NP

The emerging experimental program with brilliant gamma beams at the Extreme Light Infrastructure - Nuclear Physics facility (ELI-NP) is presented with emphasis on the prepared day-one experiments. Ex- periments at ELI-NP will cover nuclear resonance fluorescence measurements, studies of large-amplitude motions in nuclei, photo-fission and photonuclear reactions of astrophysics interest, and measurements of photonuclear reaction cross sections. The physics cases of the flagship experiments at ELI-NP and the performance of the related instruments, which are under construction for their realization, are discussed.

Experiments with brilliant gamma beams at ELI-NP: A glimpse in the future

The emerging experimental program with brilliant gamma beams at the Extreme Light Infrastructure – Nuclear Physics facility (ELI-NP), which is under construction in Magurele, Romania is presented with emphasis on the prepared day-one experiments. Experiments at ELI-NP will cover nuclear resonance fluorescence (NRF) measurements, studies of large-amplitude motions in nuclei, photofission and photonuclear reactions of astrophysics interest, and measurements of photonuclear reaction cross sections. The physics cases of the flagship experiments at ELI-NP are discussed, as well as the related instruments which are under construction for their realization.

Gamma-beam photofission experiments at ELI-NP: The future is emerging

At the Extreme Light Infrastructure - Nuclear Physics facility (ELI-NP), high-power laser systems together with high-brilliance gamma beams are the main research tools. The status of the construction of the facility is reported. The emerging photofission experimental program with brilliant gamma beams at ELI-NP is presented with emphasis on the prepared day-one experiments. The physics cases of the flagship experiments at ELI-NP are discussed, as well as the related instruments which are under construction for their realization.

Photodisintegration reactions for nuclear astrophysics studies at ELI-NP

Extreme Light Infrastructure - Nuclear Physics facility will come online in Bucharest-Magurele, Romania, in 2018 and will deliver high intensity laser and brilliant gamma beams. We present the physics cases and instruments proposed at ELI-NP to measure capture reactions by means of the inverse photodisintegration reaction. We propose to study the 16O(γ, α)12C reaction using a Time Projection Chamber detector with electronic readout. Several other reactions, such as 24Mg(γ, α)20Ne and reactions on heavy nuclei relevant in the p-process, are central to stellar evolution and will be investigated with a proposed Silicon Strip Detector array and a 4π neutron detector. The status of the experimental facilities and first-day experiments will be presented in detail.

Project for a Source of Polarized Slow Positrons at ELI-NP

We describe the status of a project for obtaining an intense beam of polarized slow positrons at the Extreme Light Infrastructure - Nuclear Physics (ELI-NP) at Magurele (near Bucharest, Romania) [1]. Positrons will be created via pair production and moderated at a tungsten target using the pulsed brilliant gamma beam which will be produced by Compton back-scattering of circularly polarized laser photons on electrons from a warm linac beam [2]. Simulations of the interaction of circularly polarized γ‑rays of energies up to 3.5 MeV and an intensity of 2.4×1010γ/s with the target, moderation of created positrons and beam formation are discussed. The optimization of the target design showed that the primary slow positron beam can be obtained with intensity of 1‑2×106e+/s. The primary beam will be transversally polarized with a degree of polarization of ~30%. We discuss the necessity of changing the e+ beam polarization from transversal to longitudinal by an electrostatic 90˚ bender which is proposed to work in combination with a remoderator. Simulations show that neither the remoderator nor the electrostatic bender will change the degree of e+ beam polarization. The longitudinally polarized e+ can be successfully transported to the sample chambers without depolarization, but with reduced intensity (by approximately one order of magnitude) due to the remoderation. We present a convertor-moderator assembly with a hole which will allow creating positrons in parasitic mode, i.e., simultaneously with the nuclear physics experiments at ELI-NP. The positron spectroscopy laboratory at ELI-NP will be user dedicated and the beam will have the highest intensity of polarized slow positrons for material science in the world and therefore it could become a unique tool for investigation of magnetic samples.

Status of the project for a positron laboratory at ELI-NP

We report on the plans of a positron laboratory to be built at the Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility. The slow e+ source is based on e−–e+ pair production in a converter made of tungsten foils by a brilliant gamma beam (Eγ<3.5 MeV, Iγ = 2.4×1010 γ s-1) which will be generated by Compton back–scattering of photons from a high power laser on electrons from a LINAC. Numerical simulations of γ–ray interactions with the designed converter showed that, if the tungsten foils are used for moderation of the created fast e+, a slow e+ beam of an intensity of ~1×106 s-1 can be obtained. Circular polarization of the γ-beam is proposed to be one of the ELI-NP’s upgrades. The slow e+ will be extracted perpendicularly to the γ–beam and will have ~ 30% transversal polarization degree. By using a transmission re-moderation stage and electrostatically turning the re–moderated beam by 90°, the transversal polarization will be changed to longitudinal. Longitudinal polarization can then be preserved in the longitudinal magnetic guiding field. The heat load to the converter was estimated at < 2 mW which implies that e+ moderation by frozen neon is applicable.

New light in nuclear physics: The extreme light infrastructure

Extreme Light Infrastructure-Nuclear Physics (ELI-NP), to become operational in 2019, is a new Research Center built in Romania that will use extreme electromagnetic fields for nuclear physics research. The ELI-NP facility will combine two large equipments with state-of-the-art parameters, namely a 2 × 10 PW high-power laser system and a very brilliant gamma-beam system delivering beams with energies up to 19.5 MeV. The laser and gamma-beam systems under construction and typical proposed first-phase experiments are described.

Brilliant gamma beams for industrial applications: new opportunities, new challenges

The Nuclear Physics oriented pillar of the pan-European Extreme Light Infrastructure (ELI-NP) will host an ultra-bright, energy tunable, and quasi-monochromatic gamma-ray beam system in the range of 0.2-19.5 MeV produced by laser-Compton backscattering technique. The applied research program envisioned at ELI-NP targets to use nuclear resonance fluorescence (NRF) and computed tomography to provide new opportunities for industry and society. High sensitivity NRF-based investigations can be successfully applied to safeguard applications and management of radioactive wastes as well as to uncharted fields like cultural heritage and medical imaging. Gamma-ray radioscopy and computed tomography performed at ELI-NP has the potential to achieve high resolution in industrial-sized objects provided the detection challenges introduced by the unique characteristics of the gamma beam are overcome. Here we discuss the foreseen industrial applications that will benefit from the high quality and unique characteristics of ELI-NP gamma beam and the challenges they present. We present the experimental setups proposed to be implemented for this goal, discuss their performance based on analytical calculations and numerical Monte-Carlo simulations, and comment about constrains imposed by the limitation of current scintillator detectors. Several gamma-beam monitoring devices based on scintillator detectors will also be discussed.

Investigation of the d(γ,n)p reaction for gamma beam monitoring at ELI-NP

The Extreme Light Infrastructure - Nuclear Physics facility will deliver brilliant gamma beams with high spectral density and a high degree of polarization starting in 2018 in Bucharest-Magurele, Romania. Several monitoring instruments are proposed for measuring the spectral, temporal, and spatial characteristics of the gamma beam. The d(γ,n)p reaction has been investigated for its use in determining the gamma beam parameters in a series of measurements carried out at the High Intensity Gamma Source, Durham, U.S.A.. Measurements of the emitted neutrons have been performed using liquid scintillator and 6Li-glass neutron detectors at several incident gamma energies between 2.5 to 20 MeV . The experimental results presented in this paper have shown that an instrument based on the d(γ,n)p reaction can be used to monitor the intensity and polarization of the gamma beam to be produced at ELI-NP.

Simulation of photofission experiments at the ELI-NP facility

An extensive experimental program for the study of photofission will take place at the Extreme Light Infrastructure – Nuclear Physics (ELI-NP) facility, where different actinide targets will be exposed to a brilliant gamma beam to produce fission fragments. We report on the implementation within the Geant4 simulation toolkit of the photofission process, of related background processes, and of extended ionic charge parameterization. These developments are used to evaluate the production rates of photofission fragments and their release efficiency from the actinide targets.

Extreme Light Infrastructure Nuclear Physics (ELI–NP): Present status and perspectives

Extreme Light Infrastructure – Nuclear Physics (ELI–NP), a new Research Center under construction, will use extreme electromagnetic fields for nuclear physics research and will be operational in 2018. The status of the Project implementation will be presented. At ELI–NP, a high power laser system together with a very brilliant gamma beam are the two main research tools. Their targeted operational parameters will be described. The related experimental set-ups will be presented, together with the main directions of the research envisioned.

Nuclear physics with advanced brilliant gamma beams at ELI–NP

The Extreme Light Infrastructure - Nuclear Physics facility is dedicated to nuclear physics studies with the use of extreme electromagnetic radiation. One of the main research system to be installed and operated in the facility is an outstanding high brilliance gamma beam system. The Gamma Beam System of ELI–NP will produce intense, quasi–monochromatic gamma beams via inverse Compton scattering of short laser pulses on relativistic electron beam pulses. The gamma beams available at ELI–NP will allow for the performance of photo-nuclear reactions aiming to reveal the intimate structure of the atomic nucleus. Nuclear Resonance Fluorescence, photo-fission, photo-disintegration reactions above the particle threshold will be used to study the dipole response of nuclei, the structure of the Pygmy resonances, nuclear processes relevant for astrophysics, production and study of exotic neutron–rich nuclei.

Source of slow polarized positrons using the brilliant gamma beam at ELI-NP. Converter design and simulations

Simulations of slow positron (es+) source based on interaction of a circularly polarized gamma beam with a W converter were performed. The aim of the study was to propose a converter geometry and to determine the expected slow positron beam intensity and its spot size, and the degree of positron spin polarization, as well. The Monte Carlo simulations by means of GEANT4 were used to estimate the fast positron production and the moderation efficiency of the converter working as a self-moderator, as well. Finite element analysis by means of COMSOL Multiphysics was applied to calculate the fraction of extracted moderated positrons from the converter cells and the quality of the beam formation by focusing. Using the low energy (<3.5MeV) gamma beam at ELI-NP with intensity of 2.4×1010γ/s the production of a slow positron beam with intensity of 1–2×106es+/s is predicted. For the optimized converter geometry and in case of 100% circular polarization of the gammas the degree of spin polarization of the slow positron beam is expected to be 33%.

The ELI–NP facility for nuclear physics

Extreme Light Infrastructure–Nuclear Physics (ELI–NP) is aiming to use extreme electromagnetic fields for nuclear physics research. The facility, currently under construction at Magurele–Bucharest, will comprise a high power laser system and a very brilliant gamma beam system. The technology involved in the construction of both systems is at the limits of the present-day’s technological capabilities. The high power laser system will consist of two 10PW lasers and it will produce intensities of up to 1023–1024W/cm2. The gamma beam, produced via Compton backscattering of a laser beam on a relativistic electron beam, will be characterized by a narrow bandwidth (<0.5%) and tunable energy of up to almost 20MeV. The research program of the facility covers a broad range of key topics in frontier fundamental physics and new nuclear physics. A particular attention is given to the development of innovative applications. In the present paper an overview of the project status and the overall performance characteristics of the main research equipment will be given. The main fundamental physics and applied research topics proposed to be studied at ELI–NP will also be briefly reviewed.

Future Experiments with Intense Laser Beams and Brilliant Gamma Beams at the ELI-NP Facility

The Extreme Light Infrastructure (ELI) Pan-European facility initiative represents a major step forward in quest for extreme electromagnetic fields. Extreme Light Infrastructure Nuclear Physics (ELI-NP) is one of the three pillars of the ELI facility, that aims to use extreme electromagnetic fields for nuclear physics and quantum electrodynamics research. At ELI-NP, high-power lasers together with a very brilliant gamma beam are the main research tools. Their targeted operational parameters are described. The emerging experimental program in the field of nuclear physics of the facility is reported. The different instruments which are considered to operate in the ELI-NP experimental halls are discussed, with an emphasis on the instrumentation which is designed for nuclear structure, reactions and astrophysics research.

Photoneutron cross section measurements on Sm isotopes

The Extreme Light Infrastructure - Nuclear Physics, one of the three pillars of the Extreme Light Infrastructure Pan-European initiative, is a new large scale facility dedicated to nuclear physics with extreme electromagnetic fields. ELI-NP will host two 10 PW lasers and a very brilliant Gamma beam system with unprecedented intensity and energy resolution parameters. We propose to perform photon induced nuclear reactions using the very brilliant γ -ray beams provided by the Gamma beam system to examine in detail the photon absorption process and its decay modes. Here the experimental program related to nuclear research on reactions above the neutron separation threshold, which is under preparation at ELI-NP, is presented.

Extreme Light Infrastructure – Nuclear Physics (ELI-NP) European Research Centre

Extreme Light Infrastructure (ELI) is one of the 48 infrastructures of the European Strategic Forum for Research Infrastructure (ESFRI) roadmap and represents a major step forward in quest for producing extreme electromagnetic fields. Extreme Light Infrastructure – Nuclear Physics (ELI-NP) is one of the three pillars of the ELI initiative, which aims to use extreme electromagnetic fields for nuclear physics research. A high power laser system and a very brilliant gamma beam are the two main research equipment at the core of ELI-NP. Their targeted operational parameters are described. The related experimental areas are also presented, together with the main directions of the proposed scientific programme.

82 SUBMILLIMETER NUCLEAR MEDICAL IMAGING WITH A COMPTON CAMERA USING TRIPLE COINCIDENCES OF COLLINEAR BETA+− ANNIHILATION PHOTONS AND GAMMA RAYS

PET cameras had their breakthrough as an imaging instrument for clinical application studies due to the large variety of radioactively labeled tracer molecules [1]. These tracers carry an e emitting isotope to e.g. a tumor. Annihilation of the positron into two back-to-back 511 keV photons allows to restrict the source origin in 2 dimensions onto a line of response (LOR). Superimposing the LORs of different decay events locates the source distribution of the emitter in 3D. Modern PET systems reach a spatial resolution of 3-10 mm. A disadvantage of this technique is the diffusion of the positron before its decay with a typical range of ca. 1 mm (depending on its energy). This motion and Compton scattering of the 511 keV photons within the patient limit the performance of PET. We present a nuclear medical imaging technique, able to reach submillimeter spatial resolution in 3 dimensions with a reduced activity application compared to conventional PET. This ’gamma-PET’ technique draws on specific e sources simultaneously emitting an additional photon with the β decay. Exploiting the triple coincidence between the positron annihilation and the third photon, it is possible to separate the reconstructed ’true’ events from background [2,3]. Therefore the spatial uncertainty introduced by the motion of the e or by Compton scattering within the patient can be strongly reduced in the direction normal to the annihilation. Especially Sc is of interest, which β decays into Ca, emitting an 1157 keV photon. With its halflife of 3.9 h, Sc has to be produced from a Ti generator (t1/2 = 60.4 a) [4]. Presently this cannot be performed in clinically relevant quantities, however, this may change with the soon expected availability of highly brilliant gamma beams [2]. Sc has already been applied in patient studies [5]. We combined the Compton camera technique, i.e. the measurement of photon energies and positions of Compton scattering interactions, with a PET camera defining the LOR. Due to the Compton kinematics and subsequent photon absorption, a Compton camera can reconstruct the origin of a primary photon on the surface of a ’Compton cone’ [6]. Superimposing such cones from different events reduces