High Intensity Neutron Target
Development of High Power Solid State Neutron Production Targets for SPIRAL-II (GANIL, France) and SPES (LNL-INFN, Italy) Facilities.
Tech Area / Field
- PHY-ANU/Atomic and Nuclear Physics/Physics
- PHY-PFA/Particles, Fields and Accelerator Physics/Physics
8 Project completed
Senior Project Manager
Malakhov Yu I
Budker Institute of Nuclear Physics, Russia, Novosibirsk reg., Akademgorodok
- VNIITF, Russia, Chelyabinsk reg., Snezhinsk
- Istituto Nazionale di Fisica Nucleare (INFN) / Laboratori Nazionali di Legnaro, Italy, Padova
Project summaryThe current proposal aims at the development of high power solid neutron production target for SPIRAL-II (GANIL, France) and SPES (LNL-INFN, Italy) facilities. Reaching the goals of the project is provided by the implementation of necessary research, design, engineering and experimental works.
The possibility of the intense radioactive beams production opens new horizons for scientific research in nuclear physics and many other disciplines. New perspectives for the study of nuclei give the installations which produce the high intensity radioactive ion beams (RIB). Among different techniques to produce RIB, the Isotope Separation On-Line (ISOL) technique is the more promising to produce high-intensity short-lived exotic nuclei far from the valley of stability. First-generation ISOL-based facilities have produced their first results and have convincingly been shown to work. The next-generation ISOL based radioactive ion beam facilities, EURopean ISOL (EURISOL), aims at increasing, beyond 2015, the variety of radioactive beams and their intensities by order of magnitude over the ones available at present for various scientific disciplines including nuclear physics, nuclear astrophysics and fundamental interactions.
The second generation facilities SPIRAL-II (GANIL, France) and SPES (LNL, Italy) will allow one to bridge the gap between now and the operation of EURISOL. Furthermore, the technical developments required for these intermediate-scale projects such as high-power proton/deuteron (p/d) superconducting linear accelerator or high-power production targets are precisely the ones needed for EURISOL. Both facilities SPES and SPIRAL2, will offer a wide range of intense stable and radioactive beams. A neutron-induced fission and charge-particle-induced fission will be used to produce high-intensity beams of fission fragments. Fusion-evaporation and transfer reactions with high-intensity stable light- and heavy-ion beams will allow to deliver neutron-deficient and light radioactive ions. The intense Radioactive Nuclear Beams (RNB) can be used in turn to study nuclei even further out from stability line through secondary fusion evaporation or deep-inelastic reactions. The use of RIB also opens new perspectives for research in other fields, as well, such as, for example, atomic and solid state physics, material studies and medical applications. Each of these applications can get unique chances to choose isotopes with a most suitable life time, kinetic and decay energy, and chemical properties.
Thanks to the high energy and high intensity neuron flux available, SPES and SPIRAL2 facilities offers a unique opportunity for material irradiations both for fission and fusion related research, tests of various detection systems and of resistance of electronic components to irradiations, etc. Both facilities also could be considered as an intermediate step towards new generation dedicated irradiation facilities as IFMIF previewed only beyond about 2015.
Both SPIRAL-II and SPES facilities use the primary beam (protons for SPES and deuterons for SPIRAL2) accelerated in an RFQ (Radio Frequency Quadrupole) and a superconducting linac, directed to a dedicated neutron target converter and produces an intense (up to 3·1014cm-2s-1) flux of fast neutrons. The parameters of the primary beam are: energy up to 100 MeV, average power up to 200 kW, beam diameter 1 cm. The obtained neutron flux hits the hot thick fission target made of 238U compounds. The fission fragments are diffused at high temperature from the target, ionized and extracted at an energy of about 60 keV. Then, after being separated by mass, they are sent into the experimental area for low-energy experiments, or further accelerated up to an energy of few tens of MeV/nucleon and delivered to the experiments.
This production scheme is introduced to remove from the fissile target the heat produced while stopping the charged primary beam, mostly due to electronic stopping, whereas the useful nuclear reaction (i.e. fission) takes place in the fission target. This imply the development of high-performance, high reliability and high power neutron converter. Accurate analysis and investigations demonstrates that carbon is the most suitable and effective material to be employed as neutron converter because of its appropriate thermal properties. For such a reason both facilities, SPES and SPIRAL2, selected graphite as neutron converter. The neutron converter has been conceived as a high speed rotating target, which limits the peak surface temperature of converter materials well below 2000 °C.
The project proposed is aimed at the design and development of the most important components for the neutron production target. Its base is the original design of the rotating neutron production target with the converter made of graphite and cooled by thermal radiation. This design is developed at BINP in the framework of ISTC Project #2257 as a result of joint activity of BINP and VNIITF specialists. BINP gained the experience in the development and maintenance of various type accelerator complexes and systems, including particle sources and conversion systems. The basis of the development of target suspension clip and driving gear should be the liquid metal (hereinafter – LM) pumping circuit which was produced at BINP for LM targets and successfully operated for around 8000 hours. VNIITF has the unique experience in the solution of 3D problems of neutron, -quanta and charged particles transport in matter.
During the project implementation it is planned to carry out the calculations and the experimental simulation of main parts and assemblies of the installation.
Within the ISTC Project #2257 specialists from RFNC VNIITF have worked out a software package solving 3-D complex problems related to neutron, photon and charged particles transport in matter (PRIZMA code). This software package will be used to calculate the neutron flux from the converter, the energy deposition, radiation damage and the material activations, considering the biological shielding of local converter sub-systems.
The optimal design of the neutron target will be selected based on the analysis of the thermal and mechanical operation modes of a particular design.
Tests of driving gear prototype aims at the check-up of its efficiency and reliability under the conditions which are close to operational. The preliminary test methods comprise the prototype operation under the working conditions and providing/check-up the stability of its parameters.
The development of the check-up technology for the target assemblies is necessary to determine the regulation of complex testing the target assembly before its commissioning. It includes the development and testing the methods and corresponding equipment for target operational conditions simulations, as well as for control of assembly’s necessary parameters. In order to carry out the experiments it is proposed to construct a dedicated test-bench with the use of high power (up to 30 – 50 kW) low energy (30 – 70 keV) electron beam on the basis of the electron accelerator developed at BINP.
As a result of works listed above, there will be proposed the variant of high power intense neutron production target with LM driving gear and cooling, which will be optimized for SPES and SPIRAL-II projects’ operational conditions. Solutions proposed will undergo the designing, scientific and engineering work-out and experimental check-up.
During the task implementation the following main results will be obtained:
- calculations of the double differential neutron distribution in the target environment produced by deuteron beam of energy up to 100 MeV. These calculations will be useful for estimation of biological shielding, radiation damage and activation of the materials;
- designing and prototyping the liquid metal cooling systems and target driving gear, including the liquid metal hot pump, leading-in circuit, rotation motor, target assemblies;
- integrated calculations and optimization of main neutron production target subsystems, including their thermal and mechanical loads, activation, radiation damage and spatial distribution of dpa number;
- study and optimization of the biological shielding taking into account the real geometry of the leading-in channels;
- development of the technology for preliminary testing the separate target elements and assemblies in order to provide reliable and safety operational conditions.
Main result obtained during the project implementation should be the selection and work out the main technical solutions for the assemblies and the systems of the high power neutron production target, taking into account the features concerning their application at SPES (INFN-LNL, Italy) and SPIRAL-II (GANIL, France) facilities.
The project proposed could be considered as one of the R&D stages of SPES and SPIRAL-II projects. In future should be helpful the following its features:
- Results of calculation of a neutron spectrum from the natural carbon, irradiated with deuterons upon the energy of 100 MeV, as well as the target assembly activation.
- Results of development and testing the liquid metal driving gear prototype for the high power neutron production target.
- Results of development and testing the check-up methods of the high power neutron production target assemblies and systems.
We notice that R&D studies on liquid metal sub-system are of great interest and challenging for other projects aiming to use liquid metal targets for positron production, liquid collimators and other high power beam devices (i.e. ILC, FAIR, etc.).
The international collaborators will take an active part in discussing the project, reviewing the technical reports, consulting on the problems to arise in the course of the project execution, in preparing and carrying out the experiments. The close interaction with the collaborators means their direct and regular participation in the project discussions, consultations and expertise of the reports. In particular in the course of the project execution it is planned to carry out a few workshops with an obligatory attendance of the collaborators. Some of the experiments are also planned to be carried out together with the collaborator on the equipment temporarily provided by the collaborator, or to be arranged jointly with the collaborator.
The participation of researchers and engineers from VNIITF will help them to proceed from the development of nuclear applications to military purposes to civil research and engineering activities. They can also use the experience they have gained while working with radioactive materials, radiation protection, etc. for environmental safety in the course of research and experiments with a high level of radiation. Thus, there will be built a basis for their integration into big international projects on fundamental studies.
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