Basic Nuclear Science Research Articles

The neutron time-of-flight facility n_TOF at CERN Recent facility upgrades and detector developments

Based on an idea by Carlo Rubbia, the n_TOF facility at CERN has been operating for over 20 years. It is a neutron spallation source, driven by the 20 GeV/c proton beam from the CERN PS accelerator. Neutrons in a very wide energy range (from GeV, down to sub-eV kinetic energy) are generated by a massive Lead spallation target feeding two experimental areas. EAR1, horizonal with respect to the proton beam direction is set at 185 meters from the spallation target. EAR2, on the vertical line from the spallation source, is placed at 20 m. Neutron energies for experiments are selected by the time-of-flight technique (hence the name n_TOF), while the long flight paths ensure a very good energy resolution. Over one hundred experiments have been performed by the n_TOF Collaboration at CERN, with applications ranging from nuclear astrophysics (synthesis of the heavy elements in stars, big bang nucleosynthesis, nuclear cosmo-chronology), to advanced nuclear technologies (nuclear data for applications, nuclear safety), as well as for basic nuclear science (reaction mechanisms, structure and decay of highly excited compound states). During the planned shutdown of the CERN accelerator complex between 2019 and 2021, the facility went through a substantial upgrade with a new target-moderator assembly, refurbishing of the neutron beam lines and experimental areas. An additional measuring and irradiation station (the NEAR Station) has been envisaged and its capabilities for performing material test studies and new physics opportunities are presently explored. An overview of the facility and of the activities performed at CERN is presented in this contribution, with a particular emphasis on the most relevant experiments for nuclear astrophysics.

First demonstration of a triton beam using target normal sheath acceleration

Tritiated titanium targets were irradiated by the short-pulse OMEGA EP laser (1.25 kJ, 10 ps) to generate a laser-accelerated pulsed beam of tritons by target normal sheath acceleration. Using a Thomson parabola, the beam was found to contain 10 12 tritons per pulse, with a mean energy of 2.2 MeV and an exponential tail reaching up to 10 MeV. In a separate experiment, the triton beam was directed onto a secondary deuterated polyethylene (CD) target to induce deuterium–tritium (D–T) nuclear reactions. Using neutron time-of-flight spectrometers, approximately 10 8 D–T fusion neutrons were observed per laser pulse. This triton beam presents new research opportunities for the study of the 3 H(t, 2n) 4 He reaction and di-neutron transfers to lithium and beryllium that may produce exotic neutron-rich nuclei of interest to basic nuclear science, astrophysics, and inertial confinement fusion technology.

Strengthening scientific literacy on nuclear reactor and its application through Nuclear School

Amid its controversy for application in power generation, nuclear technology is still considered as promising technology for some other application such as in medicine, food, agriculture, water desalination, and other industrial uses. Therefore, knowledge on nuclear technology needs to be preserved and even to be improved. This paper presents an education and outreach activity on nuclear technology, called Nuclear School, as an effort to preserve and improve nuclear science and technology. It is held by the Center for Science and Accelerator Technology (PSTA), as a subsidiary of National Nuclear Energy Agency of Indonesia (BATAN). This activity allows physics and chemistry students, lecturers, and high school teachers in physics and chemistry engage with nuclear reactor and its scientists. By utilizing Kartini Reactor, a 100 kW(th) TRIGA Mark II research reactor type, the participants acquire basic nuclear science as well as reactor physics and operation both in classroom and practice. Safety aspect on radiation and nuclear reactor operation are also provided in order to improve public understanding on nuclear science and technology.

Status and prospects of nuclear data development in China

Nuclear data are fundamental data for nuclear science and technology. They play important roles in national defense, security, nuclear energy and nuclear technology, basic nuclear science development etc. Nuclear data connect basic nuclear science and nuclear applications. Research on nuclear data is a branch of nuclear physics. Many nuclear data works have been accomplished to feed the needs for various applications in the past 50 years in China. However, more and more attention has been paid to nuclear data in China according to the rapidly rising needs from nuclear energy and nuclear technology applications. To feed these needs, more experimental and theoretical basic works on nuclear data must be carried out. The nuclear data and their applications, review and frontier of nuclear data development in the world and also in China, the importance of basic research for nuclear data development are briefly described in this paper. Finally, the challenges, opportunities and proposals for nuclear data work in China in the near future are presented.

Determining the239Np(n,f)cross section using the surrogate ratio method

Background: Neutron-induced fission cross-section data are needed in various fields of applied and basic nuclear science. However, cross sections of short-lived nuclei are difficult to measure directly due to experimental constraints.Purpose: The first experimental determination of the neutron-induced fission cross section of ${}^{239}$Np at nonthermal energies was performed. This minor actinide is the waiting point to ${}^{240}$Pu production in a nuclear reactor.Method: The surrogate ratio method was employed to indirectly deduce the ${}^{239}\text{Np}(n,f)$ cross section. The surrogate reactions used were ${}^{236}\text{U}{(}^{3}\text{He},p)$ and ${}^{238}\text{U}{(}^{3}\text{He},p)$ with the reference cross section given by the well-known ${}^{237}\text{Np}(n,f)$ cross section. The ratio of observed fission reactions resulting from the two formed compound nuclei, ${}^{238}$Np and ${}^{240}$Np, was multiplied by the directly measured ${}^{237}\text{Np}(n,f)$ cross section to determine the ${}^{239}\text{Np}(n,f)$ cross section.Results: The ${}^{239}\text{Np}(n,f)$ cross section was determined with an uncertainty ranging between 4$%$ and 30$%$ over the energy range of 0.5--20 MeV. The resulting cross section agrees closest with the JENDL-4.0 evaluation.Conclusions: The measured cross section falls in between the existing evaluations, but it does not match any evaluation exactly (with JENDL-4.0 being the closest match); hence reactor codes relying on existing evaluations may under- or overestimate the amount of ${}^{240}$Pu produced during fuel burnup. The measurement helps constrain nuclear structure parameters used in the evaluations.

European Master of Science in Nuclear Engineering

Abstract The need to preserve, enhance or strengthen nuclear knowledge is worldwide recognised since a couple of years. Among others, “networking to maintain nuclear competence through education and training”, was recommended in 2001 by an expert panel to the European Commission [EUR, 19150 EN, Strategic issues related to a 6th Euratom Framework Programme (2002–2006). Scientific and Technical Committee Euratom, pp. 14]. It appears that within the European University education and training framework, nuclear engineering is presently still sufficiently covered, although somewhat fragmented. However, it has been observed that several areas are at risk in the very near future including safety relevant fields such as reactor physics and nuclear thermal–hydraulics. Furthermore, in some countries deficiencies have been identified in areas such as the back-end of the nuclear fuel cycle, waste management and decommissioning. To overcome these risks and deficiencies, it is of very high importance that European countries work more closely together. Harmonisation and improvement of the nuclear education and training have to take place at an international level in order to maintain the knowledge properly and to transfer it throughout Europe for the safe and economic design, operation and dismantling of present and future nuclear systems. To take up the challenges of offering top quality, new, attractive and relevant curricula, higher education institutions should cooperate with industry, regulatory bodies and research centres, and more appropriate funding from public and private sources. In addition, European nuclear education and training should benefit from links with international organisations like IAEA, OECD-NEA and others, and should include worldwide cooperation with academic institutions and research centres. The first and central issue is to establish a European Master of Science in Nuclear Engineering. The concept envisaged is compatible with the projected harmonised European architecture for higher education defining bachelors and masters degrees. The basic goal is to guarantee a high quality nuclear education in Europe by means of stimulating student and instructor exchange, through mutual checks of the quality of the programs offered, by close collaboration with renowned nuclear-research groups at universities and laboratories. The concept for a nuclear master program consists of a solid basket of recommended basic nuclear science and engineering courses, but also contains advanced courses as well as practical training. Some of the advanced courses also serve as part of the curricula for doctoral programs. A second important issue identified is Continued Professional Development. The design of corresponding training courses has to respond to the needs of industry and regulatory bodies, and a specific organisation has to be set up to manage the quality assessment and accreditation of the Continued Professional Development programs. In order to achieve the important objectives and practical goals described above, the ENEN Association, a non-profit association under French law, was formed. This international association can be considered as a step towards the creation of a virtual European Nuclear University symbolising the active collaboration between various national institutions pursuing nuclear education. Based on the concepts and strategy explained above, and with the full cooperation of the participating institutions, it may be stated that the intellectual erosion in the nuclear field can be reversed, and that high quality European education in nuclear sciences and technology can be guaranteed.

A thirty year look at the nuclear science programs at the American Museum of Science and Energy

The American Museum of Science and Energy has been involved in nuclear science education since it opened in 1949. For a period between the mid-1950's and the early 1980's, a series of traveling exhibits and demonstrations provided the nation with programs about basic nuclear science and peaceful applications of atomic energy. The Museum itself continues educating its visitors about nuclear science via audio-visuals, interactive exhibitry and live demonstrations and classes.