Compact Neutron Generator Research Articles

Directed pulsed neutron source generation from inverse kinematic reactions driven by intense lasers

Neutron production driven by intense lasers utilizing inverse kinematic reactions is explored self-consistently by a combination of particle-in-cell simulations for laser-driven ion acceleration and Monte Carlo nuclear reaction simulations for neutron production. It is proposed that laser-driven light-sail acceleration from ultrathin lithium foils can provide an energetic lithium-ion beam as the projectile bombarding a light hydrocarbon target with sufficiently high flux for the inverse p(Li7,n) reaction to be efficiently achieved. Three-dimensional self-consistent simulations show that a forward-directed pulsed neutron source with ultrashort pulse duration 3 ns, small divergence angle 26°, and extremely high peak flux 3 × 1014n/(cm2⋅s) can be produced by petawatt lasers at intensities of 1021 W/cm2. These results indicate that a laser-driven neutron source based on inverse kinematics has promise as a novel compact pulsed neutron generator for practical applications, since the it can operate in a safe and repetitive way with almost no undesirable radiation.

Preliminary study on temperature distribution and pyroelectric current of LiNbO3 heated by nanosecond pulse laser

In order to reduce the volume of compact neutron generators, a lot of investigations are carried out on generating high voltages by heating pyroelectric crystals with external heating. Laser irradiation is an effective non-contact heating method. Different laser parameters determine the crystal's temperature distribution, impacting the accelerating electric field. A preliminary study on the temperature distribution and pyroelectric current response of LiNbO3 heated by nanosecond pulse laser is presented, including both direct heating and heating with Cu and Ti disks adhered to the crystal. A two-dimensional transient heat transfer and circuit model is constructed in COMSOL. To validate the simulation model of temperature field distribution, FLIR thermal camera is utilized to measure the temperature in laser spot center experimentally. The experimental results coincide with simulations, which prove that the simulation model can predict temperature field distribution of the pyroelectric crystal effectively. This study can benefit the optimization of laser parameters for modulating high-quality deuterium ion acceleration fields.

Measurement of potassium in rats using an In vivo neutron activation analysis system

Abnormal levels of potassium are linked to several health conditions, including high blood pressure, cardiac dysfunction, kidney damage, and osteoporosis. Given the limited availability of in vivo measurement techniques, there is a need for novel methods to measure potassium to enhance the diagnosis and management of potassium metabolism related diseases. This study aimed to evaluate the feasibility of compact neutron generator based in vivo measurement system for quantification of potassium using rat carcasses. A cohort of thirty-nine rats (n = 20 males and 19 females, average weight 255 ± 15 and 163 ± 7 g) were sacrificed, and their carcasses were placed in polyethylene bottles. The rats were then positioned and irradiated in a carefully designed irradiation cave built alongside the neutron generator with an optimized thermal neutron flux and radiation dose ratio. The irradiation time was 10 min, followed by a 5-min decay and 2-h measurement using a high efficiency high purity germanium detector(HPGe). ResultsThe average potassium concentration in male and female rats was found to be comparable (male 2874 ± 161 and female 2866 ± 144 μg/g). A marginally positive correlation between potassium concentration and weight was found in female rats only (male(20) = 0.07, P = 0.76 and female r(19) = 0.34, P = 0.15). We assessed the influence of manganese toxicity on potassium levels and observed no significant impact. These results were consistent with our previous study in mice. ConclusionThis study suggests that in vivo neutron activation analysis could serve as a promising method to quantify potassium and to investigate the storage and metabolism of potassium in human and in animals.

Preliminary study of a compact pulsed deuterium-deuterium neutron generator with a vacuum arc ion source and a linear induction accelerator

The pulsed neutron beam combined with the time-of-flight (TOF) technique has shown great value in many scientific research and application fields. Most of the neutron-based material identification and interrogation systems require an intense pulsed neutron beam. Time resolved prompt gamma neutron activation analysis (T-PGNAA) is an effective analytical method to greatly suppress interference from the other elements or the neutron shields of the detectors. To develop T-PGNAA method in a compact accelerator neutron source, a novel intense pulsed deuterium-deuterium (D-D) neutron generator based on a linear induction accelerator (LIA) was introduced. The generator has four major components: a vacuum arc ion source with deuterated electrode, a diode accelerator structure, a self-biased voltage secondary electron suppressed structure and a deuterated metal target. The present study characterizes the performance of the neutron generator with respect to neutron yield, the ionic current, beam profile, and beam composition as a function of the acceleration voltage at various discharge currents. Monoenergetic neutrons (2.5 MeV) are produced with a yield of ∼104 n/p and a pulse width of ∼100 ns using about 200 kV of induction acceleration voltage at 10−4 Pa vacuum environment. In this study, we will discuss various physical and technical issues related to the components of the neutron generator and the operation and merits of the novel neutron generator.

A protype of compact and high-yield DD neutron generator

Neutron generators are widely utilized in various fields, including scientific research, activation analysis, and detection of IED or drugs, due to their high neutron yield, safety, and flexibility. In this paper, we report about the development of a compact and high-yield dd neutron generator based on an Electron Cyclotron Resonance (ECR) ion source at the China Institute of Atomic Energy. The ion source to produce a high-intensity ion beam, which is used to bombard a water-cooled solid metal target. By means of the (D, D) nuclear reaction, 2.5MeV neutrons are generated. We describe the detailed design of this compact dd neutron generator and present the preliminary measurement results of its neutron yield, as measured by a calibrated 3He neutron detector. The generator has been tested for nearly 300 hours, demonstrating stable operation without any component damage. With its compact size, high yield, and long lifespan, this generator could meet the demand for a 2.5MeV neutron source in many scientific research and select industrial applications.

Characterization Measurements of Compact Neutron Generators of the New NILE Facility

Characterization Measurements of Compact Neutron Generators of the New NILE Facility

Current status and development of neutron radiation for biophysical applications in Colombia.

In Colombia, medical physics started formally about 3 decades ago. Two master's programs in medical physics initiated activities at two different universities. In particular, the master's program at the Pontificia Universidad Javeriana has been underway since 2012, and taking into account its projections, a team was established in 2015 in collaboration with the Universidad Distrital Francisco José de Caldas to conduct basic research on cancer treatment using neutron capture therapy (NCT). The primary goal of our initiative is to create the infrastructure required to adapt new technologies in our universities in the future. The long-term objective is to use neutron radiation to study not only NCT but also biomolecules, membranes, and materials. This will require the commissioning of an actual nuclear facility. Our group has been exclusively focused on carrying out calculations with GEANT4 because of its characteristics as open-source software, its accessibility, and its ample worldwide use and validation in the particle physics, nuclear physics, and medical physics communities. In this work, we present some results of our preliminary design for the ion accelerator column of a compact neutron generator. Also, we present the characterization of the kinematical and dose distributions of boron neutron capture processes using Geant4.

High-Flux Neutron Generator Based on Laser-Driven Collisionless Shock Acceleration.

A novel compact high-flux neutron generator with a pitcher-catcher configuration based on laser-driven collisionless shock acceleration (CSA) is proposed and experimentally verified. Different from those that previously relied on target normal sheath acceleration (TNSA), CSA in nature favors not only acceleration of deuterons (instead of hydrogen contaminants) but also increasing of the number of deuterons in the high-energy range, therefore having great advantages for production of high-flux neutron source. The proof-of-principle experiment has observed a typical CSA plateau feature from 2 to 6MeV in deuteron energy spectrum and measured a forward neutron flux with yield 6.6×10^{7} n/sr from the LiF catcher target, an order of magnitude higher than the compared TNSA case, where the laser intensity is 10^{19} W/cm^{2}. Self-consistent simulations have reproduced the experimental results and predicted that a high-flux forward neutron source with yield up to 5×10^{10} n/sr can be obtained when laser intensity increases to 10^{21} W/cm^{2} under the same laser energy.

Measurement of dosimetrical cross sections with 14.05 MeV neutrons from compact neutron generator

This paper deals with the measurement of the differential dosimetry cross sections using a small compact D-T neutron generator with 14.05 ± 0.08 MeV neutron emission (1 × 108 n/s into 4π). In spite of low neutron flux, it is possible to get measurable gamma-ray activities by irradiating a larger amount of target material placed in close geometry. The experimentally determined cross sections are in good agreement with the cross sections in the IRDFF-II dosimetry library. The comparison with other nuclear data libraries was performed as well. It is worth noting that the mean standard deviation in IRDFF-II library is about 4 %, while in the case of other data libraries they are from 5.5 % to 7.5 %. This result can be understood as a validation of IRDFF-II using 14.05 MeV neutrons and also a confirmation of the applicability of small compact generators in the measurement of activation cross sections.

Towards the use of SDD as an absolute detector for high-energy neutron measurements

As of today, the standard method employed in tokamaks for the absolute measurement of the neutron flux (thus of the nuclear fusion power) is based on activation foils, being the most robust and unbiased technique for the absolute determination of neutron fluence. However, this technique is not able to provide real-time data useful for the control of future fusion plants like DEMO. In this paper, we present some preliminary results about the R&D activity aimed at developing the Single-crystal Diamond Detectors (SDD) used for fast neutron measurements into an absolute neutron flux monitor. Tests have been conducted at the new NILE neutron source of the Rutherford-Appleton Laboratory, a facility with compact neutron generators with a maximum yield of 109 n/s and 1010 n/s for 2.5 MeV and 14 MeV neutrons, respectively. A series of neutron spectra and flux measurements have been taken with different SDD and associated DAQ. Comparisons with standard activation foils (and namely Fe, Zr, Al and Nb foils for 14 MeV neutrons and In for 2.5 MeV neutrons) and with other reference detectors are presented and discussed. Also discussed is the stability of the SDD over time when employed at high neutron rates in realistic neutron environment, and the effects of neutron irradiation on both the counting rate and detector resolution.

Evaluation of the scintillation screens used for low energy pulsed ion beam profiling

For a compact pulsed sealed-tube neutron generator using vacuum arc as ion source, an ion beams diagnostic system based on scintillation screen was established. And the transverse intensity distribution of the deuterium ions on the target of the pulsed neutron generator was obtained. In order to validate the accuracy of the diagnostic system, the ion irradiation effect of the Al2O3, Quartz and YAP scintillation screens were studied. Steady pulsed deuterium ion beam with energy and intensity comparable to the pulsed ion beam used in the neutron generator was let continuously irradiated on the scintillation screens, and the light yield and spot size changes of the screens were recorded. Results showed that, YAP screens own the worst radiation hardness among the three. For Al2O3 and Quartz screens, though their light yield degraded with the ion radiation, the measured beam profile almost not changed for integrated beam intensity of up to 2.5 × 1014 ions/mm2. Therefore, the diagnostic system can provide accurate results for the ion beam diagnostic for neutron generators.

A COMPACT NEUTRON GENERATOR FOR THE NIORT® TREATMENT OF SEVERE SOLID CANCERS

In the last four years, TheranostiCentre S.r.l., Berkion Technology LLC and ENEA have patented and fabricated a first prototype of a Compact Neutron Generator (CNG) currently under testing in the ENEA laboratories. Besides the usual applications in the field of materials irradiation, this CNG - producing neutrons of 2.45 MeV energy by using the DD fusion reaction - was conceived for the neutron irradiation of the solid cancer’s tumour bed by means of the Intra-Operative Radiotherapy (IORT) technique, the so-called neutron-IORT (nIORT®). The CNG is self-shielded and light-weight (~120 kg) making possible its remote handling by a robotic arm. Accurate Monte Carlo simulations, modelling the CNG and the “open wound” biological tissues near its irradiation window, demonstrated that the apparatus - operated at 100 kV-10 mA - supplies a neutron flux ~108 cm-2 s-1 and can deliver equivalent dose rates ~2 Gy (RBE)/min. Hence, it can administer very high dose levels in limited treatment times. This article briefly summarizes the main findings of this collaborative research study, the clinical rationales underpinning the nIORT® idea and the potential performances of the CNG for the treatment of solid cancer pathologies. Indeed, the CNG can be installed in an operating room dedicated to nIORT® treatments, without posing any environmental and safety issues. Monte Carlo simulations have been carried out by envisioning the CNG equipped with an IORT applicator, that is an applicator pipe with a tuneable diameter to be inserted in the surgical cavity. By foreseeing the clinical endpoints of the standard IORT protocols, the irradiation performances for potential nIORT® treatments - obtained with an applicator pipe of 6 cm diameter - are here reported for different regimes: from 10 up to 75 Gy (RBE), that can be administered in a single session of about 4 to 30 minutes. Besides the dose peak in the centre of the tumour bed, the almost isotropic neutrons emission allows to irradiate the surroundings side-walls of the tumour bed – usually filled by potential quiescent cancer cells (QCCs) – and therefore reducing the chances of local recurrences by improving the local control of the tumour. The rapid decrease in tissues depth of the dose profile (in few centimetres) will spare the neighbouring organs at risk from harmful radiations. Thus, the CNG apparatus developed for nIORT® applications can potentially improve the resectability rate of a given neoadjuvant cancer treatment and, generally, could satisfy all five R’s criteria of radiotherapy. Furthermore, in comparing with the current IORT techniques with electrons or low-keV X-rays, the nIORT® exploiting a high-flux neutrons beam of 2.45 MeV energy could lead to some significant clinical advantages due to its larger Linear Energy Transfer (LET, ~ 40 keV/m as average) and significantly higher Relative Biological Effectiveness (RBE 16) than all other forms of ionizing radiation.

Local Production of the Alpha-Emitting Radioi-sotope Actinium 225 with Low Impurities for Targeted Alpha Ther-apy by a Compact Neutron Generator System

Alpha-particle emitting radioisotope Actinium225 (225Ac) is of great interest for use in Targeted Alpha Therapy (TAT) treatments of e.g., brain tumors, bladder cancer, neuroendocrine tumors and leukemia. A suitable 225 Ac radioligand is also potentially resolutive for the treatment of advanced and metastatic Castration-Resistant Prostate Cancers (mCRPCs). The mCRPC has a mean survival rate of 9-36 months and encompasses a heterogeneous ample range of molecular cancer behavior with a high risk of progression. Global demand for the 225 Ac has spurred several production efforts including extraction from 233U, high energy protons or photon irradiation of 226Ra or spallation of 232Th by, at least, 100 MeV protons. Instead of using accelerators systems such as cyclotrons or LINACs, a Compact Neutron Generator (CNG) system has been developed. A 400kV-10 mA DC (D_7Li) CNG potentially able to produce substantial amount of 225Ac with low 227Ac impurities is here presented. Exploiting the high flux of 10 and 13 MeV energy neutrons generated by the (D_7Li) reactions to bombard a thin target layer of 226Ra, 225Ra/225Ac is produced via the 226Ra(n,2n)225Ra nuclear reaction. By irradiating a 5 mm thick 226Ra layer for 100 hours, about 11-13 mCi of 225Ac can be produced – corresponding to the TAT treatment of about 65 oncological patients – with an estimated 227Ac contamination of about one percent, which is below the acceptable limit for clinical use. This 225Ac production scheme by a suitable CNG should allow to adopt a local/regional approach avoiding the shipment costs of 225Ac. The aim of this paper is to inform the production chain of radioisotopes to be used in medical field and the medical community involved in the application of radiopharmaceuticals for the cure of cancer, that a new technology based on Compact Neutron Generators (CNG) is in a R&D phase and will allow to produce the necessary quantity of radioisotopes for clinical and research purpose. This will be essential in treatment advanced metastatic cancer as for instance the metastatic Castration – Resistant Prostate Cancer.

Feasibility Study on the nIORT® Adjuvant Treatment of Glioblastoma Multiforme through the Irradiation Field of Fast Neutrons Produced by a Compact Generator

The glioblastoma multiforme (GBM) is the most malignant glial brain tumour with average survival time of 6÷18 months. Emerging evidence suggests that GBM cells appears to reprogram their tumour microenvironment, which is a highly heterogeneous and complex system, so that an efficient GBM radiotherapy (RT) should cover both the cells of the GBM and those of its microenvironment. Relying on a 5-year collaborative research study on the intra-operative radiotherapy (IORT) with fast neutrons - the so-called neutron-IORT (nIORT®) technique - the authors think that this objective could be achieved by using an ionizing radiation field of fast neutrons that behave in the biological tissues as a “foam field” hitting both the GBM cancer cells and the neighbouring microenvironment. The nIORT® research activities - conducted by TheranostiCentre Srl, Berkion Technology LLC and ENEA - led to the fabrication of the first prototype of a compact neutron generator (CNG) that, through the deuterium-deuterium fusion reaction, produces neutrons of 2.45 MeV energy having: i) high linear energy transfer; ii) very high relative biological effectiveness (RBE), about 16 times higher than X-rays (and electrons) used in standard RT and IORT treatments; iii) reduced oxygen enhancement ratio, and hence resulting be very effective in cancer cells necrosis and apoptosis. The CNG is self-shielded, limited in size and weight (~120 kg) and manageable remotely by a robotic arm. A new prototype equipped by a cylindrical applicator to be inserted in the surgical cavities is currently under construction, with some technical advancements making possible its installation in an operating room dedicated to nIORT® treatments without posing any safety and environmental concern. In this article the nIORT® potentiality was investigated in the view of the GBM treatment, but the study is however generalisable for the neutron irradiation of other brain cancer pathologies. Accurate Monte Carlo simulations, modelling the CNG equipped with a couple of cylindrical applicators of 4 and 6 cm in diameter inserted in the brain surgical cavity after craniotomy, demonstrated that the nIORT® device operated at 100 kV-10 mA DC supplies a neutron flux ~108 cm-2 s-1 and can deliver equivalent dose rates ~5 Gy (RBE)/min in the centre of the tumour bed. Thus, it could administer the clinical endpoints foreseen by the standard IORT protocols (~10-20 Gy (RBE)) in treatment times of few minutes, by providing a sort of “switching on and off neutron brachytherapy tool” without using needles of radioisotopes (e.g., 252Cf). The near isotropic neutron emission allows to irradiate the tumour bed margins, normally filled by potential quiescent cancer cells, with lower (but still significant) dose levels. This should improve the local control of the tumour through the reduction of local recurrences and metastasis in the tumour microenvironment, and at the same time to avoid adverse effects of the administered neutron radiation field on the surrounding brain central nervous system. Also, the rapid decrease in tissue depth of the dose gradient (within few centimetres) should avoid any adverse effect on normal brain tissues and the neighbouring organs.

Proposal for a compact neutron generator based on a negative deuterium ion beam

Interest in high intensity generators of neutrons for basic and applied science has been growing, and thus the demand for an economical neutron generator has been growing. A major driver for the development of high intensity neutron generators are studies of neutron disturbance in integrated circuits, for which a compact generator that can be easily accommodated in an ordinary size lab would be highly desirable. We have investigated possible designs for neutron generators based on the D-D fusion reaction, which produce direction dependent mono-energetic neutrons with carry-off energy larger than 2.45 MeV. Specifically, we find a negative deuterium ion beam most attractive for this application, and plan to construct such a system with a negative deuterium ion beam of 200 keV energy and 100 mA current as a prototype of this concept.

Calculating the maximum possible yield for a typical pyroelectric neutron generator

Pyroelectric crystals are heated/cooled to supply D-D/D-T fusion for the purpose of neutron generation. Enhancing the pyroelectric neutron generators (PNG) yield is one of the main goals pursued by most of the previously developed techniques/models. Here, the maximum possible neutron yield of a PNG is calculated in which a widely-used pyroelectric crystal (i.e., LiTaO3 with a diameter of 3 cm and height of 1 cm) is applied. This calculation is performed by a simulation procedure including: (1) computation of the PNG potential/current for neutron generation based on new modifications (2) simulation of the deuterium ions acceleration into the target during a thermal cycle (3) simulation of the D-D fusion interaction using the Geant4 toolkit. The results show that the maximum yield of the PNG in the ideal conditions is about 6.4× 106 neutrons per cycle. This study provides a useful approach for determining the upper limit of the expected efficiency for typical PNGs and other compact neutron generators.

Progress in commissioning a neutron/X-ray radiography and tomography systems at IAEA NSIL

The Nuclear Science and Instrumentation Laboratory (NSIL) is currently establishing a Neutron Science Facility (NSF) based on two compact neutron generators: Deuterium-Deuterium (DD), resulting in 2.45 MeV neutrons, and Deuterium-Tritium (DT), resulting in 14.1 MeV neutrons, with maximum source intensities up to 5 × 106 n/s and 4 × 108 n/s over 4π, respectively. Neutron/X-ray radiography and tomography are two of the applications the NSF will be equipped with. In this paper, we report the state of the radiography and tomography system, and the neutron/X-ray radiography and tomography experiments we performed. Good radiographs and tomographs are obtained with X-ray. The spatial resolution of the X-ray radiography system is measured to be about 0.1 mm. The thermal neutron radiographs and fast neutron radiographs have proved that the DD neutron generator will be beneficial to demonstrate neutron radiography capabilities for educational purposes. Additionally, the detail of the collimator optimization of the DD neutron radiography was presented.

Thermophysical Parameter Estimation of a Neutron Source Based on the Action of Broadband Radiation on a Cylindrical Target

This paper is devoted to the computational and theoretical assessment of the physical and technical characteristics of the effect of intense energy fluxes on the target in the magneto-inertial method of plasma confinement. The results of calculating the effect of intense broadband radiation fluxes on a single-layer cylindrical target are presented. Based on these calculations, the possibility of creating compact neutron generators is estimated. The processes of radiation transfer, thermal and electromagnetic processes, including the coefficients of thermal conductivity of electrons and ions and suprathermal electrons, are studied. A new algorithm for the numerical solution of the hyperbolic and parabolic (thermal) parts of the plasma dynamics equations is briefly described.

Demonstration of an intense lithium beam for forward-directed pulsed neutron generation

As an alternative to research nuclear reactors, a compact accelerator-driven neutron generator that uses a lithium beam driver could be a promising candidate since it produces almost no undesired radiation. However, providing an intense lithium-ion beam has been difficult, and it has been thought that the practical application of such a device would be impossible. The most critical problem of insufficient ion fluxes has been solved by applying a direct plasma injection scheme. In this scheme, a pulsed high-density plasma from a metallic lithium foil generated by laser ablation is efficiently injected and accelerated by a radio-frequency quadrupole linear accelerator (RFQ linac). We have obtained a peak beam current of 35 mA accelerated to 1.43 MeV, which is two orders of magnitude higher than a conventional injector and accelerator system can deliver.

Beam dynamics of the project DARIA RFQ

The project DARIA (neutron source dedicated to applied research and industrial applications) directed to the development of compact neutron generators for universities, scientific centers and industry. In framework of the DARIA project, the 3 MeV, 162.5 MHz and 100mA pulse proton Radio Frequency Quadrupole (RFQ) is under development at National Research Centre "Kurchatov Institute". In this article the main aspects of the beam dynamics design of this RFQ are described, namely the choice of RFQ parameters, the optimization of the transport and the transmission. Results of beam dynamic simulation in RFQ are presented.