Hydride Targets Research Articles

Core design of ma-transmutation fast reactor with zirconium hydride target

The use of zirconium hydride in fast reactors provides excellent MA transmutation performance by neutron moderation with hydrogen. This study has designed an MA transmutation fast reactor loading a ‘target” containing MA-zirconium hydride in the blanket fuel region to maximize the transmutation capability of the core. As the result, the three-region core of the small fast reactor has been designed to adopt the operation of removing the irradiated target from the reactor vessel after temporarily placing in the neutron shielding area during one cycle, and to adopt the method of setting the Pu enrichment of each core fuel to increase neutron leakage to the target. By only changing the target Am/(Zr + Am) ratio to 0.1 ~ 0.3, the three-region core can be used with 2 types; one is the high-amount type with the Am/(Zr + Am) ratio of about 0.25 to be used in the disposal phase in which the amount of stored Am is positively reduced, and the other is the high-ratio type with the Am/(Zr + Am) ratio of about 0.1 to be used in the equilibrium phase in which the amount of stored Am is kept constant. One unit of the high-amount type can transmute Am generated from the spent fuel up to about 10 GWe-LWR without Pu supply from the FBR reprocessing. The three-region core can be designed with excellent core safety characteristics that is the sodium void reactivity is $1.4 or less. In addition, the core can transmute Am and Np in parallel by using Pu, which is not separated Np, as the core fuel in the condition that the Am-Zr hydride target is loaded.

Collisional effects on the electrostatic shock dynamics in thin-foil targets driven by an ultraintense short pulse laser

We numerically investigate the impact of Coulomb collisions on the ion dynamics in high-Z, solid density caesium hydride and copper targets, irradiated by high-intensity (), ultrashort (∼10 fs), circularly polarized laser pulses, using particle-in-cell simulations. Collisions significantly enhance electron heating, thereby strongly increasing the speed of a shock wave launched in the laser-plasma interaction. In the caesium hydride target, collisions between the two ion species heat the protons to ∼100−1000 eV temperatures. However, in contrast to previous work (A E Turrell et al 2015 Nat. Commun. 6 8905), this process happens in the upstream only, due to nearly total proton reflection. This difference is ascribed to distinct models used to treat collisions in dense/cold plasmas. In the case of a copper target, ion reflection can start as a self-amplifying process, bootstrapping itself. Afterwards, collisions between the reflected and upstream ions heat these two populations significantly. When increasing the pulse duration to 60 fs, the shock front more clearly decouples from the laser piston, and so can be studied without direct interference from the laser. The shock wave formed at early times exhibits properties typical of both hydrodynamic and electrostatic shocks, including ion reflection. At late times, the shock is seen to evolve into a hydrodynamic blast wave.

Evidences of accumulation points in cascade regenerative phenomena observed in high voltage dc devices insulated by long vacuum gaps

Localized heating has been observed in unexpected positions on anodic surfaces in a multi-electrode device insulated by vacuum gaps. In double polarity experiments, a counter-intuitive behavior of current-voltage characteristic has also been observed. The phenomena could depend on a cascade effect of charged particles exchanged between electrodes and on a mutual correlation of particle trajectories between electrode surfaces occurring during the high voltage conditioning phase. Attractors regions ascribed to regenerative processes of charged particles between cathode and anode have been identified thanks to numerical simulations The position of the attractors depends only on electrode shape and the ratios of applied voltages. This finding suggests new perspectives in neutrons sources applications, where recurrent impacts of focused high energy hydrogen isotopes take place on solid hydride targets supported by metallic electrodes insulated by vacuum gaps.

Proton acceleration in two-species targets irradiated by an ultra-intense femtosecond laser pulse

This paper presents results of two-dimensional particle-in-cell simulations of proton acceleration at the interactions of a 130 fs, linearly polarized laser pulse of intensity from the range 1021 –1023 W/cm2, predicted for the ELI (Extreme Light Infrastructure) lasers, with thin hydrocarbon (CH) or hydride (ErH3) targets. It is shown that for the targets of the areal density σ > 0.1 mg/cm2 and laser intensities below 1022 W/cm2 a higher efficiency of proton acceleration is achieved for hydride targets. However for the highest, ultra-relativistic laser intensities (~ 1023 W/cm2) considerably higher proton energies and proton beam intensities are achieved for thin (σ ≤ 0.1 mg/cm2) CH targets. In this case, at short distances from the irradiated CH target (< 50 um), the generated proton pulses are very short (< 20 fs), and the proton beam intensities and the proton current densities reach extremely high values, > 1021 W/cm2 and > 1012 A/cm2, respectively, which are much higher than those attainable in conventional accelerators. Such proton beams can open the door for new areas of research in nuclear physics and high energy-density physics as well as can be useful for materials research.

Handling, transfer, storage, and shipping of commercial thin film hydride disk target samples

Thin film hydride (i.e., elements that can react with hydrogen or its isotopes to form a chemical compound) targets are important for many applications, including accelerator research, oil-well logging, cancer research, various neutron devices, nuclear waste assay, process control studies, contraband detection, and for many other novel uses. They are very sensitive to air-oxidation and easily contaminated by improper handling. Targets must be handled very carefully after processing to minimize contamination from physical handling, particulate contamination, and air-exposure, which oxidize sensitive groups IIIB, IVB, and rare earth thin film materials, thus reducing their operating characteristics such as neutron output, and can produce arcing if used in neutron devices. This paper will discuss the development of handling techniques, special vacuum transfer, and shipping containers for thin film hydride target samples from postprocessing to transfer and shipment to a customer. Initial work began at the General Electric Neutron Devices Department, in Largo, FL, in the mid-1970s and was refined at the Los Alamos National Laboratory in Los Alamos, NM, in the mid to late 1990s. Studies were performed to determine the best physical handling techniques, procedures for reducing particulate contamination and for reducing air-exposure and moisture from targets. Items studied were argon or dry nitrogen filled gloveboxes, desiccators, vacuum shipping containers, and a new design loader in a glovebox (in 1993), with an International Organization for Standardization class 4 clean room dry nitrogen environment, with particle and moisture removal and measurements. Test samples of hydride thin films were used to study surface oxide contamination as a function of handling, transfer, and storage times utilizing Auger argon sputter thin film depth profiling techniques. Results have shown that argon filled gloveboxes and dry nitrogen filled desiccators, along with techniques used to minimize target air-exposure, and various vacuum ∼≤1 × 10−3 Torr (1.33 × 10−1 Pa) internal environment shipping containers initially pumped down to ∼1 × 10−7 Torr (1.33 × 10−5 Pa) or less, were adequate to supply customers with thin film hydride targets with surface oxides from 70 to 475 Å or 7.0 to 47.5 nm, as it takes ∼&amp;gt;500 nm to affect neutron output in neutron devices. A special dry nitrogen glovebox controlled clean room loader with a high-efficiency particulate air filter/fan module, and oxygen and water vapor monitors was developed to produce a pristine super clean environment with very low particulate and film surface oxide contamination. The authors demonstrated that we can ship thin film hydride targets of optimum quality adequate for many applications and can supply pristine targets when requested which are in a condition very close to that as processed directly out of a non-air-exposed loader. In addition, our results showed the relative oxidation susceptibility for the four occluder thin films studied: Sc &amp;gt; Zr &amp;gt; Er &amp;gt; Ti.

Generation of proton beams from two-species targets irradiated by a femtosecond laser pulse of ultra-relativistic intensity

AbstractThe paper presents results of two-dimensional particle-in-cell simulations of ion beam acceleration at the interactions of a 130-fs laser pulse of intensity in the range 1021–1023 W/cm2, predicted for the Extreme Light Infrastructure lasers, with thin hydrocarbon (CH) or erbium hydride (ErH3) targets. A special attention is paid to the effect of the laser pulse intensity and polarization (linear, circular) on the proton energy spectrum, the proton beam spatial distribution and the proton pulse shape and intensity. It is shown that for the low laser intensities (~1021 W/cm2) considerably higher proton beam parameters (proton energies, beam intensities) are achieved for the ErH3 target for both polarizations and the effect of polarization on the beam parameters is significant (higher parameters are achieved for the linear polarization). However, for the highest, ultra-relativistic intensities (~1023 W/cm2) higher proton beam parameters are attained for the CH target and the effect of polarization on these parameters is relatively low. In this case, for both polarizations quasi-monoenergetic proton beams are generated from the CH target of the mean proton energy ~2 GeV and $dE_{\rm p} /\bar E_{\rm p} \approx 0.3$ for the linear polarization and $dE_{\rm p} /\bar E_{\rm p} \approx 0.2$ for the circular one. At the highest laser intensities also the proton pulse peak intensities are higher for the CH target and for both polarizations they reach values well above 1021 W/cm2. In the paper, the properties of proton beam generation indicated above are discussed in detail and a physical explanation of the observed effects is done.

Enhanced efficiency of femtosecond laser-driven proton generation from a two-species target with heavy atoms

AbstractUsing two-dimensional particle-in-cell simulations, the properties of a proton beam generated from a thin erbium hydride target irradiated by a 25 fs laser pulse of intensity ranging from 1020 to 1021 W/cm2 are investigated and compared with the features of a proton beam produced from a hydrocarbon (CH) target. It is shown that in case of using the hydride target the mean proton energy and the number of high-energy (&gt;10 MeV) protons as well as the peak proton pulse intensity can be higher by a factor ~10 than the ones obtained from the CH target.

Numerical studies of petawatt laser-driven proton generation from two-species targets using a two-dimensional particle-in-cell code

Laser-driven generation of high-energy ion beams has recently attracted considerable interest due to a variety of potential applications including proton radiography, ICF fast ignition, nuclear physics or hadron therapy. The ion beam parameters depend on both laser pulse and target parameters, and in order to produce the ion beam of properties required for a particular application the laser and target parameters must be carefully selected, and the mechanism of the ion beam generation should be well understood and controlled. Convenient and commonly used tools for studies of the ion acceleration process are particle-in-cell (PIC) codes. Using two-dimensional PIC simulations, the properties of a proton beam generated from a thin erbium hydride (ErH3) target irradiated by a 25fs laser pulse of linear or circular polarization and of intensity ranging from 1020 to 1021 W/cm2 are investigated and compared with the features of a proton beam produced from a hydrocarbon (CH) target. It has been found that using erbium hydride targets instead of hydrocarbon ones creates an opportunity to generate more compact proton beams of higher mean energy, intensity and of better collimation. This is especially true for the linear polarization of the laser beam, for which the mean proton energy, the amount of high energy protons and the intensity of the proton beam generated from the hydride target is by an order of magnitude higher than for the hydrocarbon target. For the circular polarization, the proton beam parameters are lower than those for the linear one, and the effect of target composition on the acceleration process is weaker.

Textured targets of deuterides TiD2, ZrD2, NbD, and CrD2 in experiments to study the pd and dd reaction mechanisms at astrophysical energies

Various methods for depositing thin layers of deuterides (hydrides) TiD2 (TiH2), ZrD2 (ZrH2), NbD (NbH), and CrD2 (CrH2) on stainless steel, copper, and silicon substrates are described. The method for magnetron sputtering of nanolayers of these deuterides (hydrides) with various textures is considered. A technology for producing titanium, zirconium, niobium, and chromium deuteride (hydride) targets is proposed, which will allow the hypothesis of dd and pd reaction enhancement through the channeling of deuterons (protons) in crystals of these deuterides to be unambiguously tested.

Proton beam production by a laser ion source with hydride target.

We studied proton beam production from a laser ion source using hydrogen rich target materials. In general, gas based species are not suitable for laser ion sources since formation of a dense laser target is difficult. In order to achieve reliable operation, we tested hydride targets using a sub nanosecond Q-switched Nd-YAG laser, which may help suppress target material consumption. We detected enough yields of protons from a titanium hydride target without degradation of beam current during the experiment. The combination of a sub nanosecond laser and compressed hydride target may provide stable proton beam.

Numerical simulations of generation of high-energy ion beams driven by a petawatt femtosecond laser

Abstract This contribution presents results of a Particle-in-Cell simulation of ion beam acceleration via the interaction of a petawatt 25 fs laser pulse of high intensity (up to ~1021 W/cm2) with thin hydrocarbon (CH) and erbium hydride (ErH3) targets of equal areal mass density (of 0.6 g/m2). A special attention is paid to the effect that the laser pulse polarization and the material composition of the target have on the maximum ion energies and the number of high energy (&gt;10 MeV) protons. It is shown that both the mean and the maximum ion energies are higher for the linear polarization than for the circular one. A comparison of the maximum proton energies and the total number of protons generated from the CH and ErH3 targets using a linearly polarized beam is presented. For the ErH3 targets the maximum proton energies are higher and they reach 50 MeV for the laser pulse intensity of 1021 W/cm2. The number of protons with energies higher than 10 MeV is an order of magnitude higher for the ErH3 targets than that for the CH targets.

Compact deuterium-tritium neutron generator using a novel field ionization source

Active interrogation using neutrons is an effective method for detecting shielded nuclear material. A lightweight, lunch-box-sized, battery-operated neutron source would enable new concepts of operation in the field. We have developed at-scale components for a highly portable, completely self-contained, pulsed Deuterium-Tritium (DT) neutron source producing 14 MeV neutrons with average yields of 107 n/s. A gated, field ionization ion source using etched electrodes has been developed that produces pulsed ion currents up to 500 nA. A compact Cockcroft-Walton high voltage source is used to accelerate deuterons into a metal hydride target for neutron production. The results of full scale DT tests using the field ionization source are presented.

Effects of outgassing of loader chamber walls on hydriding of thin films for commercial applications

An important aspect of understanding industrial processing is to know the characteristics of the materials used in such processes. A study was performed to determine the effects of hydriding chamber material on the degree of hydriding for the commercial production of thin film hydride targets for various research universities, commercial companies, and government national laboratories. The goal was to increase the degree of hydriding of various thin film hydrides and to study the vacuum environment during air-exposure hydriding. For this purpose, dynamic residual gas analysis during deuterium gas hydride processing was utilized with erbium thin films, employing a special set-up for direct dynamic hydride gas sampling during processing at elevated temperature and full loading gas pressure. Complete process data for (1) a copper–(1.83 wt. %)beryllium wet hydrogen fired passivated (600 °C–1 h) externally heated pipe hydriding chamber are reported. Dynamic residual gas analysis comparisons during hydriding are presented for hydriding chambers made from (2) alumina (99.8 wt. %), (3) copper (with an interior aluminum coating ∼10 k Å thick, and (4) for a stainless-steel air-fired passivated (900 °C–1 h) chamber. Dynamic data with deuterium gas in the chamber at the hydriding temperature (450 °C) showed the presence and growth of water vapor (D2O) and related mixed ion species(H2O+, HDO+, D2O+, and OD+) from hydrogen isotope exchange reactions during the 1 h process time. Peaks at mass-to-charge ratios (i.e., m/e) of 12(C+), 16(CD2+), 17(CHD2+), and 18(CD3+, OD+) increased for approximately the first half hour of a 1 h hydriding process and then approach steady state. Mass-to-charge peaks at 19(HDO+) and 20(D2O+) continue to increase throughout the process cycle. Using the m/e = 20 (D2O+) peak intensity from chamber (1)–Cu(1.83 wt. %)Be as a standard, the peak intensity from chamber (4)—stainless-steel (air-fired) was 7.1× higher, indicating that the surface of stainless-steel had a larger concentration of reactive oxygen and/or water than hydrogen. The (D2O+) peak intensity from chamber (3)—Cu (interior Al coating) was 1.55× larger and chamber (2)—alumina(99.8%) was 1.33× higher than Cu(1.83 wt. %)Be. Thus copper–(1.83 wt. %)beryllium was the best hydriding chamber material studied followed closely by the alumina (99.8 wt. %) chamber. Gas take-up by Er occluder targets processed in Cu(1.83 wt. %)Be hydriding chambers (i.e., gas/metal atomic ratios) correlate with the dynamic RGA data.

Particle-in-cell simulation of acceleration of ions to GeV energies in the interactions of an ultra-intense laser pulse with two-species targets

This contribution presents the results of one-dimensional particle-in-cell simulations of ion acceleration in the interactions of an ultra-intense (IL ∼ 1023 W cm−2) 130 fs laser pulse with thin hydrocarbon (CH) and hydride (CaH2, CsH, ErH3) targets. The influence of laser pulse polarization and target material on the mean ion energy and the ion energy spectrum is examined. It is shown that for circular polarization the ion energy spectra are narrower than those for the linear one and for this polarization protons from both CH and ErH3 targets of the areal mass density below 0.1 mg cm−2 have a very narrow energy spectrum of . However, for ErH3 targets, protons are clearly separated from Er ions and their mean energy equal to 9 GeV is several times higher than those for other studied targets.

Proton extraction by laser ablation of transition metals

A study on the proton beams extraction from a plasma generated by pulsed laser ablation by targets containing transition metals is presented. The targets used were pure disks of titanium and tantalum and disks of TiH2, obtained by compression of TiH2 powder. The plasma was produced by means of a nanosecond excimer KrF laser operating at low irradiance (109–1010W/cm2). The proton and ions emission was analyzed by the time-of-flight technique using a Faraday cup as ion collector. Studies on the produced protons and ions at different laser irradiances from 2 to 15GW/cm2 were performed. The characterization showed that it is possible to obtain good proton fluxes from these targets, up to 1011 proton/pulse. The results obtained are very interesting if compared with those available in literature where proton fluxes per pulse ranging from 108 to 109 by hydride targets were obtained, at the same laser irradiances.

A possibility of miniaturized fusion and fission hybrid reaction core with positive fusion yield

A novel fission–fusion hybrid reactor was proposed, comprising saturating of a fissile actinide core with a mix of deuterium–tritium hydrogen isotopes (U–D–T target), similarly to Hyperion design. Movement of massive, highly charged and short-range fissile fragments was assumed to produce transfer of energy to deuterons at the distances below collision impact parameter for electrons, when the latter are already deflected. The overall bulk of energy transfer was still assumed to be directed to electrons, being argued to experience secondary interactions in dense metallic matrix at a short distance (∼3 × 10 −13 m) from the projectile. The resulting energy dissipation occurs as a continuous shockwave front (as opposed to discrete transfer in environments of lesser densities) producing compression ahead of the projectile and impacting local values of density. The continuity at short distances from the projectile justified hydrodynamic analogy and application of Taylor–Sedov's shockwave theory. At higher local densities in a bow-wave, the probability of high-energy deuteron acceleration was shown to increase in proportion to compression. The transient non-equilibrium equivalents of pressure and temperature may support fusion in the region with volume V over hot zone life-time τ. Both parameters were compared for the U–D–T and benchmark system (accelerator driven deuteron implantation in a non-actinide hydride target) in a dimensionless and hypothesis-free form, canceling the complexities of the mechanism. Based on the dimensionless theoretical prediction, ∼1–2 fusion 14 MeV neutrons per fission are expected to be produced, accompanied by 1–2 photoneutrons and leading to a significantly decreased critical mass. If confirmed experimentally, the proposed system could produce ∼10–20% of its energy output as controlled fusion, be of compact and economical design, environmentally friendly, lead to significant miniaturization of reactor core compatible with high rate of heat exchange. Novel technological applications in robotics, propulsion, sea bed exploration and as a robust energy source were proposed.

Energetic efficiency of laser thermonuclear targets with ablator shells made of beryllium materials: A comparative analysis

The energetic characteristics of the compression and burning of targets with beryllium and beryllium deuteride shells are compared. The characteristics considered include the hydrodynamic efficiency, the efficiency of energy transmission to the thermonuclear fuel, and the gain factor found from numerical simulation using the ‘Diana’ one-dimensional mathematical code. The calculations are carried out for direct-drive cryogenic laser targets with the ablator shells made of beryllium or beryllium deuteride with parameters corresponding to the third harmonic of energy of the neodymium-laser radiation with a pulse energy of 1–3 MJ. It is proved that the gain of beryllium hydride targets can be brought to the level of beryllium targets due to variations in the geometrical parameters of BeD2 targets. It is shown that the fission of BeD2 or BeDT ablators in reactor-scale targets could significantly contribute to the final thermonuclear yield.

Thermodynamic analysis of Np–Zr–H, Am–Zr–H, Pu–Zr–H systems

High-level radioactive wastes generated after reprocessing spent nuclear fuels from nuclear reactors include long-lived and highly toxic radioactive nuclides. Recently, the transmutation method using actinide hydride targets in fast reactor has been proposed to reduce the amount of actinide in nuclear wastes. The burning of Pu using Pu–Zr–H fuel in light water reactor has also been proposed. Given the potential for high-temperature state during routine or extraordinary operating circumstances, accurate knowledge or reliable predictions of materials behaviour under a variety of conditions is required in order to develop safe and effective nuclear handling and remediation technologies. Semi-empirical Miedema and Griessen–Driessen models on the enthalpy of formation coupling with the available experimental entropy information were utilized to estimate the thermodynamic stability of the selected actinide–zirconium hydrides. The calculations showed that at high temperature, stable hydrides might be expected to form for the Np–Zr–H, Am–Zr–H and Pu–Zr–H systems at selected compositions, which can be effectively used for the MA transmutation or plutonium burning.

Hydrogenation properties of ThZr2Hx

High-level radioactive wastes generated after reprocessing spent nuclear ftiels from nuclear reactors include long-lived radioactive nuclides. Recently, the transmutation method using actinide hydride targets has been proposed to reduce the amount of actinide in nuclear wastes. One of the major R&D items to establish the transmutation method is development of the actinide hydride target, which can be stably irradiated in reactors. The actinide hydride targets tend to decompose at high temperature and increase the internal pressure of target element. The study of hydride dissociation is important for development of hydride target. The desorption of hydrogen from ThZr2Hx was studied by Thermo Gravimetry (TG) and Differential Thermal Analysis (DTA). The several major endothermic peaks were observed in DTA curve of ThZr2Hx in temperature range from 900 to 1200K. In this paper, these peaks are discussed in relation to stabilities of particular hydrogen occupying sites in crystal structure of ThZr2Hx.

Short intense hydrogen gas pulses for transport studies in fusion plasmas produced by laser thermal desorption from titanium hydride

The suitability of laser thermal desorption (LTD) from titanium hydride targets for the production of short intense hydrogen gas pulses for diagnostic applications in fusion devices was investigated. A hydrogen yield of 2.2×1018 H2 molecules was achieved with a pulse energy of 11 J on a target spot diameter of 4.5 mm. The duration of the gas puff is closely coupled to the laser pulse length of 1 ms. The production of gas pulses by LTD close to the plasma creates the requirements for investigating very fast transport processes, especially at the high-field side. The hydrogen pulses were contaminated by 2×10−3 Ti atoms/H2 molecule, primarily as a result of evaporation on overheated surface inhomogeneities. Conditioning the surface with giant laser pulses allowed the contamination to be reduced by a factor of 2.