Li Target Research Articles

Engineering Design of Contact-Type Liquid Level Sensor for Measuring Thickness Variation of Liquid Lithium Jet in IFMIF/EVEDA Lithium Test Loop

In the Engineering Validation and Engineering Design Activities (EVEDA) on the International Fusion Materials Irradiation Facility (IFMIF), hydraulic stability of a liquid Li jet simulating the IFMIF Li target is planned to be validated in the EVEDA Li Test Loop (ELTL). This paper presents the engineering design of a contact-type liquid level sensor for use in ELTL. The sensor is going to be utilized to measure variation of jet thickness in the validation test on hydraulic stability of the Li jet, which is one of the major key tests to be performed in ELTL. A fundamental requirement for the engineering specification of the sensor is to ensure the position accuracy of the measurement probe against the pressure load of approximately 0.1 MPa between the inside and the outside of the test chamber. The calculation result on structural strength of the sensor with a Nastran code showed that the maximum displacement was 0.65 mm and that the sensor has adequate strength against the pressure load. The calculation result on the sensor temperature with an ABAQUS code showed that the probe tip’s temperature can be heated up to approximately the operation temperature with no heaters installed on the sensor.

In-situ vacuum deposition technique of lithium on neutron production target for BNCT

For the purpose of avoiding the radiation blistering of the lithium target for neutron production in BNCT (Boron Neutron Capture Therapy) device, trilaminar Li target, of which palladium thin layer was inserted between cupper substrate and Li layer, was newly designed. In-situ vacuum deposition and electrolytic coating techniques were applied to validate the method of fabrication of the Li/Pd/Cu target, and the layered structures of the synthesized target were characterized. In-situ vacuum re-deposition technique was also established for repairing and maintenance for lithium target damaged. Following conclusions were derived;(1) Uniform lithium layers with the thickness from 1.6nm to a few hundreds nanometer were formed on Pd/Cu multilayer surface by in situ vacuum deposition technique using metallic lithium as a source material.(2) Re-deposition of lithium layer on Li surface can be achieved by in situ vacuum deposition technique.(3) Small amount of water and carbonate was observed on the top surface of Li. But the thickness of the adsorbed layer was less than monolayer, which will not affect the quality of the Li target.(4) The formation of Pd-Li alloy layer was observed at the Pd and Li interface. The alloy layer would contribute to the stability of the Li layer.

First observation of the hyper superheavy hydrogen

Three candidate events of the neutron-rich hypernucleus 6{\Lambda}H were uniquely identified in the FINUDA experiment at DA{\Phi}NE, Frascati, by observing {\pi}+ mesons from the (K-stop,{\pi}+) production reaction on 6Li targets, in coincidence with {\pi}-mesons from 6{\Lambda}H \rightarrow 6He+{\pi}- weak decay. Details of the experiment and the analysis of its data are reported, leading to an estimate of (2.9\pm2.0)\cdot10-6/K- stop for the 6{\Lambda}H production rate times the two-body {\pi}- weak decay branching ratio. The 6{\Lambda}H binding energy with respect to 5H + {\Lambda} was determined jointly from production and decay to be B{\Lambda} = (4.0 \pm 1.1) MeV, assuming that 5H is unbound with respect to 3H + 2n by 1.7 MeV. The binding energy determined from production is higher, in each one of the three events, than that determined from decay, with a difference of (0.98 \pm 0.74) MeV here assigned to the 0+g.s. \rightarrow 1+ excitation. The consequences of this assignment to {\Lambda} hypernuclear dynamics are briefly discussed.

Cross-section measurements of neutron threshold reactions in various materials

Abstract As members of international collaboration “Energy and Transmutation of radioactive Waste” we routinely use (n,xn) threshold reactions in various materials to measure high energy neutron flux from spallation reactions. The cross–sections of many reactions important for our activation detectors are missing. To improve situation, we studied the neutron cross-sections using different quasi-monoenergetic neutron sources based on proton reaction on 7Li target. The measurements were performed in Nuclear Physics Institute of the Academy of Sciences of the Czech Republic in Řež near Prague and in The Svedberg Laboratory in Uppsala (Sweden). We used neutron energies 17, 22, 30 and 35 MeV from the quasi-monoenergetic neutron source in Řež and neutron energies 22, 47 and 94 MeV in Uppsala. The last experiment was carried out in February 2010 in Uppsala using neutron energies 59, 66, 72 and 89 MeV. The study of neutron threshold reactions in yttrium was performed first time during this irradiation. We have developed procedure for the subtraction of contribution of the background neutrons. We studied various materials in the form of thin foils and observed good agreement with the data in EXFOR database and also with the calculations performed in deterministic code TALYS. Many cross-sections were measured in the energy regions where no experimental data are available so far.

IFMIF/EVEDA lithium test loop: design and fabrication technology of target assembly as a key component

The engineering validation and engineering design activity (EVEDA) for the International Fusion Materials Irradiation Facility (IFMIF) is proceeding as one of the ITER broader approach activities. In the concept of the IFMIF, two 40 MeV deuteron beams are injected into a liquid Li stream (Li target) flowing at a velocity of 15 m s−1. The EVEDA Li test loop (ELTL) is aimed at validating the hydraulic stability of the Li target at a velocity up to 20 m s−1 under a vacuum condition of 10−3 Pa as the most important issue. Construction of the ELTL, which is the largest liquid metal loop possessing 5.0 m3 Li for the fusion research ever, was completed in the O-arai Research & Development Center in the Japan Atomic Energy Agency on 22 November 2010. This paper presents the design and fabrication technology of a target assembly called integrated target assembly, in which the Li target is produced by a contraction nozzle along a concave channel. There are two concepts regarding the target assembly: the integrated target assembly and the bayonet target assembly. Both target assemblies are outlined in this paper, and then the newly proposed design of the integrated target assembly for the ELTL and its fabrication technology are given. The integrated target assembly was processed by a five-axis milling machine and the processing accuracy was measured by 3D measurement tools. Finally, methods applied for the validation of the stability of the Li target are introduced in this paper.

Formation of heavy-meson bound states by two-nucleon pick-up reactions

We develop a model to evaluate the formation rate of the heavy mesic nuclei in the two nucleon pick-up reactions, and apply it to the $^6$Li target cases for the formation of heavy meson-$\alpha$ bound states, as examples. The existence of the quasi-deuteron in the target nucleus is assumed in this model. It is found that the mesic nuclei formation in the recoilless kinematics is possible even for heavier mesons than nucleon in the two nucleon pick-up reactions. We find the formation rate of the meson-$\alpha$ bound states can be around half of the elementary cross sections at the recoilless kinematics with small distortions.

Screening Potential of 6Li(d,α)4He and 7Li(p,α)4He Reactions in Liquid Lithium

In order to investigate the screening effect of a nuclear reaction in a liquid metal environment, thick-target yields of the 6 Li(d,α) 4 He and 7 Li(p,α) 4 He reactions were measured using a liquid Li target for incident energies between 22.5 and 70 keV. The modified S ( E ) factor [ S * ( E )] for the liquid Li environment was deduced by dividing the measured yield by the energy integration of the penetration factor divided by the stopping power. It was shown that S * ( E ) for the liquid environment is considerably larger than that for the atomic/molecular environment for both reactions. The difference in the screening energy between the two environments was deduced to be Δ U = 235 ±63 ( 6 Li+d) and 140±82 eV ( 7 Li+p), although the screening energy for liquid Li has a large uncertainty with U liq ∼486–776 ( 6 Li+d) and 324–637 eV ( 7 Li+p) owing to the uncertainty of the astrophysical bare S ( E ) factors. This difference in the screening energy should be considered in such a way that, in liquid Li met...

Present status of Japanese tasks for lithium target facility under IFMIF/EVEDA

In IFMIF/EVEDA, tasks for lithium target system consist of 5 validation tasks (LF1-5) and a design task (LF6), and are shared by Japan and Europe. Japan is covering LF1, LF2, LF4, LF5 and LF6, and JAEA as an Implementing Agency is organizing these tasks. Japanese universities contribute these tasks. The purpose of LF1 task is to construct and operate EVEDA Li test loop (ELTL) with diagnostics and purification systems for the validation of Li target facility. ELTL will be constructed at the end of February in 2011 and the operation will be started at the summer in 2011. LF2 and LF4 are basic research for the diagnostics and purification system, respectively. And LF2 and LF4 have also contributed the construction of the ELTL (LF1). LF5 is focusing on the remote handling for the replacement of the target assembly. Major deliverable of LF6 is finally engineering design report, which is assembled with all validation tasks, and this activity will be gradually enhanced to the end of IFMIF/EVEDA.

Recent results from COMPASS

The COMPASS experiment at CERN is studying since 2002 the spin structure of the nucleon, both for longitudinal and transverse nucleon spin. In the first case, the measurements of DIS and SIDIS asymmetries, including also high-pT hadron production and D0 mesons, allow to access the nucleon longitudinal PDFs, their first moments and the gluon polarization. The LO analysis, performed by COMPASS have shown that Δg/g is small around xg ≃ 0.1, and its first moment should not be larger than 0.2 – 0.3 in absolute value. Transverse spin effects have rised large interest in the last 10 years and the measurements performed have shown evidence for new phenomena, associated with transverse momentum dependent distribution and fragmentation functions. Collins and Sivers asymmetries obtained by COMPASS on a proton target, together with the latest results on unpolarized modulations on the deuterated 6Li target will be shown here.

Hydraulic analysis on effects of back-plate deformation upon stability of high-speed free-surface lithium flow for IFMIF target design

For engineering design of liquid lithium (Li) target of the International Fusion Materials Irradiation Facility (IFMIF), two-dimensional hydraulic analysis was performed using code FLUENT. The analysis clarified effects of smooth deformation at the center of the back-plate part of the flow channel upon velocity and pressure in the high-speed free-surface Li flow. Convex deformations caused decrease in jet thickness and thus increase in velocity and decrease in pressure. Convex deformations caused vice versa. Acceptable limit of the back-plate deformation to avoid Li boiling in IFMIF target was 1.0 mm for the convex deformation and 3.0 mm for the concave deformation. Spatial range of the effects of the deformation was localized around deformation as far as no boiling.

PHOTOPRODUCTION OF MESONS OFF LIGHT NUCLEI

During the last few years photoproduction of mesons off light target nuclei (2 H , 3 He , 7 Li ) has been systematically studied at the tagged photon beams of the Bonn ELSA accelerator and the Mainz MAMI accelerator. The experiments used the combined Crystal Barrel/TAPS setup in Bonn and the Crystal Ball/TAPS setup in Mainz. Most measurements investigated meson photoproduction off the neutron for many different reaction channels in order to establish the iso-spin structure of electromagnetic resonance couplings. This project used mostly deuteron targets. The measurements with the He and Li targets aimed at the search for η-mesic nuclei and hadron in-medium properties.

Wave period of free-surface waves on high-speed liquid lithium jet for IFMIF target

Wave period of free-surface waves on a high-speed liquid lithium (Li) jet has been experimentally studied for validation of a Li target of the International Fusion Materials Irradiation Facility (IFMIF), since stability of the jet is of crucial importance for generating high neutron fluence and for the safety of IFMIF itself. The experiments were conducted at a Li loop in Osaka University. In this loop, a plane Li wall jet of 70 mm in width and 10 mm in depth simulating the IFMIF Li target can be tested at the velocities of up to 15 m/s at the operation temperature of 573 K. In measurement of the wave period, the contact type liquid level sensor was used. As a result, probability density distribution of the wave period was found to be very similar to the log-normal distribution. From our previous and the present results, it is concluded that random wave property developed for the ocean waves can apply to the free-surface waves on the Li jet, irrespective of difference in the materials properties of Li and water.

An experimental study of the microdosimetric response of a graphite walled proportional counter in low energy neutron fields

Abstract This study describes the measurement of lineal energy spectra carried out with a graphite walled proportional counter (GPC) simulating 1 μm tissue equivalent (TE) site diameter in low energy neutron fields generated by employing the McMaster University 1.25 MV double stage Tandetron accelerator. Experiments were carried out for neutron beams of mean energies extending from 34 to 354 keV in direct neutron beams from the 7 Li target using proton beam energies ranging from 1.89 to 2.56 MeV. We have observed a continuously increasing trend in microdosimetric averages, y ¯ F and y ¯ D , and the ICRP 60 based quality factor, Q , with an increase in neutron energy. It is interesting to note that standard tissue equivalent proportional counters (TEPCs) give rise to a similar trend for these microdosimetric quantities of interest in the same energy range. Quantitatively, these quantities are also comparable to those obtained with standard TEPCs. This implies that at the microdosimetric level in the neutron energy range we employed in this study, the pattern of average energy deposited by ‘starter’ and ‘insider’ proton recoil events in the gas is similar to those generated cumulatively by ‘crosser’ and ‘stopper’ events originating from the counter wall plus ‘starter’ and ‘insider’ recoil events originating in the sensitive volume of a TEPC. This suggests that the average energy deposition per event in the wall of a TEPC counter is the same as in the counting gas itself, which confirms the similarity of the composition and mass stopping power of two media, i.e., TE wall and TE gas, used in neutron dosimetric measurements.

ICONE19-43608 DIAGNOSTICS OF HIGH-SPEED LIQUID LITHIUM JET FOR IFMIF/EVEDA LITHIUM TEST LOOP

Regarding R&Ds on the International Fusion Materials Irradiation Facility (IFMIF), hydraulic stability of the liquid Li jet simulating the IFMIF Li target is planned to be validated using EVEDA Li Test Loop (ELTL). IFMIF is an accelerator-based deuteron-lithium (Li) neutron source for research and development of fusion reactor materials. The stable Li target is required in IFMIF to maintain the quality of the neutron fluence and integrity of the Li target itself. This paper presents diagnostics of the Li jet to be implemented in validation tests of the jet stability in ELTL, and those specifications and methodologies are introduced. In the tests, the following physical parameters need to be measured; thickness of the jet; surface structure (height, length/width and frequency of free-surface waves); local flow velocity at the free surface; and Li evaporation rate. With regard to measurement of jet thickness and the surface wave height, a contact-type liquid level sensor is to be used. As for measurement of wave velocity and visual understanding of detailed free-surface structure, a high-speed video camera is to be leveraged. With respect to Li evaporation measurement, weight change of specimens installed near the free surface and frequency change of a crystal quartz are utilized.

Design and Construction of IFMIF/EVEDA Lithium Test Loop

Abstract The International Fusion Materials Irradiation Facility (IFMIF) is a D+–Li neutron source aimed at producing an intense high energy neutron flux (2 MW/m2) for testing candidate fusion reactor materials. Under Broader Approach activities, Engineering Validation and Engineering Design Activities (EVEDAs) of IFMIF started on July 2007. Regarding the lithium (Li) target facility, design, construction, and tests of EVEDA Li test loop (ELTL) is a major Japanese activity. The detail design of the loop was started since early 2009. Construction of the loop was started at the middle of 2009, and completion is scheduled at the end of February 2011. This paper focuses on the design of the loop configuration and the major components. ELTL was designed to consist of two major Li loops, which are a main loop and a purification loop including an impurity monitoring loop. The main loop equips a target assembly which produces a high-speed free-surface Li flow to test the flow stability as the D+ beam target. The maximum flow rate of an electromagnetic pump in the main loop was set to 3000 l/min, so that flow velocity in the target assembly is 20 m/s at the maximum. Regarding the purification loop, a cold trap and two hot traps and impurity monitors are installed in order to purify and monitor impurities in Li. The configuration of these components in addition to the specification and configuration of the whole loop is presented.

Multi-peak structure of the ion current in laser produced plasma

The experimental multi-peak structure of the transient ion current recorded by a charge-collector probe during the laser produced plasma expansion is reported for Sn and Li targets, and various focusing conditions and laser beam energies. Using a simple hydrodynamic model, the numerical simulations can reproduce well this type of behavior. Theoretically, a fractal hydrodynamic model is developed in a non-differentiable space-time. The solutions of Gaussian wave packet and ‘bouncing’ Gaussian wave packets types are found to explain the plasma expansion and to give a reasonable mathematical description of plasma splitting process.

State-selective charge exchange from H(1s), H(n = 2), Li and Na targets by very highly charged ions

In order to provide information for charge exchange spectroscopy diagnostics in new, high temperature tokamak plasmas, n-level state-selective electron capture cross sections are presented for very highly charged ions with charge states q ⩾ 10. Fully stripped ions with charges of 10+, 18+, 26+, 54+ and 92+ are considered in order to provide scaling information over a broad range. The H(1s) and H(n = 2) targets are evaluated at 1, 10 and 100 keV/amu, i.e. plasma core temperatures to those encountered during neutral beam heating. For use in pellet diagnostics, cross sections are given for Li and Na targets at 10 keV/amu. These latter targets also provide a means to experimentally test the accuracy of the H(n = 2) results since they are pseudo-one-electron atoms with ionization energies close to that of excited hydrogen.

Few-body systems with [formula omitted] and −2

The structure of the T = 1 iso-triplet hypernuclei, He Λ 7 , Li Λ 7 and Be Λ 7 within the framework of an α + Λ + N + N four-body cluster model is studied. A phenomenological Λ N charge symmetry breaking (CSB) interaction is introduced. The Λ binding energy of the ground state in He Λ 7 is predicted to be 5.16 ( 5.36 ) MeV with(without) the CSB interaction. The five-body cluster model calculation of α α n Λ Λ for Be Λ Λ 11 , which has been observed as Hida event, is performed. The calculated B Λ Λ is 18.23 MeV , which is less bound by about 2 MeV than the experimental data. The structure calculation in Li Ξ − 7 and Li Ξ − 10 are performed within the framework of α Ξ − n n and α α Ξ − n four-body model. Li Ξ − 7 and Li Ξ − 10 are predicted to have bound states. We propose to observe the bound states in future ( K − , K + ) experiments using 7Li and 10B targets in addition to the standard 12C target.

Development of measurement technique for surface waves on high-speed liquid lithium jet for IFMIF target

This paper reports a measurement technique for surface waves on a liquid lithium jet, and its experimental results for the purpose of study on a Li target of the International Fusion Materials Irradiation Facility (IFMIF). The statically characteristic of the waves was successfully clarified by a contact-type liquid level detector and an analysis method of the obtained data newly proposed in this paper. The detail procedure of the measurement method is described in this paper. As the results, it was found that the wave distributions in the all jet velocity range up to 15 m/s were conformed each other in normalized form and Rayleigh distribution which is one of popular model to show irregular water waves, and found that the mean wave height increased with increasing of the flow velocity.

The cross-section data from neutron activation experiments on niobium in the NPI p-7Li quasi-monoenergetic neutron field

The reaction of protons on 7 Li target produces the high-energy quasi- monoenergetic neutron spectrum with the tail to lower energies. Proton energies of 19.8, 25.1, 27.6, 30.1, 32.6, 35.0 and 37.4 MeV were used to obtain quasi-monoenergetic neutrons with energies of 18, 21.6, 24.8, 27.6, 30.3, 32.9 and 35.6 MeV, respectively. Nb cross-section data for neutron energies higher than 22.5 MeV do not exist in the literature. Nb is the important material for fusion applications (IFMIF) as well. The variable-energy proton beam of NPI cyclotron is utilized for the production of neutron field using thin lithium target. The carbon backing serves as the beam stopper. The system permits to produce neutron flux density about 109 n/cm2 /s in peak at 30 MeV neutron energy. The niobium foils of 15 mm in diameter and approx. 0.75 g weight were activated. The nuclear spectroscopy methods with HPGe detector technique were used to obtain the activities of produced isotopes. The large set of neutron energies used in the experiment allows us to make the complex study of the cross-section values. The reactions (n,2n), (n,3n), (n,4n), (n,He3), (n,α) and (n,2nα) are studied. The cross-sections data of the (n,4n) and (n,2nα) are obtained for the first time. The cross-sections of (n,2n) and (n,α) reactions for higher neutron energies are strongly influenced by low energy tail of neutron spectra. This effect is discussed. The results are compared with the EAF-2007 library.