Deuterium Beam Research Articles

Three-dimensional microscopy of deuterium in tungsten

The hydrogen isotope retention in tungsten is an important issue for fusion devices. In this paper we study the possibility of using a μm-focused deuterium beam in order to quantify deuterium distributions in microscopic dimensions. Due to the lack of cross-section data for deuteron–deuteron-scattering (dd-scattering) a validated reference sample is needed. For this purpose we used a 15 μm thick aluminum foil covered by a-C:D-layers that have been deposited in a CD4 plasma discharge from both sides. At the SNAKE facility of the Munich tandem accelerator we already established a three-dimensional microscopy of hydrogen using protons within an energy range between 17 and 25 MeV. Now, we have tested the possibility for deuteron microscopy. As a first application we analyzed a 25 μm foil implanted with 2.0 × 1020 atom cm−2 deuterons.

Computation of Time Energy Gain in D-3He Mixture: Energy Deposited through Deuterium Ignition Beam

The fast ignition approach to ICF consists in first compressing the fuel to high density by a suitable driver and then creating the hot spot required for ignition by means of a second external pulse. If the ignition beam is composed of deuterons, an additional energy is delivered to the target with increased energy gain. Therefore ,in this innovative suggestion ,we consider deuterium beams for fast ignition in D+ 3 Hemixture and solve the dynamical balance equations under the available physical conditions by considering a new average reactivity formula ,then we compute the energy gain in this mixture .Our computational results show that we can get energy gain value larger than 4 at resonant temperature (200keV)of D+ 3 Hemixture. We select D+ 3 Hefuel, because D+3Hereaction is very attractive from a theoretical point of view since it does not produced neutrons. The D+3Hebenefits include full-lifetime materials, reduced radiation damage, less activation ,absence of tritium breeding blankets ,highly efficient direct energy conversion, easier maintenance, proliferation resistance.

THE DESIGN OF A COMPACT RFQ NEUTRON GENERATOR

The output and target lifetime of a conventional electrostatic neutron generator are limited by the voltage stand-off capability and the acceleration of molecular species from the ion source. As an alternative, we suggest that the deuterium beam achievable from a compact high intensity ECR source can be injected directly into a compact RFQ to produce a more efficient compact neutron production system. Only the d+ ions are accelerated by the RFQ, which can also produce much higher output energies than electrostatic systems, resulting in a higher neutron output with a longer target lifetime. The direct injection of the beam makes the system more compact than the multielement, electrostatic systems typically used for extraction of the beam and subsequent transport and matching into the RFQ. We have designed and optimized a combined extraction/matching system for a compact high current deuterium ECR ion source injected into a high frequency RFQ structure, allowing a beam of about 12 mA of d+ ions to be injected at a modest ion source voltage of 25 kV. The end wall of the RFQ resonator serves as the ground electrode for the ion source, resembling DPI (direct plasma injection). For this design, we used the features of the code IGUN to take into account the electrostatic field between the ion source and the RFQ end wall, the stray magnetic field of the ECR source, the defocusing space charge of the low energy deuteron beam, and the rf focusing in the fringe field between the RFQ vanes and the RFQ flange.

Counter-beam thermonuclear fusion

A method of organizing counter beams of deuterium and tritium in a ring with electrified walls is suggested. In such a ring, beams of ions are locked in a potential well the height of which is much larger than the energy of colliding particles. In this instance, the phase volume of the ion beams increases due to multiple scattering. Estimates are made of the probability of thermonuclear reactions under these conditions and of the parameters of a thermonuclear reactor based on this principle. A number of risks and hazards that researchers might expect to encounter on this way are considered.

A thin float glass MRPC for the outer region of CBM-TOF wall

A Multi-gap Resistive Plate Chamber (MRPC) made out of thin float glass is proposed for the outer region of the time of flight (TOF) system for the Compressed Baryonic Matter experiment at FAIR. Usually MRPCs are assembled with ordinary glass plates of 0.5mm or more thickness, but their rate capability is less than the CBM requirement (1.5kHz/cm2). There are two ways to improve the rate capability. The first way is to reduce the bulk resistivity of the glass plates. The second is to reduce the thickness of the glass plates. Tsinghua University has made significant progress in the development of low resistive glass and high rate MRPCs. In this paper we report on three MRPCs produced with float glass plates of 0.7mm, 0.5mm and 0.35mm thickness. Tests with cosmic rays and X-rays were performed at Tsinghua University. The results show that thin float glass MRPCs work well and have the rate capability necessary to meet the demands of the CBM-TOF outer region. Further studies were performed using a continuous 1GeV deuterium beam at the Nuclotron accelerator at the Joint Institute for Nuclear Research (JINR). Time resolution of about 70ps and efficiency higher than 90% were obtained for flux densities up to 3kHz/cm2, exceeding the requirement for the CBM-TOF outer region.

Investigation on development of free-surface structures in turbulent liquid lithium flow

The liquid lithium film thickness facing the Deuterium beam of the International Fusion Material Irradiation Facility (IFMIF) determines the neutron flux to be generated. Hence, apart from its thickness also its spatio-temporal behaviour plays a decisive role in the performance of the target. Two aspects contributing to the free surface shape are the evolution of the viscous wall boundary layer in the nozzle and the development of turbulence downstream the nozzle exit, which are analysed here numerically by means of a fluid dynamic Large Eddy Simulation (LES). The numerical method is validated by experiments conducted at Osaka University with respect to mean and turbulent flow quantities in a broad spectrum of mean flow velocities. Thereby, both a qualitative and a quantitative agreement have been attained identifying different flow regimes and, moreover, allowing for a more refined, realistic IFMIF target prediction performance.

Retention and enrichment of tungsten-containing carbon films under deuterium beam impact

Abstract Retention and enrichment of a model system for mixed layers, tungsten-containing carbon films (a-C:W), were investigated with respect to the interaction with D ions. a-C:W was exposed to a mass-separated, mono-energetic D beam (200 eV/D, 1.2 × 10 15 D cm −2 s −1 ). The W concentration in the films (0–7.5 at.%), the specimen temperature during D beam exposure (300–1300 K) and the fluence ( Φ ) of incident D (10 15 –10 20 D cm −2 ) were varied. Analysis of retention and enrichment were performed by nuclear reaction analysis and Rutherford backscattering spectrometry, respectively. At 300 K and fluences up to 10 19 D cm −2 , the increase of the D inventory with fluence in a-C:W cannot be distinguished from a-C and pyrolytic graphite, e.g., above ∼10 17 D cm −2 the D inventory increases with fluence according to Φ x ( x = 0.1). Above a fluence of 10 19 D cm −2 , however, the D inventory depends strongly on the W concentration. At a fluence of 10 20 D cm −2 the D inventory is increased to the 1.5-fold of the D inventory of pyrolytic graphite for 1% and 2.5% a-C:W and it is decreased to the half value of the D inventory of pyrolytic graphite for 7.5% a-C:W. At temperatures above 300 K, following trends are observed: With increasing temperature, the D inventory increases more strongly with fluence and D reaches depths far beyond the width of the ion range. However, the D inventory does not increase with fluence according to Φ x , especially at fluences above 10 19 D cm −2 .

Calculation of Shinethrough and its Power Density Distribution for EAST NBI

The NBI (Neutral Beam Inject) system of EAST has two deuterium beam lines, in which beam power is 4 MW and energy is 80 keV. To study the neutral beam shinethrough power loss, the physics processes of neutral beam attenuation in plasma are described and simulated by the code ONETWO/NUBEAM. The simulated input plasma parameter forms are tested through curve fitting of measured shinethrough in DIII-D. The power density distribution of shinethrough is obtained by analytical governing expression. The surface temperature rise testing for a copper target is also discussed.

The polarized H and D atomic beam source for ANKE at COSY-Jülich

A polarized atomic beam source was developed for the polarized internal storage-cell gas target at the magnet spectrometer ANKE of COSY-Jülich. The intensities of the beams injected into the storage cell, measured with a compression tube, are 7.5×1016 hydrogen atoms/s (two hyperfine states) and 3.9×1016 deuterium atoms/s (three hyperfine states). For the hydrogen beam the achieved vector polarizations are pz≈±0.92. For the deuterium beam, the obtained combinations of vector and tensor (pzz) polarizations are pz≈±0.90 (with a constant pzz≈+0.86), and pzz=+0.90 or pzz=−1.71 (both with vanishing pz). The paper includes a detailed technical description of the apparatus and of the investigations performed during the development. This source has been very successfully used for single and double polarization measurements at ANKE as well as for studies of the polarization of recombining hydrogen molecules.

Sputtering Effects and Water Formation on an Amorphous Silicate Surface

We studied the formation of deuterated water on an amorphous silicate surface held at low temperature (10 K < T < 40 K). The surface is first characterized by using Ar(+) ion bombardment, and preferential sputtering of oxygen is found. Sputtering creates oxygen vacancies in the surface region that can be filled by deposition of atomic oxygen. The conditions used in the experiment are meant to make it relevant to the study of the initial stages of water formation on dust grains in interstellar space. By changing the D/O ratio of atomic beams of deuterium and oxygen at thermal energy and the temperature of the sample during deposition, we show that the routes to the formation of D2O2 can be untangled and, under certain circumstances, the net yield of D2O2 can be suppressed. The formation efficiency for water and other molecules is then estimated.

Brightness and virtual source size of a supersonic deuterium beam

Supersonic beams have numerous applications in research fields ranging from spectroscopy with nanodroplets to surface science and matter-wave microscopy. Thus, measurement and prediction of their properties is of considerable interest. In this paper we present measurements of the virtual-source size and its brightness, as well as the terminal speed and terminal speed ratio of a supersonic deuterium (D${}_{2}$) beam. The speed distribution data were measured with time-of-flight experiments and Fresnel zone-plate imaging was used to measure virtual source size. The point-spread function of the zone plate was simulated based on the measured wavelength distribution and used to extract the width of the virtual source and its brightness from the focus measurement. The experiments were carried out with a 10-$\ensuremath{\mu}$m-diameter nozzle and a source temperature of ${T}_{0}=310$ K in the pressure range ${p}_{0}=3$--171 bars and for ${T}_{0}=106$ K in the pressure range ${p}_{0}=3$--131 bars. We found that using deuterium as opposed to helium results in a virtual source that is about a factor 2 brighter under similar stagnation conditions. A comparison between the measured data and the predictions from a theoretical model based on the Boltzmann equation, which explicitly include the coupling between translational and rotational degrees of freedom as well as the real-gas properties of D${}_{2}$, resulted in good correspondence for the two different interaction potentials we tried. A careful comparison with the experimental results shows that the potential by Buck et al. [J. Chem. Phys. 78, 4439 (1983)] is moderately better than the Lennard-Jones potential at describing the expansion dynamics.

Experimental investigation of ion cyclotron range of frequencies heating scenarios for ITER's half-field hydrogen phase performed in JET

Two ion cyclotron range of frequencies (ICRF) heating schemes proposed for the half-field operation phase of ITER in hydrogen plasmas—fundamental H majority and second harmonic 3He ICRF heating—were recently investigated in JET. Although the same magnetic field and RF frequencies (f ≈ 42 MHz and f ≈ 52 MHz, respectively) were used, the density and particularly the plasma temperature were lower than those expected in the initial phase of ITER. Unlike for the well-performing H minority heating scheme to be used in 4He plasmas, modest heating efficiencies (η = Pabsorbed/Plaunched < 40%) with dominant electron heating were found in both H plasma scenarios studied, and enhanced plasma–wall interaction manifested by high radiation losses and relatively large impurity content in the plasma was observed. This effect was stronger in the 3He ICRF heating case than in the H majority heating experiments and it was verified that concentrations as high as ∼20% are necessary to observe significant ion heating in this case. The RF acceleration of the heated ions was modest in both cases, although a small fraction of the 3He ions reached about 260 keV in the second harmonic 3He heating experiments when 5 MW of ICRF power was applied. Considerable RF acceleration of deuterium beam ions was also observed in some discharges of the 3He heating experiments (where both the second and third harmonic ion cyclotron resonance layers of the D ions are inside the plasma) whilst it was practically absent in the majority hydrogen heating scenario. While hints of improved RF heating efficiency as a function of the plasma temperature and plasma dilution (with 4He) were confirmed in the H majority case, the 3He concentration was the main handle on the heating efficiency in the second harmonic 3He heating scenario.

Commissioning of the first KSTAR neutral beam injection system and beam experiments

The neutral beam injection (NBI) system was designed to provide plasma heating and current drive for high performance and long pulse operation of the Korean Superconducting Tokamak Advanced Research (KSTAR) device using two co-current beam injection systems. Each neutral beam injection system was designed to inject three beams using three ion sources and each ion source has been designed to deliver more than 2.0MW of deuterium neutral beam power for the 100-keV beam energy. Consequently, the final goal of the KSTAR NBI system aims to inject more than 12MW of deuterium beam power with the two NBI for the long pulse operation of the KSTAR. As an initial step toward the long pulse (∼300s) KSTAR NBI system development, the first neutral beam injection system equipped with one ion source was constructed for the KSTAR 2010 campaign and successfully commissioned. During the KSTAR 2010 campaign, a MW-deuterium neutral beam was successfully injected to the KSTAR plasma with maximum beam energy of 90keV and the L-H transition was observed with neutral beam heating. In recent 2011 campaign, the beam power of 1.5MW is injected with the beam energy of 95keV. With the beam injection, the ion and electron temperatures increased significantly, and increase of the toroidal rotation speed of the plasma was observed as well. This paper describes the design, construction, commissioning results of the first NBI system leading the successful heating experiments carried in the KSTAR 2010 and 2011 campaign and the trial of 300-s long pulse beam extraction.

Performance of 300 s-beam extraction in the KSTAR neutral beam injector

The first neutral beam injector (NBI-1) has been developed for the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. The first long pulse ion source (LPIS-1) has been installed in the NBI-1 for an auxiliary heating and current drive of KSTAR plasmas. The performance of 300 s ion beam extraction in the LPIS-1 was investigated on the KSTAR NBI-1 system, prior to the neutral beam injection for long pulse operation. The ion source consists of a magnetic bucket plasma generator with multi-pole cusp fields and a set of prototype tetrode accelerators with circular-type apertures. The inner volume of the plasma generator and accelerator column in the LPIS-1 is approximately 123 L. The nominal operation requirements for the ion source (IS) were a 100 kV/50 A deuterium beam and a 300 s pulse length. The extraction of ion beams was initiated by the formation of arc plasmas in the LPIS-1, called an arc-beam extraction method. A stable ion beam extraction of the LPIS-1 was achieved with 80 kV/27 A and a beam perveance of 1.19 microperv for a 300 s pulse length. Beam power deposition along the NBI-1 has been measured using water-flow calorimetry (WFC), and the sum of the deposited power on the ion source and beamline components was about 93% of the drained acceleration power (Vacc•Iacc). The beam power deposition was compared to the calculated results of the beam transport with re-ionization (BTR) code.

Deuterium beam acceleration with 3rd harmonic ion cyclotron resonance heating in Joint European Torus: Sawtooth stabilization and Alfvén eigenmodes

Experiments on accelerating NBI-produced deuterium (D) beam ions from their injection energy of ∼110 keV up to the MeV energy range with 3rd harmonic ion cyclotron resonance heating were performed on the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)]. A renewed set of nuclear diagnostics was used for analysing fast D ions during sawtooth stabilization, monster sawtooth crashes, and during excitation of Alfvén eigenmodes (AEs) residing inside the q = 1 radius. The measurements and modeling of the fast ions with the nonlinear HAGIS code [S. D. Pinches et al., Comput. Phys. Commun. 111, 133 (1998)] show that monster sawtooth crashes are strongly facilitated by the AE-induced re-distribution of the fast D ions from inside the q = 1 radius to the plasma edge.

NGEM neutron diagnostic concept for high power deuterium beams

The ITER neutral beam test facility under construction in Padova will host two experimental devices: SPIDER, a 100 kV negative H/D RF source, and MITICA, a full scale, 1 MeV deuterium beam injector. Detection of fusion neutrons will be used as a means to resolve the horizontal beam intensity profile. The neutron detection system will be placed right behind the SPIDER beam dump, as close to the neutron emitting surface as possible thus providing the map of the neutron emission on the beam dump surface. The system uses nGEM neutron detectors. These are Gas Electron Multiplier detectors equipped with a cathode that also serves as neutron-proton converter foil. The cathode is designed to ensure that most of the detected neutrons at a point of the nGEM surface are emitted from the corresponding 40 × 22 mm2 beamlet footprint on the dump front surface. The nGEM readout pads (area 20 × 22 mm2) will record a useful count rate of 5 kHz providing a time resolution of temporal structures in the neutron fluency rate to be measured of better than 1 s. The directional response of the nGEM to neutrons is a key to reducing the scattering contribution to the measured neutron flux. First results achieved using small size nGEM prototypes shows that these detectors own the directionality property and that experimental results are in agreement with MCNP simulation. In addition they have a neutron efficiency detection of about 10−5 and their response scales linearly following the intensity of the neutron flux.

New ion source for KSTAR neutral beam injection system

The neutral beam injection system (NBI-1) of the KSTAR tokamak can accommodate three ion sources; however, it is currently equipped with only one prototype ion source. In the 2010 and 2011 KSTAR campaigns, this ion source supplied deuterium neutral beam power of 0.7-1.6 MW to the KSTAR plasma with a beam energy of 70-100 keV. A new ion source will be prepared for the 2012 KSTAR campaign with a much advanced performance compared with the previous one. The newly designed ion source has a very large transparency (∼56%) without deteriorating the beam optics, which is designed to deliver a 2 MW injection power of deuterium beams at 100 keV. The plasma generator of the ion source is of a horizontally cusped bucket type, and the whole inner wall, except the cathode filaments and plasma grid side, functions as an anode. The accelerator assembly consists of four multi-circular aperture grids made of copper and four electrode flanges made of aluminum alloy. The electrodes are insulated using PEEK. The ion source will be completed and tested in 2011.

A neutron diagnostic for high current deuterium beams

A neutron diagnostic for high current deuterium beams is proposed for installation on the spectral shear interferometry for direct electric field reconstruction (SPIDER, Source for Production of Ion of Deuterium Extracted from RF plasma) test beam facility. The proposed detection system is called Close-contact Neutron Emission Surface Mapping (CNESM). The diagnostic aims at providing the map of the neutron emission on the beam dump surface by placing a detector in close contact, right behind the dump. CNESM uses gas electron multiplier detectors equipped with a cathode that also serves as neutron-proton converter foil. The cathode is made of a thin polythene film and an aluminium film; it is designed for detection of neutrons of energy >2.2 MeV with an incidence angle < 45°. CNESM was designed on the basis of simulations of the different steps from the deuteron beam interaction with the beam dump to the neutron detection in the nGEM. Neutron scattering was simulated with the MCNPX code. CNESM on SPIDER is a first step towards the application of this diagnostic technique to the MITICA beam test facility, where it will be used to resolve the horizontal profile of the beam intensity.

Magnetic filter field dependence of the performance of the RF driven IPP prototype source for negative hydrogen ions

The ITER neutral beam system requires a negative hydrogen ion beam of 48 A with an energy of 0.87 MeV and a negative deuterium beam of 40 A with an energy of 1 MeV. The beam is extracted from a large RF driven ion source with the dimension of 1.9 × 0.9 m2. An important role for the transport of the negative hydrogen ions to the extractor and the suppression of the co-extracted electrons is the magnetic filter field in front of the extractor. For the large ITER source the filter field will be generated by a current of up to 4 kA flowing through the first grid of the extractor. The extrapolation of the results obtained with the small IPP RF prototype source, where the filter field has a different 3D structure as it is generated by permanent magnets, is not straightforward. Furthermore, the filter field is by far not optimized due to the technical constraints of the RF source. Therefore, a frame that surrounds the ion sources and hosts permanent magnets was constructed for a fast and flexible change of the filter field. First results in hydrogen show that a minimum field of 3 mT in front of the extractor is needed for a sufficiently large number of extracted negative hydrogen ions, whereas sufficient co-extracted electron suppression is achieved by a source integrated magnetic field of more than 1.0 mTm.

Design of Neutral Beam-Line of EAST

Neutral beam injector for EAST is designed to deliver deuterium beams with a power of 2 MW to 4 MW at an energy of 50 keV to 80 keV into the plasma with a beam dimension of 12 cm × 48 cm. Considering the beam generation and transmission, a columniform beam-line of Φ 250 cm × 400 cm is designed with a neutralizer, ion dump, calorimeter, bending magnet and cryopanels. The arrangement of the internal elements for the beam-line is reported. A rectangular sleeve coupled to the ion source is employed as the neutralizer. At the downstream of the neutralizer, a dipole magnet separates the residual ions from the beam passage with a reflection radius of 42 cm for the full energy particles. The calorimeter and the ion dump serve as high heat flux components, which will work as thermal inertia targets in the first phase of operation.