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The IAEA has proposed a coordinated research program to address tritium retention and release in fusion reactor plasma facing components. This program will address materials which are mainly of interest to the design and construction of ITER, namely beryllium, carbon based materials and medium and high-Z metals, e.g. tungsten, vanadium and molybdenum, but will not be limited to these materials. Experimental data are needed for: recycling models, tritium inventory estimates, tritium permeation calculations and hydrogen embrittlement characterization. The ultimate use of the data would be to influence the formation of models for use by fusion reactor designers. Judicious material choices must be made by the designers and accurate predictive codes are required in order to make these choices. The proposed coordinated research program will provide a forum for discussions between experimentalists, theoreticians, modelers and reactor designers, provide financial support for relevant research projects and collect and evaluate experimental and theoretical data. This paper briefly reviews existing data, addresses the data gaps and points out experiments designed to obtain the needed data. 18 refs., 3 figs., 1 tab.

An overview of recent AFT (Advanced Toroidal Facility) experimental results and program plans is presented, with emphasis on the role of magnetic configuration controls in transport studies. The ATF operating space is bounded by a density limit that effectively sets a limit on the energy confinement time tau /sub E/. Although this limit is not solely due to impurities, it has recently been raised by improved cleanliness following titanium gettering. This has led to collapse-free neutral beam injection discharges with global tau /sub E/ approximately=16 ms. Preliminary experiments show that stored energy and bootstrap current are sensitive to details of the magnetic configuration. >

The four major processes involved in hydrogen retention in graphite are reviewed. These processes are saturation of the near-surface region, diffusion on surface-connected porosity, intragranular diffusion, and erosion of carbon with concomitant formation of codeposited hydrogen-carbon films. It is suggested that in the retention of tritium in a fusion experiment the fourth process will dominate; therefore, from that point of view, it is the most important. To address the question of plasma fuel purity, more data are needed on ion-induced release of hydrogen isotopes by hydrogen isotopes and by heavier ions (e.g. carbon and oxygen) as a function of temperature. >

The Electron Cyclotron Heating (ECH) waveguide transmission line, which is used to launch microwave power into the Advanced Toroidal Facility (ATF) plasma confinement experiment, was studied to determine the need for pumping along its length. Several constraints are imposed on the system; the two main constraints are: (1) gas released to the plasma device and (2) the maximum pressure allowed in the waveguide before gas breakdown occurs. The computer program Vacuum System Design-II was used to model the various vacuum components of the existing systems and to determine the gas flow vs. pressure. In addition, outgassing and a constant leak were used to realistically model the gas flow characteristics of the complete system. Pumping must be accomplished via small perforations in the waveguide wall to minimize microwave leakage and maintain the mode purity of the waves. Because the diameter of the perforations must be smaller than the screen thickness to prevent microwave power loss, each perforation was modeled as a long tube. The conductance, of this screen was found to reduce (about 30%) the effectiveness of the pump. In addition, the waveguide presents a significant reduction in the system conductance thereby increasing the pressure difference between the pump and the end of the waveguide. Several cases were run using various waveguide lengths and component configurations. Results of these cases are presented and conclusions made.

A new experimental technique has been developed to measure excitation functions for the 9Be(p, p) reaction. This technique uses thick targets and applies the elastic backscattering method. The angular distribution was measured for scattering angles from 142° to 165° in the proton energy region between 2300 and 2700 eV. Elastic scattering data were analyzed and fitted in terms of a combination of Breit-Wigner resonant cross sections and a constant background. The differential cross-section measurements were compared where possible to previous data using thin targets. Analysis of the present data indicates that the scattering is probably not s-wave but a mixture of p- and d-wave. The experimental technique is simple in practice and very time efficient. It can be used to make absolute measurements of the nuclear reaction or elastic scattering cross sections for many other projectile-target combinations.

The total erosion yields of 304 stainless steel by low energy hydrogen and deuterium have been determined by 4He ion backscattering spectroscopy at energies ranging from 0.33 to 9.0 keV. This experimental method determines the number of atoms removed by sputtering by measuring the change in depth of implanted Xe marker atoms. Data for 304 stainless steel are compared with the extensive published data obtained using the weight loss technique. The Xe marker method is used to make the first measurements of deuterium erosion on polycrystalline graphite. Deuterium erosion measurements of thermally-prepared oxide layers on Be were also made using 4He backscattering spectroscopy to determine directly the number of removed atoms. These new data for the sputtering yields of deuterium on carbon and BeO range from 0.016 to 0.052 atoms/ ion. A previously proposed semi-empirical curve derived from theory and fitted to existing physical sputtering data fits the stainless steel data quite well, but much of the existing carbon sputtering data using hydrogen and all of the results obtained here are substantially greater than predicted using the semi-empirical theory.

The coating of the first wall of a fusion reactor must withstand an intense neutron flux, the impact of energetic charged and neutral particles, and photons, all of which escape from the plasma. Penetration of material eroded from the first-wall coating into the plasma will have a detrimental effect on the plasma stability and energy balance. Therefore material selection for the first-wall coating of a fusion reactor represents one of the critical problem areas for the achievement of fusion power. Theoretical and experimental studies which have been conducted on the many facets of the problem are reviewed with special emphasis placed on the more critical aspects. Possible directions of future research in this area are outlined.

A review of particle-solid processes pertinent to modelling plasma-wall interactions is presented, and sets of recommended data are given. Analytic formulas are used where possible; otherwise, data are presented in the form of tables and graphs. The incident particles considered are e−, H, D, T, He, C, O, and selfions. The materials include the metals aluminum, beryllium, copper, molybdenum, stainless steel, titanium, and tungsten and the nonmetals carbon and TiC. The processes covered are light ion reflection, hydrogen and helium trapping and detrapping, desorption, evaporation, sputtering, chemical effects in sputtering, blistering caused by implantation of helium and hydrogen, secondary electron emission by electrons and particles, and arcing.

The behavior of deuterium and helium implanted near room temperature at 8 keV into prism plane oriented graphite was studied as a function of implantation fluence and post-anneal temperature. Depth profiles of the implanted species were measured by proton backscattering. Quantitative thermal desorption measurements were performed to study the species emitted from the sample during ramp heating to 950/sup 0/C. A summary of the results follows: (1) 100% trapping was observed for D implants up to fluence of 10/sup 18/ D/cm/sup 2/. (2) The measured mean ranges and full widths for D implants agreed with previous measurements but exceed the calculated ..delta..Rp for fluences up to 10/sup 18/ D/cm/sup 2/; above this fluence the profiles broaden toward the surface with the rear edge remaining at a constant depth.

Trapping and release of keV deuterium in pyrolytic graphite has been the subject of several investigations because of its relevance to the problem of interaction of a hot fusion plasma with the solid wall. In the present work the influence of He-induced damage on implantation profiles for deuterium in pyrolytic graphite is investigated for either a smaller (9 keV D + , 3 keV He + ) or larger He range (1.5 keV D + , 13 keV He + ). During annealing, the implanted D is found to be retained more strongly at depths where He-damage has been introduced. The results show that the trapping sites of deuterium in pyrolytic graphite are at least partly connected with radiation damage.

Confinement studies on the Impurity Study Experiment (ISX-B) in beam-heated plasmas contaminated with small quantities of low-Z impurities are reported. Experimental results on the correlation of particle and energy confinement are presented. A linear relationship of energy confinement and plasma density is observed. As density is increased further, this effect saturates and energy confinement becomes independent of electron density. The experiments have been extended to higher beam power, resulting in an expansion of the ISX-B operating space. Impurities other than neon (carbon and silicon) have been tried and do not produce an enhancement in confinement. Edge cooling by the introduction of impurities has been demonstrated. The change in confinement has been shown to be correlated with changes in the normalized poloidal field fluctuation level (θ/Bθ) but not with the density fluctuation level (ne/ne). The experimental results are compared with models of drift-wave and resistive ballooning turbulence and an explanation is offered for the difference between the results with recycling and non-recycling impurities.

The interaction of implanted deuterium and helium with beryllium is of significant interest in the application of first wall coatings and other components of fusion reactors. Electropolished polycrystalline beryllium was first implanted with a Xe backscatter marker at 1.98 MeV followed by either implantation with 5 keV diatomic deuterium or helium. A 2.0 MeV He beam was used to analyze for impurity buildup, namely oxygen. The oxide layer thickness was found to increase linearly with increasing implant fluence. A 2.5 MeV H+ beam was used to depth profile the D and He by ion backscattering. In addition the retention of the implant was measured as a function of the implant fluence. The mean depth of the implant was found to agree with theoretical range calculations.Scanning electron microscopy was used to observe blister formation. No blisters were observed for implanted D but for implanted He, blisters occurred at $ 1.75 × 1017 He·cm−2. The blister diameter increased with increasing implant fluence from about 0.8 μm at 1018 He·cm−2 to 5.5 μm at 3 x 1018 He·cm−2.

Ion backscattering has been used to study the diffusion couple V-Be at annealing temperatures in the range 800 to 1100 K. Analysis of proton and helium backscattering allowed determination of the average composition versus depth following in situ isothermal anneals of thin vapor-deposited vanadium films on beryllium substrates. The results were interpreted as an initial diffusion governed by grain boundary migration of the beryllium through the vanadium to form a beryllium oxide surface layer. Vanadium was found to be excluded from the beryllium oxide surface layer and also from the native oxide on the beryllium substrate. The initial rapid diffusion along grain boundaries was followed by a slower diffusion into the vanadium grains. The amount of beryllium which diffused into the vanadium film obeyed a t 1 2 dependence where t is the anneal time. Complete anneal sequences were taken at two temperatures and a tentative activation energy for the diffusion of beryllium in bulk vanadium of 3.4 eV was determined. The diffusion coefficient was estimated to be 1.0 × 10−17cm2/sec at 958 K and 0.8 × 10−18cm2/sec at 903 K.

The depth profiles and retention behavior of 4He implanted at 80 keV into vanadium have been investigated in cold rolled bulk and foil samples. The specimens were implanted at temperatures of 100, 400, and 800° C and at fluences up to 1 × 1018He/cm2. Helium depth distributions were found to be Gaussian for the 100° C implants but exhibited a double peak appearance for some of the highest fluence 400° C and 800° C implants. In polished samples blistering and flaking occurred at both 100° C and 400° C implant temperatures for fluences greater than 5 × 1017He/cm2, but little of the implanted helium appeared to have been released at a result of the exfoliation. Conversely, most of the implanted helium was released from 800 C implant areas though no significant blistering or surface perforation was observed. Blistering was observed to occur only on polished samples, through the release behavior was similar to that of the unpolished specimens on which no blistering was observed at any temperature or fluence. The surface condition of samples polished by different techniques was found to exert an influence on the temperature dependence of release and on the character of the blister topography.

A technique using nuclear microanalysis has been developed to determine 2D an 3He concentrations versus depth profiles in the near surface regions (∼2 μm) of solids. Ultimate near-surface depth resolutions of (≈100 A) should be attainable by these techniques. A probing beam of 3He ions is used to analyze for the deuterium. By energy analyzing the emitted 4He ions from the reaction d(3He,p)4He and by simple computer analysis, deuterium concentration versus depth profiles are obtained. The same methods are applicable for 3He profiling except in that case a 2D probing beam is used. The techniques is currently being developed using Er hydride and Sc hydride films. It is particularly suited for the study of the transition metals with high hydrogen solubility such as Nb and V which are of interest for CTR reactor applications.

Measurements of electron-capture cross sections ${\ensuremath{\sigma}}_{10}$ and electron-loss cross sections ${\ensuremath{\sigma}}_{01}$ for protons and atomic hydrogen in ${\mathrm{H}}_{2}$, He, Ar, Kr, ${\mathrm{N}}_{2}$, ${\mathrm{O}}_{2}$, CO, C${\mathrm{O}}_{2}$, ${\mathrm{H}}_{2}$O, C${\mathrm{H}}_{4}$, ${\mathrm{C}}_{2}$${\mathrm{H}}_{4}$, ${\mathrm{C}}_{2}$${\mathrm{H}}_{6}$, and ${\mathrm{C}}_{4}$${\mathrm{H}}_{10}$ are reported and compared with published theoretical estimates and experimental results. The energy range was 100 to 2500 keV. The results are presented in graphical form. By applying the additive rule, the cross sections ${\ensuremath{\sigma}}_{10}$ and ${\ensuremath{\sigma}}_{01}$ are estimated for hydrogen particles in carbon.

Measurements of the absolute stopping cross sections of reactive metals have been made by ion back-scattering using in situ film deposition. The success of the method rests on the dual features of (1) an absence of impurities in the film (particularly oxygen) and (2) the measurement of the target areal density to a high degree of accuracy in the vacuum. Contamination was minimized by vacuum depositing the reactive metal onto the target substrate in an ultrahigh vacuum chamber attached to the beam line of a 2.5 MeV Van de Graaff accelerator. In addition, two independent quartz microbalances built into the substrate holder provided accurate measurements of the film areal density. Using this technique, the stopping cross sections for helium ions in erbium have been determined from 250 keV to 2.5 MeV; these cross sections were used to determine the parameters for the analytic expression for the electronic stoppinf cross section formula developed by D.K. Brice. The values of the parameters are: Z = 2.997, a = 0.3197 and n = 3.168.

Agrobacterium tumefaciens strains 1D135 and B6 were characterized. Both strains formed circular, smooth, creamy, shiny colonies on rich medium. In the scanning electron microscope their morphologies were bacilliform rods which possessed 1 to 6 peritrichous flagella. The optimum growth temperature was 31·8±0·5 °C for strain 1D135 and 32·1±0·5 °C for strain B6. Generation times at 32 °C were 62 and 61 min for strains 1D135 and B6 respectively. Both strains possessed activities of d -glucoside-3-dehydrogenase, catalase, oxidase, urease, nitrate reductase and β-galactosidase. Both strains produced acid on basal medium with arabinose, cellobiose, fructose, galactose, lactose or salicin. The 70s ribosomal proteins of these two strains were identical in electrophoretic mobilities in 7·5% acrylamide-urea gels at pH 4·3. Crown-gall tumor-inducing activity was not found in preparations of 70 s ribosomes, and messenger, ribosomal or transfer RNA. Nor was tumor-initiating activity in the case of strain 1D135 associated with circular satellite DNA molecules. Furthermore, almost all preparations of the bacterial chromosome lacked tumor inducing activity. A few preparations of high molecular weight DNA induced crown-gall-like tumors. The implications of this finding are discussed.

The 4 He + beam from a Van de Graaff accelerator is often accompanied by an 16 O + beam of the same energy. If, after acceleration and before magnetic analysis, one electron is stripped from the oxygen ion to form 16 O 2+ , these ions will not be separated from 4 He + during magnetic analysis. The 16 O 2+ fraction in the 4 He + beam was measured by analyzing back-scattering spectra for a thin Au film and the O to He ion charge ratio of 2:1 was confirmed by electrostatic deflection. Ion source conditions and the pressure in the beam lines strongly affect the 16 O 2+ fraction and the dependence of the O 2+ /O + ratio on pressure is found to be in approximate agreement with predicted values. A formula for estimating the 16 O 2+ beam intensity, based on charge exchange data and measurement of the primary 16 O + beam intensity, is N [ O 2+ ] = 13 P ( torr ) l ( cm ) N [ O + ], where P is the total gas pressure, l the length of the beam line between the accelerator and switching magnet and N [O 2+ ] and N [O + ] are the beam intensities of the respective species. The 16 O 2+ contamination of 4 He + beams is easily removed by electrostatic separation.

A comparison of predicted and actual progress during the period Sept. 78 to Aug. 1979 is made. A schedule for FY 81, 82, 83, 84, and 85 is given. (MOW)

This report describes the limiters and internal components of the Impurity Study Experiment (ISX-B) as of May 1983. The positions of the fixed limiters and internal components are noted; for movable limiters the limits of position are given. In addition, the function, shape, size, and material of each component are given, along with the name of the scientist responsible for that component.

The global recombination rate coefficient k/sub r/ for hydrogen has been measured in the TEXT tokamak vacuum vessel for various surface conditions. An attempt was made to correlate the measured values of k/sub r/ with residual gas analyzer (RGA) data taken before each measurement of k/sub r/ and with the power radiated during tokamak discharges produced after each measurement of k/sub r/. The results show that k/sub r/ increases during a series of tokamak discharges, k/sub r/ is relatively insensitive to power radiated during tokamak discharges, and k/sub r/ increases with the RGA measurements of mass 28 and 40 but not with those of mass 18. In addition, it was found that the mass 18 (H/sub 2/O) signal decreases as glow discharge experiments with hydrogen were performed.

The effects of surface preparation on the propensity of a material to exfoliate, the thickness of the flakes observed in the 400/sup 0/C implant of electropolished vanadium, and the possibility of a correlation between implant fluence, integrated stress and helium retention are addressed. Results are presented. (GHT)