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Pulsed gas load pumping of hydrogen by vapor deposited titanium films

Description: The Princeton Poloidal Divertor Experiment (PDX) plans to use titanium gettering of hydrogen to provide the high pumping speeds required to capture the pulsed gas load which occurs in the region where the diverted plasma is neutralized. Detailed information with respect to hydrogen titanium film interactions under similar conditions was sought so that engineering decisions could be made with greater confidence. Pumping speeds for hydrogen on titanium films were determined by admitting a pulse of gas into the volume enclosed by the substrate and measuring the time constant of the pressure decay. The measurement was made periodically as the film was deposited, and when the maximum sticking coefficient was reached, sublimation was stopped and additional gas pulses admitted to determine the speed vs. hydrogen concentration in the Ti film. The amount of gas per pulse varied from 0.25 to 5 monolayers. Atomic hydrogen produced by thermal dissociation in a continuous measurement gave minimum-values for the sticking coefficient of 0.3 for a room temperature film. A summary of results is shown. Titanium film peeling tests were performed and sublimation sources were test operated. (auth)
Date: January 1, 1976
Creator: Martin, G.D.
Partner: UNT Libraries Government Documents Department

Comparison of the D-T neutron wall load distributions in several tokamak fusion reactor designs

Description: The distributions of the neutron angular and scalar flux and current around the wall of three proposed tokamak fusion reactor designs are investigated in detail. The calculational method involves a numerical solution of the integral form of the neutron transport equation using a ray tracing process. The wall loading in a circular cross section tokamak and in two non-circular tokamaks, the Princeton Reference Design and the University of Wisconsin UWMAK, are compared for three different plasma source distributions. The variation of the angular neutron flux at different wall points is investigated for each design. Neutron wall load peaking factors are also calculated and compared for each design, and are found to be sensitive to both the wall shape and plasma source. The divertors in the two non-circular designs are studied for neutron streaming losses and for the wall load in those regions. (auth)
Date: December 1, 1975
Creator: Chapin, D.L. & Price, W.G. Jr.
Partner: UNT Libraries Government Documents Department

Low noise control valve

Description: Noise is one of the problems associated with the use of any type of control valve in systems involving the flow of fluids. The advent of OSHA standards has prompted control valve manufacturers to design valves with special trim to lower the sound pressure level to meet these standards. However, these levels are in some cases too high, particularly when a valve must be located in or near an area where people are working at tasks requiring a high degree of concentration. Such locations are found around and near research devices and in laboratory-office areas. This paper describes a type of fluid control device presently being used at PPL as a bypass control valve in deionized water systems and designed to reduce sound pressure levels considerably below OSHA standards. Details of the design and construction of this constant pressure drop variable flow control valve are contained in the text and are shown in photographs and drawings. Test data taken are included. (auth)
Date: January 1, 1975
Creator: Christie, R.S.
Partner: UNT Libraries Government Documents Department

Conceptual design of a divertor for a tokamak experimental power reactor

Description: A design for a Double-Null Poloidal Divertor for a Tokamak EPR is presented which allows remote assembly of the torus and utilizes a standard neutral pumping and heat removal system. (auth)
Date: January 1, 1975
Creator: Georgievsky, A.V.; Gralnick, S.L.; Jassby, D.L.; Meade, D.M.; Saksagansky, L.G.; Stephanovsky, A.M. et al.
Partner: UNT Libraries Government Documents Department

2XIIB getter material problems

Description: The uniformity of wire characteristics is vital to the reliable long- time operation of the titanium alloy wire. Of particular importance is the diameter, total emissivity, and alloy mix. The getter wire must be operated at a minimum rate while the life is determined by the maximum rate. At a particular current the difference between the maximum and minimum rate is determined by variations in wire characteristics. Small percentage variations in these characteristics can result in large variations in gettering rate. (auth)
Date: November 18, 1975
Creator: Vogtlin, G. E.
Partner: UNT Libraries Government Documents Department

Application of sensitivity analysis to a quantitative assessment of neutron cross-section requirements for the TFTR: an interim report

Description: A computational method to determine cross-section requirements quantitatively is described and applied to the Tokamak Fusion Test Reactor (TFTR). In order to provide a rational basis for the priorities assigned to new cross- section measurements or evaluations, this method includes quantitative estimates of the uncertainty of currently available data, the sensitivity of important nuclear design parameters to selected cross sections, and the accuracy desired in predicting nuclear design parameters. Perturbation theory is used to combine estimated cross-section uncertainties with calculated sensitivities to determine the variance of any nuclear design parameter of interest. (auth)
Date: September 1, 1975
Creator: Gerstl, S.A.W.; Dudziak, D.J. & Muir, D.W.
Partner: UNT Libraries Government Documents Department

Accelerator-based neutron generator (addendum)

Description: A proposal to design, construct, and operate a D--Li intense neutron source for CTR materials research is discussed. Information pertaining to the following areas is given: (1) radiation damage effectiveness, (2) Linac design and performance, (3) target design and performance, (4) experimental area design, (5) construction schedule, (6) construction costs, (7) preliminary design and development program, (8) facility operation and operating costs, and (9) financial appropriation plan. (MOW)
Date: January 1976
Creator: Grand, P.
Partner: UNT Libraries Government Documents Department

Surface effects in controlled thermonuclear fusion

Description: During the operation of large size plasma facilities and future controlled thermonuclear fusion reactors the surfaces of such major components as container walls, beam limiters, diverter walls and beam-dump walls of the injector region will be exposed to particle and photon bombardment from primary plasma radiations and from secondary radiations. Such radiations can cause, for example, physical and chemical sputtering, blistering, particle- and photon- impact induced desorption, secondary electron and x-ray emission, backscattering, nuclear reactions, photo-decomposition of surface compounds, photocatalysis, and vaporization. Such effects in turn can (a) seriously damage and erode the bombarded surface and (b) release major quantities of impurities which will contaminate the plasma. The effects of some of the major surface phenomena on the operation of plasma facilities and future fusion reactors are discussed. (auth)
Date: August 1, 1975
Creator: Kaminsky, M.
Partner: UNT Libraries Government Documents Department

Energy dependent neutron sputtering and surface damage cross sections

Description: The results clearly indicate that damage function analysis might be usefully applied to define both the neutron and primary recoil energy dependence of sputtering yields. Even with relatively large data errors, it appears that it is possible to both detect the existence and indicate the form of the deviation of sputtering yield from linear damage energy dependence (if such deviation exists). This information would be very useful in developing improved models of the sputtering phenomena.
Date: January 1, 1976
Creator: Odette, G.R.; Doiron, D.R. & Kennerley, R.J.
Partner: UNT Libraries Government Documents Department

Some experimental considerations regarding ion beam simulation of neutron irradiation for mechanical property measurements

Description: A preliminary assessment of the requirements for mechanical property data related to CTR materials is given. The status of ion simulation for mechanical property measurements is described. A damage analysis and calculations for light ions are presented along with sample size, heating and cooling, and surface considerations. (MOW)
Date: January 1, 1975
Creator: Styris, D.L.; Jones, R.H.; Harling, O.K.; Kulcinski, G.L. & Marshall, R.P.
Partner: UNT Libraries Government Documents Department

Vacuum and wall problems in precursor reactor tokamaks

Description: The Princeton Large Torus (PLT) will be completed in 1975 and two other CTR oriented toroidal plasma devices, the Poloidal Divertor Experiment (PDX) and the Tokamak Fusion Test Reactor (TFTR). are planned to be completed in 1977 and 1981. The vacuum systems of these machines must satisfy stringent requirements because of unusual operating conditions, such as, magnetic field induced strains and eddy currents, energetic particle and photon bombardment, large transient gas loads, and the use of 100 Curie quantities of tritium. In addition, novel vacuum wall surfaces and fast moving mechanical or magnetic plasma limiters will be required to minimize the influx of impurities during discharges. (auth)
Date: December 1, 1975
Creator: Cohen, S.A.
Partner: UNT Libraries Government Documents Department

Counterstreaming-ion tokamak neutron source for large area surface radiation studies

Description: A tokamak neutron source that produces a neutron flux approximately 10$sup 13$ n/cm$sup 2$/s over a wall test-area of 30 m$sup 2$ is designed using near state-of-the-art tokamak and neutral-beam injection technologies. To maximize fusion reactivity, D and T plasma ions are grouped in two distinct quasi- thermal velocity distributions, oppositely displaced in velocity along the magnetic axis. Such counterstreaming distributions can be set up by tangential injection of all plasma ions by oppositely directed D and T neutral beams, by facilitating removal of completely decelerated ions, and by minimizing plasma recycling. Fusion energy is produced principally by head-on collisions between D and T ions in the counterstreaming distributions. For injection energies of 40- 60 keV, and typical tokamak parameters, the fusion power density can be approximately 1 W/cm$sup 3$, with Q approximately 1 attainable for T/sub e/ = 3.4 keV and electron energy confinement parameter n/sub e/tau/sub E/ approximately equal to 2 x 10$sup 12$ cm$sup -3$s. All plasma fueling is carried out by the injected beams, and when a significant fraction of the electron population is trapped, the plasma current can be maintained by the beams. (auth)
Date: November 1, 1975
Creator: Jassby, D.L.
Partner: UNT Libraries Government Documents Department

Leak hunting problems associated with controlled thermonuclear fusion experiments

Description: The LLL 2xIIB experiment is briefly described. The vacuum system uses mercury diffusion pumps and titanium sublimation. The base pressure of the guard vacuum is about 10$sup -5$ torr and about 2 x 10$sup -7$ torr in the high vacuum space using the diffusion pumps only. After titanium sublimation, the high vacuum pressure drops into the 10$sup -9$ torr range. A procedure for leak testing using a special sniffer probe is described. (MOW)
Date: August 25, 1975
Creator: Batzer, T.H. & Murphy, J.J.
Partner: UNT Libraries Government Documents Department

Design of a repetitively pulsed megajoule dense-plasma focus

Description: This report describes a 1 pulse per second, dense-plasma-focus (DPF) materials-testing device capable of delivering a minimum of 10$sup 15$ neutrons per pulse. Moderate scaling up from existing designs is shown to be sufficient to provide 2 x 10$sup 13$ neutrons/ cm$sup 2$. s to a suitable target. The average power consumption, which has become a major issue due to the energy crisis, is analyzed with respect to other plasma devices and is shown to be highly favorable. Also discussed is a novel approach to capacitor-bank and switch design with respect to repetitive-pulse operation. (auth)
Date: August 1, 1975
Creator: Zucker, O.; Bostick, W.; Gullickson, R.; Long, J.; Luce, J. & Sahlin, H.
Partner: UNT Libraries Government Documents Department

DT fusion neutron radiation strengthening of copper and niobium

Description: The initial results of a comparative study of the radiation strengthening and damage structures produced in Cu and Nb by D-T fusion and fission reactor neutrons are described. The radiation strengthening produced by a given fluence of fusion neutrons above about 10$sup 17$n/cm$sup 2$ is equal to that produced by a fluence of fission reactor neutrons (E greater than 0.1 MeV) ten times as great. This difference is about twice as large as would be expected if the strengthening scaled with damage energy or dpa. Initial transmission electron microscopy observations of the damage structures in fusion and fission reactor neutron irradiated copper indicate that the same type of primary structural defects, vacancy and interstitial point defect clusters and small dislocation loops with a/3 (111) and a/2 (110) Burgers vectors, are produced in both cases. The difference in the radiation strengthening produced by fusion and fission reactor neutrons in Cu appears to result from a substantially greater rate of accumulation of damage, in the form of point defect clusters, during irradiation with fusion neutrons than during irradiation with fission reactor neutrons plus a significant difference in the size and spatial distributions of the damage clusters. (auth)
Date: October 30, 1975
Creator: Mitchell, J.B.; Van Konynenburg, R.A.; Echer, C.J. & Parkin, D.M.
Partner: UNT Libraries Government Documents Department

INGRID: an intense neutron generator for radiation-induced damage studies in the CTR materials program

Description: The proposal is broken into the following chapters: (1) the need for a neutron irradiation facility, (2) characteristics of the neutron source, (3) the accelerator, (4) the lithium target source, (5) buildings, utilities, and experimental facilities, and (6) project management, schedule, and costs. (MOW)
Date: January 1, 1976
Creator: Saltmarsh, M.J. & Worsham, R.E. (eds.)
Partner: UNT Libraries Government Documents Department

Cryocondensation pumping of thick films of hydrogen and deuterium

Description: In order to obtain engineering data for design of large capacity cryopumps for hydrogen, deuterium and tritium, an apparatus was built where pumping speeds and sticking coefficients can be studied as a function of surface coverage for different leak rates. In addition, thermal conductivity and thermal absorption of these frozen gases can be inferred from the measurements of pumping speed equilibrium pressure and the helium boil-off rate. The following changes in the above parameters were observed when the surface coverage was increased from a few atomic layers to 3.8 x 10$sup 20$ molecules cm$sup -2$ for H$sub 2$ and 1.2 x 10$sup 21$ molecules cm$sup -2$ for D$sub 2$: the pumping speed decreased about 10 percent while the equilibrium pressure and helium boil-off were unchanged within the limits of our measuring accuracy; changing the gas leak rate from 0 to 2 x 10$sup -3$ Torr liters sec$sup -1$ cm$sup -2$ also decreases the pumping speed by approximately 10 percent. From the above measurements it is inferred that thermal absorption to frozen H$sub 2$ and D$sub 2$ is negligible. Based on the information obtained in our investigation we designed a cryopump having a pumping speed of 10$sup 5$ liters sec$sup -1$ for hydrogen. (auth)
Date: January 1, 1975
Creator: Halams, H.J. & Bamberger, J.A.
Partner: UNT Libraries Government Documents Department

First wall coatings

Description: As impurity problems become more significant, the selection of a suitable first wall material becomes more important. Many of the candidates are impractical either because they are difficult to fabricate or do not possess adequate strength. An alternate solution is a composite wall consisting of a suitable coating on a substrate chosen for its strength and ease of fabrication. Various techniques have been investigated for depositing a variety of candidate materials onto 304 L stainless steel. Thick coatings of several of these materials have been satisfactorily deposited utilizing ion plating. This technique is described in some detail. (auth)
Date: January 1, 1975
Creator: Simpkins, J.E.
Partner: UNT Libraries Government Documents Department

Impurity and surface studies in ORMAK

Description: The ORMAK tokamak has been in operation since 1971, and surface impurity problems have been pursued from the beginning. Surface studies of materials removed from ORMAK have revealed the presence of C, O, and Fe. These are also the principal impurities observed spectroscopically in plasma discharges, although numerous other elements are present in lesser amounts. Spectroscopy, x- ray measurements, plasma resistance, and fast ion scattering have been used in an effort to determine Z/sub eff/, the effective nuclear charge of plasma ions. All four measurements have practical difficulties leading to relatively large experimental error limits. Oxygen discharge pre-cleaning has allowed ORMAK discharges to reach higher currents and correspondingly higher ion and electron temperatures; spectroscopic studies reveal a lower level of contaminants, particularly C and N. Power measurements indicate that most of the input power strikes the walls, mostly as radiation. By varying operating parameters it is found that Z/sub eff/ approximately I/sub p//anti n/sub e/. (auth)
Date: January 1, 1976
Creator: Colchin, R.J.; Bush, C.E.; Jahns, G.L.; Lyon, J.F.; Murakami, M.; Neidigh, R.V. et al.
Partner: UNT Libraries Government Documents Department

Helium blistering of ceramic coatings on Hastelloy X and Nb--1% Zr

Description: The surface damage of insulating ceramic coatings on Hastelloy X and Nb-- 1 percent Zr held at room temperature and at 300$sup 0$C was studied for both 100 keV and 250 keV helium ion irradiation for a dose range from 3.7 x 10$sup 18$ to 1 x 10$sup 19$ ions cm$sup -2$. Blisters were observed after room temperature irradiation with both 100 keV and 250 keV helium ions. However, for irradiation at 300$sup 0$C no blisters could be observed. The sharp rise in the helium permeation with temperature, observed by others for some glasses and ceramics, is thought to be responsible for this behavior. These results suggest that for the energy range studied helium blistering has a negligible surface erosion effect on such coatings if they are operated at temperatures above 300$sup 0$C. (auth)
Date: January 1, 1975
Creator: Kaminsky, M.; Das, S.K. & Ekern, R.
Partner: UNT Libraries Government Documents Department

Plasma-wall interaction in ATC during high power neutral beam injection

Description: Measurements of the elemental composition of the vacuum vessel wall surface and impurity influx into ATC during high power beam-heated discharges are combined with previous measurements of power balance and scaling laws to give a self consistent model of plasma-wall interaction in ATC. It is shown that plasma charge exchange induced desorption is the main cause of impurity influx during neutral beam injection. Impurities change the net power balance in these beam- heated discharges by approximately 15 percent. (auth)
Date: January 1, 1976
Creator: Cohen, S.A.
Partner: UNT Libraries Government Documents Department

Radiation damage by $sup 252$Cf fission fragments and alpha particles

Description: Rates of atom displacement and helium injection in materials exposed to $sup 252$Cf fission fragments and alpha particles were calculated to establish the potential for use of $sup 252$Cf sources for radiation damage studies. Maximum displacement rates of about 10$sup -6$ dpa/sec at the surface of typical targets exposed to a $sup 252$Cf fission fragment source were comparable to those experienced by materials in a fast breeder reactor or in a controlled thermonuclear reactor (CTR) first wall, though much lower than the displacement rates achieved using particle accelerators. Helium was concurrently accumulated at a rate of 3 x 10$sup -4$ atom ppM/sec at the target surface, yielding a He/ displacement ratio 10$sup 3$ times that produced in the fast breeder reactor materials, but only about 20 times that produced in the CTR materials. These comparisons suggest that $sup 252$Cf fission fragment sources may find useful applications in studies of effects of high-He content on radiation damage in CTR materials. (auth)
Date: January 1, 1975
Creator: Gould, T. H., Jr. & McDonell, W. R.
Partner: UNT Libraries Government Documents Department