42 research outputs found
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Diagnostic enhancements for plasma processing
This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Funds obtained under this project were used to enhance the diagnostic capabilities of the plasma-processing program in the Physics Division at LANL and include successful development and implementation of in-situ Raman spectroscopy and infrared emission spectroscopy. These methods were used to detect the presence and nature of ground-state and electronically excited molecular oxygen formed in an atmospheric-pressure, nonthermal plasma source used for environmental, industrial and decontamination applications
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Plasma source ion implantation research and applications at Los Alamos National Laboratory
Plasma Source Ion Implantation research at Los Alamos Laboratory includes direct investigation of the plasma and materials science involved in target surface modification, numerical simulations of the implantation process, and supporting hardware engineering. Target materials of Al, Cr, Cu-Zn, Mg, Ni, Si, Ti, W, and various Fe alloys have been processed using plasmas produced from Ar, NH{sub 3}, N{sub 2}, CH{sub 4}, and C{sub 2}H{sub 2} gases. Individual targets with surface areas as large as {approximately}4 m{sup 2}, or weighing up to 1200 kg, have been treated in the large LANL facility. In collaboration with General Motors and the University of Wisconsin, a process has been developed for application of hard, low friction, diamond-like-carbon layers on assemblies of automotive pistons. Numerical simulations have been performed using a 2{1/2}-D particle- in-cell code, which yields time-dependent implantation energy, dose, and angle of arrival for ions at the target surface for realistic geometries. Plasma source development activities include the investigation of pulsed, inductively coupled sources capable of generating highly dissociated N{sup +} with ion densities n{sub i} {approximately} 10{sup 11}/cm{sup 3}, at {approximately}100 W average input power. Cathodic arc sources have also been used to produce filtered metallic and C plasmas for implantation and deposition either in vacuum, or in conjunction with a background gas for production of highly adherent ceramic coatings
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Intense diagnostic neutral beam development for ITER
For the next-generation, burning tokamak plasmas such as ITER, diagnostic neutral beams and beam spectroscopy will continue to be used to determine a variety of plasma parameters such as ion temperature, rotation, fluctuations, impurity content, current density profile, and confined alpha particle density and energy distribution. Present-day low-current, long-pulse beam technology will be unable to provide the required signal intensities because of higher beam attenuation and background bremsstrahlung radiation in these larger, higher-density plasmas. To address this problem, we are developing a short-pulse, intense diagnostic neutral beam. Protons or deuterons are accelerated using magnetic-insulated ion-diode technology, and neutralized in a transient gas cell. A prototype 25-kA, 100-kV, 1-{mu}s accelerator is under construction at Los Alamos. Initial experiments will focus on ITER-related issues of beam energy distribution, current density, pulse length, divergence, propagation, impurity content, reproducibility, and maintenance
A vacuum double-crystal spectrometer for reference-free highly charged ions X-ray spectroscopy
We have built a vacuum double crystal spectrometer, which coupled to an
electron-cyclotron resonance ion source, allows to measure low-energy x-ray
transitions in highly-charged ions with accuracies of the order of a few parts
per million. We describe in detail the instrument and its performances.
Furthermore, we present a few spectra of transitions in Ar, Ar
and Ar. We have developed an ab initio simulation code that allows us
to obtain accurate line profiles. It can reproduce experimental spectra with
unprecedented accuracy. The quality of the profiles allows the direct
determination of line width.Comment: 21 pages; Version
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Compact toroids generated by a magnetized coaxial source in the CTX experiment
Compact toroids containing both toroidal and poloidal magnetic field (Spheromak-type) have been generated in CTX using a magnetized coaxial plasma gun. These CTs tear loose from the gun by magnetic field line reconnection, and they are trapped in flux conservers having various geometries. In a straight cylindrical flux conserver the CTs are observed to be unstable to a gross tilting mode. Stability to the tilting mode has been demonstrated in flux conservers having an oblate trapping region; however, the geometry of the entrance region leading to the trapping volume can also have important effects. Lifetimes of about 150 ..mu..s for the CTs are typically observed. Interferometric measurements give a value of about 2 x 10/sup 14/ cm/sup -3/ for the initial plasma density. The plasma temperature measured at a single spot near the minor magnetic axis decreases to around 10 eV by the time the magnetic reconnection is complete. Spectrographic measurements and pressure probe results are in agreement with this temperature. A snipper coil has been installed to induce the CT to tear loose from the gun sooner. The use of this coil is observed to speed up the magnetic field reconnection process by about a factor of 2
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Plasma source ion implantation of metal ions: Synchronization of cathodic-arc plasma production and target bias pulses
An erbium cathodic-arc has been installed on a Plasma Source Ion Implantation (PSII) experiment to allow the implantation of erbium metal and the growth of adherent erbia (erbium oxide) films on a variety of substrates. Operation of the PSII pulser and the cathodic-arc are synchronized to achieve pure implantation, rather than the hybrid implantation/deposition being investigated in other laboratories. The relative phase of the 20 {mu}s PSII and cathodic-arc pulses can to adjusted to tailor the energy distribution of implanted ions and suppress the initial high-current drain on the pulse modulator. The authors present experimental data on this effect and make a comparison to results from particle-in-cell simulations
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Design of a high-voltage generator for the LASL implosion-heating experiment
The goals of the LASL implosion-heating experiment are to learn more about the physical processes involved in the initial implosion of a theta pinch and to find ways of euhancing the amount of implosion heating. The design parameters chosen for the experiment are: an initial plasma density of 10/sup 15/ deuterons per cm/sup 3/, a 40-cm-diameter discharge tube, a coil length of one meter, an initial electric field of 2 kV/cm applied to the inside of the discharge tube, and a magnetic field of l0 kG having a fast risetime and lasting for 500 nsec. This experiment differs from the collisionless shock experiments that have been conducted over the past few years at other laboratories in that a much higher initial plasma density is present. The higher density reduces the effective impedance of the plasma and thus requires a lowerimpedance current source. The design of a high-voltage pulse generator is described. Systems that have been considered are: 1) Mylar-insulated stripline Blumlein generators, 2) simple Mylar striplines, 3) combinations of Mylar striplines with capacitors, 4) water-insulated coaxial transmission lines, 5) capacitors, and 6) lumped-constant transmission lines. The system finally selected is a hybrid of a peaking- capacitor system with a curtailed, lumped-constant delay line. All systems were investigated by computation, mostly using the NET-2 code. The calculation takes into account the changing impedance of the load due to the motion of the imploding plasma sheath. Plasma dynamics were simulated using the bounce model, which assumes perfect elastic reflection of all ions from an impinging magnetic piston. The final design employs four coil feed points with a 125kV generator at each one, totaling 500 kV. Each 125-kV generator consists of a pulse-charged two- element lumped-constant line. An essential feature of the circuit is fast charging from Marx generators through the inductance of the Marx and of the connecting cable system. The load switches are fired when the voltage on the lumped-constant line reaches 125 kV, at which time the voltage is still rising rapidly. At the peak load current, about 300 kA is contributed by the charging current from the Marx bank and 500 kA comes from the capacitors of the lumpedconstant line. (auth