135 Matching Results

Search Results

Advanced search parameters have been applied.

Geometrical Aspects of a Hollow-cathode Magnetron (HCM)

Description: A hollow-cathode magnetron (HCM), built by surrounding a planar sputtering-magnetron cathode with a hollow-cathode structure (HCS), is operable at substantially lower pressures than its planar-magnetron counterpart. We have studied the dependence of magnetron operational parameters on the inner diameter D and length L of a cylindrical HCS. Only when L is greater than L sub zero, a critical length, is the HCM operable in the new low-pressure regime. The critical length varies with HCS inner diameter D. Explanations of the lower operational pressure regime, critical length, and plasma shape are proposed and compared with a one-dimension diffusion model for energetic or primary electron transport. At pressures above 1 mTorr, an electron-impact ionization model with Bohm diffusion at a temperature equivalent to one-half the primary electron energy and with an ambipolar constraint can explain the ion-electron pair creation required to sustain the discharge. The critical length L sub zero is determined by the magnetization length of the primary electrons.
Date: November 1, 1998
Creator: Cohen, Samuel, A. & Wang, Zhehui
Partner: UNT Libraries Government Documents Department

Model for designing planar magnetron cathodes

Description: This report outlines an analytical model of the distribution of plasma in the cathode fall of a planar magnetron cathode. Here I continue commentary on previous work, and introduce an ion sheath model to describe the discharge dark space below the magnetron halo.
Date: September 30, 1997
Creator: Garcia, M.
Partner: UNT Libraries Government Documents Department

A regulated magnetron pulser

Description: This paper describes and analysis of a 4.5-kV, 500-mA, regulated current pulser used to drive a Hitachi ZM130 magnetron in a particle-accelerator injector. In this application, precise beam from the injector. A high-voltage triode vacuum tube with active feedback is used to control the magnetron current. Current regulation and accuracy is better than 1%. The pulse width may be varied from as little as 5 {mu}m to cw by varying the width of a gate pulse. The current level can be programmed between 10 and 500 mA. Design of the pulser including circuit simulations, power calculations, and high-voltage issues are discussed.
Date: September 1, 1997
Creator: Rose, C.R.
Partner: UNT Libraries Government Documents Department

Use of an Injection Locked Magnetron to Drive a Superconducting RF Cavity

Description: The use of an injection locked CW magnetron to drive a 2.45 GHz superconducting RF cavity has been successfully demonstrated. With a locking power less than -27 dB with respect to the output and with a phase control system acting on the locking signal, cavity phase was accurately controlled for hours at a time without loss of lock whilst suppressing microphonics. The phase control accuracy achieved was 0.8 deg. r.m.s. The main contributing disturbance limiting ultimate phase control was power supply ripple from the low specification switch mode power supply used for the experiment.
Date: May 1, 2010
Creator: Haipeng Wang, Robert Rimmer, G. Davis, Imran Tahir, Amos Dexter, Greame Burt, Richard Carter
Partner: UNT Libraries Government Documents Department

Phase and Frequency Locked Magnetrons for SRF Sources

Description: Magnetrons are low-cost highly-efficient microwave sources, but they have several limitations, primarily centered about the phase and frequency stability of their output. When the stability requirements are low, such as for medical accelerators or kitchen ovens, magnetrons are the very efficient power source of choice. But for high energy accelerators, because of the need for frequency and phase stability - proton accelerators need 1-2 degrees source phase stability, and electron accelerators need .1-.2 degrees of phase stability - they have rarely been used. We describe a novel variable frequency cavity technique which will be utilized to phase and frequency lock magnetrons.
Date: May 1, 2009
Creator: Neubauer, M.; Johnson, R.P.; /Muons Inc., Batavia; Popovic, M.; Moretti, A. & /Fermilab
Partner: UNT Libraries Government Documents Department

Proposed FNAL 750 KeV Linac Injector Upgrade

Description: The present FNAL linac H{sup -} injector has been operational since 1978 and consists of a magnetron H{sup -} source and a 750 keV Cockcroft-Walton Accelerator. The proposed upgrade to this injector is to replace the present magnetron source having a rectangular aperture with a circular aperture, and to replace the Cockcroft-Walton with a 200 MHz RFQ. Operational experience at other laboratories has shown that the upgraded source and RFQ will be more reliable and require less manpower than the present system.
Date: April 1, 2009
Creator: Tan, C.Y.; Bollinger, D.S.; Schmidt, C.W. & /Fermilab
Partner: UNT Libraries Government Documents Department

Element-specific study of the temperature dependent magnetization of Co-Mn-Sb thin films

Description: Magnetron sputtered thin Co-Mn-Sb films were investigated with respect to their element-specific magnetic properties. Stoichiometric Co{sub 1}Mn{sub 1}Sb{sub 1} crystallized in the C1{sub b} structure has been predicted to be half-metallic and is therefore of interest for spintronics applications. It should show a characteristic antiferromagnetic coupling of the Mn and Co magnetic moments and a transition temperature T{sub C} of about 480K. Although the observed transition temperature of our 20nm thick Co{sub 32.4}Mn{sub 33.7}Sb{sub 33.8}, Co{sub 37.7}Mn{sub 34.1}Sb{sub 28.2} and Co{sub 43.2}Mn{sub 32.6}Sb{sub 24.2} films is in quite good agreement with the expected value, we found a ferromagnetic coupling of the Mn and Co magnetic moments which indicates that the films do not crystallize in the C1{sub b} structure and are probably not fully spin-polarized. The ratio of the Co and Mn moments does not change up to the transition temperature and the temperature dependence of the magnetic moments can be well described by the mean field theory.
Date: September 30, 2008
Creator: Schmalhorst, J.; Ebke, D.; Meinert, M.; Thomas, A.; Reiss, G. & Arenholz, E.
Partner: UNT Libraries Government Documents Department

Studies of SmCo5/Fe nanocomposite magnetic bilayers with magnetic soft x-ray transmission microscopy

Description: A hard/soft SmCo{sub 5}/Fe nanocomposite magnetic bilayer system has been fabricated on X-ray transparent 100-200 nm thin Si{sub 3}N{sub 4} membranes by magnetron sputtering. The microscopic magnetic domain pattern and its behavior during magnetization reversal in the hard and soft magnetic phases have been individually studied by element specific magnetic soft x-ray microscopy at a spatial resolution of better than 25nm. We observe that the domain patterns for soft and hard phases switch coherently throughout the full hysteresis cycle upon applying external magnetic fields. We derived local M(H) curves from the images for Fe and SmCo5 separately and found switching for both hard and soft phases same.
Date: December 4, 2009
Creator: Shahzad, F.; Siddiqi, S. A.; Im, M.-Y.; Avallone, A.; Fischer, P.; Hussain, Z. et al.
Partner: UNT Libraries Government Documents Department

A Hollow Cathode Magnetron (HCM)

Description: A new type of plasma sputtering device, named the hollow cathode magnetron (HCM), has been developed by surrounding a planar magnetron cathode with a hollow cathode structure (HCS). Operating characteristics of HCMs, current-voltage ( I-V ) curves for fixed discharge pressure and voltage-pressure ( V-p ) curves for fixed cathode current, are measured. Such characteristics are compared with their planar magnetron counterparts. New operation regimes, such as substantially lower pressures (0.3 mTorr), were discovered for HCMs. Cathode erosion profiles show marked improvement over planar magnetron in terms of material utilization. The use of HCMs for thin film deposition are discussed.
Date: April 1, 1998
Creator: Cohen, S.A. & Wang, Z.
Partner: UNT Libraries Government Documents Department

Performance and test results of a regulated magnetron pulser

Description: This paper describes the test results and performance of a 5.0-kV, 750-mA, regulated current pulser used to drive an Hitachi model 2M130 2,425-MHz magnetron. The magnetron is used to modulate the plasma in a particle accelerator injector. In this application, precise and stable rf power is crucial to extract a stable and accurate particle beam. A 10-kV high-voltage triode vacuum tube with active feedback is used to control the magnetron current and output rf power. The pulse width may be varied from as little as ten microseconds to continuous duty by varying the width of a supplied gate pulse. The output current level can be programmed between 10 and 750 mA. Current regulation and accuracy are better than 1%. The paper discusses the overall performance of the pulser and magnetron including anode current and rf power waveforms, linearity compliance, and vacuum tube performance.
Date: December 31, 1998
Creator: Rose, C.R. & Warren, D.S.
Partner: UNT Libraries Government Documents Department

Suppression of the 1 MHz beam current modulation in the LEDA/CRITS proton source

Description: Earlier operation of a microwave proton source exhibited an approximate 1-MHz modulation in the beam current. This oscillation could cause instabilities at higher energies in the linac, as the low-level RF control for linac operation rolls off at 200 kHz. Tests on a dummy load show the modulation is created by the magnetron itself: at a typical power level required for the source operation (680W), the 1-MHz sideband level was as high as {minus}4 dB from carrier. Since the magnetron exhibited better behavior at higher levels, a RF power attenuator is inserted to force the magnetron to run at a 50% higher power level for the same final power in the load. This attenuator is made of two antennas plunged in the waveguide and connected to dummy loads by a coaxial line. As the antenna are separated by a quarter of the guided wavelength, mismatching effects approximately cancel each other. The antenna length is experimentally adjusted to obtain the {minus}1.8 dB attenuation required. Magnetron operation at the higher power level gives a beam current spectrum free of the 1-MHz modulation, showing the coherent beam noise is not generated by plasma chamber phenomena.
Date: December 1, 1998
Creator: Balleyguier, P.; Sherman, J. & Zaugg, T.
Partner: UNT Libraries Government Documents Department

Influence of Base Pressure on FeMn Exchange Biased Spin-Valve Films

Description: Spin-valve films of structure NiFeCo/Co/Cu/NiFeCo(Co)/FeMn/Cu were deposited on Si substrates by DC planetary magnetron sputtering techniques. The influence of base pressure, P{sub b}, on spin-valve properties was studied by varying P{sub b} over two decades from 3 x 10{sup -8} to 7 x 10{sup -6} Torr. The GMR ratio show a slight increase with increasing P{sub b} until a large decrease occurs at P{sub b} > 3.3 x 10{sup -6} Torr. Exchange bias field and blocking temperature remain constant in the base pressure range between 3 x 10{sup -8} and 5 x 10{sup -7} Torr before a large reduction begins. An upper bound base pressure, {sup u}P{sub b} {approx} 5 x 10{sup -7} Torr, is noted from the data, above which significant performance modification begins. The degradation in exchange bias field and blocking temperature, in particular, in spin-valve films using a NiFeCo pinned layer, is the result of deterioration in the crystallographic texture and can be understood due to the contamination both at the ferromagnetic/antiferromagnetic interface and in the bulk of FeMn layer.
Date: August 13, 1999
Creator: Mao, M.; Cerjan, C.; Law, B.; Grabner, F. & Vaidya, S.
Partner: UNT Libraries Government Documents Department

Nitrogen Atom Energy Distributions in a Hollow-cathode Planar Sputtering Magnetron

Description: Energy distributions of N atoms in a hollow-cathode planar sputtering magnetron were obtained by use of optical emission spectroscopy. A characteristic line, N I 8216.3 Å, well-separated from molecular nitrogen emission bands, was identified. Jansson's nonlinear spectral deconvolution method, refined by minimization of {chi}<sub>w</sub> &sup2; , was used to obtain the optimal deconvolved spectra. These showed nitrogen atom energies from 1 eV to beyond 500 eV. Based on comparisons with VFTRIM results, we propose that the energetic N atoms are generated from N<sub>2</sub><sup>+</sup> ions after these ions are accelerated through the sheath and dissociatively reflect from the cathode.
Date: June 1, 1999
Creator: Ruzic, D.N.; Goeckner, M.J.; Cohen, Samuel A. & Wang, Zhehui
Partner: UNT Libraries Government Documents Department

Development of Nb and Alternative Material Thin Films Tailored for SRF Applications

Description: Over the years, Nb/Cu technology, despite its shortcomings due to the commonly used magnetron sputtering, has positioned itself as an alternative route for the future of superconducting structures used in accelerators. Recently, significant progress has been made in the development of energetic vacuum deposition techniques, showing promise for the production of thin films tailored for SRF applications. JLab is pursuing energetic condensation deposition via techniques such as Electron Cyclotron Resonance and High Power Impulse Magnetron Sputtering. As part of this project, the influence of the deposition energy on the material and RF properties of the Nb thin film is investigated with the characterization of their surface, structure, superconducting properties and RF response. It has been shown that the film RRR can be tuned from single digits to values greater than 400. This paper presents results on surface impedance measurements correlated with surface and material characterization for Nb films produced on various substrates, monocrystalline and polycrystalline as well as amorphous. A progress report on work on NbTiN and AlN based multilayer structures will also be presented.
Date: September 1, 2011
Creator: Valente-Feliciano, A -M; Reece, C E; Spradlin, J K; Xiao, B; Zhao, X; Gu, Diefeng et al.
Partner: UNT Libraries Government Documents Department

Electronic structure of fully epitaxial Co2TiSn thin films

Description: In this article we report on the properties of thin films of the full Heusler compound Co{sub 2}TiSn prepared by DC magnetron co-sputtering. Fully epitaxial, stoichiometric films were obtained by deposition on MgO (001) substrates at substrate temperatures above 600 C. The films are well ordered in the L2{sub 1} structure, and the Curie temperature exceeds slightly the bulk value. They show a significant, isotropic magnetoresistance and the resistivity becomes strongly anomalous in the paramagnetic state. The films are weakly ferrimagnetic, with nearly 1 {mu}{sub B} on the Co atoms, and a small antiparallel Ti moment, in agreement with theoretical expectations. From comparison of x-ray absorption spectra on the Co L{sub 3,2} edges, including circular and linear magnetic dichroism, with ab initio calculations of the x-ray absorption and circular dichroism spectra we infer that the electronic structure of Co{sub 2}TiSn has essentially non-localized character. Spectral features that have not been explained in detail before, are explained here in terms of the final state band structure.
Date: October 28, 2010
Creator: Meinert, Markus; Schmalhorst, Jan; Wulfmeier, Hendrik; Reiss, Gunter; Arenholz, Elke; Graf, Tanja et al.
Partner: UNT Libraries Government Documents Department

Visualization of Trajectories of Electron Beams Emitted by an IonSource with Closed Electron Drift

Description: Trajectories of electron beams emitted by an ion source with an anode layer and Hall electron closed drift orbits were visualized using light emission from a working gas excited by electrons. Gas discharge of magnetron type, arising in the beam drift region under the influence of an electric field of a target bias potential, was visualized.
Date: October 1, 2007
Creator: Institue of Physics, National Academy of Sciences of Ukraine; Brown, Ian G.; Bordenjuk, Ian V.; Panchenko, Oleg A.; Sologub, Sergei V. & Brown, Ian G.
Partner: UNT Libraries Government Documents Department

The FNAL injector upgrade

Description: The present FNAL H{sup -} injector has been operational since the 1970s and consists of two magnetron H{sup -} sources and two 750 keV Cockcroft-Walton Accelerators. In the upgrade, both slit-type magnetron sources will be replaced with circular aperture sources, and the Cockcroft-Waltons with a 200 MHz RFQ (radio frequency quadrupole). Operational experience at BNL (Brookhaven National Laboratory) has shown that the upgraded source and RFQ will be more reliable, improve beam quality and require less manpower than the present system. The present FNAL (Fermi National Accelerator Laboratory) injector has been operational since 1978 and has been a reliable source of H{sup -} beams for the Fermilab program. At present there are two Cockcroft-Walton injectors, each with a magnetron H{sup -} source with a slit aperture. With these two sources in operation, the injector has a reliability of better than 97%. However, issues with maintenance, equipment obsolescence, increased beam quality demands and retirement of critical personnel, have made it more difficult for the continued reliable running of the H{sup -} injector. The recent past has also seen an increase in both downtime and source output issues. With these problems coming to the forefront, a new 750 keV injector is being built to replace the present system. The new system will be similar to the one at BNL (Brookhaven National Laboratory) that has a similar magnetron source with a round aperture and a 200MHz RFQ. This combination has been shown to operate extremely reliably.
Date: March 1, 2011
Creator: Tan, C.Y.; Bollinger, D.S.; Duel, K.L.; Lackey, J.R.; Pellico, W.A. & /Fermilab
Partner: UNT Libraries Government Documents Department

Plasma&quot;anti-assistance&quot; and&quot;self-assistance&quot; to high power impulse magnetron sputtering

Description: A plasma assistance system was investigated with the goal to operate high power impulse magnetron sputtering (HiPIMS) at lower pressure than usual, thereby to enhance the utilization of the ballistic atoms and ions with high kinetic energy in the film growth process. Gas plasma flow from a constricted plasma source was aimed at the magnetron target. Contrary to initial expectations, such plasma assistance turned out to be contra-productive because it led to the extinction of the magnetron discharge. The effect can be explained by gas rarefaction. A better method of reducing the necessary gas pressure is operation at relatively high pulse repetition rates where the afterglow plasma of one pulse assists in the development of the next pulse. Here we show that this method, known from medium-frequency (MF) pulsed sputtering, is also very important at the much lower pulse repetition rates of HiPIMS. A minimum in the possible operational pressure is found in the frequency region between HiPIMS and MF pulsed sputtering.
Date: January 30, 2009
Creator: Anders, Andre & Yushkov, Georgy Yu.
Partner: UNT Libraries Government Documents Department

Residual stress measurement and microstructural characterization of thick beryllium films

Description: Beryllium films are synthesized by a magnetron sputtering technique incorporating in-situ residual stress measurement. Monitoring the stress evolution in real time provides quantitative through-thickness information on the effects of various processing parameters, including sputtering gas pressure and substrate biasing. Specimens produced over a wide range of stress states are characterized via transmission and scanning electron microscopy, and atomic force microscopy, in order to correlate the stress data with microstructure. A columnar grain structure is observed for all specimens, and surface morphology is found to be strongly dependent on processing conditions. Analytical models of stress generation are reviewed and discussed in terms of the observed microstructure.
Date: February 11, 2008
Creator: Detor, A; Wang, M; Hodge, A M; Chason, E; Walton, C; Hamza, A V et al.
Partner: UNT Libraries Government Documents Department

New developments with H-sources.

Description: Existing spallation neutron source upgrades, planned spallation neutron sources, and high-energy accelerators for particle physics place demanding requirements on the Hsources. These requirements ask for increased beam currents and duty factor (df) while generally maintaining state-of-the art H' source emittance. A variety of H sources are being developed to address these challenges. These include volume sources with and without the addition of cesium for enhanced He production, increased df cesiated H' Penning and magnetron sources, and cesiated surface converter H- sources. Research on surface films of tantalum metal for enhanced volume H- production is also being studied. Innovative plasma production techniques to address the longer df requirement without sacrificing H- source reliability and liktime will be reviewed. The physical bases, the goals, and perceived challenges will be discussed.
Date: January 1, 2002
Creator: Sherman, Joseph D. & Rouleau, G. (Gary)
Partner: UNT Libraries Government Documents Department

Measurements of the optical constants of scandium in the 50-1300eV range.

Description: Scandium containing multilayers have been produced with very high reflectivity in the soft x-ray spectrum. Accurate optical constants are required in order to model the multilayer reflectivity. Since there are relatively few measurements of the optical constants of Scandium in the soft x-ray region we have performed measurements over the energy range of 50-1,300 eV. Thin films of Scandium were deposited by ion-assisted magnetron sputtering at Linkoping University and DC Magnetron sputtering at CXRO. Transmission measurements were performed at the Advanced Light Source beamline 6.3.2. The absorption coefficient was deduced from the measurements and the dispersive part of the index of refraction was obtained using the Kramers-Kronig relation. The measured optical constants are used to model the near-normal incidence reflectivity of Cr/Sc multilayers near the Sc L{sub 2,3} edge.
Date: October 3, 2004
Creator: Aquila, A.L.; Salmassi, F.; Gullikson, E.M; Eriksson, F. & Birch, J.
Partner: UNT Libraries Government Documents Department

Transistor Driven Beam Switching Tube Decade Counter

Description: An electrical readout, decade counter employing a magnetron beam switching tube with transitor drive is described. Double pulse resolution is one microsecond. The unit will accept a variety of transitor types and will tolerate supply voltage variation of plus or minus 20% at ambient temperatures up to 60 deg C. A neon indicator is driven without the use of additional transitors. A readout circuit for printer on punched paper tape is presented. (auth)
Date: August 11, 1959
Creator: Graham, R. H.
Partner: UNT Libraries Government Documents Department