Ebeam 2010 featured 19 speakers from around the world and was attended by 60 companies from Brazil, Canada, Czech Republic, Kazakhstan, Russia, Ukraine and the United States. Ebeam is a biannual event that first convened in Reno, Nev., in 1983.

The conference, which has become the signature event for this technology, opened with a presentation by H. Padamsee of Cornell University titled “Continuing Niobium Needs for Accelerator Cavities, Present and Future.” He began by stating that 40 tons of Nb cavities have been ordered for upgrades of the CEBAF accelerator in Virginia, the Spallation Neutron Source (SNS) in Tennessee and the new European X-Ray Free-Electron Laser (XCEL) in Hamburg, Germany.

    With the success of SNS high-intensity proton accelerators for European Spallation Source (ESS) and proton injection upgrades at Fermi Lab in Illinois and CERN in Switzerland, near-future market demand will be 50 tons. Together with other projects this demand could go up to 150 tons. The far-future scenario will depend strongly if the LHC collider now operating at CERN will reveal dramatic new finds and could generate the need for another 500 tons of high-purity Nb in the next six years. The cost of Nb will play an important role. All of these requirements are met with existing technology. If an advanced technology such as multi-wire ingot slicing (Fig. 1 - online) can be achieved to produce material for cavities, substantial savings could result.

High-Heat Studies

The next three papers dealt with high-heat furnace studies, guns as a source of surface heat load and high-heat-flux experiments.

     The first paper, by D.L. Youchison, describes Sandia National Laboratories’ high-heat-flux electron-beam experiments for the ITER. They applied 12,000 thermal fatigue cycles at 0.75 MW/m² and higher to identify performance limitations. Their dual gun von Ardenne EB system, EB 1200, used to perform these high-flux tests was described as was the use of thermal imaging for safety monitoring and data acquisitions.

    The second paper, by V. Kuznetsov from Russia’s D.V. Efremov Institute and M. Neumann of 2A in Germany, was titled “Melting Electron-Beam Guns Used as a Source of Surface Heat Load During ITER PFC Testing.” Various power guns were used, but the most recent tests were performed with the EB 800/60 von Ardenne melting electron gun (Fig. 2). The purpose of the facility is to test full-scale prototypes of the ITER director plasma-facing components as well as to test PFC during their serial production.

    The third paper, “High Heat Flux Testing of Components for Future Fusion Devices by Means of the Facility JUDITH 2,” was written by A. Schmidt of Germany’s Forschungszentrum and EURATOM-Association (Fig. 3). First wall elements of future fusion reactors like ITER or DEMO will suffer extremely high heat fluxes up to 20 MW/m². In order to assure the performance of these components, EB facilities are used to simulate these high heat loads, specifically details on beam diameter diagnostics, simple beam scanning methods and calibration techniques. The generation of heating beam pattern is based on freely programmable figures, which consist of points with X and Y coordinates and different dwell times of the beam. The paper is a summary of all EB parameters of the maximum 200-kW beam power used in these simulations with different materials and geometries.

Melting

The next series of papers were devoted to melting, beginning with “Refining of Silicon by Electron Melting” by C. Lehnert of ALD Vacuum Technologies and B. Scheffel of the Frauenhofer Institute for EB and Plasma Technology. High demand for solar-grade silicon by the photovoltaic (PV) industry requires development of a new and cost-saving process for the purification of metallurgical and upgraded metallurgical silicon. The authors collaborated on the potential of EB refining for the production of solar-grade silicon. In the study, 99.97% silicon samples were melted and refined in an EB test furnace in a graphite crucible using a cold-cathode EB source, and 99.999 purity material was obtained. Results of this study with the novel ALD 400 source (Fig. 4) were presented in detail.

    D. Maijer presented a paper co-authored by S. Cockroft and S. Fox of the University of British Columbia titled “Evaporation During EB Casting of Ti6Al4V.” The presence of voids or loss of chemistry control at the end of the EBCHR casting process to produce Ti6Al4V ingots may result in significant productivity loss as the top of the ingot must be removed. Raising the shrinkage-void location can be achieved by hot topping after the termination of casting. This, however, can result in significant Al evaporation, leading to off-spec chemistry. A mathematical model of the hot top stage during EB ingot and slab casting of this alloy has been developed. The model solves the thermal-flow problem. Analytical data is generated to validate the model under various hot-topping conditions.

    E. Copland of Alvac (Monroe, N.C.) presented a paper titled “Improved measurements of the Vaporization Behavior of the Al(1) + Al₂O₃ System.” There appears to be little agreement in data on the vaporization of Al. Al₂O₃ seems to be the ideal container for Al, but studies indicate interpretation of results from vaporization studies have been hindered by Al₂O₃ condensation. The presence of Al₂O, the dominant vapor at temperatures around 1600°, does not appear accurately accounted for in early studies. The vaporization studies are reviewed, and the ramification of improved thermodynamic data on the understanding of multi-component solution behavior and vaporization from vacuum conditions encountered during EB melting are discussed.

    S. Dobrussin of Ulba Metallurgical Plant (Kazakhstan) shared the podium with M. Neumann of von Ardenne Anlagentechnik for a presentation titled “New EB Melting Capability of ULBA.” It is a 1.600-MW furnace (Fig. 5 - online) powered by two 800-kW von Ardenne electron guns. It is complementary to older equipment at Ulba that processes Ta and Ti among other materials.

    The next speaker, S. Ladokhin and Associates from the Physico Technological Institute of Metals and Alloys (PITMA) in Kiev, Ukraine, presented “New Electron Beam Technologies and Equipment for Zirconium Tube Billet Manufacture.” The use of high-voltage glow-discharge guns appears the most appropriate since they were developed to perform in processes with high gas-generation materials such as Zr. The specific molds developed for this purpose are also discussed.

    U. Biebricher of ALD next discussed the wide range of EB services available at the company. They include conventional drip melting, horizontal and vertical cold-hearth refining, and floating-zone refining and casting. He summed up by stating that no other melting technology can provide such flexibility.

    The last melting paper, by Biebricher and J. Flinspach of ALD, reported on the melting and process development services with an in-house ALD furnace on a toll basis (Fig. 6). They are capable of processing a variety of refractory metals and alloys from small buttons to larger ingots.

General Topics

A session on a range of EB-related topics rounded out the conference. It began with a paper presented by M. Merkel on work done by associates (including Merkel) from FOCUS GmbH, Fraunhofer Institute for Electron Beam and Plasma Technology and the Institute of Scientific Instruments of the ASCR. It discussed the electron beam as a tool of both nano-science and micro-technology from UHV evaporation to micro EB surface modification. The presentation started with a discussion of EFM3, an ultrahigh EB evaporator claimed to be the standard of the industry, and ended with a desktop-sized instrument that looks more like an electron microscope than a welder. It is capable of tackling a large range of micro joining and surface-modification tasks. Both the instrument and selected applications were discussed.

    Aren Paster and associates from Zak Inc. (Troy, N.Y.) discussed flow optimization for drilled water-passage copper products. These become parts of EB and other types of melting furnaces. Fig. 7 shows such components.

    G. Schubert of PTR Precision Technologies reviewed EB welding, its applications and recent developments in the next presentation.

    R. Guenther of NWL (Bordentown, N.J.) looked at high-voltage, high-frequency power supplies for EB processes. High-frequency, high-voltage power supplies have been used for more than 10 years in electrostatic precipitators with over 1,000 operational units with ratings up to 120 kW/unit (Fig. 8). In the past year, NWL has expanded this technology to the EB market, specifically in curing, coating and melting applications. Power supplies act like a current source, they parallel very easily and handle current without disruption. Modules of these power supplies allow systems up to 600 kW. This paper discusses the advantages of these power supplies.

    The next paper by F. Fischer and U. Hampel of FZD Research Center and G. Mattausch and F-H. Roegner of Fraunhofer Institute for Electron Beam and Plasma Technology, both in Germany, reported on ultra-fast CT X-ray imaging for dynamic process visualization in research and industry. There is growing demand for rapid high-resolution spatial imaging of objects and processes. X-ray computer tomography (CT) can, in principle, be used as a tool in their visualization tasks. Units developed for medical imaging are too slow for technical applications due to their mechanical inertia. FZD has recently carried out a number of projects to develop fast X-ray CT devices based on fast scanning, high-power-density EB for the tomography of technical two-phase flows in papers. The EB source of the scanner operates at 150 KV and focuses power of 10 KHZ to a 1-mm-diameter spot.

G. Mattausch of the Fraunhofer Institute, next presented a paper titled “Cold Cathode Electron Beam Sources for High-Rate PVD and Beyond.” Established designs of high-power EB sources based on thermionic emitters as well as their supply and control systems are complex and expensive, preventing their applications in many thin-film processes. Alternative EB sources with cold cathodes have recently attracted much interest because of their prospects as an economic beam source for a broader spectrum of applications, including PVD. An efficient and single cold-cathode, axial-type electron source has been developed and tested at FEP. Inside this gun, a high-voltage glow discharge (HVGD) is sustained. In addition to simplified mechanical designs and electrical supply circuitry, cost reduction results also from the fact that HVGD’s beam source needs no differential HV pumping and can be operated in a wide range of acceleration voltages. All of these issues have been addressed, and we have a report of coating plastic substrates with a thick copper layer utilizing a 30KV/60KW HVGD EB system (Fig. 9).

            The last paper in the conference by L. DeMoura and C. Sousa of CBMM (Araxa, Brazil) summarized highlights of Nb production since its first EB furnace in 1989 and their second furnace in 2003. The Nb ingot produced (Fig. 10) goes to a variety of applications, including extra-pure Nb for superconducting cavities and Nb-Ti for superconducting magnets and sputtering targets. The paper revisits the fully integrated CBMM process for Nb production and the accumulated experience of operating a 500-kW and a 1.8-megawatt EB furnace. IH

For more information: The proceedings of EB2010 are available as a CD from von Ardenne Anlagentechnik. Mr. Bakish is principal of Bakish Materials Corp., P.O. Box 148, Englewood, N.J. 07631; tel: 210-567-5873; fax: 201-567-6684; e-mail: bakishmat@aol.com