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A HIGH-POWER L-BAND RF WINDOW

Description: This paper discusses the design, fabrication and testing of a high power alumina disk window in WR1500 waveguide at L Band, suitable for use in the NLC damping ring RF cavities at 714 MHz and the LEDA Accelerator at 700 MHz. The design is based on the fabrication methods used for the successful PEP-II cavity windows. Four prototype windows at 700 MHz have been produced by LBNL for testing at LANL. The RF design and simulation using MAFIA, laboratory cold test measurements, fabrication methods and preliminary high power test results are discussed.
Date: May 1, 2001
Creator: RIMMER, R.; KOEHLER, G. & AL, ET
Partner: UNT Libraries Government Documents Department

Design of multi-megawatt actively cooled beam dumps for the Neutral-Beam Engineering Test Facility

Description: The Neutral Beam Engineering Test Facility will test Neutral Beam Sources up to 170 keV, 65 Amps, with 30 second beam-on times. For this application actively cooled beam dumps for both the neutral and ionized particles will be required. The dumps will be able to dissipate a wide range of power density profiles by utilizing a standard modular panel design which is incorporated into a moveable support structure. The thermal hydraulic design of the panels permit the dissipation of 2 kW/cm/sup 2/ anywhere on the panel surface. The water requirements of the dumps are optimized by restricting the flow to panel sections where the heat flux falls short of the design value. The mechanical design of the beam-dump structures is described along with tests performed on a prototype panel. The prototype tests were performed on two different panel designs, one manufactured by Mc Donnell Douglas (MDAC) the other by United Technologies (UT). The dissipation capabilities of the panels were tested at the critical regions to verify their use in the beam dump assemblies.
Date: October 1, 1981
Creator: Paterson, J.A.; Koehler, G. & Wells, R.P.
Partner: UNT Libraries Government Documents Department

Development of large rectangular ceramic insulators for ion accelerators for the neutral-beam program

Description: The need for structures that are resistant to damage for 14 MeV neutrons, are bakeable, and that can be closely packed together, has resulted in the intensive development of rectangular brazed ceramic insulators for ion accelerators. The development of two candidate materials, machinable glass ceramic and alumina, is described along with the ceramic-to-metal brazing techniques developed for each material. The microstructures of the brazed joints are examined and the results of microprobe studies presented. It has been found that the surfaces produced by different machining methods have a significant effect on the strength of brazed joints to the machinable glass ceramic. Lapped surfaces have given bond strengths up to three times those produced with other surfaces. Successful full-size brazes have been realized between alumina and titanium and between machinable glass and titanium. Vacuum tight joints between machinable glass and titanium have not been reliably achieved and more work is needed before brazing techniques to this promising new material are fully understood.
Date: March 1, 1979
Creator: Paterson, J.A.; Koehler, G.W. & Duffy, T.J.
Partner: UNT Libraries Government Documents Department

ON FABRICATION AND BRAZING OF 15A, 120 keV CONTINUOUS DUTY ACCELERATOR GRID ASSEMBLIES

Description: The development of high intensity neutral beam injectors at the Lawrence Berkeley Laboratory has progressed from relatively low duty cycle, low energy devices to the next generation of continuous duty high energy units. The earlier pulsed versions were designed with edge cooled grid structures described ·in a previous publication. The prerequisites set by the higher duty cycle devices no longer allow the edge cooling methods to be employed. Hollow molybdenum grid rails with deionized cooling water flowing at pressures of approximately 1.73 x 10{sup 6}Pa (250 PSI) at from 1.135 to 1.89 liters per minute (.3 to .5 GPM) are brazed to Type 304L stainless steel rail holders.
Date: May 1, 1980
Creator: Biagi, L.A.; Koehler, G.W. & Paterson, J.A.
Partner: UNT Libraries Government Documents Department

Adjustable rare earth quadrupole drift tube magnets

Description: A prototype permanent-magnet drift tube quadrupole with adjustable field strength has been constructed and tested. The magnet uses iron pole pieces to provide the required field shape along with rare earth permanent-magnet material (samarium cobalt) to energize the magnet. A unique feature of the configuration is the adjustability of the field, accomplished by rotating the outer rings consisting of permanent magnets and iron. In contrast with a previous prototype magnet, this new design uses ball bearings in place of slide bearings to eliminate potential failures. The rotation is now achieved with a bevel gear mechanism. The prototype design also incorporates a new drift tube shell vacuum seal to allow easy disassembly. Tests were made of the magnetic properties and the mechanical performance of this magnet. Field errors are extremely small, and the magnet passed an accelerated ten year lifetime test. It is planned to use this type of magnet to replace 24 of the SuperHILAC prestripper drift tubes.
Date: March 1, 1987
Creator: Feinberg, B.; Tanabe, J.; Halbach, K.; Koehler, G. & Green, M.I.
Partner: UNT Libraries Government Documents Department

Design and fabrication of an actively cooled Langmuir probe for long pulse applications

Description: The details of the mechanical design and fabrication for a Langmuir Probe for the continuous monitoring of plasma density are given. The probe was designed for use as a diagnostic tool in the development of long pulse positive ion plasma sources for use on neutral beam systems. The essential design feature of this probe is the incorporation of two electrically isolated cooling water circuits which actively cool the probe tip and probe jacket. The electrical isolation is required to prevent drain currents from the probe body disturbing the measurement of the probe tip current and thereby the plasma density measurement. The successful realization of the design requires precision components and vacuum tight ceramic to refractory metal brazes. To date this design has successfully operated in steady-state in plasma densities up to 250 mA/cmS and surface heat fluxes of 25 W/cmS.
Date: November 1, 1985
Creator: Paterson, J.A.; Biagi, L.A.; Ehlers, K.W. & Koehler, G.W.
Partner: UNT Libraries Government Documents Department

Design, fabrication and operation of the mechanical systems for the Neutral Beam Engineering Test Facility

Description: The Neutral Beam Engineering Test Facility (NBETF) at Lawrence Berkeley Laboratory (LBL) is a National Test Facility used to develop long pulse Neutral Beam Sources. The Facility will test sources up to 120 keV, 50 A, with 30 s beam-on times with a 10% duty factor. For this application, an actively cooled beam dump is required and one has been constructed capable of dissipating a wide range of power density profiles. The flexibility of the design is achieved by utilizing a standard modular panel design which is incorporated into a moveable support structure comprised of eight separately controllable manipulator assemblies. A unique neutralizer design has been installed into the NBETF beamline. This is a gun-drilled moveable brazed assembly which provides continuous armoring of the beamline near the source. The unit penetrates the source mounting valve during operation and retracts to permit the valve to close as needed. The beamline is also equpped with many beam scraper plates of differing detail design and dissipation capabilities.
Date: December 1, 1983
Creator: Paterson, J.A.; Biagi, L.A.; Fong, M.; Koehler, G.W.; Low, W.; Purgalis, P. et al.
Partner: UNT Libraries Government Documents Department

Mechanical design and construction of a 200 mA, 100 keV, dc, negative ion accelerator

Description: A volume production source and a 100 keV, dc, accelerator together with an additional, modular, 100 keV, electro static focused accelerator provide a starting point for a high energy H/sup -//D/sup -/ beam-line (200 keV to 800 keV), intended for fusion energy applications. The 100 keV accelerator tests started in June 1987. The mechanical design and construction of the accelerator is described. 3 refs., 8 figs.
Date: October 1, 1987
Creator: Purgalis, P.; Anderson, O.A.; Cooper, W.S.; Cummings, C.; Koehler, G.W.; Matuk, C.A. et al.
Partner: UNT Libraries Government Documents Department

RF cavity R&D at LBNL for the NLC Damping Rings,FY2000/2001

Description: This report contains a summary of the R&D activities at LBNL on RF cavities for the NLC damping rings during fiscal years 2000/2001. This work is a continuation of the NLC RF system R&D of the previous year [1]. These activities include the further optimization and fine tuning of the RF cavity design for both efficiency and damping of higher-order modes (HOMs). The cavity wall surface heating and stresses were reduced at the same time as the HOM damping was improved over previous designs. Final frequency tuning was performed using the high frequency electromagnetic analysis capability in ANSYS. The mechanical design and fabrication methods have been developed with the goals of lower stresses, fewer parts and simpler assembly compared to previous designs. This should result in substantial cost savings. The cavity ancillary components including the RF window, coupling box, HOM loads, and tuners have been studied in more detail. Other cavity options are discussed which might be desirable to either further lower the HOM impedance or increase the stored energy for reduced transient response. Superconducting designs and the use of external ''energy storage'' cavities are discussed. A section is included in which the calculation method is summarized and its accuracy assessed by comparisons with the laboratory measurements of the PEP-II cavity, including errors, and with the beam-sampled spectrum.
Date: June 1, 2001
Creator: Rimmer, R.A.; Atkinson, D.; Corlett, J.N.; Koehler, G.; Li, D.; Hartman, N. et al.
Partner: UNT Libraries Government Documents Department

RF cavity R&D at LBNL for the NLC damping rings, FY1999

Description: This report contains a summary of the R&D activities at LBNL on RF cavities for the NLC damping rings during fiscal year19999. These activities include the optimization of the RF design for both efficiency and damping of higher-order (HOMs), by systematic study of the cavity profile, the effect of the beam pipe diameter, nosecone angle and gap, the cross section and position of the HOM damping waveguides and the coupler. The effect of the shape of the HOM waveguides and their intersection with the cavity wall on the local surface heating is also an important factor, since it determines the highest stresses in the cavity body. This was taken into account during the optimization so that the stresses could be reduced at the same time as the HOP damping was improved over previous designs. A new method of calculating the RF heating was employed, using a recently released high frequency electromagnetic element in ANSYS. This greatly facilitates the thermal and stress analysis of the design and fabrication methods have been developed with the goals of lower stresses, fewer parts and simpler assembly compared to previous designs. This should result in substantial cost savings. Preliminary designs are described for the cavity ancillary components including the RF window, HOM loads, and tuners. A preliminary manufacturing plan is included, with an initial estimate of the resource requirements. Other cavity options are discussed which might be desirable to either lower the R/Q, for reduced transient response, or lower the residual HOM impedance to reduce coupled-bunch growth rates further still.
Date: November 1, 1999
Creator: Rimmer, R.A.; Corlett, J.N.; Koehler, G.; Li, D.; Hartman, N.; Rasson, J. et al.
Partner: UNT Libraries Government Documents Department

Mechanical design and fabrication of the transverse field focusing (TFF) matching/pumping section for negative ion based neutral beam systems

Description: A negative ion based neutral beam injection system is under development as proof-of-principle demonstration of a radiation-hardened beamline. The beamline consists of a source, a pre-accelerator, a matching/pumping (M/P) section, and an accelerator. The function of the M/P section is to provide vacuum pumping, to remove electrons, to provide beam edge confinement, to compress the beam thickness to match the requirements of the accelerator, and to transport the 1A, 80 keV, 25 cm high H ribbon beam to the accelerator entrance. Details of the design and fabrication of the M/P section are presented. The M/P section has eight separate, high voltage electrodes forming an ''S'' shaped beam path. Electrons are removed by the electron trap in this path. Beam edge confinement and thickness compression is accomplished by the curvature and face contour of the electrodes. Design heat loads are described. Electrode fabrication is discussed, and the cryopumps used are described. (LEW)
Date: November 1, 1985
Creator: Purgalis, P.; Anderson, O.A.; Koehler, G.W.; Maruyama, Y.; Matuk, C.A.; Owren, H.M. et al.
Partner: UNT Libraries Government Documents Department

Mechanical baseline design of the common long pulse source for the neutral beam systems of TFTR, Doublet III-D, and MFTF-B

Description: The Common Long Pulse Source (CLPS) is designed to meet the differing long pulse neutral beam requirements of TFTR, Doublet III-D, and MFTF-B. The mechanical baseline design to meet these requirements is described along with supporting engineering data collected during the testing of the prototype LBL 10 x 40 Long Pulse Accelerator (LPA) and the Long Pulse Plasma Source (LPS). The CLPS is a scaled up design of the LPA and LPS and can be configured for 120 keV, 70 A D/sub 2/ non-focused, and, 80 keV, 80 A H/sub 2/ or 50 A D/sub 2/ with a 10 m focal length. The two configurations use identical major components, such as accelerator grids, supporting structures, insulators and plasma sources. Ion beam optics are analytically modeled and the results are presented along with the electric field gradients and thermal calculations for various components. A low technology plasma source back plate electron dump design has been adopted. A full scale model of CLPS was constructed, and the baseline design has been transferred to industry. 7 refs., 5 figs.
Date: November 1, 1985
Creator: Paterson, J.A.; Chan, C.F.; Fong, M.Y.; Koehler, G.W.; Sullivan, J.S.; Wells, R.P. et al.
Partner: UNT Libraries Government Documents Department

PEP-II RF cavity revisited

Description: This report describes the results of numerical simulations of the PEP-II RF cavity performed after the completion of the construction phase of the project and comparisons are made to previous calculations and measured results. These analyses were performed to evaluate new calculation techniques for the HOM distribution and RF surface heating that were not available at the time of the original design. These include the use of a high frequency electromagnetic element in ANSYS and the new Omega 3P code to study wall losses, and the development of broadband time domain simulation methods in MAFIA for the HOM loading. The computed HOM spectrum is compared with cavity measurements and observed beam-induced signals. The cavity fabrication method is reviewed, with the benefit of hindsight, and simplifications are discussed.
Date: November 1, 1999
Creator: Rimmer, R.A.; Koehler, G.; Li, D.; Hartman, N.; Folwell, N.; Hodgson, J. et al.
Partner: UNT Libraries Government Documents Department