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Development of a 2 MW CW Waterload for Electron Cyclotron Heating Systems

Description: Calabazas Creek Research, Inc. developed a load capable of continuously dissipating 2 MW of RF power from gyrotrons. The input uses HE11 corrugated waveguide and a rotating launcher to uniformly disperse the power over the lossy surfaces in the load. This builds on experience with a previous load designed to dissipate 1 MW of continuous RF power. The 2 MW load uses more advanced RF dispersion to double the capability in the same size device as the 1 MW load. The new load reduces reflected power from the load to significantly less than 1 %. This eliminates requirements for a preload to capture reflected power. The program updated control electronics that provides all required interlocks for operation and measurement of peak and average power. The program developed two version of the load. The initial version used primarily anodized aluminum to reduce weight and cost. The second version used copper and stainless steel to meet specifications for the ITER reactor currently under construction in France. Tests of the new load at the Japanese Atomic Energy Agency confirmed operation of the load to a power level of 1 MW, which is the highest power currently available for testing the load. Additional tests will be performed at General Atomics in spring 2013. The U.S. ITER organization will test the copper/stainless steel version of the load in December 2012 or early in 2013. Both loads are currently being marketed worldwide.
Date: November 9, 2012
Creator: R. Lawrence,Ives; Mizuhara, Maxwell; Collins, George; Neilson, Jeffrey & Borchard, Philipp
Partner: UNT Libraries Government Documents Department

Development of a 402.5 MHz 140 kW Inductive Output Tube

Description: This report contains the results of Phase I of an SBIR to develop a Pulsed Inductive Output Tube (IOT) with 140 kW at 400 MHz for powering H-proton beams. A number of sources, including single beam and multiple beam klystrons, can provide this power, but the IOT provides higher efficiency. Efficiencies exceeding 70% are routinely achieved. The gain is typically limited to approximately 24 dB; however, the availability of highly efficient, solid state drivers reduces the significance of this limitation, particularly at lower frequencies. This program initially focused on developing a 402 MHz IOT; however, the DOE requirement for this device was terminated during the program. The SBIR effort was refocused on improving the IOT design codes to more accurately simulate the time dependent behavior of the input cavity, electron gun, output cavity, and collector. Significant improvement was achieved in modeling capability and simulation accuracy.
Date: May 9, 2012
Creator: Ives, R. Lawrence & Michael Read, Robert Jackson
Partner: UNT Libraries Government Documents Department

A 350 MHz, 200 kW CW, Multiple Beam Inductive Output Tube - Final Report

Description: This program developed a 200 kW CW, 350 MHz, multiple beam inductive output tube (MBIOT) for driving accelerator cavities. The MBIOT operates at 30 kV with a gain of 23 dB. The estimated efficiency is 70%. The device uses seven electron beams, each transmitting 1.4 A of current. The tube is approximately six feet long and weighs approximately 400 lbs. The prototype device will be evaluated as a potential RF source for the Advanced Photon Source at Argonne National Laboratory (ANL). Because of issues related to delivery of the electron guns, it was not possible to complete assembly and test of the MBIOT during the Phase II program. The device is being completed with support from Calabazas Creek Research, Inc., Communications & Power Industries, LLC. and the Naval Surface Weapons Center (NSWC) in Dahlgren, VA. The MBIOT will be initially tested at NSWC before delivery to ANL. The testing at NSWC is scheduled for February 2013.
Date: November 28, 2012
Creator: Ives, R. Lawrece; Collins, George; Read, David Marsden Michael; Eisen, Edward & Takuchi Kamura, Philipp Borchard
Partner: UNT Libraries Government Documents Department

Integration of Heat Transfer, Stress, and Particle Trajectory Simulation

Description: Calabazas Creek Research, Inc. developed and currently markets Beam Optics Analyzer (BOA) in the United States and abroad. BOA is a 3D, charged particle optics code that solves the electric and magnetic fields with and without the presence of particles. It includes automatic and adaptive meshing to resolve spatial scales ranging from a few millimeters to meters. It is fully integrated with CAD packages, such as SolidWorks, allowing seamless geometry updates. The code includes iterative procedures for optimization, including a fully functional, graphical user interface. Recently, time dependent, particle in cell capability was added, pushing particles synchronically under quasistatic electromagnetic fields to obtain particle bunching under RF conditions. A heat transfer solver was added during this Phase I program. Completed tasks include: (1) Added a 3D finite element heat transfer solver with adaptivity; (2) Determined the accuracy of the linear heat transfer field solver to provide the basis for development of higher order solvers in Phase II; (3) Provided more accurate and smoother power density fields; and (4) Defined the geometry using the same CAD model, while maintaining different meshes, and interfacing the power density field between the particle simulator and heat transfer solvers. These objectives were achieved using modern programming techniques and algorithms. All programming was in C++ and parallelization in OpenMP, utilizing state-of-the-art multi-core technology. Both x86 and x64 versions are supported. The GUI design and implementation used Microsoft Foundation Class.
Date: May 17, 2012
Creator: Bui, Thuc; Read, Michael & ives, Lawrence
Partner: UNT Libraries Government Documents Department

An Advanced simulation Code for Modeling Inductive Output Tubes

Description: During the Phase I program, CCR completed several major building blocks for a 3D large signal, inductive output tube (IOT) code using modern computer language and programming techniques. These included a 3D, Helmholtz, time-harmonic, field solver with a fully functional graphical user interface (GUI), automeshing and adaptivity. Other building blocks included the improved electrostatic Poisson solver with temporal boundary conditions to provide temporal fields for the time-stepping particle pusher as well as the self electric field caused by time-varying space charge. The magnetostatic field solver was also updated to solve for the self magnetic field caused by time changing current density in the output cavity gap. The goal function to optimize an IOT cavity was also formulated, and the optimization methodologies were investigated.
Date: April 27, 2012
Creator: Bui, Thuc & Ives, R. Lawrence
Partner: UNT Libraries Government Documents Department

Improved Space Charge Modeling for Simulation and Design of Photoinjectors

Description: Photoinjectors in advanced high-energy accelerators reduce beam energy spreads and enhance undulator photon fluxes. Photoinjector design is difficult because of the substantial differences in time and spatial scales. This Phase I program explored an innovative technique, the local Taylor polynomial (LTP) formulation, for improving finite difference analysis of photoinjectors. This included improved weighting techniques, systematic formula for high order interpolation and electric field computation, and improved handling of space charge. The Phase I program demonstrated that the approach was powerful, accurate, and efficient. It handles space charge gradients better than currently available technology.
Date: April 19, 2010
Creator: Robert H. Jackson, Thuc Bui, John Verboncoeur
Partner: UNT Libraries Government Documents Department

A 200 MHz 35 MW Multiple Beam Klystron for Accelerator Applications Final Report

Description: Calabazas Creek Research, Inc. (CCR) performed initial development of a compact and reliable 35 MW, multiple beam klystron (MBK) at 200 MHz with a pulse length of 0.125 ms and a 30 Hz repetition rate. The device was targeted for acceleration and ionization cooling of a muon collider, but there are several other potential applications in this frequency range. The klystron uses multiple beams propagating in individual beam tunnels to reduce space charge and allow reduction in the accelerating voltage. This allows a significant reduction in length over a single beam source. More importantly this allows more efficient and less expensive power supplies. At 200 MHz, the interaction circuit for a single beam klystron would be more than six meters long to obtain 50% efficiency and 50 dB gain. This would require a beam voltage of approximately 400 kV and current of 251 A for a microperveance of 1.0. For an eight beam MBK with the same beam perveance, a three meter long interaction circuit achieves the same power and gain. Each beam operates at 142 kV and 70A. The Phase I demonstrated that this device could be fabricated with funding available in a Phase II program and could achieve the program specifications.
Date: November 28, 2011
Creator: Ives, R. Lawrence; Read, Michael; Ferguson, Patrick & Marsden, David
Partner: UNT Libraries Government Documents Department

BOA, Beam Optics Analyzer A Particle-In-Cell Code

Description: The program was tasked with implementing time dependent analysis of charges particles into an existing finite element code with adaptive meshing, called Beam Optics Analyzer (BOA). BOA was initially funded by a DOE Phase II program to use the finite element method with adaptive meshing to track particles in unstructured meshes. It uses modern programming techniques, state-of-the-art data structures, so that new methods, features and capabilities are easily added and maintained. This Phase II program was funded to implement plasma simulations in BOA and extend its capabilities to model thermal electrons, secondary emissions, self magnetic field and implement a more comprehensive post-processing and feature-rich GUI. The program was successful in implementing thermal electrons, secondary emissions, and self magnetic field calculations. The BOA GUI was also upgraded significantly, and CCR is receiving interest from the microwave tube and semiconductor equipment industry for the code. Implementation of PIC analysis was partially successful. Computational resource requirements for modeling more than 2000 particles begin to exceed the capability of most readily available computers. Modern plasma analysis typically requires modeling of approximately 2 million particles or more. The problem is that tracking many particles in an unstructured mesh that is adapting becomes inefficient. In particular memory requirements become excessive. This probably makes particle tracking in unstructured meshes currently unfeasible with commonly available computer resources. Consequently, Calabazas Creek Research, Inc. is exploring hybrid codes where the electromagnetic fields are solved on the unstructured, adaptive mesh while particles are tracked on a fixed mesh. Efficient interpolation routines should be able to transfer information between nodes of the two meshes. If successfully developed, this could provide high accuracy and reasonable computational efficiency.
Date: December 6, 2007
Creator: Bui, Thuc
Partner: UNT Libraries Government Documents Department

Analysis Code for High Gradient Dielectric Insulator Surface Breakdown

Description: High voltage (HV) insulators are critical components in high-energy, accelerator and pulsed power systems that drive diverse applications in the national security, nuclear weapons science, defense and industrial arenas. In these systems, the insulator may separate vacuum/non-vacuum regions or conductors with high electrical field gradients. These insulators will often fail at electric fields over an order of magnitude lower than their intrinsic dielectric strength due to flashover at the dielectric interface. Decades of studies have produced a wealth of information on fundamental processes and mechanisms important for flashover initiation, but only for relatively simple insulator configurations in controlled environments. Accelerator and pulsed power system designers are faced with applying the fundamental knowledge to complex, operational devices with escalating HV requirements. Designers are forced to rely on “best practices” and expensive prototype testing, providing boundaries for successful operation. However, the safety margin is difficult to estimate, and system design must be very conservative for situations where testing is not practicable, or replacement of failed parts is disruptive or expensive. The Phase I program demonstrated the feasibility of developing an advanced code for modeling insulator breakdown. Such a code would be of great interest for a number of applications, including high energy physics, microwave source development, fusion sciences, and other research and industrial applications using high voltage devices.
Date: May 30, 2010
Creator: Ives, Robert Lawrence; Verboncoeur, John & Aldan, Manuel
Partner: UNT Libraries Government Documents Department

A 30 MW, 200 MHz Inductive Output Tube for RF Accelerators

Description: This program investigated development of a multiple beam inductive output tube (IOT) to produce 30 MW pulses at 200 MHz. The program was successful in demonstrating feasibility of developing the source to achieve the desired power in microsecond pulses with 70% efficiency. The predicted gain of the device is 24 dB. Consequently, a 200 kW driver would be required for the RF input. Estimated cost of this driver is approximately $1.25 M. Given the estimated development cost of the IOT of approximately $750K and the requirements for a test set that would significantly increase the cost, it was determined that development could not be achieved within the funding constraints of a Phase II program.
Date: June 19, 2008
Creator: Ives, R. Lawrence & Read, Michael
Partner: UNT Libraries Government Documents Department

Development of a 50 MW Multiple Beam Klystron

Description: The goal of this program was to develop a 50 MW, multiple beam klystron at 11.424 GHz. The device uses eight electron guns and beam lines to achieve the required power level at a beam voltage of 190 kV, consistent with solid state power supplies. The electron gun operates with confined flow focusing, which is unique among current multiple beam sources, and allows operation at power levels consistent with producing 10s of MWs of pulsed RF power. The circuit consists of a ring resonator input cavity, eight sets of buncher cavities, and a ring resonator output cavity. The RF output power is coupled into four rectangular waveguides equally spaced around the klystron. Eight individual collectors absorb the spent beam power in each beam. The klystron operates in a solenoid. The principle challenges in the design included development of the beam optics using confined flow focusing, shaping of the magnetic field in the gun region to avoid beam spiraling, coupling input power equally to all eight beam lines from a single input, and obtaining the required frequency and Q in the output cavity. The mechanical design was particularly complex due to the large parts count, number of braze and weld joints, and close proximity of the beam lines that limited access. Addressing vacuum leaks and cold testing the complex structures was particularly troublesome. At the conclusion of the program, the klystron is experiencing several vacuum leaks that are under repair. Efforts will continue to seal and test the klystron.
Date: October 31, 2007
Creator: Ives, R Lawrence; Ferguson, Patrick; Read, Michael & Collins, George
Partner: UNT Libraries Government Documents Department

Final Technical Report

Description: This program applied reservoir cathode technology to increase the lifetime of cesiated tungsten photocathodes. Cesiated tungsten photocathodes provide a quantum efficiency of approximately 0.08% when cesium is initially applied to the surface. During operation, however, the cesium evaporates from the surface, resulting in a gradual decrease in quantum efficiency. After 4-6 hours of operation, the efficiency drop to below useful levels, requiring recoating on the emission surface. This program developed a cathode geometry where cesium could be continuously diffused to the surface at a rate matching the evaporation rate. This results in constant current emission until the cesium in the reservoir is depleted. Measurements of the evaporation rate indicated that the reservoir should provide cesium for more than 30,000 hours of continuous operation. This is orders of magnitude longer operation then previously available. Experiments also demonstrated that the photocathode could be rejuvenated following contamination from a vacuum leak. Recoating of the emission surface demonstrated that the initial quantum efficiency could be recovered.
Date: September 25, 2012
Creator: Ives, Lawrence; Montgomery, Eric; Pan, Zhigang; Riddick, Blake; Feldman, Donald & Falce, Lou
Partner: UNT Libraries Government Documents Department

Final Technical Report

Description: Calabazas Creek Research Inc. (CCR) completed Phase I the development of a 10 MW, 1.3 GHz, annular beam klystron (ABK) for driving advanced accelerators, such as the International Linear Collider (ILC). Through detailed simulations in Phase I, CCR produced a design that meets all of the requirements for ILC. The ABK uses an annular beam to minimize space charge depression and the impedance. This allows the relatively low voltage of 120 kV specified for the International Linear Collider (ILC). Like the sheet beam klystron, the ABK uses a thin beam located close to the drift tube walls; however, it operates with lower risk, single mode cavities. In addition, it is azimuthally symmetric, dramatically reducing design and fabrication costs. It provides the same operating characteristics as a multi-beam klystron, but is far simpler and will be easier and less expensive to fabricate.
Date: May 17, 2010
Creator: Read, Michael; Ives, R. Lawrence & Ferguson, Patrick
Partner: UNT Libraries Government Documents Department

Phase II Final Report Computer Optimization of Electron Guns

Description: This program implemented advanced computer optimization into an adaptive mesh, finite element, 3D, charged particle code. The routines can optimize electron gun performance to achieve a specified current, beam size, and perveance. It can also minimize beam ripple and electric field gradients. The magnetics optimization capability allows design of coil geometries and magnetic material configurations to achieve a specified axial magnetic field profile. The optimization control program, built into the charged particle code Beam Optics Analyzer (BOA) utilizes a 3D solid modeling package to modify geometry using design tables. Parameters within the graphical user interface (currents, voltages, etc.) can be directly modified within BOA. The program implemented advanced post processing capability for the optimization routines as well as the user. A Graphical User Interface allows the user to set up goal functions, select variables, establish ranges of variation, and define performance criteria. The optimization capability allowed development of a doubly convergent multiple beam gun that could not be designed using previous techniques.
Date: April 15, 2011
Creator: Ives, R. Lawrence; Bui, Thuc; Tran, Hien; Read, Michael; Attarian, Adam & Tallis, William
Partner: UNT Libraries Government Documents Department

Final Report 200 MW L-Band Annular Beam Klystron for Accelerators

Description: This program developed a 200 MW, 1.3 GHz, Annular Beam Klystron (ABK) for accelerator systems. An ABK provides lower impedance than a conventional klystron, making it possible to produce higher RF powers with lower voltages. With a higher power per unit, fewer klystrons would be required for a large accelerator. Lower voltage also simplifies and reduces the cost of the power supply system. Both features will significantly lower the cost of an RF system. This device operates at 475 kV. The klystron uses a magnetron injection gun producing 1100 A in one microsecond pulses. Power is extracted into fundamental rectangular waveguide through two output windows. The predicted gain is approximately 45 dB with estimated efficiency of 45%. The klystron was assembled, but no facility was available for testing. Consequently, no high power performance measurements are available. Because the assembled klystron is approximately 15 feet long, it was disassembled for storage. It can be reassembled should a use materialize.
Date: February 11, 2009
Creator: Read, Michael; Ferguson, Patrick; Ives, Lawrence; Song, Liqun; Carlsten, Bruce & Fazio, Michael
Partner: UNT Libraries Government Documents Department

Final Report Advanced Quasioptical Launcher System

Description: This program developed an analytical design tool for designing antenna and mirror systems to convert whispering gallery RF modes to Gaussian or HE11 modes. Whispering gallery modes are generated by gyrotrons used for electron cyclotron heating of fusion plasmas in tokamaks. These modes cannot be easily transmitted and must be converted to free space or waveguide modes compatible with transmission line systems.This program improved the capability of SURF3D/LOT, which was initially developed in a previous SBIR program. This suite of codes revolutionized quasi-optical launcher design, and this code, or equivalent codes, are now used worldwide. This program added functionality to SURF3D/LOT to allow creating of more compact launcher and mirror systems and provide direct coupling to corrugated waveguide within the vacuum envelope of the gyrotron. Analysis was also extended to include full-wave analysis of mirror transmission line systems. The code includes a graphical user interface and is available for advanced design of launcher systems.
Date: April 30, 2010
Creator: Neilson, Jeffrey
Partner: UNT Libraries Government Documents Department

An Over-moded Fundamental Power Coupler for the ILC

Description: The current design of fundamental power couplers for the ILC are expensive and require excessively long conditioning times. The goal of this develoment is design of a coupler that requires little rf processing and is significantly less expensive to build than the present ILC coupler. The goal of this program is development of a new technology for power couplers.This new technology is based on the cylindrical TE01 mode and other over-moded technologies developed for the X-band rf distribution system of the NCLTA. During the Phase I program, a TE10 to TE01 mode transducer suitable for use as a part of a power coupler in the ILC will be designed, built and tested. Following a succesful test, prototype designs of the TE01 to cavity coupler and thermal will be produced. A detailed study of the suitability of this overmoded waveguide technology for the ILC power coupler will be provided in the final report. Development of over-moded power couplers for superconducting cavities could find application im many world-wide accelerator projects, such as SNS, Jefferson Lab upgrade, RIA, TESLA in addition to the ILC.
Date: May 20, 2009
Creator: Jeff Neilson, Sami Tantawi, Rand Pendleton
Partner: UNT Libraries Government Documents Department

Improved Collectors for High Power Gyrotrons

Description: High power gyrotrons are used for electron cyclotron heating, current drive and parasitic mode suppression in tokamaks for fusion energy research. These devices are crucial for successful operation of many research programs around the world, including the ITER program currently being constructed in France. Recent gyrotron failures resulted from cyclic fatigue of the copper material used to fabricated the collectors. The techniques used to collect the spent beam power is common in many gyrotrons produced around the world. There is serious concern that these tubes may also be at risk from cyclic fatigue. This program addresses the cause of the collector failure. The Phase I program successfully demonstrated feasibility of a mode of operation that eliminates the cyclic operation that caused the failure. It also demonstrated that new material can provide increased lifetime under cyclic operation that could increase the lifetime by more than on order of magnitude. The Phase II program will complete that research and develop a collector that eliminates the fatigue failures. Such a design would find application around the world.
Date: May 20, 2009
Creator: R. Lawrence Ives, Amarjit Singh, Michael Read, Philipp Borchard, Jeff Neilson
Partner: UNT Libraries Government Documents Department

Development of a 50 MW 30 GHz Gyroklystron Amplifier

Description: DOE requires sources for testing of high gradient accelerator structures. A power of 50 MW is required at K and Ka band. The pulse length must be ~ 1 microsecond and the pulse repetition frequency at least 100 Hz. At least some applications may require phase stability not offered by a free running oscillator. CCR proposed to build a 50 MW 30 GHz gyrklystron amplifier. This approach would give the required phase stability. The frequency was at the second harmonic of the cycltron frequency and used the TE02 mode. This makes it possible to design a device without an inner conductor, and with a conventional (non-inverted) MIG. This minimizes cost and the risk due to mechanical alignment issues. A detailed design of the gyroklystron was produced. The design was based on simulations of the cavity(ies), electron gun, output coupler and output window. Two designs were produced. One was at the fundamental of the cyclotron frequency. Simulations predicted an output power of 72 MW with an efficiency of 48%. The other was at the second harmonic, producing 37 MW with an efficiency of 37%.
Date: May 20, 2009
Creator: Read, Michael & Wesely Lawson, Lawrence Ives, Jeff Neilson
Partner: UNT Libraries Government Documents Department

Final Technical Report

Description: The Phase I program met or exceeded all the program goals. During the Phase I program, CCR personnel communicated directly with Dr. Al Moretti at Fermilab concerning the design and specifications. Results of the Phase I program were also presented at the MUON Accelerator Conference in Berkeley, California in February 2005. This review of the design by accelerator scientists provided additional verification of the approach and predicted performance. Results for specific program tasks are described below. In addition, CCR performed a preliminary investigation for a 10 MW device at the request of personnel at Fermi National Laboratory. Results of that task are also provided.
Date: December 1, 2005
Creator: Ives, Lawrence
Partner: UNT Libraries Government Documents Department

Final report

Description: Calabazas Creek Research Inc. (CCR) has investigated the feasibility of a 30 GHz gyroklystron amplifier for driving advanced accelerators. Gyroklystrons have been shown to be efficient sources of high power radiation at frequencies above X-Band and are, therefore, well suited for driving high frequency accelerators. CCR's gyroklystron design includes a novel inverted magnetron injection gun (MIG) that allows support and cooling of the coaxial inner conductor of the circuit. This novel gun provides a very high quality electron beam, making it possible to achieve a cavity design with an efficiency of 54%. During Phase I, it was determined that the original frequency of 17 GHz was no longer well matched to the potential market. A survey of accelerator needs identified the Compact Linear Collider (CLIC) as requiring 30 GHz sources for testing of accelerator structures. Developers at CLIC are seeking approximately 25 MW per tube. This will result in the same power density as in the original 80 MW, 17 GHz device and will thus have essentially the same risk. CLIC will require initially 3-4 tubes and eventually 12-16 tubes. This quantity represents $5M-$10M in sales. In addition, gyroklystrons are of interest for radar systems and electron paramagnetic resonance (EPR) instruments. Following discussions with the Department of Energy, it was determined that changing the program goal to the CLIC requirement was in the best interest of CCR and the funding agency. The Phase I program resulted in a successful gyroklystron design with a calculated efficiency of 54% with an output power of 33 MW. Design calculations for all critical components are complete, and no significant technical issues remain.
Date: December 1, 2005
Creator: Michael Read, Wesley Lawson, George Miram, David Marsden, Philipp Borchard,pborchard@gmx.net
Partner: UNT Libraries Government Documents Department

Final Report for Sheet Beam Klystron Program

Description: The Phase I program demonstrated feasibility of the RF circuit, periodic permanent magnet focusing and beam transport. Computer simulations indicate that the device should meet the goals of the program with the anticipated power and efficiency. The electron gun is currently under construction in another program, and the collector is a simple design based on existing technology.
Date: September 22, 2004
Creator: Read, Michael; Ives, Lawrence & Phillips, Purobi
Partner: UNT Libraries Government Documents Department