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| TPPT027 | 53 MHz Beam Loading Compensation for Slip Stacking in the Fermilab Main Injector | beam-loading, feedback, proton, cathode | 1958 | ||
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Funding: Operated by Universities Research Association, Inc. for the U.S. Department of Energy under contract DE-AC02-76CH03000. |
Recently In-Phase and Quadrature (I&Q) was added to both the 53 MHz Feedback and Feedforward Beam Loading Compensation for Slip Stacking in the Fermilab Main Injector. With 53 MHz Feedback, we can now turn the 18 Radio Frequency (RF) Stations off down to below 100 V. In using I&Q on Feedforward, beam loading compensation to the beam on both the upper and lower frequencies of Slip Stacking can be applied as we slip the beam. I&Q theory will be discussed. |
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| TPPT055 | Electro-Polishing Surface Preparation for High Gradient Cavities at DESY | acceleration, superconductivity, feedback, linac | 3304 | ||
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Improvement of acceleration gradients in super conducting accelerator structures was reached by applying electro polishing of the niobium surfaces. This technology is actually foreseen to serve as major surface preparation step for projects like the XFEL at DESY and the proposed ILC linear accelerator. At DESY an electro polishing apparatus was build up in 2003. After commissioning the apparatus operates regular for cavity surface treatment. We report on experiences with the electro-polishing set up, polishing parameters and results on the preparation of S.C. resonators for a high gradient module to be tested in the TTF2 accelerator at DESY.
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| TPPT098 | VORPAL as a Tool for Three-Dimensional Simulations of Multipacting in Superconducting RF Cavities | electron, simulation, plasma, resonance | 4332 | ||
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Considerable resources are required to run three dimensional simulations of multipacting in superconducting rf cavities. Three dimensional simulations are needed to understand the possible roles of non-axisymmetric features such as the power couplers. Such simulations require the ability to run in parallel. We consider the versatile plasma simulation code VORPAL* as a possible platform to study such effects. VORPAL has a general 3D domain decomposition and can run in any physical dimension. VORPAL uses the CMEE library** to model the secondary emission of electrons from metal surfaces. We will present a three dimensional simulation of a simple pillbox rf cavity to demonstrate the potential of VORPAL to be a major simulation tool for superconducting rf cavities.
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*C. Nieter and J.R. Cary, J. Comp. Phys. 196 (2004), p. 448. **P.H. Stoltz, ICFA electron cloud work shop, Napa, CA (2004). |
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| WPAE001 | Helium Distribution for the Superconducting Devices in NSRRC | superconducting-magnet, vacuum, storage-ring, monitoring | 758 | ||
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In NSRRC up to five superconducting magnets and one superconducting cavity will be installed in the storage ring. At current stage two superconducting magnets and one superconducting cavity are kept in cold condition by one 450W helium cryogenic system. The crucial stable cryogenic condition required from the superconducting cavity is hard to achieve due to the join of superconducting magnets. A second cryogenic system dedicated for the superconducting magnets is planned in the next stage. A switch valve box serves the function for the backup of two cryogenic systems for each other and a 100 meter nitrogen-shielding helium transfer line dedicated for the five superconducting magnets are installed at end of the year 2004. This paper presents the helium distribution design of the two cryogenic systems and the commission result of the recent work.
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| WPAT025 | First Results of the IOT Based 300 kW 500 MHz Amplifier for the Diamond Light Source | factory, power-supply, synchrotron, background | 1883 | ||
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We present the first RF measurements of the IOT based 300 kW 500 MHz amplifier for the Diamond Light Source. Four 80 kW IOTs are combined using a waveguide combiner to achieve the RF requirement of up to 300 kW for each of three superconducting cavities for the main storage ring. The IOTs are protected by a full power circulator and a 300 kW ferrite RF load. This is the first time IOTs will be used for a synchrotron light source. This paper gives an overview of the design of the Thales amplifiers and IOTs with commissioning results including measurements of key components and overall RF performance following factory tests and the installation of the first unit
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| WPAT041 | Klystron Linearizer for Use with 1.2 MW 476 MHz Klystrons in PEP-II RF Systems | klystron, feedback, impedance, monitoring | 2660 | ||
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Funding: Work supported by U.S. Department of Energy contract DE-AC02-76SF00515. |
The direct and comb loop feedback around the RF cavities in PEP-II is critical in reducing longitudinal instabilities driven by the cavity impedance, and the non-linear 1 MW klystron is in the signal path for these feedback loops. As a result, the effective small-signal gain of the klystron at 85% saturation reduces the impedance control by factors of 5 to 20 as compared to a linear power amplifier. A klystron linearizer circuit has been developed which operates in series with the power amplifier and acts to equalize the small and large signal gains through the combination. The technique must implement a 1 MHz linear control bandwidth over roughly 15 dB of RF signal level variation. The dynamics of this system is operating point dependent, and the channel must have dynamic gain compensation to keep the linearity compensation loop stable over changes in operating point. The design of this non-linear signal processing channel (incorporating RF and DSP techniques) and measured results from full-power klystron testing are presented. |
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| WPAT076 | Resonant High Power Combiners | insertion, resonance, impedance, synchrotron | 3970 | ||
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Particle accelerators need radio frequency sources. Above 300 MHz, the amplifiers mostly used high power klystrons developed for this sole purpose. As for military equipment, users are drawn to buy "off the shelf" components rather than dedicated devices. IOTs have replaced most klystrons in TV transmitters and find their way in particle accelerators. They are less bulky, easier to replace, more efficient at reduced power. They are also far less powerful. What is the benefit of very compact sources if huge 3 dB couplers are needed to combine the power? To alleviate this drawback, we investigated a resonant combiner, operating in TM010 mode, able to combine 3 to 5 IOTs. Our IOTs being able to deliver 80 kW C.W. apiece, combined power would reach 400 kW minus the minor insertion loss. Values for matching and insertion loss are given. The behavior of the system in case of IOT failure is analyzed.
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| WPAT078 | A High Power RF Power Supply for High Energy Physics Applications | power-supply, resonance | 4018 | ||
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Funding: Particle Physics and Astronomy Research Council (PPARC). |
Accelerators used for experiments in high-energy physics require very high power radio frequency sources to provide the energy needed to accelerate the particles. The RF power needs to be stable and predictable such that any variation in the supplied RF power has a limited and acceptable impact on the accelerated beam quality. The output load specifications for high voltage DC power systems are becoming increasingly more demanding. In addition, the impact of such systems on the electricity source is becoming more tightly regulated through power quality directives. These regulations set limits, for example, on the allowable individual harmonic current amplitudes and on "flicker" caused by transient load demands - the latter is particularly important for "long-pulse" modulators. The requirements above have to be met while still providing higher reliability to a higher specification at lower cost. A situation has now been reached where modulators based on existing approaches cannot meet these specifications and stay within acceptable cost and size limits. This demands that new approaches be taken to provide the power supplies needed for such applications. The research proposed here addresses this need. |
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| WPAT079 | Design of a Direct Converter for High Power, RF Applications | feedback, booster, target, synchrotron | 4033 | ||
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Funding: Particle Physics and Astronomy Research Council. |
This paper is concerned with a new type of power supply for high power RF applications for CW operation. The converter is a direct topology operating with a high frequency (resonant) link. Switching losses are minimised by switching at zero current. High operating frequency allows for minimised transformer and filter size. Advantages of this topology over conventional approaches are discussed, along with the potential problems and proposed solutions. Recently, considerable interest has been shown in direct converter topologies as an alternative topology in motor drive applications. This approach offers advantages such as reduced energy storage and higher energy density compared to conventional topologies. The work presented in this paper capitalises on these advantages in other fields, namely power conversion for RF supplies. The RF power needs to be stable and predictable such that any variation has a limited impact on the accelerated beam quality. In order to meet the required output voltage specification such designs require output filters with consequent energy storage. Management of this energy in the event of a fault is necessary if destruction of the tube is to be avoided. |
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| RPAT100 | Radiation-Hard Beam Position Detector for Use in the Accelerator Dump Lines | target, electron, radiation, monitoring | 4341 | ||
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Funding: This work supported by the U.S. Department of Energy under contract DE-AC05-84ER40150 |
The new proposed method of beam position measurement is particularly suitable for monitoring high energy, and high power accelerated beams of charged particles in the vicinity of power beam dumps. Generally, the beam quality in those areas is very poor, and any equipment positioned there must be extremely resistant to radiation damage. We have found that a plate made of Chemical Vapor Deposition (CVD) Silicon Carbide (SiC) has a set of physical properties that make it suitable for such an application. CVD SiC material is a chemically inert, extremely radiation-hard, thermo-resistive semiconductor capable of withstanding working temperatures up to 2000 degrees Kelvin. It has good thermal conductivity comparable to that of Aluminum, which makes it possible to use it in high-current particle beams. High electrical resistivity of the material, and its semiconductor properties allow characterization of the position of a particle beam crossing such a plate by measuring balance of electrical currents at the plate ends. The design of a test device, and first results are presented in the report. |
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| RPPE014 | Temperature Regulation of the Accelerating Section in CANDLE Linac | feedback, linac, simulation, resonance | 1416 | ||
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The temperature of the CANDLE S-Band Linac high-power RF components will be regulated by stand-alone closed loop (SACL) water system. The RF components are made of oxygen-free high conductivity copper and respond quickly to temperature changes. Temperature stabilization better than ± 0.1 C is required to achieve a good RF phase and energy stability. The temperature regulation and control philosophy along with the simulation results are discussed.
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| RPPE064 | Development of a Cryogenic Radiation Detector for Mapping Radio Frequency Superconducting Cavity Field Emissions | radiation, shielding, diagnostics | 3627 | ||
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Funding: Work supported by: U.S. DOE Contract No. DE-AC05-84er4015. |
There is a relationship between field emissions in a Super Conducting RF cavity and the production of radiation (mostly X-rays). External (room temperature) detectors are shielded from the onset of low energy X-rays by the vacuum and cryogenic stainless steel module walls. An internal measuring system for mapping field emissions would assist scientists and engineers in perfecting surface deposition and acid washing module surfaces. Two measurement systems are undergoing cryogenic testing at JLab. One is an active CsI photodiode array and the second is an X-ray film camera. The CsI array has operated sucessfully in a cavity in liquid Helium but saturated at higher power due to scattering in the cavity. A shield with an aperature similar to the X-ray film detector is being designed for the next series of tests which will be completed before PAC-05. |
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| RPPE068 | A Magnetostrictive Tuning System for Particle Accelerators | vacuum, monitoring, background, synchrotron | 3762 | ||
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Funding: This work is supported by DOE SBIR Program DE-FG02-03ER83648. |
Energen, Inc. has designed, built, and demonstrated several fast and slow tuners based on its magnetostrictive actuators and stepper motor. These tuners are designed for Superconducting Radio Frequency (SRF) cavities, which are important structures in particle accelerators that support a wide spectrum of disciplines, including nuclear and high-energy physics and free electron lasers (FEL). In the past two years, Energen’s work has focused on magnetostrictive fast tuners for microphonics and Lorentz detuning compensation on elliptical-cell and spoke-loaded cavities, including the capability for real-time closed-loop control. These tuners were custom designed to meet specific requirements, which included a few to 100 micron stroke range, hundreds to kilohertz operation frequency, and cryogenic temperature operation in vacuum or liquid helium. These tuners have been tested in house and at different laboratories, such as DESY, Argonne National Lab, and Jefferson Lab. Some recent results are presented in this paper. |
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| RPPT038 | Phase Noise Characteristics of Fiber Lasers as Potential Ultra-Stable Master Oscillators | laser, electron, booster, feedback | 2521 | ||
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Fourth-generation light sources, such as the European X-Ray free electron laser facility (XFEL) require timing signals distributed over distances of the order of kilometers with a timing jitter in the order of femtoseconds. The master clock for the proposed optical distribution system must operate with exceptionally low timing jitter. A promising approach is the use of a mode-locked laser that generates ultrastable pulses which are distributed via timing stabilized fiber links. Candidates for the pulse source are mode-locked Erbium doped fiber lasers, featuring very low high frequency noise. In this paper, we present a study of the phase noise of various fiber lasers in view of their applicability as laser-based master oscillators for femtosecond timing distributions.
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| RPPT043 | Commissioning of the Main Magnet of Kolkata K-500 Superconducting Cyclotron | cyclotron, vacuum, superconducting-magnet, power-supply | 2765 | ||
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Main magnet of the K-500 superconducting cyclotron at Kolkata has been fully assembled in the cyclotron vault. The assembly includes alpha and beta superconducting coils inside the liquid helium chamber, coil tank for the outer vacuum, liquid nitrogen shield, support links, cryogenic instrumentation and 80 ton magnet frame forming the pill box structure. Cooling of the coils was started in mid-December. It took about three weeks to fill the liquid helium chamber - fully immersing the coils. All the four temperature sensors embedded in the coil are steady at about 4.4K. At this time the liquid nitrogen line for cooling the shield seems to show a leak. So, we are not cooling the shield. The helium liquefier/regrigerator of 200W capacity has been functioning well and so is the network of vacuum jacketted and liquid nitrogen cooled cryogenic transfer lines. Energization of the main magnet will begin soon. Magnetic field measurement set up is in place to start the mapping. In this presentation, our experiences with commissioning of the largest superconducting magnet in India, with stored energy 22 MJ at peak field of 6T, will be described. Some results of the magnetic field measurements will also be presented.
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| FPAT050 | Improvement RF Control System for the 20 Mev Proton Linac of PEFP | rfq, proton, feedback, linac | 3100 | ||
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Funding: EPICS, Control, LLRF. |
This paper presents the RF control system for Korea Multi-purpose Accelerator Complex (KOMAC). KAERI (Korea Atomic Energy Research Institute) has been performing the project named KOMAC. As the 3nd phase of the project, 20MeV proton accelerating structure is under development. The new design is based on the use of VME based Multi-function modules connected to the specific low level RF Controllers(LLRF) via distributed I/O modules and Serial communication modules. The control system was based on EPICS (Experimental Physics and Industrial Control System) from the end of 2004. Installation and commissioning of the RF module is scheduled on 2005. Control system to integrated the RF System to the KOMAC control system is implemented. Hardware, software and various applications are upgrade to support the operation of RF Control system. In this paper, We describe control structure and scheme of the current RF Control System and upgraded one. |
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