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Rf systems for RHIC

Description: The RHIC rf systems must capture the injected beam, accelerate it through transition to top energy, shorten the bunches prior to rebucketing, and store the beam for 10 hours in the presence of strong intra-beam scattering. These different functions are met by three independent systems. An accelerating system at 26.7 Mhz (h = 342), a storage system at 196.1 MHz (h = 2508), and a wideband system for the damping of injection efforts.
Date: May 1, 1995
Creator: Rose, J.; Brodowski, J.; Connolly, R.; Deng, D.P.; Kwiatkowski, S.; Pirkl, W. et al.
Partner: UNT Libraries Government Documents Department

STUDIES ON THE RCMS RF SYSTEM.

Description: This note addresses the various options for the Rapid Cycling Medical Synchrotron (RCMS) RF. The study was divided into three cases, namely non-tuning, tuning and filter. Each case also includes a few options. The primary study was focused on the non-tuning options. However, it was found that it requires too much driver power to cover the wide band and thus causes the cost being too high to be competitive. The proposal of RCMS is not yet clear if it can be approved or not. The results of this study might be useful to other similar machines.
Date: January 22, 2003
Creator: ZHAO,Y.
Partner: UNT Libraries Government Documents Department

Longitudinal Stability Calculations

Description: Coupled bunch longitudinal stability in the presence of high frequency impedances is considered. A frequency domain technique is developed and compared with simulations. The frequency domain technique allows for absolute stability tests and is applied to the problem of longitudinal stability in RHIC with the new 56 MHz RF system.
Date: January 2, 2009
Creator: Blaskiewicz,M.
Partner: UNT Libraries Government Documents Department

Landau damping with high frequency impedance

Description: Coupled bunch longitudinal stability in the presence of high frequency impedances is considered. A frequency domain technique is developed and compared with simulations. The frequency domain technique allows for absolute stability tests and is applied to the problem of longitudinal stability in RHIC with the new 56 MHz RF system.
Date: May 4, 2009
Creator: Blaskiewicz,M.
Partner: UNT Libraries Government Documents Department

RF breakdown studies in X-Band klystron cavities

Description: RF breakdown studies are presently being carried out at SLAC with klystron cavities in a traveling wave resonator (TWR). Different kinds of fabrication methods and several kinds of semiconducting and insulating coatings have been applied to X-Band TM{sub 010} cavities. RF breakdown thresholds up to 250 MV/m have been obtained. Dark current levels were found to be depressed on TiN-coated and single-point diamond turned cavities. A new TM{sub 020} cavity with demountable electrodes has been designed and will be used to test a variety of materials, coatings, and processes. Recent tests of klystron output windows at 119 MW are also presented in this paper.
Date: May 1, 1997
Creator: Xu, X.; Callin, R.S. & Fowkes, W.R.
Partner: UNT Libraries Government Documents Department

OPERATION OF THE RHIC RF SYSTEMS.

Description: Operational aspects of the RHIC rf system are described. To date three different beam combinations have been collided for physics production: gold-gold, deuteron-gold, and proton-proton(polarized). To facilitate this flexibility the rf systems of the two rings are independent and self-sufficient. Techniques to cope with problems such as, injection/capture, beam loading, bunch shortening, and rf noise have evolved and are explained.
Date: May 12, 2003
Creator: BRENNAN,J.M.; BLASKIEWICZ,M.; DELONG,J.; FISCHER,W.; HAYES,T.; SMITH,K.S. et al.
Partner: UNT Libraries Government Documents Department

Modeling large heterogeneous RF structures

Description: Large heterogeneous structures are difficult to model on a numerical grid because of the limitations on computing resources, so that alternate approaches such as equivalent circuits and mode-matching have been developed to treat this problem. This paper will describe the three methods and will analyze a structure representative of the SLAC and JLC detuned structures to compare the efficacy of each approach.
Date: November 1, 1996
Creator: Li, Zenghai; Ko, Kwok; Srinivas, V. & Higo, Toshiyasu
Partner: UNT Libraries Government Documents Department

Simulation of high-average power windows for accelerator production of tritium

Description: Development of a robust, high-average-power (210 kW, CW) microwave transmission line system for the Accelerator Production of Tritium (APT) facility is a stringent engineering and operational requirement. One key component in this RF transmission system is the vacuum barrier window. The requirement of high-power handling capability coupled to the desirability of good mean time to failure characteristics can be treated substantially with a set of microwave, thermal-structural, and Weibull analysis codes. In this paper, we examine realistic 3-D engineering models of the ceramic windows. We model the detailed cooling circuit and make use of accurate heat deposition models for the RF. This input and simulation detail is used to analyze the thermal- structural induced stresses in baseline coaxial window configurations. We also use a Weibull-distribution failure.
Date: August 20, 1998
Creator: Cummings, K A; Daily, L D; Mayhall, D J; Nelson, S D; Salem, J & Shang, C C
Partner: UNT Libraries Government Documents Department

Beam breakup in a microtron

Description: In a microtron, the path length change from pass to pass is a fixed multiple of the RF wavelength, and the accelerating system can be reasonably well approximated as a single cavity. Under such circumstances it is possible to derive an analytical formula for the multipass beam breakup threshold current. The threshold current determined by numerical simulations agrees very well with the formula for a machine with a small number of passes. The analytic formula can serve as a useful guide in examining optics designs to improve the BBU threshold.
Date: June 1, 1997
Creator: Yung, B.C. & Merminga, L.
Partner: UNT Libraries Government Documents Department

Summary report for the Microwave Source Working Group

Description: This report summarizes the discussions of the Microwave Source Working Group during the Advanced Accelerator Concepts Workshop held October 13-19, 1996 in the Granlibakken Conference Center at Lake Tahoe, California. Progress on rf sources being developed for linear colliders is reviewed. Possible choices for high-power rf sources at 34 GHz and 94 GHz for future colliders are examined. 27 refs.
Date: January 1, 1997
Creator: Westenskow, G. A.
Partner: UNT Libraries Government Documents Department

Particle diffusion in overlapping resonances

Description: Longitudinal bunch dilution was studied in the IUCF Cooler Ring with phase modulation of a higher-order harmonic rf. Diffusion in the presence of overlapping parametric resonances has been identified as the dilution mechanism. We found that fast growth is associated with the rapid particle motion along separatrices of dominant parametric resonances, slow growth is related to particle diffusion in the chaotic sea, and saturation occurs when particles are bounded by an invariant torus.
Date: January 1, 1998
Creator: Ng, K.Y.
Partner: UNT Libraries Government Documents Department

Phase loop bandwidth measurements on the advanced photon source 352 MHz rf systems

Description: Phase loop bandwidth tests were performed on the Advanced Photon Source storage ring 352-MHz rf systems. These measurements were made using the HP3563A Control Systems Analyzer, with the rf systems running at 30 kilowatts into each of the storage ring cavities, without stored beam. An electronic phase shifter was used to inject approximately 14 degrees of stimulated phase shift into the low-level rf system, which produced measureable response voltage in the feedback loops without upsetting normal rf system operation. With the PID (proportional-integral-differential) amplifier settings at the values used during accelerator operation, the measurement data revealed that the 3-dB response for the cavity sum and klystron power-phase loops is approximately 7 kHz and 45 kHz, respectively, with the cavities the primary bandwidth-limiting factor in the cavity-sum loop. Data were taken at various PID settings until the loops became unstable. Crosstalk between the two phase loops was measured.
Date: August 1, 1997
Creator: Horan, D.; Nassiri, A. & Schwartz, C.
Partner: UNT Libraries Government Documents Department

Radio Frequency Plasma Applications for Space Propulsion

Description: Recent developments in solid-state radio frequency (RF) power technologies allow for the practical consideration of RF heated plasmas for space propulsion. These technologies permit the use of any electrical power source, de-couple the power and propellant sources, and allow for the effcient use of both the propellant mass and power. Effcient use of the propellant is obtained by expelling the rocket exhaust at the highest possible velocity, which can be orders of magnitude higher than those achieved in chemical rockets. Handling the hot plasma exhaust requires the use of magnetic nozzles, and the basic physics of ion detachment from the magnetic #12;eld is discussed. The plasma can be generated by RF using helicon waves to heat electrons. Further direct heating of the ions helps to reduce the line radiation losses, and the magnetic geometry is tailored to allow ion cyclotron resonance heating. RF #12;eld and ion trajectory calculations are presented to give a reasonably self-consistent picture of the ion acceleration process.
Date: September 13, 1999
Creator: Baity, F. W., Jr.; Barber, G. C.; Carter, M. D.; Chang-Diaz, F. R.; Goulding, R. H.; Ilin, A. V. et al.
Partner: UNT Libraries Government Documents Department

Investigation of High Voltage Breakdown and Arc Localization in RF Structures

Description: An effort is underway to improve the voltage standoff capabilities of ion cyclotron range of frequencies (ICRF) heating and current drive systems. One approach is to develop techniques for determining the location of an electrical breakdown (arc) when it occurs. A technique is described which uses a measurement of the reflection coefficient of a swept frequency signal to determine the arc location. The technique has several advantages including a requirement for only a small number of sensors and very simple data interpretation. In addition a test stand is described which will be used for studies of rf arc behavior. The device uses a quarter-wave resonator to produce voltages to 90 kV in the frequency range of 55-80 MHz.
Date: April 12, 1999
Creator: Bigelow, T.S.; Goulding, R.H. & Swain, D.W.
Partner: UNT Libraries Government Documents Department

RF Systems for a Proposed Next Step Option (FIRE)

Description: FIRE (Fusion Ignition Research Experiment) is a high-field, burning-plasma tokamak that is being studied as a possible option for future fusion research. Preliminary parameters for this machine are R<sub>0</sub> approximately equal to 2 m, a approximately equal to 0.5 m, B<sub>0</sub> approximately equal to 10 T, and I<sub>p</sub> approximately equal to 6 MA. Magnetic field coils are to be made of copper and precooled with LN<sub>2</sub> before each shot. The flat-top pulse length desired is greater than or equal to 10s. Ion cyclotron and lower hybrid rf systems will be used for heating and current drive. Present specifications call for 30 MW of ion cyclotron heating power, with 25 MW of lower hybrid power as an upgrade option.
Date: April 12, 1999
Creator: Carter, M.D. & Swain, D.W.
Partner: UNT Libraries Government Documents Department

Informal report on measurements of slant TEC by FORTE

Description: Los Alamos National Laboratory`s Space and Atmospheric Sciences group is now operating the FORTE satellite, which has two sets of instruments: optical detectors and radio detectors. In this report the author describes work with one set of radio detectors that allow measurements of the total electron content (TEC) traversed by VHF radiation originating at an electromagnetic pulse (EMP) generator located at Los Alamos.
Date: November 21, 1997
Creator: Massey, R.S.
Partner: UNT Libraries Government Documents Department

Experimental evaluation of 350 MHz RF accelerator windows for the low energy demonstration accelerator

Description: Radio frequency (RF) windows are historically a point where failure occurs in input power couplers for accelerators. To obtain a reliable, high-power, 350 MHz RF window for the Low Energy Demonstration Accelerator (LEDA) project of the Accelerator Production of Tritium program, RF windows prototypes from different vendors were tested. Experiments were performed to evaluate the RF windows by the vendors to select a window for the LEDA project. The Communications and Power, Inc. (CPI) windows were conditioned to 445 kW in roughly 15 hours. At 445 kW a window failed, and the cause of the failure will be presented. The English Electronic Valve, Inc. (EEV) windows were conditioned to 944 kW in 26 hours and then tested at 944 kW for 4 hours with no indication of problems.
Date: September 1, 1997
Creator: Cummings, K.; Rees, D. & Roybal, W.
Partner: UNT Libraries Government Documents Department

The Next Linear Collider Test Accelerator's RF Pulse Compression and Transmission Systems

Description: The overmoded rf transmission and pulsed power compression system for SLAC's Next Linear Collider (NLC) program requires a high degree of transmission efficiency and mode purity to be economically feasible. To this end, a number of new, high power components and systems have been developed at X-band, which transmit rf power in the low loss, circular TE01 mode with negligible mode conversion. In addition, a highly efficient SLED-II* pulse compressor has been developed and successfully tested at high power. The system produced a 200 MW, 250 ns wide pulse with a near-perfect flat-top. In this paper we describe the design and test results of the high power pulse compression system using SLED-II.
Date: February 24, 1999
Creator: Tantawi, Sami
Partner: UNT Libraries Government Documents Department

Prospects for Advanced RF Theory and Modeling

Description: This paper represents an attempt to express in print the contents of a rather philosophical review talk. The charge for the talk was not to summarize the present status of the field and what we can do, but to assess what we will need to do in the future and where the gaps are in fulfilling these needs. The objective was to be complete, covering all aspects of theory and modeling in all frequency regimes, although in the end the talk mainly focussed on the ion cyclotron range of frequencies (ICRF). In choosing which areas to develop, it is important to keep in mind who the customers for RF modeling are likely to be and what sorts of tasks they will need for RF to do. This occupies the first part of the paper. Then we examine each of the elements of a complete RF theory and try to identify the kinds of advances needed.
Date: April 12, 1999
Creator: Batchelor, D.B.
Partner: UNT Libraries Government Documents Department

Evolution of the rf systems layout for the SSC collider rings

Description: This note contains information on the results of ongoing reviews concerning the basic design of the 360-MHz rf systems for the 2 {times} 20 TeV Superconducting Super Collider (SSC). For generation of 20-MV peak voltage per ring, with proton beams of 2 {times} 70 mA, several versions have been investigated: Version A (baseline design and modified baseline): 2 {times} 8 five-cell normalconducting cavities; Version B: 2 {times} 24 single-cell normalconducting cavities; and Version C: 2 {times} 8 or 2 {times} 10 single-cell superconducting cavities. For reasons of easier High Order Mode (HOM) damping, multicell cavities have been found inferior in performance when compared to single cells. Superconducting cavities have been found superior in handling transient beam loading when compared to normalconducting cavities. A threefold higher voltage, and a reduced R/Q value of superconducting cells lead to a ninefold increase in stored electromagnetic energy which, by the same factor, reduces the speed of phase changes originating from notches in the circulating beams. The theoretical possibility to operate superconducting cavities half-detuned in order to supply reactive power to the beam may also lead to considerable savings in overall power consumption. On the other hand, many challenges are involved with the use of superconducting cavities, such as the delicacy of the superconductive state, the complexity of cryostat design and operation, tuning requirements, sensitivity to vibration, and other issues.
Date: October 1, 1993
Creator: Schaffer, G.
Partner: UNT Libraries Government Documents Department