Ferrite Characterization for the Design of an Accelerating Cavity With Perpendicular Biasing (original) (raw)
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Perpendicular Biased Ferrite Tuned Cavities for the Fermilab Booster
The aging Fermilab Booster RF system needs an upgrade to support the future experimental program. The important feature of the upgrade is a substantial enhancement of the requirements for the accelerating cavities. The new requirements include enlargement of the cavity beam pipe aperture, increase of the cavity voltage and increase in the repetition rate. The modification of the present traditional parallel biased ferrite cavities is rather challenging. An alternative to rebuilding the present Fermilab Booster RF cavities is to design and construct new perpendicular biased RF cavities, which potentially offer a number of advantages. An evaluation and a preliminary design of the perpendicular biased ferrite tuned cavities for the Fermilab Booster upgrade is described in the paper. Also it is desirable for better Booster performance to improve the capture of beam in the Booster during injection and at the start of the ramp. One possible way to do that is to flatten the bucket by introducing second harmonic cavities into the Booster. This paper also looks into the option of using perpendicularly biased ferrite tuners for the second harmonic cavities.
Tunable RF Cavities Using Orthogonally Biased Ferrite
Originally conceived as a solution for FFAG applications, a new compact RF cavity design that tunes rapidly over various frequency ranges can be used to upgrade existing machines. The design being developed uses orthogonally biased garnet cores for fast frequency tuning and liquid dielectric to adjust the frequency range and to control the core temperature. We describe measurements of candidate ferrite and dielectric materials. The first use of the new cavity concept will be for improvements to the 8 GeV Fermilab Booster synchrotron.
Investigation of dielectric and magnetic properties of AL-800 ferrite
Lithuanian Journal of Physics
Ferrites are usually used in accelerators for tuning radiofrequency (RF) cavities and in nonreciprocal devices controlling the power flow in RF accelerating systems. The conventional parallel‐biased Ni Zn ferrites employed for varying the frequency of accelerating cavities have the disadvantage of high saturation magnetization (4πMs). Application of the transversely biased yttrium iron garnet (YIG) material in RF tuners promises a significant reduction of power loss compared with systems that use the longitudinal bias. To inject the beam and extract the beam out of the CERN accelerator rings the fast kicker magnets made from ferrite materials must be used. Power deposition in the kicker magnets can be a limitation: if the temperature of the ferrite yoke exceeds the Curie temperature, the beam will not be properly deflected. Investigation of the ferrite electromagnetic properties of materials up to the GHz frequency range is essential for a correct impedance evaluation. This report s...
The Effect of 2-Directional Magnetic Biasing Used for Tuning of a Ferrite-Loaded Re-entrant Cavity
IEEE Transactions on Nuclear Science, 2000
Cavities that are partially filled with ferrite material provide a tunable resonance frequency by making use of the changing µ-characteristics of ferrites when exposed to an external magnetic bias field. The concept of using either parallel or perpendicular magnetic biasing to reach a certain resonance frequency of a cavity has been known for many years. However, a cavity based on superposition of perpendicular and parallel magnetic fields to obtain improved ferrite characteristics was suggested in W. R. Smythe "Reducing ferrite tuner power loss by bias field rotation," IEEE Trans. Nucl. Sci., vol. 30, no. 4, pp. 273-275, 1983, but to our knowledge was neither tested nor built. Such a 2-directional biasing is expected to provide a reduction in RF losses for an identical tuning range as compared with the classical 1directional magnetic bias. We have successfully tested this theory with a measurement setup consisting of a ferrite-filled cavity, exposed to external biases that allow the clear separation of the two orientations of superposed magnetic bias fields. The outcome is an enlargement of tuning range with high cavity Ԛ and the possibility of fast tuning. In this paper, we describe the measurement setup and present the tuning ranges that we attained by applying different bias schemes.
Study on a tuning-free network for the rf accelerating cavity
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1996
Applying a bridged-T type all-pass network to a resonator described as a parallel circuit, the output voltage of the resonator shows a band-pass feature over a certain frequency range, while the input impedance is always constant against frequency. This feature is considered to realize the ferrite-loaded tuning-free rf accelerating cavity. It has several merits such as a simple cavity structure without bias windings, an easy operation without feedback control of the bias current, applying new ferrite with favorable rf characteristics and so on. The accelerating system is applicable to a proton-synchrotron for radio therapy or a cooler-synchrotron for nuclear physics studies in a multi-GeV region. This paper presents a theory of the system, the characteristics of the new ferrite, which is currently developed, and design studies of the network based on preliminary measurements of an equivalent lumped circuit.
A Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster
2015
A perpendicular biased 2nd harmonic cavity is currently being designed for the Fermilab Booster. Its purpose cavity is to flatten the bucket at injection and thus change the longitudinal beam distribution so that space charge effects are decreased. It can also with transition crossing. The reason for the choice of perpendicular biasing over parallel biasing is that the Q of the cavity is much higher and thus allows the accelerating voltage to be a factor of two higher than a similar parallel biased cavity. This cavity will also provide a higher accelerating voltage per meter than the present folded transmission line cavity. However, this type of cavity presents technical challenges that need to be addressed. The two major issues are cooling of the garnet material from the effects of the RF and the cavity itself from eddy current heating because of the 15 Hz bias field ramp. This paper will address the technical challenge of preventing the garnet from overheating.
Advanced electromagnetic design of cavities for high current accelerators
Proceedings Particle Accelerator Conference, 1995
This report was prepared as an acmuht of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or n i 10s Alamos National Laboratoty, an affirmative actiorVequal opportunity employer, is operated by the Universjty of California for the U.S. Department of Energy under contract W-7405-ENG-36. By acceptance of this article, the publisher recognizes that the US. Government retains a nonexclusive royalty-free license to publish or reproduce the published form of this contribution, or to allow others to do so, for US. Government purposes. The Los Alams iational Laboratoly requests that the publisher identify this article as work performed under the auspices of the U.S. Department of Energy.
IEEE Transactions on Nuclear Science
The design of suitable electromagnetic band-gap (EBG) cavities has been performed by means of a hybrid numerical/analytical approach implemented via a homemade code with the aim of optimizing a novel accelerating structure for proton linear accelerators (linacs). In particular, a 3-GHz proton linac tank with on-axis coupled EBG cavities closed with full end cells has been optimized. The proton beam input energy is 27 MeV. The performances of the proton linac EBG accelerating cavities has been compared with the performances of a 27-MeV 3-GHz side-coupled proton linac accelerating cavities in terms of typical linac figures of merit. The use of EBG cavities allows to increase the transit-time factor (by about 8%). Moreover, the peak surface electric field is strongly reduced (by about 65%), paving the way to the design of very high accelerating gradient microwave proton linacs. Furthermore, the wakefields of the EBG structure have been compared to the wakefields of the SCL structure, showing that the EBG structure provides effective damping of the transverse wakefields.