Fast Kicker Magnet Research Articles

Investigation of dielectric and magnetic properties of AL-800 ferrite

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 summarizes an approach for deriving electromagnetic properties as a function of both frequency and temperature of the AL-800 garnet material. This information will be useful for simulating ferrite behaviour under realistic operating conditions.

Coil induced eddy current analysis of a fast kicker magnet

The eddy current effect is an important issue in pulsed magnet design. The eddy currents in the iron cores and the metal supports are proven to be the major causes of the eddy current effects in accelerator magnets. In our previous study, we focused on the eddy current effects in yoke and metal supports of a fast kicker magnet in Huazhong University of Science and Technology (HUST). Simulations using OPERA 3D revealed that eddy currents in yoke and metal supports have no significant influence on the magnetic field quality. However, the measured magnetic field distortion is approximately ± 0.4% during the fast change of magnetic field, and it takes several hundreds of microseconds to disappear. In addition, it is difficult to achieve a fast transient from the rising process to a steady state. Herein, we investigate the coil induced eddy current effect of a fast kicker magnet and reveal the main reason for the field distortion and the difficulty in the pulsed power supply commissioning. With design considerations of the coil induced eddy current, the simulation results can be in good agreement with the measurement results. Based on the dynamic performance of the load inductance, a fast transient from the rising process to a steady state can be achieved. The research findings can provide a good reference in the design and optimization of such pulsed magnet and associated power supply, especially for the fast kicker/bump magnet with windows frame yoke.

Design study for large acceptance muon beamlines by using beam splitting methods

A muon beamline scheme is designed for the Phase-I of the Experimental Muon Source (EMuS), which is a standalone facility by sharing the proton beam extracted from the Rapid Cycling Synchrotron (RCS) of China Spallation Neutron Source (CSNS). The proton beam for EMuS has a beam power of 20–25 kW and kinetic energy of 1.6 GeV with a low repetition rate of 1.25–2.5 Hz. Different from traditional muon beamline design, a sophisticated beam splitting system using combined spatial and time splitting methods has been developed for the EMuS beamline. In order to profit a graphite target of long effective length, the beamline is designed to have a large horizontal acceptance of 6000π·mm·mrad. A special electrostatic deflector with two channels splits the beam spatially into two branch beamlines, so that the reduced horizontal emittance of the split beams becomes utilizable for applications. Since the muon beam has a time structure of two bunches per pulse that inherits from the proton beam and a single bunch is required for μSR applications, a fast kicker magnet is used to separate two bunches into two endstations. All these make simultaneous muon beams in four endstations that are basically for μSR applications. Surface muons with an intensity order of 105/s and different spot sizes are available for all the four endstations. The contaminated positrons are carefully treated to reduce the background by combining the use of the electrostatic deflector and a dedicated Wien filter.

Design, Construction and Testing of a Magnetic Probe for Fast Kicker Magnets

Design, Construction and Testing of a Magnetic Probe for Fast Kicker Magnets

Development and measurement of a fast kicker magnet applied to a proton therapy facility

A proton therapy facility based on spot scanning technique requires a fast ON/OFF beam switch during beam spots and energy modulation procedures. At HUST, a proton therapy facility (HUST-PTF) with multiple treatment rooms is under development. For HUST-PTF, this beam switch function is implemented by a fast kicker magnet and downstream beam dump. This paper introduces the development and measurement of this kicker magnet system, with main topics: (1) the development and measurement of the fast kicker magnet; (2) the corresponding pulsed power supply to implement the kicker function; (3) the dynamic magnetic field measurement system based on printed circuit board (PCB) technique.

Design and Test of the Power Supply for a Fast Kicker Magnet

To perform fast beam switch during spot scanning and energy modulation procedure, a fast kicker magnet system is adopted in HUST-PTF (Huazhong University of Science and Technology Proton Therapy Facility). The rising/falling time is expected to be less than 100 μs, and the maximum repetition rate should be up to 500 Hz. To meet the specifications on dynamic response of the power supply, a solution with two separate DC link scheme is present in this paper. Since the Kicker is closed to other sensitive equipment, an output filter is installed to prevent electromagnetic disturbances from propagating along the cables. The optimized design of the output filter and comparison measurement results of the power supply are introduced as well. Here, a trade-off between the voltage oscillation, dynamic performance and engineering implementation has been made.

Measurements of electromagnetic properties of ferrites as a function of frequency and temperature

Fast kicker magnets are used to inject beam into and extract beam out of the CERN accelerator rings. These kickers are often ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. The interaction of the beam with the resistive part of the longitudinal beam coupling impedance leads to power dissipation and heating of different elements in the accelerator ring. In particular, 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. In addition, the imaginary portion of the beam coupling impedance contributes to beam instabilities. A good knowledge of electromagnetic properties of materials up to GHz frequency range is essential for a correct impedance evaluation. This paper presents the results of transmission line measurements of complex initial permeability and permittivity for different ferrite types. We present an approach for deriving electromagnetic properties as a function of both frequency and temperature; this information is required for simulating ferrite behaviour under realistic operating conditions.

Measurements of Electromagnetic Properties of Ferrites as a Function of Frequency and Temperature

Fast kicker magnets are used to inject beam into and extract beam out of the CERN accelerator rings. These kickers are often ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. The interaction of the beam with the resistive part of the longitudinal beam coupling impedance leads to power dissipation and heating of different elements in the accelerator ring. In particular, 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. In addition, the imaginary portion of the beam coupling impedance contributes to beam instabilities. A good knowledge of electromagnetic properties of materials up to GHz frequency range is essential for a correct impedance evaluation. This paper presents the results of transmission line measurements of complex initial permeability and permittivity for different ferrite types. We present an approach for deriving electromagnetic properties as a function of both frequency and temperature; this information is required for simulating ferrite behaviour under realistic operating conditions.

Characterization of pseudosingle bunch kick-and-cancel operational mode

Author(s): Sun, C; Robin, DS; Steier, C; Portmann, G | Abstract: Pseudosingle-bunch kick-and-cancel (PSB-KAC) is a new operational mode at the Advanced Light Source of Lawrence Berkeley National Laboratory that provides full timing and repetition rate control for single x-ray pulse users while being fully transparent to other users of synchrotron radiation light. In this operational mode, a single electron bunch is periodically displaced from a main bunch train by a fast kicker magnet with a user-on-demand repetition rate, creating a single x-ray pulse to be matched to a typical laser excitation pulse rate. This operational mode can significantly improve the signal to noise ratio of single x-ray pulse experiments and drastically reduce dose-induced sample damage rate. It greatly expands the capabilities of synchrotron light sources to carry out dynamics and time-of-flight experiments. In this paper, we carry out extensive characterizations of this PSB-KAC mode both numerically and experimentally. This includes the working principle of this mode, resonance conditions and beam stability, experimental setups, and diagnostic tools and measurements.

The fast extraction kicker for J-PARC with a novel pulse compression system

A fast extraction kicker magnet for the main ring of J-PARC has been developed. A lumped constant type magnet is employed for its structural simplicity and stability in high-voltage operation. A disadvantage of the lumped constant type, a slow rise time, was alleviated by the adoption of a newly developed magnetic pulse compression system. The effectiveness of the magnetic pulse compression system in sharpening the excitation current was confirmed both by a circuit simulation and experimentally. The newly developed fast extraction kicker system was operated successfully with a 30kV charging voltage of the pulsed power supply. The required rise time of less than 1.1μs was achieved in the measurement.

Design and Prototype Test of CSNS/RCS Injection and Extraction Magnets

The China Spallation Neutron Source (CSNS) accelerator consists of a linear accelerator (Linac), a rapid cycle synchrotron (RCS) and two beam transport lines. The injection and extraction systems of the RCS play an important role in connecting these four parts of accelerator. The injection system consists of three sets of bump magnets and two septum magnets, and the extraction system is composed of ten fast kicker magnets and a Lambertson magnet. The design of all these magnets is carefully considered. To prove the design concepts, a prototype bump magnet and a prototype kicker magnet have been successfully developed and tested.

A fast kicker magnet for the PSI 600 MeV proton beam to the PSI ultra-cold neutron source

The new type of ultra-cold neutron source presently under construction at PSI requires the possibility of transporting the full high-intensity proton beam, currently 2 mA, for about 8 s every 800 s onto a spallation target located at the centre of the source. For this purpose, a fast kicker magnet with a rise time (5–95%) of 0.5 ms has been built. The required magnet and power supply have been manufactured at PSI and were installed during a shutdown. A first test of the fast beam switching process, however, for safety reasons with a reduced beam intensity of 20 μ A , was performed successfully.

Hardware R&D of the KEK/JAERI 50 GeV Synchrotron Fast Extraction Kicker Magnets

The fast extraction kicker magnets of the 50 GeV synchrotron are now in an intensive R&D stage. In the 50 GeV ring, the fast extraction system is designed to deliver the 50 GeV beam to the downstream neutrino oscillation experiment beam line with the Super-Kamiokande detector. At the same time, the fast extraction line is required to function as a beam abort, in case of hardware failure during acceleration of the beam from 3 GeV to 50 GeV. In order to fulfill both demands, the extraction system is designed to accommodate bipolar beam extraction. A new technology to make the bipolar kicker magnet system, using a symmetric Blumlein pulse forming network (SBPFN) system, has been introduced. Its validity is being investigated, both theoretically and experimentally. R&D programs aimed at establishing some of the important technical elements in the fast extraction kicker system are presently in progress. This R&D includes experimental studies of the bipolar kicker principle and the development of IGBT switching modules that satisfy full switching capability of the designed current and voltage.

Coupling impedance measurements of a model fast extraction kicker magnet for the SNS accumulator ring

Both longitudinal and transverse coupling impedance of a fast extraction kicker magnet has been measured for the design and development of beam extraction in the Spallation Neutron Source accumulator ring. The conventional wire method with improved techniques is employed in the bench test. The experimental result is explained by and compared with a newly developed resonant circuit model. The impact of the measurement on the fast extraction kicker magnet design is discussed.

Development of fast extraction kicker magnet for booster synchrotron of Indus-1

A fast extraction kicker magnet has been developed, which is used for extracting electron beams of 450 MeV from the 700 MeV Booster synchrotrons and injecting them into Indus-1, a 450 MeV electron storage ring. The fast extraction kicker magnet is of an open C-type lumped magnet design with a field strength of 624 Gauss at 800 Ampere. The fast kicker magnet is excited at a rectangular pulse of current with a rise time of 45 ns. A pulsed magnetic field of 624 G with a rise time of 45 ns and duration of 75 ns was obtained. This paper presents ferrite material selection criteria, magnetic circuit designs, design requirements, fabrication processes and performance results.

Manufacture of fast-pulsed magnets for the SLC damping rings

A second-generation fast kicker magnet (and its power supply) was designed by Fermilab for the SLC (Stanford Linear Collider) electron damping ring. The requirements were to inject and extract two bunches of electrons, with the following magnetic field specifications: integral peak magnetic field=0.021 T-m; rise/fall time (0-100%)=56.03 ns maximum; and 'flat-top' duration=61.63 ns. Many of the early problems with these magnets have been studied intensely, and substantial progress has been made. In particular, vacuum potting with room-temperature curing silicone rubber (RTV) has been refined to give reliable high-voltage service up to 18 kV/mm, and lifetimes of about a year despite stored beam intensities of 3*10/sup 10/ electrons/bunch at 120 pps. Further improvements in RTV formulation are suggested, and the direction of future insulation-system development is indicated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Feasibility study into the use of mechanical choppers to alter the natural time structure of the APS

In standard operating mode, the Advanced Photon Source (APS) is projected to be with 20 equally spaced bunches of positrons separated by 177 ns. This time structure may not be optimal for all experiments, particularly those experiments that require long periods (microseconds to milliseconds) of darkness preceding and/or succeeding the x-ray burst. As a result, an ongoing study is being made into the possibility of altering the natural time structure of the x-ray bursts from the APS. One possibility is through the use of fast kicker magnets (wobblers). A more passive approach is through the use of high-speed mechanical choppers. Using choppers rotating between 18 000 and 20 000 rpm (typical rotational speeds for currently operational neutron choppers), a single burst of x rays can be passed while blocking the surrounding bursts. Interpulse periods are adjustable from approximately 3 to 300 μs depending on the slit configuration of the chopper wheels. Even longer periods of darkness can be achieved by using phased choppers and/or mechanical shutters.

Design of a High Yield Position Source

The Stanford Linear Collider (SLC) requires a positron source with a yield large enough to give equal number of positrons and electrons at the interaction point. In addition, the colliding positrons must have an emittance and bunch length similar to the electron beam. This report describes the design of a high yield positron source to give these characteristics. Reference 1 contains more details of the systems of the SLC and positron source. The overall positron production system in relation to the SLC is shown in Fig. 1. A single bunch of electrons of 33 GeV is extracted from the Linac at the two-thirds point by means of a fast kicker magnet and a pair of septum magnets. The extracted electron beam is transported into the positron vault where it is focused to a spot size of + or -0.6 mm at the target. Spoiler foils are placed in the extracted beam path to increase the emittance so that the spot size cannot be made so small that target damage would occur. Positrons are collected in a focusing solenoid system using an iron shaped solenoidal field of 1 Tesla at the target and a pulsed solenoidal field from a flux concentratormore » with a peak field of 5 Tesla. The positron beam emerging from the focusing solenoid system is accelerated to 200 MeV in a 1.5 meter high-gradient-accelerator of 50 MeV/meter and three 3.05 m standard accelerator sections. The positrons are contained in the accelerator aperture using a 0.5 Tesla solenoidal field in the beginning and quadrupole focusing in the final two standard accelerator sections. The positrons are then transported back to the beginning of the Linac for further acceleration to 1.2 GeV, whereupon they are sent to the positron damping ring. Later they are removed from the damping ring, accelerated to the end of the Linac, and transported around the e/sup +/ arc to the interaction point.« less

Fast kicker magnet system

A fast kicker magnet system has been developed to be used as a fast extraction device for electrons in a synchrotron. Measurements on pulse characteristics are presented.

Magnet systems for the Daresbury synchrotron radiation source

The design, production and testing of the main dipole and quadrupole magnets for a 2 GeV electron storage ring are described, with particular emphasis on the integrated field performance including the optimisation of magnet ends. In addition fast pulsed kicker and septum magnets for control of injection and extraction processes in both the storage ring and its booster synchrotron injector are treated. All magnets are now installed and operating routinely in the new Synchrotron Radiation Source at Daresbury.