Magnetic Alloy Cores Research Articles

Magnetic Alloy Core Loaded 2nd harmonic cavity design and testing for CSNS-II RCS

In this report, we present our recent progress in the design and high-power testing of the 2nd harmonic cavity for the China Spallation Neutron Source upgrade project. To achieve optimal performance, high-performance magnetic alloy (MA) cores with dimensions of Φ850mm × Φ316mm × 25mm were meticulously developed and fabricated to serve as the load material for the radio-frequency (RF) cavity. Through rigorous testing, we were able to achieve a remarkable cavity accelerating gradient of over 40 kV/m under 15% duty cycle. To ensure optimal cooling efficiency, we conducted a comprehensive fluid dynamics simulation analysis and verified our results through experiments. Finally, to assess the long-term stability and performance of the cavity, we conducted a series of extended operation tests. These experiments successfully confirmed the high-performance capabilities and exceptional stability of the 2nd harmonic cavity.

Design and verification of a high-gradient and high-power 2nd harmonic cavity for the China Spallation Neutron Source upgrade project

Here, we report our recent progress in the design, fluid thermodynamics simulation, and high-power test of the2nd harmonic cavity for the China Spallation Neutron Source Phase II. A high-performance and large-size magnetic alloy (MA) core was developed as the load material for the radiofrequency cavity to achieve a high gradient of 40 kV/m. The water-cooling structure and cooling efficiency were studied and improved through numerical analysis and thermal experiments. The long-term stability of the cavity, especially the waterproofness of the MA cores with high heat load, was verified by high power tests.

Synthesis of α-Fe2O3 nanoparticles from soft magnetic FeSiAl alloy cores of spent printed circuit boards and their application in visible-light-driven degradation of methylene blue dye

This study aims at 3R recovery, reuse, and recycling of metals from spent printed circuit boards (PCBs). Here, soft magnetic FeSiAl alloy cores of spent PCBs were used to synthesize α-Fe2O3 nanoparticles (NPs) for visible-light-driven degradation of methylene blue (MB) dye. The α-Fe2O3 NPs were synthesized by dissolving FeSiAl in a mixture of mild organic acids such as citric acid and ascorbic acid. The α-Fe2O3 NPs were characterized by powder XRD, TG-DSC, FESEM-EDX, HRTEM, UV–Vis DRS, and BET isotherm. The synthesized α-Fe2O3 NPs were flat spindle shaped and a few were oval with a particle size between 20 and 30 nm. Under visible light irradiation, the α-Fe2O3 NPs showed high efficiency for the degradation of MB dye in the presence of H2O2. To get optimum conditions, various experiments such as catalyst dosage, volume of H2O2, [MB], and nature of light were studied. Thus, it can be proposed that the present study is simple, environmentally benign, and highly efficient for the synthesis of α-Fe2O3 NPs and subsequent degradation of MB dye.

Development of medium-frequency cavity loaded with multi-ring magnetic alloy cores cooled by chemically inert liquid

Magnetic alloys (MAs) are commonly applied in the radio-frequency (RF) cavities of proton synchrotrons. The high saturation permeability and Curie temperature of MAs facilitate the development of RF cavities with large accelerating gradients that could not be achieved with ferrite. The conventional MA core is a disk-shaped toroid made by winding MA ribbons. Here, we propose a multi-ring core structure that consists of three concentrically arranged toroidal ring cores of different radial sizes. Neither epoxy resin impregnation nor a waterproof coating is applied to the cores, and thus the thermal stress during high-power operation is expected to be relaxed. A set of multi-ring cores is sandwiched between two glass-epoxy plates with flow channels. This modular structure increases the velocity of the coolant flow, making the flow turbulent to obtain the desired cooling efficiency. Coolant-induced corrosion of the Fe-based MA is prevented by adopting a low-viscosity, chemically inert, and electrically insulating liquid. The RF and thermal designs of a cavity loaded with multi-ring cores are presented and two types of test cavity are developed. A series of high-power tests demonstrate stable operation with the designed performance. The results of experimental performance tests for two cavities loaded with multi-ring MA cores cooled by a chemically inert liquid are reported.

Design of the deceleration magnetic alloy cavity for a high-intensity heavy-ion accelerator facility Spectrometer Ring

The construction of the high-intensity heavy-ion accelerator facility (HIAF) Yang et al. (2013) [1] at the Institute of Modern Physics, Chinese Academy of Science (IMP, CAS), has begun recently in Huizhou, Guangdong province, China. One of the devices of the HIAF is the Spectrometer Ring (SRing). Designed with two magnetic alloy (MA) loaded cavities to decelerate the heavy-ion beams, such as a 238U+92 beam from 800 to 30 MeV/u, the SRing will serve as a multi-functional experimental storage ring. The MA cavity design works in the frequency range of 1.006-0.503 MHz with a maximum voltage of 50 kV and peak power of 220 kW. This study describes the variable-harmonic RF deceleration cavity design and a performance test of Chinese MA cores.

Etoposide-Bound Magnetic Nanoparticles Designed for Remote Targeting of Cancer Cells Disseminated Within Cerebrospinal Fluid Pathways.

Magnetic nanoparticles (MNPs) have potential for enhancing drug delivery in selected cancer patients, including those which have cells that have disseminated within cerebrospinal fluid (CSF) pathways. Here, we present data related to the creation and in vitro use of new two-part MNPs consisting of magnetic gold-iron alloy cores which have streptavidin binding sites, and are coated with biotinylated etoposide. Etoposide was chosen due to its previous use in the CSF and ease of biotinylation. Etoposide magnetic nanoparticles (“Etop-MNPs”) were characterized by several different methods, and moved at a distance by surface-walking of MNP clusters, which occurs in response to a rotating permanent magnet. Human cell lines including D283 (medulloblastoma), U138 (glioblastoma), and H2122 (lung adenocarcinoma) were treated with direct application of Etop-MNPs (and control particles), and after remote particle movement. Cell viability was determined by MTT assay and trypan blue exclusion. Results indicated that the biotinylated etoposide was successfully bound to the base MNPs, with the hybrid particle attaining a maximum velocity of 0.13 ± 0.018 cm/sec. Etop-MNPs killed cancer cells in a dose-dependent fashion, with 50 ± 6.8% cell killing of D283 cells (for example) with 24 h of treatment after remote targeting. U138 and H2122 cells were found to be even more susceptible to the killing effect of Etop-MNPs than D283 cells. These findings indicate that the novel Etop-MNPs have a cytotoxic effect, and can be moved relatively rapidly at physiologic distances, using a rotating magnet. While further testing is needed, intrathecal administration of Etop-MNPs holds promise for magnetically-enhanced eradication of cancer cells distributed within CSF pathways, particularly if given early in the course of the disease.

Design and test of an RF acceleration system loaded with magnetic alloy for the proton synchrotron of the Xi’an Proton Application Facility

The Xi’an Proton Application Facility (XiPAF) is a facility dedicated to the experimental simulation of the space radiation environment. The facility uses a compact synchrotron as its final-stage accelerator. The synchrotron can accelerate a proton beam from 7 to $$230\,\hbox {MeV}$$ . Physical design results show that the radio frequency (RF) acceleration system should work in the frequency range of $$1{-}6\,\hbox {MHz}$$ and provide a maximum voltage of $$>800\,\hbox {V}$$ . To dilute the strong space charge effect during the injection period, we also aim to achieve multiharmonic acceleration. A compact RF acceleration system loaded with magnetic alloy cores has been designed and developed to fulfill these requirements. The preliminary test results show that the system can work normally with a gap voltage of $$800\,\hbox {V}$$ . With a further RF power upgrade, the voltage can be improved to $$>1.2\,\hbox {kV}$$ .

Measurement of thermal deformation of magnetic alloy cores of radio frequency cavities in 3-GeV rapid-cycling synchrotron of Japan proton accelerator research complex

Magnetic alloy cores loaded in radio frequency cavities are employed to achieve a high field gradient in the 3-GeV Rapid-Cycling Synchrotron of the Japan Proton Accelerator Research Complex. We use three core-types, which were manufactured in three different processes. Buckling occurred in some cores of only one of the three core types. In order to find out the mechanism of buckling, we measured thermal deformations of the two core types, which had not buckled and the core types, which had buckled, while changing their temperatures by RF heating in air. Furthermore, we calculated the thermal stress using the results of the experiments. These experiments yielded that there was no remarkable difference in the strength of thermal stress between the core types, which had not buckled, and the core types, which had buckled; however, that there was a clear difference in the behavior of thermal deformations. The local deformations appeared, when a certain temperature was exceeded, and accelerated with temperature rise in the buckled core types. This was not seen with core types that did not show the buckling problem. We conclude that the repetition of these catastrophic and local deformations, which are accelerated with the temperature rises, lead to the buckling.

Study of a magnetic alloy-loaded cavity for compact synchrotrons**Supported by National Natural Science Foundation of China (11175194)

Magnetic alloy (MA)-loaded cavities have been widely used in compact proton and heavy-ion synchrotrons, and the MA core is the key issue in their development. Chinese-produced MA has never yet been adopted as core material for an MA-loaded cavity. To use Chinese-produced MA as the core material, it is necessary to study its properties, and compare with MA material produced elsewhere. In this paper, the properties of several MA cores made of Chinese-produced material are measured. Based on the measured results, a schematic design is produced for a cavity which could obtain 1 kV gap voltage with less than 1.5 kW power dissipation in the frequency range of 0.5–7 MHz. The difference between resonant frequencies obtained from simulation and analytical results is less than 10%.

Mechanisms of increasing of the magnetic alloy core shunt impedance by applying a transverse magnetic field during annealing

In the J-PARC synchrotrons, Magnetic Alloy (MA) cores loaded RF cavities are employed to achieve a high field gradient. We are successful to increase the shunt impedance of the MA cores for the Main Ring synchrotron RF cavities by reducing the ribbon thickness and applying a transverse magnetic field during annealing. In this paper, we study the effects of transverse field annealing on the MA core shunt impedance by comparing two kinds of MA cores, those are the FT3M core that is annealed without any magnetic fields and the FT3L core that is annealed with a transverse magnetic field. The FT3L core shows the higher shunt impedance than the FT3M core. By applying the transverse magnetic field during annealing, the magnetization processes of the FT3L core occur by mainly magnetization rotations, and consequently the core loss is reduced and the relative complex permeability shows an excellent frequency behavior. The MA core shunt impedance is increased by those improvements of the magnetic properties.

Ribbon thickness dependence of the Magnetic Alloy core characteristics in the accelerating frequency region of the J-PARC synchrotrons

We employ Magnetic Alloy (MA) core loaded RF cavities for the J-PARC synchrotrons to achieve a high field gradient. The MA core has a laminated structure of 18μm thick ribbon layers. We have been developing high shunt impedance MA cores to prepare for an increase of beam power. At low frequencies, it is well known that the eddy current loss in the ribbon is proportional to the square of the ribbon thickness. The MA core shunt impedance can be increased by using thinner ribbons. On the other hand, at high frequencies, the MA core magnetic characteristics are largely different from low frequencies. Using thinner ribbons might be effective to increase the MA core shunt impedance in the accelerating frequency region of the J-PARC synchrotrons. We reviewed the theoretical calculations of the ribbon thickness dependence of the MA core magnetic characteristics and we derived the ribbon thickness dependence from measured data. The measured data show that the MA core shunt impedance is inversely proportional to the ribbon thickness in the accelerating frequency region of the J-PARC synchrotrons, which is consistent with our calculations.

Numerical analysis and experiment to identify origin of buckling in rapid cycling synchrotron core

The accelerating cavities used in the rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) are loaded with magnetic alloy (MA) cores. Over lengthly periods of RCS operation, significant reductions in the impedance of the cavities resulting from the buckling of the cores were observed. A series of thermal structural simulations and compressive strength tests showed that the buckling can be attributed to the low-viscosity epoxy resin impregnation of the MA core that causes the stiffening of the originally flexible MA–ribbon–wound core. Our results showed that thermal stress can be effectively reduced upon using a core that is not epoxy-impregnated.

Passive protections against breakdowns between accelerating grids in SPIDER experiment

In the SPIDER experiment a ITER-like full size plasma source will be realized with the target to extract a Dˉ beam of 70 A and then to accelerate it to 100 keV energy. The reduction of the effects due to the frequent breakdowns between the accelerating grids is needed, because of grids damage due to energy deposition by arcing and strong electromagnetic noise (EMI) emission. The solution proposed is a comprehensive design of the circuit. Two passive components are installed: a Damping Resistor and an Output Filter in series to the Power Supplies. Then a doubled screened structure will be adopted for the 30 m long – 100 kV Transmission Line TL, which connects the Ion Source and Acceleration Power Supplies to their loads: the Inner Screen will be connected to the reference ground (the vessel) by a resistive link, the Outer Screen acting as a low-impedance ground. Finally, a Distributed Core Snubber DCS (magnetic snubber) will be installed onto the TL, aimed to increase the damping of the oscillations due to the stray inductances and capacitances. The DCS is composed of 10 magnetic alloy cores and is equipped by a biasing circuit to enhance the flux swing in unsaturated condition during the breakdown. A detailed model of the circuit is developed to evaluate the passive components parameters for protection against breakdown, in which all the magnetic and capacitive couplings between components are modeled as well as the magnetic core snubber saturation.

Study of a magnetic alloy-loaded RF cavity for bunch compression at the CSR

The Heavy Ion Research Facility and Cooling Storage Ring (HIRFL-CSR) accelerator in Lanzhou offers a unique possibility for the generation of high density and short pulse heavy ion beams by non-adiabatic bunch compression longitudinally, which is implemented by a fast jump of the RF-voltage amplitude. For this purpose, an RF cavity with high electric field gradient loaded with Magnetic Alloy cores has been developed. The results show that the resonant frequency range of the single-gap RF cavity is from 1.13 MHz to 1.42 MHz, and a maximum RF voltage of 40 kV with a total length of 100 cm can be obtained, which can be used to compress heavy ion beams of 238U72+ with 250 MeV/u from the initial bunch length of 200 ns to 50 ns with the coaction of the two single-gap RF cavity mentioned above.

The origin of magnetic alloy core buckling in J-PARC 3 GeV RCS

We have been operating ten RF cavities loaded with magnetic alloy (MA) cores with a high field gradient of more than 20 kV/m in Japan Proton Accelerator Research Complex (J-PARC) 3 GeV Rapid Cycling Synchrotron (RCS) since September 2007. During 3 years operation, we detected three times the impedance reductions of RF cavities resulting from the buckling of MA cores. To find out the origin of the MA core buckling, we evaluated the thermal stress inside the MA cores in operation and studied the relationship between the MA core buckling and core structure. We figured out that the MA core buckling was caused by the thermal stress that was enhanced due to the impregnation with low viscosity epoxy resin. We improved the MA cores without the low viscosity epoxy resin impregnation and replaced all the cores in one RF cavity with them in March 2010. Up to now we operated the RF cavity loaded with the improved MA cores for 1500 h, it showed no impedance reduction and no buckling.

Development of RF acceleration system for 150 MeV FFAG accelerator

An RF accelerating system was developed for the 150 MeV FFAG accelerator to demonstrate rapid cycling acceleration. The 150 MeV FFAG accelerator has been developed as a prototype for various applications, such as proton cancer therapy. To achieve rapid cycling acceleration, a high-field gradient and a broadband impedance of the RF cavity were necessary. Therefore, we employed a magnetic alloy (MA) for a core material. The required field gradient and the bandwidth were 35 kV/m and 3.0 ± 1.5 MHz , respectively. Because of the strong fringing field of the focusing magnets of the FFAG accelerator, the RF cavity had to be magnetically shielded. An effective cooling system for the MA cores was also needed because of the large power dissipation of more than 1 W / cm 3 . We have developed an RF system satisfying these requirements and successfully demonstrated a rapid cycling acceleration of 100 Hz.

Broadband Buncher Cavity for Beam Transport Line of HiECR Ion Source

A newly developed rf buncher has been installed in the beam transport line of an electron cyclotron resonance (ECR) ion source, HiECR, at the Center for Nuclear Study (CNS) of the University of Tokyo. The rf buncher is a compact cavity having magnetic alloy (MA) cores and operates in the wide frequency range between 18 and 45 MHz without any tuning systems. Bunched beams of H+, O5+, and Ar8+ ions have been produced successfully and measured using a newly designed Faraday cup with good time resolution. In this paper, the design of the MA-loaded buncher cavity and the results of the beam test are presented. A detailed description of the HiECR beam transport line and the design of the new Faraday cup are also given.

Broadband “in-series multistation” rf cavity with low voltage standing wave ratio

A configuration for an untuned broadband rf cavity with a low-voltage standing wave ratio (VSWR) is proposed. Although an untuned broadband cavity is currently implemented by loading magnetic alloy (MA) cores, the VSWR of such a cavity is expected to be no less than approximately 2.0 in the operational frequencies sweeping by a factor of about 10. A type of rf cavity, “in-series multistation” cavity, described here can cover a much broader frequency range sweeping by a factor of 20, while keeping the VSWR value below 1.2. The system consists of multiple stations, each of which is loaded with low-Q high-permeability MA cores. A “bench” test circuit was built and successfully tested.

Indirect “one-side” cooling method of a magnetic-alloy–loaded rf cavity

For magnetic alloy (MA) loaded rf accelerating cavity, we have developed an indirect cooling system, which is effective for retaining its shunt impedance by cooling only one side of the MA cores. Because of its low-$Q$ high-permeability property, MA cores are suitable for constructing untuned broadband accelerating systems. Since these same cores are made of wound thin tape, the key to establishing an untuned broadband cavity with effective indirect cooling method is to suppress the reduction of core impedance when attaching metallic cooling plates to the core and keeping a good thermal contact between them. We have employed indium bonding to thermally connect both cores and cooling plates. Both cooling and endurance tests have demonstrated its successful results.

Measurement of RF characteristics of magnetic alloys for an RF cavity of the accumulator cooler ring

The magnetic alloy (MA)-loaded RF cavity has been studied for an RF stacking system of the accumulator cooler ring (ACR). RF characteristics of several high-permeability MA cores were measured in the frequency range between 1 and 50MHz. The effects of the cut-core configuration, cutting the core and leaving air gaps between two circular halves, were also investigated. The results show that the shunt impedance remains high and the appropriate inductance and Q-value can be obtained by increasing the gap width of the cut core in the frequency region of the ACR cavity.