Development of a high gradient rf system using a nanocrystalline soft magnetic alloy

Abstract

The future high intensity upgrade project of the J-PARC (Japan Proton Accelerator Research Complex) MR (Main Ring) includes developments of high gradient rf cavities and magnet power supplies for high repetition rate. The scenario describing the cavity replacements is reported. By the replacement plan, the total acceleration voltage will be almost doubled, while the number of rf stations remains the same. The key issue is the development of a high gradient rf system using high impedance magnetic alloy, FT3L. The FT3L is produced by the transverse magnetic field annealing although the present cavity for the J-PARC adopts the magnetic alloy, FT3M, which is annealed without magnetic field. After the test production using a large spectrometer magnet in 2011, a dedicated production system for the FT3L cores was assembled in 2012. This setup demonstrated that we can produce material with 2 times higher 0 p Qf product compared to the cores used for present cavities. In this summer, the production system was moved to the company from J-PARC and is used for mass production of 280 FT3L cores for the J-PARC MR. The cores produced in the first test production are already used for standard machine operation. The operation experience shows that the power loss in the cores was reduced significantly as expected.

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

“…The dual harmonic voltage operation curves.. The use of magnetic alloy (MA) cores as loading material for RF cavities is widespread due to their high saturation flux density, contributing to achieving high gradient [3]. Additionally, the low Q-product property of MA cores allows for a wideband property, enabling the establishment of a simpler RF system without tuning loops.…”

Development of Radiation-Hard Solid-State Amplifiers for Kilogray Environments Using COTS Components

“…Digital Object Identifier 10.1109/TNS.2019.2937603 magnetic alloy-loaded system [5] using Finemet [6], [7] will be installed in the straight sections, and its large instantaneous bandwidth (0.5-20 MHz) covers the frequency band of all the required harmonics [8], [9]. As the PSB consists of four superimposed accelerator rings, the RF system is made of four stacked systems assemblies.…”

Harmonic ratcheting for fast acceleration

“…These properties allow MA cavities to achieve low Q values, meaning they can support fast, broadband acceleration using feedforward systems to achieve the desired frequency band operation, as seen in the J-PARC 3 GeV RCS [13]. This low Q value combined with the robust nature of the material allows MA cavities to achieve high gradients, but at the cost of high power requirements, especially at low frequencies wherein the μQf product can be orders of magnitude lower than in ferrite cavities [8]. Despite the resilience of MA cores to FIG.…”

“…In lieu of ferrite, magnetic alloy (MA) cavities have been designed and used for high power rapid cycling synchrotrons [8].…”