The Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) has been engaged the conceptual design and prototype coil development for the main coil of the whole-body 14 T magnetic resonance imaging (MRI) superconducting magnet since 2017. In order to improve the thermal and mechanical stability of the coil, a type of conductor called Rutherford cable-in-channel (RIC) will be used in the main coil of the 14 T MRI magnet system. The Rutherford cable is the core component of the RIC conductor. Assessing the electromagnetic performance of the Rutherford cable under operating conditions allows prediction and evaluation of the performance of RIC conductors and 14 T MRI magnets. In order to verify the critical performance of the Rutherford cable, a 2-layer, 2-turn (2 x 2) insert coil was manufactured and tested under a WM3 (maximum magnetic field of 20 T) resistive magnet at the High Magnetic Field Laboratory of the Chinese Academy of Science (CHMFL). The insert coil reaches a critical current of 3489.2 A with n-value of 24.39 after 12 times of quench training under a 14 T background field. The joint resistance is around 20 n Omega. The design, fabrication, testing and analysis of 2 x 2 insert coil will be presented in this paper.

In order to accommodate the luminosity improvement strategy, two superconducting 499.8 MHz radio frequency (rf) cavities have been adopted for the Upgrade project of Beijing Electron Positron Collider (BEPCII), a double-ring electron-positron collider as well as a synchrotron radiation (SR) light source. The in-house development of the 499.8 MHz superconducting cavity system was initiated at IHEP since 2008. One prototype niobium cavity with all the parts except for the flanges and the pickup port formed by spinning was fabricated and then vertical-tested successfully in July 2011. Four prototype input couplers were manufactured and high-power tested with one reaching a maximum rf power of continuous wave (cw) 420 kW. One prototype HOM damper with a satisfactory absorbing efficiency at the desired frequency band was also constructed and high power tested up to cw 4.4 kW. In the meanwhile, a frequency tuner consisting of a stepping motor and a piezoelectric oscillator was developed. Finally, the bare cavity was dressed with one input coupler, two HOM dampers and one frequency tuner, mounted in a domestic-developed cryostat and then high-power tested successfully in Oct. 2011. The achieved accelerating voltage is 2.2 MV with corresponding Q(0) measured to be 5.8 x 10(8), beyond the designed goal. This is the first in-house developed 499.8 MHz HOM-damped superconducting cavity system in China. The design, fabrication, post processing and tests of the niobium bare cavity and its auxiliaries, as well as the horizontal high-power test of the cavity system are presented.

The Beijing Electron Positron Collider (BEPCII) is a high-brightness collider and operates in compatible mode of synchronous light source. This summer, BEPCII spare cavity, which was all made in China, had been put into BEPCII operation, and the LLRF system for the spare cavity was also upgraded at the time.

The invention discloses a low-temperature insertion rod tuner and a superconducting cavity. The low-temperature insertion rod tuner comprises an insertion rod assembly and an adjusting assembly; the insertion rod assembly comprises a first telescopic device and an insertion rod, the upper end of the first telescopic device is connected with the adjusting assembly through a top flange, and the lower end of the first telescopic device is used for sealed connection with an opening arranged on the superconducting cavity, so that a closed system is formed between the insertion rod assembly and thesuperconducting cavity; and the adjusting assembly controls telescoping of the first telescopic device, and controls the length of the insertion rod in the first telescopic device inserted into the superconducting cavity. The low-temperature insertion rod tuner provided by the invention is relatively compact in structure, and the superconducting cavity body is not required to be deformed, and acting force required for frequency tuning is small. The tuning range of the tuner is directly determined by the amount of compression or stretching of a bellows, and the frequency of the superconductingcavity can be adjusted in a relatively large range.

A 2 x 4-cell superconducting linac module for the THz-FEL facility has been developed at the China Academy of Engineering Physics, which is expected to provide 6-8 MeV quasi-CW electron beams with an average current of 1-5 mA. The module consists of two 4-cell SRF cavities, two main couplers, two tuners and a cryostat. The design, fabrication and performance test of these components is presented in this paper. The test results reveal that all these components have reached their design goals and the module has also been assembled and horizontal tested at Chengdu. The gradients of both cavities at 2 K reach 10 MV/m, which meets our requirements. Currently beam-loading commissioning is underway. (C) 2017 Elsevier B.V. All rights reserved.

The Superconducting Radio Frequency (SRF) system of the upgrade project of the Beijing Electron Positron Collider (BEPCII) has been in operation for almost 8 years. During operation, many problems have been encountered, such as excessive heating of the power couplers, frequent beam trips during high intensity colliding, false arc interlock trigger and so on. Among them, some has been solved successfully, some have been alleviated. This paper will describe some experiences with BEPCII SRF system operation, including the symptoms, causes and solutions of problems.

A new tuner control system for spoke superconducting radio frequency (SRF) cavities has been developed and applied to cryomodule I of the C-ADS injector I at the Institute of High Energy Physics, Chinese Academy of Sciences. We have successfully implemented the tuner controller based on Programmable Logic Controller (PLC) for the first time and achieved a cavity tuning phase error of ±0.7° (about ±4 Hz peak to peak) in the presence of electromechanical coupled resonance. This paper presents preliminary experimental results based on the PLC tuner controller under proton beam commissioning.

Peking University is developing a 1.3 GHz superconducting accelerating section highpower THz free-electron laser for the China Academy of Engineering Physics (CAEP). A compact fast/slow tuner has been developed by the Institute of High Energy Physics (IHEP) for the accelerating section to control Lorentz detuning, compensate for beam loading effect, microphonics and liquid helium pressure fluctuations. The tuner design, warm test and cold test of the first prototype are presented, which has a guiding significance for the manufacture of the formal tuner and cryomodule assembly.

IHEP started the 1.3 GHz SRF technology R&D in 2006 and recently enters the stage of integration and industrialization. After successfully making several single cell and 9-cell cavities of different shape and material, we designed and assembled a short cryomodule containing one large grain low-loss shape 9-cell cavity with an input coupler and a tuner etc. This module will perform horizontal test in 2016 with the newly commissioned 1.3 GHz 5 MW klystron and the 2 K cryogenic system. Beam test with a DC photocathode gun is also foreseen in the near future. We report here the problems, key findings and improvements in cavity dressing, clean room assembly, cryomodule assembly and the liquid nitrogen cool down test. A fine grain TESLA 9-cell cavity is also under fabrication in a company as the industrialization study.

In the digital low level RF (LLRF) system of a circular (particle) accelerator, the RF field signal is usually down converted to a fixed intermediate frequency (IF). The ratio of IF and sampling frequency determines the processing required, and differs in various LLRF systems. It is generally desirable to design a universally compatible architecture for different IFs with no change to the sampling frequency and algorithm. A new RF detection method based on a double heterodyne architecture for wide IF range has been developed, which achieves the high accuracy requirement of modern LLRF. In this paper, the relation of IF and phase error is systematically analyzed for the first time and verified by experiments. The effects of temperature drift for 16 h IF detection are inhibited by the amplitude and phase calibrations.

The Half-Wave Resonator (HWR) has been widely used in proton and heavy ion accelerators, for it has particular advantages of accelerating low energy charged particles. Preliminary design of a 325 MHz β=0.12 superconducting HWR cavity has been proposed at Institute of High Energy Physics (IHEP). The basic geometric parameters choices of the cavity are based upon theoretical model and numerical calculation, and then the RF performances are optimized by extensive electromagnetic simulations. In this paper, the detailed mechanical analysis, frequency control, and the considerations for fabrication of the 325 MHz HWR cavity are also presented.

The tuning system plays a very important role when a superconducting cavity is in operation. It cooperates with other control loops to adjust the cavity frequency with high precision, reduce the reflection power, guarantee the stability of beam, and ensure the safety of the superconducting cavity. This paper focuses mainly on the tuning system working principle, the working state and problems that Beijing Electron Positron Collider (BEPC II) has encountered during operation.

The Accelerator Driven Sub-critical System （ADS） is under development and aims at the safe disposal of nuclear waste and providing electric power in China. The main accelerator of the ADS is composed of two injector sections and one main linear acceleration section. The 650 MHz β=0.82 superconducting cavities will be adopted to accelerate the proton bunches from 360 MeV to 1.5 GeV in the medium energy section. This paper presents the study and design results of this kind of superconducting cavity.

Since Nov. 2006, the 500MHz SRF system of Beijing electron positron collider upgrade (BEPCII) has been running stably. But there’s a hidden danger for no spare cavity is existed. If there’s any serious trouble happened on either one of the two operating cavities and cannot be recovered in time, it will affect the operation of BEPCII facility. Spare cavities began to be investigated since 2009. Now three cavities are developed and two of them have been vertical tested at Jan and July 2011, respectively. This paper will briefly present the manufacturing, post-processing and vertical test performance of the cavity.

Research and development of a 1.3 GHz 9-cell cavity test cryomodule were carried out by a collaboration group between IHEP (Institute of High Energy Physics) and TIPC (Technical Institute of Physics and Chemistry) in China. The cryomodule is a 'test model' for the ILC cryomodule, and a key component of a superconducting accelerator test unit which will be built in the near future, also can be used as a horizontal test facility for 1.3 GHz 9-cell cavities. This paper presents the development status of the cryomodule, including structure design, cryogenic flow diagram, thermal and mechanical simulations, heat load estimation and etc.