Huan Jia

The design simulation of the superconducting section in the ADS injector II

The high-current superconducting proton linac is being studied for the accelerator-driven system (ADS) project undertaken by the Chinese Academy of Sciences. The injector II will be operated at 162.5 MHz, and the proton out from the RFQ with an energy of 2.5 MeV will be accelerated to 10 MeV by two cryo-modules, which are composed of eight superconducting half wave resonance cavities and nine solenoids. In this paper, the design and beam simulation of the superconducting section of the injector II, the acceptance calculation and a stability analysis are presented.

Design and construction of the MEBT1 for CADS injector scheme II

A Medium Energy Beam Transport line 1 (MEBT1) has been designed for Injector Scheme II of the China ADS project. To match the beam from RFQ to Superconducting (SC) Half Wave Resonator (HWR) sections with emittance preservation, the MEBT1 has been designed to be mechanically compact. Working at 162.5 MHz, the MEBT1 transports a 10 mA, 2.1 MeV proton beam using seven quadrupoles and two bunching cavities within 2.7 meters. Three collimators are placed between every two adjacent quadrupoles to collimate the beam halo. Design and construction of the MEBT1 are presented in this paper.

End-to-end simulation of the C-ADS Injector II with a 3-D field map

The Injector II, one of the two parallel injectors of the high-current superconducting proton driver linac for the China Accelerator-Driven System (C-ADS) project, is being designed and constructed by the Institute of Modern Physics. At present, the design work for the injector is almost finished. End-to-end simulation has been carried out using the TRACK multiparticle simulation code to check the match between each acceleration section and the performance of the injector as a whole. Moreover, multiparticle simulations with all kinds of errors and misalignments have been performed to define the requirements of each device. The simulation results indicate that the lattice design is robust. In this paper, the results of end-to-end simulation and error simulation with a 3-D field map are presented.

A new compact structure for a high intensity low-energy heavy-ion accelerator

A new compact accelerating structure named Hybrid RFQ is proposed to accelerate a high-intensity low-energy heavy ion beam in HISCL (High Intensive heavy ion SuperConducting Linear accelerator), which is an injector of HIAF (Heavy Ion Advanced Research Facility). It is combined by an alternative series of acceleration gaps and RFQ sections. The proposed structure has a high accelerating ability compared with a conventional RFQ and is more compact than traditional DTLs. A Hybrid RFQ is designed to accelerate U-238(34+) from 0.38 MeV/u to 1.33 MeV/u. The operation frequency is described to be 81.25 MHz at CW (continuous wave) mode. The design beam current is 1.0 mA. The results of beam dynamics and RF simulation of the Hybrid RFQ show that the structure has a good performance at the energy range for ion acceleration. The emittance growth is less than 5% in both directions and the RF power is less than 150 kW. In this paper, the results of beam dynamics and RF simulation of the Hybrid RFQ are presented.

Capacitive beam position monitors for the low-β beam of the Chinese ADS proton linac*

Beam Position Monitors (BPMs) for the low-beta beam of the Chinese Accelerator Driven Subcritical system (CADS) Proton linac are of the capacitive pick-up type. They provide higher output signals than that of the inductive type. This paper will describe the design and tests of the capacitive BPM system for the low-beta proton linac, including the pick-ups, the test bench and the read-out electronics. The tests done with an actual proton beam show a good agreement between the measurements and the simulations in the time domain.

Development of bunch shape monitor for high-intensity beam on the China ADS proton LINAC Injector II

The development, performance, and testing of the longitudinal bunch shape monitor, namely, the Fast Faraday Cup (FFC), are presented in this paper. The FFC is an invasive instrument controlled by a stepper motor, and its principle of operation is based on a strip line structure. The longitudinal bunch shape was determined by sampling a small part of the beam hitting the strip line through a 1-mm hole. The rise time of the detector reached 24 ps. To accommodate experiments that utilize high-intensity beams, the materials of the bunch shape monitor were chosen to sustain high temperatures. Water cooling was also integrated in the detector system to enhance heat transfer and prevent thermal damage. We also present an analysis of the heating caused by the beam. The bunch shape monitor has been installed and commissioned at the China ADS proton LINAC Injector II.

Study of medium beta elliptical cavities for CADS

The China Accelerator-Driven Sub-critical System (CADS) is a high intensity proton facility to dispose of nuclear waste and generate electric power. CADS is based on a 1.5 GeV, 10 mA CW superconducting (SC) linac as a driver. The high energy section of the linac is composed of two families of SC elliptical cavities which are designed with geometrical beta 0.63 and 0.82. In this paper, the 650 MHz β=0.63 SC elliptical cavity is studied, including cavity optimization, multipacting, high order modes (HOMs) and generator RF power calculation.The China Accelerator Driven Sub-critical System (CADS) is a high intensity proton facility to dispose of nuclear waste and generate electric power. CADS is based on 1.5GeV, 10mA CW superconducting (SC) linac as a driver. The high-energy section of the linac is compose of two families of SC elliptical cavities which are designed for the geometrical beta 0.63 and 0.82. In this paper, the 650 MHz \b{eta}=0.63 SC elliptical cavity was studied including cavity optimization, multipacting, high order modes (HOMs) and generator RF power calculation. Keywords: high current, medium beta, ADS, superconducting cavity, HOMsThe China Accelerator-Driven Sub-critical System(CADS) is a high intensity proton facility to dispose of nuclear waste and generate electric power.CADS is based on a 1.5 GeV,10 mA CW superconducting(SC) linac as a driver.The high energy section of the linac is composed of two families of SC elliptical cavities which are designed with geometrical beta 0.63 and 0.82.In this paper,the 650 MHz β=0.63 SC elliptical cavity is studied,including cavity optimization,multipacting,high order modes(HOMs) and generator RF power calculation.

Conceptual Design of LEBT for C-ADS Linac Accelerator

In order to avoid the hybrid ions like H2, H3 injecting into the RFQ and the residual gas H2 tracing through the RFQ which may lead the RFQ cavity performance degradation, we present the conceptual design of the Low Energy Beam Transport (LEBT) for the China Accelerator Driven Sub-Critical reactor system (C-ADS) accelerator. The LEBT, consisting of one bending magnet and three solenoids and four short-drift sections, match the CW proton beam with 35KeV and 10mA to the entrance of a radio frequency quadrupole (RFQ). This bending LEBT can easily separate the unwanted ions. With the edge angles and one quadrupole to correct the beam asymmetry causing by the bending magnet, the simulation results meet the RFQ entrance requirements.

Development and test of ADS injector II RFQ accelerator

The injector II RFQ accelerator of ADS is used to accelerate protons of 10 mA from 35 keV to 2.1 MeV. The cavity structure of the RFQ is the same as that of the SNS RFQ which has a square cross section, and it adopts π-mode rods to enhance the RF (radio frequency) stability of the cavity. Low power tests show that the flatness of the cavity is better than ±0.01 and the unloaded Q value is 13000. CW (continuous wave) working condition was realized after a long time conditioning of the cavity. Beam tests were conducted with a current of 10 mA in pulse mode and CW mode, respectively, and it indicates that the transmission efficiency is 95.3%, output energy is 2.165 MeV, energy spread is 1.9%, and the transverse and longitudinal emittances are all 0.33 πmm·mrad. ©, 2015, Atomic Energy Press. All right reserved.