Study on the selection of BLM detector for C-ADS Injector Ⅱ

The injector of C-ADS (Chinese Accelerator Driven Sub-critical System) project is a high current, fully super-conducting proton accelerator. Meanwhile, a BLM system is indispensable for this facility, especially in low energy segments. This paper presents some basic simulations for 10 MeV proton by Monte Carlo program FLUKA, as well as the distributions on different secondary particles in three aspects: angular, energy spectrum, and current. These results are beneficial to selecting the detector type and its location and determining its dynamic range matching different requirements for both fast and slow beam loss. Furthermore, in this paper the major impact of the background is also analyzed, such as superconducting cavity X radiation and radiation caused by material activation. This work is meaningful in BLM system research.     

Study on the selection of BLM detector for C-ADS Injector Ⅱ

The injector of C-ADS (Chinese Accelerator Driven Sub-critical System) project is a high current, fully super-conducting proton accelerator. Meanwhile, a BLM system is indispensable for this facility, especially in low energy segments. This paper presents some basic simulations for 10 MeV proton by Monte Carlo program FLUKA, as well as the distributions on different secondary particles in three aspects: angular, energy spectrum, and current. These results are beneficial to selecting the detector type and its location and determining its dynamic range matching different requirements for both fast and slow beam loss. Furthermore, in this paper the major impact of the background is also analyzed, such as superconducting cavity X radiation and radiation caused by material activation. This work is meaningful in BLM system research.     

Multi-physics analysis of the RFQ for Injector Scheme Ⅱ of C-ADS driver linac

A 162.5 MHz, 2.1 MeV radio frequency quadruples (RFQ) structure is being designed for the Injector Scheme Ⅱ of the China Accelerator Driven Sub-critical System (C-ADS) linac. The RFQ will operate in continuous wave (CW) mode as required. For the CW normal conducting machine, the heat management will be one of the most important issues, since the temperature fluctuation may cause cavity deformation and lead to the resonant frequency shift. Therefore a detailed multi-physics analysis is necessary to ensure that the cavity can stably work at the required power level. The multi-physics analysis process includes RF electromagnetic analysis, thermal analysis, mechanical analysis, and this process will be iterated for several cycles until a satisfactory solution can be found. As one of the widely accepted measures, the cooling water system is used for frequency fine tunning, so the tunning capability of the cooling water system is also studied under different conditions. The results indicate that with the cooling water system, both the temperature rise and the frequency shift can be controlled at an acceptable level.     

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.     

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

The InjectorⅡ, 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.     

Progress of the Injector Linac Upgrade for the BEPCⅡ Project

BEPCⅡ—an upgrade project of Beijing Electron Positron Collider (BEPC) is a factory type of e+e- collider. It requires its injector linac to have a higher beam energy (1.89 GeV) for on-energy injection and a higher beam current (40 mA e+ beam) for a higher injection rate ( 50 mA/min). The low beam emittance (1.6π mm·mrad for e+ beam, and 0.2πmm·mrad for 300 mA e- beam) and the low beam energy spread (±0.5%) are also required to meet the storage ring acceptance. Thus the original BEPC injector linac must be upgraded to have a new electron gun with its complete tuning system, a new positron source with a flux concentrator, a new RF power system with its phasing loops and a new beam tuning system with orbit correction and optics tuning devices. These new components have been designed, fabricated, tested and will be installed in their final positions in this spring and summer, which are described in this paper.     

Simulation of BEPCⅡ′s BPM

Considering the effect of photoelectron, BEPCⅡ′s beam position monitor (BPM) uses antechamber structure. The cut-off frequency of TE mode is maybe lower than the BPM signal processing frequency 500MHz. The power of TE mode will result in beam position measurement error. With monitoring the antechamber's TE mode power amplitude and calculating the transmission of TE mode power to BPM's electrodes, we can calculate the error of position measurement caused by TE mode. We found that the error is beyond the acceptance when the cut-off frequency of TE₁₀ mode is lower than 500MHz. By changing the slot length, the cut-off frequency is higher than 500MHz and the error could be accepted. At last the effect of the wakefield to the beam has been simulated and the longitudinal impedance of wakefield has been calculated.     

Working principles of the energy measurement system at BEPCⅡ

The proposed beam energy measurement system at BEPCⅡ is composed     

Measurement of radiation dose at the north interaction point of BEPCⅡ

The technique details for measuring radiation dose are expounded.The results of gamma and neutron radiation levels are presented and the corresponding radiation shielding is discussed based on the simplified estimation.In addition, the photon radiation level move as background for future experiments is measured by a NaI(T1) detector.     

Study of the p and p Identification at BES Ⅱ

Based on three methods of particle identification (PID) of BES,we study the identification of p and p in momentum range from 0.3 to 1.2 GeV using real particle samples of e,μ,π,K,p and p which were collected in 2-5GeV R scan,J/(ψ) and ψ′ data taking periods. The paper presents the optimized method of PID:p(p) is identified by dE/dx only if momentum below 0.6GeV,and by TOF or the combination of dE/dx and TOF for higher momentum.The PID efficiency of p, p and contamination from the other charged particles are also given.     

Measurement of radiation dose at the north interaction point of BEPCⅡ

The technique details for measuring radiation dose are expounded. The results of gamma and neutron radiation levels are presented and the corresponding radiation shielding is discussed based on the simplified estimation. In addition, the photon radiation level move as background for future experiments is measured by a NaI（T1） detector.     

BEPCⅡ BPM模拟研究

基于减少光电子的要求,BEPCⅡ真空管道采用antechamber结构,TE模截止频率可能低于BPM信号处理频率500MHz.本文主要模拟研究TE10模对位置测量的影响,发现TE10模截止频率低于500MHz时,将带来束流位置测量误差10.1μm;改变狭缝长度,在TE10模截止频率高于500MHz时,测量误差将在可以接受的范围内.同时,模拟研究了BPM尾场对束流的影响,计算了相应尾场阻抗     

Study of radiation background at the north crossing point of the BEPCⅡ in collision mode

Understanding the radiation background at the north crossing point (NCP) in the tunnel of BEPCII is crucial for the performance safety of the High Purity Germanium (HPGe) detector, and in turn of great significance for long-term stable running of the energy measurement system. Therefore, as the first step, a NaI(Tl) detector is constructed to continuously measure the radiation level of photons as background for future experiments. Furthermore, gamma and neutron dosimeters are utilized to explore the radiation distribution in the vicinity of the NCP where the HPGe detector will be located. Synthesizing all obtained information, the shielding for neutron irradiation is studied based on model-dependent theoretical analysis.     

Studies of dual-harmonic acceleration at CSNS-Ⅱ

The Rapid Cycling Synchrotron(RCS) of the China Spallation Neutron Source(CSNS) complex is designed to provide 1.56×1013 protons per pulse(ppp) during the initial stage,and it is upgradeable to 3.12×1013 ppp during the second stage and 6.24×1013 ppp during the ultimate stage.The high beam intensity in the RCS requires alleviation of space charge effects to reduce beam losses,which is key in such high beam power accelerators.With higher intensities in the upgrading phases,a dual-harmonic RF system is planned to produce flat-topped bunches that are useful to reduce the space charge effects.We have studied different schemes to apply the dual-harmonic acceleration in CSNS-,and have calculated the main parameters of the RF systems,which are presented in this paper.     

Frequency tuning with RFQ temperature in China ADS Injector Ⅱ

A 162.5 MHz four-vane radio frequency quadruple(RFQ) accelerator has been developed at the Institute of Modern Physics(IMP) for Injector II of the China ADS linac. The RFQ will operate in continuous wave mode at 100 k W. For the designed 10 mA beam, the additional RF power dissipation will induce a very large reflection of power. A water-temperature controlling system will be used to reduce the power reflection by tuning the frequency of the RFQ. The tuning capability of the water temperature is studied under different configurations of cooling water.Simulations and experiment are compared in this paper. The experimental results agree well with simulation using ANSYS. This can be used as a reference to tune the RFQ in beam commissioning.     

Preliminary study of EEHG-based superradiant undulator radiation at the HLS-Ⅱ storage ring

We investigate storage ring-based Echo-Enabled Harmonic Generation(EEHG) superradiant undulator radiation as a possible scheme to obtain shorter wavelengths at the HLS-Ⅱ(Hefei Light Source-Ⅱ) storage ring. In this paper we give the designation of the storage ring based EEHG up to the 26 th harmonic, where 31 nm vacuum ultraviolet light is radiated from an 800 nm seeded laser. The novelty of our design is that both the two dispersion sections of EEHG are realized by the storage ring's own magnet structure. In particular, the whole ring is used as the first dispersion section, and two modulators of the traditional EEHG can be done with the same undulator. These two dispersion sections are realized by changing the superperiod of the present lattice structure, and more precisely by changing the focusing strengths of the present structure. Since no additional magnets and chicanes are used,the beam circulates around the storage ring repeatedly, and thus this storage ring-based EEHG can have a higher repetition rate than a linac-based EEHG.     

Monte Carlo Study of the Neutron Detection Wall at RIBLLⅡ in HIRFL-CSR

With the construction of the new Radioactive Ion Beam Line in Lanzhou (RIBLLⅡ) which connects the CSRm and the CSRe, an experimental setup for physics research is highly required. A large area neutron detection wall is the main part of the setup. This paper introduced the detection principle of the neutron detection wall and the Monte-Carlo simulation of its design under the environment of the Geant4 toolkit. We presented the final design with the optimized parameters and the performance of the wall.     

Determination of the angles of the unitarity triangle at BABAR⋆

We report recent measurements of the three angles of the unitarity triangle using the data collected with the BABAR detector at the PEP-II asymmetric energy e ⁺ e ^- collider. Original article based on material presented at HADRON 2007.     

Study of Neutral Track Measurement at BESⅡ

The measurement errors of the deposited energy and position of neutral tracks in Barrel Shower Counter (BSC) of BESⅡ are investigated. The errors of energy and position of real data are determined by radiative Bhabha events, while the errors of Monte Carlo Data are determined by e⁺e^－→γγ events. Then the corrections are tested by the selected ρπ sample, which shows better pull and Confidence Level distribution after the correction. The results are already applied to the kinematic fitting, which can improve the physics results at BESⅡ.     

On the Correlation of the Components of the Earth’s Electric Field at Spatially Separated Stations at the Harmonics of the Frequencies of Rotation of Relativistic Double Star Systems

Russian Physics Journal - Using spectro-eigenoscopy of multiyear series of observations of the vertical component of the electric field strength in the surface layer of the atmosphere, we have...