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Zou Y.,Anhui University of Science and Technology | Zou Y.,CAS Institute of High Energy Physics | Tang J.,Anhui University of Science and Technology | Tang J.,CAS Institute of High Energy Physics | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2016

This paper proposes a novel method for resonant slow extraction in synchrotrons by using special anti-symmetric sextupole fields, which can be produced by a special magnet structure. The method has potential in applications demanding very stable slow extraction from synchrotrons. Our studies show that slow extraction at the half-integer resonance by using an anti-symmetric sextupole field has some advantages compared to the standard sextupole field, which is widely used in the slow extraction method. One advantage is that it can work at a more distant tune from the resonance, so that it can reduce significantly the intensity variation of the extracted beam which is mainly caused by the ripples of magnet power supplies. Studies by both the Hamiltonian theory and numerical simulations show that the stable region near the half-integer resonance by anti-symmetric sextupole field is much smaller and flatter than the one by standard sextupole field at the third-order resonance. The particles outside the region will be driven out in two possible directions in quite a short transit time but with spiral steps similar to the third-order resonant extraction. By gradually increasing the field strength, the beam can be extracted with intensity more homogeneous than by the usual third-order resonant method, because of both smaller intensity variation and spike in the beginning spill. With the same field strength and tune distance to the resonance, the change in the stable region area due to the working point variation in the case of the anti-symmetric sextupole is about 1/14 of the one for the standard sextupole. Detailed studies including beam dynamic behaviors near other resonances, expression of the field in polynomial expansion, influence of 2-D field error, half-integer stop-band, and resonant slow extraction using a quadrupole field are also presented. © 2016 Elsevier B.V. All rights reserved.

Jia D.,CAS Institute of Chemistry | Yang J.-F.,CAS Institute of Chemistry | Cheng H.,CAS Institute of High Energy Physics | Cheng H.,Dongguan Institute of Neutron Science | Han C.C.,CAS Institute of Chemistry
Acta Polymerica Sinica | Year: 2015

As a typical elastic scattering technique, laser light scattering results cannot precisely describe the solution structure when the samples absorb incident light. Therefore, commercial laser light scattering instrument has been modified and upgraded to utilize four independent lasers, e. g. 785 nm, 632.8 nm, 532 nm and 457 nm, respectively as the light sources. By switching the wavelengths of incident lasers to avoid the sample absorption, the instrument can be widely used in fluorescent/phosphorescence solution systems. Spherical polystyrene nanoparticles with and without fluorescent dyes are used to calibrate the modified instrument. It is found that the height of the normalized intensity-intensity time correlation function decreases with the increase of the scattering angle when the sample absorbs the incident laser light. Such a correlation function fails to describe the sample solution structure, because the corresponding hydrodynamic radius distribution shows two modes and the average characteristic line width 'Γ' versus the square of scattering vector q2 does not fit a good linear relationship any more. Therefore, another laser which is not absorbed by the sample is used to do the calibration again. The corresponding intensity-intensity time correlation functions and the fitting results can precisely describe the solution structure. Fluorescence correlation spectroscopy (FCS) is also conducted to further prove the results obtained from the modified laser light scattering instrument are precise and accurate. © 2015, Science Press. All rights reserved.

Huang M.-Y.,CAS Institute of High Energy Physics | Huang M.-Y.,Dongguan Institute of Neutron Science
Chinese Physics C | Year: 2016

We study the detection of accelerator neutrinos produced at the China Spallation Neutron Source (CSNS). Using the code FLUKA, we have simulated the production of neutrinos in a proton beam on a tungsten target and obtained the yield efficiency, numerical flux, and average energy of different flavors of neutrinos. Furthermore, detection of these accelerator neutrinos is investigated in two reaction channels: neutrino-electron reactions and neutrino-carbon reactions. The expected numbers of different flavors of neutrinos have also been calculated.

Huang L.-S.,CAS Institute of High Energy Physics | Huang L.-S.,Dongguan Institute of Neutron Science | Yoshiro I.,High Energy Accelerator Research Organization | Liu Y.-D.,CAS Institute of High Energy Physics | And 3 more authors.
Chinese Physics C | Year: 2015

Both longitudinal and transverse coupling impedance for some critical components need to be measured for accelerator design. The twin wires method is widely used to measure longitudinal and transverse impedance on the bench. A mode error is induced when the twin wires method is used with a two-port network analyzer. Here, the mode error is analyzed theoretically and an example analysis is given. Moreover, the mode error in the measurement is a few percent when a hybrid with no less than 25 dB isolation and a splitter with no less than 20 dB magnitude error are used. © 2015 Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

Yuan Y.-S.,CAS Institute of High Energy Physics | Yuan Y.-S.,Dongguan Institute of Neutron Science | Li K.-W.,CAS Institute of High Energy Physics | Li K.-W.,Dongguan Institute of Neutron Science | And 4 more authors.
Chinese Physics C | Year: 2015

The China Spallation Neutron Source/Rapid Cycling Synchrotron (CSNS/RCS) accelerates a high-intensity proton beam from 80 MeV to 1.6 GeV. Since the beam current and beam power is high, the beam loading is a severe problem for the stability of the circulating beam in the RCS. To study the beam loading effect in the CSNS/RCS theoretically, the RLC circuit model of the rf cavity, the method of Fast Fourier Transform and the method of Laplace transform have been employed to obtain the impedance of the rf system, the beam spectrum and the beam-induced voltage, respectively. Based on these physical models, the beam dynamics equations have been revised and a beam loading model has been constructed in the simulation code ORIENT. By using the code, the beam loading effect on the rf system of the CSNS/RCS has been investigated. Some simulation results have been obtained and conclusions have been drawn. © 2015 Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

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