Chloride channel blocker 4,4-diisothiocyanatostilbene-2,2'-disulfonic acid inhibits nitric oxide-induced apoptosis in cultured rat hippocampal neurons

Apoptosis in cultured rat hippocampal neurons was induced using the nitric oxide donor 3-morpholinosydnonimine, and cells were treated with the chloride channel blocker, 4,4- diisothiocyanatostilbene-2,2＇-disulfonic acid. Results showed that the survival rate of neurons was significantly increased after treatment with 4,4-diisothiocyanatostilbene-2,2＇-disulfonic acid, and the rate of apoptosis decreased. In addition, the expression of the apoptosis-related proteins poly（adenosine diphosphate-ribose）polymerase-1 and apoptosis-inducing factor were significantly reduced. Our experimental findings indicate that the chloride channel blocker 4,4- diisothiocyanatostilbene-2,2＇-disulfonic acid can antagonize apoptotic cell death of hippocampal neurons by inhibiting the expression of the apoptosis-related proteins poly（adenosine diphosphate-ribose）polymerase-1 and apoptosis-inducing factor.

Upgrade of the sextupole field for beam instability mitigation in rapid cycling synchrotron of China Spallation Neutron Source

Background The China Spallation Neutron Source incorporates a rapid cycling synchrotron(RCS)that operates by accumulating protons at 80 MeV and subsequently accelerating them to 1.6 GeV within a time span of 20 ms.The beam is guided to striking the tungsten target for neutron source.Purpose As a space charge dominated machine,the RCS is subject to space charge effects and momentum spread,hereby influencing the tune spread.To address this issue,sextupole magnets,powered by two families of DC power supply,were initially employed to decrease the absolute value of chromaticity and to control the tune spread.The head-tail instability has been observed during the RCS beam commissioning.Method The beam tests and simulations were conducted,revealing that tuning the chromaticity proved to be an effective mitigation strategy.However,to achieve better control over the tune spread and further suppress the instability,the DC sextupole field has been upgraded to an AC sextupole field,aiming to provide dynamic for controlling the chromaticity over an acceleration cycle.Results and conclusion Thanks to the upgraded of AC field,the instability has been fully mitigated with beam power of 100 kW and the transmission in the RCS has been improved by~2%from 96 to 98%.With help of AC sextupole at present,the beam power in the RCS is increased to 140 kW.

Simulation on buildup of electron cloud in a proton circular accelerator

Electron cloud interaction with high energy positive beams are believed responsible for various undesirable effects such as vacuum degradation, collective beam instability and even beam loss in high power proton circular accelerators. An important uncertainty in predicting electron cloud instability lies in the detailed processes of the generation and accumulation of the electron cloud. The simulation on the build-up of electron cloud is necessary to further studies on beam instability caused by electron clouds. The China Spallation Neutron Source （CSNS） is an intense proton accelerator facility now being built, whose accelerator complex includes two main parts： an H-linac and a rapid cycling synchrotron （RCS）. The RCS accumulates the 80 MeV proton beam and accelerates it to 1.6 GeV with a repetition rate of 25 Hz. During beam injection with lower energy, the emerging electron cloud may cause serious instability and beam loss on the vacuum pipe. A simulation code has been developed to simulate the build-up, distribution and density of electron cloud in CSNS/RCS.

Design and performance of the LLRF system for CSNS/RCS

The rapid cycling synchrotron （RCS） is part of the China Spallation Neutron Source （CSNS）. The RCS provides 1.6 GeV protons with a repetition rate of 25 Hz. The RF system in RCS is mainly composed of a ferrite loaded RF cavity, a high power tetrode amplifier, a bias supply of 3300 A and a digital low level RF （LLRF） system based on FPGA. The major challenge of the LLRF system is to solve problems caused by rapid frequency sweeping and the heavy beam loading effect. A total of eight control loops are applied to ensure the normal operation. An effective feedforward scheme is widely used to improve the dynamic performance of the system. The design of the LLRF system and high power integration test results with the prototype RF system are presented.

Design study for a 500 MeV proton synchrotron with CSNS linac as an injector

Using the China Spallation Neutron Source（CSNS） linac as the injector, a 500 MeV proton synchrotron is proposed for multidisciplinary applications, such as biology, material science and proton therapy. The synchrotron will deliver proton beam with energy from 80 MeV to 500 MeV. A compact lattice design has been worked out, and all the important beam dynamics issues have been investigated. The 80 MeV H-beam is stripped and injected into the synchrotron by using multi-turn injection. In order to continuously extraction the proton with small beam loss,an achromatic structure is proposed and a slow extraction method with RF knock-out is adopted and optimized.

Study of the beam loading effect in the CSNS/RCS

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.

Mechanical research and development of a monocrystalline silicon neutron beam window for CSNS

The monocrystalline silicon neutron beam window is one of the key components of a neutron spectrom- eter. Monocrystalline silicon is brittle and its strength is generally described by a Weibull distribution due to the material inhomogeneity. The window is designed not simply according to the mean strength but also according to the survival rate. The total stress of the window is stress-linearized into a combination of membrane stress and bending stress by finite element analysis. The window is a thin circular plate, so bending deformation is the main cause of failure and tensile deformation is secondary and negligible. Based on the Weibull distribution of bending strength of monocrystalline silicon, the optimized neutron beam window is designed to be 1.5 mm thick. Its survival rate is 0.9994 and its transmittance is 0.98447, which meets both physical and mechanical requirements.

Accurate calculation of field quality in conventional straight dipole magnets

Purpose In the standard design method of straight dipole magnets,the good field region is symmetric to the magnet mechanical center both in 2D and in 3D,so the obtained field quality is not the actual one because the field integration lines are not consistent with the curved beam paths.In this paper,an improved method for straight dipole magnets aiming at obtaining accurate field quality is proposed.Methods The field quality is calculated by taking into account the relationship of the good field region to the magnet straight geometry.General description of the improved method is introduced,and two application examples of straight dipole magnets are presented to investigate the detailed field quality difference between the improved and traditional methods.The result of the improved method is also compared with the field quality calculated along particle trajectory in OPERA-3D.Results It is shown that the difference in field quality between the improved and traditional methods cannot be neglected,and the field quality in the improved method is very close to the one calculated along real beam paths.Conclusion The field quality in the improved method is accurate enough for practical application in a straight dipole magnet.

Design and performance of Hall probe measurement system in CSNS

Background The construction of China Spallation Neutron Source(CSNS)was started in 2011 and will be completed in 2018.The phase I CSNS facility consists of an 80MeV HLinac,a 1.6GeV Proton Rapid Cycling Synchrotron(RCS),two beam transport lines and a target station.Magnets in the RCS and transport lines should be measured before being installed in the tunnel.Method In this paper,a new hall probe measurement system is described.The design and performance of the hall probe measurement system is presented.Conclusions The measurement results meet the design requirements.Some key issues were solved in the process.

Impedance measurements of the extraction kicker system for the rapid cycling synchrotron of China Spallation Neutron Source

The fast extraction kicker system is one of the most important accelerator components and the main source of impedance in the Rapid Cycling Synchrotron of the China Spallation Neutron Source. It is necessary to understand the kicker impedance before its installation into the tunnel. Conventional and improved wire methods are employed in the impedance measurement. The experimental results for the kicker impedance are explained by comparison with simulation using CST PARTICLE STUDIO. The simulation and measurement results confirm that the window-frame ferrite geometry and the end plate are the important structures causing coupling impedance. It is proved in the measurements that the mismatching from the power form network to the kicker leads to a serious oscillation sideband of the longitudinal and vertical impedance and the oscillation can be reduced by ferrite absorbing material.