Using a pre-kicker to ensure safe extractions from the HEPS storage ring

The High Energy Photon Source (HEPS) is a 6 GeV diffraction-limited storage ring light source under construction. The swap-out injection is adopted with the depleted bunch recycled via high-energy accumulation in the booster. The extremely high beam energy density of the bunches with an ultra-low emittance (about 30 pm horizontally and 3 pm vertically) and high bunch charges (from 1.33 to 14.4 nC) extracted from the storage ring could cause hazardous damage to the extraction Lambertson magnet in case of extraction kicker failure. To this end, we proposed the use of a pre-kicker to spoil the bunches prior to extraction, significantly reducing the maximum beam energy density down to within a safe region while still maintaining highly efficient extractions. The main parameters of the pre-kicker are simulated and discussed.

DETERMINATION OF THE STRUCTURAL STATE AND STABILITY OF THE LASER CRYSTALLIZED Cd1-xМnxTe CRYSTAL SURFACE

The modified surface layers of the Cd1-xMnxTe crystals were obtained by the laser recrystallization of the crystal surface with the use of millisecond and nanosecond ruby ​​lasers. The determination and diagnostics of the layer structural state were performed by the study the electron channeling patterns in the SEM. The AFM studies showed that mechanically stable contact regions in the CdTe crystal – Cu film system can be formed, depending on the laser energy density and beam defocusing. On the base of the ellipsometric studies, it was found that while irradiating the Cd1-xMnxTe crystal surface, the refractive index of the oxide film on the modified surface changes depending on the laser beam energy density, which can be interpreted as the formation of the oxides of the different chemical composition.

High Chromium Steel Modification by the Intense Discrete Electron Beam: Structure and Properties

The Fe-Cr-C system thermodynamic analysis has been made. It has been demonstrated that the Fe-Cr alloys carbon alloy addition results in the significant structural-phase state change in them and exerts determinant influence on the M23С6, M7С3, M3С2and M3С carbides existence domain by the α-and γ-phases. The temperature field numerical calculations, forming in the steel superficial layer in the case of the electron beam irradiation, have been carried out. It has been demonstrated that the peak temperature, being achieved on the sample surface towards the end of the impulse effect, is below steel melting temperature at electrons beam energy density 10 J/cm2regardless of the electrons beam pulse duration (50-200 ms). The peak temperature on the irradiation surface is equal to the steel boiling temperature at electrons beam energy density (20-30) J/cm2and at pulse duration 50 μs. The peak temperature on the irradiation surface achieves and increases the steel melting temperature at pulse duration 200 μs. The AISI 321 and AISI 420 steel surface irradiation has been carried out by the intense pulse electron beam. The studies have been made and the nanostructured polyphaser superficial layers formation laws analysis have been done. It has been established that the steel electronic-beam treatment is accompanied by the М23С6((Cr, Fe,)23C6) composition initial carbide phase particles solution, by the carbon and chromium atoms superficial layer crystal lattice saturation, by the submicron sizes and dendritic crystallization cells formation, by the titanium carbide and chromium carbide nanosized particles abstraction. The mechanical and tribological tests of the AISI 321 and AISI 420 steel samples, irradiated by the intense pulse electron beam, have been done. It has been detected that the superficial layer hardness increases in 1.5 times and the superficial layer wear resistance increases in 1.5 times. The friction coefficient decreases in 1.6 times. The microhardness increases in 1.5 times. The wear resistance increases in 3.2 times. The friction coefficient reduces in 2.3 times

Laser modification of graphene oxide layers

The effect of linearly polarized laser irradiation with various energy densities was successfully used for reduction of graphene oxide (GO). The ion beam analytical methods (RBS, ERDA) were used to follow the elemental composition which is expected as the consequence of GO reduction. The chemical composition analysis was accompanied by structural study showing changed functionalities in the irradiated GO foils using spectroscopy techniques including XPS, FTIR and Raman spectroscopy. The AFM was employed to identify the surface morphology and electric properties evolution were subsequently studied using standard two point method measurement. The used analytical methods report on reduction of irradiated graphene oxide on the surface and the decrease of surface resistivity as a growing function of the laser beam energy density.

High-Current Pulsed Electron Treatment of Hypoeutectic Al–10Si Alloy

This paper reports, for the first time, an analysis of the effect of high-current pulsed electron beam (HCPEB) on a hypoeutectic Al–10Si alloy. The Al–10Si alloy was treated by HCPEB in order to see the potential of this fairly recent technique in modifying its wear resistance. For the beam energy density of 3 J/cm2 used in the present work, the melting mode was operative and led to the formation of a “wavy” surface and the absence of mass primary Si phase and eutectic microstructure. The surface nanocrystallization of primary and eutectic Si phases led to the increase in macro-hardness of the top surface layer, and the wear resistance was drastically improved with a factor of 4.

Different operation regimes of cylindrical triode-type electron accelerator studied by PIC code simulations

The performance of the converging electron beam generated in cylindrical triodes is systematically studied by particle-in-cell code simulations. Depending on the cathode and grid potentials applied, different operation regimes are identified. For low voltages between cathode and grid, laminar flow and homogeneous beam energy density at the target (anode) is obtained. This applies both to the case of unipolar electron flow and to bipolar flow with counter-streaming ions. Hereby, the electron emission current is enhanced by about 50% for bipolar flow compared with unipolar flow. A further increase by about 20% is obtained when electron backscattering at the target is enhanced due to a change of target material from aluminum to tungsten. For cathode-grid voltages exceeding a critical value, laminar flow is replaced by non-laminar flow regimes. For unipolar electron beams, a virtual cathode forms between grid and target, which leads to an inhomogeneous power density at the target. For the specific geometry investigated and the cathode potential fixed at −120 kV, the cathode-grid voltage threshold for the formation of the virtual cathode is ~32 kV for Al targets and ~28 kV for W targets. For bipolar flow, the laminar flow regime already ends at cathode-grid voltages of ~23 kV (Al target) and ~20 kV (W target), respectively, and is replaced by magnetic insulation at the beam edge. For increasing cathode-grid voltage, the magnetically insulated region extends until beam pinching occurs.

A new experimental setup for high-throughput controlled non-photochemical laser-induced nucleation: application to glycine crystallization

Non-photochemical laser-induced nucleation (NPLIN) has been a growing field of study since 1996, and more than 40 compounds including organics, inorganics and proteins have now been probed under various conditions (solvents, laser types, laser beamsetc.). The potential advantages of using this technique are significant, in particular polymorphic control. To realize these benefits, the objective is a carefully designed experimental setup and highly controlled parameters, for example temperature and energy density, in order to reduce the uncertainty regarding the origin of nucleation. In this paper, a new experimental setup designed to study NPLIN is reported. After a full technical description of the present setup, the different functionalities of this device will be illustrated through results on glycine. Glycine crystals obtained through NPLIN nucleate at the meniscus and exhibit different morphologies. The nucleation efficiency, as a function of the supersaturation of the solution used and the laser beam energy density, has also been established for a large number of samples, with all other parameters held constant.