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Using strong electromagnetic fields generated by lasers to interact with electrons for precise diagnosis and manipulation of electron beams represents a recent focal point in accelerator technology. This approach surpasses the limitations of conventional RF technology, such as low electric field gradients and timing jitters, effectively enhancing the accuracy of ultrafast electron beam diagnostics and manipulations. As demands for precision continue to rise, the precise diagnosis of crucial parameters of ultrafast electron beams remains challenging. This study delves into the electromagnetic behavior of THz-driven devices and proposes an all-optical method utilizing single-cycle THz radiation to compress and characterize a 3 MeV electron beam. Particle tracking simulations demonstrate an astonishing compression effect, reducing the bunch length from 54.0 fs to 4.3 fs, and achieving sub-femtosecond bunch length measurement resolution. Moreover, when combined with an orthogonal THz streak camera, this method shows even greater potential in multi-bunch scenarios.

Microbunching instability (MBI) has been one of the most challenging issues in designs of high-brightness beam transport lines for single-pass or recirculating accelerators. Although the intrabeam scattering (IBS) has long been studied in lepton or hadron storage rings as a slow diffusion process or in high-intensity proton linear accelerators as one mechanism for the beam halo, the effects of IBS on single-pass or recirculating electron accelerators have drawn attention only in the recent two decades due to emergence of linac-based or energy-recovery-linac-based fourth-generation light sources, which require high-quality electron beams during the beam transport. In this paper we develop a theoretical formulation of microbunching instability in the presence of IBS for single-pass or recirculation accelerators. To quantify MBI with inclusion of IBS, we start from the Vlasov-Fokker-Planck (VFP) equation, combining both collective interactions and incoherent IBS effects. The linearized VFP equation and the corresponding friction and diffusion coefficients are derived. The evolutions of the resultant density and energy modulations are formulated as a set of coupled integral equations. The theoretical formulation is then applied to a recirculating beamline design. The results from the semianalytical calculation are compared and show good agreement with massive particle tracking simulations.

Huazhong University of Science and Technology (HUST) has built a compact linac-based terahertz free electron laser (THz-FEL) prototype. In order to achieve compact structure, the linac uses collinear load cells instead of conventional output coupler to absorb remanent power at the end of linac. The new designed structure is confronted with rf breakdown problem after a long time conditioning process, so we tried to figure out the breakdown site in the linac. Without transmitted signal, we propose two methods to analyze the breakdown site mainly based on the forward and the reflected power signals. One method focuses on the time relationship of the two signals while the other focuses on the amplitude. Both the two methods indicate the breakdown events happened at the end of the linac and more likely in the first or the second load cell.

A proton therapy facility with two 360° gantry treatment rooms and one fixed beamline is under development in the Huazhong University of Science and Technology, which is based on the isochronous superconducting cyclotron scheme. This paper presents the beam optics and main magnetic elements including dipoles, quadrupoles, and fast scanning magnets of the gantry beamline. In addition, the energy selection system will be introduced, which enables fast energy modulation of proton beam between 70 and 240 MeV. [ABSTRACT FROM AUTHOR]

To enhance the dye fixation of pad-steam dyeing with reactive dyes, we used five kinds of dyes and water–ethanol dyeing medium to investigate the hydrophobic effect in dyeing process. The results indicated that the higher the molecule weight per water soluble group, i.e. the stronger dye hydrophobicity, the higher the dye fixation rate. When dyed with hydrophobic dye, both the alkali and steaming time can be reduced to realize the saving of chemicals and energy. For the more hydrophobic C.I. Reactive Orange 16 (RO16), the appropriate sodium carbonate concentration is 20 g/L, which is 10 g/L lower than the 30 g/L of C.I. Reactive Violet 5 (RV5). Similarly, RO16 just needed 2 min of steaming time to obtain the maximum K/S value, while RV5 needed 3 min. Enhancing the hydrophobicity of dyeing medium can also increase the dye fixation rates and K/S values. The K/S values and fixation rates of fabrics dyed with RV5 increased up mostly by 31.2% and 14% via using ethanol instead of 32 vol.% water in dyeing medium, respectively. All the dyed fabrics exhibit good color fastness.

With the ever-growing concern about environmental conservation, green production and water-based nanofibers have attracted more and more interest from both academic and industrial fields; nevertheless, the stabilization process of water-based nanofibers is primarily relying on the application of organic solvent-based crosslinking agents. In this work, we develop a green approach to fabricate water-resistant polyvinyl alcohol (PVA) nanofibers by using a water-based epoxy compound, N1, N6-bis(oxiran-2-ylmethyl) hexane-1,6-diamine (EH), as the crosslinker. This EH/sodium carbonate/sodium bicarbonate (CBS) solution system can break down large aggregates of PVA molecules into small ones and promote the uniform distribution of EH in the solution, resulting in the improved stability of crosslinked PVA nanofibers. We firstly report that the uniform dispersion of crosslinking agents in the electrospinning solution plays a vital role in improving the stability of spinning solutions and the water resistance of crosslinked PVA nanofibers by comparing crosslinking performances between water-based epoxy and conventional water-based blocked isocyanate (BI). This work could open up a novel strategy and green approach for the stabilization of water-based nanofibers.

The magnetic septa have been developed for the slow beam extraction from the 50 GeV Proton Synchrotron to the Hadron Experimental Hall at J-PARC (Japan Proton Accelerator Research Complex). The magnetic septa consist of two thin magnetic septa, four medium thick magnetic septa and four thick magnetic septa. The typical operating current is 3000 A and the total kick angle is 77 mrad with the 30 GeV proton beam. All parts of the thin and of the medium thick septum magnets are made of inorganic materials to resist high radiation environment. The positions of the thin and medium thick septa can be aligned remotely in the horizontal range of ±5 mm, which enables us to minimize the beam loss at the magnetic septum section. The septa were installed in the synchrotron ring in December, 2008, after a test at KEK (High Energy Accelerator Research Organization), and were successfully operated in the beam time for the slow beam extraction in January and February, 2009, which resulted in the first 30 GeV slow extracted beam delivery to the Hadron Experimental Hall. [ABSTRACT FROM AUTHOR]

Digital inkjet printing has been widely used in textile industry. The quality of dye solutions and ink-jet droplets limits the ink-jet printing performance, which is very important for obtaining high-quality ink-jet printing images on fabrics. In this paper, we introduced diethylene glycol (DEG) into the dye solutions of Reactive Blue 49 and Reactive Orange 13, respectively, and investigated the interaction between dye chromophores and DEG molecules. Results indicated that the dye chromophores were featured in the aggregation. Adding DEG into the dye solution could effectively disaggregate clusters of reactive dyes, and eliminate satellite ink droplets, thus improving the resolution of the ink-jet printing image on fabrics. Under the same DEG concentration, the disaggregation effect was more obvious in Orange 13 than in Reactive Blue 49. Higher DEG concentration was required in Reactive Orange 13 solution for creating complete and stable ink drops. The surface tension and viscosity of the dye solutions were measured, and printing performance on cotton fabrics was evaluated. The interaction mechanism between dye chromophores and DEG molecules was also investigated. Results from this work are useful for high-quality ink-jet printing images on fabrics.

The aggregation structure of dye molecules has a great influence on the properties of dye solutions, especially in high concentration. Here, the dye molecular aggregation structures were investigated systemically in aqueous solutions with high concentration using three reactive dyes (O-13, R-24:1 and R-218). O-13 showed stronger aggregation than R-24:1 and R-218. This is because of the small non-conjugate side chain and its β-linked position on the naphthalene of O-13. Compared with R-218, R-24:1 showed relatively weaker aggregation due to the good solution of R-24:1. The change of different aggregate distributions in the solutions were also investigated by splitting the absorption curves. Moreover, it is found that the surface tension of solutions can be modified by the combined effect of both aggregation and the position of the hydrophilic group, which, however, also have an effect on viscosity. This exploration will provide guidance for the study of high concentration solutions.