Obtaining the complete distribution of a beam in high-dimensional phase space is crucial for predicting and controlling beam evolution. Based on the theory of maximum entropy tomography, we developed an algorithm for reconstructing the four-dimensional (4D) transverse phase space distribution. Our algorithm can take any number of 2D linear projections as constraints, and iteratively converges to the unique numerical solution which is the maximum-entropy distribution satisfying the constraints. Having verified the algorithm with simulation experiments, we plan to use it to conduct 4D phase space tomography in the MEBT and HEBT of the heavy ion linac CAFe II.

The China Initiative Accelerator Driven System (CiADS), a multi-purpose facility driven by a 500 MeV superconducting RF linac, is currently under construction in Huizhou, Guangdong. In order to ensure the stable operation of the superconducting linac, we conducted optimization research on the beam quality in the front-end section of CiADS. By using the point scraping method, part of the beam halo particles are removed in advance at the entrance of the LEBT, avoiding the generation of beam halo particles. On the other hand, since the beam extracted from the ECRIS contains a portion of $H^{2+}$ and $H^{3+}$particles, impurity particles may lead to a decrease in the transmission efficiency of downstream accelerators. By separating the mixed beam, it is possible to measure the proportion and phase space distribution of the mixed beam at the exit of the ion source, thereby achieving accurate measurement of the proton beam. This paper mainly outlines the first beam commissioning of CiADS Front end. Additionally, the effectiveness of the point scraping method has been verified through transverse emittance measurement, and the proportion and phase space distribution of the mixed beam was measured. Furthermore, the stability of the ion source was tested, and the centroid shift of the ion source extracted beam was measured.

The 81.25 MHz quarter-wave resonator (QWR) and 162.5 MHz half-wave resonator (HWR) are selected as the main accelerating cavities for the superconducting ion linac of the High Intensity heavy-ion Accelerator Facility (HIAF) at the Institute of Modern Physics (IMP). Six QWR007 (βopt = 0.07) cavities and eight HWR015 (βopt = 0.15) cavities have been fabricated before the mass production to verify the design and production quality control. Two cavities of the both types have been random chosen to surface processing and vertical testing for performance validating before welding helium vessel. In this paper, the development of SRF cavity for HIAF will be addressed, which including the fabrication, surface processing and vertical testing results. The achieved gradients for both cavities have exceeded 60%~100% of requiring operation gradients. The Q0 of both types cavities have met the 2 K operation requirement too. These results inspired to push the cavity production for the HIAF project forward to the mass production stage.

Quantifying the difference between two beam distributions in high-dimensional phase space is crucial for interpreting experimental or simulation results. This study aims to analyze and compare several common statistical divergences that quantify the differences in high-dimensional distributions, and to determine which of them are suitable for beam physics applications. We tested these divergences with common kinds of initial distributions by computing how the difference values vary when the mismatch factor and emittance change, between the same and different kinds of distributions. These results, along with similar comparisons after extended beam transport, provided guidance on the use and choice of statistical divergences for beam phase space distributions.

The demonstration of a 100 mA, 4.6 MeV superconducting radio frequency linear electron accelerator, based on conduction cooling and developed by the Institute of Modern Physics (IMP), aims to validate the feasibility of stable beam commissioning in a liquid helium-free 5-cell-$\beta$opt=0.82 Nb3Sn elliptical cavity, and to offer guidance for subsequent industrial applications. The beam energy characteristics, considered one of the critical parameters, need to be precisely measured. Given the high beam energy and the need for a compact, straightforward accelerator layout, we achieved high-precision measurements using only a ordinary dipole, a slit, and a Faraday Cup (FC). This paper presents the online measurement results of beam energy at different cavity voltage and provides a thorough analysis and optimization of the various errors encountered during measurement.