The China Spallation Neutron Source (CSNS) facility began operation in 2018. By 2020, its accelerator achieved the design power of 100kW and currently operates at a power of 160kW. This year, the power upgrade project (CSNS-Ⅱ) has been launched to meet the growing scientific demands. Our goal is to enhance the accelerator power to 500kW primarily by increasing the beam current. A comprehensive suite of beam diagnostics has been developed to support commissioning and operation of the accelerator at higher intensities. In this paper, we first review the commissioning and operational status of the existing linac, and then outline the new requirements for the linac upgrade.

The CSNS accelerator complex is upgrading the injection area to improve the beam-loss control during beam injection and acceleration in the Rapid Cycling Synchrotron. At CSNS, the linac beam energy will be increased from 80MeV to 300MeV employing a new superconducting accelerating section, and the beam power at the spallation target will be 500kW. To accomplish these requirements, a stripline-type BPM has been designed with a large aperture and 50 Ω stripline electrodes. This BPM has an inner diameter of 52 mm and is used to detect the beam with a current of 10-30 mA and a pulse width of 100-500us. Several geometrical and electrical parameters have been optimized with numerical simulation. This paper will describe the design and optimization of the stripline-type BPM in detail, and simulation results are discussed.

As part of the CSNS-II upgrade, the H- LINAC beam energy will be increased from 80 MeV to 300 MeV using superconducting cavities. To accurately measure beam position, phase, and energy, stripline-type Beam Position Monitors (BPM) are essential. The shorted-type stripline BPM was chosen for this upgrade due to its excellent S/N ratio and rigid structure. As space is limited in the LINAC's SC section, the BPMs must be embedded in the quadrupole magnet. Two prototypes, with inner diameters of 50 mm and 96 mm, were designed using numerical simulation codes and manufactured for beam testing. This paper will detail the simulation, design, and beam test results of the prototype BPMs for CSNS-II.

To enhance the performance of the next generation of X-ray free electron lasers (XFEL), it is essential to produce a high quality electron beam with a low emittance, for instance, below 0.2 mm-mrad for a 100 pC bunch charge. In order to demonstrate the fundamental techniques required for future FEL facilities, a C-band photoinjector test facility has been constructed aligning with the Southern Advanced Photon Source (SAPS) pre-research project. An emittancemeter based on the consecutive double-slit-scan concept has been proposed and designed for determining such small emittance. This paper presents the further optimization of the primary parameters of this emittancemeter employing numerical simulations in the presence of the measured motion accuracy and the expected observation resolution.

Non-invasive and turn-by-turn beam transverse profile monitoring is essential for the tunning and operating CSNS 1.6 GeV Rapid Cyclic Synchrotron. A residual gas Ionization Profile Monitor (IPM) was designed and installed in RCS for horizontal beam profile measurement. However, several challenges related to electromagnetic interference (EMI), vacuum, and MCP operation in the IPM were identified. The EMI is induced by the beam itself and further accelerator components. An improved Faraday cage was implemented to counteract the EMI issues. In order to achieve the desired MCP gain, a suitable pull-down resistor was incorporated into the MCP power supply circuit. After these improvements, the IPM was commissioned successfully. This paper will describe the challenges of IPM and early beam commissioning results.