Korea-4GSR, a 4th generation synchrotron radiation facility under construction in Ochang, South Korea, will install ten beamlines in Phase-1, nine of which will use undulators as light sources. The central cone entering each beamline’s optics has a beam size about 1/10 that of the full white beam, requiring precise shaping and diagnostics at the front-end. The white beam from IVU24(In-Vacuum Undulator) reaches up to 18 kW power with a peak power density of 165 kW/mrad². Such high thermal loads can cause damage or vacuum failure with slight misalignments. Therefore, diagnostics must endure this load and provide accurate measurements. The diagnostic system must offer sub-100 µm resolution to detect beam size and position, while also managing heat. For this, scCVD(single crystalline Chemical Vapor Deposition) diamond is used to detect current signals and X-ray fluorescence, supported by a low-conductive water cooling channel. This presentation introduces the white beam monitoring system for Korea-4GSR undulator beamlines, including mechanical design, cooling system, and thermal analysis.

The beamlines of 4GSR use an undulator as the light source and consist of a DCM (Double Crystal Monochromator), beam focusing devices, and slit devices. The Beam Defining Slit, installed after the DCM, processes an X-ray beam of several tens of micrometers with sub-micron precision. This device minimizes parasitic scattering and maximizes X-ray beam intensity at the sample location. Materials resistant to the heat load from the synchrotron light source were chosen. The slit edges are designed with a knife-edge shape, and the surface roughness is polished to several hundred nanometers or less, optimizing fuzziness. The device achieves geometric stability and sub-micron precision for more accurate beam processing. The schematic structure includes four slit blades, four blade transport mechanisms, a vacuum chamber, and support structures. Additionally, the design includes a BPM function by receiving electrical signals from the slit blades. This presentation will describe the configuration and mechanical design of the Beam Defining Slit for the 4GSR beamlines, along with the detailed structure of the devices for beam processing.

The Korea-4GSR, to be built in Ochang, South Korea by 2030, is a new 4th generation synchrotron radiation facility. It is designed with an electron beam energy of 4 GeV, a stored electron beam current of 400 mA, and an emittance of 62 pm.rad. In Phase I, 10 beamlines will be constructed, five of which will use the IVU24 undulator. When the undulator gap is set to 5 mm, the X-ray source has a total power of 17.95 kW and peak power density of 165 kW/mrad². The High Heat Load Front-End(HHLFE) system is designed to absorb up to 17kW of heat using a fixed mask and a movable mask, ensuring that only the central cone is transmitted to the beamline optical devices. The main materials are GlidCop or CuCrZr, selected for their high thermal conductivity, and the cooling channels are designed with a rectangular cross-section to maximize the heat exchange area for efficient thermal management. In addition, tungsten is applied to precisely shape and effectively absorb the X-ray beam. The structural design of the heat-absorbing devices was determined based on thermal analysis results$*$. This presentation introduces the structural and mechanical design details of the HHLFE.

Currently under construction in Ochang, Chungcheongbuk-do, Korea-4GSR is a 4GeV, 4th Generation Synchrotron Light Source. The front end is being designed to pass the powerful synchrotron radiation generated by the insertion device. High heat load components have hence been customized to meet the requirements of beamline users and account for the thermomechanical limits of materials. In the analysis of the 4GSR beamline device, the values of IVU24, which has the largest beam intensity, were used, and the specifications for securing the safety of the front end device were determined. In the case of devices that come into direct contact with the beam, the flow rate and cooling passage structure were determined so that the convection coefficient could be increased under conditions that did not cause significant vibration. And cooling system optimization analysis was conducted to minimize the slope error of the mirror, and as a result, partial cooling according to the footprint size resulted in the best slope error value. In this paper, we describe the characteristics and analysis results of the front end and mirror.