Front end components must endure the harshest operating conditions of all the elements in a synchrotron beamline. At the same time, reliability is a key aspect of their design, with no tolerance for downtime due to the typically very limited access. The unique challenges presented by the front ends of the upcoming Sector 5 and 6 beamlines at CHESS are presented here together with the solutions adopted. The beamlines feature each two undulator sources. In one beamline, the undulators are installed in series for a power load of 12.4 kW over a 6x9 mm2 area, with a peak power density of 2270 W/mm2. In the other beamline, the undulators are canted to serve two independent branches, with a total radiated power of 14 kW. In addition to these high power loads, further challenges in the design of these front ends included severe space limitations for installation, due to the presence of existing infrastructure in the narrow underground accelerator tunnel; and intense ambient radiation from the 6 GeV storage ring during operation, especially in the beam plane, which affected the cooling and wiring routes as well as local shielding.

As part of the SLS 2.0 upgrade program, front-end systems have been extensively redesigned, refurbished, or constructed entirely anew to accommodate increased heat load, higher power density, and more compact device requirements$*$. Of the 18 front ends in scope, 12 have been installed and connected to the storage ring, most achieving first light at 400 mA and enabling initial user preparation; the remaining six are scheduled for installation in 2026 (Phase 2). Commissioning demonstrated flawless front-end performance, with beam delivery to the beamlines requiring minimal intervention. While design, procurement, manufacturing, and assembly adhered to schedule, ancillary systems such as cabling, vacuum, cooling, alignment, and PLC-based beamline control posed greater scheduling challenges due to complex inter-group coordination and shifting project priorities. The first-light results confirmed the efficacy of a fixed-mask plus movable-slit configuration, with newly developed slits reliably withstanding the increased thermal load.

The Advanced Photon Source (APS) upgrade from double-bend achromats (DBA) to multi-bend achro-mats (MBA) lattice is completed. All storage ring components and front ends were installed between April 2023 to April 2024 and fully commissioned. Some major changes have been made on front ends since our last front end design paper published in MEDSI2018 proceedings. The changes are: 1) Removed clearing magnet from all front ends, 2) Incorporated a Burn-Through-Mask (BTM) as the first fixed mask for all Insertion Device (ID) front ends, 3) Added a new-design diamond window to replace beryllium window for windowed High Heat Load Front End (HHLFE). The upgraded APS front ends will only have three types: a) HHLFE for single beam, b) Canted Front End (CFE) for canted beam, c) Bending Magnet Front End (BMFE) for bending magnet beam. This paper presents the as-built version of all three types of front ends.

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.

New frontends are required to upgrade the PETRA accelerator to the 4th generation. The design is based on the original design concept developed for the photon beamline frontends at PETRA III. The newly designed frontends aimed at using the same proven components and minimizing of the number of girder variations. In addition, a lot of the old components (complete girder) can be used for the new beamlines. A total of 36 new frontends are required for the PETRA IV project, which are divided into the types of 28 Frontends for single beamlines, 6 Frontends for 5 mrad canting and, 2 Frontends for 1.5 mrad canting. The frontends will be installed over four different experimental halls, so that the last part of the system has to be adapted accordingly. On the accelerator girder, the frontend is assembled as a complete string to minimize assembly times on the accelerator girder. Furthermore, the calibration of individual components prior to installation enables a substantial reduction in measurement and set-up times on the accelerator girder. A further benefit is that the entire assembly of the individual strings can be carried out in a cleanroom environment.

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.

A newly constructed infrared (CIRI) beamline at the SOLARIS National Synchrotron Radiation Centre features a front-end mirror positioning system capable of inserting the mirror directly into the storage ring vacuum chamber. The positioning mechanism utilizes a lead screw drive, which recently experienced a mechanical failure during operation. To enhance reliability and enable early fault detection, a vibration-based condition monitoring strategy is being implemented. The approach employs an industrial accelerometer mounted on the mirror assembly to measure vibration signals during insertion and extraction cycles. These signals are analysed to assess the operational condition of the lead screw and to identify early indicators of mechanical degradation, supporting predictive maintenance and reducing the risk of unexpected failures. The presentation will cover the concept, implementation, and results obtained from vibration-based monitoring, with particular emphasis on improving system reliability.