A new laser-based monitoring method for the cryomodule components alignment

Abstract

Alignment of superconducting cavities is one of the important issues for the China Spallation Neutron Source Phase II (CSNS II) linac. In order to obtain the cavity displacement in the process of cooling down to the liquid helium temperature, a laser-based Poisson Spot Monitor (PSM) system was newly proposed and a verification system in the laboratory was built. The PSM system uses the diffraction spot formed on the CMOS camera after a beam of parallel laser passes through a spherical target to monitor the position of the measured object, where the spherical target is fixed on the monitored object. The displacement during the cooling process of the cryomodule is replaced by the movement of the high-precision two-axis motorized translation stage. A spherical target is fixed on the translation stage as the monitoring object. A beam of parallel laser passes through the spherical monitoring target to form a Poisson spot image on a CMOS camera. The coordinates of the Poisson spot center are obtained through image processing. Through experiments, the PSM system obtained a high accuracy within 5μm, which meets the displacement monitoring requirement of the CSNS II cryomodule components. The system is fairly simple and able to be constructed without highly specialized parts and can also be used in other high-precision alignment and monitoring fields.

The Arago–Poisson Spot: New Applications for an Old Concept

“…Since the spots are very tiny, they can be used in litography [62,63], to print sub-micrometer circuits. They could also be used in alignment [64][65][66][67], or to study aberrations [68]. Still considering the Arago-Poisson spot in optics, it has been used to measure velocities in fluids [69].…”

The design and application of magnetic landmark used for magnetic fiducialization of HEPS insertion devices*

“…Figure 4 illustrates the schematic diagram of the mechanical center fiducialization measurement process. This procedure establishes a mechanical center coordinate system, with the coordinate origin positioned on one end face of the MLK [18][19][20]. The Z-axis of this coordinate system coincides with the line connecting the geometric centers of the normal and skew quadrupole permanent magnet blocks, while the Y-axis is perpendicular and points upwards, forming a right-handed coordinate system along with the Xaxis.…”

High-precision and high-efficiency measurement method of accelerator tunnel control network based on total station angle observation

“…The accelerator is divided into three parts: linear, ring, and transport lines. The CSNS beamline has a total length of approximately 650 m: the length of the linear accelerator (LINAC) tunnel is about 197 m, the ring tunnel (RCS) has a circumference of about 230 m, the LRBT transport line tunnel connects the linear accelerator and the ring tunnel with a length of about 40 m, and the RTBT transport line tunnel connects the ring tunnel and the target station with a length of about 144 m [34,35]. The CSNS facility 0.000 0.000 0.000 coordinate system is defined as a three-dimensional horizontal coordinate system with the RCS symmetric center as the origin.…”