Ultrasonic tomography and critically refracted longitudinal (LCR) wave method is studied for inspecting the integrity and residual stress of plate. A transducer array based on sixteen elements is employed to imaging the corrosion defect for evaluating the size of defect quantitatively. The central frequency of element is chosen as 1MHz to excite low mode lamb wave. The algebraic reconstruction technique (ART) and simultaneous iterative reconstruction technique (SIRT) by attenuation of Lamb wave signal are used to get the projection data for tomographic reconstruction. The reconstructed image indicates that ultrasonic tomography is efficient to evaluate the integrity of plate. The residual stresses inspecting is based on the effect of stresses on the propagation velocity of elastic waves. The LCR wave mode was employed and accurate travel time data were measured for plate of steel. According to the results of experiments, the active LCR wave will effectively interact with the internal stress within a defined depth range and generate a measurable change on the travel time.
Superconducting undulators (SCUs) for advanced light sources are being developed rapidly to emit light with higher brightness and flux. The SCU consists of two superconducting magnets with a small gap, each with alternating poles. The SCU is invisible when operating in a Dewar or cryostat, so measuring the magnetic field in the narrow magnetic gap is a challenge in the development of the SCU. This paper presents a measurement system in vertical status for scanning the magnetic field of the SCU along the z-axis. The SCU is immersed vertically in 4.2 K liquid helium in a Dewar and the scanning is powered by a servo motor at room temperature. The measurement system overcomes the temperature difference of 300 K to drive the Hall probes to scan the magnetic field in the narrow magnetic gap of the SCU. In order to make the scanning area of the Hall probes coincide with the trajectory of the electron beam, a lot of detailed work on mechanical aspects has been done, such as controlling the positional accuracy of the Hall probes as they move, high precision machining and limiting the direction of movement. Unlike the currently reported magnetic field scans in the vertical status which are only available for SCU mock-ups of few periods, this system supports magnetic field measurements for SCUs up to 1.5 m long. The measurement system was validated on a 20-period SCU prototype, and after modification, the magnetic field of a liquid helium-cooled 30.5-period SCU was scanned. When the excitation current of the SCU with a magnetic gap of 7 mm is 450 A, the system measured a field distribution with a peak magnetic field of 1 T. The measurement system completed a full stroke trial run of 1750 mm before the 1.5 m SCU was machined. The results of magnetic field measurement from scanning in vertical status can be used as a reference for local shimming and correction of the magnetic poles of the SCU. This work establishes the SCU's ability to operate in cryostat horizontally.
To obtain high luminosity, compact high gradient quadrupole magnets QD0 and QF1 are required on both sides of the interaction points of the proposed Circular Electron Positron Collider (CEPC). QD0 is a double aperture superconducting quadrupole closest to the interaction point with a crossing angle between two aperture centerlines of 33 mrad. Magnetic field crosstalk between two apertures of QD0 is negligible using iron yoke, and the 3D coil end is optimized by ROXIE. In the design study, both NbTi conductor and HTS conductor are taken into account. The first step of the R&D is to design and manufacture a QD0 short model magnet with a magnetic length of 0.5 m. In this paper, the R&D status of QD0 short model magnet is described, and the design study of quadrupole magnet including NbTi technology and HTS Bi-2212 technology is presented.
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