A four-row APPLE-Knot undulator is under developing in the High Energy Photon Source to get polarization adjustable synchrotron radiation and reduce on-axis heat load, because of the exotic magnetic field design, its construction faces challenges in mechanical design of frame, magnet blocks holder and integral field shimming method. In this paper, a mechanical design for APPLE-Knot undulator has been posed and structural deformation has been analysed, a test piece has been manufactured to test the physical design as well as magnetic holder design, integral field shimming method has also been described and realized, the result presents a good repeatability. It's a practical design of four-row APPLE-Knot undulator for the High Energy Photon Source.

a b s t r a c tThe estimation of unsaturated permeability coefficients (UPC) is of great importance on the properties of the matrix. Aim to study the relationship between the UPC and oxidation -reduction potential (ORP) in different matrix depths in the subsurface wastewater infiltration system (SWIS) and provide scientific basis for regulating SWIS and increasing pollutant removal, a test experiment of simulating the SWIS which included an inflow period (12 h) and a drying period (12 h) in one cycle was designed with a hydraulic load of 0.10 m 3 ·(m 2 ·d) -1 . Results investigated that ORP could increase with UPC increasing in 70 and 115 cm and decrease with the UPC increasing in 100 and 130 cm matrix depths. Phenomena indicated that capillary action could affect UPC and ORP obviously. Moreover, the existence of oxygen and low volumetric water contents could impose UPC and ORP. UPC in the 100 cm matrix depth below proved that anaerobic area could be found in aerobic environment under alternation conditions. UPC in different matrix depths of a satisfactory SWIS could change from 2.49 × 10 -7 to 1.16 × 10 -3 cm·s -1 . Treated water met reused requirements and no clogging was found.