0428同步年報-2021-全

Facility Status 099 CU15 can have a maximum 3 times higher than that using the IU22 at 20 keV. From a user’s experiences, the experimental time can efficiently be decreased to one third on replacing IU22 with CU15. NdFeB-based CPMU (CUT18) CUT18, which is the second CPMU at the TPS and has a period length of 18 mm, was developed using LN 2 tank cooling and the newest grade of NdFeB (NMX-U52SH) magnets. Several key factors were considered in the design of CUT18: (1) The temperature control system of magnets is well-developed, so a NdFeB magnet-based CPMU can be controlled at a temperature of 160–170 K to maximize the magnetic field. (2) The annual operational costs (including maintenance costs) of CPMUs with LN 2 tank cooling are one-fifth, compared to those of CPMUs with cryocoolers. (3) The magnetic performances from the newest grade of Tb- diffused NdFeB magnets may be comparable to PrFeB magnets. However, the research and development of new grades of NdFeB PMs are intensive due to high market demand; therefore, the potential of NdFeB-based CPMUs is expected to increase in the future. (4) As the required temperature of magnet is 100 K higher at CUT18 than that of CU15. A large margin of the temperature control on magnets is an advantage for CUT18. CUT18 is designed to be a standard undulator at the TPS for serving in broad scientific applications; therefore, the deflection parameter of CUT18 is designed to be greater than 2 to achieve high spectral performance. Maximum effective field strength of 1.18 T was measured at 170 K with a gap of 5.6 mm. An important feature of TPS-CUT18 is its ability to incorporate either cryo-coolers or LN 2 tanks as a cooling system (as depicted in Fig. 5 ). Like in the design of CU15, the cooling system is located at a separated vacuum, and the cold heads or LN 2 tanks can therefore be replaced without reassembling the magnet arrays or UHV components. This aspect of the design is particularly beneficial for field measurements and corrections in the laboratory, where no LN 2 supply is available. CUT18 was tested with liquid nitrogen tank cooling in the experimental hall of the TPS. When the temperature of magnets is controlled at 170 K, the cooling margin is more than 200 Fig. 4 : Cross sections of magnet arrays with conduction-cooling system. Fig. 5 : Current design of cryocooler-cooled PrFeB-based CPMU and extended design of a LN 2 - tank cooled NdFeB-based CPMU. W, which is sufficient for operating TPS-CUT18 at a beam current of 500 mA. CUT18 was installed at the TPS storage ring in December 2021and ready for commissioning. Summary Two CPMUs with magnetic and cryogenic performance above the required specifications have been successfully developed at the TPS. With a temperature control system, the temperature of magnets can be stabilized, and the CPMUs can provide stable, reproducible energy spectra. Drawing on the development of the TPS-CPMUs, CPMU technologies are further advanced and even commercially produced. (Reported by Jui-Che Huang)