0428同步年報-2021-全

100 ACTIVITY REPORT 2021 The Design and Fabrication of Liquid Nitrogen Transfer System for Taiwan Photon Source Beamlines A t Taiwan Photon Source (TPS), the main liquid nitrogen (LN 2 ) transfer line of length 600 m for beamline endstations was installed in 2015. It previously supplied LN 2 to a maximum of 24 beamlines. TPS 13A , of which the aim is advanced and general studies of biological structures and structural kinetics in solution or condensed forms under environmental simulations, from atomic to micrometer scale and time resolution ranging from microsecond to minute, was installed during 2018 and 2019. We designed and self- manufactured one LN 2 transfer line according to the requirements of TPS 13A , to supply LN 2 into the double-crystal monochromator (DCM), to solve the problem of thermal deformation of the crystal. Otherwise, the keep-full device was intended to be used in place of the chiller's phase separator. The installation and commissioning of one LN 2 -transfer system for the TPS project were completed in 2015. 1 This system consisted of two transfer lines (length 600 m), eight keep-full devices, and 24 cryogenic control valves for 24 straight sections of beamlines. The consumption of LN 2 required for each beamline is 20 L/h. The LN 2 supply from a single storage tank (60 m 3 ) was refilled every day from an LN 2 truck. Another transfer line of length more than 300 m that supplied users of Taiwan Light Source (TLS) was installed in 2003. The configuration of the LN 2 - transfer system in TLS and TPS is shown in Fig. 1 . During the years 2015–2018, four LN 2 branch lines for TPS beamlines ( 05A , 09A , 23A , 25A ) were installed, enabled, and used LN 2 to cool the beamline equipment for the DCM. Some unexpected problems appeared on these four LN 2 branch lines, such as that the separator filling process being too noisy, ice or water formed due to cold nitrogen gas exhaust, the pressure downstream of the pressure-reducing valve that activates the safety valve was excessive, and heat loss caused by the non-vacuum design of the pressure-reducing device was excessive. In 2019, we designed, constructed, installed, and tested one vacuum-shielded LN 2 branch line for TPS 13A . Based on long-term operation in an early beamline LN 2 branch, some problems should be considered and avoided in this self-manufactured LN 2 branch line, such as reducing the heat load, reducing the sound, decreasing the two- phase flow, improving pressure stabilization, and avoiding the ice and water phenomenon. For these purposes, we designed three devices construct in the branch line, a pressure regulator, a keep full, and a sound-suppression device with a heater. Figure 2 shows the structure of a pressure-regulator device. One pressure-regulator valve connects with an LN 2 pipe located in a chamber for gaseous nitrogen. For maintenance, the top and bottom caps of the chamber can be opened. We can open the caps and adjust the pressure of the pressure-regulator valve during cold conditions while pure gaseous nitrogen flows into the chamber. We installed a check valve in the chamber to avoid the worst-case based on which the pressure-regulator valve leaks after thermal cycles. Two pressure transducers were installed at the downstream side and the GN 2 chamber. This device's Fig. 1 : Configuration of the LN 2 transfer system in TLS and TPS. Fig. 2 : Pressure-regulating device.