Stimmen - 4, Durchschnittliche Bewertung: 3.3
(
)
)
|
Anleitung Zusammenfassung
Cottrell et al Version 0.2 Contents 1 Getting Started 3 1.1 Layout of the liquid handling system 3 1.2 Layout of the in situ sample stick 4 1.3 Layout of the pump 4 2.1 Sample loading 6 2.1.1 Loading Vessel 1 6 2.1.2 Loading Vessel 2 6 2.2 Evacuation of the system 6 2.2.1 Removing air from Vessel 1 7 2.2.2 Removing air from Vessel 2 7 2.2.3 Removing air from Vessel 3 7 2.2.4 Evacuation of the sample cell 7 2.3 Freeze-Pump-Thaw cycle 8 2.3.1 Sample in Vessel 1 8 2.3.2 Sample in Vessel 2 8 2.3.3 Sample in Vessel 3 9 2.4 Liquid transfers 9 2.4.1 Vessel 1 to sample cell 9 2.4.2 Vessel 3 to sample cell 10 2.4.3 Recovery of liquid in manifold to Vessel 2 10 2.4.4 Recovery of liquid in sample cell to Vessel 1 11 2.4.5 Recovery of liquid in sample cell to Vessel 2 11 2.4.6 Recovery of liquid in sample cell to Vessel 3 11 2 General procedures 6 3 Example Experiment 13 1 Getting Started This manual describes the liquid handling system and the in situ sample cell as used on the DEVA instrument with the “RF” spectrometer, for either normal muon spins relaxation or RF resonance experiments. 1.1 Layout of the liquid handling system The Muon Liquid Handling System has been designed to facilitate the in situ degassing and transfer of samples into and out of the sample cell. The main features of the liquid handling system are shown in Figure 1. Figure 1 The layout of the front panel on the muon liquid handling system. In general, the rig consists of three glass vessels for the storage of liquid samples, any of which can be opened to a vacuum for the purposes of degassing by the freeze- pump-thaw method. Once degassed, the sample liquid can be transferred to the sample cell contained within a cryostat without further exposure to the air. In addition, samples may be returned to the rig for further freeze-pump-thaw cycles or for disposal. Text Box: Vessel 1 Text Box: Vessel 2 Text Box: Vessel 3 Text Box: To cell Text Box: Baratron Text Box: To pump Text Box: Gas pressure Text Box: Cell pressure Text Box: Inlet 1 Text Box: Inlet 2 1.2 Layout of the in situ sample stick The liquid sample stick is designed to fit into the DEVA flow cryostat, details of which can be found in the DEVA manual. It consists of a shapol target cell 30 mm x 30 mm with a mylar window upon which may be mounted an RF coil. Two stainless steel capillaries provide a means of flowing liquid into and out of the cell along with feed throughs for an RF excitation signal and a pick-up coil. Figure 2 The liquid-sample cell mounted on a sample stick with a flat coil suitable for RF .SR. 1.3 Layout of the pump The pump used with the Muon Liquid Handling System consists of a rotary pump used to reduce the pressure of large volumes of gas and a turbo pump to achieve a high vacuum. The main features pump used on the liquid handling system are shown in the diagram below. Figure 2 The layout of the front panel on the vacuum pump used with the muon liquid handling system. Text Box: Off/Run switch Text Box: Roughing/Turbo switch Text Box: Pressure reading Text Box: Turbo control panel Text Box: Turbo Pump Text Box: Rotary Pump 2 General procedures 2.1 Sample loading At this point, the system will be open to the atmosphere, ensure that valve V2 is closed to prevent air condensation in the cold trap. 2.1.1 Loading Vessel 1 • Open the tap on the right-hand side of Vessel 1. • Open tap A and valve V11. • The liquid should be poured into the system very slowly to avoid liquid leaving the vessel via the side tap. • When loading is complete, close the side tap, tap A and valve V11. 2.1.2 Loading Vessel 2 • Ensure tap E and valve V7 are closed. • Remove the rubber septum on Vessel 2 and open tap E. • Opening valve 12 allows the liquid to be poured directly into the glass bulb. • When loading is complete, close tap E and valve V12. Replace the rubber septum carefully making sure not to place any strain on the metal-to-glass seals. It is important to note that a small amount of liquid may remain in the system after sample loading is finished. Care must be taken to prevent this liquid reaching the pump. 2.2 Evacuation of the system After loading the sample liquid, the system must be evacuated. However, air and possibly a small amount of liquid will be in the main body of the system. To avoid air condensation in the cold trap, the nitrogen dewar surrounding it should be removed and the glass U-tube allowed to warm-up. • Close all the taps on Vessels 1, 2 and 3. • Ensure that the pump is switched to roughing before opening valve V1. The pump can be switched to turbo if a high vacuum is required. Once the system is evacuated, air must be removed from the vessel containing the sample to be cleaned. The system must be ‘let-up’ to atmospheric pressure using helium gas. This is achieved by first closing valve V1 and then opening valves V3 and V9. The pressure of gas in the system can be read from the baratron gauge. 2.2.1 Removing air from Vessel 1 Once the system has been pressurised, tap ...