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pressurized nitrogen tank with liquid nitrogen (≥ 0.5 bar pressure)
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flushed nitrogen lines in the heat exchanger (20 mins, 200-250 mg/s nitrogen gas flow)
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Attach solenoid valve (blue rectangle) to the nitrogen tank using the orange labelled screw.
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Open the valve of the pressurized LN2 tank.
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Place heat exchanger carefully in the nitrogen dewar.
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Try not to touch the temperature sensors on the rod or the nitrogen inlet.
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If you need to adjust the heat exchanger in the dewar, please move it ONLY along the yellow marked axis. Avoid touching the sensors (red) or the nitrogen inlet (blue).
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Switch on the electricity on the extension cord on the floor.
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After 30 mins the stage reaches its final temperature.
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The time and temperature thresholds are stored, but before your session, please check, if the values are correct:
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TIME = 7 mins, MIN-sensor threshold = -193°C, MAX-sensor threshold= -192°C
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The temperature sensors are set to have ±1°C buffer, for potential temperature fluctuations. The MIN-sensor will trigger filling at -192°C and the MAX-sensor will close the valve at -193°C, with the above written thresholds.
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When will the valve close? The solenoid valve closes if either the MAX-sensor's temperature threshold is reached or if the timer runs out (7 mins).
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Switch off the electricity.
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Close manual valve on the pressurized nitrogen tank.
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Carefully remove heat exchanger from the nitrogen dewar.
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Close dewar with the cap.
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Close the manual valve on the tank.
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Unscrew only the closest nut to the manual valve.
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Please DO NOT screw the other nuts to avoid damaging the solenoid valve
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Gently place the solenoid valve on the floor.
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Release pressure from the tank, and exchange empty tank for the full one at UZH-Warenannahme.
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Note: the tanks has one more fill left in it, when the level reaches the marked green line.
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Before exchanging and refilling the pressurized nitrogen tank, it is recommended to completely fill the nitrogen dewar. A full dewar lasts ca. 20 hours.
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Press the 'Valve test' button.
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After hearing the warning sound the controller will open the solenoid valve. The LN2 flow will automatically stop once the temperature within the dewar is in the preset range.
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