In CERN's cryogenics group, ON/OFF valves are operated using solenoid actuators, while control valves (CV) utilize piezo actuators. It is being tested whether piezo actuators can also be used for ON/OFF valves; for this reason, a dedicated campaign in Cobalt-60 has been launched to conduct these tests. The main advantages of piezo actuators are:

• Piezo actuators need no energy to maintain their active state, leading to no heat generation.
• A similar bending element is used in cryogenic control valves, ensuring compatibility and efficiency.
• Less power consumption compared to solenoid actuators, which allows more supported channels per card from an electronics perspective.

When the piezo actuator is ON, port 2 is connected to the input, allowing air to fill the closed volume. When the piezo actuator is OFF, air flows from port 2 to port 3, releasing the air from the volume. For testing, a pressure regulator maintains the pressure at 6 bar, with an input pressure sensor and an output pressure sensor for each piezo actuator under test. Once the input and output pressures stabilize at 6 bar, the volume is filled with air, and a steady-state condition is reached. A flowmeter is used to measure any air leakage when the steady-state condition is achieved. Each piezo actuator is tested individually.

The following plot presents the results of a dry run test conducted on one piezo actuator. The top plot shows the input piezo voltage; when the voltage increases, the piezo turns ON and begins to fill the closed volume with air. The second plot displays the input pressure, while the third plot shows the output pressure. After approximately 15-20 seconds, 2 liters of the closed volume have been filled. The bottom plot illustrates the air flow measurement, which, due to instrument constraints, saturates at 3 l/min. Once the steady-state condition is reached, the air leakage is measured at 0 l/min.

The setup and facilities are depicted in the following images.