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ENEA - Fusion division
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Vacuum sub-plant of FTU
The vacuum plant has to produce a high level of vacuum inside the FTU vessel to keep it as clean as possible in order to obtain a high-performance plasma.
The value of the vacuum inside the vessel at cryogenic temperature (-180°C) is lower than 10-8 mbar, while at room temperature it is of the order of 10-6 mbar. With temperatures inside the chamber around 150°C (during "baking" operation), the vacuum value reaches 10-4 mbar. Following a plasma shot, the value generally rises to 10-7÷10-6 mbar, whilst before a shot vacuum must go back to about 2*10-8.
The vacuum plant was built by 'Peiffer Vacuum' and consists of:
- two pumping units for the pre-vacuum, each one with Pirani instruments, with an effective pumping speed of 16 litres/s. The value of vacuum reached with this system is < 5*10-3 mbar;
- six pumping units for high-vacuum, each with ionization gauges, with an effective pumping speed of 2200 litres/s. When the gate valve is closed, the value of vacuum reached is of the order of 5*10-9 mbar. All six units are able to maintain a vacuum value in the vessel of 2*10-8 mbar;
- one pumping unit for high vacuum, dedicated to spectroscopic analyses by means of quadruple instruments (mass spectrometry). The pumping capacity is 330 litres/s.
'PFEIFFER mod. DUO 060 A' rotary pumps are used for the pre-vacuum.
'PFEIFFER mod. TPU 2200' turbomolecular pumps are used for the high vacuum,
with rotary boost pumps of the same type as those used for the pre-vacuum.
as seen on a screen of the main control board
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