The getter pump (15) comprises an envelope having selectively blackened outer surfaces (16) and including one or more non-evaporable getter NEG elements.

The transparent wall (4) with the frame (2) defines a closed chamber (6) containing the spacers (3), the light absorber (8) and a getter pump (15).

A water sorbent (224) has the primary purpose of pumping water vapor and a getter pump (218) has the primary purpose of pumping active gases.

The parallel pumps, i.e., the water sorbent (224) and getter pump (218) are disposed in a gas storage chamber (214) that is separate from the main housing (202) of the flywheel system.