The vacuum chambers of MAXIV are only 22 mm of diameter; the chamber size was chosen in order to fit inside the compact magnets of the storage ring. Due to the small diameter of the chamber, the conventional way of pumping using lumped pumps is not efficient nor practical, accordingly, the vacuum system of the 3 GeV storage ring is fully NEG (non-evaporable getter) coated vacuum system.
NEG coating provides the needed pumping and reduces the outgassing due to the photons hitting the chamber walls. For NEG coating to be pumping down it should be activated, activation means that the coating should be heated up to around 200˚C, consequently, any venting to atmosphere will cause the NEG coating to be saturated (can not pump) and should be followed with NEG activation to restore the coating performance. At MAX IV, in order to activate the NEG coating, a major intervention is needed, where the whole achromat (23 m) should be lifted and heated up inside an oven. Such an intervention would last from 2 weeks (if the achromat does not have insertion devices) up to 4 weeks (for achromats with insertion devices).