Abstract
The 3 GeV electron storage ring of the MAX IV laboratory is the first storage-ring-based synchrotron radiation facility with the inner surface of almost all the vacuum chambers along its circumference coated with non-evaporable getter (NEG) thin film. The coating provides a low dynamic outgassing rate and pumping of active gases. As the NEG coating was applied on an unprecedented scale, there were doubts concerning the storage ring performance. Fast conditioning of the vacuum system and over five years of reliable accelerator operation have demonstrated that the chosen design proved to be good and does not impose limits on the operation. The vacuum system performance is comparable with or better than that of other similar facilities around the world, where conventional designs were implemented. Observed pressure levels are low, and the electron beam lifetime is long and not limited by residual gas density. A summary of the vacuum performance is presented.
Highlights
Future machines that have a vacuum system based on NEGcoated chambers may need to take into consideration that the dominating gas in such systems is hydrogen, which is the case at the MAX IV 3 GeV storage ring
The vacuum conditioning has progressed well with the accumulated beam dose, and the electron beam lifetime continues to increase as the average pressure around the ring continues to decrease
The slope of the vacuum conditioning curve presented in Fig. 6 is 0.77 and this is slightly better than what has been observed in other synchrotron light facilities, 0.7 (Cox et al, 2008) and 0.69 (Herbeaux, 2008a)
Summary
The MAX IV facility in Lund, Sweden, is composed of two storage rings with electron energies of 1.5 and 3 GeV. A linear accelerator (Linac) serves as the full energy injector to the two storage rings and as a driver for a short pulse facility. The nominal energy of the Linac is 3 GeV (Eriksson et al, 2013). The MAX IV 3 GeV storage ring started commissioning in August 2015, and began to deliver photons to users in April 2017 (Tavares et al, 2018)
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