Availability modeling approach for future circular colliders based on the LHC operation experience

Reaching the challenging integrated luminosity production goals of a future circular hadron collider (FCC-hh) and high luminosity LHC (HL-LHC) requires a thorough understanding of today’s most powerful high energy physics research infrastructure, the LHC accelerator complex at CERN. FCC-hh, a 4 times larger collider ring aims at delivering $10–20{\mathrm{ab}}^{-1}$ of integrated luminosity at 7 times higher collision energy. Since the identification of the key factors that impact availability and cost is far from obvious, a dedicated activity has been launched in the frame of the future circular collider study to develop models to study possible ways to optimize accelerator availability. This paper introduces the FCC reliability and availability study, which takes a fresh new look at assessing and modeling reliability and availability of particle accelerator infrastructures. The paper presents a probabilistic approach for Monte Carlo simulation of the machine operational cycle, schedule and availability for physics. The approach is based on best-practice, industrially applied reliability analysis methods. It relies on failure rate and repair time distributions to calculate impacts on availability. The main source of information for the study is coming from CERN accelerator operation and maintenance data. Recent improvements in LHC failure tracking help improving the accuracy of modeling of LHC performance. The model accuracy and prediction capabilities are discussed by comparing obtained results with past LHC operational data.

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Figure 1

CERN’s accelerator complex [11].

Figure 2

System life cycle phases.

Figure 3

Peak luminosities of fills during 2012. The lines indicate the technical stops [3].

Figure 4

LHC schedule for 2012 [65]; time scheduled for physics is marked with light orange.

Figure 5

Collider production cycle and cycle phases.

Figure 6

LHC operational statistics for 2012 [3] and for 2015 [69].

Figure 7

LHC system downtime for 2012 and 2015 based on data from [71].

Figure 8

The model concept with the main features.

Figure 9

Three levels of the collider operations model and normal transitions between states.

Figure 10

Result distribution of 1000 model iterations with Gaussian fit.

Figure 11

Actual LHC integrated luminosity production during 2012 compared to production in one model simulation.

Figure 12

Predictions for integrated luminosity production in the LHC during 2015 reference period compared to actual value.

Figure 13

The actual LHC production compared to a scenario with less nonproductive time.

Figure 14

Sensitivity analysis of luminosity production to UFO dump rate and quench probability, based on LHC 2012 operational data. Quench probability is the probability of a quench to occur in each UFO dump.