FACTS AND FIGURES

188 ESRF

ACCELERATOR OPERATION

Since the Extremely Brilliant Source (EBS) schedule was set in early 2017, the target to resume operation with users was always 25 August 2020. Despite the worldwide COVID-19 pandemic, which forced the ESRF to stop most of its activities for about two months during the crucial period of commissioning, all accelerators were ready for the milestone date! This was the result of intensive work carried out over previous months. Indeed, most nominal parameters were reached separately well ahead of schedule in particular, beam intensity, lifetime and emittance (in both planes). The challenge consisted in putting them all together on time!

As shown in Figure 162, on 2 June, several beamlines had already passed all necessary radioprotection tests and could receive beam. During the evenings and night shifts, the RF cavities were tuned in such a way that even more beamlines could progressively close the gaps of their insertion devices. In the meantime, bending magnet (BM) sources were progressively installed and the optics of the storage ring adjusted accordingly during machine-dedicated time so as to make this operation transparent for all other beamlines.

On 25 August, the first official day of User Service Mode (USM) operation, a total of 14 BM beamlines were equipped with their sources, with the machine perfectly tuned and reliably filled via top-up every 20 minutes. Over the four months of beam delivery, the

RUN NUMBER

2020-05 2020-06 TOTAL

2020

Start 25/08/2020 27/10/2020

End 14/10/2020 14/12/2020

Total number of shifts 150 143 293

Scheduled beam time (h) 1009 600 1609

Machine availability 953.80 592.10 1545.90

Availability 94.53% 98.68% 96.08%

Dead time for failures 5.5% 1.3% 3.9%

Number of failures 27 8 35

Mean time between failures (h) 37.4 75 46

Mean duration of a failure (h) 2.04 1 1.80

Table 6: Overview of storage ring operation in 2020.

longest interruption occurred during the first week of operation, and was the result of an intervention to replace a vacuum chamber on the straight section of ID14. One full day of this intervention took place during the USM week, which explains the moderate availability during the run 2020-05. Some repetitive communication problems occurred among the corrector power supplies, slightly impacting on the Mean Time Between Failures (MTBF), but the problem was solved when Ethernet switches were re-configured to full speed to improve the communication.

The fact that no other equipment of this brand- new accelerator suffered teething problems demonstrates the high level of reliability of most of the equipment as well as the great efforts made to solve any remaining issues. As shown in Table 6, the availability reached 96.08% and the MTBF 46 hours, which is remarkable for a new accelerator made up of thousands of new components.

Filling modes and top-up

Over the four months of operation in 2020, three different modes were delivered: 7/8 + 1, uniform mode and a temporary 32*12 mode. Concerning 7/8+1 and uniform mode, all nominal parameters (i.e., an intensity of 200 mA for a lifetime greater than 20 hours with a stabilised vertical emittance of 10 pm.rad) were successfully reached and delivered. However, the initially planned 16-bunch mode (as well as the 4*10 mA timing mode) could not be delivered with nominal parameters, in order to protect a ceramic kicker chamber, which was found to be unable to withstand the increased thermal stress. The temperature increase is a direct consequence of the intensity per bunch and explains why modes with fewer bunches cannot yet be delivered. The design and manufacture of new ceramic chambers are among the ongoing projects with the highest priority, with completion expected by the end of 2021. Until then, temporary solutions have been found by delivering 32*12 bunches at 150 mA or 16-bunch at 32 mA.

L. HARDY

Fig 162: The Control Room synopsis showing that, on 2 June 2020, many

beamlines were able to take beam at 200 mA.