Michael Hahn reporting for

1. Michael Hahn reporting for Jean-Louis Bersier, Francis Bodart, Emmanuel Burtin, Dominique Cognie, Gilles Debut, Franck Demarcq, Michel Garrec, Pierre Guerin, Roberto Kersevan, Gildas Le Flem, Laurence Loiacono Levet, Gérard Luce, Isabelle Parat, Daniela Schmied, Jacqueline Tucek and Vincent Marion (trainee)

2. Storage Ring machine parameters • Circumference 844m • E = 6 Gev • 200 (250) mA multibunch • 90 mA 16 bunch • Vertical emittance 0.025 nm • Booster machine parameters • Circumference 300m • Repetition rate 10 Hz

3. Storage Ring Vacuum System • Stainless Steel 316 LN Vacuum chambers connected by CF150 flanges • Lumped pumping by SIP Varian Starcell…. • and NEG St707 cartridges by SAES • Two long / three short machine shutdowns per year • In-situ baking equipment installed

4. Beam-Lifetime is the key quality parameter as far as vacuum is concerned, we obtain 80 hrs at 200 mA in uniform mode • Especially the modifications in the straight sections with the goal of an increased synchrotron light brilliance are critical for restarts: Quick conditioning is crucial in order to obtain acceptable Bremsstrahlungs-Level in the Beamline hutches • ESRF follows two main directions to increase the brilliance • low gap Insertion Device vacuum chambers (10mm externally) with distributed pumping provided by NEG coating produced in-house at ESRF under CERN license • In Vacuum Undulators allow the magnets to come even closer to the electron beam (5.5mm), the vacuum tank is equipped with massive pumping by Ti Sublimators, SIPs and a 500 l/s St707 NEG cartridge

5. topics.. Definition Preventive Maintenance / Downtime of Accelerators Control System tools / Systematic Vacuum failure analysis Additional machine data analysis for correlation Temporary repair during Machine Shifts Final repair / Machine Shutdown philosophy: To bake or not to bake…. Discussion

6. The goal of our activities is to keep the unscheduled downtime of the accelerators due to vacuum as low as possible: One important parameter for the overall performance of the ESRF is (unwanted downtime / scheduled user hours) * total budget ESRF – all interventions and repairs should therefore take place during scheduled downtimes

7. Control System tools

8. Air leak • This dynamic tool based on the ratio of normalised pressure in a given filling mode, helps us to detect : • In USM, air leaks at a very early stage (ratio > 2) • Ratio >5 signifies real problem on the SR (SR hitting vacuum chamber wall etc.) • - In MDT, quick pressure peaks can be correlated with HOM’s in the RF cavity areas or bad RF finger contacts in an a transient bellow vacuum vessel can be identified

9. The application is programmed in Labview for Unix, it gives the possibility to compare the vacuum situation in a given mode of the Storage Ring (16 bunch, 1/3, 2/3, hybrid, single, uniform and “exotic” modes) to a stored known as “good” situation. As the data is presented as a factor compared to the reference for all relevant pressures of the SR we can identify degradation or potential vacuum problems in a single view. To store a “reference” situation the application provides a “Save” function that asks for the operation mode and stores the data accordingly with the actual time and date. This data set will be stored independent from the historical database which increases the availability time (HDB data would be saved for one year online, older data on tape). As an additional tool we have LINUX PCs in each cell that store permanently on a FIFO base all the vacuum data with 1 Hz, the intelligence of this “interface PCs” allows also to trigger a higher sampling rate for HDB when something is “happening” on the gauges. The ion pump current is monitored permanently to have an additional confirmation of p behaviour The early recognition of air leaks by means of these methods made that since 2001 all leak detections could be carried out during scheduled downtimes

10. Additional machine data analysis for correlation Lifetime (h) Change of the slopes on the pressure curve as well as on the lifetime profile pressure (mbar) Integrated dose (A.h)

11. Beamloss detectors cartography

12. The beamloss detectors are scintillators connected to each of the 64 dipole chambers on the SR, a MATLAB application allows to present the data representative and time-resolved. Differing from the real-time buffer as described for “vacgauge” this appliction recalls data from HDB (one hour from the desired starting time) We use also Bremsstrahlung data from XBPMs and a dedicated ionisation chamber in ID6 beamline hutch to qualify the conditioning of new ID vacuum chambers

13. pressure (mbar) CV9 (ion pump current) Helium detection + Repair CV11 (penning gauge)

14. Identification of the leak, localization prediction by reading gauges and SIP currents location: Precision in the range of 1m • Leak detection during machine dedicated time, temporary fixing with varnish • Exchange of the Vacuum chamber during ESRF machine shutdown, with bake or warming depending on amount of new surface area - update of the history file • Improvements of spare chamber design following analysis of the failure

15. CELL15 CELL16 mbar mA CV2 CV4 C15-2 CROTCH1 CV11 CV11 CROTCH2 CV2 CV4 CROTCH1 C15-1 C16-1 C17-1 C14-7

16. Due to the water leak on a special absorber (one of a kind) we had to change absorber, dipole chamber, crotch chamber and re-baked the system after careful optical inspection with the endoscope During the restart this weekend we could recover quickly a reasonable average pressure and obtained (yesterday) lifetimes in the > 70 hrs @ 200mA

17. Preventive Maintenance for Storage Ring Operation ACKNOWLEDGEMENTS The first part of this presentation reports on work initiated and realized by Daniela Schmied, Isabelle Parat and the ESRF Vacuum Measurement & Analysis subgroup. Special thanks to the ESRF Computing Services. Thank you: Gilles Chazot, Graham Naylor, Laurent Farvacque