The Extra Low Energy Antiproton ring (ELENA) at CERN — part 2

I have been a project leader of the powering work package for the new Extra Low ENergy Antiproton (ELENA) ring at CERN since 2014. Being part of such an innovative and complex project has been a great managerial experience as well as an opportunity to participate in the design, installation and commissioning of a new complex machine based on cutting-edge technologies. In “Part 2” I describe the scope of the powering work package for the ELENA project at CERN and present its installation and commissioning phases. The start up of the main magnetic system is also covered.

The scope of the ELENA powering work package

The project schedule foresaw the commissioning of the ELENA ring with its injection and extraction lines in Q4 of 2016. It was supposed to be done using an external source of particles, however, in the final phase, the beam from the Antiproton Decelerator (AD) was intended to be injected into the new Extra Low Energy Antiproton ring at CERN. The delivery of the electron cooler was eventually postponed to 2018 and additional commissioning was carried out just for this element. My main objective as a leader of the powering work package for the ELENA project was to provide power converters together with associated control systems & IT infrastructure for the ELENA ring magnetic system, injection and extraction lines, electron cooler, new electrostatic transfer lines and the ion switch. The activity included organization and coordination of the installation and commissioning of the hardware and the controls software, as well as putting the magnetic system into operation. In order to supply different types of elements used to construct the ELENA, five families of converters have been chosen (APOLO, CANCUN, COMBO-DELTA, CUTE, High Voltage Boards). The total amount of converters depended not only on the number of magnet elements but also on the type of connection used. Some magnetic elements have been designed to be supplied independently while others should be connected in series. The tables below summarize the number of power converters delivered for operation. To ensure the continuity in case of hardware failure, additional spare devices from each converter families were added and reserved as a hot swap.

The installation and commissioning

The installation of the power components inside the Antimatter Factory facility began in early 2016. For technical reasons, two locations were chosen. The first one was the Antiproton Decelerator powering room, whereas the second one was an upper platform near the ELENA ring. In total, 460 operational power converters and their control systems were delivered for the project. 13 racks were installed in the powering room and 14 racks were distributed to the upper platform.

In order to efficiently coordinate and execute the work, I took an initiative and created planning and commissioning procedures for all teams involved in putting the magnetic system of the ELENA into operation. This included members of the organization from other groups and departments with whom I shared the documents using CERN data management services. I ensured that all information was available on time. After receiving a safety clearance from the inspection team, the ELENA Commissioning Coordination formally authorised the powering of each circuit. Before starting, it was essential to assure the safety of people and equipment, therefore final independent equipment checks and required evaluations were performed. Additionally, the following conditions had to be met prior to the commissioning of each magnetic circuit: power distribution for power converter racks available; DC cables connected on the magnet side; DC cables disconnected on the power converter side; cooling and ventilation systems operational; water distribution circuits connected and operational; magnet safety interlock system active; power converter and magnet installed and ready. The commissioning procedure of each magnet circuit comprised of several steps. They are presented in details in the table below.

These tests were carried out in chronological order. The starting point was the power converter individual system checks, which were executed in the CERN laboratory before the installation. Once power supplies were delivered and connected, the verification of the remote control system was performed. Afterwards, the electrical quality assurance (ELQA) tests were finalized. Their purpose was to check the integrity of the circuits with respect to the load parameters and earth faults. The analysis was done in an open loop at their connection point to the power converters. Later, the Warm Magnet Interlock Controller (WIC) was deployed and reviewed. To guarantee the protection for the magnetic system from overheating, the functional tests were performed in two phases. The first one was responsible for the verification of the interface between the interlock system and the magnets, while the second one checked the connections between the machine protection infrastructure and the power converters. The thermo-switches inside the magnets were constantly monitored by a PLC, which was supposed to trigger a fast abort signal to the correct power converter in the event of a fault. Both phases successfully verified the software and the hardware architecture of the interlock system, which was essential prior to the first powering. Later, all magnets were visually inspected to ensure that no objects causing potential harm were within the power loops. Afterwards, 10% of the nominal current was injected into the magnetic circuits for the first time. As the next steps, loop tuning and polarity checks were performed. After successful completion of all previous tests on all circuits, an eight hours heat run was carried out. It was executed at the nominal operating conditions for the ELENA’s magnetic system and at the end of the run, the thermal camera measurements were done to evaluate the heat distribution on the power converters, magnets and electrical circuits. The goal of the last test was to evaluate the performance of the magnet circuits in terms of current stability and it was carried out in parallel with the heat run. The delivered power converters fulfilled the following current ripple acceptance criteria: APOLO_2p ±90 mA; CANCUN_50 ±5 mA; CANCUN_20/CUTE_10 ±5 mA/±12 mA; COMBO-DELTA ±60 mA.

Summary

Commissioning such complex project was a challenge. Thanks to excellent communication, organization, coordination and teamwork, the system was ready on time and under budget. In total, 27 racks filled with more than 460 power converters with their control systems were delivered for the ELENA project at CERN. The electron cooler — the last missing part of the ring — was put into operation in June 2018. The new transfer lines for the experiments are to be tested in 2020. The achievement was published in the CERN Bulletin.

References

[1] A new ring to slow down antimatter

[2] 2016.11.23 — Michał Dudek — CERN ELENA project overview

Gallery

[1] Photographs of the extra low energy antiproton ring (ELENA) at CERN — installation & final layout