By Ina Reichel
After the summer shutdown, the ALS went back to user operations on Sunday, October 12, as scheduled. A lot of work for both the ALS and ALS-U was accomplished during the shutdown, including a key milestone for the upgrade.
More than four years after starting to install magnet supports and more than two years after installing the first magnets, the mechanical installation of the accumulator ring (AR) magnets and magnet rafts is complete.
“This achievement is the result of our dedicated engineers and technicians who worked hard to fabricate and install around 240 magnets, 84 vacuum chambers, and rafts,” explained Matthaeus Leitner, ALS-U technical director.
During the summer shutdown, the remaining three dipole magnets and three rafts were installed in Sector 12. This sector was installed last, as it also houses the new booster-to-accumulator-ring (BTA) transfer line, so space is highly restricted in that area of the tunnel.
The team also installed all vacuum chambers for the AR, connected 85% of them, and pumped them down.
The BTA transfer line installed during this shutdown consists of six bend magnets (two vertical, four horizontal), 11 quadrupole magnets, two septum magnets, and three kicker magnets in the AR. The BTA is squeezed in between the AR and the booster-to-storage ring (BTS) transfer line, requiring all elements (including the remaining AR magnets and rafts) to be installed using a crane instead of the scissor lift like most of the AR. This necessitated the removal of a number of consecutive roof blocks to allow crane access to the whole area. The height of the AR introduced another complication. Both the booster and the storage rings are at the same height, but the AR is higher, so the transfer line needs to go “uphill.” This requires the transfer line to not just have the usual horizontal bend magnets but also some vertical bend magnets.
A diagnostic beamline for the AR was also installed. This will allow measuring the emittance (which is related to the beam size) of the beam in the AR. Whereas most emittance measurements in electron synchrotrons employ simple optic imaging methods, this device will rely on interference methods. Because of the smaller beam size in the AR, the traditional method lacks the resolution the new method offers.
The commissioning of the AR radio frequency (RF) system is in progress. Electronic racks for both the AR and the BTA were installed as planned, including some related to the AR RF system. Those racks mostly contain power supplies for the AR and BTA, with some instrumentation and controls electronics.
Many new cables, which will eventually power the AR, were installed. Each of the twelve AR sectors requires dozens of cables of different types. Some will carry power to the magnets; others will read out instrumentation or temperature sensors. To date, the cables for one complete sector and some of the cables for a couple of additional sectors have been installed.
In addition, a cable inventory is underway in preparation for the dark time. All existing cables need to be cataloged to ensure that they have the right specification for their functions and that there is enough room in each cable tray for all the cables that will be there.
“The cable plant group was responsible for cataloging cables for Sectors 7, 8, and 9 originating from the storage ring pit,” said Priyanka Gupta, Facility Integration and Installation lead engineer. “The team, composed of facilities electricians, electrical coordinators, interns, and technicians, successfully cataloged a total of 2,882 cables,” she added.
The cataloging effort helped identify routes, yielded a database for all cables in these sectors, as well as helped determine the safety requirements for their removal. This initial effort took four months and was quite exhaustive.
“For future sectors, each subsystem will identify the specific equipment and cabling that needs to be preserved during the dark time,” said Gupta. “This approach will allow us to streamline the cataloging process for other sectors by focusing only on essential equipment and cabling.”
In addition, the commissioning of the booster bend power supply is finally complete. This replaces the existing power supply, which has had reliability issues in recent years. It will also allow the booster ring to ramp up to 2 GeV, which will be needed for the new storage ring after the upgrade. The current storage ring runs at 1.9 GeV. The new supply has been used in routine operations since the start of user operations in October.
“We’re really proud of what we’ve accomplished and can’t wait to move on to the next phase,” Leitner exclaimed.
Looking ahead, he said upcoming work will include electrical installations for the accumulator ring and building the first rafts for the new storage ring.
Multiple projects around the ALS enhanced the safety for both people and equipment.
The seismic retrofit of the storage ring tunnel continued. The goal is to make the accelerator enclosures more earthquake safe by better attaching the walls to the floor and the ceiling blocks to the walls, as well as adding stitch plates to the walls.
The system that provides power to all racks at the ALS had not been upgraded since the facility opened in 1993, and was no longer code-compliant. During this shutdown, Rick Lellinger, electronics engineering associate, ran the team that replaced it with a new system using power distribution units (PDUs).
The ALS has a complex system of interlocks to protect both people and equipment from being damaged. Part of the equipment protection system is an interlock of the storage ring feeder master. This was upgraded during the shutdown.
A lot of equipment at the ALS is cooled using low-conductivity water (LCW). The impellers that help pump LCW through the system were upgraded to ensure that, while running both the accumulator ring and the current storage ring, the system has enough water flow. This also adds redundancy to the system.
There was work on some electrical banks to prepare for the substation upgrade in Fall 2026, which will take the ALS accelerator offline and pause user operations for the second half of the calendar year. This work required a three-day ALS-wide power outage. “All power to the ALS comes through switch station A3; it’s original to the ALS construction,” explained Steve Rossi, ALS deputy for business operations. “It’s currently past service life and represents a major operational liability for us since parts are becoming harder to come by and the lead time for switch gear like this is often a year or more, never mind the construction duration required. Replacement will retire reliability issues and worker safety will be greatly improved with a major reduction in arc flash potential and other modern safety features. I know I’ll sleep better at night knowing this risk has been addressed.”
All in all it was a busy and successful shutdown reaching a key milestone for ALS-U and also getting work for the current ALS done.