|The ALS Shutdown: Behind the Scenes|
As we head into another ALS shutdown, it’s interesting to take a look “behind the scenes” of our facility to get a glimpse of what it takes to keep this amazing machine running. We recently sat down with Steve Rossi, ALS project and facility management group leader, to talk about the upcoming shutdown, May 5 through July 10.
“The general theme for this shutdown is operational reliability and improvements,” says Rossi. “It’s not necessarily stuff that’s ‘cool and fun’ for users, but the increased reliability we’ll gain will be a huge benefit for them.”
The big-ticket project that’s really setting the timing and duration of this shutdown is the replacement of the ALS storage ring radio frequency (SRRF) crowbar system with a new high-voltage switch. The new switch will provide the same over-voltage protection for the SRRF system that the crowbar system did, but with increased reliability.
Developed in-house by electrical engineering staff matrixed to the ALS, the high-voltage switch has required years of development and robust testing. It represents one of the final stages of the larger $4.8 million RF upgrade project—two years ago was the klystron replacement, last year the high-voltage power supply replacement, and next year will be the waveguide switch matrix.
Historically the ALS has had one klystron driving two RF cavities in the storage ring. After next year, there will be two klystrons driving two RF cavities and a new switch matrix will give the ALS the ability to quickly change configurations so that one klystron can drive either cavity or, at reduced beam power, could drive both cavities. The net benefit will be that the ALS will be able to get light back to users quickly in the event of a klystron failure. The switch matrix should require just an hour or two, whereas a klystron replacement is more like a day or two at best and is fraught with potential technical pitfalls.
“It will be a very flexible system that reduces our need for spares,” says Rossi. “Since spares for the klystron are about $500K apiece, that’s a very good thing.”
Other shutdown projects will focus on the low-conductivity water system, something the ALS has been working on for years. Corrosive by nature, the low-conductivity water system causes maintenance problems like water leaks and blockages. An anti-corrosive agent, Benzotriazole, was recently added to the ALS low-conductivity water supply and the effects are being closely monitored. This shutdown will include the replacement of a number of low-conductivity water flow meters in the storage ring with vortex-based meters that have no mechanical or moving parts, which should reduce corrosion issues that can cause the beam to trip, costing users valuable time. The water system will also get two new tower fans out at Building 37.
This shutdown will also include surveying and aligning the storage ring and replacing beam position monitor (BPM) buttons (part of the $7.6 million, multi-year controls upgrade project). The new BPM buttons will be connected to a new electronics system, which will give the ALS accelerator physics staff a much better tool for monitoring the beam. CXRO will be using shutdown time to complete their new cleanroom in Sector 12.
Rossi is often asked how shutdowns are scheduled, and the answer is that it’s not quite an exact science. “We look at our entire project portfolio and choose the start date based on the forecast readiness of the majority of the portfolio,” says Rossi. “The overall duration is set by the critical path of the longest project, along with the needed start up time to commission any new equipment.”