CHESS-U accelerator work update

Production of CESR accelerator components for CHESS-U is well underway.

The fabrication of magnets, vacuum systems, power conversion components, instrumentation, and other systems has been ramping up over the last 6 months. The first few components of each type were fabricated in house, but most are contracted to upstate NY businesses. The following is an illustrated series of snapshots of activities.

The single most massive (and expensive!) system is the array of precision magnets needed to bend and focus the stored electrons. Machining precision for some low-carbon iron surfaces is ±0.0005 inches. The coils must satisfy rigid mechanical and radiation resistance properties.

Girder 3 Eric Banta James Drake
Girder #3 (of 12) was assembled in November across the street from Wilson Lab at the “Annex.” Eric Banta and James Drake with occasional help from Tom Dugan are carrying out this work.

Before utilities, instrumentation and magnet power converters are installed, the magnets are field mapped and aligned on each girder at the Annex building. After this stage, the alignment of magnets relative to the girder is maintained at the 50 micron level, facilitating final installation and alignment. Once complete, the girder and magnets are moved across Rte. 366 to the L0E hall in Wilson Lab.Paul Osetek, Sasha Temnykh, Dragana Jusic

On the right, scientist Sasha Temnykh is making final checks while surveyors Paul Osetek and Dragana Jusic finish a successful magnet alignment.

Once in the L0E hall in Wilson Lab, the vacuum chambers and final plumbing, electrical, and instrumentation are installed and tested along with the local “chopper” magnet current regulators. 

Rich Gallagher L0E

Rich Gallagher directs the weekly girder trimout meeting in the L0E hall. Staff responsible for mechanical design, utilities, wiring, power conversion systems and instrumentation attend. Three girders with tested and aligned magnets, one 95% wired and plumbed, are in the background. 

The magnet power conversion system must provide individual control of more than 100 magnets in the CHESS-U achromat region. Production and testing of components is well underway.Marshall Berry computer interface boards

On the right, Marshall Berry inspects computer interface boards. More than 120 of various kinds are being manufactured by local firms and tested in house.

The individual magnets in the CHESS-U achromats require well-regulated currents from ±12 to 300 amps. These, as with the existing CESR magnets, are provided by in-house designed units that can be ramped together in a coordinated manner for smooth changes to conditions with stored beams. Stability is a few parts in 105 where required.

300 Amp switch-mode current regulators (“Choppers”)


toroidal coils
Toroidal coils for precision current control

The CHESS-U vacuum system is compact and complex, making for a challenge to find places for all components.

CHESS-U vacuum system

CHESS-U vacuum system

Sliding joints (shown above) to accommodate thermal expansion and squeezing water fittings between magnet poles are a couple of the challenges to vacuum system designers. There are three types of vacuum chambers in the CHESS-U region of CESR, each is approximately 4.6 m long. The “Dipole A” chamber is the most complex, with accommodation of the x-ray extraction line and Beryllium “crotch” to absorb direct radiation from the adjacent bending magnet.Ed Foster Dipole A chamber

On the right, welder Ed Foster prepares to weld a Dipole A chamber. Accurate fixtures to hold position during welding are necessary to assure proper fit in quadrupole magnets at either end with only ~ 1 mm gap between chamber and magnet pole tips. (The chamber is shown upside-down with the X-ray line on the left and CESR beam line on the right.)

As 2018 begins, nearly all equipment and outside machining work is on order and daily deliveries are the norm. Three girders with tested and aligned magnets are in the L0E experimental hall with one nearly complete. Three technicians and a physicist will be committed to girder production at the Annex while five technicians will be installing utilities and instrumentation in L0E. Vacuum chambers are in production and will keep pace with the magnet girder deliveries. CHESS-U is on schedule for a June 4 start of installation.