FNAL AOSC Undulator Requirements 380252swk.pdf

Specifications for the Amplified Optical Stochastic Cooling Undulators

The amplified optical stochastic cooling experiment, which is slated for Q4 2026 at the Fermilab IOTA storage ring, requires the design and fabrication of two identical electromagnetic undulators. The required geometric parameters, magnetic and performance characteristics and required fabrication tolerances are given in the table and comments below. Figure 1 shows an example spectrum simulated in Synchrotron Radiation Workshop (SRW) using 100 MeV (KE) electrons.

Geometric parameters

Maximum physical length 950.0 mm

Undulator period 80.0 mm

Number of periods 9 (not including terminations)

Minimum Vertical aperture (pole-to-pole)

12.6 mm (larger aperture is preferred subject to max on-axis field requirements)

Magnetic and performance properties

On-axis fundamental wavelength for electrons with 100-MeV kinetic energy

2188 nm

Nominal undulator parameter (“K”) 1.494

Nominal on-axis field 2.00 kG

Maximum operational field (on-axis) 2.25 kG

Maximum dT (from 0A to full current) ~10 K

Minimum “good-field” region (<1e-4 integrated field deviation)

+/- 6.3 mm

Yoke material 1006 steel, ARMCO or equivalent

Required tolerances between the two undulators

Relative difference in wavelength < 0.6 %

Relative difference in undulator period < 0.5 %

Relative difference in on-axis field < 0.5 %

Additional magnetic requirements: End terminations (e.g. [1/4, -3/4] or [1/2] schemes) should be included to zero the field integrals; separately powered trim coils may be included if needed. Schemes that produce nonzero angle offsets within the undulator are less desirable than those producing position offsets. For each fabricated undulator, the total angular change of the ideal trajectory should be < 0.25 mrad, and the total position offset of the ideal trajectory should be limited to ~20 µm. End terminations should be individually powered for fine tuning of the field integrals. Uncorrected deviations from the on-axis model field should be limited to < 0.001*B0 ~2.0 G. Field-mapping measurements should be performed at nominal and maximum excitations and demonstrate compliance with requirements on zeroing of the field-integrals and the corresponding theoretical trajectory offsets.

Comments on cooling: Indirect water cooling of the yokes and, if necessary, the coils is preferred. The maximum pressure drop across the magnet should be 60 PSI. The typical inlet temperature and pressure are 92F and 100 PSI, and outlet temperatures are typically software interlocked at 120 F. The desired maximum temperature rise of the yokes/coils for maximum excitation is ~10 K. Higher values may be acceptable provided that the magnet is thermally stable and the required inlet/outlet temperatures are in range.

Comments on power supplies: If possible, power requirements should be compatible with the existing 10kW-class Genisys 125V/80A supplies that are available at IOTA. Maximum operation below 50V is highly desirable but not required.

Comments on physical structure: The maximum physical length of the undulator including all covers, supports, etc… should be <950mm. Any proposed breaches of this envelope, particularly within ~60 mm of the magnetic axis, must be discussed with and approved by the appropriate technical personnel at Fermilab. Not including coils, the yokes (including termination poles) are anticipated to have a total length of ~920 mm. If needed, alternative end-termination schemes can be considered. The nominal magnetic axis of the system should be ~251.3 mm (+/- 2 mm) above the base of the contact point for the undulator’s support structures. There is a desired hole pattern for mounting to existing adjustable support stands.

Exact details will be provided later.

Comments on surfaces: The body of the magnet should be painted to prevent corrosion with the exception of the pole tips. The pole tips should be appropriately oiled to prevent corrosion. The pole tips should not be coated with nickel.

Comments on alignment features:

During the design phase, the number, location and specifications of holes for alignment nests must be coordinated with Fermilab technical personnel.

Comments on lifting fixtures:

An appropriate solution for safely and stably lifting the magnets via overhead crane should be provided.

Comments on documentation:

Comprehensive documentation of the magnet design (mechanical/design, thermal, electrical, magnetic, …) must be provided to Fermilab technical personnel for approval prior to the start of fabrication.

Comprehensive documentation detailing measurements of the fabricated magnets must be provided (magnetic performance and field quality, electrical performance, …).

Delivery: 18 weeks (or sooner) after receipt of order.

Figure 1: SRW simulation of the undulator radiation’s spatially integrated, spectral-energy density for a single 100 MeV electron. Only the fundamental band and the tail of the 2nd harmonic are shown. Includes an aperture with 7-mm radius at ~1.44 m downstream from the undulator center. Simulation includes [¼,-¾] end terminations.