Measuring the Magnetic Center Behavior and Field Quality of an ILC Superconducting Combined Quadrupole-Dipole Prototype

• Published in: IEEE transactions on applied superconductivity Vol. 20; no. 3; pp. 1964 - 1968
• Main Authors: Spencer, Cherrill M, Adolphsen, Chris, Berndt, Martin, Jensen, David R, Rogers, Ron, Sheppard, John C, St. Lorant, Steve, Weber, Thomas B, Weisend, John, Brueck, Heinrich, Toral, Fernando
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01-06-2010; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acceleration; Applied sciences; Beams (structural); Coils; Cryogenics; Electrical engineering. Electrical power engineering; Electromagnets; Electrostatic, collective, and linear accelerators; Exact sciences and technology; Experimental methods and instrumentation for elementary-particle and nuclear physics; Holes; Houses; Laboratories; Linear accelerators; Magnetic field measurement; Magnetic measurements; Micrometers; Nuclear physics; Physics; Prototypes; Quadrupoles; Stability; Superconducting coils; Superconducting magnets; superconducting quadrupole magnet; Superconducting supercolliders; Superconductivity; Various equipment and components; Europe; Spain; Harmonic; Prototype; Magnet; Bias; Magnetic measurements; Linear accelerator; superconducting quadrupole magnet; Quadrupoles; Cryogenic temperature; Magnetic measurement; Superconducting magnet; Cavity; Cryogenics; Linear colliders; Dipole
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2010.2041919

The main linacs of the proposed International Linear Collider (ILC) consist of superconducting cavities operated at 2 K. The accelerating cavities are contained in a contiguous series of cryogenic modules that also house the main linac quadrupoles, thus the quadrupoles also need to be superconducting. In an early ILC design, these magnets are about 0.6 m long, have cos (2¿) coils, and operate at constant field gradients up to 60 T/m. In order to preserve the small beam emittances in the ILC linacs, the e+ and e- beams need to traverse the quadrupoles near their magnetic centers. A quadrupole shunting technique is used to measure the quadrupole alignment with the beams; this process requires the magnetic centers move by no more than about 5 micrometers when their strength is changed. To determine if such tight stability is achievable in a superconducting quadrupole, we at SLAC measured the magnetic center motions in a prototype ILC quadrupole built at CIEMAT in Spain. A rotating coil technique was used with a better than 0.1 micrometer precision in the relative field center position, and less than a 2 micrometer systematic error over 30 minutes. This paper describes the warm-bore cryomodule that houses the quadrupole in its Helium vessel, the magnetic center measurement system, the measured center data and strength and harmonics magnetic data.