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BEPC-II Magnet Project

Project Overview

The BEPC-II magnets are Interaction Region magnets to be used as part of an upgrade to the Beijing Electron Positron Collider. Two magnets will be produced, both of which will be inserted within the solenoidal detector at one of the collision points.

Since the best use of the quadrupole focusing in this case requires placing the magnet as close to the collision point as possible, these magnets will be used within the magnetic field of the detector. This constrains the materials that can be used for construction to only non-magnetic materials. It also places severe demands on the structure of the magnet and it’s holding supports due to the reaction forces between the solenoid and the magnet.

To create the coil pattern for the final magnet, the coils will be manufactured using the computer controlled 11 axis-winding machine. Using ultrasonic energy, the cable is wound onto a support tube using a welding technique commonly used in industry for joining plastics. Since the magnet will be ramped relatively slowly, the use of 6 around 1 cable is acceptable.

The coil set for both magnets include an 8 layer main quad coil, a 2 layer horizontal dipole, a 2 layer vertical dipole, a 2 layer skew quad, and three anti-solenoid shield coils. The anti-solenoids are fabricated using a rectangular MRI style wire. These coils will be placed around different parts of the body of three coils. The inner diameter of the main quad for SCQ1 is 10 cm, with the outer diameter being 20 cm. For SCQ2, the inner is 12.2 cm, with 16.8 outer.

In all, there are 28 layers of superconductor used in this magnet, the most complicated design to date, using somewhat over three miles of superconductor.

IR Quadrupole Design Report (pdf)

Initial R&D Winding and Tests

Production Winding


For more information contact John Escallier.