Construction of helical magnets for RHIC

Helical magnets are required in RHIC to control proton spin in a program for polarized proton colliding beam experiments. The basic construction unit is superconducting magnet producing a four tesla dipole field that rotates through 360 degrees in a length of 2.4 meters. These magnets are assembled in groups of four to build four Snakes to control spin in the lattice and eight Rotators to orient spin at two collision points. A collaboration with the Japanese institute RIKEN is providing financial support to carry out the program. After a successful R&D program to validate the design, the magnets are in the construction phase. The design of the magnets is reviewed, the construction approach is described, and test results from the first completed units are presented.