Abstract: A method of assembling an annular magnet and a pole piece in a chamber of a cylindrical core at a predetermined height is disclosed. The magnet assembly tool has a first portion with a diameter of approximately the diameter of the chamber less the width of the annular magnet and a second portion with a diameter of approximately the width of the chamber. Therefore a gap is formed between the outer wall of the chamber and the first portion of the magnet assembly tool when the tool is inserted in the chamber. The annular magnet is positioned into the gap, and an adhesive is applied to adhere the magnet to the outer wall of the chamber. The pole piece is assembled using a pole piece assembly tool. The pole piece assembly tool has a head and an annular sleeve extending from the head. The annular sleeve of the tool is inserted into the chamber such that the outer surface of the annular sleeve is in contact with the magnet and the head of the device abuts the upper edge of the chamber.