The Recycler Project
Magnetic Field Loss With Age
Background: Over time, materials which are magnetized, lose their magnetic properties (under most circumstances, these materials may be re-magnetized). The strontium ferrite ceramic bricks that are being used in the Recycler Project will also, over time, lose their magnetic properties, and their ability to contain the antiproton beam. In this experiment, an attempt will be made to determine the rate at which the magnetic field strength is lost.
A flip coil apparatus is a way to measure field strength. A coil of wire is placed between the magnetic bricks. The baseline voltage is recorded. The coil is then rotated (flipped) 180°counterclockwise. As the coil moves in the magnetic field, an electric current is induced, which results in a voltage change (according to Ohm's Law, the amount of current flowing through a conductor will change if the voltage changes, and the resistance stays the same).The new voltage is recorded. The coil is then flipped back to its starting orientation, and the third voltage (which should resemble the baseline voltage). Is recorded. The two differences are computed (baseline to new voltage, and new voltage back to baseline), and averaged. Because magnetic properties can change with temperature, an insulating blanket of fiberglass surrounded the entire apparatus. The temperature never fluctuated more than three degrees during the experiment.
Materials: Four, 4x6x1, strontium ferrite ceramic bricks (manufactured by Hitachi), Lambertson electromagnet, wire coil, attached to rotating apparatus (see diagram), DC voltmeter, digital integrator, digital clock, digital thermocouple, insulating blanket (for a picture of the flipcoil apparatus, see the photo gallery).
Procedure: The flip coil apparatus was attached to the integrator, which in turn was connected to the DC voltmeter. The integrator had the job of allowing consistent reset of the voltmeter, to allow for consistent measurements over the weeks.
Four 4x6x1 strontium ferrite ceramic bricks, manufactured by Hitachi, were magnetized by a Lambertson electromagnet. The bricks were installed into the flip coil apparatus. The integrator was reset, and measurements of the voltage were taken every 10 seconds for 50 seconds. At the time of one elapsed minute, the coil was rotated 180°. A second set of voltage recordings were taken every 10 seconds, for 50 seconds. At the passing of the second elapsed minute, the coil was rotated back to its original position. A third set of voltage readings were taken every 10 seconds, for 50 seconds.
An average was taken for the voltage change caused by the clockwise rotation of the flipcoil, and a second average was made of the change caused by the counterclockwise rotation of the flipcoil. Finally, these two averages were averaged to determine an average voltage change at that time.
You can try to follow in our footsteps by analyzing the data that we collected, and then trying to interpret what it means.
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