Hints on Data Interpretation

When interpreting data of any kind, one simply asks the question: "What does this data mean, within the contexts of the objective of my experiment".

In this experiment, we wanted to determine the pattern and rate of decay of the magnetic field of strontium ferrite magnetized bricks. Why was this important? This is important, because without this information, it would be impossible to know when the magnetic field would become too weak to contain the anti-proton beam. Armed with this knowledge, scientists won't simply wait until the beam is lost for the first time. Rather, since they can predict the time when it will be too weak to do the job, they can schedule that time for maintenance, and replacement of the magnets, rather than scheduling the run of a critical experiment! It is kind of like when your teacher asks the other teachers in advance of upcoming field trips that will involve every member of their class. Rather than scheduling an important test or lab for that day, the teacher without students might schedule a "maintenance day" of review for the few remaining students. If the teacher is unable to predict this in advance, they can get quite aggitated, and pummel the offending teacher who took away their students on a field trip......just like if we cannot predict brick failure, a Fermilab researcher may one day become aggitated (even..violently aggitated) when their experiment fails because the magnets on the Recycler Ring lost strength, and will require several months of replacement and maintenance, before the experiment may resume!

In the context of this experiment, it is important to decide what shape the curve of Time vs. Average Voltage Change takes on a semi-log plot. (Remember.....we couldn't accurately measure the magnetic field, so we measured a voltage change that was brought about by a moving coil of wire in a magnetic field......The magnetic field strength and Voltage Change are proportional). If you aren't sure, check a text book. Is it a linear relationship? Exponential? Logarithmic? Inverse?

Next, we must decide if this curve means we can go on with the project. Each magnet has 272 bricks in it, and the whole ring will be about 400 magnets. The Fermilab personnel will not be happy if the magnets need to get new bricks every year. These bricks must hold their strength for a long time. If the graph of Time vs. Avg. Voltage Change shows that the Average Voltage Change will be large, or increase as time goes on, this entire project should be shut down immediately. However, if the Average Voltage Change is small, or becomes small over time, this project should work. If you come up with a linear graph, find the slope of the graph. If the graph is logarithmic, find the slope of the line after the first 100 minutes of magnetization. The slopes of these lines must be quite small (on the order of 10-7 or 10-8 ). If the slope is much larger than that, the magnets will lose their field too rapidly for this project to be economically feasible.

If you are doing a write up of some kind, make certain that you make statements about these important points in your Concluding Statements.

Author:
Thomas Egan of Marist High School, Chicago, IL. This project was constructed as part of the Teachers Research Associate (TRAC) Program from the Fermi National Accelerator Laboratory in Batavia, IL. This project is also in conjunction with Aurora University, Aurora, IL.
Produced on: August 7, 1996