The third year laboratories

Figure 1: Work experience student Michael Schoenhammer operating the vacuum apparatus.

The Laboratory's suite of experiments in fundamental physics has been augmented by a state-of-the-art experiment aimed at training students in vacuum science as a technological tool in experimental physics.

THE THIRD YEAR laboratory represents the final opportunity for many physics students to do "real" physics in the form of experiments, using sophisticated equipment that allows the confirmation of the tenets which form the foundations of our understanding of modern physics. Students with career paths in teaching and engineering have this last opportunity to use recently introduced computer assisted experiments to study, for example, Fourier optics, scanning tunnelling microscopy or magnetic resonance imaging (MRI).

In some of these experiments the equipment itself represents a statement about our modern scientific technology; an experiment covering the topic of vacuum science and technology has been developed over the 1999/2000 recess. Some cynical observers consider vacuum science to be "a lot of noise about nothing", while others never do understand why vacuum pumping seems to take so long, but vacuum techniques are vital in the manufacture of electronic semiconductors, CDs and many foods. The vacuum project involved the third year laboratory staff as well as Martin Schoenhammer, a student, with a career path in computer/electronic equipment design, from the Fachhochschule Regensburg, Germany, and taking part in the regular work experience program organised within the School of Physics.

The criteria for the vacuum experiment included:

• the use of modern vacuum equipment: rotary and turbo-molecular pumps (reality has displaced sentimentality, and the days of the mysterious diffusion pump are numbered)

• that vacuum measurements be computerised and displayed in real time on a continuous graphical basis as part of a computer program (Visual Basic) which also allows interactive calculation of linear and exponential curve fitting (see Fig. 2)
• student participation in the building and modification of vacuum systems using industry standard components (KF couplings)

• student participation in operating the assembled components as a functioning vacuum system.

The pedagogical approach is to allow students to gain "hands-on" experience in the building and control of vacuum equipment while the computer, in real time, acquires, displays and records gas pressure data. The individual assessment of learning outcomes focuses on a student's understanding of the performance of the equipment, demonstrating a scientific interpretation of the collected data in the context of their knowledge of physics.

It is the intention of the laboratory to provide experiments that are relevant to the topics of modern physics taught in lecture courses, and to teach professional methods of practice in the experimental investigation of physical phenomena.

Patrick McMillan &
Barry Perczuk

Figure 2: The vacuum pressure (linear and log) time plots for a chamber showing: a rotary pump evacuation of the chamber (left), an air "leak" (calibrated) into the chamber (right).