FORUM ON EDUCATION
Spring 2003

Road Show Demonstrations for a Research Laboratory

Motivation for the project[1]

MAX-lab[2] is a synchrotron facility located at Lund University, Lund Sweden. The community of scientists using the laboratory comes from around the world, representing chemistry, physics, life sciences and several fields of engineering. The laboratory provides beam lines designed for focusing infrared to X-Ray light that is produced by relativistic electrons moving in three different rings. Experimental stations include an ultraviolet light for photoemission measurements of new types of semiconductors, a beam line for x-ray crystallography heavily subscribed by pharmaceutical and life sciences, an x-ray lithography and micromachining area, and there is also a soft x-ray photoelectron microscope including several instruments for soft x-ray spectroscopy of surfaces, to name a few.

The average visitor to the synchrotron sees an accelerator hidden behind a shielding wall with an enormous number of pipes and cables fed into it. The experiments all look the same, and the high-tech x-ray optics are sealed inside stainless steel vacuum chambers pumped by noisy vacuum pumps. The laboratory itself is not a particularly inspiring environment for anybody except perhaps the involved researchers.

The goal of this project is to give the outside visitor a better picture of the science at the synchrotron radiation source and to emphasize the enormous number of different research projects at the lab. The visitors we are targeting include high-school students, undergraduate physics students, graduate students from many disciplines, funding agencies, politicians, and physics teachers. We also hope to pique the interest of students and teachers to recruit scientists for the future. The result is an interactive science area focusing on the fundamental properties of different wavelengths of light and their interaction with matter. The developed demonstrations show the fundamental physical phenomena that are the basis for both the electron-beam technology and also the research performed at the lab.

Development of the Demonstrations for MAX-Lab

We didn’t want the demonstrations to become a bunch of technology with a plethora of connections that overwhelm the visitor with little impact on their impression of the synchrotron light facilities. The displays are made up of more common materials to create an uncomplicated way to observe the physics utilizing more recognizable apparatus. The demonstrations are listed below:

• Electromagnetic Radiation from Accelerating Charges
• Interaction of light with matter: Detectors
• Interaction of light with matter: Absorption & transmission
• Lithography using absorption of UV radiation
• Electron beam deflection
• Magnetic fields and properties: Ferrofluid
• Vacuum systems using a Hittorf Tube
• Principles of X-Ray crystallography using a HeNe laser and special slides (under development)

The interactive science area is set-up in the library at the laboratory. Each set-up has a short description of the science displayed by the demonstration. There is also a set of instructions on how to perform the demonstration and suggestions on what to observe. The demonstrations are flexible and can be used to illustrate both the principle of the laboratory research project and a basic physical phenomenon. Staff and researchers also find a new way to look at concepts through the demonstrations.

Below are short descriptions of some of the experiments to show the principle idea behind the display I designed and put together during a sabbatical leave from The University of Oregon.

Electromagnetic Radiation and Accelerating Charges

The connection between accelerating charges and electromagnetic (EM) radiation is displayed by using a visual source of electrical charges, a plasma tube. Plasma tubes have become popular and are commonly seen in movies, science museum stores and novelty shops. They come in various shapes and forms and have become relatively inexpensive. The colorful bottled lightning easily attracts attention and can be used for a number of physics demonstrations. Here, the accelerated charges produce electromagnetic radiation in the radio frequency range and the radiation noise produced can be picked up by an AM radio placed a few meters from the tube. One can make a visible connection that the accelerating charges actually produce EM picked up by our detector, the AM radio. We also have available items so observers can explore shielding and properties of matter using this display.

Interaction of light with matter: Detectors

Most of the EM radiation produced at MAX-Lab is outside of the visible part of the EM spectrum so detectors are needed to monitor radiation that the senses cannot perceive. The set-up has two examples of detectors that are sensitive to radiation wavelengths that we cannot see but safe enough for demonstration use. The first is a set of beads[3] that change color while exposed to ultraviolet radiation (UV). The nice thing about these beads is that they change back to white after a short period of time once the UV source is removed. They can be used repeatedly to detect UV radiation. The UV source we used is a “Black Light”, a source of safe low energy UV radiation great for demonstration purposes.

The second detector is a charge-coupled device (CCD) video camera. A standard CCD camera responds well to infrared radiation (IR) as well as to the visible light that we see. We employ TV and VCR IR remote controls as a source of safe IR to illustrate how the CCD detector can ‘see’ what our eyes cannot. The CCD camera is especially illustrative since it can be shown in real time on a television monitor. We instruct the observers to point the IR remote control at the camera where they are able to clearly see pulses of IR light coming from the IR diode on the remote control unit.

We also use these safe light sources and detectors to observe the characteristic absorption and transmission properties of different materials, the interaction of light and matter. These are examples of using common materials to display the physics behind the technology and research performed in the research laboratory. Under development is an apparatus to show the principles of X-Ray crystallography utilizing a laser as the source of light and a microscope objective lens as the Fourier analyzer.

Controlling the Electron Beam

The electrons travel in an evacuated environment and are controlled with magnetic fields. The beam radiation is also enhanced with oscillating magnetic fields interacting with the electrons as they travel. To give some basics demonstrations of how the laboratory machine works we used commercial apparatus; an electron beam apparatus to show the steering of an electron beam, a Ferrofluid cell[4], which contains a stable colloidal suspension of nano sized (10^-8 m) magnetic particles in a liquid carrier, to show matter interacting with a magnetic field, and a Hittorf Tube[5] to demonstrate some phenomena regarding vacuum systems.

Summary

We have developed hands-on demonstrations where the principles of light interacting with matter are described in several different ways for different wavelengths of light. Infra red light is detected using a CCD camera and several different cases are used to show how this light interacts with plastics and dyes. The fact that all light is created by accelerated electrons is exemplified in the plasma sculpture; and also by the RF noise picked up on an AM radio. We have demonstrated the principle of lithography using an array of UV-sensitive beads and a poly carbonite mask, and in the future, a visual demonstration of x-ray crystallography using visible laser light.

Acknowledgments

I am grateful to my host Stacey Sorensen who envisioned and coordinated the project. Machinist Gustav Ekberg, who built the supports for many of the demonstrations. We are also thankful for suggestions and ideas from the MAX-Lab staff. Support from MAX-Lab, the Foundation for Strategic Research (SSF) and the Swedish Research Council (VR) is also acknowledged. Pasco Scientific, Kebo Scientific, Per-Olaf Zetterberg and Vernier Software for loaning of equipment during the development of the project, along with Brian Jones at Colorado State University for his inspiration along with the members of PIRA, Physics Instructional Resource Association, for the constant dialog and exchanging of ideas are also greatly appreciated.

For more information, contact:

Stanley Micklavzina
Department of Physics
University of Oregon
Eugene Oregon 97403-1274
541-346-4801 (office)
541-346-4757 (Demonstration Room)
stanm@hendrix.uoregon.edu