Undergraduate Student Laboratory Experience

1
Undergraduate Student Laboratory Experience at
the Synchrotron Radiation Center Steven C.
Sahyun and Jeffrey M. Polak Physics Department,
University of Wisconsin - Whitewater, Whitewater,
Wisconsin 53190 Christopher J. Moore 
University of Wisconsin - Madison, Synchrotron
Radiation Center, Stoughton, Wisconsin 53589
The SRC produces electrons at highly relativistic
speeds. A preliminary accelerator injects
electrons into the Aladdin storage ring. When the
electrons undergo acceleration, a broad spectrum
of radiation is emitted by the electrons due to
the interaction of the electrons electric field
with the magnetic field from the bending magnets
in the storage ring. At the SRC, the radiation is
directed to beamlines. Research stations are set
up at the end of each beamline.
Students spent three weeks (6 lab sessions)
working with SRC data. This included an
introductory session, an initial field trip with
two weeks of remote data collection, and a final
poster presentation at the SRC where students
presented their posters to SRC staff members.
Students chose which sample items to research and
what to present in their posters.
Abstract We describe the structure of an
intermediate physics laboratory course, a
significant component of which is dedicated to
having students perform three weeks of hands-on
experiments and real-time data collection at the
Synchrotron Radiation Center national laboratory
operated by the University of Wisconsin -
Madison. We comment on student feedback on how
this experience affected their attitudes and
expectations of physics.
Course Overview
To provide a conceptual context for the
experiments at the SRC as well as to make the
best use of the limited research beam time, four
preliminary laboratories modules were performed
to acquaint the students with the concepts,
techniques, and equipment that are used at the
SRC. These included the motion of of electrons in
magnetic fields, data acquisition, computer
control of equipment using LabVIEW, and analysis
of spectral graphs. Students worked in pairs for
two weeks at each station (8 hours total).
Students submitted typed reports for each lab
station.
To assess the changes in student attitudes about
physics, the students were given the Maryland
Physics Expectation (MPEX) survey. Although
positive changes leading to better alignment with
expert views on questions in the independence,
coherence, and concept clusters were seen, due to
the small sample size, these effects were not
statistically significant for the 11 students
surveyed.
The SPECTRA beamline allows students to perform
photoemission experiments where soft x-ray
wavelengths are directed onto a photodiode. The
photodiode was gold for the 2004 group of
students, but apparatus upgrades allowed the 2006
group to use a variety of photodiode materials.
The light on the diode liberates electrons that
are collected by an anode. The measured values of
the associated current as the light is scanned
through the desired range of wavelengths and data
are stored on the SPECTRA Web server for students
to download. One of several sample filters (for
example, aluminum, boron, beryllium, or titanium)
can be inserted into the beam path just before
the detector for analysis.

• Lab Station 1Electron properties.
• Helmholtz coil field mapping.
• e/m ratio
• Millikan Oil Drop

Lab Station 2 Magnetism Magnetic dipole moment
and torque experiments and a brief introduction
to vacuum systems.
Lab Station 3 Computer Interfacing. Using a
digital storage oscilloscope, RC circuit, and
LabVIEW interface to send and receive data.

• Lab Station 4Material Properties.
• Analysis of Alpha/Proton X-ray Spectra (APXS)
  from the Mars Spirit and Opportunity rovers.
• Scanning Tunneling Microscope.

SRC Experience
SRC EXPERIMENT AND PRESENTATION The SRC is
funded by the National Science Foundation and is
operated by the Graduate School of the University
of Wisconsin - Madison. The facility consists of
an electron accelerator and the Aladdin storage
ring, and produces intense, broad-spectrum
electromagnetic radiation from infrared to x-ray
frequencies. This radiation is used for a wide
array of materials research and applications
including nanotechnology, geology, and
environmental science.
On the last day of the course the students were
also given a questionnaire on how the SRC
experience affected the course and their future
plans. It was found that the students agreed with
statements about the SRC being an enjoyable and
challenging experience. They also agreed that the
SRC provided a better context of real physics
research than experiments performed in the
classroom. Students noted that the SRC experience
did not alter their career goals and most of the
students were not interested in working in a
laboratory of this type as a career choice.
The samples absorb some of the incident x-ray
light when the photon energy exceeds the binding
energy for the samples K-shell (for B and Be) or
L-shell (for Al and Ti) electrons, thus altering
the detected signal. Dividing the samples
current signal by the initial detector current
signal eliminates most of the detector diode and
other beamline effects.
CONCLUSION The SRC experience is a unique
opportunity for students to learn about physics
using the facilities at a national laboratory and
students are able to see one type of research
career path at an early stage in their
educational experience. The students that have
used the facility have shown an interest in the
experience and have produced quality posters
presentations to the SRC staff. Students
generally found the SRC laboratory a valuable
experience and the most worthwhile part of the
course. The modular design of the background labs
allowed students to perform laboratory
experiments with a limited number of experimental
setups. An added benefit was that students were
able to seek peer instruction in order to perform
the experiments. The use of the lab stations was
helpful as preparation for the visit to the SRC
and it reinforced self-reliance and the need for
teamwork rather than relying on the instructor to
provide detailed instruction and hand-holding in
order to complete the lab.
The students imported their data into a
spreadsheet, calibrated the tabular data sets,
converted the data to equivalent photon energies,
and divided the sample filter data by the
detector data to remove effects of the beamline
and the detector on the recorded signal.
A plot of the derivative allows students to
clearly see peaks at specific energies related to
the subtle changes in the absorption of the
light due to resonances at the samples K or
L-shell energies.
A research station at the SRC, called Students
Performing Experiments Collaboratively Thorough
Remote Access (SPECTRA), is dedicated to outreach
programs. This research station enables students
to conduct local or remote experiments and
collect real-time data using a Web interface. The
manageable size of the SRC allows students to
experience physics experiments not available in
the traditional course or laboratory setting.
For more information about the SRC SPECTRA
program contact the SRC Educational Outreach
Coordinator Chris Moore cmoore_at_src.wisc.edu (608)
877-2137 For information about the
undergraduate laboratory contact Steven Sahyun -
sahyuns_at_uww.edu
Here, the 112 eV K-shell binding energy for
beryllium, as well as small peaks for carbon (284
eV) and oxygen (537 eV) can be seen.
The experiments conducted at the Synchrotron
Radiation Center, University of
Wisconsin-Madison, is supported by the NSF Award
No. DMR-0084402.