There are other things going on in the department but this quarter Optics Lab is making the news since optics has pretty colors and new experiments.  As one part of the final optics lab, we tried to build a TEA (Transversely Excited Atmospheric) laser based on the designs shown in several Youtube videos.  We did not get it to work during the lab time period.

However, several of us worked on it a bit more after lab and by the second day of spring break, the laser was working well.  A picture of the laser firing is shown at the left.  The arcs between the two rods are seen nearly the length of the rods.  The very bright arc at the lower right suggests that the rods could be aligned a bit better.  The laser beam is invisible (UV) but we can see it as the green/yellow light in the Rhodamine B dye in the upper left of the picture.  We could make a dye laser using this design.

Fall is here but leaves aren't the only thing falling to the ground.  Projectiles are launching into the crisp fall air and falling back to earth as part of labs in all of the introduction classes.  In the picture at left framed by colorful trees, the Conceptual Physics Lab students are launching rocket-shaped projectiles and measuring their range as a function of angle.

As mentioned back in December of 2021, the telescope is mounted on a metal pier that reaches down through the third story of Kretschmar and shakes like a leaf in the wind.  The December vibration reduction update added air legs between the pier and the telescope.  It did reduce vibration a bit but added tracking problems.  During the past two months, the air legs were removed from the system and a tuned mass damper (TMD) was added.  As shown in the picture, the TMD is mounted near the top of the pier and is made of 6 lead bricks floating on sorbothane.  The major vibration peaks at 6 and 10 Hz have a reduction of about 5 dB in each axis.

During the summer between the junior and senior year, we strongly encourage the physics majors to participate in a Research Experience for Undergrads (REU).  A number of universities and labs participate in the program so most majors are able to enjoy this learning opportunity.  This summer we have one major and one minor doing research at different universities.  In addition to research, students and faculty are able to participate in conferences.  Both Dr. Campbell and Dr. Ekkens are attending conferences this summer.  As COVID restrictions continue to wane some conferences now have in-person options.

Raman Spectroscopy is a topic that we cover very heavily in Nanotechnology (and a bit in optics).  We have two older Raman spectrometers that we have been using for lab but we really have needed a third one based on the number of students in lab.  This year we bought one that is quite different from the two we already have.  It is green (532nm) instead of IR (985 nm) and it is sold as a number of discrete components instead of a single box.  Fortunately, a plastic file folder box is about the right size and we were able to zip-tie the components in place as shown in the picture at the left.  It will be interesting over the next few years of labs to see which wavelength works the best with our carbon nanotube samples.

The quarter of Physical Electronics lab is coming to an end.  We have made a lot of devices in lab this quarter - pn junctions, SBDs, Hall probes, and two types of transistors.  Most of them worked, but the prettiest of them all was a solar cell.  The picture shows a 2 mm view of the cell without any changes to the color.  The surface of the cell is totally dry but looks like oil on water.

The quarter of Nanotechnology is finishing up this month.  Our next-to-last lab covers magnetism so we looked at the unique shapes we could make in the fluid with magnets - both permanent and electro.  This year we set a local record from the amount of mess made with ferrofluid.  This picture was taken a few minutes before "the event."

It is once again Winter quarter so the PVC scanning tunneling microscopes are being built by the Nanotechnology class.  New for this year is a better holder for the borescope and a new power supply for the amplifiers.  The power supply is shown in the picture at the left.  It is based off a bipolar kit from Jameco and is housed in a 3d-printed box.  The new power supply replaces four 9-volt batteries for the amplifiers and a small 12-volt supply for the motor.  So far there doesn't seem to be difference in performance between the power supplies apart from ease of use.

This quarter, our upper division physics majors are taking Experimental Physics.  We are spending time learning to program data acquisition boards.  For the lab this week, we built a circuit from a function generator, inductor, and diode.  The circuit exhibits chaotic behavior so we used our programming skills to collect the voltage across the diode as a function of drive voltage.  The resulting logistic map at the right shows the pitchfork bifurcations typical of chaotic systems.  We were able to compute Feigenbaum's number from this graph with fairly good accuracy.  Taking this data by hand would have taken forever but using the computer, the picture was constructed in about 5 minutes.  

September 27:  Classes are starting today and we are back to in-person classes and labs.  Just before the first physics class of the quarter, this rainbow was visible over our observatory.  In addition to the rainbow, this should be an exciting year in physics and astronomy.  The world is awaiting the launch of the James Webb Space Telescope on December 18.  This telescope will have almost 10 times more collecting area than Hubble and more than 250 times the collecting area of our 16" telescope mounted in the silver dome on the roof of Kretschmar Hall.

Summer is the time that we buy new equipment and test it out.  This summer we are upgrading our Zeeman Effect experiment.  The initial hardware was put together by Calvin, a physics major several years ago, from spare parts.  This summer we bought the dedicated system from Pasco shown in the inset of the picture.  In the last few weeks, testing on it has been completed and it will be used in the Modern Physics Lab this coming fall.  The split lines, shown in the picture, are from the unpolarized light.

After the previous viewing in April, a new telescope camera was purchased.  The previous camera was about 20 years old, connected to a computer using a parallel part, and was water-cooled.  This new camera is USB 3.0 and is air cooled so it is much easier to use.  The first images taken with the new camera were of the moon.  While the telescope mount lets too much vibration through, several good pictures were obtained.

This month, we finished up the optics labs for the quarter.  One of the improvements this time was in measuring the sodium doublet.  Sodium emits light in two wavelengths that are close together (called the doublet).  There are several methods to measure the difference in the two wavelengths but some of them require more complicated tooling or are difficult to set up.  The picture shows our method for using an interferometer to measure the difference in wavelengths.  The improvement was to level the system using a laser shown by the red line and then rotate only a single mirror to the sodium light shown by the yellow line.  This geometry made setting up the experiment much easier.

The physics department is back in session with 50% of the classes taught in person this quarter.  As seen in the picture of our optics lab, we are wearing masks and face shields, but we are once again doing the lab experiments that make our graduates stand out of the crowd.  During the last two COVID-19 quarters, we covered all the labs by video but it just isn't the same as being there.

In Modern Physics, we talk about how the Braggs used x-rays to determine crystal structure.  In lab, we don't use x-rays because of radiation damage.  Instead we duplicate the classic experiment using low-power microwaves with "crystals" made of ball bearings.  Usually we hold the bearings in position using foam as seen in the picture on the right.  This year (after the lab was completed using foam holders), we started building up ball bearing holders using plastic.  The plastic does mess up the microwaves a bit, but it allows us to change the crystal size really fast.  The crystal on the left has holes cut for bearing spacings of 3, 3.5, 4, and 4.5 cm.  A laser engraver was used to make the pieces.  In time for next year's lab, we will have a number of these sets made.

School is back in session for the 2020-2021 year.  Because covid-19 is still with us, many of the sophomore and junior classes are remote.  General Physics and Principles of Physics are on-line so the labs are mostly done by watching videos of the experiments.  In the picture at the left, we are measuring the height of Kretschmar Hall by dropping a golf ball from the top and measuring its time of flight.  One advantage of the video lab is that the camera is much more accurate with timing than a human using a stopwatch.

This summer the Physics Department gratefully received a donation from the Fluke Corporation.  The multimeters and thermocouple therometers will be used in the large introductory labs such as General Physics and Principles of Physics.  The Fluke Corporation routinely makes such donations to colleges in the Northwest.  Thank you.

This quarter, Walla Walla University like nearly all other schools is meeting on-line only.  Our labs are on-line as well.  This means the experiment is recorded and the students watch the video and collect data from the video.  In the picture at left, a screen capture from a Principles of Physics lab is shown.  A stream of electrons is hitting some helium gas and making the greenish glow.  From the measured parameters, we can compute the ratio of the electron charge to the electron mass.

The interesting thing is that using cameras to collect data in many situations gives better results than the data collected by eye only.  Some labs are being rewritten to suggest that the data be collected by cameras always.

The new quarter has started and Introduction to Nanotechnology is underway.  The first two labs of the quarter are spent building a scanning tunneling microscope.  As shown in the picture PVC and hot glue play a role in the construction.  Four lab groups are each building up their own microscope.  The detailed build directions from the 2014 article are available at https://www.wallawalla.edu/academics/areas-of-study/physics/faculty/ekkens-research/studentstm/ .  Over the last six years, we have made several changes in the design to make use of our 3d printers.  An update to the build directions should be finished by this summer.