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In a number of labs over the past number of years, we use dedicated or embedded processors. A number of these processors are expensive and hard to program. This year, we have continued the transition to the cheap and very capable Raspberry Pi universe. The Pi Pico is a $4 processor that can be used in our digital logic labs (in place of the Xilinx FPGAs) and for a stepper motor controller (in place of the National Instruments DAQ boards). We designed a simple shield shown at the right in the above picture to connect switches and LEDs to the Pico. These elements are used to test a digital logic circuit in Experimental Physics lab.
The last lab of the quarter in Principles of Physics covers Kepler's Laws. In the last few weeks, we purchased a Gravity Well (stretchy material over a PVC frame with a large mass in the center). By watching a marble orbit a heavy ball in the center, the second law can be tested. The picture below shows data from our most recent lab. Accounting for friction, our data suggests that the second law appears to be correct.
In Modern Physics lab this year, we added a pulsed NMR (nuclear magnetic resonance) machine to our lab. In previous years, we have just used our earth-field NMR to study long relaxation-time materials such as water, ketchup, and butter. Using the pNMR machine allowed us to study mineral oil which has a relaxation time that is 100 times shorter than that of water. The picture at the right uses about 20 B-pulses to get the spin-spin relaxation time of mineral oil.
The pNMR machine is also a bit easier to use since its power requirements are more modest and its stray magnetic field tolerances are better.
Near the end of October, the WWU Physics Department was privileged to have one of our graduates, Spencer, come back to campus and give a talk on his PhD research. He is working on twisted graphene layers and some of the data he presented was only 48 hours old. While his talk had some technical aspects, the combination of cool science, humor (the word "twisted" got used and misused), and a small bit of movie trivia kept the audience engaged.
Back in May, our new Scanning Electron Microscope was introduced. This month, we used it for the first official lab exercises. In Modern Physics lab this week, we used several ways of changing the image including accelerating voltage and detector type. The students looked at several samples including a DVD, fruit fly, and EPROM chip. In the picture below, the DVD is imaged using the the backscattered electrons on the left, secondary electrons on the middle and right using two different positions of the detector.
While cleaning out an old storeroom, an old schematic of Kretschmar Hall was found as shown in the picture above. There was no date on it but it appears to pre-date the third story and engineering extension which would make it earlier than 1985. Any alumni with a better guess on the date, please email Dr. Ekkens.
This summer we have been developing several new projects to use for science camps with grade school students. One of the projects is to look at types of crystals found around an average house: salt, sugar, and sand (in dirty houses). The picture below is how the salt, sugar, and sand look through an optical microscope magnified 80 times. For camps away from the department, the optical microscopes are easy to move. For camps at the university, the crystals can also be imaged at much higher magnification using one of our scanning electron microscopes.
As normal during the summer, the Physics Department hosted a session for the summer science camp for children in fifth to eighth grades. This age is more interested in doing than learning so many of the activities are selected to be fun while sneaking a bit of learning in on the side. Frequently, the campers come up with their own experiments.
In the picture at the right, a summer camper wanted an IR picture taken while he touched the van der Graaf generator to charge himself up. He was rather sad that in the picture he looked the same as he did when the van der Graaf generator wasn't running.
This spring we purchased a second laser engraver. This xTool semiconductor blue laser (465nm) joins the CO2 gas IR laser (10,600nm) in our shop and adds the ability to cut thin metal which the IR laser doesn't have. It also can mark silicon wafers so the plan is to integrate it into the Physical Electronics lab.
Over the past five years, we have boosted our shop capacity with a number of these new tools. Each one of these computer run tools - both laser engravers, two filament 3d printers, and one resin 3d printer - has their own niche that they fill in our lab classes and equipment building. However, if we had to select just one tool for everything, the large filament 3d printer is still the most useful.
On the evening of May 24, we opened the observatory to see the moon, Venus, M13, and the newest supernova on the block (2023ixf). This supernova was discovered on May 19 in the Pinwheel Galaxy M101. Our new 4.5" telescope was used to take the pictures of M101 before and after the supernova explosion. Note that our telescope uses universal time so the time stamps are ahead one day from the observation time for pictures taken before midnight. We didn't get the best focus on the telescope but the supernova is so bright it doesn't matter.
In the KRH observatory, we have a 16" Meade telescope mounted on a pedestal in the dome. It has a camera that can connect to it. However, most visitors to the observatory want to look through the telescope rather than watch a monitor so we leave the camera off. This means in our high-light location, we don't get the advantage of image stacking so nebula and galaxies are very dim.
This May, the solution has been to buy a 4.5" digital telescope - the eVscope 2 from Unistellar. This scope has the camera and processing built into it which makes it very easy to use. The image is sent to a viewport on the side of the scope and wirelessly to a tablet. In the picture at the right, the 16" is on the left and the 4.5" is on the right. For normal operation, the 4.5" is placed outside on the roof. Head on over to our observatory page to see pictures from it.
For the last 14 years, we have been using a Scanning Electron Microscope (SEM) that uses secondary electrons for producing the image. That SEM as been ideal for the student labs because it is cheap to maintain and robust in operation. This past summer, we were able to find a used SEM that uses backscattered electrons to produce the image. This SEM is more expensive to maintain but produces a different type of image which is useful for a number of labs. In the image, a fruit fly's eye is shown magnified by 4000 times. The left half of the image is taken using the secondary electrons and the whiskers are very bright. The right half of the image is taken using the backscattered electrons and the surface of the gold coating over the eye is more more detailed.
The winter weather along with its clouds and rain left the valley near the end of April. With the return of clear skies, the observatory resumed operations. We had two observations during last week of April with around 150 people enjoying views of the moon, Venus, Mars, and M13. The weather was absolutely perfect with clear skies and warm temperatures.
The picture at right, taken by Debbie Muthersbaugh, shows the dome with the moon and Venus visible above it. While the moon gets in the way of seeing dim objects, the craters on it are interesting to the younger viewers.
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.
Optics lab is still going strong. One of our labs studied the colors present in white light. In the picture at the right, white light from two sources is compared. The top band is from an incandescent light bulb and the bottom band is from a white LED. At the very bottom of the picture is the scale in nanometers that is almost too small to read. Our eyes detect light from about 400 nm to about 700 nm - almost the exact range of the LED. The incandescent light has a lot of light produced in the range of 750 nm to 1000 nm - mostly heat energy.
Winter quarter has started and the optics lab is underway. Mounting hardware for the optics breadboard is usually made of aluminum or steel so it is heavy and rigid. Unfortunately it is also expensive. This quarter, we have started making a number of smaller pieces on the 3d printer. The plastic parts are quick to produce but don't work every situation. Here are two of the ones that worked.
In the picture above at left, a plastic piece sits between the metal rod and the metal mirror assembly. It offsets the mirror so it is directly over the rod. In the picture above at right, a piezo is held in place by a plastic clamp. The clamp attaches to a metal lens holder. Both these pieces allow us to spend less time setting up experiments and more time doing the experiment.
With great sadness we mark the passing of Martin Scott who was killed today in a traffic accident.
Marty has been a part of the Physics Department for many years. He taught Astronomy to hundreds of Walla Walla University students for more than twenty years. When the Kretschmar Hall observatory was completed in 1999, Marty was its first daily administrator. While teaching astronomy and running the observatory, he completed a Masters Degree in Astronomy. He then became the "astronomy guy" to the entire Walla Walla valley contributing to astronomy programs in all three colleges, the local newspaper, and a host of smaller projects.
A student was looking for Marty some time ago and couldn't remember his name. The student came into my office and asked "Where is the professor that looks like Santa Claus and knows about stars?" As I think back over the ways Martin Scott has touched our lives over the years, I will always remember him as the "Santa Claus who knows about stars."
Tom Ekkens, Chair of Physics, Walla Walla University
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.
With the vibration damping improvement from the tuned mass damper and the clear skies provided by a late summer drought, this has been our best quarter for viewing ever. Jupiter was at its closest approach in decades and Saturn was also in a prime viewing location. We got in the following groups before the fall rains started:
September 15, Faculty and staff. M13, Jupiter, and Saturn.
October 1, Students in Conceptual Physics, General Physics, and Principles of Physics. Jupiter, Saturn, M13, M31, and the moon.
October 12, All of WWU as announced in the 11am daily email. Again Jupiter, Saturn, M13, M31, and the moon.
October 22, Parents Weekend. Jupiter, Saturn, and M13. The clouds came up during the viewing so the season is over now.
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.
Summer is also the time when new experiments are developed and new equipment is built. This summer Dr. Ekkens has been working on incorporting Raspberry Pi boards into several experiments. In the picture is the Pico board. This $4 board has a fast processor and several analog inputs which make it a good fit for a collecting data and controlling hardware. Students in General Physics this coming year will use it for at least one lab.
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.
The summer is underway with lots of activities. Dr. Campbell is teaching General Physics in the highly compressed summer option. Cramming three quarters of material into the summer doesn't leave students much time for anything else. Dr. Ekkens hosted a section of science camp where area school children learned about sound and light. Everyone - even the camp staff - enjoyed taking thermal imaging pictures of themselves. The Tesla coil was also a noisy hit.
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.
This graduation will go down in memory as the time we almost got washed out. During the service, we had only a few rain showers come through. Later in the afternoon the rain really arrived and we got 1 inch of rain in about 12 hours. The picture shown at the right is during the ceremony just before the first drops of rain fell. In the physics department we had one major graduate this year.
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.
We are just finishing up an upgrade to our oscilloscopes used in the General Physics and Principles of Physics laboratories. These new oscilloscopes replace the older passive matrix displays so they are much brighter. This upgrade also moves us from generic parts to name brand parts so the reliability of the equipment is better and the noise is lower.
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."
This year we got better pictures of carbon nanotubes that we ever have before using our PVC STMs. The picture at the right shows at least three tubes across the image from the lower left corner to the upper right corner. The diameter of the smaller tubes is about 5 nm or 1000 times smaller than a red blood cell. Best resolution on the STM appears to be 2 nm.
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.