Todd C. McAlpine

In the summer 2007 NSF-REU program, Frank King and I wrote a graphical simulation of a charged spherical pendulum in a the magnetic field that is parallel to the gravitational field and the electric field perpendicular to the gravitational field. Our program was used to collect preliminary data for a range of initial polar angles and polar angular speeds both with and without fields; variations in the azimuthal angle were left to the effects of the fields. We used this data to determine divergence from initial conditions at increments of the natural period of the pendulum in order to look at sensitivity to initial conditions of the system, eventually hoping to rigorously test to see if the system is chaotic.

During the 2007 - 2008 academic year, Mark Wellons picked up this work for his Senior Independent Study Project. To start with, Mark reformulated the equations of motion because in the previous incarnation of the simulation there were some situations in which the dynamics just did not make sense. Having fixed this, Mark moved on to implement a variable time step into the simulation to allow for more efficient operation of the simulation. Additionally, Mark has developed a number of data collection routines to allow us to gather data on the dynamics of the system. This spring, we will run the simulation on the Xgrid and analyse the resulting data.

In the summer 2007 NSF-REU program, Corwin Atwood-Stone and I made strides towards the completion of a celestial clock, which is a hallway display intended to raise awareness about our dynamic place in the cosmos with respect to other celestial bodies. LabVIEW was used to create a program that tracks the positions of the Sun, the Moon, the center of the Milky Way Galaxy, and the velocity vector of the Earth with respect to the Cosmic Microwave Background in real time. LabVIEW also interfaces with the lego NXT modules, which will control the motors that run the devices. When completed, there will be three divices: one to track the Sun, another the Moon, and a third which will track both Sagittarius A* (the super-massive black hole that is the center of our galaxy) and earth's velocity vector with respect to the cosmic microwave background radiation as these two positions are at a fixed angle with respect to each other.

During the 2007 - 2008 academic year, this project is being continued by Travis Brown, a Research Assistant through the Sophomore Research Program. Travis has worked tirelessly towards complete construction of one of the devices, implementing a number of his own innovations in the operation of the celestial clock.

At the University of Kansas, I completed a full experimental characterization of an optically pumped mid-infrared semiconductor laser with a W-well active region and optical pumping injection cavity (W-OPIC) using pump wavelength tuning and resonant optical pumping. Particular emphasis was placed on the cavity length study of resonantly pumped devices. Four devices with different cavity lengths ranging from 0.312 mm to 2.030 mm were cleaved from the same region of a lapped and polished semiconductor laser wafer and subsequently characterized at seven temperatures ranging from 77 K to 325 K. Measurements were taken for each laser separately while the resonantly pumped data for all of the lasers are analyzed as a whole for the cavity length study.