Session F7: Undergraduate Research/SPS V

Making Physics Fun: The 2015 Science Outreach Catalyst Kit

The Society of Physics Students is dedicated to performing outreach events to get the general public excited about physics. The SPS National Office established the Science Outreach Catalyst Kit program in 2001 to aid SPS chapters at colleges all around the world in their efforts to bring physics education to students of all ages. Each year SPS produces twenty-five SOCKs in conjunction with the National Institute of Standards and Technology to give to SPS chapters on a first come, first serve basis. I spent my time at the SPS offices this summer helping to develop the 2015 SOCK. We designed activities that help students from elementary to high school explore basic acoustics with everyday materials like cups, straws, string, balloons, and rubber bands. In this presentation I will discuss why we chose to include the activities we did and the process of making this year’s SOCK a reality.   

Optimization of the Diode-Pumped Solid State Nd:YLF Amplifier Chain for the 263 nm Drive Laser at the FAST Facility

The RF photoinjector of the 50 MeV superconducting electron linear accelerator at the Fermilab Accelerator Science and Technology (FAST) Facility is driven by a phase-locked laser system. The neodymium-doped yttrium-lithium fluoride (Nd:YLF) seed laser provides short (3 ps) infrared (1053 nm) pulses to an amplifier chain before conversion to ultraviolet (263 nm) through two frequency-doubling BBO crystals. The amplification section consists of seven diode-pumped solid state (DPSS) amplifiers, which increase the pulse energy of the seed laser using optically end-pumped Nd:YLF crystals. To maximize the total gain of the amplifier chain, each stage must be properly tuned with optimized optics, alignment, and laser beam characterization. In this paper we report on one of the single-pass amplifier improvements to achieve a consistent gain of 4.83 with stabilized output pulse trains for up to 1500 seed pulses. The final ultraviolet pulses imaged onto the Cs$_{\mathrm{2}}$Te photocathode of the RF electron gun have been doubled in energy to 10.2 $\mu $J per pulse as a result of these alterations.   

Alpha Background Rejection in Bolometer Detectors

This study presents the modification of bolometer detectors used in particle searches to veto or otherwise reject alpha radiation background and the statistical advantages of doing so. Several techniques are presented in detail -- plastic film scintillator vetoes, metallic film ionization vetoes, and Cherenkov radiation vetoes. Plastic scintillator films are cooled to bolometer temperatures and bombarded with 1.4MeV to 6.0MeV alpha particles representative of documented detector background. Quantum dot based liquid scintillator is similarly bombarded to produce a background induced scintillation light. Photomultipliers detect this scintillation light and produce a veto signal. Layered metallic films of a primary metal, dielectric, and secondary metal, such as gold-polyethylene-gold films, are cooled to milli-kelvin temperatures and biased to produce a current signal veto when incident 1.4MeV to 6.0MeV alpha particles ionize conduction paths through the film. Calibration of veto signal to background energy is presented. These findings are extrapolated to quantify the statistical impact of such modifications to bolometer searches. Effects of these techniques on experiment duration and signal-background ratio are discussed.   

All-Optical Helicity Dependent Spin Switching in a Many-Spin System

All-optical helicity dependent magnetic switching (AOS) is achieved through using an ultrafast laser pulse to manipulate and switch the spin of an electron from one direction to another. This process happens in a short amount of femtoseconds after the laser pulse is introduced. All-optical helicity dependent magnetic switching (AOS) does not fall to the assistance of any external magnetic field. Linearly polarized light, as well as right and left circularly polarized light are used to manipulate the spin of the electrons. Ferrimagnetic, rather than ferromagnetic, materials are more suitable to create conditions in which AOS are viable due to the orientation of the spins within this material. In the following study we show and conclude that AOS is possible with the use of left and right circularly polarized laser pulses. All-optical helicity dependent magnetic switching has many applications in magnetic recording technology or magnetic memory devices.   

Rapid Adiabatic Passage in a Rb gas with intense Frequency Chirped Laser Light

We will discuss our progress toward using intense frequency chirped laser light to control the excitation of atoms in a room-temperature gas cell. We illuminate $^{87}$Rb atoms with a 1 GHz in 8 ns frequency chirped pulse of laser light covering the 5S$_{1/2}$ F$=$1 $\to $ 5P$_{3/2}$ and explore the saturation behavior as intensity increases. We estimate that we are exciting over 90{\%} of the atoms over 1 mm$^{2}$.   

Magnetic Second Harmonic Generation Imaging

Second harmonic generation is an effective probe of lattice, electronic, and magnetic symmetries of crystals where inversion symmetry is broken. In particular, magnetic second harmonic generation (MSHG) can be used to measure the magnetism induced at surfaces and interfaces of centrosymmetric materials. Imaging this MSHG signal can provide spatial information about the magnetic domains and domain boundaries that form at these interfaces. We have constructed an MSHG imaging setup using a femtosecond Ti:sapphire laser system and a highly sensitive CCD camera. Our setup can potentially be used to investigate magnetic domains and domain wall boundaries in magnetic topological insulator systems, such as EuS/Bi$_{2}$Se$_{3}$ heterostructures.   

High Q-factor Surface Plasmon-Polariton Resonance in a Plasmonic Perfect Absorber in the Terahertz Regime

Perfect absorption of light has become one of the exotic properties of plasmonic metamaterials which are popular due to the variety of feasible applications, particularly using them as a chemical/bio sensor. We present the plasmonic perfect absorber that exhibits strong surface plasmon-polariton (SPP) resonance. Due to the Fabry-Perot cavity effect, the SPP resonance is significantly sharped and the Q-factor reaches 63.1. Correspondingly, the electric field of the surface wave is largely enhanced. Furthermore, we have shown numerically that the absorption peak is independent of the incident angle. The high Q-factor and enhanced surface wave are beneficial to increase the performances of the sensor and detector devices, especially in the THz regime, where such properties are hard to achieve by natural materials.   

Figures and First Years: Examining first-year Calculus I student ability to incorporate figures into technical reports

This three-year study focused on first-year Calculus I students and their abilities to incorporate figures into technical reports. Students were handed guidelines as part of their Multidisciplinary Sustainability Education Module meant to aid them in crafting effective figures. Figure-specific questionnaires were added in the class to gain insight into the quantitative literacy skills students possessed both before starting their course and after its completion. Reviews of the figures in 78 technical reports written by 106 students showed repeated failure to refer to figures in discussion sections and use them in evidence-based arguments. Analysis of quantitative literacy skills revealed that the students could both read and interpret figures, suggesting that issues with literacy were not the main contributor to the sub-par graphs.   

Simulating Entanglement Dynamics of Singlet-Triplet Qubits Coupled to a Classical Transmission Line Resonator

Electrons confined in lateral quantum dots are promising candidates for scalable quantum bits. Particularly, singlet-triplet qubits can entangle electrostatically and offer long coherence times due to their weak interactions with the environment. However, fast two-qubit operations are challenging. We examine the dynamics of singlet triplet qubits capacitively coupled to a classical transmission line resonator driven near resonance. We numerically simulate the dynamics of the von Neumann entanglement entropy and investigate parameters of the coupling element that optimizes the operation time for the qubit.   

Simulation of weak anchoring effects on nematic liquid crystal hemispheres

The free energy of a nematic liquid crystal droplet depends on an interplay between elastic and surface interactions. When the two contributions are of similar magnitude, there exists a transition of the nematic structure of the droplet. Because the two contributions scale differently with length scales, this transition is visible as a function of the size of the droplet. We carry out numerical simulations to explore the use of this transition in measuring surface anchoring energies. This technique could help elucidate alignment forces on liquid crystals, such as those caused by rubbed surfaces, electric fields, or even the Casimir torque.