Session C5: Undergraduate Research - SPS II

Experiments with Electrodynamic Wheels

Our experiments were involving inductive magnetic levitation. A Halbach array is a system in which a series of magnets is arranged in a manner such that the magnetic field is cancelled on one side of the array while strengthening the field on the other. We constructed two circular Halbach wheels, making the strong magnetic field on the outer rim of the ring. Such system is usually dubbed as an Electrodynamic Wheel (EDW). Rotating this wheel around a horizontal axis above a flat conducting surface should induce eddy currents in said surface through the variable magnetic flux. The eddy currents produce, in turn, their own magnetic fields which interact with the magnets of the EDW. We demonstrated that these interactions produce both drag and lift forces on the EDW which can theoretically be used for lift and propulsion of the EDW. The focus of our experiments is determining how to maximize the lift-to-drag ratio by the proper choice of the induction element. We will also describe our experiments with a rotating circular Halbach array having the strong magnetic field of about 1 T on the flat side of the ring, and acting as a hovercraft.   

Thermal Noise of Epoxies

Interferometric precision optical measurement is a powerful tool for investigating the smallest of physical phenomena. Examples of this include gravitational wave detection, precision spectroscopy, and laser ring gyroscopes. The limiting noises sources include thermal fluctuations from optical materials and structures. Epoxies can be used to construct hardware for these experiments, which can significantly contribute to the thermal noise. At American University, we are investigating the elastic properties of various epoxies to better predict thermal noise.   

Seasonal Dependence and Aging Effect of GEM Prototype~for the SiD~in the ILC

High energy physics experiments require detectors and electronics that are capable of high precision, stable energy read out. Since 2007, the Advance Detector team in University of Texas at Arlington has been working on the Gas electron multiplier (GEM) detector technology. The detector technology utilizes the avalanche effect of charged particles in high electric field to magnify hadron signals produced in collision for precise and accurate energy interpretation. KPiX is a multi-channel 13 bits electronic chip designed for the time synchronous requirements of the Silicon Detector (SiD) in the International Linear Collider (ILC). The chip is coupled with GEM in this experiment to study the aging of the prototype 30cmx30cm detector. In this study, cosmic ray is used as a source to study the gain fluctuation of GEM over a period of 3 years. Statistics methods are implemented to investigate the seasonal dependence of the gain of the signal. Also, the self-trigger mode of KPiX v.9 enable the study of the electronics though the chip's electronics gain variation. Results over 3 years shows that GEM is capable of stable data read out with little aging effect. The study provides invaluable information of the detector on its stability as a calorimeter.   

Investigation of Self Triggered Cosmic Ray Detectors using Silicon Photomultiplier

The silicon photomultiplier (SiPM) is a highly sensitive light detector capable of measuring single photons. It costs a fraction of the photomultiplier tube and operates slightly above the breakdown voltage. At this conference we describe our investigation of SiPM, the multipixel photon counters (MPPC) from Hamamatsu as readout detectors for plastic scintillators working for detecting cosmic ray particles. Our setup consists of scintillator sheets embedded with blue to green wavelength shifting fibers optically coupled to MPPCs to detect scintillating light. Four detector assemblies would be constructed and arranged to work in self triggered mode. Using custom matching tee boxes, the amplified MPPC signals are fed to discriminators with threshold set to give a reasonable coincidence count rate. Moreover, the detector waveforms are digitized using a 5 Giga Samples per second waveform digitizer, the DRS4, and triggered with the coincidence logic to capture the MPPC waveforms. Offline analysis of the digitized waveforms is accomplished using the CERN package PAW and results of our experiments and the data analysis would also be discussed.   

Near-field effects in radio-frequency emission from particle showers in a dense medium

Two mechanisms are expected to produce radio-frequency emission in ultra-high energy cosmic ray air showers. Askaryan emission, generated by an overall charge excess, has been studied in beam experiments previously. The emission due to Earth's magnetic field has been inferred from observations by cosmic-ray observatories, but not yet studied in a controlled laboratory environment. The SLAC T-510 experiment recently studied the effects of a magnetic field upon the radio-frequency emission from particle showers in high-density polyethylene as a way to model cosmic ray air showers. Ultra-High Frequency (UHF) and Very High Frequency (VHF) antennas were used to measure the signal from particle showers in the target at different positions. For an overview, see the talk by K. Mulrey in this conference. Several near-field runs were performed with the UHF antenna array closer to the target than in the majority of the data taking. Signal from the two mechanisms, Askaryan and Magnetic, were separated into orthogonal polarizations by the geometry of the system. We report on studies of the electric field for several positions in the near field. Initial results indicate that the electric field as a function of angle behaves consistently as the antennas are moved further from the target.   

Neoclassical bootstrap current models for describing NSTX plasmas

In the study of magnetically confined fusion plasmas, the motion of particles and energy across magnetic field lines can be described by neoclassical transport theory. For the toroidal magnetic geometry of a tokamak reactor, one of the main results of this theory is the generation of a current as a result of interaction between trapped and passing particles. This so-called bootstrap current is of particular interest because it generates an additional component to the magnetic field which helps to confine particles to the center of the reactor. Here, a neoclassical transport code is used to calculate the bootstrap current based on several experimental plasma profiles from the National Spherical Torus Experiment, and the results are compared to several classic models to examine whether any of them sufficiently describe the simulated bootstrap current profiles.   

Muon Detection with a Ring Imaging Cerenkov Radiation Detector

Our goal is to measure the cosmic muon spectrum. We are developing a low-cost RICH detector by the modification of a digital camera. The detector will be suitable for a low budget laboratory. I will discuss the engineering and materials selection involved in building the detector from commercial off the shelf equipment, and present examples of the data obtained.   

Gravitational Redshift of Deformed Neutron Stars

Non-rotating neutron stars are generally treated in theoretical studies as perfect spheres. Such a treatment, however, may not be correct if strong magnetic fields are present and/or the pressure of the matter in the cores of neutron stars is non-isotropic, leading to neutron stars which are deformed. In this work, we investigate the impact of deformation on the gravitational redshift of neutron stars in the framework of general relativity. Using a parameterized metric to model non-spherical mass distributions, we derive an expression for the gravitational redshift in terms of the mass, radius, and deformity of a neutron star. Numerical solutions for the redshifts of sequences of deformed neutron stars are presented and observational implications are pointed out.