Complex Permittivity Measurements at Variable Temperatures of Low Loss Dielectric Substrates Employing Split Post and Single Post Dielectric Resonators

A split post dielectric resonator in a copper enclosure and a single post dielectric resonator in a cavity with superconducting end-plates have been constructed and used for the complex permittivity measurements of single crystal substrates. (La,Sr)(Al,Ta)O3, LaAlO3, MgO and quartz substrates have been measured at temperatures from 20 K to 300 K in the split post resonator and from 15 K to 80 K in the single post resonator. The TE01delta mode resonant frequencies and unloaded Qo-factors of the empty resonators at temperature of 20 K were: 9.952 GHz and 25,000 for the split post resonator and 10.808 GHz and 240,000 for the single post resonator respectively.Comment: 4 pages, 8 figures, 1 tabl

Discovery of Bragg confined hybrid modes with high Q-factor in a hollow dielectric resonator

The authors report on observation of Bragg confined mode in a hollow cylindrical dielectric cavity. A resonance was observed at 13.4 $GHz$ with an unloaded Q-factor of order $2\times10^5$, which is more than a factor of 6 above the dielectric loss limit. Previously such modes have only been realized from pure Transverse Electric modes with no azimuthal variations and only the $E_{\phi}$ component. From rigorous numeric simulations it is shown that the mode is a hybrid mode with non-zero azimuthal variations and with dominant $E_r$ and $E_{\phi}$ electric field components and $H_z$ magnetic field component.Comment: Accepted to be published in Applied Physics Letter

Detrapping and retrapping of free carriers in nominally pure single crystal GaP, GaAs and 4H-SiC semiconductors under light illumination at cryogenic temperatures

We report on extremely sensitive measurements of changes in the microwave properties of high purity non-intentionally-doped single-crystal semiconductor samples of gallium phosphide, gallium arsenide and 4H-silicon carbide when illuminated with light of different wavelengths at cryogenic temperatures. Whispering gallery modes were excited in the semiconductors whilst they were cooled on the coldfinger of a single-stage cryocooler and their frequencies and Q-factors measured under light and dark conditions. With these materials, the whispering gallery mode technique is able to resolve changes of a few parts per million in the permittivity and the microwave losses as compared with those measured in darkness. A phenomenological model is proposed to explain the observed changes, which result not from direct valence to conduction band transitions but from detrapping and retrapping of carriers from impurity/defect sites with ionization energies that lay in the semiconductor band gap. Detrapping and retrapping relaxation times have been evaluated from comparison with measured data.Comment: 7 pages, 6 figure

Modified permittivity observed in bulk Gallium Arsenide and Gallium Phosphide samples at 50 K using the Whispering Gallery mode method

Whispering Gallery modes in bulk cylindrical Gallium Arsenide and Gallium Phosphide samples have been examined both in darkness and under white light at 50 K. In both samples we observed change in permittivity under light and dark conditions. This results from a change in the polarization state of the semiconductor, which is consistent with a free electron-hole creation/recombination process. The permittivity of the semiconductor is modified by free photocarriers in the surface layers of the sample which is the region sampled by Whispering Gallery modes.Comment: 8 pages, 3 figure

Effects of a Mobile Fueling Station on Performance in Division III Soccer Players

Topics in Exercise Science and Kinesiology Volume 4: Issue 1, Article 11, 2023. This study aimed to determine if there was an ergogenic effect of utilizing a mobile fueling station in Division III soccer teams. Mobile fueling stations have been shown to be a feasible and sustainable option to support nutrition periodization in college-aged athletes. To date, no studies have analyzed the effect of these stations on athletic performance. We analyzed the effects of this fueling strategy on sprint speed, sprint count, and athlete acceptance during soccer practices and competitions. Athletes from the DeSales University Men’s and Women’s soccer teams (n=35) completed two weeks of data collection in a randomized, crossover design, with one week of fueling using the mobile fueling station (WS), and one week without fueling (NS). In the WS condition, participants ate a carbohydrate-containing snack before soccer practice or competition and ate a snack containing carbohydrates and protein after. Sprint data were collected using GPS sensors, and a post-study questionnaire evaluated athlete acceptance and perceived effectiveness. An a priori alpha level for significance was set at 0.05, and sprint data were analyzed using univariate analysis of variance. While there were no statistically significant differences (p\u3e0.05) in peak (WS=7.65 m/s, NS=7.9 m/s) and mean (WS=6.93 m/s, NS=7.01 m/s) sprint speed or maximum (WS=13, NS=12.16) and mean (WS=8.16, NS=7.46) sprint count, survey responses indicated that 100% of athletes found that mobile fueling stations improved their athletic performance and would like it to be a permanent fixture of their athletic program. These results indicate that mobile fueling stations are perceived as beneficial by Division III soccer players