Design, simulation and experiment of a cusp electron beam for millimeter wave gyro-devices

The design, simulation and experiment of a thermionic cusp electron gun that is to be used for millimeter wave generation will be presented. A cusp gun uses a non-adiabatic magnetic field reversal to obtain azimuthal motion on an electron beam resulting in an annular shaped, axis-encircling beam. The cusp gun was designed to generate a beam of 1.5A at 40kV with an adjustable velocity ratio of up to 3.0. The beam had a simulated axial velocity spread of 7.4% and alpha spread of 10.1%. The beam had an averaged radius of 0.35mm and beam thickness of 0.05mm which is ideal to drive sub-mm wave gyro-devices under investigation

The appropriate initiation of parenteral nutrition per ASPEN criteria in a community hospital

Introduction The American Society for Parenteral and Enteral Nutrition (ASPEN) has published guidelines for the proper initiation of parenteral nutrition (PN) in order to safelyadminister PN. Objective The objective of this study is to determine the amount of PN orders that were appropriately initiated according to ASPEN guidelines within the WellStar North Fulton campus. Methods This study is a single-center, retrospective chart review over 30 months. The data was collected from Wellstar North Fulton Hospital patients from January 1st, 2019, to July 19th, 2021. The sample size is 115 patients. Appropriate initiation of PN was determined by analyzing how PN is used at WellStar and comparing them to the ASPEN guideline recommendations. Patient charts were reviewed to determine if a patient is appropriately receiving per ASPEN guidelines. An appropriate use assessment was conducted which included indication, timing, and duration of PN orders. The primary endpoint is the appropriate initiation of PN at Wellstar North Fulton Hospital. Secondary endpoints studied included the service line of provider writing PN order and the total cost of PN. Inclusion criteria includes all patients over the age of 18 who had PN orders from January 1st, 2019 to July 19th, 2021. Exclusion criteria excludes all patients under the age of 18 year who had not received PN. Data collected includes patient demographics such as age, gender, admission date, PN administration date and duration. Prescriber information and service line was also collected. Results A total of 115 charts were reviewed. Of these charts, 109 had PN administered. Of these administrations, 64 were determined to be appropriate (58.7%) while 45 were determined to be inappropriate (41.3%). The most common reason for inappropriate PN orders was duration, with 22 out of 45 patients (48.0%) followed by timing with 16 out of 45 patients (35.6%) and indication with 14 out of 45 patients (31.1%). Additionally, 12 out of 45 patients (26.7%) had concurrent enteral nutrition/PN or adequate oral intake and 5 out of 45 patients (11.1%) were determined to be eligible for enteral nutrition. Thirteen out of 45 patients (28.9%) had multiple reasons for inappropriate factors. Inappropriate PN loss accounted for $10,839-$13,775. Regarding prescribers, 30 out of the 45 inappropriate PN orders were written by the internal medicine service line (66.6%) followed by 7 out of the 45 inappropriate PN orders were written by the critical care service line (15.5%). Eight out of the 45 inappropriate PN orders were written by all other service lines (17.7%). Discussion/Conclusion Compared to other single-center studies, the studied facility holds up well when compared to other facilities pre-intervention. Targeted education to individual prescribers and service lines are planned in order to increase appropriate initiation of PN. Additionally, greater communication between physicians and pharmacists can increase appropriate use of PN

Bandwidth study of the microwave reflectors with rectangular corrugations

The mode-selective microwave reflector with periodic rectangular corrugations in the inner surface of a circular metallic waveguide is studied in this paper. The relations between the bandwidth and reflection coefficient for different numbers of corrugation sections were studied through a global optimization method. Two types of reflectors were investigated. One does not consider the phase response and the other does. Both types of broadband reflectors operating at W-band were machined and measured to verify the numerical simulations

Investigation on the optimal magnetic field of a cusp electron gun for a W-band gyro-TWA

High efficiency and broadband operation of a gyrotron traveling wave amplifier (gyro-TWA) requires a high-quality electron beam with low-velocity spreads. The beam velocity spreads are mainly due to the differences of the electric and magnetic fields that the electrons withstand the electron gun. This paper investigates the possibility to decouple the design of electron gun geometry and the magnet system while still achieving optimal results, through a case study of designing a cusp electron gun for a W-band gyro-TWA. A global multiple-objective optimization routing was used to optimize the electron gun geometry for different predefined magnetic field profiles individually. Their results were compared and the properties of the required magnetic field profile are summarized

A pillbox window with impedance matching sections for a W-band gyro-TWA

A mode-matching method was developed to design a pillbox-type millimeter wave window for a W-band gyrotron traveling wave amplifier. With additional impedance matching sections, the pillbox window was able to achieve -40 dB reflection over a 10% frequency bandwidth. The manufactured pillbox window achieved a maximum reflection of -15 dB. The reasons for the difference between the simulated and measured reflections were investigated

Design of a multilayer output window for a 372 GHz gyro-TWA

An output window for application in a gyrotron traveling-wave amplifier (gyro-TWA) operating at a center frequency of 372 GHz is designed and simulated. The window is based on the multilayer design and has the requirement of greater than -30 dB reflection over 24 GHz bandwidth

A multiple-hole input coupler for a 372 GHz gyro-travelling wave amplifier

The design of a multiple-hole coupler that operates at a center frequency of 372 GHz for use in a gyrotron travelingwave amplifier (gyro-TWA) is presented. In simulations, the coupler achieved 35% bandwidth from 289GHz to–410 GHz with transmission losses of -0.5 dB predicted

Input coupling systems for millimetre-wave gyrotron travelling wave amplifiers

Input couplers for millimetre-wave gyrotron travelling wave amplifiers are presented in this study. A W-band input coupling system composed of a pillbox window, a smoothly curved waveguide bend, a T-junction and a broadband reflector was numerically optimised, constructed and measured. An average transmission coefficient of −2.0 dB over a designed operating frequency range was measured. Additionally, a higher-frequency input coupler for operation at a central frequency of 372 GHz was also designed based on a multiple-hole coupling configuration. The simulated transmission coefficient was −0.5 dB if the ohmic loss is not considered

Understanding mobile VLE usage in distance education: A pilot study

This paper presents preliminary results of a mobile virtual learning environment (VLE) usage study conducted at a United Kingdom (UK) based distance education institution. A total of 207 undergraduate students participated in the study over a period of 6 months. Study participants were recruited through email invitation. An online survey was conducted to gather both quantitative and qualitative data about (i) learner characteristics, (ii) awareness about the existence of the mobile VLE system, (iii) perceptions about the usefulness of using the mobile VLE system to support learning, (iv) attitudes towards using mobile VLE technological tools to support learner activities, and (v) motives for using mobile VLE tools when carrying out learning activities. Results indicate that perceived usefulness of the various technological tools incorporated in the mobile VLE system and also familiarity with their usage in teaching and learning has an effect on their deployment in distance education. These findings confirm our assumptions that the design and integration of mobile VLE in teaching and learning should be closely aligned with pedagogical goals and established practices

Multi-mode coupling wave theory for helically corrugated waveguide

Helically corrugated waveguide has been used in various applications such as gyro-backward wave oscillators, gyro-traveling wave amplifier and microwave pulse compressor. A fast prediction of the dispersion characteristic of the operating eigenwave is very important when designing a helically corrugated waveguide. In this paper, multi-mode coupling wave equations were developed based on the perturbation method. This method was then used to analyze a five-fold helically corrugated waveguide used for X-band microwave compression. The calculated result from this analysis was found to be in excellent agreement with the results from numerical simulation using CST Microwave Studio and vector network analyzer measurements