[Truncated abstract] Infrared (IR) detectors have many applications, from homeland security and defense, to medical imaging, to environmental monitoring, to astronomy, etc. Increasingly, the wave- length dependence of the IR radiation is becoming important in many applications, not just the total intensity of infrared radiation. There are many types of infrared detectors that can be broadly categorized as either photon detectors (narrow band-gap materials or quantum structures that provide the necessary energy transitions to generate free car- riers) or thermal detectors. Photon detectors generally provide the highest sensitivity, however the small transition energy of the detector also means cooling is required to limit the noise due to intrinsic thermal generation. This thesis is concerned with the tech- nique of resonant-cavity-enhancement of detectors, which is the process of placing the detector within an optically resonant cavity. Resonant-cavity-enhanced detectors have many favourable properties including a reduced detector volume, which allows improved operating temperature, or an improved signal to noise ratio (or some balance between the two), along with a narrow spectral bandwidth. ... Responsivity of another sample annealed for 20 hours at 250C in a Hg atmosphere (ex-situ) also shows resonant performance, but indicates significant shunting due the mirror layers. There is good agreement with model data, and the peak responsivity due to the absorber layer is 9.5×103 V/W for a 100 'm ×100 'm photoconductor at 80K. An effective lifetime of 50.4 ns is extracted for this responsivity measurement. The responsivity was measured as a function of varying field, and sweepout was observed for bias fields greater than 50 V/cm. The effective lifetime extracted from this measurement was 224 ns, but is an over estimate. Photodiodes were also fabricated by annealing p-type Hg(1x)Cd(x)Te for 10 hours at 250C in vacuum and type converting in a CH4/H2 reactive ion etch plasma process to form the n-p junction. There is some degradation to the mirror structure due to the anneal in vacuum, but a clear region of high reflection is observed. Measurements of current-voltage characteristics at various temperatures show diode-like characteristics with a peak R0 of 10 G measured at 80K (corresponding to an R0A of approximately 104 cm2. There was significant signal from the mirror layers, however only negligible signal from the absorber layer, and no conclusive resonant peaks.

No description available.

Call number: LD2668 .T4 1979 H364 / Master of Science / Mechanical and Nuclear Engineering

This thesis is based on modifications performed on the U.S. Army TACOM (Tank Automotive Command, Warren, Michigan) Thermal Imaging Model (TTIM). It discusses the TTIM computer model of a staring thermal imaging sensor with respect to spatial nonuniformities. The spatial nonuniformities in a staring sensor is caused by fixed pattern noise or responsivity variations across the sensor. The objective of the thesis is to present the correction schemes for spatial nonuniformities present on a staring thermal imaging sensor and the data analysis of the corrections using flat field and bar chart targets of known temperatures. The signal-to-noise ratios (S/Ns) of the images will be calculated and measured before and after the correction. A simulated image after a one-point correction will be evaluated by comparison with an image from a real system using a platinum silicide thermal imaging sensor. The limits and assumptions of the simulation also will be discussed.

Master of Science / Department of Mechanical and Nuclear Engineering / William L. Dunn / Two types of high efficiency neutron detector arrays (HENDAs), a 32-channel planar device and two trenched devices, were constructed at Kansas State University (KSU) and characterized. These HENDAs are prototypes for a detector that will be developed for the Spallation Neutron Source (SNS), which is located at Oak Ridge National Laboratory (ORNL). The general design objectives of a proposal from the KSU Semiconductor Materials and Radiological Technologies (SMART) Lab to the National Science Foundation, which led to a grant that funded this research, were reached. A spatial resolution for the HENDA prototypes of approximately 120 μm was achieved. The prototypes had relatively fast response times of approximately 1.2 μs, with rise times of 300 ns for the planar device and 200 ns for the 100-μm deep trenched device. The thermal neutron counting efficiency of one of the trenched devices was measured to be about 12%. It is expected that the goal of a 50% efficient HENDA is attainable by making trenches contained within the trenched device deeper and by stacking modules in a sandwich design. The pulse heights produced by the HENDA prototypes were approximately 0.5 volt with noise levels of 13 mvolt, resulting in a signal to noise ratio of almost 40:1. The response of HENDA, when placed in the neutron beam from the tangential beam port of the KSU TRIGA Mark II was proportional to the reactor power from 2 kW to 512 kW. At 512 kW, the neutron flux is φ = 1.08x10[superscript]7 cm[superscript]-2 s[superscript]-1, and therefore HENDA can operate with negligible dead time at neutron fluxes beyond 107 cm-2 s-1. From the experimental results, HENDA is a valuable linear array detector and can be applied to experiments that are designed to study material properties and structures through methods such as neutron diffraction and imaging.

published_or_final_version / Chemistry / Master / Master of Philosophy

No description available.

Abstract In New Zealand there are currently no regular external audits to verify the full treatment chain in radiotherapy. This thesis reports on a project to devise such an audit procedure suitable to assess the accuracy of the delivery of prescribed radiotherapy doses to patients over the full treatment process. The National Radiation Laboratory (NRL), regulatory authority, will use the method developed to conduct biennial audits of all radiotherapy centres. A commercial chest phantom with a MOSFET dosimetry system was provided for this project. The MOSFETs were commissioned and their characteristics determined, namely reproducibility, energy dependence and angular dependence. The MOSFETs were also tested in a clinical environment with the phantom. Measurements were carried out to test the MOSFET capabilities in both lung and soft tissue in the phantom. Two plans were devised for the audit process, a straightforward one with two parallel opposed beams and a more complex one involving lung tissue and wedges. These plans were designed to test the entire treatment planning and delivery process. It was found that each MOSFET detector needed to be individually calibrated. Reproducibility was found to have an average standard deviation of 2% on standard sensitivity and 1.2% on high sensitivity. The angular dependence of the detectors showed that when the MOSFET was rotated by 90 degrees to the beam axis a drop in response of 3% was observed with 6 MV. The energy dependence factor was constant within uncertainty for all MOSFETs. Overall, the MOSFET and phantom dosimetry system was determined to be suitable for the audit. The measurements with phantom showed that doses in high dose regions could be determined accurately. The greatest variation from the Treatment Planning system dose to the measured dose was 6%. The trial runs of the audit in two New Zealand radiotherapy centres showed that the procedure created is able to find discrepancies within the desired 5%, recommended by the ICRU, in the prescribed dose to the phantom.

A novel detector for ultra-high energy cosmic rays, and its prototype are discussed. It detects events with primary energy greater than 100 PeV. (1 PeV = 1000 TeV; 1EeV = 1000 PeV.) The detector operates by sensing the near-ultraviolet scintillation light of ionized nitrogen molecules created by the passage of ionizing particles in extensive air showers. (The concept is loosely based on the highly successful Fly's Eye detector situated at Dugway, Utah.) Typical events should consist of 1 to 100 EeV primary energy showers, with near-vertical cores, passing through the detector's field-of-view at distances of 1 to 20 km. The optical field of view of the hypothetical detector would be 60 degrees wide by several (≈ 3) degrees high and would look in a near-horizontal direction at a distant mountain range or other suitably dark background roughly 20 Ian away. A typical good location would be the rim of a canyon, looking slightly downward at the other side. The field-of-view would be subdivided into 3 or more thinner ''wedges'', 60 degrees wide by, perhaps, 1 degree high. A single detector provides timing and brightness information only. Three widely-separated detectors with overlapping fields-of-view provide sufficient data to determine the core location, the zenith and azinruthal angles of the core axis, and the absolute luminosity of the cascade. Interpretation of the luminosity data would be a challenge, but it should be possible to estimate primary energy from it. The advantage of this new scheme is the enormous effective detector area per relatively low-cost detector module. Each triplet of detectors "sees" 300 square km with a typical core axis acceptance of roughly 1 sr. The construction and testing of a prototype unit has been accomplished. The field-of-view was 41 degrees wide by 2 degrees high. Light was collected by a 4.7 square meter mirror and focused onto a wave-shifter PMT system. 8 events with primary energies in the 0.1 to 1 EeV range were observed in an 8.5 hour period. Representative events are shown and preliminary data analysis is discussed.

The research described in this dissertation is the first evaluation and application of a new class of optical detectors, two-dimensional charge-coupled device (CCD), for low-light level chemiluminescence and other luminescence spectroscopies. This research conclusively demonstrates the superior qualitative and quantitative performance of spectrometric systems which employ these detectors. It is experimentally shown that a single detector element of a CCD has comparable or superior sensitivity to the most sensitive single channel detectors; photomultiplier tubes (PMT). The results from the application of the CCD detector system to molecular spectroscopies (fluorescence, chemiluminescence, fluorescence detection of high performance liquid chromatography (HPLC) effluents, and chemiluminescence detection of HPLC effluents) and atomic spectroscopies (spatially and spectrally resolved spark and direct current plasma are presented). The results of operating the CCD in specialized readout modes developed in this research termed charge dependent variable binning (CDVB), simultaneous variable binning (SVB), and continuous high speed spectral framing (CHSF) are described and applied. The CDVB and SVB techniques allow very sensitive quantitation of spectrally resolved and unresolved signals with very wide dynamic ranges without prior knowledge of the signal intensity. Finally, CHSF technique provides spectrally resolved temporal study of extended period luminescence emission with millisecond time resolution. The results of unique algorithms to restore the integrity of the image obtained with a two-dimensional CCD detector are described and applied. The algorithms implemented are for removing variations in detector sensitivity and responsivity and spectrometer efficiency, as well as providing digital image filtering.