A method has been developed to fabricate waveguideto-waveguide couplers and tapered dielectric ro... more A method has been developed to fabricate waveguideto-waveguide couplers and tapered dielectric rod antennas for the millimeter-wave regime from microetched silicon. A proof-ofconcept study shows that the structures can be realized using relatively simple wet etching and robotic process control. Experimental measurements of the waveguide-waveguide couplers agree in key features with simulations. The results indicate that two-stepped tapers perform nearly as well as smooth linear tapers, but are much easier to fabricate. Coupling transmissivity of better than −1 dB, and peak antenna gain of 8-10 dB are indicated at W-band frequencies. Lateral dimension etch control of 5-μm precision was realized. To solve a challenge of controlling the length of the first step, either an improved masking method or a switch to dry etching processes is required. Index Terms-Dielectric rod antenna, dielectric waveguide, millimeter-wave, terahertz (THz). I. INTRODUCTION E MERGING needs exist for novel sources of highfrequency radiation sources, in the frequency ranges of 30-300 GHz (millimeter-wave) and 300-1000 GHz [terahertz (THz)]. These include high-data-rate communication, highresolution radar, biomedical imaging, and remote sensing [1]-[6]. To exploit these new high-frequency sources, it is also necessary to develop specialized components, such as lowloss waveguides and antennas. This is particularly important in compact high-frequency vacuum electronic devices where novel methods for input and output coupling are needed that Manuscript
ABSTRACT Metamaterials and periodic structures operating under high-power excitations are suscept... more ABSTRACT Metamaterials and periodic structures operating under high-power excitations are susceptible to breakdown. It was recently demonstrated that a localized breakdown created in a given region of a periodic structure can facilitate breakdown in other regions of the structure where the intensity of the incident electromagnetic fields may not be high enough to cause breakdown under normal circumstances. It was also demonstrated that this phenomenon is due to the generation of vacuum ultraviolet radiation at the location of the initial discharge, which propagates to the neighboring regions (e.g., other unit cells in a periodic structure) and facilitates the generation of a discharge at a lower incident power level. In this paper, we present the results of an experimental study conducted to determine the effective range of this physical phenomenon for periodic structures that operate in air and in pure nitrogen gas at atmospheric pressure levels. It is demonstrated that when breakdown is induced in a periodic structure using a high-power pulse with a frequency of 9.382 GHz, duration of 0.8 mu s, and peak power level of 25 kW, this phenomenon is highly likely to happen in radii of approximately 16-17mm from the location of the initial discharge under these test conditions. The results of this study are significant in designing metamaterials and periodic structures for high-power microwave applications as they suggest that a localized discharge created in such a periodic structure with a periodicity less than 16-17mm can spread over a large surface and result in a distributed discharge. (C) 2014 AIP Publishing LLC.
Effective design of powerful sources and efficient components for terahertz (THz) regime radiatio... more Effective design of powerful sources and efficient components for terahertz (THz) regime radiation requires knowledge of dissipation losses caused by conducting surfaces. However, theoretical predictions for the effect of roughness on the reflectivity of surfaces are untested in this frequency regime. Measurements of the electronic properties of metals and semiconductors are performed using a high quality factor quasi-optical (QO) hemispherical resonator operating at 650 GHz. Large area (> 1 cm x 1 cm) copper surfaces with controlled nanoscale surface roughness are fabricated using either an abrasive process or a chemical etching process. Measurement of the reflectance of the samples shows the increased resistivity of the metal due to the surface features. These measurements are compared to approximate theoretical predictions developed by Hammerstad and Bekkadal, rigorous theoretical predictions developed by Tsang et al. and computational simulations. Comparisons show a deviation...
Development of high power microwave (HPM) distributed discharge limiters relies critically on min... more Development of high power microwave (HPM) distributed discharge limiters relies critically on minimizing the delay time between HPM incidence and diffuse plasma creation. Breakdown is achieved by illuminating a gas cell with a train of ˜25kW, ˜2 kV/cm, 800ns-long pulses at 41 HZ repetition rate. Using mixtures of neon with small concentrations of argon or xenon at pressures between 5-350 torr, we have observed breakdown in <100ns for particular choices of gas composition and pressure. Breakdown times predicted by published theoretical modelsfootnotetextY.Y. Lau, J.P. Verboncoeur, H.C. Kim, ``Scaling laws for dielectric window breakdown in vacuum and collisional regimes,'' Appl. Phys. Letters, Vol. 89, 261501-1. are approximately 3-5 times longer than our experimental observations. Careful study of experimental trends suggest surface charge accumulation on the gas cell's polycarbonate window and Penning-like effects in mixtures of noble gases may explain the observatio...
An essential element of distributed discharge limiter development is minimizing the delay time be... more An essential element of distributed discharge limiter development is minimizing the delay time between high power microwave (HPM) incidence and diffuse plasma creation. We present a series of pulsed plasma experiments conducted in neon and argon from 80-760 torr designed to assess methods of reducing this delay time. Evidence is presented implicating a charge buildup effect on the dielectric window with a characteristic decay time constant on the order of tens of minutes to several hours. A detailed description of the experimental setup used in this study is provided and progress towards development of a high-frequency multi-moded signal acquisition system is also presented, including the development of a circuit analog absorber designed to provide greater than 30dB attenuation with a thickness of less than 2cm.
ABSTRACT We present a preliminary in vivo study of the microwave-frequency dielectric properties ... more ABSTRACT We present a preliminary in vivo study of the microwave-frequency dielectric properties of mice breast tumor xenografts with accumulation of single-walled carbon nanotubes (SWCNTs). Dispersions of SWCNT-DSPE-PEG at various concentrations were injected directly into 22 tumors. Dielectric properties (1-6 GHz) before and after the injection were characterized using an open-ended coaxial probe technique. Baseline measurements (sham control and PEG only) were also conducted in 12 tumors. We found at least a ~10% relative permittivity enhancement effect upon injection of 100 μl of SWCNT stock solutions at concentrations ranging between 3 and 7 mg/ml.
The resistive wall amplifier (RWA), a vacuum electron device, has been theoretically predicted to... more The resistive wall amplifier (RWA), a vacuum electron device, has been theoretically predicted to provide extremely high gain. However, the properties of practical, naturally available bulk materials for the resistive wall support structure significantly reduce achievable gain. This paper investigates the capabilities of a metamaterial-enhanced RWA (ME-RWA). We predict that using epsilon-negative metamaterials can yield high gains that closely approach the idealized performance limit. ME-RWAs may exhibit bandwidths and gains much higher than many commercially available vacuum electron devices.
The design of sources and components for terahertz (THz) regime radiation is influenced by dissip... more The design of sources and components for terahertz (THz) regime radiation is influenced by dissipation losses in conducting surfaces. In this regime, however, predictive capability of surface loss is lacking. A high quality factor quasi-optical (QO) hemispherical resonator operating at 400 GHz to 650 GHz is designed and implemented for the measurement of electronic properties of conductors and low-loss dielectrics. Large area, periodic, textured gold surfaces are fabricated using nanoimprinted resist as a mold for an electroforming process. A comparison of the measured effective conductivity between the samples shows the increased resistivity of the metal due to the surface features. The regular geometry of these textures enables straightforward computational simulation and direct comparison to experiment. In addition to the nanofabricated structures, we will also present measured conductivity of samples that are lapped to different average roughness values. Computational simulation...
Research and development of optimized vacuum electronic sources utilizing advanced computational ... more Research and development of optimized vacuum electronic sources utilizing advanced computational codes and state-of-the-art micro- fabrication techniques were performed focusing on using micromachining to develop THz regime folded-waveguide traveling-wave tubes (TWTs). Successful development of THz TWTs has enormous potential for low-cost, extremely-high-data-rate (> 10 GB/s) advanced digital communications capabilities, as well as lower cost, higher yield production of millimeter-wave slow-wave amplifiers for air-borne radar and missile seeker technologies. To address the need for compact THz radiation sources (amplifiers and oscillators), micro-fabricated TWTs were invented under this program and feasibility analyses were completed resulting in representative designs for a 56 mW, 560 GHz recirculated feedback oscillator and a 174 mW, 400 GHz amplifier. The recirculated feedback oscillator concept was successfully demonstrated experimentally at a scaled frequency, and in depth s...
IEEE MTT-S International Microwave Symposium digest. IEEE MTT-S International Microwave Symposium
This material is presented to ensure timely dissemination of scholarly and technical work. Copyri... more This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.
Summary form only given. Calabazas Creek Research, Inc is funded by the US Department of Energy (... more Summary form only given. Calabazas Creek Research, Inc is funded by the US Department of Energy (DOE), the National Aeronautics and Space Administration (NASA), and the US Air Force (USAF) to investigate applications for micro-electromechanical systems (MEMS) and field emission array (FEA) cathodes for vacuum electron devices. These include high power klystrons, traveling wave tubes (TWT's), and backward wave oscillators (BWOs). This presentation will describe how new advances in MEMS and FEA technology are enabling development of a new generation of RF devices.
This material is presented to ensure timely dissemination of scholarly and technical work. Copyri... more This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.
2011 IEEE International Vacuum Electronics Conference (IVEC), 2011
Skip to Main Content. IEEE.org | IEEE Xplore Digital Library | IEEE Standards Association | Spect... more Skip to Main Content. IEEE.org | IEEE Xplore Digital Library | IEEE Standards Association | Spectrum Online | More IEEE Sites. IEEE Xplore Digital Library. Search Term(s). Advanced Search | Preferences | Search Tips. ...
2011 IEEE International Vacuum Electronics Conference (IVEC), 2011
Page 1. 18.3: Measurement of Surface Roughness Effects on Conductivity in the Terahertz Regime wi... more Page 1. 18.3: Measurement of Surface Roughness Effects on Conductivity in the Terahertz Regime with a High-Q Quasioptical Resonator Benjamin B. Yang1, Sarah L. Katz and John H. Booske2 Department of Electrical and ...
2008 33rd International Conference on Infrared, Millimeter and Terahertz Waves, 2008
ABSTRACT Calabazas Creek Research, Inc. (CCR) and the University of Wisconsin, Madison (UW) are d... more ABSTRACT Calabazas Creek Research, Inc. (CCR) and the University of Wisconsin, Madison (UW) are developing a 650 GHz traveling wave tube amplifier (TWTA). Simulations predict 360 mW peak output power with a 2-10% duty cycle. This paper summarizes the design and fabrication of the TWT. Testing is expected in November, 2008.
Calabazas Creek Research, Inc. (CCR) is funded to develop a wide variety of RF sources from 81 GH... more Calabazas Creek Research, Inc. (CCR) is funded to develop a wide variety of RF sources from 81 GHz to 2 THz. Two traveling wave tubes are in development at 83.5 GHz for satellite communications applications. Development was performed on an overmoded, suspended ladder circuit at 95 GHz for high power applications. Two sources are in development at 650 GHz. CCR is continuing development of a 600-700 GHz backward wave oscillator and is funded to develop a 650 GHz TWTA (including the power supply). This TWT design incorporates a sheet electron beam and a planar circuit. To address high peak power applications, CCR is developing a gyrotron to generate peak power pulses exceeding 5 kW from a few hundred GHz up to 2.0 THz.
2013 Abstracts IEEE International Conference on Plasma Science (ICOPS), 2013
ABSTRACT form only given. Development of high power microwave (HPM) distributed discharge limiter... more ABSTRACT form only given. Development of high power microwave (HPM) distributed discharge limiters relies critically on minimizing the delay time between HPM incidence and diffuse plasma creation. We present a range of pulsed plasma experiments conducted in neon, argon, helium, and mixtures of these gases, from 50-760 torr. Breakdown is achieved by illuminating a gas cell with a ~25kW, ~2 kV/cm, 800ns-long pulse as well as 41Hz pulse trains. Current results focus on preliminary experiments with metamaterial window coatings that indicate significant improvement opportunities for controlling breakdown thresholds and reducing breakdown delay. New results with gas mixtures in which observed breakdown occurs in
2012 Abstracts IEEE International Conference on Plasma Science, 2012
ABSTRACT form only given. Development of high power microwave (HPM) distributed discharge limiter... more ABSTRACT form only given. Development of high power microwave (HPM) distributed discharge limiters relies critically on minimizing the delay time between HPM incidence and diffuse plasma creation. We present a series of pulsed plasma experiments conducted in neon, argon, and a 9∶1 mixture of the two gases from 50–760 torr. Breakdown is achieved by illuminating a gas cell with a train of ∼25kW, ∼2 kV/cm, 800ns-long pulses at 41Hz repetition rate. The results suggest that surface charge accumulation on the gas cell&#39;s polycarbonate window from many low density precursor discharges eventually results in rapid (&lt;30ns), high density, discharge formation. The number of precursor pulses required to form these high density discharges is significantly reduced following a previous high-density discharge.
We present a formulation for achieving stable high-concentration (up to 20 mg/ml) aqueous dispers... more We present a formulation for achieving stable high-concentration (up to 20 mg/ml) aqueous dispersions of carbon nanotubes (CNTs) with exceptionally high microwave-frequency (0.5-6 GHz) dielectric properties. The formulation involves functionalizing CVD-synthesized CNTs via sonication in nitric and sulfuric acid. The overall chemical integrity of the CNTs is largely preserved, as demonstrated via physical and chemical characterizations, despite significant shortening and functionalization with oxygen-containing groups. This is attributed to the protected inner walls of double-walled CNTs in the samples. The resulting CNT dispersions show greatly enhanced dielectric properties compared to a CNT-free control. For example, at 3 GHz, the average relative permittivity and effective conductivity across several 20 mg/ml CNT samples were increased by ∼ 70% and ∼ 400%, respectively, compared to the control. These CNT dispersions exhibit the stability and extraordinary microwave properties desired in systemically administered theranostic agents for microwave diagnostic imaging and/or thermal therapy.
IEEE Transactions on Terahertz Science and Technology, 2012
ABSTRACT We present an experimental study of electromagnetic losses resulting from atmospheric at... more ABSTRACT We present an experimental study of electromagnetic losses resulting from atmospheric attenuation due to water vapor on 400 GHz radiation. A hermetically sealed, high quality factor quasi-optical resonator system permits the precise control of the atmospheric water vapor content, and allows for measurement of electromagnetic losses. The empirically determined losses are compared with predictions by various different electromagnetic attenuation models. Close agreement is demonstrated with four of the models, while another differs by more than an order of magnitude at higher values of water content.
A method has been developed to fabricate waveguideto-waveguide couplers and tapered dielectric ro... more A method has been developed to fabricate waveguideto-waveguide couplers and tapered dielectric rod antennas for the millimeter-wave regime from microetched silicon. A proof-ofconcept study shows that the structures can be realized using relatively simple wet etching and robotic process control. Experimental measurements of the waveguide-waveguide couplers agree in key features with simulations. The results indicate that two-stepped tapers perform nearly as well as smooth linear tapers, but are much easier to fabricate. Coupling transmissivity of better than −1 dB, and peak antenna gain of 8-10 dB are indicated at W-band frequencies. Lateral dimension etch control of 5-μm precision was realized. To solve a challenge of controlling the length of the first step, either an improved masking method or a switch to dry etching processes is required. Index Terms-Dielectric rod antenna, dielectric waveguide, millimeter-wave, terahertz (THz). I. INTRODUCTION E MERGING needs exist for novel sources of highfrequency radiation sources, in the frequency ranges of 30-300 GHz (millimeter-wave) and 300-1000 GHz [terahertz (THz)]. These include high-data-rate communication, highresolution radar, biomedical imaging, and remote sensing [1]-[6]. To exploit these new high-frequency sources, it is also necessary to develop specialized components, such as lowloss waveguides and antennas. This is particularly important in compact high-frequency vacuum electronic devices where novel methods for input and output coupling are needed that Manuscript
ABSTRACT Metamaterials and periodic structures operating under high-power excitations are suscept... more ABSTRACT Metamaterials and periodic structures operating under high-power excitations are susceptible to breakdown. It was recently demonstrated that a localized breakdown created in a given region of a periodic structure can facilitate breakdown in other regions of the structure where the intensity of the incident electromagnetic fields may not be high enough to cause breakdown under normal circumstances. It was also demonstrated that this phenomenon is due to the generation of vacuum ultraviolet radiation at the location of the initial discharge, which propagates to the neighboring regions (e.g., other unit cells in a periodic structure) and facilitates the generation of a discharge at a lower incident power level. In this paper, we present the results of an experimental study conducted to determine the effective range of this physical phenomenon for periodic structures that operate in air and in pure nitrogen gas at atmospheric pressure levels. It is demonstrated that when breakdown is induced in a periodic structure using a high-power pulse with a frequency of 9.382 GHz, duration of 0.8 mu s, and peak power level of 25 kW, this phenomenon is highly likely to happen in radii of approximately 16-17mm from the location of the initial discharge under these test conditions. The results of this study are significant in designing metamaterials and periodic structures for high-power microwave applications as they suggest that a localized discharge created in such a periodic structure with a periodicity less than 16-17mm can spread over a large surface and result in a distributed discharge. (C) 2014 AIP Publishing LLC.
Effective design of powerful sources and efficient components for terahertz (THz) regime radiatio... more Effective design of powerful sources and efficient components for terahertz (THz) regime radiation requires knowledge of dissipation losses caused by conducting surfaces. However, theoretical predictions for the effect of roughness on the reflectivity of surfaces are untested in this frequency regime. Measurements of the electronic properties of metals and semiconductors are performed using a high quality factor quasi-optical (QO) hemispherical resonator operating at 650 GHz. Large area (> 1 cm x 1 cm) copper surfaces with controlled nanoscale surface roughness are fabricated using either an abrasive process or a chemical etching process. Measurement of the reflectance of the samples shows the increased resistivity of the metal due to the surface features. These measurements are compared to approximate theoretical predictions developed by Hammerstad and Bekkadal, rigorous theoretical predictions developed by Tsang et al. and computational simulations. Comparisons show a deviation...
Development of high power microwave (HPM) distributed discharge limiters relies critically on min... more Development of high power microwave (HPM) distributed discharge limiters relies critically on minimizing the delay time between HPM incidence and diffuse plasma creation. Breakdown is achieved by illuminating a gas cell with a train of ˜25kW, ˜2 kV/cm, 800ns-long pulses at 41 HZ repetition rate. Using mixtures of neon with small concentrations of argon or xenon at pressures between 5-350 torr, we have observed breakdown in <100ns for particular choices of gas composition and pressure. Breakdown times predicted by published theoretical modelsfootnotetextY.Y. Lau, J.P. Verboncoeur, H.C. Kim, ``Scaling laws for dielectric window breakdown in vacuum and collisional regimes,'' Appl. Phys. Letters, Vol. 89, 261501-1. are approximately 3-5 times longer than our experimental observations. Careful study of experimental trends suggest surface charge accumulation on the gas cell's polycarbonate window and Penning-like effects in mixtures of noble gases may explain the observatio...
An essential element of distributed discharge limiter development is minimizing the delay time be... more An essential element of distributed discharge limiter development is minimizing the delay time between high power microwave (HPM) incidence and diffuse plasma creation. We present a series of pulsed plasma experiments conducted in neon and argon from 80-760 torr designed to assess methods of reducing this delay time. Evidence is presented implicating a charge buildup effect on the dielectric window with a characteristic decay time constant on the order of tens of minutes to several hours. A detailed description of the experimental setup used in this study is provided and progress towards development of a high-frequency multi-moded signal acquisition system is also presented, including the development of a circuit analog absorber designed to provide greater than 30dB attenuation with a thickness of less than 2cm.
ABSTRACT We present a preliminary in vivo study of the microwave-frequency dielectric properties ... more ABSTRACT We present a preliminary in vivo study of the microwave-frequency dielectric properties of mice breast tumor xenografts with accumulation of single-walled carbon nanotubes (SWCNTs). Dispersions of SWCNT-DSPE-PEG at various concentrations were injected directly into 22 tumors. Dielectric properties (1-6 GHz) before and after the injection were characterized using an open-ended coaxial probe technique. Baseline measurements (sham control and PEG only) were also conducted in 12 tumors. We found at least a ~10% relative permittivity enhancement effect upon injection of 100 μl of SWCNT stock solutions at concentrations ranging between 3 and 7 mg/ml.
The resistive wall amplifier (RWA), a vacuum electron device, has been theoretically predicted to... more The resistive wall amplifier (RWA), a vacuum electron device, has been theoretically predicted to provide extremely high gain. However, the properties of practical, naturally available bulk materials for the resistive wall support structure significantly reduce achievable gain. This paper investigates the capabilities of a metamaterial-enhanced RWA (ME-RWA). We predict that using epsilon-negative metamaterials can yield high gains that closely approach the idealized performance limit. ME-RWAs may exhibit bandwidths and gains much higher than many commercially available vacuum electron devices.
The design of sources and components for terahertz (THz) regime radiation is influenced by dissip... more The design of sources and components for terahertz (THz) regime radiation is influenced by dissipation losses in conducting surfaces. In this regime, however, predictive capability of surface loss is lacking. A high quality factor quasi-optical (QO) hemispherical resonator operating at 400 GHz to 650 GHz is designed and implemented for the measurement of electronic properties of conductors and low-loss dielectrics. Large area, periodic, textured gold surfaces are fabricated using nanoimprinted resist as a mold for an electroforming process. A comparison of the measured effective conductivity between the samples shows the increased resistivity of the metal due to the surface features. The regular geometry of these textures enables straightforward computational simulation and direct comparison to experiment. In addition to the nanofabricated structures, we will also present measured conductivity of samples that are lapped to different average roughness values. Computational simulation...
Research and development of optimized vacuum electronic sources utilizing advanced computational ... more Research and development of optimized vacuum electronic sources utilizing advanced computational codes and state-of-the-art micro- fabrication techniques were performed focusing on using micromachining to develop THz regime folded-waveguide traveling-wave tubes (TWTs). Successful development of THz TWTs has enormous potential for low-cost, extremely-high-data-rate (> 10 GB/s) advanced digital communications capabilities, as well as lower cost, higher yield production of millimeter-wave slow-wave amplifiers for air-borne radar and missile seeker technologies. To address the need for compact THz radiation sources (amplifiers and oscillators), micro-fabricated TWTs were invented under this program and feasibility analyses were completed resulting in representative designs for a 56 mW, 560 GHz recirculated feedback oscillator and a 174 mW, 400 GHz amplifier. The recirculated feedback oscillator concept was successfully demonstrated experimentally at a scaled frequency, and in depth s...
IEEE MTT-S International Microwave Symposium digest. IEEE MTT-S International Microwave Symposium
This material is presented to ensure timely dissemination of scholarly and technical work. Copyri... more This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.
Summary form only given. Calabazas Creek Research, Inc is funded by the US Department of Energy (... more Summary form only given. Calabazas Creek Research, Inc is funded by the US Department of Energy (DOE), the National Aeronautics and Space Administration (NASA), and the US Air Force (USAF) to investigate applications for micro-electromechanical systems (MEMS) and field emission array (FEA) cathodes for vacuum electron devices. These include high power klystrons, traveling wave tubes (TWT's), and backward wave oscillators (BWOs). This presentation will describe how new advances in MEMS and FEA technology are enabling development of a new generation of RF devices.
This material is presented to ensure timely dissemination of scholarly and technical work. Copyri... more This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.
2011 IEEE International Vacuum Electronics Conference (IVEC), 2011
Skip to Main Content. IEEE.org | IEEE Xplore Digital Library | IEEE Standards Association | Spect... more Skip to Main Content. IEEE.org | IEEE Xplore Digital Library | IEEE Standards Association | Spectrum Online | More IEEE Sites. IEEE Xplore Digital Library. Search Term(s). Advanced Search | Preferences | Search Tips. ...
2011 IEEE International Vacuum Electronics Conference (IVEC), 2011
Page 1. 18.3: Measurement of Surface Roughness Effects on Conductivity in the Terahertz Regime wi... more Page 1. 18.3: Measurement of Surface Roughness Effects on Conductivity in the Terahertz Regime with a High-Q Quasioptical Resonator Benjamin B. Yang1, Sarah L. Katz and John H. Booske2 Department of Electrical and ...
2008 33rd International Conference on Infrared, Millimeter and Terahertz Waves, 2008
ABSTRACT Calabazas Creek Research, Inc. (CCR) and the University of Wisconsin, Madison (UW) are d... more ABSTRACT Calabazas Creek Research, Inc. (CCR) and the University of Wisconsin, Madison (UW) are developing a 650 GHz traveling wave tube amplifier (TWTA). Simulations predict 360 mW peak output power with a 2-10% duty cycle. This paper summarizes the design and fabrication of the TWT. Testing is expected in November, 2008.
Calabazas Creek Research, Inc. (CCR) is funded to develop a wide variety of RF sources from 81 GH... more Calabazas Creek Research, Inc. (CCR) is funded to develop a wide variety of RF sources from 81 GHz to 2 THz. Two traveling wave tubes are in development at 83.5 GHz for satellite communications applications. Development was performed on an overmoded, suspended ladder circuit at 95 GHz for high power applications. Two sources are in development at 650 GHz. CCR is continuing development of a 600-700 GHz backward wave oscillator and is funded to develop a 650 GHz TWTA (including the power supply). This TWT design incorporates a sheet electron beam and a planar circuit. To address high peak power applications, CCR is developing a gyrotron to generate peak power pulses exceeding 5 kW from a few hundred GHz up to 2.0 THz.
2013 Abstracts IEEE International Conference on Plasma Science (ICOPS), 2013
ABSTRACT form only given. Development of high power microwave (HPM) distributed discharge limiter... more ABSTRACT form only given. Development of high power microwave (HPM) distributed discharge limiters relies critically on minimizing the delay time between HPM incidence and diffuse plasma creation. We present a range of pulsed plasma experiments conducted in neon, argon, helium, and mixtures of these gases, from 50-760 torr. Breakdown is achieved by illuminating a gas cell with a ~25kW, ~2 kV/cm, 800ns-long pulse as well as 41Hz pulse trains. Current results focus on preliminary experiments with metamaterial window coatings that indicate significant improvement opportunities for controlling breakdown thresholds and reducing breakdown delay. New results with gas mixtures in which observed breakdown occurs in
2012 Abstracts IEEE International Conference on Plasma Science, 2012
ABSTRACT form only given. Development of high power microwave (HPM) distributed discharge limiter... more ABSTRACT form only given. Development of high power microwave (HPM) distributed discharge limiters relies critically on minimizing the delay time between HPM incidence and diffuse plasma creation. We present a series of pulsed plasma experiments conducted in neon, argon, and a 9∶1 mixture of the two gases from 50–760 torr. Breakdown is achieved by illuminating a gas cell with a train of ∼25kW, ∼2 kV/cm, 800ns-long pulses at 41Hz repetition rate. The results suggest that surface charge accumulation on the gas cell&#39;s polycarbonate window from many low density precursor discharges eventually results in rapid (&lt;30ns), high density, discharge formation. The number of precursor pulses required to form these high density discharges is significantly reduced following a previous high-density discharge.
We present a formulation for achieving stable high-concentration (up to 20 mg/ml) aqueous dispers... more We present a formulation for achieving stable high-concentration (up to 20 mg/ml) aqueous dispersions of carbon nanotubes (CNTs) with exceptionally high microwave-frequency (0.5-6 GHz) dielectric properties. The formulation involves functionalizing CVD-synthesized CNTs via sonication in nitric and sulfuric acid. The overall chemical integrity of the CNTs is largely preserved, as demonstrated via physical and chemical characterizations, despite significant shortening and functionalization with oxygen-containing groups. This is attributed to the protected inner walls of double-walled CNTs in the samples. The resulting CNT dispersions show greatly enhanced dielectric properties compared to a CNT-free control. For example, at 3 GHz, the average relative permittivity and effective conductivity across several 20 mg/ml CNT samples were increased by ∼ 70% and ∼ 400%, respectively, compared to the control. These CNT dispersions exhibit the stability and extraordinary microwave properties desired in systemically administered theranostic agents for microwave diagnostic imaging and/or thermal therapy.
IEEE Transactions on Terahertz Science and Technology, 2012
ABSTRACT We present an experimental study of electromagnetic losses resulting from atmospheric at... more ABSTRACT We present an experimental study of electromagnetic losses resulting from atmospheric attenuation due to water vapor on 400 GHz radiation. A hermetically sealed, high quality factor quasi-optical resonator system permits the precise control of the atmospheric water vapor content, and allows for measurement of electromagnetic losses. The empirically determined losses are compared with predictions by various different electromagnetic attenuation models. Close agreement is demonstrated with four of the models, while another differs by more than an order of magnitude at higher values of water content.
Uploads
Papers by John Booske