Moshe Einat

Lifetime of ferroelectric Pb(Zr, Ti)O3 ceramic cathodes with high current density

Electron emission from ferroelectric cathodes is investigated, it is commonly suggested as an electron source for different applications due to its special characteristics such as high current density, easy treatment, and operation. In this experimental research, a lifetime of lead zirconate-titanate ceramic cathode with composition related to a ferroelectric phase was studied. The strong plasma emission from the cathode was excited in a nonreversal (nonswitching) mode by application of unipolar high stress. Severe damage to the cathodes was observed, especially in a high repetition rate. An upper limit of the lifetime of the ferroelectric cathode with plasma-induced emission was estimated at about ∼106 pulses of ∼200 ns each at ∼100 Hz repetition rate. Possible applications of the limited lifetime ferroelectric cathode are discussed.

Demonstration of microwave generation by a ferroelectric-cathode tube

A ferroelectric cathode is employed in a cyclotron-resonance maser (CRM). The CRM oscillator device operates at similar to 7 GHz, near the cutoff frequency of a hollow cylindrical cavity. The cathode is made of a PLZT 12/65/35 ceramic with high-dielectric constant (epsilon(r)similar to 4000). Electrons are extracted from the plasma excited on the cathode surface by similar to 1 kV short rise-time pulses. The use of ferroelectric cathodes may advance the microwave tube technology for various applications

Detecting Hidden Objects on Human Body Using Active Millimeter Wave Sensor

The paper describes millimeter wave (MMW) sensors designed for detecting both metallic and nonmetallic objects placed on a human body and hidden under clothes. The sensor is based on the synchronized detection principle and estimating a power of back-scattered signal from hidden objects. Time-gating algorithm combined with preliminary determined threshold level has been implemented in order to reach detection probability of ~ 90% or more for metal and plastic hidden objects at the distance up to 3 m.

High-repetition-rate ferroelectric-cathode gyrotron

The intensive research on ferroelectric electron-emission mechanisms in the last decade has resulted in a wide understanding of the physics and characteristics of this plasma-assisted electron source. Nevertheless, practical devices employing this cathode were hardly introduced. In this experimental study, a high-repetition-rate microwave oscillator based on a ferroelectric electron gun has been developed. The device operates as a cyclotron-resonance maser in the gyrotron mode. Microwave pulses exceeding 1.5 kW at ∼7 GHz are measured in repetition rates above 3 MHz and duty cycles of ∼50%. These experimental results encourage the implementation of ferroelectric cathodes in practical high-power microwave tubes.

A ferroelectric electron gun in a free-electron maser experiment

An electron-gun based on a ferroelectric cathode is studied in a free-electron maser (FEM) experiment. In this gun, the electrons are separated from the cathode surface plasma, and are accelerated in two stages. The electron energyspread is reduced sufficiently for an FEM operation in the microwave regime. A 14 keV, 1–2 A e-beam is obtained in a 0.1–2.1ms pulse width. The pulse repetition frequency attains 3.1 MHz in B50% duty-cycle. This gun is implemented in an FEM oscillator experiment operatingaround 3 GHz. The paper presents experimental results and discusses the applicability of ferroelectric guns in free-electron laser devices. r 2002 Elsevier Science B.V. All rights reserved.

Two-dimension full array high-speed ink-jet print head

An ink-jet print head in a structure, similar to a liquid crystal display, is suggested. It is based on a segment, containing a microink reservoir, feeding one or a few nozzles. The segment is autonomous and unlimitedly duplicable to form a large ink-jet print head. The microreservoirs are open to the atmospheric pressure, and pressure regulation in the nozzle is accomplished by capillary action. The microreservoirs are replenished by slow wiper smearing action. Experiments with a 57600 nozzle matrix print head showed good results for the design. Printing speed of ∼1000pagesmin, and even more, is achievable.

Spectral measurements of gyrotron oscillator with ferroelectric electron gun

Since the discovery of the ferroelectric electron-emission effect, its implementation in microwave tubes has been impeded by various reasons and in particular by its relatively wide energy spread. Recently, a 1.5 kW microwave output from a gyrotron based on repetitive ferroelectric electron gun has been reported. This letter presents measurements of the spectral variations of the gyrotron output, and relates them to the electron-gun energy spread and to other inherent line-widening causes, such as the pulse length. The result shows that the contribution of the electron energy spread to the spectral content is not significantly larger than the other causes of line broadening.

Non-Imaging MM-Wave FMCW Sensor for Pedestrian Detection

This paper describes a millimeter-wave sensor that is able to detect pedestrians, thereby reducing the likelihood of human road injuries or fatalities. The sensor consists of a transmit/receive channel module, operating in the millimeter-wave range (W-band) using frequency-modulated-continuous-wave mode. The laboratory prototypes of the sensor have been designed and tested in real-life environment. An analysis of system performance and experiments conducted has indicated a high-resolution, detection ability of both adults and children at a distance of up to 100-150 m.

Gyrotron With Dual Electrode Ferroelectric Cathode Operating at High Repetition Rate and Long Pulse

A gyrotron based on a ferroelectric cathode with dual front electrodes has been experimentally studied, and the results are reported. The two electrodes are triggered separately with complementary timing. During operation when plasma is forming on one of the electrodes, the other undergoes a relaxation process and vice versa. A pulse repetition rate of ~ 3 MHz with a 50% duty cycle was obtained from each electrode, reaching an overall 100% duty cycle, forming a continuous ~ 7-μs current pulse. This configuration has the potential to extend the pulse duration toward continuous operation. The cathode was used as a source for a 25-GHz gyrotron generating a ~ 7-μs radiation pulse.

Induced static magnetic field by a cellular phone

Recent claims regarding the safety of cellular phones suggest that weak static magnetic fields are induced around the phone, and this field and its gradients may pose a health risk to the user. An experiment was conducted to measure the induced static magnetic field around a cellular phone. 65 μT variations and 18 μT/cm gradients were measured in the magnetic field at 6 cm from the phone. An analytical model is derived to explain the results. The influence that the measured magnetic fields may have on the user is beyond the scope of this research.