A. Shahadi

Increased Levels of Numerical Chromosome Aberrations after In Vitro Exposure of Human Peripheral Blood Lymphocytes to Radiofrequency Electromagnetic Fields for 72 Hours

Abstract Mazor, R., Korenstein-Ilan, A., Barbul, A., Eshet, Y., Shahadi, A., Jerby, E. and Korenstein, R. Increased Levels of Numerical Chromosome Aberrations after In Vitro Exposure of Human Peripheral Blood Lymphocytes to Radiofrequency Electromagnetic Fields for 72 Hours. Radiat. Res. 169, 28–37 (2008). We investigated the effects of 72 h in vitro exposure of 10 human lymphocyte samples to radiofrequency electromagnetic fields (800 MHz, continuous wave) on genomic instability. The lymphyocytes were exposed in a specially designed waveguide resonator at specific absorption rates (SARs) of 2.9 and 4.1 W/kg in a temperature range of 36–37°C. The induced aneuploidy of chromosomes 1, 10, 11 and 17 was determined by interphase FISH using semi-automated image analysis. We observed increased levels of aneuploidy depending on the chromosome studied as well as on the level of exposure. In chromosomes 1 and 10, there was increased aneuploidy at the higher SAR, while for chromosomes 11 and 17, the increases were observed only for the lower SAR. Multisomy (chromosomal gains) appeared to be the primary contributor to the increased aneuploidy. The effect of temperature on the level of aneuploidy was examined over the range of 33.5–40°C for 72 h with no statistically significant difference in the level of aneuploidy compared to 37°C. These findings suggest the possible existence of an athermal effect of RF radiation that causes increased levels of aneuploidy. These results contribute to the assessment of potential health risks after continuous chronic exposure to RF radiation at SARs close to the current levels set by ICNIRP guidelines.

Free-electron maser oscillator experiment in the UHF regime

A nonrelativistic electron beam (< 4 keV) travels in this experiment in a non-dispersive waveguide along a planar undulator and an axial magnetic fields. The electron beam has a Gaussian pulse shape with a 1 ms pulse width. Two distinct radiation bursts are observed during the electron energy sweep. Each burst contains a different range of microwave frequencies. One burst corresponds to the FEM interaction, at ∼ 0.8 GHz. The other burst corresponds to the cyclotron resonance interaction, at ∼ 5 GHz. This experiment demonstrates an FEM operation in an extremely long wavelength (37.5 cm) in the UHF regime.

Cyclotron maser oscillator experiments in a periodically loaded waveguide

The periodic-waveguide cyclotron maser is a device in which orbiting, nonrelativistic electrons interact with traveling waves in a metallic, periodically loaded waveguide. In this paper, we describe a table-top oscillator experiment that operates in the microwave regime (9.4 GHz) with a low-energy (8 keV), low-current (0.2 A) electron beam pulse (1 ms pulse width). The frequency modulation (chirping) observed is used in the determination of cyclotron resonance condition for this interaction. The results show that the cyclotron interaction occurs with a backward-propagating wave in the periodically loaded waveguide. Microwave power of /spl ges/0.3 kW and efficiency of /spl ges/20% are measured by an external loading of the oscillator. >

Dielectric-loaded free-electron maser in a stripline structure

Abstract Experimental results of a dielectric-loaded free-electron maser (FEM) oscillator in a stripline structure are presented. The table-top oscillator experiment employs a low-energy electron beam (8 keV, 0.5 A) and a folded-foil wiggler (2 cm period). The waveguide consists of dielectric slabs and metal striplines along the side walls of a rectangular tube. The metallic striplines protect the dielectric slabs attached to them from the electron beam, and support a quasi-TEM mode in the waveguide. The effective dielectric constant of the dominant odd quasi-TEM mode is measured as e eff ≅ 8. The oscillator operates in a frequency range of 3–5 GHz, in agreement with the tuning relation of the slow-wave dielectric-loaded free-electron maser.

Low-cost electron-gun pulser for table-top maser experiments

Abstract A simple 10 kV electron-gun pulser for small-scale maser experiments is presented. This low-cost pulser has operated successfully in various table-top cyclotron-resonance maser (CRM) and free-electron maser (FEM) experiments. It consists of a low-voltage capacitor bank, an SCR control circuit and a transformer bank (car ignition coils) connected directly to the e-gun. The pulser produces a current of 3 A at 10 kV voltage in a Gaussian like shape of 1 ms pulse width. The voltage sweep during the pulse provides a useful tool to locate resonances of CRM and FEM interactions. Analytical expressions for the pulser design and experimental measurements are presented.

Carbon-fiber emitter in a cyclotron-resonance maser experiment

Abstract A compact cyclotron-resonance oscillator which employs a carbon-fiber electron-gun is presented in this paper. The maser oscillates at ∼3 GHz frequency near the electron cyclotron-resonance. The 2mm diameter carbon-fiber cathode emits ∼1 A current at ∼1 kV voltage. The electron beam tends to be unstable. Clear bursts of RF oscillations are observed in this experiment.

Cyclotron resonance maser experiment in a non-dispersive waveguide

Abstract A cyclotron-resonance maser (CRM) experiment with a transverse electromagnetic (TEM) wave is presented in this paper. A nonrelativistic electron beam is spiraling in this device in a non-dispersive parallel-line waveguide. The CRM oscillator output frequency is tuned by the axial magnetic field in the range of 3.2–4.8 GHz.

Cyclotron resonance maser experiment in a nondispersive waveguide

A cyclotron-resonance maser (CRM) oscillator experiment in which a spiraling electron beam interacts with a transverse electromagnetic wave in a nondispersive waveguide is presented. The experiment employs a low-energy (<5 keV) low-current (<1 A) electron beam in a two-wire (Lecher type) waveguide. The microwave output frequency is tuned in this experiment by the axial magnetic field in the range 3.5-6.0 GHz. A second harmonic emission is observed at /spl sim/7 GHz. CRM theory shows that in a free-space TEM-mode interaction, the gain might be canceled due to the equal and opposite effects of the axial (Weibel) and the azimuthal bunching mechanisms. This balance is violated in the large transverse velocity regime (V/sub /spl perp///spl Gt/V/sub z/) in which our experiment operates. The tunability measurements of the CRM oscillator experiment in the nondispersive waveguide are discussed in view of the CRM theory.

Backward-wave cyclotron maser oscillator experiment

A backward-wave cyclotron maser oscillator experiment conducted at Tel Aviv University is reported in this paper. The oscillator operates in the microwave regime (9.4 GHz) with a low- energy electron beam pulse (8 keV, 0.2 A, 1 ms). A frequency chirping effect observed by a heterodyne technique reveals the cyclotron resonance with a backward wave harmonic of the periodic waveguide.

Cyclotron maser experiment in a 2D periodic waveguide

The experimental study of a cyclotron-resonance maser (CRM) in a 2D periodic-waveguide is reported. Using a low-energy electron beam (/spl sim/5 keV, 0.1 A), the experiment is operated in microwave-frequency around 7 GHz in an axial magnetic field (/spl sim/3 kG). The corresponding efficiency is /spl sim/10%. This experiment is a first stage in the development of a new CRM-array concept.