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Papers by Samer Banna

It is proposed to utilize the diffraction radiation emitted by an electron traversing an array of... more It is proposed to utilize the diffraction radiation emitted by an electron traversing an array of metallic posts for deducing the electron's displacement from the symmetry axis of the structure. In other words, it is proposed to use such an array as a beam position monitor (BPM). The structure consists of a set of N × N metallic vertical posts bounded from above and below by two horizontal metallic plates. The beam position offset from the symmetry axis is determined by measuring the backward radiation emitted by the beam as it traverses the array. The position resolution of the suggested BPM is dominated by the noise level of the detectors used for measuring the radiation, whereas the time resolution is dominated by their operation frequencies.

Bulletin of the American Physical Society, Oct 5, 2010

Conventional industrial ICP sources for dry etching processes suffer inherently from the so-calle... more Conventional industrial ICP sources for dry etching processes suffer inherently from the so-called M-shape etch rate (ER) pattern across the wafer. Such M-shape limits significantly the ER uniformity and the depth range of shallow trench isolation processes which are detrimental for ...

Physical Review E Statistical Nonlinear and Soft Matter Physics, Nov 1, 2006

The interaction of electromagnetic radiation with free electrons in the presence of an active med... more The interaction of electromagnetic radiation with free electrons in the presence of an active medium has some appealing outcomes. Among them is particle acceleration by stimulated emission of radiation (PASER). In its framework, energy stored in an active medium (microscopic cavities) is transferred directly to an e -beam passing through. We have developed a two-dimensional analytic model for the evaluation of the energy exchange occurring as a train of electron microbunches traverses a dilute resonant medium. Efficient interaction occurs at resonance—namely, when the frequency of the train matches the resonance frequency of the medium. It is shown that the energy exchange is γ independent for relativistic energies and it drops dramatically with an increase of the beam’s radius. Based on this model, we have evaluated the relative change in the kinetic energy of a 0.1-nC 45-MeV macrobunch traversing an excited CO2 gas mixture—the former being modulated at the CO2 laser wavelength. Good agreement is found between the theoretical predictions and the results of the PASER experiment performed recently at Brookhaven National Laboratory.

Journal of Applied Physics, Apr 14, 2004

In this study we investigate the properties of the electromagnetic wake-field generated by an ele... more In this study we investigate the properties of the electromagnetic wake-field generated by an electron bunch moving in the vicinity of an optical structure of finite roughness. The model employed consists of a metallic cylindrical waveguide to which grooves of random width, height, and location are attached. Based on this model analytic expressions have been developed for the average energy emitted per groove and for its standard deviation. As expected, both quantities are virtually independent of the momentum in a highly relativistic regime and the average energy emitted per groove is proportional to the roughness parameter. Moreover, it has been found that the standard deviation of the energy emitted per groove is proportional to the standard deviation of the roughness parameter to the power of 1/4. The cumulative effect of surface roughness was studied resorting to both periodic and quasiperiodic structures—significant differences in the spectrum have been observed only for low frequencies.

Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999

We report first experiments on high-power traveling wave amplifiers using an electron beam genera... more We report first experiments on high-power traveling wave amplifiers using an electron beam generated with a ferroelectric cathode. The electron beam, which is driven by a ferrite core transformer-pulse line system, has energy of 440 keV and a beam current of 40-50 Amperes. The beam pulse duration is about 250 ns and the system is operated at 0.07 Hz. The beam is generated from a command switched ferroelectric cathode located in the fringing field of a solenoid. A single stage disk loaded TWT structure is used as thẽ 9GHz amplifier. A gain of 10 dB is observed over the frequency range from 8.9 to 9.4 GHz. The main purpose of the experiment is to demonstrate that the ferroelectric generated beam is of good enough quality for microwave amplification in X band, and to pave the way for use of this cathode in future high power microwave source experiments. We compare the results obtained using this system with the output from a PIC code simulation.

The effect of the surface roughness on a moving electron bunch is considered by resorting to a mo... more The effect of the surface roughness on a moving electron bunch is considered by resorting to a model of a metallic structure with random perturbations on its surface. Based upon this model, analytic expressions have been derived for the average energy emitted per groove (EPG) and for its standard deviation. For a relativistic bunch, both quantities are shown to be virtually independent of the momentum. Moreover, it has been found that the standard deviation of the EPG is proportional to that of the roughness parameter to the power of 1/4. © 2004 American Institute of Physics

It is proposed to utilize the diffraction radiation emitted by an electron traversing an array of... more It is proposed to utilize the diffraction radiation emitted by an electron traversing an array of metallic posts for deducing the electron's displacement from the symmetry axis of the structure. In other words, it is proposed to use such an array as a beam position monitor (BPM). The structure consists of a set of N × N metallic vertical posts bounded from above and below by two horizontal metallic plates. The beam position offset from the symmetry axis is determined by measuring the backward radiation emitted by the beam as it traverses the array. The position resolution of the suggested BPM is dominated by the noise level of the detectors used for measuring the radiation, whereas the time resolution is dominated by their operation frequencies.

Bulletin of the American Physical Society, Oct 5, 2010

Conventional industrial ICP sources for dry etching processes suffer inherently from the so-calle... more Conventional industrial ICP sources for dry etching processes suffer inherently from the so-called M-shape etch rate (ER) pattern across the wafer. Such M-shape limits significantly the ER uniformity and the depth range of shallow trench isolation processes which are detrimental for ...

Physical Review E Statistical Nonlinear and Soft Matter Physics, Nov 1, 2006

The interaction of electromagnetic radiation with free electrons in the presence of an active med... more The interaction of electromagnetic radiation with free electrons in the presence of an active medium has some appealing outcomes. Among them is particle acceleration by stimulated emission of radiation (PASER). In its framework, energy stored in an active medium (microscopic cavities) is transferred directly to an e -beam passing through. We have developed a two-dimensional analytic model for the evaluation of the energy exchange occurring as a train of electron microbunches traverses a dilute resonant medium. Efficient interaction occurs at resonance—namely, when the frequency of the train matches the resonance frequency of the medium. It is shown that the energy exchange is γ independent for relativistic energies and it drops dramatically with an increase of the beam’s radius. Based on this model, we have evaluated the relative change in the kinetic energy of a 0.1-nC 45-MeV macrobunch traversing an excited CO2 gas mixture—the former being modulated at the CO2 laser wavelength. Good agreement is found between the theoretical predictions and the results of the PASER experiment performed recently at Brookhaven National Laboratory.

Journal of Applied Physics, Apr 14, 2004

In this study we investigate the properties of the electromagnetic wake-field generated by an ele... more In this study we investigate the properties of the electromagnetic wake-field generated by an electron bunch moving in the vicinity of an optical structure of finite roughness. The model employed consists of a metallic cylindrical waveguide to which grooves of random width, height, and location are attached. Based on this model analytic expressions have been developed for the average energy emitted per groove and for its standard deviation. As expected, both quantities are virtually independent of the momentum in a highly relativistic regime and the average energy emitted per groove is proportional to the roughness parameter. Moreover, it has been found that the standard deviation of the energy emitted per groove is proportional to the standard deviation of the roughness parameter to the power of 1/4. The cumulative effect of surface roughness was studied resorting to both periodic and quasiperiodic structures—significant differences in the spectrum have been observed only for low frequencies.

Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999

We report first experiments on high-power traveling wave amplifiers using an electron beam genera... more We report first experiments on high-power traveling wave amplifiers using an electron beam generated with a ferroelectric cathode. The electron beam, which is driven by a ferrite core transformer-pulse line system, has energy of 440 keV and a beam current of 40-50 Amperes. The beam pulse duration is about 250 ns and the system is operated at 0.07 Hz. The beam is generated from a command switched ferroelectric cathode located in the fringing field of a solenoid. A single stage disk loaded TWT structure is used as thẽ 9GHz amplifier. A gain of 10 dB is observed over the frequency range from 8.9 to 9.4 GHz. The main purpose of the experiment is to demonstrate that the ferroelectric generated beam is of good enough quality for microwave amplification in X band, and to pave the way for use of this cathode in future high power microwave source experiments. We compare the results obtained using this system with the output from a PIC code simulation.

The effect of the surface roughness on a moving electron bunch is considered by resorting to a mo... more The effect of the surface roughness on a moving electron bunch is considered by resorting to a model of a metallic structure with random perturbations on its surface. Based upon this model, analytic expressions have been derived for the average energy emitted per groove (EPG) and for its standard deviation. For a relativistic bunch, both quantities are shown to be virtually independent of the momentum. Moreover, it has been found that the standard deviation of the EPG is proportional to that of the roughness parameter to the power of 1/4. © 2004 American Institute of Physics

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