arXiv subjects

Lekdar Gevorgian

Publications and source records attributed to Lekdar Gevorgian.

5 recordsLinked to original sources

arXiv2022

Advanced Radio Frequency Timing AppaRATus (ARARAT) Technique and Applications

The development of the advanced Radio Frequency Timer of electrons is described. It is based on a helical deflector, which performs circular or elliptical sweeps of keV electrons, by means of 500 MHz radio frequency field. By converting a time distribution of incident electrons to a hit position distribution on a circle or ellipse, this device achieves extremely precise timing. Streak Cameras, based on similar principles, routinely operate in the ps and sub-ps time domain, but have substantial slow readout system. Here, we report a device, where the position sensor, consisting of microchannel plates and a delay-line anode, produces ~ns duration pulses which can be processed by using regular fast electronics. A photon sensor based on this technique, the Radio Frequency Photo-Multiplier Tube (RFPMT), has demonstrated a timing resolution of ~10 ps and a time stability of ~0.5 ps, FWHM. This makes the apparatus highly suited for Time Correlated Single Photon Counting which is widely used in optical microscopy and tomography of biological samples. The first application in lifetime measurements of quantum states of graphene, under construction at the A. I. Alikhanyan National Science Laboratory (AANL), is outlined. This is followed by a description of potential RFPMT applications in time-correlated Diffuse Optical Tomography, time-correlated Stimulated Emission Depletion microscopy, hybrid FRET/STED nanoscopy and Time-of-Flight Positron Emission Tomography.

physics.ins-det↗

arXiv2022

An RF Timer of Electrons and Photons with the Potential to reach Picosecond Precision

This paper describes a new radio frequency timer of keV energy electrons. It is based on a helical deflector, which performs circular or elliptical sweeps of keV electrons, by means of 500 MHz radio frequency field. By converting a time distribution of incident electrons to a hit position distribution on a circle or ellipse, this device achieves extremely precise timing. Streak Cameras, based on similar principles, routinely operate in the ps and sub-ps time domain, but have substantial dead time associated with the readout system. Here, we report a new type of RF timing technique, where the position sensor, consisting of microchannel plates and a delay-line anode, produces ~ns duration pulses with small dead time. Measurements made with sub-ps duration laser pulses, synchronized to the radio frequency power, produced a timing resolution of ~10 ps. This ultra-high precision technique has potential applications in a large variety of scientific devices, and in all cases, electrons are timed and detected simultaneously in the same device.

physics.ins-det↗

arXiv2013

On the Possibility of Medium-Energy Compact X-ray Free-Electron Laser

The problem of X-ray Free-Electron Laser operating on self-amplified spontaneous emission in irregular microundulator is considered. The case when the spectrum width of spontaneous radiation is conditioned by the spatial distribution of sources creating the undulating field is considered. In this case gain function of the stimulated radiation is dozens of times higher than that of the conventional undulators. We propose a model of irregular microundulator, which can be used to construct a drastically cheap and compact X-ray free-electron laser operating on medium energy electron bunch.

physics.acc-ph↗

arXiv2012

Radiation of the electron bunch moving in non-regular fields

The problem of spontaneous radiation of the electron bunch grazing into a charged metallic surface with randomly distributed needle shaped asperities is considered. Distances between two neighboring asperities have been described by gamma distribution. Being repealed by highly charged asperities the electrons of the bunch move along non-regular periodical trajectories in the planes parallel to the metallic surface. The spatial periods of the trajectories are random quantities which are described by the same gamma distribution. The radiation characteristics of the bunch have been obtained. It is shown that the angular distributions of the number of photons radiated from the bunch and from a single electron are the same but the frequency distribution of the bunch is being drastically changed at the hard frequency region. It is proposed to develop a new non-destructive method for investigation of the metal surface roughness. The frequency distribution of the number of photons radiated under the zero angle has been obtained. That allows to find the gain expression of the stimulated radiation.

physics.class-ph↗

arXiv2011

Doppler effect in the oscillator radiation process in the medium

The purpose of this paper is to investigate the radiation process of the charged particle passing through an external periodic field in a dispersive medium. In the optical range of spectrum we will consider two cases: first, the source has not eigenfrequency, and second, the source has eigenfrequency. In the first case, when the Cherenkov radiation occurs, the non-zero eigenfrequency produces a paradox for Doppler effect. It is shown that the absence of the eigenfrequency solves the paradox known in the literature. The question whether the process is normal (i.e. hard photons are being radiated under the small angles) or anomalous depends on the law of the medium dispersion. When the source has an eigenfrequency the Doppler effects can be either normal or anomalous. In the X-ray range of the oscillator radiation spectrum we have two photons radiated under the same angle- soft and hard. In this case the radiation obeys to so-called complicated Doppler effect, i.e. in the soft photon region we have anomalous Doppler effect and in the hard photon region we have normal Doppler effect.

hep-ph↗