arXiv subjects

M. R. Mailian

Publications and source records attributed to M. R. Mailian.

6 recordsLinked to original sources

arXiv2015

Vibrating wires for beam diagnostics

A new approach to the technique of scanning by wires is developed. Novelty of the method is that the wire heating quantity is used as a source of information about the number of interacting particles. To increase the accuracy and sensitivity of measurements the wire heating measurement is regenerated as a change of wire natural oscillations frequency. By the rigid fixing of the wire ends on the base an unprecedented sensitivity of the frequency to the temperature and to the corresponding flux of colliding particles. The range of used frequencies (tens of kHz) and speed of processes of heat transfer limit the speed characteristics of proposed scanning method, however, the high sensitivity make it a perspective one for investigation of beam halo and weak beam scanning. Traditional beam profile monitors generally focus on the beam core and loose sensitivity in the halo region where a large dynamic range of detection is necessary. The scanning by a vibrating wire can be also successfully used in profiling and detecting of neutron and photon beams.

physics.ins-det↗

arXiv2014

Self-Organized Graphene/Graphite Structures Obtained Directly on Paper

We experimentally investigated the properties of graphite layers produced by an easy and non-conventional method of repeatedly rubbing conventional random stacked graphite bulk against insulating and semiconductor substrates. The patterned structure composed of rubbed-off and transferred layers exhibits properties of a solid-state material with through-thickness anisotropy of carrier mobility reaching ~10^3 cm^2/V*sec at the surface. The surface of the structure demonstrates quality of more ordered and optically oriented mono or few layer graphene shaped by self-organization process due to friction. Enhanced photoconductivity originating from modification of continuous and linear valence and conduction bands caused by interaction between 4 graphene layers made possible obtaining Raman spectra at near infrared excitation wavelength of 976 nm.

cond-mat.mtrl-sci↗

arXiv1999

Gravimetric Measurement of Magnetic Field Gradient Spatial Distribution

Magnetic interaction between a weighing sample and an external magnetic field allows to measure characteristics of magnetic field (a sample with known magnetic characteristics), as well as the magnetic properties of a sample (a known magnetic field). Measurement of materials magnetic permeability is a well known application of this method. In this paper we restrict ourselves to the measurement of magnetic field spatial distribution, which was achieved by scanning of samples from known materials along the vertical axis. Field measurements by Hall detector were done to calibrate obtained data. Such measurements are of great interest in some branches of physics, in particular, in accelerator physics, where the quality of magnetic system parts eventually determine the quality of accelerated bunches. Development of a simple and cheep device for measurement of magnetic field spatial distribution is an urgent problem. The developed system for gravimetric measurement of magnetic field gradients partially solves this problem.

physics.acc-ph↗

arXiv1999

Vibrating Wire for Beam Profile Scanning

The method for measurement of transverse profile (emittance) of the bunch by detecting of radiation arising scattering at of the bunch on the scanning wire is wide-spread. In this work the information about scattering bunch is proposed to measure using the oscillation frequency of the tightened scanning wire. In such way the system of radiation (or secondary particles) extraction and measurement can be removed. Dependence of oscillations frequency on beam scattering is determined by several factors, including changes of wire tension caused by transverse force of the beam, influence of beam self field. Preliminary calculations show that influence caused by wire heating will dominate. We have studied strain gauges on the basis of vibrating wire from various materials (tungsten, beryl bronze, niobium zirconium alloys). A scheme of self oscillations generation by alternating current in autogeneration circuit with automatic frequency adjustment was selected. Special method of wire fixation and elimination of transverse degrees of freedom allow to achieve relative stability better than 1E-5 during several days. For a tungsten wire with a fixed end dependence of frequency on temperature was 1E-5/K. Experimental results and estimates of wire heating of existing scanners show, that the wire heats up to a few hundred grades, which is enough for measurements.

physics.acc-ph↗

arXiv1998

Two-dimensional Stationary Wake Fields in Vortexfree Cold Plasma. I

Present paper is devoted to formulation of the system of the master equations of the problem and analytical considerations of the limiting cases, which have an exact solutions (transversal and longitudinal flat bunches, linear approxim- ation). Presented consideration gives some hints to the construction of proper algorithm for numerical calculations.

physics.acc-ph↗

arXiv1997

Generator-Invertor-Dumper System of Electron (Positron) Bunches Moving in Cold plasma for Development of Strong Accelerating Electric Field

It is shown that high accelerating gradient can be obtained in a specially constructed system of electron (positron) bunches, moving in cold plasma,with definite density. These combined bunch systems do not generate the wake fields behind them and can pass through the plasma column in a periodic sequence. The consideration is carried out numericaly and analyticaly in one dimensional approach, (which can be applied to finite system when its transverse dimensions are larger than plasma wave length, divided by $2π$). The possibilities of the experimental tests by measuring the predicted energy gain are discussed on the examples of Argonne Wakefield Accelerator and induction linac with typical parameters.

physics.acc-ph↗