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Radiofrequency Coherent Radiation of Particles

#A-691


Coherent Radiation Produced by Bunches of Particles in the Radio Frequency Region

Tech Area / Field

  • PHY-RAW/Radiofrequency Waves/Physics
  • PHY-PFA/Particles, Fields and Accelerator Physics/Physics

Status
3 Approved without Funding

Registration date
12.03.2001

Leading Institute
A.I. Alikhanyan National Science Laboratory, Armenia, Yerevan

Collaborators

  • University of Wisconsin-Madison, USA, WI, Madison\nArray\nUniversity of California, USA, CA, Los-Angeles\nCatholic University of America, USA, DC, Washington

Project summary

In accordance with the purposes of ISTC in this Project it is suggested to form a new scientific and exploratory group from the scientists and engineers, working in Yerevan Physics Institute (YerPhI) with the purpose to perform works on 1) The theory of coherent radio radiation (CRR) produced by electron and photon bunches with energies 10 MeV – 20 TeV in radio wave region; 2) The design and construction of an experimental arrangement and the investigation of various types of radiation in centimeter-meter wavelength regions produced by 20 MeV, 50 MeV electron and photon bunches.

The main purpose of all these works is to verify and develop the theoretical and experimental understanding of the processes which allow using arrays of RF antennas to detect super high energy neutrinos passing through the Earth and producing electromagnetic showers and coherent radio radiation in Antarctic ice. Besides the well-known applications of CRR for the measurement of the characteristics of charged particle beams, CRR can be used also for distant cosmic communications due to its mach smaller angular pergence compared with the radiation from usual antennae. Some preliminary results of the planned works have been presented and discussed in the First International Workshop on Radio Detection of High Energy Particles, RADHEP-2000, Los Angeles, USA.

The theoretical works will be devoted to: 1a) The first calculations of the coherent forward transition radiation (TR) fields and intensity when the distance from the interface between two media with different dielectric constants and the detector is less or of the order of the TR formation length; 1b) The analytic calculations of the spontaneous radiation produced by the moving negative charge excess of the high energy electromagnetic showers using the fitted dependence of the charge excess on the distance; 1c) The study of spontaneous TR or resonance radiation (RR) produced by bunches of particles in a stack of plates under certain resonance conditions; 1d) The theoretical investigation of the coherent stimulated TR and Cherenkov radiation (CR) under the influence of the field of TR and CR photons produced by the previous bunches and returned with the help of wave-guide system ; 1e) The influence of the transversal sizes of the radiator on the intensity of the produced TR and 1f) The calculation of the radiation produced in stochastically inhomogeneous media for the radio wave region when the radiation wave lengths are larger than the dimension of the inhomogeneities. 1g) Interference between different kinds of radiation of high-energy particle; TR, Synchrotron Radiation, Cherenkov Radiation etc.

The experimental works will be devoted to: 2a) The measurements of the dependence of the intensity of the detected TR photons upon the distance between the thin metallic and dielectric radiators and the detector; 2b) The measurements of the angular and spectral distributions of the radiation produced by a sequence of electron and photon bunches in different radiators; 2c) The experimental study of RR produced by charged bunches in certain stack of plates when resonance conditions are fulfilled; 2d) The dependence of the stimulated TR and CR upon various parameters will be measured and compared with the theoretical predictions and 2e) The dependence of the TR intensity upon the transversal sizes of the radiator.

The state of art in the above mentioned fields can be described in the following way. 1, 2a) It is strange, but it is a fact that the detectable intensity of the simple TR, when the distance between the radiator and detector is less and of the order of the formation length, is not quantified theoretically and experimentally. It is only said that the TR intensity in the case of above described conditions will be suppressed because the TR photons are aborted before their formation. There are only two published theoretical works and, first of which shows the important role of the particle charge field, while the second is devoted only to the backward TR. Experimentally it has been shown recently that for 15 MeV electrons the intensity of TR photons with wave lengths 10-20 cm measured at distances about 1 m is suppressed about 30 times with respect to the theoretical estimates for wave zone. The aim of the tasks 1,2 a) is the explanation of this discrepancy, the calculation and the measurement of TR intensity dependence on the observation distance.
In the case of 1,2b) the calculations and measurements of the angular and spectral distributions of the radiation produced by a sequence of electron bunches in thick dielectric radiators have been carried out analytically and numerically. However, the analytical calculations have been performed for some model development of the shower, while the Monte Carlo simulations assume an instant appearance and disappearance of the negatively charged particles. Therefore, it is necessary to carry out new 1b) analytic calculations of the radiation with the help of more realistic shower development models and compare them with the Monte Carlo results. New experimental results 2b) are necessary in order to confirm the results of the above-mentioned experiment.

Study of CRR in the 10 – 20 cm wavelength region produced by charged bunches in certain stacks of plates when resonance conditions are fulfilled 1,2c) is of interest because it is they can show the possibility of using CRR for distant telecommunication purposes.

The stimulated TR is experimentally studied only in the FIR region. Our planned theoretical 1d) and experimental works 2d) will reveal the application possibilities of this process.

The predicted new effect on the suppression of TR intensity when the transversal sizes of the radiator is less than the so called transversal sizes of the TR sources is still not verified experimentally and can be very important for various applications of CRR. Therefore it is important to carry out 1e) and 2e) works devoted to the study of this effect.

The study of the coherent TR produced in clouds, as well as in inhomogeneities of ice is important for the above mentioned cosmic ray application of CRR.

The planed experimental works will be carried out using the existing in YerPhI 20-50 MeV electron beams as well as dipole and horn antennae.

The YerPhI physicists, who will take part in the given Project have many years experience of working in the fields of radiation theory, accelerator technology, and detection methods of particle and radiation in a wide spectral region. Their achievements in these fields are well known over all world, since many fundamental works on the theory and experiment of the radio-,optical- and x-ray transition radiation were performed in YerPhI for the first time. The foreign collaborators of the Project have great achievements in the above mentioned regions for the first time applying subpicosecond beams of Argone Wakefield accelerator (15 MeV) and of SLAC (up to 30 GeV) for obtaining first results on CRR (coherent TR and Cherenkov radiation) in radio-frequency (10 – 20 cm) region. They will exchange their information and experience with YerPhI physicist.

The Project is for 36 months, total person-months are 300 and the total estimated cost is 200 000 US$. The plan of the works is organized in such a way that the theoretical and numerical works will be carried out almost always, while the construction works will follow design efforts and linear accelerator schedule. It is expected that the first experimental results on the investigation of the above mentioned radiation's will be obtained in the 5-th quarter.

The proposed Project corresponds to ISTC instructions and aims and gives possibility to scientists from YerPhI engaged in military projects in USSR for further collaboration with International Scientific Community.


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