مجله پژوهش فیزیک ایران
سال هفدهم شماره 2 (بهار 1396)

Particle accelerators are engines of discovery and innovation. Design, construction and use of particle accelerators have made numerous scientific and technological achievements in recent decades, having an undeniable influence on society. In medicine and pharmacy, particle accelerators provide in more efficient treatment with fewer side effects. Disease diagnostics are how much straightforward with the help of radio isotopes, accelerators have made it possible to develop new antibiotics with providing the ground for research in molecular biology and discovering new protein structures and live cells. Accelerators also provide better quality electrical microchips for the market, by processing and producing semiconductors. They provide cleaner water and air by helping in research on pollutants and have unexampled achievements in archaeology and archaeometry. Today, there are more than 35 thousand accelerators of different types around the world from which 65% are working in industry, more than 30% in medicine and about 5% in large-scale laboratories and research centers. Considering various applications of accelerators in different scientific and engineering fields, developing different types of accelerators and introducing their different applications to the scientific society, can result in developing industrial potency, enhancing economic power and even improving life in the society. Large-scale facilities have always been the target of the best researchers and scientists around the world in different fields of studies, with the purpose of conducting the most advanced scientific projects. Some beneficiary companies and science institutions employing new strategies will develop from those projects. Of course, the management and financing methods will be new and different in such laboratories. Iran, a country of about 85 million populations with an outstanding scientific quality in the Middle-East, has had a poor record in the use of particle accelerators. Nearly 5 million students are studying in 470 universities, 2 million are studying in basic science, engineering and medicine. Such a big number of students and researchers have little access to particle accelerator laboratories, as a modern and efficient tool for research and innovation. The most optimistic estimation has counted 50 accelerators being utilized by Iranian researchers in medical applications, and just two to three accelerators are being used for non-medical purposes, while the first laboratories of this kind have been employed more than 40 years ago in Europe and USA, and are being exploited more widely each day. Without enough laboratories and experimental tools, new generations of researchers would not have an appropriate grasp of measurement and experimental science. It can be stated that the most important reason for this lag in developing accelerators technology is the absence of recognition and enough motivation on the part of universities and scientific institutions, not the lack of scientific qualification. It should be noted that scientific capability of Iran is now envied by many developed countries, those who have enough hardware but are in need of young researchers for utilizing and scientific management of these laboratories. The lack of attention and delaying in setting up scientific plans, such as Iranian Light Source Facility (ILSF), and similar projects deprives the country from the opportunity of attracting the best graduates and scientists. Building large scale facilities for such a huge human capacity in the country, would enable educated and talented individuals to seek better and professional opportunities in our country and to stop " Brain drain" to occur. Constructing a national large-scale laboratory, such as Iranian Light Source Facility (ILSF) targeted for interdisciplinary research, with no doubt enhances the quality of research in Iran. Furthermore, it should be pointed out that new political condition after resolving sanction against Iran should concentrate more on scientific and technological independence and self-sufficiency of the country and prevent from over purchasing form abroad. Organizers of the second national conference on particle accelerators and their applications, endeavor to demonstrate a precise and genuine picture of what is going on in Iran regarding construction and application of particle accelerators, to connect researchers and to encourage commercial companies to assist Iranian researchers in developing accelerator science and technology. It is hoped that in the near future, Iran experience a productive period in producing science and technology, especially in constructing and applying particle accelerators. We invite all scientists, from all over the country, as well as Iranian experts working abroad, working up in this area, to this national gathering. The availability of educated individuals at the present scale in Iran is indeed exceptional. This is a unique opportunity which should not be missed by science policy makers at the political levels.

Storage rings are extensively used for particle colliders, damping rings and light sources. To further increase the luminosity at the colliders or brightness of a synchrotron light sources, the emittance of accelerator beam is being continually pushed downward in storage rings. In this paper, we investigate the lattice design for the storage ring of Iranian Light Source Facility (ILSF) with an ultra-low emittance of 0.27 nm-rad, intermediate energy of 3 GeV and storage ring circumference of 528 m. In this design, the base line for installing adjuncts is based on 20 straight sections with the length of 7 m.

Iranian Light Source Facility (ILSF) is a new 3 GeV synchrotron radiation laboratory in the Middle East. The ILSF storage ring (SR) is based on a Five-Bend Achromat lattice, providing a beam emittance of 0.48 nm rad. The ring is consisting of 100 pure dipole, 320 quadrupole and 320 sextupole magnets. In this paper, we present some design features of the SR magnets and discuss their detailed physical design

Magnetic Measurement Lab is one of the most significant divisions of Research and Development (R&D) Lab of Iranian Light Source Facility. The main duty of this lab is to measure and check qualification of the accelerator magnets, including permanent and electromagnets, being applied in Iran for the fisrt time. The ILSF measurement lab consists of precise measurement equipment, in proportion to synchrotron needs, such as Hall Effect probe measurement bench, rotating coil and Helmholtz coil. Recently, the lab has been provided with Hall probe measurement bench and uncompensated rotating coil and has made it possible to measure prototype magnets. In this article, the results of measuring quadrupole prototype are studied using Hall probe and rotating coil, to determine and compare errors in measuring multipole magnets and their sources

Iranian Light Source Facility (ILSF) RF system was conceptually designed based on ILSF requirements for a 3 GeV storage ring and 400 mA beam current at 500 MHz RF frequency. Considering the fact that cavity construction is simpler at 100 MHz and advantages of reducing frequency provided an alternative of 100MHz RF system to be explored for ILSF. After a thorough study on the effect of reducing RF frequency on electron beam, machine parameters and comparison of RF systems at both frequencies, the RF frequency was switched to 100 MHz. This paper presents these investigations and comparision leading to selecting the intended frequency. Furthermore, the electromagnetic and mechanical design for 100 MHz cavity are discussed.

The Iranian Light Source Facility (ILSF) booster main specifications including 250 ms ramp up, 2Hz repetition rate, and quasi-sinusoidal wave shape, up to this point have been the basis for calculations. Each family of magnets including Dipole, Quadrupole and Sextupoles will feed by individual power supply. In order to maintain constant transverse tunes and chromaticity while the beam is accelerated, quadrupole and sextupole magnet currents must closely track the current in the dipole magnets. In booster rings, feeding the high inductance load, tracking of Quadrupole and sextupole magnets, reducing output current fluctuation and having a precise high bandwidth current regulation system are particular challenges. In order to meet the requirements, it is necessary to have a fully digital controller to achieve a fast regulation system. The prototype power supply and its test results are described in this paper.

In this paper, we have discussed about the role of two emittance values suggested for Iranian Light Source Facility (ILSF) (3.278 and 0.476 nm.rad) on different radiation features of the synchrotron light sources (bending magnet, shaker and oscillator) such as spot size, divergence of the beam on light spot, brilliance and important quantities in beamline design such as photon cross-section, optical element sizes and energy resolution

Design and construction process of special kind of sputter ion pump is described briefly in this paper. In order to investigate the optimization of effective parameters in choosing and designing ILSF ion pumps, this pump has been designed and manufactured. By optimizing some parameters such as dimension and shape of penning cells, anode voltage, magnetic field and internal structure of pump, it is possible to significantly decrease the cost of construction and operation of synchrotron vacuum system. By using the results of simulations and calculations of electromagnetic field, plasma simulation or glow discharge, titanium sputtering, etc., critical parameters in design of internal structure of ion pump have been optimized. In the following configuration, the pumping has been started at 10-4 torr. The pressure goes down to 10-8, without saturation effect in low pressures

Side-coupled standing wave tubes in AWT IMAGE mode are widely used in the low-energy electron linear accelerator, due to high accelerating gradient and low sensitivity to construction tolerances. The use of various simulation software for designing these kinds of tubes is very common nowadays. In this paper, SUPERFISH code and COMSOL are used for designing the accelerating and coupling cavities for a 6 MeV electron linear accelerator. Finite difference method in SUPERFISH code and Finite element method in COMSOL are used to solve the equations. Besides, dimension of accelerating and coupling cavities and also coupling iris dimension are optimized to achieve resonance frequency of 2.9985 MHz and coupling constant of 0.0112. Considering the results of this study and designing of the RF energy injection port subsequently, the construction of 6 MeV electron tube will be provided

The main purpose for designing and constructing electroradio frequency linear accelerators is to reach better beam quality with higher power and energy by lower RF power consumption. The main step for this purpose is doing research and development in the area of designing, constructing, measuring and tuning of accelerator RF cavities. Institute for Research in Fundamental Sciences (IPM) linear accelerator projecta is the first Iranian project for construction of electrolinear accelerator. In this paper, a brief introduction to construction procedure has been given. Then, the measurement and tuning of a disk-loaded periodic structure before and after tuning was reported. In addition, the detailed design and measurement setup for electric field measurement by perturbation method was investigated

The purpose of electron linear accelerator project in Institute for Research in Fundamental Sciences (IPM) has been to design and construct a S-band electron linear accelerator in such a way that all its parts be designed and built in Iran as much as possible. For more detailed evaluations and assurance, a cooper accelerating tube with the exact same specification of the main accelerating tube has also been constructed. After designing and constructing prototype tube, it was measured by applying slater perturbation method in resonance mode and steel method in non-resonance mode. Adaption of electric field in different modes for the accelerating tube after tuning with simulation values shows the accuracy of the applied construction and mesurment methods

In this paper, we introduce RF electron gun of Iranian Light Source Facility (ILSF) pre-injection system. Design, fabrication and low-power microwave tests results of the prototype RF electron gun have been described in detail. This paper also explains the tuning procedure of the prototype RF electron gun to the desired resonant frequency. The outcomes of this project brighten the path to the fabrication of the RF electron gun by the local industries

In this paper, the feasibility studty of a new method of RF power coupling to acceleration cavity of charged particles accelerator will be evaluated. In this method a slit is created around the accelerator cavity, and RF power amplifier modules is connected directly to the acceleration cavity. In fact, in this design, the cavity in addition to acting as an acceleration cavity, acts as a RF power combiner. The benefits of this method are avoiding the use of RF vacuum tubes, transmission lines, high power combiner and coupler. In this research, cylindrical and coaxial cavities were studied, and a small sample coaxial cavity is build by this method. The results of the resarch showed that compact, economical and safe RF accelerators can be achieved by the proposed method

Resonant structure is one of the proposed methods in combining power in RF systems of RF accelerators. In this structure, fabrication of RF power divider or combiner using coaxial and cylindrical cavity is important. In this study, two combiners, in the same frequency band, are designed and fabricated; and their results are compared. The experimental results confirmed the simulation results and showed that compared with cyclical cavity, the power combiner with coaxial cavity is smaller, more easily adjustable, and is more suitable for use in RF systems of RF accelerators

Considering the challenges in fabrication and electromagnetic characterization of linear accelerator tube, first four major effective parameters in cavity fabrication, including cavity material, dimension agreement, surface roughness and concentricity of cavities have been studied. Then, considering appropriate electromagnetic properties, fabrication results of cavities, techniques for their resonant frequency and quality factor measurement are presented. Then, plunger test is done by designing special fixtures for double checking the resonant frequency of each cavity. Finally, the bead-pull test is accomplished after brazing the cavities together, to check the RF field profile and tuning.

In this paper, the vacuum film deposition through electron beam evaporation has been reviewed and the effect of magnetic field on the operation of this system has been explained. Then, the magnetic field distribution due to magnetic components configuartion of a commercial evaporation source with 270-degree electron beam gun (manufactured by Sharif University Branch of ACECR), has been simulated by means of a finite element software, ANSYS. The simulation result was verified by comparing with the results obtained from measurement by Hall Effect sensor. Furthermore, by using the ray-tracing capability of the software, the capability of the magnetic lens of this device for electron beam focusing has been investigated. The predicted position of the electron beam spot on the target is in good agreement with experimental observations

Linac4 is the near future 160 MeV H- linear accelerator of the CERN presently under construction. It will replace the present Linac2 as injector of the proton accelerator complex in CERN. The Linac4 is composed of a 45 keV ion source, a Low Energy Beam Transport (LEBT), a 352.2 MHz Radio Frequency Quadrupole (RFQ), which accelerates the beam to 3 MeV, and a Medium Energy Beam Transport (MEBT), housing a beam chopper, has been installed and commissioned in the Linac4 tunnel. The LEBT is composed of two solenoids and a diagnostic box; the MEBT is composed of three Radio Frequency (RF) cavities and 11 quadrupole magnets to match and transfer the beam from the source to the RFQ and DTL, respectively. In this paper, the beam matching process of the 45 keV H- beam to the RFQ and that of accelerated 3 MeV beam to the DTL has been presented. The MEBT beam commissioning was complemented with the emittance measurement of the DTL matched beam taken with a slit-and-grid emittance measurement device located after the MEBT line

Cherenkov radiation is generated when relativistic charged particles move in a medium with refractive index larger than unity. Although, the refractive index is generally smaller than unity in X-ray region, in the vicinity of atomic absorption edges, the refractive index may exceed unity and Cherenkov radiation can be generated in soft X-ray region with a narrow band width. In this paper, the spectral-angular distribution of X-ray Cherenkov Radiation (XCR) and its properties are analyzed. It is shown that, by using electron accelerators which can produce 10 MeV electrons, with average current density 20 mA/mm2, and choosing different µm-thick foils, one can produce soft X-ray Cherenkov radiation source with intensity about 10-4 ph/el, and X-ray photon energy from 50 eV up to 1 keV. Some unique properties of XCR, such as narrow band width and high brightness, make XCR a novel soft X-ray source for applications in soft X-ray microscopy, photoelectron spectroscopy, analysis of trace elements and other research areas.

The measurements of electron Channeling Radiation (CR) have been performed at ELBE linear electron accelerator of the Forschungszentrum Dresden-Rossendorf. The aim of performing these experiments was to optimize radiation yield and spectral line width of CR in order to apply channeling radiation for preparing a monochromatic X-ray source. Diamond crystals can be used in relatively high electron currents due to their high Debye temperature and the large thermal conductivity. Measurements of (110) planar channeling radiation have been performed at electron energies of 14.6, 17, 30, and 34 MeV, using diamond crystals of 42.5, 102, 168, and 500 μm thick. These data resulted in installing an X-ray source in ELBE linear electron accelerator. The electron beam with an average current of up to 200 μA allows reaching photon rates between 1010 s-1 and 1011 s-1 per 10% bandwidth. Photon energy can be tuned by changing the electron beam energy. Monochromisation of CR and bremsstrahlung background reduction has been investigated applying X-ray diffraction at a graphite crystal

In this paper, electron acceleration in the field of laser pulse is investigated. To limit the interaction region for electron pulse, which is required for acceleration, a new method is presented based on the injection of electron on temporal peak of the laser pulse. In this method, the electron is provided by a plasma source and is steered inside the laser field by utilizing the magnetic field and the interaction time is optimized for maximum energy gain. The dependence of the electron energy gain on duration and initial phase of the laser pulse as well as the injection angle of the electron is studied and optimized

In this paper a one dimentional position-sensitive X-ray gas detector has been designed, simulated and constructed based on Multi Wire Proportional Chamber (MWPC) with delay line position readout. These kinds of detectors are useful in soft X-ray imaging and are capable of being extended to two dimensions position readout easily. The position resolution of this detector is estimated to be 230µm

Electron curtain accelerator is a type of low-energy electron accelerator, which plays an important role in many different industries such as printing, coating and packing to promote product quality, while reducing volatile organic compounds for protecting global environment. Electron emitter is one of the main components of this type of accelerators. Multi-filament cathodes and grid structures within filament housing have been designed carefully to generate uniform broad beam distribution. Compared to single filament cathode, multi-filament cathodes are more preferred in width expansion and beam uniformity. Distortion of linear filament due to thermal expansion is one of the major problems in this type of electron source. The aim of this study is to design and fabricate an appropriate mechanical system to maintain the filament in its initial shape and position when heating. In addition, dependence of emitted electrons on anode voltage (at constant cathode temperature), as well as dependence of emitted electrons on filament current (at constant anode voltage) have been experimentally investigated.

Intraoperative electron radiotherapy is one of the radiotherapy methods that delivers a high single fraction of radiation dose to the patient in one session during the surgery. Beam shaper applicator is one of the applicators that is recently employed with this radiotherapy method. This applicator has a considerable application in treatment of large tumors. In this study, the dosimetric characteristics of the electron beam produced by LIAC intraoperative radiotherapy accelerator in conjunction with this applicator have been evaluated through Monte Carlo simulation by MCNP code. The results showed that the electron beam produced by the beam shaper applicator would have the desirable dosimetric characteristics, so that the mentioned applicator can be considered for clinical purposes. Furthermore, the good agreement between the results of simulation and practical dosimetry, confirms the applicability of Monte Carlo method in determining the dosimetric parameters of electron beam intraoperative radiotherapy

Electron beam accelerators technology has made significant progress in environmental applications in recent years. Including some environmental applications of industrial accelerators, is clearing the air from oxides of nitrogen and sulfur(NOx , SOx) produced by industrial facilities. Combustion of coal, oil, natural gas and other gases that are produced in power plant, refineries and industrial factories, produce high extent of these oxides wshich exceed the limit in most cases. Clearing by irradiation involves adding amounts of ammonia to output gases and irradiation by Electron beam accelerators. Irradiation produces radicals that interact again with NOx , SOx and produced the related gases. Due to the ammonia, these acids transform into ammonium sulfate ((NH4)2SO4 ) and ammonium nitrate (NH4NO3) are precipitated by electrostatic precipitators, and are used as chemical fertilizer. Cosidering purification process of pollutant gases by electron beam and the importance of electron accelerator in industrial plants that are polluting the environment in Iran, can be a suitable sollution for this environmental problem

In this paper, a practical simulation method for optimizing of x-ray reflection of nano-multilayer mirrors in three different edge energies: Cr-Kα, Co-Kα, and Ti-Kα is discussed in order to obtain the most reflection based on quarter-wave thickness method (QW). In this method, the reflected x-ray will have a constructive interference, and a peak, called Brag peak, will appear in reflection curve when the tickness of the layer is an odd multiple of the quarter-wave thickness. The quarter-wave thickness is dependent to on the angle and energy of the entrance photon beam. In the mentioned edge energies, for different nano-multilayer mirrors, and for incident angle ranges from 0.5 to 8 degrees, the QW thikness for each layer is estimated and the Brag peak reflected intensity was simulated for each angle by the IMD computational code. The details shows that the optimal reflection is accessible by plotting Brag peak reflection curves based on the related angles.