Yerevan Physics Institute Research Articles

О некоторых проектах модернизации ереванского синхротрона арус

В работе представлено краткое описание проектов модернизации и модификации Ереванского электронного синхротрона АРУС Национальной научной лаборатории им. А.И. Алиханяна (Ереванский физический институт). Описанные работы, предложенные в разные годы, представляют интерес в связи с обсуждением вопроса создания новой ускорительной базы в Армении для решения актуальных прикладных и фундаментальных физических задач. Ներկայացված է Ա. Ալիխանյանի անվան Ազգային գիտական լաբորատորիայի (Երևանի ֆիզիկայի ինստիտուտ) ԱՐՈՒՍ էլեկտրոնաիյն սինքրոտրոնի արդիականացման և մոդիֆիկացիայի նախագծերի համառոտ նկարագրությունը: Տարբեր տարիներին մշակված և առաջարկված աշխատանքները հետաքրքրություն են ներկայացնում Հայաստանում նոր արագացուցչային բազայի ստեղծման հարցի քննարկման կապակցությամբ՝ ակտուալ կիրառական և ֆիզիկայի հիմնարար խնդիրների ուսումնասիրման համար: The paper presents a brief description of the projects for the modernization and modification of the Yerevan Electron Synchrotron ARUS of the A. Alikhanyan National Science Laboratory (Yerevan Physics Institute). The described works, proposed in different years, are of interest in connection with the discussion of the issue of creating a new accelerator base in Armenia for solving actual applied and fundamental physical problems.

Investigation of photonuclear reactions on isotopes 51V, natCu, natMo, 115In and 207Pb at photon energy Eγmax= 20–70 MeV

The targets with masses in range of 51–207 a.u. have been exposed to the bremsstrahlung photon beam of the electron linear accelerator of AANL (Yerevan Physics Institute). Yields of (γ, α), (γ, αxn) and (γ, xpyn) reactions have been measured at the maximum bremsstrahlung photon energy of 20, 30, 40 and 70 MeV. The yields and the flux-weighted average cross sections of a number of the reactions were compared with the results of calculation in the frames of the TALYS-1.9 model. Agreement between the calculated and experimental data was obtained within a factor of two.

Atmospheric electric field variations during fair weather and thunderstorms at different altitudes

Ground-based electric field measurements during fair weather and thunderstorms are key parameters for Global Electric Circuit investigations and climate change assessment. We study the variations of near surface electric field during fair weather and thunderstorms. In this work we present daily, monthly and yearly distribution of thunderstorm activity from 2012 to 2019 at different research stations of Cosmic Ray Division (CRD) of the A. Alikhanyan National Science Laboratory (Yerevan Physics Institute) which has been done the first time for mentioned locations. The distribution of fair-weather days based on electric field variation and meteorological parameters are also discussed. According to results, thunderstorm activity is very high from May to June and the most active part during the day is from 15:00 to 20:00 LT at three different altitudes.

A Study of Low-Energy Proton- and Photon-Nuclear Interactions at AANL

In spite of a large amount of the existing experimental data in the region of low-energy proton- and photon-nuclear interactions, new experimental measurements are still needed to gain insight into a number of problems in nuclear physics. Particularly, the stellar nucleo-synthesis, the study of the resonance states of light nuclei, the underlying mechanisms of the (p,n), (p,α) and (γ,p), (γ,n) reactions are of great interest. For this purpose, the possibility of exploitation of existing electron linear accelerator and cyclotron C18/18, which was launch out recently at AANL (Yerevan Physics Institute), are discussed. The upgrade of the existing electron machine and the purchase of a new modern one for the study of the aforementioned nuclear physics problems are presented as well.

A Study of Alpha Particle Production in Photonuclear Reactions at Photon Energies of 21 and 40 MeV

The production of alpha particles in photonuclear reactions on 65Cu, 115In, 92Mo and 207Pb targets in the beam of accelerated electrons with energy of 21 and 40 MeV was studied. The experiments were run on the Linear Electron Accelerator NLA (The Yerevan Physics Institute). The measurement results represent the yields of reactions studied as functions of the mass number of nuclei and the photon energy. The data obtained enable one to suggest a change in the mechanism of alpha particle photoproduction with increasing energy of incident photons and target mass.

INVESTIGATION OF PULSE SHAPE NEUTRON-GAMMA DISCRIMINATION

The role of neutron beam investigation is significant not only for fundamental science but also for various fields of applied science. This work is dedicated to the formation of neutron beams using the external 18-MeV proton beam of IBA cyclotron C18/18 with a beam current of up to 100 µA. The facility is located at the A. Alikhanyan National Science Laboratory (Yerevan Physics Institute). The possibility to obtain thermal or epithermal neutron beams using the external proton beam of the cyclotron is studied using Geant4 simulations. In this case, a quasimonoenergetic neutron source 9Be (p, n)9B reaction is chosen. As a result of the simulations, the optimal thickness of the 9Be beryllium isotope target is determined. The induced neutron beam is accompanied by a gamma ray background. To decrease the number of accompanying gamma rays, the lead absorber is considered. As a method of separating neutrons from gamma rays, the pulse shape discrimination (PSD) technique is developed. This study shows the possibility of neutron-gamma PSD and its applicability using the EJ-299-33A plastic scintillator.

INVESTIGATION OF PULSE SHAPE NEUTRON-GAMMA DISCRIMINATION

The role of neutron beam investigation is significant not only for fundamental science but also for various fields of applied science. This work is dedicated to the formation of neutron beams using the external 18-MeV proton beam of IBA cyclotron C18/18 with a beam current of up to 100 µA. The facility is located at the A. Alikhanyan National Science Laboratory (Yerevan Physics Institute). The possibility to obtain thermal or epithermal neutron beams using the external proton beam of the cyclotron is studied using Geant4 simulations. In this case, a quasimonoenergetic neutron source 9Be (p, n)9B reaction is chosen. As a result of the simulations, the optimal thickness of the 9Be beryllium isotope target is determined. The induced neutron beam is accompanied by a gamma ray background. To decrease the number of accompanying gamma rays, the lead absorber is considered. As a method of separating neutrons from gamma rays, the pulse shape discrimination (PSD) technique is developed. This study shows the possibility of neutron-gamma PSD and its applicability using the EJ-299-33A plastic scintillator.

Linear Electron Accelerator LUE-75 of Yerevan Physics Institute at Energies of 10−75 MeV

The results to increase the rated energy of the linear accelerator of electrons LUE-75 from 50 to 75 MeV are presented. The characteristics of the beam are investigated, and the measured energy spectra of the obtained beams are presented in the range of 50–75 MeV at the average intensity up to 10 μA. The modernization of the elements of magnetic optics for the parallel transfer path was performed, and the beam was tracked to the end of the transport channel.

LUE-75 Linear Accelerator Facility at Yerevan Physics Institute

Owing to the growing interest in the low-energy nuclear physics, it becomes relevant to enhance the potential of the experimental facilities at Yerevan Physics Institute (YerPhI). The complex unit based on the linear electron accelerator LUE-75 (ARUS synchrotron injector) for applied and fundamental experiments with electron beams, the intensity and energy of which can vary in a wide range of 10–18–10–5 А and 10–50 MeV, has been created. In recent years, the regimes developed at LUE-75 were applied to obtain the controllable electron beams of extremely low intensity used for calibration of detectors.

Study of Atmospheric Discharges by Near Surface Electric Field Measurements

Background:In this work the disturbances of the near surface electric field are investigated, which are attributed to different types of atmospheric discharges: intracloud or cloud-to-ground.Method:The patterns of the lightning occurrences are discussed as measured by the network of the electric field mills located at the stations of Cosmic Ray Division of Yerevan Physics Institute. Discharges make changes in the near surface electric field, which can be separated into two groups. The differences of those two groups and shapes of the recovery curves are discussed using the data from electric field mills network for a stormy day on May 23, 2015.Conclusion:The results presented in this work show that magnitudes of field changes from one of the groups are larger and have shorter duration compared to another one. Recovery curves of the near surface electric field produced by lightning flashes also have a power-law or a linear dependence besides exponential shape.

25th Annual International Laser Physics Workshop (LPHYS’16)

EDITORIALDear Readers,The 25th annual International Laser Physics Workshop, LPHYS’16, took place in the city of Yerevan, Republic of Armenia. 319 participants from 32 countries attended the conference. It was hosted by the Yerevan Physics Institute, A Alikhanyan National Laboratory. This year the conference has been endorsed by the Optical Society (OSA), the year the society celebrates its 100th anniversary.The LPHYS’16 Steering Committee and the Advisory & Program Committee would like to extend their sincere gratitude to Dr. Koryun B Oganesyan (Chair of the Local Organizing Committee) and to his team for the outstanding job performed on organizing, arranging, managing and putting in order the conference. Their combined effort lead to a successful result.In this volume of the IOP Journal of Physics: Conference Series you will find selected proceedings of the Workshop in Yerevan.Please make a note that the 26th annual International Laser Physics Workshop (LPHYS’17) will take place from July 17 to July 21, 2017 in the city of Kazan, Russia hosted by the Kazan E K Zavoisky Physical-Technical Institute (KPhTI).With kind regards,Steering and Advisory & Program committeesLPHYS’16

Investigation of 123I production using electron accelerator

The possibility of 123I isotope production with the help of the high-intensity bremsstrahlung photons produced by the electron beam of the LUE50 linear electron accelerator at the A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute [YerPhI]) is considered. The production method has been established and shown to be successful. The 124Xe(γ,n)123Xe→123I nuclear reaction has been investigated and the cross-section was calculated by nuclear codes TALYS 1.6 and EMPIRE 3.2. The optimum parameter of the thickness of the target was determined by GEANT4 code. For the normalized yield of 123I, the value of 143Bq/(mg·μA·h) has been achieved.

24th International Laser Physics Workshop (LPHYS'15)

Dear Readers,The 24th annual International Laser Physics Workshop, LPHYS'15, took place in the City of Shanghai, China. 357 participants from 29 countries attended the conference. It was hosted by the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences.The LPHYS’15 Steering Committee and the Advisory & Program Committee would like to extend their sincere gratitude to Professor Ruxin Li (Co-Chair), Professor Heping Zeng, Professor Zhenrong Sun (Co-Chairs of the Local Organizing Committee) and to their team for the outstanding job performed in organizing, arranging, managing and putting in order the conference. Their combined efforts lead to a successful result.In this volume of the IOP Journal of Physics: Conference Series you will find selected proceedings of the Workshop in Shanghai.Please make a note that the 25rd annual International Laser Physics Workshop (LPHYS'16) will take place from July 11 to July 15, 2016 in the city of Yerevan, Republic of Armenia hosted by Yerevan Physics Institute, AAlikhanyan National Laboratory.With kind regards,Steering and Advisory & Program committees LPHYS'15

Conceptual design project: Accelerator complex for nuclear physics studies and boron neutron capture therapy application at the Yerevan Physics Institute (YerPhI) Yerevan, Armenia

The final goal of the proposed project is the creation of a Complex of Accelerator Facilities at the Yerevan Physics Institute (CAF YerPhI) for nuclear physics basic researches, as well as for applied programs including boron neutron capture therapy (BNCT). The CAF will include the following facilities: Cyclotron C70, heavy material (uranium) target/ion source, mass-separator, LINAC1 (0.15–1.5MeV/u) and LINAC2 (1.5–10MeV/u). The delivered by C70 proton beams with energy 70MeV will be used for investigations in the field of basic nuclear physics and with energy 30MeV for use in applications.

Development of medicine-intended isotope production technologies at Yerevan Physics Institute

Accelerator-based 99m Tc and 123 I isotopes production technologies were created and developed at A.Alikhanyan National Science Laboratory (former Yerevan Physics Institute - YerPhI). The method involves the irradiation of natural molybdenum (for 99m Tc production) and natural xenon (for 123 I production) using high-intensity bremsstrahlung photons from the electron beam of the LUE50 linear electron accelerator located at the YerPhI. We have developed and tested the extraction of 99m Tc and 123 I from the irradiated natural MoO3 and natural Xe, respectively. The production method has been developed and shown to be successful. The current activity is devoted to creation and development of the technology of direct production 99m Tc on the 100 Mo as target materials using the proton beam from an IBA C18/18 cyclotron. The proton cyclotron C18/18 (producer – IBA, Belgium) was purchased and will be installed nearby AANL (YerPhI) till end 2014. The 18 MeV protons will be used to investigate accelerator-based schemes for the direct production of 99mTc. Main topics of studies will include experimental measurement of 99m Tc production yield for different energies of protons, irradiation times, intensities, development of new methods of 99m Tc extraction from irradiated materials, development of target preparation technology, development of target material recovery methods for multiple use and others.

Photonuclear reactions on 112,118,124Sn, natTe, and natHf targets

The yields of products of photonuclear reactions on tin targets enriched in the isotopes 112,118,124Sn and on Te and HfO2 targets of natural isotopic composition were measured. The targets were irradiated at the linear electron accelerator of the A.I. Alikhanian National Science Laboratory (Yerevan Physics Institute) at the electron energy of Ee = 40 MeV. The dependence of the product yields on the nucleonic composition of the targets was discussed. The isomeric ratios were obtained for the 119m,gTe, 121m,gTe, 117m,gIn, and 123m,gSn products. The experimental data in question were compared with their theoretical counterparts calculated on the basis of the TALYS 1.4 code. The dependence of the isomeric ratios on the photon energy and on the mass number of the product is considered.

Critical phenomena for systems under constraint

Critical phenomena for systems under constraint N. Izmailian1,2, R. Kenna2 1 Yerevan Physics Institute, Alikhanian Brothers 2, 375036 Yerevan, Armenia 2 Applied Mathematics Research Center, Coventry University, Coventry CV1 5FB, England Received June 5, 2014 It is well known that the imposition of a constraint can transform the properties of critical systems. Early work on this phemomenon by Essam and Garelick, Fisher, and others, focused on the effects of constraints on the leading critical exponents describing phase transitions. Recent work extended these considerations to critical amplitudes and to exponents governing logarithmic corrections in certain marginal scenarios. Here these old and new results are gathered and summarised. The involutory nature of transformations between the critical parameters describing ideal and constrained systems are also discussed, paying particular attention to matters relating to universality.

Photo-production of (99)Mo/(99m)Tc with electron linear accelerator beam.

We report on the development of a relatively new method for the production of (99)Mo/(99m)Tc. The method involves the irradiation of natural molybdenum using high-intensity bremsstrahlung photons from the electron beam of the LUE50 linear electron accelerator located at the Yerevan Physics Institute (YerPhi). The production method has been developed and shown to be successful. The linear electron accelerator at YerPhi was upgraded to allow for significant increases of the beam intensity and spatial density. The LUE50 was also instrumented by a remote control system for ease of operation. We have developed and tested the (99m)Tc extraction from the irradiation of natural MoO3. This paper reports on the optimal conditions of our method of (99)Mo production. We show the success of this method with the production and separation of the first usable amounts of (99m)Tc.

Problems of magnetic field distortions caused by eddy currents in Yerevan synchrotron

The effects of eddy currents on the design value of magnetic field in accelerators are investigated analytically. A program is developed for calculation of magnetic field distortions caused by eddy currents. The numerical results are given for the accelerator in Yerevan Physics Institute, if it will be used to accelerate the ions.

Experimental plant for investigation of the possibility of linac-based production of medicine-intended isotopes

We describe a technique of obtaining radioactive 99mTc isotope by irradiation of molybdenum with high-intensity beam of bremsstrahlung photons from the electron beam of the linear electron accelerator (LUE50) of the Alikhanyan National Science Laboratory (ANSL, former Yerevan Physics Institute). We have elaborated and created an experimental plant for development of 99mTc production technology. Upgrading of linac has been performed aimed at raising the beam intensity and density. A system of automated control of the parameters of the plant and accelerator was built up. We carried out preliminary studies of 99mTc obtaining technique and give quantitative and qualitative results.