Publications by Ivan Konoplev


A tunable source of coherent terahertz radiation driven by the microbunched electron beam

Journal of Physics D: Applied Physics IOP Publishing 53 (2019) 105501

H Zhang, I Konoplev, G Doucas


Resonant Excitation of Volume and Surface Fields on Complex Electrodynamic Surfaces

Physical Review Applied 11 (2019)

AJ MacLachlan, CW Robertson, IV Konoplev, AW Cross, ADR Phelps, K Ronald

© 2019 authors. Published by the American Physical Society. Analytical, numerical, and experimental studies of volume and surface-field coupling in planar metal periodic surface lattice (PSL) structures superimposed on dielectric substrates with a metallic backing (PSLDM) are presented. We show the formation of frequency-locked PSLDM-coupled eigenmodes and unlocked surface-field resonances (PSL without substrate). These experimental observations are in excellent agreement with theoretical and numerical predictions. For the first time, the derivation of a field coupling coefficient α is demonstrated. By comparing theoretical and numerical dispersions, we obtain α. Detailed analysis of possible scattering mechanisms and dispersive behavior in subwavelength "effective metadielectric" PSLs is shown. The theory and measurements presented in this paper are applicable over a broad frequency range from optical frequencies to THz and are fundamental to the innovation of high-power short-wavelength sources, solar cells, and alternative subwavelength absorbers.


A coherent Smith-Purcell radiation source: Design considerations for a high power, tunable source of terahertz radiation

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2019-September (2019)

H Zhang, I Konoplev, G Doucas

© 2019 IEEE. The concept of coherent terahertz (THz) tunable Smith-Purcell radiation source driven by the microbunched electron beam is presented. Studies were performed using numerical and analytical approaches to investigate the radiation generated by electron microbunches. It is demonstrated that the capability of manipulating the microbunching of electron beams results in the possibility to control both the radiation power and the frequency of coherent Smith-Purcell radiation (cSPr). Numerical results were compared with analytical calculations and there is a good agreement between them. These proof of concept studies demonstrate the possibility of designing a high power, broadly tunable THz radiation source.


Optimization of dual axis asymmetric cavity for energy recovery Linac

29th Linear Accelerator Conference JaCoW Publishing (2019)

YV Shashkov, A Bulygin, MA Gusarova, I Konoplev, F Marhauser, A Seryi


Developing Innovative, Robust and Affordable Medical Linear Accelerators for Challenging Environments.

Clinical oncology (Royal College of Radiologists (Great Britain)) (2019)

M Dosanjh, A Aggarwal, D Pistenmaa, E Amankwaa-Frempong, D Angal-Kalinin, S Boogert, D Brown, M Carlone, P Collier, L Court, A Di Meglio, J Van Dyk, S Grover, DA Jaffray, C Jamieson, J Khader, I Konoplev, H Makwani, P McIntosh, B Militsyn, J Palta, S Sheehy, SC Aruah, I Syratchev, E Zubizarreta, CN Coleman


Self-injection of multiple electron microbunches into a beam-driven plasma bubble

45th EPS Conference on Plasma Physics, EPS 2018 2018-July (2019) 893-896

Z Lécz, A Andreev, A Seryi, I Konoplev, J Smith


Studies of high order modes in asymmetric dual-axis cavity

Applied Physics Letters 113 (2018)

M Topp-Mugglestone, IV Konoplev, H Zhang, A Seryi

© 2018 Author(s). Electron-beam current in superconducting radiofrequency energy recovery linear accelerators (SCRF ERLs) is limited by beam break-up (BBU) instabilities disrupting beam transport and energy recuperation. The instabilities originate from the accumulation of high order modes (HOMs) in the cavity and positive feedback between the beam and HOMs which is especially evident in multi-pass ERLs. Overcoming the beam current limitations due to BBU instabilities is one of the challenges in accelerator science. A dual-axis asymmetric SCRF ERL has been proposed as a possible way to drive a high average current electron beam for next-generation light sources and beam cooling in electron-ion colliders (EICs). In this work, detailed studies on HOMs in the asymmetric dual axis cavity were carried out. The asymmetric field distribution of HOMs (i.e., confinement to one or another axis) has been demonstrated and their excitation from different axes has been studied. The results confirm the numerical predictions and theory developed to describe the asymmetric dual axis cavity.


Trains of electron micro-bunches in plasma wake-field acceleration

PLASMA PHYSICS AND CONTROLLED FUSION 60 (2018) ARTN 075012

Z Lecz, A Andreev, I Konoplev, A Seryi, J Smith


Millimeter-Wave Periodic Surface Lattices for Mode Control in Vacuum Electronic Sources

2017 EIGHTEENTH INTERNATIONAL VACUUM ELECTRONICS CONFERENCE (IVEC) (2018)

AJ MacLachlan, AR Phipps, CW Robertson, IV Konoplev, K Ronald, AW Cross, ADR Phelps, IEEE


Selective excitation and control of coherent terahertz Smith-Purcell radiation by high-intensity period-tunable train of electron micro-bunches

Applied Physics Letters American Institute of Physics 113 (2018) Artricle: 171104-

Y Liang, Y Du, D Wang, L Yan, Q Tian, K Chen, W Huang, C Tang, IV Konoplev, G Doucas, H Zhang

We report the observation and studies of selective excitation and control of Terahertz (THz) coherent Smith-Purcell radiation (cSPr) from a train of sub-picosecond-period electron micro-bunches. The coherence of the radiation from such a train has been demonstrated. The spectrum of cSPr was measured and the selective excitation of the first and the second harmonics was observed respectively. We also demonstrate experimentally that radiation pulses generated by each electron micro-bunch interfere coherently with the maximum intensity of cSPr observed at the frequency equal to the frequency of the micro-bunch spacing. The experimental results greatly contribute to the understanding of coherent Smith-Purcell radiation from the train of electron micro-bunches, as well as the development of THz diagnostics for accelerators.


PERIODIC STRUCTURES MANUFACTURED BY 3D PRINTING FOR ELECTRON BEAM EXCITATION OF HIGH POWER MICROWAVE SOURCES

2017 IEEE 21ST INTERNATIONAL CONFERENCE ON PULSED POWER (PPC) (2018)

AR Phipps, AJ MacLachlan, L Zhang, CR Robertson, IV Konoplev, K Ronald, ADR Phelps, AW Cross, IEEE


Concept of a tunable source of coherent THz radiation driven by a plasma modulated electron beam

Physics of Plasmas AIP Publishing 25 (2018) 043111

H Zhang, I Konoplev, G Doucas, J Smith

We have carried out numerical studies which consider the modulation of a picosecond long relativistic electron beam in a plasma channel and the generation of a micro-bunched train. The subsequent propagation of the micro-bunched beam in the vacuum area was also investigated. The same numerical model was then used to simulate the radiation arising from the interaction of the micro-bunched beam with a metallic grating. The dependence of the radiation spectrum on the parameters of the micro-bunched beam has been studied and the tunability of the radiation by the variation of the micro-bunch spacing has been demonstrated. The micro-bunch spacing can be changed easily by altering the plasma density without changing the beam energy or current. Using the results of these studies, we develop a conceptual design of a tunable source of coherent terahertz (THz) radiation driven by a plasma modulated beam. Such a source would be a potential and useful alternative to conventional vacuum THz tubes and THz free-electron laser sources.


OPTIMIZATION OF DUAL AXIS ASYMMETRIC CAVITY FOR ENERGY RECOVERY LINAC

29th Linear Accelerator Conference-LINAC18: 29th Linear Accelerator Conf. (2018)

Y Shashkov, A Bulygin, I Konoplev, MA Gusarova, F Marhauser, A Seryi


Novel approach to the elimination of background radiation in a single-shot longitudinal beam profile monitor

Proceedings of the 5th International Beam Instrumentation Conference, IBIC 2016 (2018) 471-474

H Harrison, G Doucas, AJ Lancaster, IV Konoplev, H Zhang, A Aryshev, M Shevelev, N Terunuma, J Urakawa

Copyright © 2016 CC-BY-3.0 and by the respective authors. It is proposed to use the polarization of coherent Smith-Purcell radiation (cSPr) to distinguish between the cSPr signal and background radiation in a single-shot longitudinal bunch profile monitor. A preliminary measurement of the polarization has been carried out using a 1 mm periodic metallic grating installed at the 8 MeV electron accelerator LUCX, KEK (Japan). The measured degree of polarization at θ = 90° (300 GHz) is 72.6 ± 3.7%. To make a thorough test of the theoretical model, measurements of the degree of polarization must be taken at more emission angles - equivalent to more frequencies.


Observation of coherent Smith-Purcell and transition radiation driven by single bunch and micro-bunched electron beams

Applied Physics Letters American Institute of Physics 112 (2018) Article number: 053501-1

Y Liang, Y Du, X Su, D Wang, L Yan, Q Tian, H Zhang, G Doucas, D Wang, W Huang, W Gai, C Tang, I Konoplev, Z Zhou

<p>Generation of coherent Smith-Purcell (cSPr) and transition/diffraction radiation using a single bunch or a pre-modulated relativistic electron beam is one of the growing research areas aiming at the development of radiation sources and beam diagnostics for accelerators. We report the results of comparative experimental studies of terahertz radiation generation by an electron bunch and micro-bunched electron beams and the spectral properties of the coherent transition and SP radiation. The properties of cSPr spectra are investigated and discussed, and excitations of the fundamental and second harmonics of cSPr and their dependence on the beam-grating separation are shown. The experimental and theoretical results are compared, and good agreement is demonstrated.</p>


A Fabry-Pérot interferometer with wire-grid polarizers as beamsplitters at terahertz frequencies

Review of Scientific Instruments AIP Publishing 89 (2018) 035116

I Konoplev, G Doucas, H Harrison, AJ Lancaster, M Shevelev, N Terunuma, A Aryshev, J Urakawa, PG Huggard

The design of a compact Fabry-Pérot interferometer (FPi) and results of the experimental studies carried out using the device are presented. Our FPi uses freestanding wire-grid polarizers (WGPs) as beamsplitters and is suitable for use at terahertz (THz) frequencies. The FPi was studied at the LUCX facility, KEK, Japan, and an 8 MeV linear electron accelerator was used to generate coherent Smith-Purcell radiation. The FPi was designed to be easy to align and reposition for experiments at linear accelerator facilities. All of the components used were required to have a flat or well understood frequency response in the THz range. The performance of the FPi with WGPs was compared to that of a Michelson interferometer and the FPi is seen to perform well. The effectiveness of the beamsplitters used in the FPi is also investigated. Measurements made with the FPi using WGPs, the preferred beamsplitters, are compared to measurements made with the FPi using silicon wafers as alternative beamsplitters. The FPi performs well with both types of beamsplitter in the frequency range used (0.3–0.5 THz). The successful measurements taken with the FPi demonstrate a compact and adaptable interferometer that is capable of analyzing THz radiation over a broad frequency range. The scheme is particularly well suited for polarization studies of THz radiation produced in an accelerator environment.


Smith-Purcell coherent THz radiation signal modulation measurements for monitoring of separation of femtosecond electron micro-bunches

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz (2017)

IV Konoplev, H Zhang, AJ Lancaster, H Harrison, G Doucas, A Aryshev, M Shevelev, N Terunuma, J Urakawa

© 2017 IEEE. Micro-bunched particle beams are used for a wide range of research including tunable sources of THz radiation. In most of the applications accurate and non-destructive monitoring of the bunch-to-bunch separation is required. We present the results of proof-of-principle experiments on measuring the distance between two micro-bunches via the analysis of the coherent Smith-Purcell signal amplitude modulation. The proposed monitor can be used to provide feedback to control the sum-millimeter distances between the femtosecond long micro-bunches to stabilize the operation of a THz oscillator or to position the witness bunch into the right phase of the wakefield.


Experimental studies of 7-cell dual axis asymmetric cavity for energy recovery linac

Physical Review Accelerators and Beams American Physical Society 20 (2017) 103501

I Konoplev, K Metodiev, AJ Lancaster, R Ainsworth, G Burt, A Seryi

High average current, transportable energy recovery linacs (ERLs) can be very attractive tools for a number of applications including next generation high-luminosity, compact light sources. Conventional ERLs are based on an electron beam circulating through the same set of rf cavity cells. This leads to an accumulation of high-order modes inside the cavity cells, resulting in the development of a beam breakup (BBU) instability, unless the beam current is kept below the BBU start current. This limits the maximum current which can be transported through the ERL and hence the intensity of the photon beam generated. It has recently been proposed that splitting the accelerating and decelerating stages, tuning them separately and coupling them via a resonance coupler can increase the BBU start current. The paper presents the first experimental rf studies of a dual axis 7-cell asymmetric cavity and confirms the properties predicted by the theoretical model. The field structures of the symmetric and asymmetric modes are measured and good agreement with the numerical predictions is demonstrated. The operating mode field flatness was also measured and discussed. A novel approach based on the coupled mode (Fano-like) model has been developed for the description of the cavity eigenmode spectrum and good agreement between analytical theory, numerical predictions and experimental data is shown. Numerical and experimental results observed are analyzed, discussed and a good agreement between theory and experiment is demonstrated.


Smith-Purcell coherent THz radiation signal modulation measurements for monitoring of separation of femtosecond electron micro-bunches

2017 42nd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) (2017)

IVAN Konoplev


Periodic structures manufactured by 3D printing for electron beam excitation of high power microwave sources

2017 IEEE 21st International Conference on Pulsed Power (PPC) (2017)

IVAN Konoplev

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