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Goryashko, Vitaliy
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Publications (10 of 35) Show all publications
Goryashko, V., Jobs, M., Hoang, L., Eriksson, J. & Ruber, R. (2018). 12-Way 100 kW Reentrant Cavity-Based Power Combiner With Doorknob Couplers. IEEE Microwave and Wireless Components Letters, 28(2), 111-113
Open this publication in new window or tab >>12-Way 100 kW Reentrant Cavity-Based Power Combiner With Doorknob Couplers
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2018 (English)In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 28, no 2, p. 111-113Article in journal (Refereed) Published
Abstract [en]

We present radio frequency (RF) and thermal characterization of a compact 12-way power combiner designed for operation at 352 MHz at a power level of 100 kW with 5% duty factor. The combiner is based on a reentrant cavity with 12 input doorknob couplers and one output coupler that is integrated with the post of the cavity and forms doorknob type geometry. We introduce convenient design formulas that allow easy identification of a suitable parameter space, which is then refined with numerical simulations. Low-power RF measurements of a prototype show 0.2% insertion loss and a relative rms amplitude imbalance between the ports of 0.1% and phase imbalance of 0.036 degrees rms. The matching is better than -25 dB over a 3-dB bandwidth around the design frequency. We also tested the combiner up to 200 kW and found the RF loss to be comparable to that of the low-power measurement. In a long test run at 100 kW with 5% duty factor, the combiner temperature stabilized at 10 degrees above ambient.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2018
Keywords
High-power handling capability, high-power radio frequency (RF) measurements, power combiner, thermal study
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-349845 (URN)10.1109/LMWC.2017.2780619 (DOI)000425173500007 ()
Available from: 2018-05-03 Created: 2018-05-03 Last updated: 2018-05-03Bibliographically approved
Shamuilov, G., Mak, A., Salén, P. & Goryashko, V. (2018). Analytical model of waveform-controlled single-cycle light pulses from an undulator. Optics Letters, 43(4), 819-822
Open this publication in new window or tab >>Analytical model of waveform-controlled single-cycle light pulses from an undulator
2018 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 43, no 4, p. 819-822Article in journal (Refereed) Published
Abstract [en]

This Letter builds upon a recent concept [Phys. Rev. Lett. 113, 104801 (2014)] for producing ultrashort optical pulses through the coherent radiation of electrons in an undulator. Each pulse contains only a single oscillation cycle, and has a controlled waveform (and hence a stable carrier-envelope phase). While the concept had been demonstrated numerically, this Letter provides an analytical model for the radiation mechanism, thereby revealing three key observations: (i) the correlation between the waveforms of the optical and undulator fields; (ii) the free-space dispersion of transversely confined light; and (iii) the dependence of the optical pulse shape on the undulator field strength.

Place, publisher, year, edition, pages
OPTICAL SOC AMER, 2018
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-349360 (URN)10.1364/OL.43.000819 (DOI)000425123700049 ()29444002 (PubMedID)
Funder
Swedish Research Council, 2016-04593
Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2018-04-26Bibliographically approved
Hoang Duc, L., Bhattacharyya, A., Goryashko, V., Ruber, R., Olsson, J. & Dancila, D. (2018). Time Domain Characterization of High Power Solid State Amplifiers for the Next Generation Linear Accelerators. Microwave and optical technology letters (Print), 60(1), 163-171
Open this publication in new window or tab >>Time Domain Characterization of High Power Solid State Amplifiers for the Next Generation Linear Accelerators
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2018 (English)In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 60, no 1, p. 163-171Article in journal (Refereed) Published
Abstract [en]

This paper presents the time domain characterization of high power pulsed solid state amplifiers to be used forlinear accelerator applications. The study comprises nonlinear circuit envelope simulations and time domainenvelope measurements. Measurements and simulations are performed under the pulsed conditions (3.5 mspulse width, 5% duty cycle) specific to the European Spallation Source (ESS) high intensity proton accelerator.We measure the characteristics of pulsed LDMOS based power amplifiers such as: pulse droop along the pulse,efficiency, average envelope pulse amplitude and phase, pulse drain current waveform, pulse drain voltagewaveform, etc. A comparison between the measured results and the simulated results is also presented. Inaddition to the pulse profile characterization, the pulse to pulse (P2P) stability of the presented solid state poweramplifier (SSPA) is investigated as variations of amplitude and phase. The P2P stability simulations areintroduced as a combination of the Monte-Carlo simulations and the nonlinear circuit envelope simulations. Thesimulated results are used for fitting the P2P measurements to give an early insight of causes of instabilities ofthe nonlinear LDMOS models.

Keywords
accelerator, solid state amplifiers, LDMOS, nonlinear circuit envelope, time domain envelope measurements, pulse profile
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-334910 (URN)10.1002/mop.30926 (DOI)000416937700028 ()
Projects
ESS
Available from: 2017-11-29 Created: 2017-11-29 Last updated: 2018-02-28Bibliographically approved
Mak, A., Salén, P. & Goryashko, V. (2018). Undulator Considerations in the Baseline Design of the MAX IV Soft X-Ray Laser.
Open this publication in new window or tab >>Undulator Considerations in the Baseline Design of the MAX IV Soft X-Ray Laser
2018 (English)Report (Other academic)
Abstract [en]

We examine the optimal parameter space for an x-ray free-electron laser (FEL) in the operation mode of self-amplified spontaneous emission (SASE). The study focuses on FEL operation with a shorter undulator period and higher undulator strength made available through recent developments in in-vacuum, cryogenic and superconducting undulators. We survey the progress on short-period undulator technologies and compute the FEL output characteristics versus the undulator parameters. We perform the study on a case of the planned soft-x-ray FEL at the MAX IV Laboratory in Sweden. An extension of the SASE mode into the harmonic lasing self-seeded mode is also analysed.

Publisher
p. 16
Series
FREIA Report ; 2018-4
National Category
Accelerator Physics and Instrumentation
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-357900 (URN)
Funder
Swedish Research Council, 2016-04593The Royal Swedish Academy of Sciences, PH2018- 0037EU, Horizon 2020, 777431
Available from: 2018-08-21 Created: 2018-08-21 Last updated: 2018-08-22Bibliographically approved
Santiago Kern, R., Bhattacharyya, A., Gajewski, K., Goryashko, V., Hermansson, L., Jobs, M., . . . Ruber, R. (2017). Cryogenic Synopsis from the Testing of the Fully Equipped ESS’ Double Spoke Cavity Romea. Uppsala
Open this publication in new window or tab >>Cryogenic Synopsis from the Testing of the Fully Equipped ESS’ Double Spoke Cavity Romea
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2017 (English)Report (Other academic)
Place, publisher, year, edition, pages
Uppsala: , 2017. p. 29
Series
FREIA Report ; 2017/12
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-333037 (URN)
Available from: 2017-11-06 Created: 2017-11-06 Last updated: 2017-11-09Bibliographically approved
Opanasenko, A., Mytrochenko, V., Zhaunerchyk, V. & Goryashko, V. (2017). Design study of a low-emittance high-repetition rate thermionic rf gun. PHYSICAL REVIEW ACCELERATORS AND BEAMS, 20(5), Article ID 053401.
Open this publication in new window or tab >>Design study of a low-emittance high-repetition rate thermionic rf gun
2017 (English)In: PHYSICAL REVIEW ACCELERATORS AND BEAMS, ISSN 2469-9888, Vol. 20, no 5, article id 053401Article in journal (Refereed) Published
Abstract [en]

We propose a novel gridless continuous-wave radiofrequency (rf) thermionic gun capable of generating nC ns electron bunches with a rms normalized slice emittance close to the thermal level of 0.3 mm mrad. In order to gate the electron emission, an externally heated thermionic cathode is installed into a stripline-loop conductor. Two high-voltage pulses propagating towards each other in the stripline-loop overlap in the cathode region and create a quasielectrostatic field gating the electron emission. The repetition rate of pulses is variable and can reach up to one MHz with modern solid-state pulsers. The stripline attached to a rf gun cavity wall has with the wall a common aperture that allows the electrons to be injected into the rf cavity for further acceleration. Thanks to this innovative gridless design, simulations suggest that the bunch emittance is approximately at the thermal level after the bunch injection into the cavity provided that the geometry of the cathode and aperture are properly designed. Specifically, a concave cathode is adopted to imprint an.-shaped distribution onto the beam transverse phase-space to compensate for an S-shaped beam distribution created by the spherical aberration of the aperture-cavity region. In order to compensate for the energy spread caused by rf fields of the rf gun cavity, a 3rd harmonic cavity is used. A detailed study of the electrodynamics of the stripline and rf gun cavity as well as the beam optics and bunch dynamics are presented.

National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-360219 (URN)10.1103/PhysRevAccelBeams.20.053401 (DOI)000440464600002 ()
Funder
Swedish Research Council
Available from: 2018-09-13 Created: 2018-09-13 Last updated: 2018-09-13Bibliographically approved
Li, H., Santiago-Kern, R., Jobs, M., Bhattacharyya, A., Goryashko, V., Hermansson, L., . . . Ruber, R. (2017). First High Power Test of the ESS Double Spoke Cavity. Uppsala
Open this publication in new window or tab >>First High Power Test of the ESS Double Spoke Cavity
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2017 (English)Report (Other academic)
Abstract [en]

The first double spoke cavity for ESS project was tested with high power in the HNOSS cryostat at FREIA Laboratory. This cavity is designed for 325.21MHz, a pulse mode with 14 Hz repetition rate, up to peak power of 360 kW. The qualification of the cavity package in a high power test, involved a spoke superconducting cavity, a fundamental power coupler, LLRF system and a RF station, represented an important verification before the module assembly. This report presents the test configuration, RF conditioning history and first high power performance of this cavity package.

Place, publisher, year, edition, pages
Uppsala: , 2017. p. 60
Series
FREIA Report ; 2017/10
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-335434 (URN)
Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2017-12-06Bibliographically approved
Goryashko, V. A. (2017). Quasi-half-cycle pulses of light from a tapered undulator. PHYSICAL REVIEW ACCELERATORS AND BEAMS, 20(8), Article ID 080703.
Open this publication in new window or tab >>Quasi-half-cycle pulses of light from a tapered undulator
2017 (English)In: PHYSICAL REVIEW ACCELERATORS AND BEAMS, ISSN 2469-9888, Vol. 20, no 8, article id 080703Article in journal (Refereed) Published
Abstract [en]

Strong-field few-cycle terahertz (THz) pulses are an invaluable tool for engineering highly non-equilibrium states of matter. A scheme is proposed to generate quasi-half-cycle GV/m-scale THz pulses with a multikilohertz repetition rate. It makes use of coherent spontaneous emission from a prebunched electron beam traversing an optimally tapered undulator. The scheme is the further development of the slippage control in free-electron lasers [T. Tanaka, Phys. Rev. Lett. 114, 044801 (2015)]. An explicit condition for the spectral amplitude of undulator radiation and a phase condition for the electron density distribution, required for the generation of desired pulses, are presented. The amplitude condition is met by proper undulator tapering, and a generic optimal undulator profile is found analytically. In order to meet the phase condition, the distance between the adjacent bunches is varied according to the instantaneous resonant undulator wavelength. A 3D analytical theory is complemented by a detailed numerical study based on a direct solution to the 3D wave equation.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-332656 (URN)10.1103/PhysRevAccelBeams.20.080703 (DOI)000407559200001 ()
Funder
Swedish Research Council
Available from: 2017-11-13 Created: 2017-11-13 Last updated: 2017-11-13Bibliographically approved
Goryashko, V. A., Bhattacharyya, A. K., Li, H., Dancila, D. & Ruber, R. (2016). A Method for High-Precision Characterization of the Q-Slope of Superconducting RF Cavities. IEEE transactions on microwave theory and techniques, 64(11), 3764-3771
Open this publication in new window or tab >>A Method for High-Precision Characterization of the Q-Slope of Superconducting RF Cavities
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2016 (English)In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 64, no 11, p. 3764-3771Article in journal (Refereed) Published
Abstract [en]

We propose a novel method for high-precision determination of a quality factor Q(0) of a superconducting radio-frequency cavity as a function of the strength of the field excited in the cavity, the so-called Q-slope. Usually, the cavity parameters are measured only at resonance for different cavity field strengths, but such a single data point measurement for a given field strength results in a 10%-15% uncertainty in Q(0). In contrast, we propose a method that improves the accuracy of Q(0) determination by an order of magnitude. We vary the phase of an excited stabilized field in the cavity and measure the reflection coefficient of the cavity as a function of the phase. The procedure is repeated for different strengths of the excited field. Given the fact that the complex reflection coefficient of a cavity describes a perfect circle in polar coordinates as a function of the field phase for a constant field strength, we find the coupling coefficient much more accurately by fitting the overdetermined set of measured data to the circle for each value of the cavity field. From the time-decay measurement, which allows least-squares minimization, we accurately find the total (loaded) quality factor and deduce Q(0) with an uncertainty of around 1%.

Keywords
Cavity quality factor, minimization procedure, precise microwave measurements, self-excited loop, superconducting (SC) radio-frequency (RF) resonator
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-311203 (URN)10.1109/TMTT.2016.2605671 (DOI)000388501900002 ()
Available from: 2016-12-22 Created: 2016-12-22 Last updated: 2018-02-28Bibliographically approved
Han, L., Vitaliy, G., Sakari, T. & Roger, R. (2016). Calibration procedure for RF test. Uppsala: Uppsala universitet
Open this publication in new window or tab >>Calibration procedure for RF test
2016 (English)Report (Other academic)
Abstract [en]

Precision measurements of quality factors of superconducting resonators are desired in the determination of ESS superconducting cavities. Components of the measurement setup, such as interconnecting cables and adapters, introduce variations in magnitude and phase that can mask the actual response of the device under test. In order to have an accurate measurement, calibration becomes the first and most important step. FREIA has developed a test stand based on a self-exited loop for demonstrating the performance of superconducting cavities at low power level. So far, a single spoke cavity Hélène and a double spoke cavity Germaine from IPNO have undergone a cold test with FREIA SEL. Several calibration procedures are studied in these tests. Similar test results as IPNO's previous test were obtained with the FREIA system, which means the accuracy control fulfills the requirements.

This report presents the calibration procedure of the FREIA SEL test.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2016. p. 9
Series
FREIA Report ; 2016/02
Keywords
calibration, RF
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-278899 (URN)
Available from: 2016-02-26 Created: 2016-02-26 Last updated: 2016-03-10Bibliographically approved
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