Yaman, Fatih
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Yaman, F
Yaman, F.
Yaman, F.
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Email Address
fatihyaman@iyte.edu.tr
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03.05. Department of Electrical and Electronics Engineering
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Current Staff
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4QUALITY EDUCATION
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9INDUSTRY, INNOVATION AND INFRASTRUCTURE
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Documents
27
Citations
192
h-index
7
Documents
97
Citations
1636
Scholarly Output
30
Articles
17
Views / Downloads
16716/11973
Supervised MSc Theses
5
Supervised PhD Theses
2
WoS Citation Count
74
Scopus Citation Count
83
Patents
0
Projects
4
WoS Citations per Publication
2.47
Scopus Citations per Publication
2.77
Open Access Source
19
Supervised Theses
7
| Journal | Count |
|---|---|
| IEEE Transactions on Instrumentation and Measurement | 4 |
| AEU - International Journal of Electronics and Communications | 2 |
| Proceedings - Linear Accelerator Conference, LINAC | 2 |
| Journal of Electromagnetic Waves and Applications | 2 |
| EPJ Techniques and Instrumentation | 1 |
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30 results
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Now showing 1 - 10 of 30
Article Citation - WoS: 4Citation - Scopus: 4Electromagnetic Simulations of Mechanical Imperfections for Accelerator Cavities(Institute of Electrical and Electronics Engineers Inc., 2019) Karatay, Anıl; Yaman, FatihEffects of surface roughness and transversal cell misalignments on the performance of elliptical accelerator cavities are studied in this article. A high-beta, 9-cell elliptical cavity, whose pi-mode resonates at 3.9 GHz, is designed to investigate imperfections. The considered frequency is chosen to observe variations of fundamental accelerating cavity parameters, wake potentials, and wake impedances more clearly by using relatively small structures. Moreover, 3-cell elliptical cavities having pi-mode at 2 and 3.9 GHz are designed to confirm the 9-cell cavity results. The undesired effects caused by the considered mechanical imperfections are simulated for an ultra-relativistic bunch in the parameter scope of a realistic scenario. In particular, Huray's snowball model, which is a scattering-based surface roughness approach developed for microstrip lines, is employed to determine the effects of the surface roughness on the accelerator cavities. Surface roughness due to the fabrication process is expressed as a surface impedance, and the required equivalence between the surface roughness and surface impedance concept is achieved. Significant computational efficiency is observed by using the surface impedance concept with Huray's snowball model in the simulations. Experimental verification of certain parameters is included for an elliptical cavity having high cell-to-cell coupling at 3.9 GHz.Editorial Recent Theory and Applications on Inverse Problems 2014(Hindawi Publishing Corporation, 2015) Yaman, Fatih; Yakhno, Valery G.; Özdemir, Caner; Yu, Tzu-Yang; Potthast, RolandThis special issue presents some very interesting recent developments in the area of inverse problems.The scope of the issue covers wide range of disciplines, for example, electromagnetics, acoustics, heat conduction, and image processing, from theory and application point of view. In the following, we give very brief descriptions of the published papers.Conference Object Citation - Scopus: 2Rf Measurements and Tuning of the Test Module of 800 Mhz Radio-Frequency Quadrupole(JACoW Publishing, 2022) Kılıçgedik, A.; Adıgüzel, A.; Esen, S.; Baran, B.; Çağlar, A.; Çelebi, E.; Özcan, V. E.; Kaya, U.; Türemen, G.; Ünel, N. G.; Yaman, FatihThe 800 MHz RFQ (radio-frequency quadrupole), developed and built at KAHVElab (Kandilli Detector, Accelerator and Instrumentation Laboratory) at Bogazici University in Istanbul, Turkey, has been designed to provide protons that have an energy of 2 MeV within only 1 m length. The RFQ consists of two modules and the test module of RFQ was constructed. The algorithm developed by CERN, based on the measurements generated by the tuner settings estimated through the response matrix [1, 2, 3], has been optimized for a single module and 16 tuners. The desired field consistent with the simulation was obtained by bead-pull measurements. In this study, we present low-power rf measurements and field tuning of the test module. © 2022 Proceedings - Linear Accelerator Conference, LINAC. All rights reserved.Article Balance of Bunch Compression and Emittance Preservation for High-Brightness X-Ray Free Electron Laser Injectors(Amer Physical Soc, 2025) Davut, C.; Apsimon, O.; Hounsell, B. R.; Militsyn, B. L.; Cowie, L. S.; Yaman, F.; Williams, P. H.This paper presents two conceptual low-energy injector configurations optimized for high-brightness, high-repetition-rate XFELs. The designs were evaluated at a nominal bunch charge of 150 pC using multiobjective optimization techniques and further assessed through start-to-end simulations incorporating collective effects to determine their suitability for delivering high-brightness beams under FEL-relevant conditions. One of the injector design configurations employs a hybrid rf and magnetic compression scheme, while the second relies solely on two-stage rf compression. Start-to-end simulations through the main linac, including collective effects, were performed to assess the suitability of each design for meeting XFEL requirements. The results highlight the critical role of longitudinal charge distribution symmetry in maintaining beam quality during acceleration and compression, and demonstrate that appropriately balancing compressibility, emittance preservation, and phase space linearity is essential for meeting the stringent demands of XFEL operation.Article Citation - WoS: 3Citation - Scopus: 3Inhomogeneity Reconstructions in Tendon Ducts Via Boundary Integral Equations(Elsevier Ltd., 2014) Yaman, Fatih; Weiland, Thomas W.In this study, as an alternative to the formerly presented investigations, Newton-type numerical algorithms are proposed to find location and shape of an air void inside of a tendon duct and to identify gathered metallic bars in a concrete column. The simulated structures are illuminated by four acoustic sources at a fixed frequency such that the scattered field is measured in a near-field region at 128 points. According to the nature of physical problems, the Dirichlet boundary condition is employed to model air-filled cavities and transmission conditions are assumed for metallic objects. Additionally, conductive boundary conditions are suggested for a more realistic representation of the inhomogeneities for the rusty metallic skin of the duct. Potential approaches are used to derive boundary integral equations. The proper treatment of the ill-conditioned equations is established via Tikhonov regularization. Applicability of the proposed inversion algorithms is tested with realistic parameters for different scenarios using noisy scattered field data and accurate numerical results are presented at 10 kHz for the unknown physical properties of the duct's skin.Article Numerical Investigations of Resistive Wall Wake Potentials(Institution of Engineering and Technology, 2020) Yaman, FatihThe aim of this Letter is to examine and identify longitudinal resistive wall wake potential behaviours of medium-beta long bunches and ultra-relativistic short bunches using different beam and pipe properties for particle accelerator applications. The lack of detailed analysis in current literature for the chosen set of parameters ignites this work. Since computations of wake potentials for the considered beam parameters by particle-in-cell codes are extremely difficult the author uses an analytical approach. Numerical integrations are evaluated for large domains with fine discretisations. The author observes that conductivity of beam pipe has a larger impact on medium-beta long bunches, variation of beam velocity effects wakes of short bunches more significantly, beam radii changes may have a contribution to instability for low energy short bunches. Interesting numerical results are presented and their physical explanations are discussed in this Letter.Article Citation - WoS: 3Citation - Scopus: 4Cost-Effective Experiments With Additively Manufactured Waveguide and Cavities in the S-Band(Iop Publishing Ltd, 2023) Karatay, Anıl; Yilmaz, Hasan Önder; Özkal, Ceren; Yaman, FatihThis study demonstrates the applicability of additively manufactured components that are metalized with conductive tape for two different microwave experiments. We focus on dielectric measurements and prototyping elliptical accelerator cavities at a low power regime for 2.45 GHz. To illustrate the accuracy of our results for the commonly used solid/liquid materials in engineering and to compare the fundamental accelerator cavity parameters with previous research rectangular and elliptic 3D-printed cavities coated with aluminum-type tape were employed in the experiments. Results reported for the complex-valued permittivities and specific design parameters for the cavity prototype are consistent with the literature. Various approaches to obtain the conductivity value of the tape and the effect of the roughness/thickness of the coating on the reflection parameter are discussed in detail. We confirm the effectiveness of the proposed approach, which reduces costs and provides a high degree of accuracy for investigated applications.Article Citation - Scopus: 2Mixture-Based Dielectric Permittivity Measurements Through Gallium-Excited Cavities(Ieee-inst Electrical Electronics Engineers inc, 2024) Karatay, Anil; Yaman, FatihIn dielectric measurements within resonant cavities, analytical perturbation methods encounter limitations, particularly with nonstandard cavity shapes and lossy materials under test (MUTs) having high dielectric constant. In such cases, the demand for iterative techniques to improve accuracy and flexibility is evident, but the efficiency of the existing iterative techniques, relying on numerical electromagnetic solvers, is often compromised, particularly in terms of time. Therefore, we introduce a novel methodology for measuring the permittivity of dielectric materials using liquid mixtures. This novel method employs a rapid iterative technique in which effective permittivity values are reconstructed at each iteration step based on the volume fraction of liquid mixtures, thus eliminating the dependence on time-consuming 3-D numerical solvers. In addition, we aim to achieve dual-band measurements at 2.45 and 5.8 GHz, enhancing precision by separating mode frequencies. Introducing a re-entrant cavity-like structure, we position the first mode at 2.45 GHz and the second at 5.8 GHz, effectively mitigating intermodal crosstalk and ensuring measurement accuracy. Also, for the first time in the literature, determining which mode will be excited in a cavity by the coupler probe made of gallium can be achieved through the displacement of the liquid metal, which enables measurements to be taken exclusively at the desired frequency.Doctoral Thesis Active metasurface designs for tunable scattering properties(01. Izmir Institute of Technology, 2024) Yılmaz, Hasan Önder; Altınkaya, Mustafa Aziz; Yaman, FatihGelişen teknolojiler, elektromanyetik dalgaların saçılmasını ve özelliklerini kontrol etmek için, doğal yapıların ötesinde özelliklere sahip yapay olarak tasarlanmış dinamik yüzeylere ihtiyaç duymaktadır. Bu tez, geçirgen bir metayüzey üzerinde oluşturulan yüzey dalgaları aracılığıyla yayılan dalgaların dinamik kontrolü için yeni bir yöntem önererek, bunun karşıt olmayan iletim ve yeniden yapılandırılabilir radyasyon problemlerine uygulanmasını içermektedir. Bu çalışma, faz eşlenik yüzeyler ve bianizotropiye dayalı analitik model için bir tasarım metodolojisi ve çift negatif indeks ortamına dayalı metayüzey kavramını içeren mikrodalga alanındaki üç boyutlu gerçekleştirme modeli önererek literatüre katkıda bulunmaktadır. Tez, ilk olarak sayısal simülasyonlarla desteklenen analitik çözümleri ve ardından pasif ve dinamik üç boyutlu modellerin tasarımları ve simülasyon sonuçlarını sunmaktadır. Empedans tabanlı karakterizasyon hem zaman bağımlı ve hem de zaman bağımsız birim hücre modelleri için uygulanmaktadır. Bunu, elde edilen empedanslar aracılığıyla zamana dayalı eşdeğer devrenin geliştirilmesi ve oluşturulması izlemektedir. Geliştirilen bu eşdeğer devre, zaman modülasyonlu birim hücrenin sayısal çözümünde kullanılmaktadır. Karşıt olmayan iletim için, uyarım yönüne bağlı olarak bianizotropik metayüzey üzerinde üretilen antisimetrik yüzey dalgalarına uygulanan zaman modülasyonuna dayalı yeni bir yöntem önerilmiştir. Bu yöntemin uygulanabilirliği, değişken bir kapasitör içeren bir yüzey kavitesi ile sınırlanmış geçirgen birim hücre üzerinde gösterilmiştir. Sayısal simülasyon sonuçları zaman modülasyonu yoluyla hem faz uyumlu hem de faz uyumsuz karşıt olmayan iletimi göstermektedir ve bunlar tutarlı deney sonuçlarıyla desteklenmektedir. Son bölümde, yeniden yapılandırılabilir radyasyon uygulamaları için yüzey dalgalarını kullanarak metayüzeyin birim hücrelerindeki faz değişimleri yoluyla dalga cephesi manipülasyonu araştırılmaktadır. Özel olarak, bir korna anten tarafından beslenen metayüzeyden yayılan hüzmenin açısal yönlendirilmesine odaklanılmaktadır. Önerdiğimiz yönteme dayalı yeni bir 3B tasarım modeli tanıtılmaktadır. Bu tasarım ile, kolonları elektriksel olarak ayıran kazınmış yarıklara yerleştirilmiş değişken kapasitörler ile basitleştirilmiş bir kontrol şeması önerilmektedir. Periyodik sınır koşulları altında uyarılmış yüzey modlarını incelemek için numerik özdeğer analizleri, ve ardından hüzme yönlendirme uygulaması için korna antenle entegrasyonunun simülasyonları gerçekleştirilmiştir. Simülasyonlardan ve kavram kanıtı deneylerinden elde edilen sonuçlar yayılan hüzmenin yönlendirilmesini göstermektedir.Conference Object Citation - WoS: 1An Origami-Inspired Low-Cost Waveguide Design, Fabrication and Measurements for X-Band Satellite Communication Systems(IEEE, 2023) Karatay, Anıl; Ataç, Enes; Yaman, FatihIn many applications such as satellite communication, transmission lines are required and waveguides are widely used in these applications. This passive component, which is an indispensable element of microwave systems, is generally not suitable for practical and low-cost applications due to being produced from costly and heavy metals. Therefore, nowadays, the tendency to use low-cost, light and practical components has increased. In this study, origami-inspired waveguide design for X-band satellite communication systems is aimed. This component, which is formed by folding a paper into a three-dimensional structure and covering it with a conductive material, is both practical and fast to produce, portable and adjustable. The obtained simulation results match well with the experimental results, and it has been proven that the paper-based waveguide performs as well as the conventional aluminum waveguide. This makes the proposed method an innovative and cost-effective solution for waveguide fabrication.
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