M.S. Theses

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3 - D optical profilometry at micron scale with modified fiber optic Lloyd's mirror technique
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2017., 2017.) İnanç, Arda.; İnci, Naci.
In this thesis, it is shown that a modiﬁed ﬁber optic Lloyd’s mirror technique is suitable and practical to produce fringe patterns that have easily adjustable frequency. This allows measuring 3D height distribution of test objects at micron scale without using additional elements as part of the optical projection unit. To test the validity of the proposed method, images that contain deformed fringe patterns due to the height distribution of micron scale test objects are recorded by a CCD camera and analysed with one dimensional continuous wavelet transform. After the extraction of phase map using 1D continuous wavelet transform, the height dis tribution of the test objects is obtained by further analyses. Finally, the results are discussed and compared with the expected values.
3+1 formulation in Newton-Cartan gravity
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Aras, Ulaş.; Bleeken, Dieter Van den.
In this thesis, we will give a review of torsion-free Newton- Cartan theory. We will start by doing a large c expansion of general relativity and we will restrict ourselves to a few leading orders. After obtaining Newton-Cartan theory in this way, we will explore its symmetries. Through a special set of combined symmetries, we will construct a split space and time structure. Lastly, we will work out the field equations and equations of motion for a particle in the 3+1 formulation we have obtained.
3D optical profilometry with a double beam - splitter setup
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2019., 2019.) Çetin, İsra Merve.; İnci, Naci.
In this thesis, it is demonstrated that a double beam splitter arrangement is very convenient and more practical to generate square shaped fringe patterns, and fringe distribution can be easily controlled in two dimensions. This enables to extract 3D height distribution of test objects without using any additional component as a projection unit. To approve the validity of the proposed technique, various frequencies of the fringe pattern are obtained by rotating a cubic beam splitter, and images that include deformed fringe patterns due to the height distribution of test objects are captured by a CCD camera. The resultant square fringe pattern is analyzed with two-dimensional continuous wavelet transform method and is separated into two fringe patterns in horizontal and vertical axes with a certain algorithm. The height-related phase map is acquired after analysis process.
A compilation of dualities between 4D N=2 supersymmetric gauge theories and 2D conformal field theories
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2019., 2019.) Kurşun, A. Kerem.; Kozçaz, Can.
In this thesis AGT-W conjecture is reviewed. AGT conjecture is a phenomenon which is shown by Luis F. Alday, Davide Gaiotto and Yuji Tachikawa in their paper published in 2009. It relates the partition functions of both N = 2 supersymmetric U(2), SU(2) gauge theories and Liouville ﬁeld theory which is a type of conformal ﬁeld theory. One month later, Niclas Wyllard extended the conjecture and proved the connection between N = 2 supersymmetric SU(N) gauge theories and AN−1 Toda ﬁeld theories. In addition to AGT-W conjecture, gauge/Liouville Triality, spectral duality and 2D/4D duality through Nekrasov-Shatashvili limit are summarized. N = 2 supersymmetric gauge theories are also studied in type IIA, IIB and topological string theory background.
A new tracking algorithm for atlas trigger
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2012., 2012.) Sarıkaya, Saime.; Özcan, Veysi Erkcan.
The Large Hadron Collider (LHC) is the world's highest energy accelerator with the highest luminosity, which aims to nd answers to the most fundamental questions of particle physics. It leads us to the discoveries of new particles (e.g discovery of Higgs boson nowadays), as predicted by Standard Model and its extensions like supersymmetry. However, coping up with the data produced by the LHC, and nding the interesting events, is not an easy task. LHC produces 1TB of data per second and approximately only 1 event per million is from interesting physics. At this point, looking for an event in the whole data is like trying to nd a needle in the haystack and to nd the interesting events out of the entire data, trigger systems are used. One of the most important part of trigger is tracking, which one needs to identify the tracks made by particles, and to identify the physics objects in the event. In this thesis, we describe an algorithm, to run at one of the LHC detectors, ATLAS, in order to achieve fast tracking. The algorithm is tested, using very high luminosity simulation data both running on hits obtained from the entire detector and also in certain small regions around interesting signals. The performance is shown to be satisfactory both in terms of tracking e ciency and in terms of timing requirements.
A permanent-magnet microwave discharge ion source at KAHVELab
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Açıksöz, Sevim.; Özcan, Veysi Erkcan.; Çetinkaya, Hakan.
A new Permanent Magnet Microwave Discharge Ion Source (PM-MDIS) has been designed and constructed at Boğaziçi University Kandilli Detector, Accelerator, and Instrumentation Laboratory (KAHVELab). The PM-MDIS design includes a plasma chamber surrounded by permanent magnets, a hydrogen gas supply to sustain the plasma, the waveguide system used to transfer power to the plasma chamber, a dualelectrode extraction system used to extract ions from the chamber, and a Faraday cup to measure the beam current. The aim is to extract ions from the thermal hydrogen plasma generated using a 2.45 GHz microwave source. In order to extract ions from the plasma medium, a magnetic field exceeding 875G has to be applied over the plasma chamber to ensure Electron Cyclotron Resonance (ECR) condition is satisfied. Since the plasma chamber is to be operated on the high voltage (HV) platform, higher system stability can be achieved by using the permanent magnet configuration shown in this work. Based on the designed magnetic field profile of the constructed system, the dual-electrode extraction system has also been designed using IBSIMU integrated DemirciPro software and produced to transmit proton beams from the plasma chamber to the beamline. The determination of the magnetic field profile, and the vacuum, HV, and beam tests are completed before integration with the rest of the beamline. Finally, how the transmitted proton beams behaved on the existing Low Energy Beam Transport (LEBT) line has been examined, and the LEBT line configuration has been optimized accordingly. In addition, besides the protons, the trajectories of H+ 2 and H+ 3 ions from the PM-MDIS have also been studied to optimize the LEBT beam optics. As a result of this study, the PM-MDIS has been integrated with the proton beamline, and 0.38mA mean beam current has been measured with the Faraday cup in the experiments performed at 20 kV and 0.01 sccm gas flow.
A search for vector-like leptons in ATLAS Run 2 data
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2021., 2021.) Örgen, Bora.; Özcan, Veysi Erkcan.; Ünel, N. Gökhan.
The search for pair-produced heavy iso-singlet leptons predicted by Grand Unified Theory (GUT) based on group E6 is detailed in this study. The discovery channel through which the search has been conducted is pp→L_e L ‾_e→ZeWν_e→3l 2j E_T^miss. The data used in the study is the ATLAS Run 2 data which has an integrated luminosity of L=139 fb^(-1) from proton-proton collisions at 13 TeV center of mass-energy. A cut-based event selection has been performed to maximize signal to background yields. Exclusion limits without systematic uncertainties have been obtained, and the results have been found to be promising with the possibility to increase the lower mass limit of the heavy charged lepton to about 250 GeV from the previous limit of 100 GeV.
A study of anomalous events in CMS-HF PMTs
(Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2009., 2009.) Halu, Arda.; Gülmez, Erhan.
The Forward Hadronic (HF) calorimeter of the CMS detector will measure the hadronic jets as well as determine the missing transverse energy generally attributed to new physics phenomena. HF is a quartz ber calorimeter in which the Cerenkov light generated by charged particles is collected by conventional photomultiplier tubes (PMT). In the HF test beam of 2004, events with unusually high energies with respect to the incoming beam energy were seen. These abnormal events were later con rmed in the 2007 test beam study. In this thesis, anomalous events are studied in various aspects, with more emphasis on the comparison of their electromagnetic (EM) and hadronic (HAD) channel signals. EM/HAD and HAD/EM energy ratio histograms are plotted for several pion and muon test runs with di erent beam momenta. Incident tower ratio histograms in the typical energy range display a clear peak, justifying the existence of a correlation while histograms of abnormally high energy events for the sum of all other towers do not exhibit such a relation. This observation might help us infer that these anomalous events, which most probably result from particles striking PMT windows directly instead of passing through bers to reach them, are of no experimental signi cance and may be tagged as \unreal" events to be discarded.
A study on the stability of the led gain monitoring system for the CMS-HF PMTs during 2009
(Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2010., 2010.) Özbek, Melih.; Gülmez, Erhan.
The Hadronic Forward (HF) calorimeter improves the jet detection and the missing transverse energy resolution of the Compact Muon Solenoid (CMS). In HF, the Photo Multiplier Tubes (PMTs) convert optical signals (i.e., Čerenkov light) to electrical signals. For monitoring the PMT gains, LED signals are extensively used. LED data collected throughout 2009 were thoroughly studied in this thesis. The focus was analyzing the stability of the LED system over time by graphical means. Also, by plotting the average charge versus position, it was possible to identify problematic channels.
Accretion discs around compact objects
(Thesis (M.S.)- Bogazici University. Institute for Graduate Studies in Science and Engineering, 1999., 1999.) Ekşi, K.Yavuz.; Ercan, E. Nihal.
Accretion onto a compact object is the process that is thought to power unexpectedly intense radiation of some astrophysical objects like Active Galactic Nuclei and X-Ray Binaries. A similar process is known to exist in Cataclysmic Variables and Young Stellar Objects. When the accreting matter has enough angular momentum it forms a disc around the compact object (a black hole, neutron star or white dwarf) and this disc is called an accretion disc. In this thesis accretion discs around compact objects are studied both analytically and numerically. Simplifying hydrodynamic equations in their full generality by the assumptions of the standart accretion disc theory, both time-independent and time-dependent equations were solved analytically. Time-dependent solutions are supported by numerical results. In all solutions a viscosity prescription which is a little more generalized than the standart prescription is used. The solution of the time-dependent equations with the generalized viscosity belong to the same family with the earlier ones.
Acoustic radiation enhanced drug delivery
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2015., 2015.) Yılmaz, Defne.; Ünlü, Mehmet Burçin.
Drug development is one of the main concerns in cancer research. In recent years, lots of new drugs have been discovered in order to increase the e ciency of cancer treatment and enhance the quality of patient's life. However, anti-cancer drugs, which are e ective in laboratory experiments, may not give positive results when they are injected to humans. Because of the abnormal vasculature in tumor microenvironment, drug particles face with several physiological barriers preventing the transport of therapeutic agents homogeneously from the region of administration to the cells in solid tumors. Recent studies have revealed that drug response of a tumor cell is determined by its biological characteristics and its microenvironment regulation. The abnormalities in tumor vasculature result in uneven drug distribution and blood ow within solid tumors. Moreover, the leaky, tortuous and highly permeable tumor vessels and the lack of functional lymphatic vessels lead to the elevated interstitial uid pressure (IFP). The use of radiation force is for the enhancement of drug delivery is an emerging method. Experimental studies have shown that radiation force can manipulate delivery vehicles in the vasculature by changing their velocities and positions. In the light of these experiments, a mathematical model which associates the e ect of acoustic radiation force for the convective transport and the drug distribution in tumors is constructed. Governing equations in the model involve the principles for transvascular and interstitial drug transport as well as conservation laws.
Active brownian particles propelled by sound
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2016., 2016.) Kaya, Serhat.; Ünlü, Mehmet Burçin.
Small particles in acoustic elds experience the so-called acoustic radiation forces by which the motion of particles can be manipulated in a contact-less way. Active Brownian particles have the ability to propel themselves by converting ambient energy into kinetic energy. However, because of the lack of study, the behavior of active Brownian particles in vicinity of external elds is not well-understood. The usage of acoustic elds in controlling the motion of these particles was suggested before, but this e ect has not been resolved analytically yet. In the analysis contained herein, the behavior of active particles inside an acoustic eld is investigated by constructing the equation of motion for a single particle. This is the rst time in the literature whereby the analytic form of the acoustic radiation forces is integrated with the dynamic equations of the system. The resulting equation is solved via numerical techniques. Then, with the performed simulations for two di erent active matter models, the collective behavior of active Brownian particles is also exploited.
AE AQR :|a DQ her type cataclysmic variable binary system
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 1998., 1998.) Erkut, M. Hakan.; Ercan, E. Nihal.
AE Aquarii, a DQ Her type Cataclysmic Variable X-ray binary system, is observed with rosat, PSPC in the energy range 0.1-2.4 keV with a total of 5.74 hr period. As a result of spectral and timing analyses of the ROSAT X-ray data of AE Aquarii, it is found that both a very low mass accretion rate of 8.59 x 10-13M yr-1 estimated from the X-ray luminosity and a QPO like structure obderved in the X-ray average power spectrum support the magnetic propeller scenario in which the gas blobs of the inhomogeneous accretion stream from the secondary star to the white dwarf are radiated thermally near the white dwarf surface because of the shock heating of the gas blobs at supersonic speeds in the high accretion state of AE Aquarii. On the other hand, the accreted gas particles are radiated magnetically in ~ 10 Gauss of magnetospere far away from the white dwarf surface during the low accretion states.
AGT and elliptic higgsed networks
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2020., 2020.) Ghoneim, Mohamed.; Kozçaz, Can.
In this thesis we want to introduce a current work in progress where elliptically deformed networks of DIM algebra intertwiners are used to obtain the partition function of 4d quiver gauge theories. To achieve this we start by introducing the relevant background of the AGT correspondence whose higher dimensional extension has the DIM algebra as its symmetry. The rst part then gives a review of the AGT relation as well as its higher dimensional extensions to 5 and 6d. Then part two begins with a brief of DIM algebra and how its itertwiners are used to build the Higgsed networks whose matrix elements give the partition function of 3d quiver gauge theories. Finally, we deform the algebra and use the deformed networks to obtain the 4d uplift of the 3d theories.
An attractive φ4 theory in light-front coordinates
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2019., 2019.) Yalnız, Gökhan; Turgut, Teoman.
We study an attractive φ4 interaction using Tamm-Dancoﬀ truncation with light-front coordinates in 3 + 1 dimensions. The truncated theory requires a coupling constant renormalization, we compute its β function non-perturbatively, show that the model is asymptotically free, and ﬁnd the corresponding Callan-Symanzik equations. The model supports bound states, we ﬁnd the wave function of the ground state of the two-particle sector. We also give a bound for the N-particle ground state energy within a mean ﬁeld approximation, including the corresponding result for the case of 2 + 1 dimensions where the model does not require renormalization.
An interferometric vibration sensor based on a four - core optical fiber
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2016., 2016.) Gökbulut, Belkıs.; İnci, Naci.
In this thesis, an interferometric fiber optic vibration sensor based on a four-core optical fiber is described. When the light is coupled into the four cores, each core acts as a mutually coherent waveguide with the other ones, which allows obtaining an interference fringe pattern at the far field. Vibrating a section of the four-core optical fiber causes a path difference between the light beams guiding in the separate cores, which results in a shift in the fringe pattern. Such a mechanism allows one to relate the fringe shift to the vibration amplitude and frequency. In this study, a source, which is capable to generate 100 Hz frequency sound waves is attached to the optical fiber to maintain vibration of the section of the fiber. A single slit and a photodetector are used to detect the shifting of the fringe pattern that causes a change in the phase of the guiding light. When a He-Ne laser beam is coupled into the optical fiber, the structured fringe pattern is projected onto the slit behind the photodetector, then a small part of the fringe pattern is analysed. Thus, an interferometric fiber optic vibration sensor based on a four-core optical fiber, which has a simple structure and high sensitivity, is accomplished.
Analysis of J / ψ ώπ π at BESIII
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2015., 2015.) Yüncü, Alperen.; Özcan, Veysi Erkcan.; Uman, İsmail Ruhi.
Using a sample of 1.3 billion J= events collected with the BESIII detector at the BEPCII storage ring, the decay channel J= ! ! 0 0 has been studied. Two of the lightest tetraquark candidates, f0(500) (a.k.a. ) and f0(980) have been searched for. A Dalitz Plot analysis has been performed and in additon to f0(500) ( ) and f0(980), f2(1270), b1(1325), (1450), and f2(2300) have been observed. The analysis and background study indicate that this channel is suitable for a detailed study of the resonances through a Partial Wave Analysis.
Approximate ground state energies of one dimensional potential wells by the s-matrix formalism
(Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2003., 2003.) Erkol, Hakan.; Beker, Haluk.
One dimensional potential wells are described as a collection of consecutive thin slices, each approximated by a Dirac delta well. Bound state energies of these Dirac delta well conglomerates are calculated, using a method based on Transfer and S-Matrix formalisms. It is observed that the method, a variant of the Born approximation, works best for the ground state energies of narrow and shallow wells. The approximate results compare favorably with the known exact results of several potential well problems.
Archaelogical provenancing of marble by pore size analysis, using phase transition porosimetry
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 1999., 1999.) Öztürk, M. Kaan.; Aktaş, Gülen, 1951- .; Özbal, Hadi.
Determination of the source of a particular marble sample is an ongoing subject of study among archaeometrists. In this study, categorization according to pore size distribution is suggested. The employed method for pore size analysis is Phase Transition Porosimetry (PTP). The principles on which PTP works are described. PTP requires a computer system for data taking and data processing. The electronic data-acquisition system and the control software are discussed extensively. After construction of a dilatometric Phase Transition Porosimeter, marble samples collected from field have been studied with this method and the results are given. The precision of PTP in low-porosity materials are discussed using the results.
Aspects of finite size effects on Bose-Einstein condensation
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2015., 2015.) Seymen, Sema.; Turgut, Teoman.
In this thesis, the number of particles calculations of Pathria for a 3 dimensional box is shortly reviewed. After that, the works of Toms and Kirsten which use the Mellin Barnes integral representation and heat kernel approximation to calculate the partition function summation is reviewed. Toms and Kirsten's approach is worked out in d dimension to calculate some thermodynamic quantities such as the number of particles, internal energy, heat capacity at constant volume and constant pressure, isothermal compressibility, adiabatic compressibility etc. The discontinuity of the heat capacity and the derivative of the heat capacity around the critical temperature is investigated. The results are checked at the bulk level to see that at d = 3 they are consistent with the ones given in Pathria. Lastly, the results are generalized to ps for s = 2k case and also an expression for the discontinuity of the heat capacity at constant volume is written.

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