The Two-Screen Measurement Setup to Indirectly Measure Proton Beam Self-Modulation in AWAKE

The goal of the first phase of the AWAKE \cite{AWAKE1,AWAKE2} experiment at CERN is to measure the self-modulation \cite{SMI} of the $\sigma_z = 12\,\rm{cm}$ long SPS proton bunch into microbunches after traversing $10\,\rm{m}$ of plasma with a plasma density of $n_{pe}=7\times10^{14}\,\rm{electrons/cm}^3$. The two screen measurement setup \cite{Turner2016} is a proton beam diagnostic that can indirectly prove the successful development of the self-modulation of the proton beam by imaging protons that got defocused by the transverse plasma wakefields after passing through the plasma, at two locations downstream the end of the plasma. This article describes the design and realization of the two screen measurement setup integrated in the AWAKE experiment. We discuss the performance and background response of the system based on measurements performed with an unmodulated Gaussian SPS proton bunch during the AWAKE beam commissioning in September and October 2016. We show that the system is fully commissioned and adapted to eventually image the full profile of a self-modulated SPS proton bunch in a single shot measurement during the first phase of the AWAKE experiment.Comment: 5 pages 8 figure

Dilution Effects in Two-dimensional Quantum Orbital System

We study dilution effects in a Mott insulating state with quantum orbital degree of freedom, termed the two-dimensional orbital compass model. This is a quantum and two-dimensional version of the orbital model where the interactions along different bond directions cause frustration between different orbital configurations. A long-range correlation of a kind of orbital at each row or column, termed the directional order, is studied by means of the quantum Monte-Carlo method. It is shown that decrease of the ordering temperature due to dilution is much stronger than that in spin models. Quantum effect enhances the effective dimensionality in the system and makes the directional order robust against dilution. We discuss an essential mechanism of the dilute orbital systems.Comment: 5pages, 4 figure

Colligative properties of solutions: II. Vanishing concentrations

We continue our study of colligative properties of solutions initiated in math-ph/0407034. We focus on the situations where, in a system of linear size $L$, the concentration and the chemical potential scale like $c=\xi/L$ and $h=b/L$, respectively. We find that there exists a critical value \xit such that no phase separation occurs for \xi\le\xit while, for \xi>\xit, the two phases of the solvent coexist for an interval of values of $b$. Moreover, phase separation begins abruptly in the sense that a macroscopic fraction of the system suddenly freezes (or melts) forming a crystal (or droplet) of the complementary phase when $b$ reaches a critical value. For certain values of system parameters, under ``frozen'' boundary conditions, phase separation also ends abruptly in the sense that the equilibrium droplet grows continuously with increasing $b$ and then suddenly jumps in size to subsume the entire system. Our findings indicate that the onset of freezing-point depression is in fact a surface phenomenon.Comment: 27 pages, 1 fig; see also math-ph/0407034 (both to appear in JSP

Indirect Self-Modulation Instability Measurement Concept for the AWAKE Proton Beam

AWAKE, the Advanced Proton-Driven Plasma Wakefield Acceleration Experiment, is a proof-of-principle R&D experiment at CERN using a 400 GeV/c proton beam from the CERN SPS (longitudinal beam size sigma_z = 12 cm) which will be sent into a 10 m long plasma section with a nominal density of approx. 7x10^14 atoms/cm3 (plasma wavelength lambda_p = 1.2mm). In this paper we show that by measuring the time integrated transverse profile of the proton bunch at two locations downstream of the AWAKE plasma, information about the occurrence of the self-modulation instability (SMI) can be inferred. In particular we show that measuring defocused protons with an angle of 1 mrad corresponds to having electric fields in the order of GV/m and fully developed self-modulation of the proton bunch. Additionally, by measuring the defocused beam edge of the self-modulated bunch, information about the growth rate of the instability can be extracted. If hosing instability occurs, it could be detected by measuring a non-uniform defocused beam shape with changing radius. Using a 1 mm thick Chromox scintillation screen for imaging of the self-modulated proton bunch, an edge resolution of 0.6 mm and hence a SMI saturation point resolution of 1.2 m can be achieved.Comment: 4 pages, 4 figures, EAAC conference proceeding

Mean-field driven first-order phase transitions in systems with long-range interactions

We consider a class of spin systems on $\Z^d$ with vector valued spins (\bS_x) that interact via the pair-potentials J_{x,y} \bS_x\cdot\bS_y. The interactions are generally spread-out in the sense that the $J_{x,y}$'s exhibit either exponential or power-law fall-off. Under the technical condition of reflection positivity and for sufficiently spread out interactions, we prove that the model exhibits a first-order phase transition whenever the associated mean-field theory signals such a transition. As a consequence, e.g., in dimensions $d\ge3$, we can finally provide examples of the 3-state Potts model with spread-out, exponentially decaying interactions, which undergoes a first-order phase transition as the temperature varies. Similar transitions are established in dimensions $d=1,2$ for power-law decaying interactions and in high dimensions for next-nearest neighbor couplings. In addition, we also investigate the limit of infinitely spread-out interactions. Specifically, we show that once the mean-field theory is in a unique ``state,'' then in any sequence of translation-invariant Gibbs states various observables converge to their mean-field values and the states themselves converge to a product measure.Comment: 57 pages; uses a (modified) jstatphys class fil

Optimal designs for rational function regression

We consider optimal non-sequential designs for a large class of (linear and nonlinear) regression models involving polynomials and rational functions with heteroscedastic noise also given by a polynomial or rational weight function. The proposed method treats D-, E-, A-, and $\Phi_p$-optimal designs in a unified manner, and generates a polynomial whose zeros are the support points of the optimal approximate design, generalizing a number of previously known results of the same flavor. The method is based on a mathematical optimization model that can incorporate various criteria of optimality and can be solved efficiently by well established numerical optimization methods. In contrast to previous optimization-based methods proposed for similar design problems, it also has theoretical guarantee of its algorithmic efficiency; in fact, the running times of all numerical examples considered in the paper are negligible. The stability of the method is demonstrated in an example involving high degree polynomials. After discussing linear models, applications for finding locally optimal designs for nonlinear regression models involving rational functions are presented, then extensions to robust regression designs, and trigonometric regression are shown. As a corollary, an upper bound on the size of the support set of the minimally-supported optimal designs is also found. The method is of considerable practical importance, with the potential for instance to impact design software development. Further study of the optimality conditions of the main optimization model might also yield new theoretical insights.Comment: 25 pages. Previous version updated with more details in the theory and additional example

Superconductivity and charge carrier localization in ultrathin La1.85Sr0.15CuO4/La2CuO4\mathbf{{La_{1.85}Sr_{0.15}CuO_4}/{La_2CuO_4}} bilayers

$\mathrm{La_{1.85}Sr_{0.15}CuO_4}$/$\mathrm{La_2CuO_4}$ (LSCO15/LCO) bilayers with a precisely controlled thickness of N unit cells (UCs) of the former and M UCs of the latter ([LSCO15\_N/LCO\_M]) were grown on (001)-oriented {\slao} (SLAO) substrates with pulsed laser deposition (PLD). X-ray diffraction and reciprocal space map (RSM) studies confirmed the epitaxial growth of the bilayers and showed that a [LSCO15\_2/LCO\_2] bilayer is fully strained, whereas a [LSCO15\_2/LCO\_7] bilayer is already partially relaxed. The \textit{in situ} monitoring of the growth with reflection high energy electron diffraction (RHEED) revealed that the gas environment during deposition has a surprisingly strong effect on the growth mode and thus on the amount of disorder in the first UC of LSCO15 (or the first two monolayers of LSCO15 containing one $\mathrm{CuO_2}$ plane each). For samples grown in pure $\mathrm{N_2O}$ gas (growth type-B), the first LSCO15 UC next to the SLAO substrate is strongly disordered. This disorder is strongly reduced if the growth is performed in a mixture of $\mathrm{N_2O}$ and $\mathrm{O_2}$ gas (growth type-A). Electric transport measurements confirmed that the first UC of LSCO15 next to the SLAO substrate is highly resistive and shows no sign of superconductivity for growth type-B, whereas it is superconducting for growth type-A. Furthermore, we found, rather surprisingly, that the conductivity of the LSCO15 UC next to the LCO capping layer strongly depends on the thickness of the latter. A LCO capping layer with 7~UCs leads to a strong localization of the charge carriers in the adjacent LSCO15 UC and suppresses superconductivity. The magneto-transport data suggest a similarity with the case of weakly hole doped LSCO single crystals that are in a so-called {"{cluster-spin-glass state}"

Principlesand technology competence approach to formation of professional career students

У статті аналізується питання кар’єрного становлення студентської молоді, обґрунтовуються переваги компетентнісного підходу до формування та розвитку відповідного рівня знань і вмінь у сфері кар’єрного самовизначення.Виявлено, що кар’єрна компетентність, як особлива конфігурація ментальних та практичних характеристик суб’єктів кар’єрних процесів, формується на основі методології компетентнісного підходу. Його підґрунтям є ключові ідеї, які відображають практико-зорієнтований шлях набуття молодими людьми відповідних навичок, принципи визначальних освітніх орієнтирів та засадничих вимог у підготовці майбутніх фахівців і розгалужена система операційних процедур формування конкурентоспроможного фахівця. З’ясовано, що знання, які сьогодні отримують студенти, знаходяться під загрозою швидкої втрати актуальності. Відповідно існує нагальна потреба підготовки майбутніх фахівців, які б швидко адаптувались до нових професійних та кар’єрних викликів. Запропоновано авторську модель формування кар’єри студентської молоді, заснованої на основних методологічних вимогах та принципах компетентнісного підходу. У моделі презентовані діагностично-інформаційний, прогностично-формуючий, навчально-пізнавальний і організаційно-комунікативний блоки формування кар’єрної компетентності студентської молоді, визначено  технології, методи, алгоритми, які становлять комплекс практичних заходів у системі підготовки майбутніх фахівців.  В статье анализируются вопросы карьерного становления студенческой молодежи, обосновываются преимущества компетентностного подхода к формированию и развитию соответствующего уровня знаний и умений в сфере карьерного самоопределения. Выявлено, что карьерная компетентность, как особая конфигурация ментальных и практических характеристик субъектов карьерных процессов, формируется на основе методологии компетентностного подхода. Его опорой являются ключевые идеи, которые отражают практико-ориентированный путь обретения молодыми людьми соответствующих навыков, принципы определяющих образовательных ориентиров и основных требований к подготовке будущих специалистов и разветвленная система операционных процедур формирования конкурентоспособного специалиста.Выяснено, что знания, которые сегодня получают студенты, находятся под угрозой быстрой потери актуальности. Соответственно существует настоятельная необходимость подготовки будущих специалистов, которые были бы способны быстро адаптироваться к новым профессиональным и карьерным вызовам. Предложена авторская модель формирования карьеры студенческой молодежи, базирующаяся на методологических требованиях и принципах компетентностного подхода. В модели представлены информационный, формирующий, познавательный и коммуникативный блоки формирования карьерной компетентности студенческой молодежи, определены технологии, методы, алгоритмы, которые составляют комплекс практических мероприятий в системе подготовки будущих специалистов.The need of training of professionals, who are able not only to productive work, but also to compete successfully with others and build their career path according to their own preferences is an urgent challenge.A tool in the process of competition in the labor market is a career competence, which is formed during training in a higher education. The basis of its discovery is a competence-based approach as a set of ideas that provide the orientation of educational process to the demands of the labor market, the principles that define the basic guidelines in the preparation of competitive specialists and a set of tools to help you ensure the transfer of knowledge in the field of career development.The benefits of this study are in logical sequence of considered questions. The article defines the concept of «career competence», which is understood as an integral characteristic of the subject’s career that measures the ability to solve typical and innovative professional and non-professional tasks in productive, life, communicative situations. Competency approach reviewed on the methodological basis and the principles of its application in the formation of career competence developed, namely the principle of educational and market congruence, the principle of practical orientation of educational process, the principle of institutionalization of the career orientation of students and the principle of monitoring and evaluation of actual and achieved levels of career competence.The article proposed the technological model of the students career competence formation, the goal is allocated to the basic blocks and appropriate technologies, algorithms, methods of forming of career competence. In the presented model the diagnostic and informative block includes procedures for career counseling and guidance in career processes, the prognostically-forming unit focuses on choosing a portfolio career and forming individual career development plan, the training and educational block aimed at systemic accumulation of resources for career growth, the organizational and communicative one covers the cooperation with employers.In general, the article features acquired theoretical justification of career development of students in conjunction with practical mechanisms for achieving the appropriate level of career competence.