Physical Sciences and Mathematics Commons^™

Fragmentation Of Fast Josephson Vortices And Breakdown Of Ordered States By Moving Topological Defects, Ahmad Sheikhzada, Alex Gurevich

Physics Faculty Publications

Topological defects such as vortices, dislocations or domain walls define many important effects in superconductivity, superfluidity, magnetism, liquid crystals, and plasticity of solids. Here we address the breakdown of the topologically-protected stability of such defects driven by strong external forces. We focus on Josephson vortices that appear at planar weak links of suppressed superconductivity which have attracted much attention for electronic applications, new sources of THz radiation, and low-dissipative computing. Our numerical simulations show that a rapidly moving vortex driven by a constant current becomes unstable with respect to generation of vortex-antivortex pairs caused by Cherenkov radiation. As a result, …

Corrigendum To "Suppression Of ϒ Production In D + Au And Au + Au Collisions At √Sɴɴ = 200 Gev" (Phys. Lett. B Vol 735 (2014) 127-137), J. Adamczyk, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, S. Bültmann

Physics Faculty Publications

No abstract provided.

Nlo Evolution Of 3-Quark Wilson Loop Operator, I. Balitsky, A. V. Grabovsky

Physics Faculty Publications

It is well known that the high-energy scattering of a meson from some hadronic target can be described by the interaction of that target with a color dipole formed by two Wilson lines corresponding to the fast quark-antiquark pair. Moreover, the energy dependence of the scattering amplitude is governed by the evolution equation of this color dipole with respect to rapidity. Similarly, the energy dependence of scattering of a baryon can be described in terms of evolution of a three-Wilson-line operator with respect to the rapidity of the Wilson lines. We calculated the evolution of the 3-quark Wilson loop operator …

The Heavy Photon Search Test Detector, M. Battaglieri, S. Boyarinov, S. Bueltmann, V. Burkert, A. Celentano, G. Charles, W. Cooper, C. Cuevas, N. Dashyan, R. Devita, L. B. Weinstein

Physics Faculty Publications

The Heavy Photon Search (HPS), an experiment to search for a hidden sector photon in fixed target electroproduction, is preparing for installation at the Thomas Jefferson National Accelerator Facility (JLab) in the Fall of 2014. As the first stage of this project, the HPS Test Run apparatus was constructed and operated in 2012 to demonstrate the experiment׳s technical feasibility and to confirm that the trigger rates and occupancies are as expected. This paper describes the HPS Test Run apparatus and readout electronics and its performance. In this setting, a heavy photon can be identified as a narrow peak in the …

Beam-Energy-Dependent Two-Pion Interferometry And The Freeze-Out Eccentricity Of Pions Measured In Heavy Ion Collisions At The Star Detector, L. Adamczyk, J.K. Adkins, G. Agakishiev, M.M. Aggarwal, Z. Ahammed, I. Koralt, Star Collaboration

Physics Faculty Publications

We present results of analyses of two-pion interferometry in Au + Au collisions at root s(NN) = 7.7, 11.5, 19.6, 27, 39, 62.4, and 200 GeV measured in the STAR detector as part of the BNL Relativistic Heavy Ion Collider Beam Energy Scan program. The extracted correlation lengths (Hanbury-Brown-Twiss radii) are studied as a function of beam energy, azimuthal angle relative to the reaction plane, centrality, and transverse mass (m(T)) of the particles. The azimuthal analysis allows extraction of the eccentricity of the entire fireball at kinetic freeze-out. The energy dependence of this observable is expected to be sensitive to …

Double Spin Asymmetries Of Inclusive Hadron Electroproduction From A Transversely Polarized He-3 Target, Y. X. Zhao, K. Allada, K. Aniol, J.R.M. Annand, T. Averett, F. Benmokhtar, M. Canan

Physics Faculty Publications

We report the measurement of beam-target double spin asymmetries (A_LT) in the inclusive production of identified hadrons, ^→e + ³He^↑ → h + X, using a longitudinally polarized 5.9-GeV electron beam and a transversely polarized ³He target. Hadrons (π^±, K^±, and proton) were detected at 16 ° with an average momentum ( P_h ) = 2.35 GeV/c and a transverse momentum (p_T) coverage from 0.60 to 0.68 GeV/c. Asymmetries from the He-3 target were observed to be nonzero for π^± production when the target was polarized …

E00-110 Experiment At Jefferson Lab Hall A: Deeply Virtual Compton Scattering Off The Proton At 6 Gev, M. Defurne, M. Amaryan, K. A. Aniol, M. Beaumel, H. Benaoum, P. Bertin, C. E. Hyde, P.E. Ulmer, Jefferson Lab Hall A Collaboration

Physics Faculty Publications

We present final results on the photon electroproduction (^→e p → epγ) cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region from Jefferson Lab experiment E00-110. Results from an analysis of a subset of these data were published before, but the analysis has been improved, which is described here at length, together with details on the experimental setup. Furthermore, additional data have been analyzed, resulting in photon electroproduction cross sections at new kinematic settings for a total of 588 experimental bins. Results of the Q² and x_B dependencies of both …

Λλ Correlation Function In Au + Au Collisions At √S(Nn)=200 Gev, L. Adamczyk, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, S. Bültmann, I. Koralt

Physics Faculty Publications

We present ΛΛ correlation measurements in heavy-ion collisions for Au + Au collisions at √s_NN = 200 GeV using the STAR experiment at the Relativistic Heavy-Ion Collider. The Lednicky-Lyuboshitz analytical model has been used to fit the data to obtain a source size, a scattering length and an effective range. Implications of the measurement of the ΛΛ correlation function and interaction parameters for dihyperon searches are discussed.

Measurement Of The Target-Normal Single-Spin Asymmetry In Quasielastic Scattering From The Reaction ³He↑(E, E'), Y. W. Zhang, E. Long, M. Mihoviloviĉ, G. Gin, M Canan, S. Golge, R. Schiavilla

Physics Faculty Publications

We report the first measurement of the target single-spin asymmetry, A_y, in quasielastic scattering from the inclusive reaction ³He↑(e, e') on a ³He gas target polarized normal to the lepton scattering plane. Assuming time-reversal invariance, this asymmetry is strictly zero for one-photon exchange. A nonzero A_y can arise from the interference between the one-and two-photon exchange processes which is sensitive to the details of the substructure of the nucleon. An experiment recently completed at Jefferson Lab yielded asymmetries with high statistical precision at Q² = 0.13, 0.46, and 0.97 GeV2. These measurements demonstrate, for the first …

Precision Measurement Of The Longitudinal Double-Spin Asymmetry For Inclusive Jet Production In Polarized Proton Collisions At √S= 200gev, L. Adamczyk, J.K. Adkins, G. Agakishiev, S. Bültmann, I. Koralt, Star Collaboration

Physics Faculty Publications

We report a new measurement of the midrapidity inclusive jet longitudinal double-spin asymmetry, A_LL, in polarized pp collisions at center-of-mass energy √s = 200 GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep-inelastic scattering (DIS), semi-inclusive DIS, and RHIC pp data. The measured asymmetries provide evidence at the 3σ level for positive gluon polarization in the Bjorken-x region x > 0.05.

Precision Measurements Of Aⁿ1 In The Deep Inelastic Regime, D. S. Parno, D. Flay, M. Posik, M. Canan, C. Hyde, The Jefferson Lab Hall A Collaboration

Physics Faculty Publications

We have performed precision measurements of the double-spin virtual-photon asymmetry A₁ on the neutron in the deep inelastic scattering regime, using an open-geometry, large-acceptance spectrometer and a longitudinally and transversely polarized ³He target. Our data cover a wide kinematic range 0.277 <= x <= 0.548 at an average Q² value of 3.078(GeV/c)², doubling the available high-precision neutron data in this xrange. We have combined our results with world data on proton targets to make a leading-order extraction of the ratio of polarized-to-unpolarized parton distribution functions for up quarks and for down quarks in the same kinematic range. Our data are consistent with …

Separated Response Functions In Exclusive, Forward Π± Electroproduction On Deuterium, G. M. Huber, H. P. Blok, A. Klein, L. M. Qin, K. Vansyoc, Jefferson Lab, Fπ Collaboration

Physics Faculty Publications

Background: Measurements of forward exclusive meson production at different squared four-momenta of the exchanged virtual photon, Q², and at different four-momentum transfer, t, can be used to probe QCD's transition from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales. Ratios of separated response functions in π^- and π⁺ electroproduction are particularly informative. The ratio for transverse photons may allow this transition to be more easily observed, while the ratio for longitudinal photons provides a crucial verification of the assumed pole dominance, needed for reliable extraction of the pion form …

Spectroscopy Of Li-9 (Lambda) By Electroproduction, G. M. Urciuoli, D. Hayes, C. E. Hyde, H. F. Ibrahim, P.E. Ulmer, Jefferson Lab Hall A Collaboration

Physics Faculty Publications

Background: In the absence of accurate data on the free two-body hyperon-nucleon interaction, the spectra of hypernuclei provides information on the details of the effective hyperon-nucleon interaction.

Purpose: To obtain a high-resolution binding-energy spectrum for the ⁹Be(e, e' K⁺)⁹_ΛLi reaction.

Method: Electroproduction of the hypernucleus ⁹_ΛLi has been studied for the first time with sub-MeV energy resolution in Hall A at Jefferson Lab on a ⁹Be target. In order to increase the counting rate and to provide unambiguous kaon identification, two superconducting septum magnets and a ring imaging Cherenkov detector were …

Towards A Resolution Of The Proton Form Factor Problem: New Electron And Positron Scattering Data, Clas Collaboration, D. Adikaram, L. B. Weinstein, R. P. Bennett, K. P, Adhikari, M. J. Amaryan, S. Careccia, L. El Fassi, C. E. Hyde, A. Klein, S E. Kuhn, M. Mayer, Z. W. Zhao

Physics Faculty Publications

There is a significant discrepancy between the values of the proton electric form factor, G^p_E, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of G^p_Efrom the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual …

High-Velocity Spoke Cavities, C. S. Hopper, Hyekyoung Park

Physics Faculty Publications

There are several current and recent projects which explore the feasibility of spoke-loaded cavities operating in the high-velocity region. Spoke cavities have a large number of geometric parameters which often influence multiple rf properties. Fabricating, handling, and processing these cavities presents some unique challenges, not unlike other TEM-class structures. This paper will summarize the current efforts toward the design, fabrication, and testing of spoke cavities with optimum beta greater than 0.8.

Development And Testing Of A 325 Mhz Β0= 0.82 Single-Spoke Cavity, C. S. Hopper, Hyekyoung Park, J. R. Delayen

Physics Faculty Publications

A single-spoke cavity operating at 325 MHz with geometric beta of 0.82 has been developed and tested. Initial results* showed high levels of field emission which limited the achievable gradient. Several rounds of helium processing significantly improved the cavity performance. Here we discuss the development process and report on the improved results.

Measurements Of Rf Properties Of Thin Film Nb3Sn Superconducting Multilayers Using A Calorimetric Technique, S. Sosa-Guitron, A. Gurevich, J. Delayen, E. Chang Beom, C. Sundahl, G. V. Eremeev

Physics Faculty Publications

Results of RF tests of NB₃SN thin film samples related to the superconducting multilayer coating development are presented. We have investigated thin film samples of Nb₃Sn/Al₂O₃/Nb with Nb₃Sn layer thicknesses of 50 nm and 100 nm using a Surface Impedance Characterization system. These samples were measured in the temperature range 4 K-19 K, where significant screening by Nb₃Sn layers was observed below 16-17 K, consistent with the bulk critical temperature of Nb₃Sn.

Crab Cavity And Cryomodule Development For Hl-Lhc, F. Carra, A. A. Carvalho, K. Artoos, S. Atieh, I. A. Santillana, S. Belomestnykh, A. Boucherie, J. P. Brachet, K. Brodzinski, G. Burt, S. U. De Silva, J. R. Delayen, R. Olave, H. Park

Physics Faculty Publications

The HL-LHC project aims at increasing the LHC luminosity by a factor 10 beyond the design value. The installation of a set of RF Crab Cavities to increase bunch crossing angle is one of the key upgrades of the program. Two concepts, Double Quarter Wave (DQW) and RF Dipole (RFD) have been proposed and are being produced in parallel for test in the SPS beam before the next long shutdown of CERN accelerator’s complex. In the retained concept, two cavities are hosted in one single cryomodule, providing thermal insulation and interfacing with RF coupling, tuning, cryogenics and beam vacuum. This …

A Facility For Magnetic Field Penetration Measurements On Multilayer S-I-S Structures, Oleg B. Malyshev, Lewis Gurran, Shrikant Pattalwar, Ninad Pattalwar, Keith D. Dumbell, Reza Valizadeh, Alex Gurevich

Physics Faculty Publications

Superconducting RF cavities made of bulk Nb has reached a breakdown field of about 200 mT which is close to the superheating field for Nb. As it was theoretically shown a multilayer coating can be used to enhance the breakdown field of SRF cavities. The simple example is a superconductor-insulator-superconductor (S-I-S), for example bulk niobium (S) coated with a thin film of insulator (I) followed by a thin layer of a superconductor (S) which could be a dirty niobium. To verify such an enhancement in a presence of a DC magnetic field at 4.2 K a simple experimental facility was …

Recent Developments In Superconducting Deflecting-Mode Cavities, J. R. Delayen

Physics Faculty Publications

In the last few years there has been a growing interest in compact superconducting cavities operating in a deflecting mode to be used either in rf separators or crabbing systems. This talk will give an overview of recent progress in global activities towards SRF deflecting mode cavities.

Engineering Design And Prototype Fabrication Of Hom Couplers For Hl-Lhc Crab Cavities, C. Zanoni, S. Atieh, I. Aviles Santillana, S. Belomestnykh, G. Burt, R. Calaga, S. U. De Silva, J. R. Delayen, R. Olave, H. Park

Physics Faculty Publications

The High-Luminosity upgrade for the LHC relies on a set of RF Crab Cavities for reaching its goals. Two parallel concepts, the Double Quarter Wave (DQW) and the RF Dipole (RFD), are going through a comprehensive design process along with preparation of fabrication in view of extensive tests with beam in SPS. High Order Modes (HOM) couplers are critical in providing damping in RF cavities for operation in accelerators. HOM prototyping and fabrication have recently started at CERN. In this paper, an overview of the final shape is provided along with an insight in the mechanical and thermal analyses performed …

Electromagnetic Design Of 400 Mhz Rf-Dipole Crabbing Cavity For Lhc High Luminosity Upgrade, S.U. De Silva, H. Park, J. R. Delayen, Z. Li

Physics Faculty Publications

The beam crabbing proposed for the LHC High Luminosity Upgrade requires two crabbing systems operating in both horizontal and vertical planes. In addition, the crabbing cavity design needs to meet strict dimensional constraints and functional specifications of the cavities. This paper presents the detailed electromagnetic design including em properties, multipole analysis, multipacting levels of the 400 MHz rf-dipole crabbing cavity.

Superconducting Cavity For The Measurements Of Frequency, Temperature, Rf Field Dependence Of The Surface Resistance, Hyekyoung Park, S.U. De Silva, J. R. Delayen

Physics Faculty Publications

In order to better understand the contributions of the various physical processes to the surface resistance of superconductors the ODU Center for Accelerator Science is developing a half-wave resonator capable of operating between 325 MHz and 1.3 GHz. This will allow the measurement of the temperature and rf field dependence of the surface resistance on the same surface over the range of frequency of interest for particle accelerators and identify the various sources of power dissipation.

Analysis Of A 750 Mhz Srf Dipole Cavity, Alejandro Castilla, J. R. Delayen

Physics Faculty Publications

There is a growing interest in using rf transverse deflecting structures for a plethora of applications in the current and future high performance colliders. In this paper, we present the results of a proof of principle superconducting rf dipole, designed as a prototype for a 750 MHz crabbing corrector for the Medium Energy Electron-Ion Collider (MEIC), which has been successfully tested at 4.2 K and 2 K at the Jefferson Lab’s Vertical Testing Area (VTA). The analysis of its rf performance during cryogenic testing, along with Helium pressure sensitivity, Lorentz detuning, surface resistance, and multipacting processing analysis are presented in …

Secondary Electron Yield Of Electron Beam Welded Areas Of Srf Cavities, M. Basovic, S. Popovic, M. Tomovic, L. Vuskovic, A. Samolov, F. Cuckov

Physics Faculty Publications

Secondary Electron Emission (SEE) is a phenomenon that contributes to the total electron activity inside the Superconducting Radiofrequency (SRF) cavities during the accelerator operation. SEE is highly dependent on the state of the surface. During electron beam welding process, significant amount of heat is introduced into the material causing the microstructure change of Niobium (Nb). Currently, all simulation codes for field emission and multipacting are treating the inside of the cavity as a uniform, homogeneous surface. Due to its complex shape and fabricating procedure, and the sensitivity of the SEE on the surface state, it would be interesting to see …

Experiment And Results On Plasma Etching Of Srf Cavities, J. Upadhyay, Do Im, J. Peshl, S. Popovic, L. Vuskovic, A. -M. Valente-Feliciano, L. Phillips

Physics Faculty Publications

The inner surfaces of SRF cavities are currently chemically treated (etched or electro polished) to achieve the state of the art RF performance. We designed an apparatus and developed a method for plasma etching of the inner surface for SRF cavities. The process parameters (pressure, power, gas concentration, diameter and shape of the inner electrode, temperature and positive dc bias at inner electrode) are optimized for cylindrical geometry. The etch rate non-uniformity has been overcome by simultaneous translation of the gas point-of-entry and the inner electrode during the processing. A single cell SRF cavity has been centrifugally barrel polished, chemically …

Design And Prototyping Of A 400 Mhz Rf-Dipole Crabbing Cavity For The Lhc High-Luminosity Upgrade, S. U. De Silva, J. R. Delayen, H. Park, Z. Li, T. H. Nicol

Physics Faculty Publications

LHC High Luminosity Upgrade is in need of two crabbing systems that deflects the beam in both horizontal and vertical planes. The 400 MHz rf-dipole crabbing cavity system is capable of crabbing the proton beam in both planes. At present we are focusing our efforts on a complete crabbing system in the horizontal plane. Prior to LHC installation the crabbing system will be installed for beam test at SPS. The crabbing system consists of two rf-dipole cavities in the cryomodule. This paper discusses the electromagnetic design and mechanical properties of the rf-dipole crabbing system for SPS beam test.

Imperfection And Tolerance Analysis Of Hom Couplers For Odu/Slac 400 Mhz Crabbing Cavity, S. U. De Silva, R. G. Olave, H. Park, J. R. Delayen, Z. Li

Physics Faculty Publications

In preparation for the LHC High Luminosity upgrade, a 400 MHz crab cavity has been developed jointly at ODU/SLAC, including two higher order mode couplers designed to dampen the wakefields in order to comply with the impedance budget specified for the LHC system. During fabrication, assembly, and processing of the couplers, a number of imperfections may arise that could modify the higher order mode spectrum and the associated impedance for each mode. We present here a detailed study of the imperfections of the horizontal- and vertical- HOM couplers, and the associated allowed tolerances for manufacture, assembly and processing.

Fpc And Hi-Pass Filter Hom Coupler Design For The Rf Dipole Crab Cavity For The Lhc Hilumi Upgrade, Zenghai Li, S. U. De Silva, J. R. Delayen, Hyekyoung Park, R. G. Olave

Physics Faculty Publications

A 400-MHz compact RF dipole (RFD) crab cavity design was jointly developed by Old Dominion University and SLAC under the support of US LARP program for the LHC HiLumi upgrade. The RFD cavity design is consisted of a rounded-square tank and two ridged deflecting poles, operating with a TE11-like dipole mode, which is the lowest mode of the cavity. A prototype RFD cavity is being manufactured and will be tested on the SPS beam line at CERN. The coaxial fundamental Power Coupler (FPC) of the prototype cavity was re-optimized to minimizing the power heating on the coupler internal antenna. A …

Progress On The Design Of The Polarized Medium Energy Electron Ion Collider At Jlab, F. Lin, S. A. Bogacz, P. D. Brindza, A Camsonne, E. Daly, Y. S. Derbenev, D. Douglas, R. Ent, D. Gaskell, R. L. Geng, A. Castilla, J. R. Delayen, C. E. Hyde, K. Park

Physics Faculty Publications

The Medium-energy Electron Ion Collider (MEIC) at JLab is designed to provide high luminosity and high polarization needed to reach new frontiers in the exploration of nuclear structure. The luminosity, exceeding 10³³ cm^-2s⁻¹ in a broad range of the center-of-mass (CM) energy and maximum luminosity above 10³⁴ cm^-2s⁻¹, is achieved by high-rate collisions of short small-emittance low-charge bunches made possible by high-energy electron cooling of the ion beam and synchrotron radiation damping of the electron beam. The polarization of light ion species (p, d, ³He) can be easily preserved and …