Plasma and Beam Physics Commons^™

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.

Beam Dynamics Studies Of 499 Mhz Superconducting Rf-Dipole Deflecting Cavity System, S. U. De Silva, K. E. Deitrick, H. Park, J. R. Delayen

Physics Faculty Publications

A 499 MHz deflecting cavity has been designed as a three-way beam spreader to separate an electron beam into 3 beams. The rf tests carried out on the superconducting rf-dipole cavity have demonstrated that a transverse voltage of 4.2 MV can be achieved with a single cavity. This paper discusses the beam dynamics on a deflecting structure operating in continuous-wave mode with a relativistic beam. The study includes the analysis on emittance growth, energy spread, and change in bunch size including effects due to field non-uniformities.

Progress On A Compact Accelerator Design For A Compton Light Source, K. Deitrick, J. R. Delayen, B.R.P. Gamage, Geoffrey A. Krafft, T. Satogata

Physics Faculty Publications

A compact Compton light source using an electron linear accelerator is in design at the Center for Accelerator Science at Old Dominion University and Jefferson Lab. We report on the current design, including beam properties through the entire system based on a full end-to-end simulation, compare current specifications to design goals, and target areas for improvement.

Peppo: Using A Polarized Electron Beam To Produce Polarized Positrons, A. Adeyemi, G.L Gueye, P.A. Adderly, M. L. Stutzman, M. M. Ali, H. Areti, J. F. Benesch, L. S. Cardman, J. Clark, S. Covert, S. Golge, C. Hyde

Physics Faculty Publications

An experiment demonstrating a new method for producing polarized positrons has been performed at the CEBAF accelerator at Jefferson Laboratory. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁺/e⁻ pairs originating from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a 1.0 mm tungsten pair-production target. This paper describes preliminary results of measurements using an 8.2 MeV/c electron beam with polarization 84% to generate positrons in the range of 3.1 to 6.2 MeV/c with polarization as high as ∼80%.

Effects Of Crab Cavities Multipole Content In An Electron-Ion Collider, A. Castilla, V. S. Morozov, T. Satogata, J. R. Delayen

Physics Faculty Publications

The impact on the beam dynamics of the Medium Energy Electron-Ion Colider (MEIC) due to the multipole content of the 750 MHz crab cavity was studied using thin multipole elements for 6D phase space particle tracking in ELEGANT. Target values of the sextupole component for the cavity’s field expansion were used to perform preliminary studies on the proton beam stability when compared to the case of pure dipole content of the rf kicks. Finally, important effects on the beam sizes due to non-linear components of the crab cavities’ fields were identified and some criteria for their future study were proposed.

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.

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 …

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 …

Evaluation Of The Effects Of A Plasma Activated Medium On Cancer Cells, S. Mohades, M. Laroussi, J. Sears, N. Barekzi, H. Razavi

Electrical & Computer Engineering Faculty Publications

The interaction of low temperature plasma with liquids is a relevant topic of study to the field of plasma medicine. This is because cells and tissues are normally surrounded or covered by biological fluids. Therefore, the chemistry induced by the plasma in the aqueous state becomes crucial and usually dictates the biological outcomes. This process became even more important after the discovery that plasma activated media can be useful in killing various cancer cell lines. Here, we report on the measurements of concentrations of hydrogen peroxide, a species known to have strong biological effects, produced by application of plasma to …

Langmuir Probe Instrument Suite For Mesosphere Turbulence Experiment Mission, Adam Blake

Doctoral Dissertations and Master's Theses

The Langmuir probe technique is the predominant in-situ plasma diagnostic technique, and is arguably the only measurement technique that is universally own on every sounding rocket investigation. Earth's mesosphere region (80-120 km) is a host of many dynamic phenomena such as the noctilucent clouds, breaking gravity waves, inversion layers, settlement of mesospheric smoke particles, etc. As such it is critical to have a comprehensive suite of plasma diagnostics that can unambiguously measure various plasma parameters.

This thesis deals with the development and testing of three different Langmuir probe implementations suitable for investigation of the mesosphere which are to be launched …

A Prototype Microwave Cavity Control Circuit For Use In Next Generation Free Electron Laser, Josh Thompson, Peter Neal Barrina, Jiayi Jiang, Joe Frisch, Steve Smith, Daniel Van Winkle

STAR Program Research Presentations

One of the current programs at SLAC National Accelerator Laboratory is the Linac Coherent Light Source, or LCLS. Using the existing hardware of the last third of their linear accelerator (or “linac”), SLAC has created one of the most energetic X-ray free electron lasers (or “FEL”). Since 2009, LCLS has used this FEL to perform a wide range of experiments across all sciences, most notably ultrafast filming at the molecular scale. As requests for beam-time with this laser increases, SLAC is purposing a linac upgrade to better match this demand. This upgrade, named LCLS-II, will replace existing copper radio frequency …

A Numerical Assessment Of Cosmic-Ray Energy Diffusion Through Turbulent Media, M. Fatuzzo, F. Melia

Faculty Scholarship

No abstract provided.

Effects Of Turbulence On Cosmic Ray Propagation In Protostars And Young Stars, M. Fatuzzo, F. C. Adams

Faculty Scholarship

No abstract provided.

Higher Order Mode Damping In Superconducting Spoke Cavities, C. S. Hopper, J. R. Delayen

Physics Faculty Publications

Parasitic higher order modes (HOMs) can be severely detrimental to the performance of superconducting cavities. For this reason, the mode spectrum and beam coupling strength must be examined in detail to determine which modes must be damped. One advantage of the spoke cavity geometry is that couplers can be placed on the outer body of the cavity rather than in the beam line space. We present an overview of the HOM properties of spoke cavities and methods for suppressing the most harmful ones.

Employing Twin Crabbing Cavities To Address Variable Transverse Coupling Of Beams In The Meic, A. Castilla, V. S. Morozov, T. Satogata, J. R. Delayen

Physics Faculty Publications

The design strategy of the Medium Energy Electron-Ion Collider (MEIC) at Jefferson Lab contemplates both matching of the emittance aspect ratios and a 50 mrad crossing angle along with crab crossing scheme for both electron and ion beams over the energy range (√s=20-70 GeV) to achieve high luminosities at the interaction points (IPs). However, the desired locations for placing the crabbing cavities may include regions where the transverse degrees of freedom of the beams are coupled with variable coupling strength that depends on the collider rings’ magnetic elements (solenoids and skew quadrupoles). In this work we explore the feasibility of …

Progress On The Interaction Region Design And Detector Integration At Jlab's Meic, V. S. Morozov, P. Brindza, A. Camsonne, Ya S. Derbenev, R. Ent, D. Gaskell, F. Lin, P. Nadel-Turonski, M. Ungaro, Y. Zhang, C. E. Hyde, K. Park, M. Sullivan, Z. W. Zhao

Physics Faculty Publications

One of the unique features of JLab's Medium-energy Electron-Ion Collider (MEIC) is a full-acceptance detector with a dedicated, small-angle, high-resolution detection system, capable of covering a wide range of momenta (and charge-to-mass ratios) with respect to the original ion beam to enable access to new physics. We present an interaction region design developed with close integration of the detection and beam dynamical aspects. The dynamical aspect of the design rests on a symmetry-based concept for compensation of non-linear effects. The optics and geometry have been optimized to accommodate the detection requirements and to ensure the interaction region's modularity for ease …

Plasma Processes And Polymers Special Issue On: Plasma And Cancer, Mounir Laroussi, Michael Keidar

Electrical & Computer Engineering Faculty Publications

During the last two decades, research efforts on the application of low temperature plasmas in biology and medicine have positioned nonequilibrium lowtemperature plasmas as a technology that has the potential of revolutionizing healthcare.[1,2] Low temperature plasmas can be applied in direct contact with living tissues to inactivate bacteria,[3] to disinfect wounds and accelerate wound healing,[4] and to induce damage in some cancer cells.[5–11]

Fully Coupled Fluid And Electrodynamic Modeling Of Plasmas: A Two-Fluid Isomorphism And A Strong Conservative Flux-Coupled Finite Volume Framework, Richard Joel Thompson

Doctoral Dissertations

Ideal and resistive magnetohydrodynamics (MHD) have long served as the incumbent framework for modeling plasmas of engineering interest. However, new applications, such as hypersonic flight and propulsion, plasma propulsion, plasma instability in engineering devices, charge separation effects and electromagnetic wave interaction effects may demand a higher-fidelity physical model. For these cases, the two-fluid plasma model or its limiting case of a single bulk fluid, which results in a single-fluid coupled system of the Navier-Stokes and Maxwell equations, is necessary and permits a deeper physical study than the MHD framework. At present, major challenges are imposed on solving these physical models …

Feedback Stabilization At Spear3, Daniel Kelley, Jeff Corbett

STAR Program Research Presentations

The SPEAR3 synchrotron lightsource at SLAC relies on a sophisticated radio frequency (RF) timing system to maintain current – electrons – in the storage ring. One problem SPEAR3 operators have dealt with is the thermal expansion of one of the cables supporting this RF timing system. As the cable expands and contracts with the diurnal rise and fall of the sun, the phase of the RF in the cable shifts. This shifting phase affects the timing accuracy of electron injections into the storage ring.

A common feedback control algorithm PID (Proportional Integral Derivative) has countless applications in engineering. PID feedback …

Study Of A Non-Equilibrium Plasma Pinch With Application For Microwave Generation, Ahmad Al Agry

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Non-Equilibrium Plasma Pinch (NEPP), also known as the Dense Plasma Focus (DPF) is well known as a source of energetic ions, relativistic electrons and neutrons as well as electromagnetic radiation extending from the infrared to X-ray. In this dissertation, the operation of a 15 kJ, Mather type, NEPP machine is studied in detail. A large number of experiments are carried out to tune the machine parameters for best performance using helium and hydrogen as filling gases. The NEPP machine is modified to be able to extract the copious number of electrons generated at the pinch. A hollow anode with …

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

Physics Faculty Publications

The proposed LHC high luminosity upgrade requires two crabbing systems in increasing the peak luminosity, operating both vertically and horizontally at two interaction points of IP1 and IP5. The required system has tight dimensional constraints and needs to achieve higher operational gradients. A proof-of-principle 400 MHz crabbing cavity design has been successfully tested and has proven to be an ideal candidate for the crabbing system. The cylindrical proof-of-principle rf-dipole design has been adapted in to a square shaped design to further meet the dimensional requirements. The new rf-dipole design has been optimized in meeting the requirements in rf-properties, higher order …

Multipole Field Effects For The Superconducting Parallel-Bar/Rf-Dipole Deflecting/Crabbing Cavities, S. U. De Silva, J. R. Delayen

Physics Faculty Publications

The superconducting parallel-bar deflecting/crabbing cavity is currently being considered as one of the design options in rf separation for the Jefferson Lab 12 GeV upgrade and for the crabbing cavity for the proposed LHC luminosity upgrade. Knowledge of multipole field effects is important for accurate beam dynamics study of rf structures. The multipole components can be accurately determined numerically using the electromagnetic surface field data in the rf structure. This paper discusses the detailed analysis of those components for the fundamental deflecting/crabbing mode and higher order modes in the parallel-bar deflecting/crabbing cavity.

Geometry Effects On Multipole Components And Beam Optics In High-Velocity Multi-Spoke Cavities, C. S. Hopper, K. Deitrick, J. R. Delayen

Physics Faculty Publications

Velocity-of-light, multi-spoke cavities are being proposed to accelerate electrons in a compact light-source [1]. There are strict requirements on the beam quality which require that the linac have only small non-uniformities in the accelerating field. Beam dynamics simulations have uncovered varying levels of focusing and defocusing in the proposed cavities, which is dependent on the geometry of the spoke in the vicinity of the beam path. Here we present results for the influence different spoke geometries have on the multipole components of the accelerating field and how these components, in turn, impact the simulated beam properties.

Study Of Cavity Imperfection Impact On Rf-Parameters And Multipole Components In A Superconducting Rf-Dipole Cavity, R. G. Olave, J. R. Delayen, S. U. De Silva, Z. Li

Physics Faculty Publications

The ODU/SLAC superconducting rf-dipole cavity is under consideration for the crab-crossing system in the upcoming LHC luminosity upgrade. While the proposed cavity complies well within the rf-parameters and multipolar component restrictions for the LHC system, cavity imperfections arising from cavity fabrication, welding and frequency tuning may have a significant effect in these parameters. We report on an initial study of the impact of deviation from the ideal shape on the cavity’s performance in terms of rf-parameters and multipolar components.

Comparison Of Electromagnetic, Thermal And Mechanical Calculations With Rf Test Results In Rf Dipole Deflecting/Crabbing Cavities, H. Park, S. U. Silva, J. R. Delayen

Physics Faculty Publications

The current requirements of higher gradients and strict dimensional constraints in the emerging applications have required the designing of compact deflecting and crabbing rf structures. The superconducting rf-dipole cavity is one of the first novel compact designs with attractive properties such as higher gradients, higher shunt impedance and widely separated higher order modes. The recent tests performed on proof-of-principle designs of the rf-dipole geometry at 4.2 K and 2.0 K in a vertical test assembly have proven the designs to achieve higher gradients with higher intrinsic quality factors and easily processed multipacting conditions. The design frequency sensitivity to pressure (df/dp) …

Magnetic Bunch Compression For A Compact Compton Source, B.R.P. Gamage, T. Satogata

Physics Faculty Publications

A compact electron accelerator suitable for Compton source applications is in design at the Center for Accelerator Science at Old Dominion University and Jefferson Lab. Here we discuss two options for transverse magnetic bunch compression and final focus, each involving a 4-dipole chicane with M56 tunable over a range of 1.5-2.0m with independent tuning of final focus to interaction point \beta*=5mm. One design has no net bending, while the other has net bending of 90 degrees and is suitable for compact corner placement.

Assessing The Feasibility Of Cosmic-Ray Acceleration By Magnetic Turbulence At The Magnetic Center, M. Fatuzzo, F. Melia

Faculty Scholarship

No abstract provided.