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in creator/contributor: "Lawrence Berkeley National Laboratory. Accelerator & Fusion Research Division."

Experimental Tests of Cooling: Expectations and Additional Needs

Cooling is a critical aspect for a high-performance Neutrino Factory or a MuonCollider. For this reason, considerable effort is being put toward theexperimental verification of this technique. The international Muon IonizationCooling Experiment, MICE, was approved to operate at Rutherford AppletonLaboratory (RAL) in the UK and beam line commissioning commenced in March, 2008. The MICE collaboration comprises about 130 scientists and engineers from Asia, Europe, and the U.S. In this paper we present the motivation and goals for thisexperiment and describe its present status. MICE is scheduled for completion in2011. We will also indicate the prospects for a future 6D muon coolingexperiment and discuss its possible time schedule.

Date: September 24, 2008

Creator: Zisman, Michael S

Item Type: Article

Partner: UNT Libraries Government Documents Department

SYNCHROTRON RADIATION AND RING FORMATION IN THE ELECTRON RING ACCELERATOR

We discuss the possibility of using synchrotron radiation to form electron rings having a very high electric field to hold the ions inside the ring. The formulas describing bow the energy and the dimension of the ring change under the effect of synchrotron radiation are derived, and a numerical example is given.

Date: May 13, 1970

Creator: Pellegrini, C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

Shot-Noise Seeded Microbunching Instability: Second-Order Correction to the Gain Function

We determine the second-order correction to the gain function of the microbunching instability in single-pass systems of interest for the next generation of light sources. The calculation applies to the case where the instability is seeded by shot noise. We examine an analytically treatable model of beam dynamics where collective forces are active only in non-dispersive sections of the linac. We find that the second order term can augment the linear gain significantly while affecting the spectrum of the overall gain only marginally. The weight of the second-order correction relative to the linear gain is found to scale quadratically with respect to R56. The qualitative behavior predicted by the model is consistent with exact numerical solutions of the Vlasov equations for realistic lattices.

Date: June 30, 2008

Creator: Venturini, Marco

Item Type: Article

Partner: UNT Libraries Government Documents Department

Control of Laser Plasma Based Accelerators up to 1 GeV

This dissertation documents the development of a broadband electron spectrometer (ESM) for GeV class Laser Wakefield Accelerators (LWFA), the production of high quality GeV electron beams (e-beams) for the first time in a LWFA by using a capillary discharge guide (CDG), and a statistical analysis of CDG-LWFAs. An ESM specialized for CDG-LWFAs with an unprecedented wide momentum acceptance, from 0.01 to 1.1 GeV in a single shot, has been developed. Simultaneous measurement of e-beam spectra and output laser properties as well as a large angular acceptance (> {+-} 10 mrad) were realized by employing a slitless scheme. A scintillating screen (LANEX Fast back, LANEX-FB)--camera system allowed faster than 1 Hz operation and evaluation of the spatial properties of e-beams. The design provided sufficient resolution for the whole range of the ESM (below 5% for beams with 2 mrad divergence). The calibration between light yield from LANEX-FB and total charge, and a study on the electron energy dependence (0.071 to 1.23 GeV) of LANEX-FB were performed at the Advanced light source (ALS), Lawrence Berkeley National Laboratory (LBNL). Using this calibration data, the developed ESM provided a charge measurement as well. The production of high quality electron beams up to 1 GeV from a centimeter-scale accelerator was demonstrated. The experiment used a 310 {micro}m diameter gas-filled capillary discharge waveguide that channeled relativistically-intense laser pulses (42 TW, 4.5 x 10{sup 18} W/cm{sup 2}) over 3.3 centimeters of sufficiently low density ({approx_equal} 4.3 x 10{sup 18}/cm{sup 3}) plasma. Also demonstrated was stable self-injection and acceleration at a beam energy of {approx_equal} 0.5 GeV by using a 225 {micro}m diameter capillary. Relativistically-intense laser pulses (12 TW, 1.3 x 10{sup 18}W/cm{sup 2}) were guided over 3.3 centimeters of low density ({approx_equal} 3.5 x 10{sup 18}/cm{sup 3}) plasma in this experiment. A statistical analysis of the CDG-LWFAs ...

Date: December 3, 2007

Creator: Nakamura, Kei

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

R&D Toward a Neutrino Factory and Muon Collider

There is considerable interest in the use of muon beams to create either an intense source of decay neutrinos aimed at a detector located 3000-7500 km away (a Neutrino Factory), or a Muon Collider that produces high-luminosity collisions at the energy frontier. R&D aimed at producing these facilities has been under way for more than 10 years. This paper will review experimental results from MuCool, MERIT, and MICE and indicate the extent to which they will provide proof-of-principle demonstrations of the key technologies required for a Neutrino Factory or Muon Collider. Progress in constructing components for the MICE experiment will also be described.

Date: April 29, 2009

Creator: Zisman, Michael S

Item Type: Article

Partner: UNT Libraries Government Documents Department

Particle-In-Cell/Monte Carlo Simulation of Ion Back BomBardment in a High Average Current RF Photo-Gun

In this paper, we report on study of ion back bombardment in a high average current radio-frequency (RF) photo-gun using a particle-in-cell/Monte Carlo simulation method. Using this method, we systematically studied effects of gas pressure, RF frequency, RF initial phase, electric field profile, magnetic field, laser repetition rate, different ion species on ion particle line density distribution, kinetic energy spectrum, and ion power line density distribution back bombardment onto the photocathode. Those simulation results suggested that effects of ion back bombardment could increase linearly with the background gas pressure and laser repetition rate. The RF frequency has significantly affected the ion motion inside the gun so that the ion power deposition on the photocathode in an RF gun can be several orders of magnitude lower than that in a DC gun. The ion back bombardment can be minimized by appropriately choosing the electric field profile and the initial phase.

Date: October 17, 2009

Creator: Qiang, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

Test Results of HD2, A High Field Nb3Sn Dipole with A 36 MM Bore

The Superconducting Magnet Program at Lawrence Berkeley National Laboratory (LBNL) has developed the 1 m long Nb{sub 3}Sn dipole magnet HD2. With tilted (flared) ends to avoid obstructing a 36 mm clear bore, HD2 represents a step towards the use of block-type coils in high-field accelerator magnets. The coil design has been optimized to minimize geometric harmonics and reduce the conductor peak field in the end region, resulting in an expected short sample dipole field of 15 T. The support structure is composed by an external aluminum shell pre-tensioned with pressurized bladders and interference keys, and by two stainless steel end plates compressing the coil ends through four aluminum axial rods. We report on magnet design, assembly, and test results, including training performance, quench locations, and strain gauge measurements.

Date: May 19, 2008

Creator: Ferracin, Paolo

Item Type: Article

Partner: UNT Libraries Government Documents Department

Shell-Based Support Structures for Nb3Sn Accelerator Quadrupole Magnets

Shell-based support structures are being fabricated and tested as part of the development of large-aperture Nb{sub 3}Sn superconducting quadrupoles for future upgrades of the LHC Interaction Regions. These structures utilize water pressurized bladders for room-temperature pre-load control, and rely on a pre-tensioned aluminum shell to deliver a substantial part of the coil pre-stress during cool-down. The coil final pre-load is therefore monotonically approached from below, without overstressing the strain-sensitive conductor. This method has been adopted by the US LARP collaboration to test subscale racetrack coils (SQ series), 1 m long cos-theta coils (TQS series), and 4 m long magnets (LRS and LQS series). We present recent progress in the development of shell-based support structures, with a description of the principles of operations and the future plans.

Date: May 19, 2008

Creator: Ferracin, Paolo

Item Type: Article

Partner: UNT Libraries Government Documents Department

Modelling of e-Cloud Induced Coherent Tuneshifts Using POSINST: Simulation of April 2007 Measurements at Cesr

The authors model the interaction between a beam and electron cloud (EC) as taking place in localized stations along the accelerator at s = s{sub i}, i = 0,1,2, ..., n{sub s}.

Date: May 1, 2009

Creator: Venturini, Marco

Item Type: Report

Partner: UNT Libraries Government Documents Department

Nb3Sn Quadrupoles Designs For The LHC Upgrades

In preparation for the LHC luminosity upgrades, high field and large aperture Nb{sub 3}Sn quadrupoles are being studied. This development has to incorporate all the relevant features for an accelerator magnet like alignment and cooling channels. The LARP HQ model is a high field and large bore quadrupole that will meet these requirements. The 2-layer coils are surrounded by a structure based on key and bladder technology with supporting iron yoke and aluminum shell. This structure is aimed at pre-stress control, alignment and field quality. We present here the magnetic and mechanical design of HQ, along with recent progress on the development of the first 1-meter model.

Date: May 19, 2008

Creator: Felice, Helene

Item Type: Article

Partner: UNT Libraries Government Documents Department

Advances in Nb3Sn Performance

Nb{sub 3}Sn wires with non-Cu critical current densities (J{sub c}) that surpass 3 kAmm{sup -2} at 12 T and 4.2 K are commercially available in piece lengths longer than 10 km. Accelerator-type magnets that utilize these conductors have achieved record magnetic fields. This article summarizes key developments in the last decade that have led to these significant improvements in the performance of Nb{sub 3}Sn wires.

Date: May 19, 2008

Creator: Godeke, Arno

Item Type: Article

Partner: UNT Libraries Government Documents Department

A high-order fast method for computing convolution integral with smooth kernel

In this paper we report on a high-order fast method to numerically calculate convolution integral with smooth non-periodic kernel. This method is based on the Newton-Cotes quadrature rule for the integral approximation and an FFT method for discrete summation. The method can have an arbitrarily high-order accuracy in principle depending on the number of points used in the integral approximation and a computational cost of O(Nlog(N)), where N is the number of grid points. For a three-point Simpson rule approximation, the method has an accuracy of O(h{sup 4}), where h is the size of the computational grid. Applications of the Simpson rule based algorithm to the calculation of a one-dimensional continuous Gauss transform and to the calculation of a two-dimensional electric field from a charged beam are also presented.

Date: September 28, 2009

Creator: Qiang, Ji

Item Type: Article

Partner: UNT Libraries Government Documents Department

Modulation compression for short wavelength harmonic generation

Laser modulator is used to seed free electron lasers. In this paper, we propose a scheme to compress the initial laser modulation in the longitudinal phase space by using two opposite sign bunch compressors and two opposite sign energy chirpers. This scheme could potentially reduce the initial modulation wavelength by a factor of C and increase the energy modulation amplitude by a factor of C, where C is the compression factor of the first bunch compressor. Such a compressed energy modulation can be directly used to generate short wavelength current modulation with a large bunching factor.

Date: January 11, 2010

Creator: Qiang, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

The Muon Collider

We describe the scientific motivation for a new type of accelerator, the muon collider. This accelerator would permit an energy-frontier scientific program and yet would fit on the site of an existing laboratory. Such a device is quite challenging, and requires a substantial R&D program. After describing the ingredients of the facility, the ongoing R&D activities of the Muon Accelerator Program are discussed. A possible U.S. scenario that could lead to a muon collider at Fermilab is briefly mentioned.

Date: May 17, 2010

Creator: Zisman, Michael S

Item Type: Article

Partner: UNT Libraries Government Documents Department

Short Wavelength Seeding through Compression for Fee Electron Lasers

In this paper, we propose a seeding scheme that compresses an initial laser modulation in the longitudinal phase space of an electron beam by using two opposite sign bunch compressors and two opposite sign energy chirpers. This scheme could potentially reduce the initial modulation wavelength by a factor of C and increase the energy modulation amplitude by a factor of C , where Cis the compression factor of the first bunch compressor. Using two lasers as energy chirpers, such a modulation compression scheme can generate kilo-Ampershort wavelength current modulation with significant bunching factor from an initial a few tens Amper current. This compression scheme can also be used togenerate a prebunched single atto-second short wavelength current modulation and prebunched two color, two atto-second modulations.

Date: March 29, 2010

Creator: Qiang, Ji

Item Type: Article

Partner: UNT Libraries Government Documents Department

Single Ion Implantation and Deterministic Doping

The presence of single atoms, e.g. dopant atoms, in sub-100 nm scale electronic devices can affect the device characteristics, such as the threshold voltage of transistors, or the sub-threshold currents. Fluctuations of the number of dopant atoms thus poses a complication for transistor scaling. In a complementary view, new opportunities emerge when novel functionality can be implemented in devices deterministically doped with single atoms. The grand price of the latter might be a large scale quantum computer, where quantum bits (qubits) are encoded e.g. in the spin states of electrons and nuclei of single dopant atoms in silicon, or in color centers in diamond. Both the possible detrimental effects of dopant fluctuations and single atom device ideas motivate the development of reliable single atom doping techniques which are the subject of this chapter. Single atom doping can be approached with top down and bottom up techniques. Top down refers to the placement of dopant atoms into a more or less structured matrix environment, like a transistor in silicon. Bottom up refers to approaches to introduce single dopant atoms during the growth of the host matrix e.g. by directed self-assembly and scanning probe assisted lithography. Bottom up approaches are discussed in Chapter XYZ. Since the late 1960's, ion implantation has been a widely used technique to introduce dopant atoms into silicon and other materials in order to modify their electronic properties. It works particularly well in silicon since the damage to the crystal lattice that is induced by ion implantation can be repaired by thermal annealing. In addition, the introduced dopant atoms can be incorporated with high efficiency into lattice position in the silicon host crystal which makes them electrically active. This is not the case for e.g. diamond, which makes ion implantation doping to engineer the electrical properties of diamond, ...

Date: June 11, 2010

Creator: Schenkel, Thomas

Item Type: Book

Partner: UNT Libraries Government Documents Department

Some Considerations Regarding Pulsed Correction of Chromatic Aberrations in Final Focusing Systems

Nearly all designs of accelerators for heavy ion fusion rely on a velocity (energy) ramp to compress the beam longitudinally from its length in the accelerator to the length required at the target. The size of the velocity ramp is constrained by the longitudinal emittance of the beam. For example, if the longitudinal emittance is 0.05 eV {center_dot} s and we wish to produce a pulse having a width of {+-}2.5 ns at the target, we must supply an energy tilt such that the energy spread at the target is at least {+-}0.05 eV {center_dot} s/2.5 ns = {+-}2 x 10{sup 7} eV. The minimal value of energy spread occurs when the beam has propagated to the point where there is no correlation between the time and energy variables of the beam particles. (In the simple approximation where the boundary of the longitudinal phase space containing the particles is an ellipse, the ellipse is erect at this point, i.e., not tilted with respect to the axes.) In any case, the energy spread can affect focusing. If, for example, the beam kinetic energy is of the order of 5 GeV, a tilt of {+-}2 x 10{sup 7} eV corresponds to a fractional energy spread of 0.004 and it may be possible to focus the beam to the required spot size without using an achromatic optical system. Nevertheless, an optical system that allows larger longitudinal emittance should lead to a less expensive accelerator since the tolerances on acceleration waveforms could be relaxed. Moreover, at lower kinetic energies the problem becomes more serious. If the kinetic energy of our example beam were 1 GeV rather than 5 GeV, the fractional energy spread would be 0.02. This much energy spread would likely produce serious chromatic aberrations leading to an unwanted increase in focal spot ...

Date: March 31, 2010

Creator: Bangerter, Roger

Item Type: Report

Partner: UNT Libraries Government Documents Department

The evolution of ion charge states in cathodic vacuum arc plasmas: a review

Cathodic vacuum arc plasmas are known to contain multiply charged ions. 20 years after “Pressure Ionization: its role in metal vapour vacuum arc plasmas and ion sources” appeared in vol. 1 of Plasma Sources Science and Technology, it is a great opportunity to re-visit the issue of pressure ionization, a non-ideal plasma effect, and put it in perspective to the many other factors that influence observable charge state distributions, such as the role of the cathode material, the path in the density-temperature phase diagram, the “noise” in vacuum arc plasma as described by a fractal model approach, the effects of external magnetic fields and charge exchange collisions with neutrals. A much more complex image of the vacuum arc plasma emerges putting decades of experimentation and modeling in perspective.

Date: December 18, 2011

Creator: Anders, Andre

Item Type: Article

Partner: UNT Libraries Government Documents Department

Longitudinal Motion in High Current Ion Beams - a Self-Consistent Phase Space Distribution With an Envelope Equation

Many applications of particle acceleration, such as heavy ion fusion, require longitudinal bunching of a high intensity particle beam to extremely high particle currents with correspondingly high space charge forces. This requires a precise analysis of longitudinal motion including stability analysis. Previous papers have treated the longitudinal space charge force as strictly linear, and have not been self-consistent; that is, they have not displayed a phase space distribution consistent with this linear force so that the transport of the phase space distribution could be followed, and departures from linearity could be analyzed. This is unlike the situation for transverse phase space where the Kapchinskij-Vladimirskij (K-V) distribution can be used as the basis of an analysis of transverse motion. In this paper we derive a self-consistent particle distribution in longitudinal phase space which is a solution of the Vlasov equation and derive an envelope equation for this solution. The solution is developed in Section II from a stationary solution of the Vlasov equation derived in Section I.

Date: March 1, 1979

Creator: Neuffer, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

Final Report for completed IPP Project:"Development of Plasma Ablation for Soft Tissue and Bone Surgery"

ArthroCare is a medical device company that develops, manufactures, and markets an advanced surgical tool, a plasma electro-surgical system for cutting and removing tissue. The hand-held electrical discharge device produces plasma in a biocompatible conductive fluid and tissue to which it is applied during surgery. Its products allow surgeons to operate with increased precision and accuracy, limiting damage to surrounding tissue thereby reducing pain and speeding recovery for the patient. In the past, the design of ArthfoCare's plasma wands has been an empirical undertaking. One goal of this R&D program was to put the phenomena involved on a sound scientific footing, allowing optimization of existing plasma based electro-surgery system technology, and the design and manufacture of new and improved kinds of scalpels, in particular for the surgical cutting of bone. Another important related goal of the program was to develop, through an experimental approach, new plasma wand approaches to the cutting ('shaving') of hard bone tissue. The goals of the CRADA were accomplished - computer models were used to predict important parameters of the plasma discharge and the bone environment, and several different approaches to bone-shaving were developed and demonstrated. The primary goal of the project was to develop and demonstrate an atmospheric-pressure plasma tool that is suitable for surgical use for shaving bone in humans. This goal was accomplished, in fact with several different alternative plasma approaches. High bone ablation speeds were measured. The use of probes ('plasma wand' - the surgical tool) with moving active electrodes was also explored, and there are advantages to this method. Another important feature is that the newly-exposed bone surface have only a very thin necrosis layer; this feature was demonstrated. This CRADA has greatly advanced our understanding of bone removal by atmospheric pressure plasmas in liquid, and puts ArthroCare in a good ...

Date: September 1, 2009

Creator: Brown, Ian

Item Type: Report

Partner: UNT Libraries Government Documents Department

INSTABILITIES OF RELATIVISTIC PARTICLE BEAMS

The purpose of this paper is twofold: to introduce the reader to the subject of instabilities exhibited by relativistic particle beams, and to summarize the present state of our knowledge concerning these phenomena. Most of the material in the first part of the paper is not new. It has been known to some specialists for a good many years; what is new is that the problems that can be solved are now of much more interest to the general community of accelerator physicists. Consequently, many accelerator physicists who have not paid much attention to these matters may now want to become informed; it is my hope that this paper will provide an introduction to the field. The second part of the article consists of two sections. The first summarizes the experimental information presently available, with emphasis upon the degree to which it confirms or disagrees with theory. Our current level of understanding is delineated: considering the generality and reliability of the theoretical analysis as well as the degree of experimental confirmation, the author expresses his opinion as to what can be considered relatively well established. The final section contains a discussion of subjects needing further investigation and, consequently, supplements the discussion of areas of understanding by describing the peripheral areas of uncertainty.

Date: October 4, 1965

Creator: Sessler, Andrew M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

International scoping study: accelerator working group report

During the past several years, an International Scoping Study (ISS) of a Neutrino Factory was carried out, with the aim of developing an internationally accepted baseline facility design. Progress toward that goal will be described. Many of the key technical aspects of a Neutrino Factory facility design are presently being investigated experimentally, and the status of these investigations will be mentioned. Plans for the recently launched International Design Study (IDS), which serves as a follow-on to the ISS, will be briefly described.

Date: September 30, 2006

Creator: Zisman, Michael & Zisman, M.S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

Investigation of Beam Instability Under the Effects of Long-Range Transverse Wake Fields in the Berkeley Future Light Source

An ultra-relativistic charged particle bunch moving through a resonator cavity leaves behind a wake field that will affect subsequent bunches (if the bunch is not ultra-relativistic, the wake field will not be exclusively behind it). If the initial bunch enters the cavity off-axis, it will produce a transverse wake field that can then kick later bunches off the axis. Thus, even bunches that were initially traveling on axis could be displaced and, in turn, produce their own transverse wake fields, affecting following bunches. The offsets obtained by bunches could increase along the bunch train, leading to the so-called multi-bunch beam break-up instability [1]. The purpose of our investigation is to see whether such instability will occur in the superconducting, 1.3 GHz, 2.5GeV linac (see Table 1) planned for the Berkeley future light source (BFLS). We assume an initial steady-state situation established for machine operation; i.e. a continuous process where every bunch follows the same trajectory through the linac, with only small deviations from the axis of the rf structures. We will look at a possible instability arising from a bunch having a small deviation from the established trajectory. Such a deviation would produce a wake field that is slightly different from the one produced by the bunches following the established trajectory. This could lead to subsequent bunches deviating further from the established trajectory. We will assume the deviations are small (at first) and so the difference in the wake field caused by a bunch not traveling along the established trajectory is well approximated by a long-range transverse dipole wake. We are concerned only with deviations from the established trajectory; thus, in our models, a transverse position of zero corresponds to the bunch traveling along the established trajectory. Under this assumption, only the additional long-range transverse dipole wake remains in our ...

Date: August 31, 2008

Creator: Kur, Eugene & Zholents, Alexander A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

LASER ACCELERATORS

Laser accelerators may be conveniently characterized, by their mode of operation, into media, far-field, and near-field accelerators. The first category--media accelerators--include the Inverse Cherenkov Effect Accelerator, the Plasma Focus Accelerator, and the Beat Wave Accelerator (BWA). The second category--far-field accelerators--include the Two-Wave Device and the Inverse Free Electron Accelerator (IFEL). The third category--near-field accelerators--includes conventional linacs scaled to small dimensions, dielectric sheets, small holes in dielectric cylinders, and gratings. Attention is devoted to an example from each category: namely (1) the BWA, (2) the IFEL, and (3) the linac scaled to small dimensions (about 30 GHz) and powered by a free electron laser (FEL). Finally, special attention is given to grating accelerators.

Date: April 1, 1983

Creator: Sessler, A.M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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