Beam Guides Research Articles

Vacuum Beam Guide for Large Scale Quantum Networks.

The vacuum beam guide (VBG) presents a completely different solution for quantum channels to overcome the limitations of existing fiber and satellite technologies for long-distance quantum communication. With an array of aligned lenses spaced kilometers apart, the VBG offers ultrahigh transparency over a wide range of optical wavelengths. With realistic parameters, the VBG can outperform the best fiber by 3 orders of magnitude in terms of attenuation rate. Consequently, the VBG can enable long-range quantum communication over thousands of kilometers with quantum channel capacity beyond 10^{13} qubit/sec, orders of magnitude higher than the state-of-the-art quantum satellite communication rate. Remarkably, without relying on quantum repeaters, the VBG can provide a ground-based, low-loss, high-bandwidth quantum channel that enables novel distributed quantum information applications for computing, communication, and sensing.

Guiding of Charged Particle Beams in Curved Plasma-Discharge Capillaries

Guiding of Charged Particle Beams in Curved Plasma-Discharge Capillaries

Handling the Functional Features of Accelerator Components Using ISO GPS Situation Features

The building blocks of a scientific facility based on particle beams comprise magnets and electro-magnetic devices. The optical design usually imposes a demanding accuracy with respect to their theoretically exact position and orientation. It happens that the functional features are either not clearly defined – what is the « axis » of a magnet –, or not explicitly used along their lifecycle. Improving how to handle these functional features would contribute to meeting demanding challenges. The European Spallation Source (ESS) is aiming at providing a powerful proton linear accelerator and a target system to produce pulsed neutrons. The challenging complex design and integration yielded to introducing a tool shared in common by all stakeholders along the lifecycle: the “situation features”, as defined in ISO GPS (Geometrical Product Specifications) standards. They are here developed, and extended to beyond-mechanics use cases. Two examples of fiducialization and installation phases are presented for neutron beam guides and quadrupole magnets. Perspectives of generic use are also highlighted.

Analyis of Fibre Laser’s Optical Construction from the End of the Beam Guiding Optical Fibre to the Focal Spot

Abstract In material-processing fiber lasers, the resonator in the closed box produces the laser radiation. Even with the same resonator, the diameter of the laser beam transporting fiber optics and the properties of the optical elements in the laser focusing head decide the cross-section of the focused laser beam used for machining. If we summarize the formulas in different sources in the literature, we can predict the effect of each optical element: what will happen if we choose another focusing lens, put a beam expander in the system, set on the beam expander how many times the laser beam expands. The other important point is that if we want to repeat an experiment or start a production process based on a scientific publication, then in addition to the resonator, it would be good to know the data of the optical elements in the focusing head, which is usually incomplete in the presented articles, but we can determine them approximately using the four formulas listed in the article.

Guiding and polarization shaping of vector beams in anisotropic media

We investigate a scheme to guide a weak vector beam using optically written waveguides inside atomic vapor, while controlling its polarization rotation. The atoms are prepared in the four-level tripod configuration in the presence of an external magnetic field. The three transitions of the tripod system are driven by a strong control beam and the two orthogonal polarization components of a weak vector beam (VB). A suitable spatial intensity profile and the detuning of the control field facilitate the generation of an optical fiberlike refractive index gradient across the atomic vapor. This enables waveguiding of the weak VB for a couple of Rayleigh lengths. Further, the magnetic-field-induced anisotropy of the tripod system creates a difference in the refractive indices of its two components. This is the reason behind the polarization shaping of VB. The mechanism of efficient guiding of VB with controllable polarization may have important applications in high-density optical communication and quantum information.

FT-ICR mass spectrometry: Superconducting magnet, external ion source, ion-molecule reactions, and ion-ion traps.

The world of Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry has witnessed, especially in the last 30 years significant advances in many fields of science, such as electronics, magnets, new ICR cell designs, developed ICR event sequences, modern external ionization sources, and linear ion beam guides, as well as modern vacuum technology. In this review, a brief account is given focusing especially on the studies performed in Wanczek's group and ICR research laboratory at the University of Bremen. An FT-ICR mass spectrometer has been developed with a high magnetic field superconducting magnet, operating at 4.7 T. At this magnetic field, a trapping time of 13.5 h was obtained with 30% efficiency. For the tetrachloromethane molecular ion, m/z 166, a mass-resolving power m/Δm = 1.5 × 106 was measured at a pressure of 2 × 10-8 Torr. The transition from magnet sweep to frequency sweep and the application of Fourier-transform has greatly enhanced the ICR technology. External ion sources were invented and differential pumping schemes were developed for enabling ultrahigh vacuum condition for ICR detection, while guiding ions at relatively higher pressures, during their flight to the ICR cell. With the external ion source, a time-of-flight ICR tandem instrument is built. A method to measure the ion flight time and to trap the ions in the ICR cell is described. Many ICR cell characteristics such as z-axis ion ejection and coupling of radial and axial ion motions in a superposed homogeneous magnetic and inhomogeneous trapping electric field were extensively studied. Gas-phase ion-molecule reactions of several reactive inorganic compounds with a focus on phosphorous and sulfur as well as silicon chemistry were also studied in great detail. The gas-phase ion chemistry of several trifluoromethyl-reagents such as trifluoromethyltrimethylsilane and tris(trifluoromethyl)phosphine were also investigated in ICR. Dual polarities multisegmented ICR cells were invented and deeply characterized. Sophisticated ICR pulse event programs were developed to enable long-range ion-ion interactions between simultaneously trapped positive and negative ions.

Design of phoxonic virtual waveguides for both electromagnetic and elastic waves based on the self-collimation effect: an application to enhance acousto-optic interaction.

The dual beam guides for transverse-electric and transverse-magnetic polarizations of electromagnetic (EM) wave and elastic wave in defect-free phoxonic crystals are reported. The realization for phoxonic virtual waveguides relies on dual flat equifrequency contours (EFCs) enabling self-collimation for EM and elastic waves. As a possible application of our work, the enhanced acousto-optic (AO) interaction in this kind of defect-free phoxonic waveguide, just as it does in defect-based waveguides, is further studied. Results show that obvious shifts of the transmission peaks of EM waves exist for both polarizations during one period of the elastic wave, and single-phonon exchange dominates the AO interaction. This kind of phoxonic virtual waveguide provides an effective platform to enhance AO interaction and exhibits some advantage over defect-based waveguides by properly manipulating the photonic and phononic dispersion surfaces.

Simultaneous beam guides of electromagnetic and acoustic waves in defect-free phoxonic crystals using self-collimation effect

We report the coexistence of photonic and phononic beam guides in defect-free phoxonic crystals that simultaneously allow a virtually diffractionless propagation for electromagnetic (EM) and acoustic waves. Functionality is achieved via self-collimation effects by intentionally creating simultaneous flat equal-frequency contours of EM waves for both polarizations and acoustic waves. Phoxonic self-collimation in a passband shows considerable advantages over the defect-based phoxonic bandgap effect in achieving phoxonic beam guides. The results thus provide a potential platform to achieve various acoustic-optic devices and highly controllable photon-phonon interactions by simultaneously manipulating the photonic and phononic dispersion.

A new XRF spectrometer using a crystal monochromator and parallel plates beam guides

Conventional x-ray fluorescence analysis (XRF) is a powerful instrumental technique for elemental quantification of samples with a wide range of matrices coming from industry, medicine, biology, environmental and archaeometry. The scattering of the x-ray tube excitation beam from the matrix is mainly responsible of the strong background in XRF spectra which restricts the detection limit (DL) to a few ppm (w/w). One possible strategy to reduce the DL is the monochromatization of the excitation beam with a crystal monochromator. In this case, the optimization of the system components is strongly required to obtain the highest excitation count rate over the sample, since it is considerable reduced by the short energy band pass of the monochromator.In the present work an optical device composed by a Si(100) crystal monochromator and two parallel plates beam guides (PPBG) was characterized and including in a conventional XRF spectrometer to improve the DLs. The PPBGs are composed by several thin glass plate reflectors placed together and separated by spacers. Inside the gap, x-rays are transmitted by total reflection contributing to the photon flux at the output of the optical device. The first PPBG reduces the divergence of the beam striking the crystal, and the second one collects the monochromatic beam that emerges from the crystal. In this way, the design of the optical device is quite compact keeping a high photon flux at the output thanks to the wide acceptance solid angle of the PPBGs. The new XRF spectrometer was applied to the analysis of biological tissues. The first results obtained in this field are shown in the present work where the performance of the spectrometer can be evaluated.

Guiding of relativistic electron beams in dense matter by laser-driven magnetostatic fields

Intense lasers interacting with dense targets accelerate relativistic electron beams, which transport part of the laser energy into the target depth. However, the overall laser-to-target energy coupling efficiency is impaired by the large divergence of the electron beam, intrinsic to the laser–plasma interaction. Here we demonstrate that an efficient guiding of MeV electrons with about 30 MA current in solid matter is obtained by imposing a laser-driven longitudinal magnetostatic field of 600 T. In the magnetized conditions the transported energy density and the peak background electron temperature at the 60-μm-thick target's rear surface rise by about a factor of five, as unfolded from benchmarked simulations. Such an improvement of energy-density flux through dense matter paves the ground for advances in laser-driven intense sources of energetic particles and radiation, driving matter to extreme temperatures, reaching states relevant for planetary or stellar science as yet inaccessible at the laboratory scale and achieving high-gain laser-driven thermonuclear fusion.

Guiding of charged particle beams in curved capillary-discharge waveguides

A new method able to transport charged particle beams along a curved path is presented. It is based on curved capillary-discharge waveguides where the induced azimuthal magnetic field is used to focus the beam and, at the same time, keep it close to the capillary axis. We show that such a solution is highly tunable, it allows to develop compact structures providing large deflecting angles and, unlike conventional solutions based on bending magnets, preserves the beam longitudinal phase space. Such a feature, in particular, is very promising when dealing with ultra-short bunches for which non-trivial manipulations on the longitudinal phase spaces are usually required when employing conventional deflecting devices.

Monte Carlo ray-tracing simulations for cold neutron beam guides of CONAS

The cold neutron guides dedicated to the cold neutron activation station (CONAS) at HANARO (KAERI, Republic of Korea) offering a substantial improvement of analytical sensitivity were simulated by using two Monte Carlo neutron ray-tracing packages (McStas and VITESS). In this paper, the estimations of neutron intensities and fluxes were calculated at some particular positions of the two cold neutron guides, namely CG1 and CG2B. In addition, some drawbacks of the simulation with the energy spread of the incident beams were found out based on the comparison between the simulation and experimental results.

Guiding and focusing of fast electron beams produced by ultra-intense laser pulse using a double cone funnel target

A novel double cone funnel target design aiming at efficiently guiding and focusing fast electron beams produced in high intensity (>1019 W/cm2) laser-solid interactions is investigated via two-dimensional particle-in-cell simulations. The forward-going fast electron beams are shown to be directed and focused to a smaller size in comparison with the incident laser spot size. This plasma funnel attached on the cone target guides and focuses electrons in a manner akin to the control of liquid by a plastic funnel. Such device has the potential to add substantial design flexibility and prevent inefficiencies for important applications such as fast ignition. Two reasons account for the collimation of fast electron beams. First, the sheath electric fields and quasistatic magnetic fields inside the vacuum gap of the double cone provide confinement of the fast electrons in the laser-plasma interaction region. Second, the interface magnetic fields inside the beam collimator further guide and focus the fast electrons during the transport. The application of this technique to cone-guided fast ignition is considered, and it is shown that it can enhance the laser energy deposition in the compressed fuel plasma by a factor of 2 in comparison with the single cone target case.

Guiding and collimation of laser-accelerated proton beams using thin foils followed with a hollow plasma channel

It is proposed that guided and collimated proton acceleration by intense lasers can be achieved using an advanced target—a thin foil followed by a hollow plasma channel. For the advanced target, the laser-accelerated hot electrons can be confined in the hollow channel at the foil rear side, which leads to the formation of transversely localized, Gaussian-distributed sheath electric field and resultantly guiding of proton acceleration. Further, due to the hot electron flow along the channel wall, a strong focusing transverse electric field is induced, taking the place of the original defocusing one driven by hot electron pressure in the case of a purely thin foil target, which results in collimation of proton beams. Two-dimensional particle-in-cell simulations show that collimated proton beams with energy about 20 MeV and nearly half-reduced divergence of 26° are produced at laser intensities 1020 W/cm2 by using the advanced target.

Radio frequency quadrupole technology: Evolution and contributions to mass spectrometry

Just as 2013 marks the centenary of the birth of mass spectrometry through the publication of Thomson’s classic book ‘Rays of Positive Electricity and Their Application to Chemical Analyses’, it is also exactly six decades since Paul and Steinwedel filed their first German patent ‘Verfahren zur Trennung bzw. Zum getrennten Nachweis von Ionen verschiedener spezifischer Ladung’ (‘Method for separating or separately detecting ions of different specific charges’) on 24th December, 1953. This patent described the quadrupole mass filter (QMF) and the three-dimensional quadrupole ion trap (3D-QIT), both of which operate by confining ions mass-selectively through the application of radio frequency quadrupolar potentials to appropriate electrode structures. In the ensuing 60 years since the initial description of these devices the impact of quadrupole technology upon mass spectrometry as a whole has been truly remarkable, especially when combined with chromatographic separation methods and/or other types of mass analysers. This retrospective article will aim to trace the principal milestones in the evolution of transmission quadrupoles (the QMF, quadrupole beam guides, and triple quadrupole tandem instruments) and of trapping quadrupoles (the 3D-QIT and, the more recent, linear quadrupole ion trap (LQIT)), both as stand-alone instruments and in various hybrid configurations. Recent research advances into quadrupole technology itself will be discussed; an account of ion trapping in the Kingdon trap and the Orbitrap™ mass spectrometer is included in the Supplementary Information for comparison.

Application of the MCNPX-McStas interface for shielding calculations and guide design at ESS

Recently, an interface between the Monte Carlo code MCNPX and the neutron ray-tracing code MCNPX was developed [1, 2]. Based on the expected neutronic performance and guide geometries relevant for the ESS, the combined MCNPX-McStas code is used to calculate dose rates along neutron beam guides. The generation and moderation of neutrons is simulated using a full scale MCNPX model of the ESS target monolith. Upon entering the neutron beam extraction region, the individual neutron states are handed to McStas via the MCNPX-McStas interface. McStas transports the neutrons through the beam guide, and by using newly developed event logging capability, the neutron state parameters corresponding to un-reflected neutrons are recorded at each scattering. This information is handed back to MCNPX where it serves as neutron source input for a second MCNPX simulation. This simulation enables calculation of dose rates in the vicinity of the guide. In addition the logging mechanism is employed to record the scatterings along the guides which is exploited to simulate the supermirror quality requirements (i.e. m-values) needed at different positions along the beam guide to transport neutrons in the same guide/source setup.

Enhancing neutron beam production with a convoluted moderator

We describe a new concept for a neutron moderating assembly resulting in the more efficient production of slow neutron beams. The Convoluted Moderator, a heterogeneous stack of interleaved moderating material and nearly transparent single-crystal spacers, is a directionally enhanced neutron beam source, improving beam emission over an angular range comparable to the range accepted by neutron beam lines and guides. We have demonstrated gains of 50% in slow neutron intensity for a given fast neutron production rate while simultaneously reducing the wavelength-dependent emission time dispersion by 25%, both coming from a geometric effect in which the neutron beam lines view a large surface area of moderating material in a relatively small volume. Additionally, we have confirmed a Bragg-enhancement effect arising from coherent scattering within the single-crystal spacers. We have not observed hypothesized refractive effects leading to additional gains at long wavelength. In addition to confirmation of the validity of the Convoluted Moderator concept, our measurements provide a series of benchmark experiments suitable for developing simulation and analysis techniques for practical optimization and eventual implementation at slow neutron source facilities.

Evidence of Ultrasonic Band Gap in Aluminum Phononic Crystal Beam

In this paper, we prove theoretically and experimentally the existence of complete ultrasonic band gap in phononic crystal beam. The phononic beam structure studied is composed of a linear lattice array of square pillars on a beam, made with aluminum-fortal easily machinable at centimetric scale. Ultrasonic characterization of phononic beam guides shows the existence of a frequency range where the transmitted signals are strongly attenuated, due to the presence of ultrasonic band gap, in agreement with theoretical results predicted by finite element simulation. These structures present a potential for the use as energy loss reduction in micromechanical resonators at high frequency regime.

An Investigation of Guiding of Positrons Through Insulating Capillaries

Guiding of diffuse low-intensity positron and electron beams through macroscopic tapered insulating capillaries was investigated. Transmitted positrons and electrons were observed. However, further investigations are necessary to clarify whether the transmitted particles are a true indication of guiding or simply due to a range of diffuse angles of the incoming beams.

Comments on “Effect of Beam Premodulation and Guide Magnetic Fields on Slow Wave Free Electron Laser: Nonlocal Theory”

The article comments on the original article by Bhasin and Sharma, which discussed the effect of beam premodulation and guide magnetic fields on slow wave free electron laser. Maraghechi claim that a pre-modulated beam was not used and only a uniform beam with constant energy has been used and present amended versions.