Transverse Optics Research Articles

Mitigation of the microbunching instability through transverse Landau damping

The microbunching instability has been a long-standing issue for high-brightness free-electron lasers (FELs) and is a significant showstopper to achieve full longitudinal coherence in the x-ray regime. This paper reports the first experimental demonstration of microbunching instability mitigation through transverse Landau damping, based on linear optics control in a dispersive region. Analytical predictions for the microbunching content are supported by numerical calculations of the instability gain. The effect is confirmed through the experimental characterization of the spectral brightness of the FERMI FEL under different transverse optics configurations of the transfer line between the linear accelerator and the FEL. Published by the American Physical Society 2024

Transverse and Longitudinal Optical Phonon Analysis of Silicon dioxide (SiO2) from Rice Husk Charcoal

Abstract Rice husk is one of the biggest wastes from rice production. Rice husk can be used as an alternative in producing silicon dioxide (SiO2). Silicon dioxide is widely used in various industries, such as glass, ceramics, tires and electronics. In this paper, charcoal from rice husks is annealed at various temperatures of 800 °C, 850 °C and 900 °C and then characterized using FTIR. In previous studies, analysis using FTIR was able to show the functional groups of Silicon dioxide found in rice husk charcoal. FTIR data modified with the Kramers-Kronig (KK) equation can produce Longitudinal Optics (LO) and Transverse optics phonon (TO) values. The LO and TO values are the optical properties of the Silicon dioxide from rice husk charcoal. In addition, the value of the dielectric function can also be obtained. Based on the results, it shows that the LO values for each treatment were 907.47 cm−1, 958.62 cm−1, and 986.67 cm−1. The TO values for each treatment were 903.61 cm−1, 954.00 cm−1 and 964.41 cm−1. The dielectric function values of each treatment were 512.00 cm−1, 962.48 cm−1 and 1007.00 cm−1. By analyzing the optical-phonon parameters of Transverse Optics (TO) and Longitudinal Optics (LO), we succeeded in characterizing the SiO2 properties with the variations of annealing temperature. We determined that the TO and LO were not-monotonously affected by the variation in annealing temperature, which was determined by studying the optical-phonon wavelengths.

Studies on Transverse Resonance Island Buckets in third and fourth generation synchrotron light sources

A Transverse Resonance Island Bucket optics has a betatron tune close to a resonance, such that the particle motion is governed by non-linear terms in the equation of motion. This results in additional stable fixed points in transverse phase-space, which can be populated with a single RF-bunch filling pattern. Thus, these optics have the potential of providing pseudo single-bunch operation, i.e. allows some beamlines to receive light pulses at the revolutionary frequency while the remaining beamlines continue to receive pulses with a frequency set by the ring RF. By blocking either the synchrotron radiation from the standard orbit or secondary orbit each beamline can individually choose whether they want multi- or single-bunch synchrotron radiation. Transverse Resonance Island Bucket optics were achieved in both MAX IV storage rings. In particular, the optics of the 1.5 GeV ring has been characterized both theoretically and experimentally, and we show that TRIBs are achieved in a lattice without any octupolar elements. Furthermore, a feasibility study was performed which indicates that the beamlines of the 1.5 GeV ring could make use of the synchrotron radiation from the island orbit while blocking the standard orbit radiation.

Nanoparticulate CdS 2D array by chemical bath deposition: Characterization and optoelectronic study

Nanostructured CdS thin film was successfully deposited on glass by chemical bath deposition (CBD) at 80 °C. The effect of deposition time on the morphology, composition, optical and optoelectronic properties of nanostructured CdS thin films has been studied. The CBD-grown CdS thin films showed random arrangement of interconnected nanoparticles in 2D morphology. Nanostructured CdS thin films exhibited metastable cubic phase having uniform, compact and defect-free structure with enhanced crystallinity. Tauc plot of CBD-grown nanostructured CdS thin film showed an optimum band gap of 2.30 eV and a resonant Raman peak at 302 cm−1. The transverse optics (TO) mode, multi-phonon scattering and high-order replicas of nanostructured CdS thin films were also observed. Metal-semiconductor-metal (MSM) based CdS Photodetector (PD) showed an excellent photodetectivity of 2.6 × 1013 Jones. Photoconductive performance such as photo-sensitivity (207%) and - responsivity (0.38 A/W @ 420 nm) under an illumination condition was obtained for application in visible-light photodetector.

Commissioning and first results of the Fermilab Muon Campus

In the following years, the Fermilab Muon Campus will deliver highly polarized muon beams to the Muon $g\ensuremath{-}2$ experiment. The Muon Campus contains a target section wherein secondaries are produced, the delivery ring which separates the muons from the rest of the beam, and a sequence of beam lines that transports them to the Muon $g\ensuremath{-}2$ storage ring. Here, we report the first results of beam measurements at the Muon Campus with an emphasis on the key achievements that have contributed to the successful beam delivery to the Muon $g\ensuremath{-}2$ experiment. These achievements include the production of an intense secondary beam from the target, its transport over 2 km, the successful monitoring of muons from the available diagnostics, and the development of techniques for measuring the transverse optics. We also present detailed comparisons between the experimental data and simulation and discuss the similarities and differences observed.

First measurement of traverse beam optics for the Fermilab Muon Campus using a magnet scanning technique

In the following years the Fermilab Muon Campus will deliver highly polarized muon beams to the storage ring of the Muon g-2 Experiment. The transmission fraction of the storage ring has been shown to depend strongly on the transverse optics of the injected beam. Unfortunately, the current diagnostics in the Muon Campus allow only measurement of the beam configuration space which limits how well propagation can be predicted. This paper demonstrates an experimental technique based on a conventional magnet scan to obtain the Twiss parameters at a point, using only beam profiles such that installation of new equipment is not required. A proof-of-principle experiment is presented which shows that this new method is applicable to the Muon Campus, offering a viable approach to optimization of injection in the Muon g-2 Experiment.

Minimization of transverse beam-emittance growth in the 90-degree bending section of the RAON rare-isotope accelerator

The major contribution of the transverse beam emittance growth (EG) in a RAON heavy-ion accelerator comes from the bending section, which consists of a charge-stripping section, a matching section, and a charge-selection section in sequence. In this paper, we describe our research to minimize the two-dimensional EG in the 90-degree bending section of the RAON currently being developed in Korea. The EG minimization was achieved with the help of multi-objective genetic algorithms and the simplex method. We utilized those algorithms to analyze the 90-degree bending section in a driver linac for the in-flight fragmentation system. Horizontal and vertical EGs were limited to below 10 % in the bending section by adjustment of the transverse beam optics upstream from the charge-stripping section, redesign of the charge-selection section, and optimization of the vertical beam optics at the entrance of a charge-selection section.

Low energy ion beam dynamics of NANOGAN ECR ion source

A new low energy ion beam facility (LEIBF) has been developed for providing the mass analyzed highly charged intense ion beams of energy ranging from a few tens of keV to a few MeV for atomic, molecular and materials sciences research. The new facility consists of an all permanent magnet 10GHz electron cyclotron resonance (ECR) ion source (NANOGAN) installed on a high voltage platform (400kV) which provides large currents of multiply charged ion beams. Higher emittance at low energy of intense ion beam puts a tremendous challenge to the beam optical design of this facility. The beam line consists of mainly the electrostatic quadrupoles, an accelerating section, analyzing cum switching magnet and suitable beam diagnostics including vacuum components. The accelerated ion beam is analyzed for a particular mass to charge (m/q) ratio as well as guided to three different lines along 75°, 90° and 105° using a large acceptance analyzing cum switching magnet. The details of transverse beam optics to all the beam lines with TRANSPORT and GICOSY beam optics codes are being described. Field computation code, OPERA 3D has been utilized to design the magnets and electrostatic quadrupoles. A theoretical estimation of emittance for optimized geometry of ion source is given so as to form the basis of beam optics calculations. The method of quadrupole scan of the beam is used to characterize the emittance of the final beam on the target. The measured beam emittance increases with m/q ratios of various ion beams similar to the trend observed theoretically.

Symmetric single-quadrupole-magnet scan method to measure the 2D transverse beam parameters

Precise measurements of the transverse beam parameters are essential to control and optimize all types of charged particle beams. In this paper we present a novel method that uses one quadrupole magnet and one profile monitor to measure the transverse beam emittance and optics. In comparison to a conventional single-quadrupole scan measurement, this new technique measures the two transverse planes simultaneously. This novel procedure is faster, more intuitive and allows keeping under control the required quadrupole gradient and the beam sizes at the profile monitor. The application of the method is illustrated with the SwissFEL Injector Test Facility.

Study on internal short-range order microstructure characteristic of SiO2 thin film

SiO2 is one of important low refractive index materials, and SiO2 films are prepared by both ion-beam sputtering (IBS) and electron-beam evaporating (EB) technology. Dielectric constants of SiO2 films are calculated by infrared spectrum inversion technique in a wavenumber range from 400 cm-1 to 1500 cm-1. Through analyzing dielectric energy loss function, the oscillation frequency and the Si–O–Si angle of two types of SiO2 films are obtained in the transverse optics and longitudinal optics oscillating mode. The research results indicate that the attended modes of SiO4 are main coesite-like structure, three-plane folding ring structure, and keatite-like structure in the range of short-range order for EB-SiO2 films, but the attended modes of SiO4 are main coesite-like structure, three-plane folding ring structure, four-plane folding ring structure, and keatite-like structure in the range of short-range order for IBS-SiO2 films.

An improved transfer map approach to longitudinal beam dynamics

In this paper we present our transfer map approach for studying longitudinal beam dynamics. It combines synchrotron motion mapping equations with Differential Algebraic transfer map extraction. The novel approach can take into account a variety of effects, including non-relativistic effects, arbitrary changes to RF voltage and synchronous phase, as well as nonlinearities and coupling between transverse and longitudinal beam optics. All these are made possible efficiently and accurately, without the need for time consuming element-by-element 6D particle tracking. Moreover, longitudinal space charge effects can be readily treated too. The utility of this approach is demonstrated by applying it to the study of ion beam acceleration in a proposed pre-booster ring of the Medium Energy Electron Ion Collider (MEIC) facility at TJNAF.

Measuring the bunch frequency multiplication at the 3rd CLIC Test Facility

The CLIC Test Facility 3 (CTF3) is being built and commissioned by an international collaboration to test the feasibility of the proposed Compact Linear Collider (CLIC) drive beam generation scheme. Central to this scheme is the use of RF deflectors to inject bunches into a delay loop and a combiner ring, in order to transform the initial bunch frequency of 1.5 GHz from the linac to a final bunch frequency of 12 GHz. To do so, the machine's transverse optics must be tuned to ensure beam isochronicity and each ring's length can finally be adjusted with wiggler magnets to a sub millimeter path length accuracy. Diagnostics based on optical streak camera and RF power measurements, in particular frequency bands, have been designed to measure the longitudinal behaviour of the beam during the combination. This paper presents the diagnostics and recent commissioning measurements.

Transverse envelope analysis for accelerating relativistic electron beams in a linear accelerator as a photon source

Since recent progress of electron guns extends the application of linear accelerators to photon radiation sources, the design and optimization of transverse beam optics over a linear accelerator become important. In this paper, we propose a transverse beam envelope analysis for accelerating beams in a linear accelerator using symplectic matrices based on a normalized emittance. This approach allows a description of the transverse envelope function, which reflects the characteristics of beam optics. Since the envelope function is described in the same phase space as photon radiation, it provides an effective and powerful tool for the design and optimization of the beam optics as a photon source. The emittance based formalism of the beam envelope, which was previously described by Douglas, Kewisch, and York, is first introduced for impulse acceleration, and then extended to a thick accelerator structure. The transverse beam envelope analyses, such as error sensitivity, chromatic aberration, and emittance growth, are presented by applying second-order perturbation treatment to a formulated matrix describing a quasi-periodic lattice in the linear accelerator system.

Transverse nonlinear optics in heavy-metal-oxide glass

We investigate beam propagation in a heavy-metal-oxide glass of the group ${\text{Nb}}_{2}{\text{O}}_{5}--\text{PbO}--{\text{GeO}}_{2}$ using picosecond pulses in the near infrared. We observe a wavelength-dependent self-focusing, with beam collapse and modulation instability in the Kerr regime at $1.064\text{ }\ensuremath{\mu}\text{m}$ and stable spatial solitons at 820 nm where multiphoton absorption is present. We report near-infrared beam self-confinement and solitons, filamentation, interactions, and conical emission in the ps regime and discuss them with the aid of a numerical model.

Nonlinear lensing mechanisms in a cloud of cold atoms

We present an experimental study of nonlinear lensing of near-resonant light by a cloud of laser-cooled rubidium atoms, specifically aimed at understanding the role of the interaction time between the light and the atomic vapor. We identify four different nonlinear mechanisms, each associated with a different time constant: electronic nonlinearity, Zeeman optical pumping, hyperfine optical pumping and radiation pressure. Our observations can be quite accurately reproduced using a simple rate equation model which allows for a straightforward discussion of the various effects. The results are important for planning more refined experiments on transverse nonlinear optics and self-organization in samples of cold atoms.

Dental OCT

We present here the first in vivo optical coherence tomography (OCT) images of human dental tissue. A novel dental optical coherence tomography system has been developed. This system incorporates the interferometer sample arm and transverse scanning optics into a handpiece that can be used intraorally to image human dental tissues. The average imaging depth of this system varied from 3 mm in hard tissues to 1.5 mm in soft tissues. We discuss the application of this imaging system for dentistry and illustrate the potential of our dental OCT system for diagnosis of periodontal disease, detection of caries, and evaluation of dental restorations.

Transverse nonlinear optics: Introduction and review

The characteristics features of the field of Transverse Nonlinear Optics are briefly illustrated, as an introduction to this special issue of Chaos, Solitons & Fractals.

Some applications of particle-in-cell codes to problems of high intensity beams

The technique of using the “particle-in-cell” method was developed in the field of plasma physics [1]. Borrowed for problems of intense beams, it becomes an especially powerful tool because such problems frequently use single species “plasmas” and so pose a less severe requirement on the computer. We will look at several problems in which the PIC code method has been useful. The first is the classical Pierce gun in a transient or short pulse mode. Here the transverse beam optics is strongly affected by the time dependence of the current. The second is a study of high power klystrons searching for the source of an instability. The third is the high power rf source called the “lasertron” which is under development at SLAC. The interesting new development for the lasertron simulation is the introduction of a double gap output cavity for improved efficiency. The lasertron and klystron simulations are steady state solutions to rf problems with high- Q cavities. In order to limit the computation to a realistic time, these simulations use an external equivalent circuit which can communicate with the beam tunnel through ports placed at the locations of the rf cavities. Application for electron beams generally require using a fully relativistic electromagnetic code such as MASK. In some applications, the computation can be speeded up by limiting the solution of the fields to the electrostatic conditions. This can be especially helpful if the degree of precision required demands very large numbers of macroparticles. As a last example, we will show the use of this technique for a problem involving emittance growth for a high intensity beam for heavy ion fusion.