Quadrupole Lenses Research Articles

First direct-write lithography results on the Guelph high resolution proton microprobe

The recently completed high-resolution proton microprobe at the University of Guelph is Canada’s first one-micron nuclear microprobe, which represents the country’s state-of-the-art technology for various nuclear microprobe applications, e.g. direct-write microlithography. Its probe-forming system is comprised of a triplet Oxford Micro beams magnetic quadrupole lenses, along with high-precision objective slits. High energy protons coming off a 3MV particle accelerator can achieve a nominal resolution of one micro and a beam current of several hundred of picoamperes when arriving at the target. This proton probe is ideal for the use of direct-write lithography with the incorporation of a magnetic scanning system and motorized sample stage.Preliminary lithography results have been obtained using spin-coated PMMA photoresist as specimen. The beam spot size, beam range and straggling inside the substrate and the exposure conditions are investigated by using scanning electron microscopy. This facility is the first in Canada to perform focused direct-write ion beam lithography, which is ideal for modification and machining of polymer and semiconductor materials for biological, microfluidic and ultimate lab-on-chip applications.

One-stage probe-forming systems with quadrupole lenses excited by individual power supplies

The work deals with the ion-optical characteristics of the probe-forming systems based on a quadruplet of magnetic quadrupole lenses with four power supplies. The excitation of the lenses of a final doublet of such system is determined from the stigmatic focusing conditions, and the excitations of the first two lenses (downstream the beam) are free parameters which form a parametric set of the probe-forming systems. For this parametric set, the system acceptance reduced to the envelope dimensions in the target plane is determined as a figure of merit for the optimization task. The solution of this task gives optimal excitations of the first two lenses allowing an increase in demagnifications and acceptance of the probe-forming systems with individual power supplies in comparison with a separated Russian quadruplet.

Nonlinear processes of probe formation of a beam with inhomogeneous phase density at nuclear microprobe

The work describes nonlinear processes of probe formation on the target with allowance for an inhomogeneous density of ion distribution in phase space in the object collimator plane taken from experimental data. The chromatic aberrations, intrinsic aberrations of the 3rd order and parasitic aberrations caused by sextupole and octupole components of the magnetic quadrupole lens field have been taken into account in the object-target phase coordinate transformation. The criterion of obtaining the optimal resolution was defined as the minimum spot size (FWHM) for a fixed ratio IFWHM/I0 of beam current in this spot to the total beam current. The conditions for which the initial density of ion distribution in phase space is matched with the ion-optical characteristics of the probe-forming system were considered. The influence of axial brightness and parasitic sextupole and octupole field components on the beam current distribution at the target has been determined.

Use of a line focus of a quadrupole multiplet for irradiating millimeter length lines

We have developed a new method of irradiation suitable for uniformly irradiating long, straight lines for waveguide and channel fabrication in semiconductors and polymers. This is achieved by exciting the quadrupole lenses of a nuclear microprobe in a manner such that the beam is focused in one plane but highly defocused in the orthogonal plane. This method requires no surface mask and since the beam is not scanned, it produces uniformly-irradiated patterns. This approach has been used for rapid exposure of lines 8 mm in length with widths of about 3 μm in silicon and 1.5 μm in polymethyl methacrylate.

Design and optimization of multipole lens and Wien filter systems

The differential algebra (DA) method has been employed to compute the optical properties and aberrations up to the fifth order of multipole systems containing electrostatic and magnetic round, quadrupole, hexapole and octopole lenses, and Wien filters. A new software package has been developed, which computes the geometrical and chromatic aberrations up to the fifth order by using a single DA ray trace. It also has an optimization module where a weighted set of aberrations can be minimized by the automatic adjustment of a set of user-defined system variables. In this paper, we present our new method for designing and optimizing multipole systems including Wien filters, and illustrate its application with three relevant examples.

Ion, X-ray, UV and Neutron Microbeam Systems for Cell Irradiation.

The array of microbeam cell-irradiation systems, available to users at the Radiological Research Accelerator Facility (RARAF), Center for Radiological Research, Columbia University, is expanding. The HVE 5MV Singletron particle accelerator at the facility provides particles to two focused ion microbeam lines: the sub-micron microbeam II and the permanent magnetic microbeam (PMM). Both the electrostatic quadrupole lenses on the microbeam II system and the magnetic quadrupole lenses on the PMM system are arranged as compound lenses consisting of two quadrupole triplets with "Russian" symmetry. Also, the RARAF accelerator is a source for a proton-induced x-ray microbeam (undergoing testing) and is projected to supply protons to a neutron microbeam based on the (7)Li(p, n)(7)Be nuclear reaction (under development). Leveraging from the multiphoton microscope technology integrated within the microbeam II endstation, a UV microspot irradiator - based on multiphoton excitation - is available for facility users. Highlights from radiation-biology demonstrations on single living mammalian cells are included in this review of microbeam systems for cell irradiation at RARAF.

Harmonic method for measuring and correcting amplitude functions in the circular accelerator

Free oscillations of particles in the ring’s focusing system with a variable gradient are described by the amplitude function (beta function) and the phase function. The gradient perturbation leads to distortions in these functions. Beta-function distortions reduce the ring acceptance, especially if the working point on the betatron frequency is close to the half-integer resonance. A new method for calculating the current in the windings of correcting quadrupole lenses is presented. The idea of this method consists of the excitation of the closed orbit distortions with the dipole magnet. A comparison of the measured values of these orbits in the pickup with calculated values for the ideal gradients presents the opportunity to calculate the resonant harmonics of the beta-function distortions and then adjust them using quadrupole correctors. The algorithm of the method and the preliminary results of applying it to the SIS 100 synchrotron are given.

Development of Multi-Turn Time-of-Flight Mass Spectrometers and Their Applications

The mass resolution of a time-of-flight (ToF) mass spectrometer is directly proportional to its total flight path length. We have developed multi-turn ToF mass spectrometers, where ions are stored in a fixed orbit within electrostatic sectors and allowed to propagate the said orbit numerous times. With each successive orbit, the flight path is correspondingly increasing. The first multi-turn ToF mass spectrometer, the MULTUM Linear plus, was developed for cometary exploration. The spectrometer consists of four cylindrical electrostatic sectors and 28 electrostatic quadrupole lenses. The size of the analyzer is 40 cm square. Mass resolution is demonstrated to increase according to the number of ion cycles. A mass resolution of greater than 350,000 was achieved after 501.5 cycles. Another multi-turn ToF mass spectrometer, the MULTUM II, which consists of only four toroidal electrostatic sectors, was also developed in an effort to reduce the number of quadrupole lenses. We are developing various types of mass spectrometer based on the MULTUM II technology, a ToF/ToF mass spectrometer "MULTUM- TOF/TOF", a stigmatic imaging mass spectrometer "MULTUM-IMG" and miniature mass spectrometers of high mass resolving power, the "MULTUM-S" series.

Optimization of the quadrupole probe-forming system with individual power supplies for lenses

This study reviews a quadruplet of magnetic quadrupole lenses, where each lens is fed from an individual power supply. In this case the power supplies of two last lenses (along the course of the beam) are selected from the condition of ensuring the stigmatic focusing, while the power supply values of two first lenses are free parameters. These parameters form a two-parameter set, where the functional characterizing the acceptance of a probe-forming system is determined. It has been shown that the use of four individual power supplies for lenses in the quadruplet allows us to make the acceptance more than two times larger.

Characterization and control of ion sources from ultra-short high-intensity laser–foil interaction

The unprecedented properties of laser accelerated ion beams result from a highly organized ion emission scenario at the laser-driven source. Multi-channel high resolution ion spectroscopy reveals exact and strong correlation between spectral characteristics and ion trajectories in the beam. These properties are coupled to a well defined ion source evolution as suggested by the experimental data. Such beams are ideal candidates for manipulation with well-established ion beam optics. This is demonstrated with a set of magnetic quadrupole lenses in order to achieve beam collimation and monochromatization.

Investigation of the Optical Properties of the Achromatic Quadrupole Lens by Using the Rectangular Potential Distribution Model

An optimization calculation is made to find the optimum properties of combined quadrupole lens which consists of electrostatic and magnetic lens. Both chromatic and spherical aberration coefficients are reduced to minimum values and the achromatic aberration is found for many cases. These calculations are achieved with the aid of transfer matrices method and using rectangular model of field distribution, where the path of charged-particles beam traversing the field has been determined by solving the trajectory equation of motion and then the optical properties for lens have been computed with the aid of the beam trajectory along the lens axis. The computations have been concentrated on determining the chromatic and spherical aberration coefficients in both convergence and divergence planes and the effects of changing both of excitation and effective length of lens are studied.

Investigation of the Optical Properties of the Achromatic Quadrupole Lens by Using the Rectangular Potential Distribution Model

An optimization calculation is made to find the optimum properties of combined quadrupole lens which consists of electrostatic and magnetic lens. Both chromatic and spherical aberration coefficients are reduced to minimum values and the achromatic aberration is found for many cases. These calculations are achieved with the aid of transfer matrices method and using rectangular model of field distribution, where the path of charged-particles beam traversing the field has been determined by solving the trajectory equation of motion and then the optical properties for lens have been computed with the aid of the beam trajectory along the lens axis. The computations have been concentrated on determining the chromatic and spherical aberration coefficients in both convergence and divergence planes and the effects of changing both of excitation and effective length of lens are studied.

Study of a Focusing Quadrupole Lens for Low-Energy CarbonIons

The focusing quadrupole lens consists of an assembly of four magnets, where the magnets together produce a good approximation of quadrupole elds through which ions are passing. By varying the strength of the magnetic elds, the traveling charged heavy ions could be kept within the system, where the magnets are set in an iron cylinder with coils through which currents ow. The employed focusing system consists of three consecutive quadrupoles (triplet), where the middle one is twice longer and is rotated by 90 degrees around the central axis. The ions are focused along one direction while being defocused along the other direction at the rst quadrupole. Since the middle one is rotated by 90 degrees around the central axis the diverged ions are forced into the central axis (focusing e ect) along double the distance. Finally the net e ect after traveling through the system of the three quadrupoles is focusing in all directions In this study, the focusing e ect of the quadrupoles for carbon ions at di erent lengths of the middle quadrupole with a velocity of 0.01c (c = 3.0 108 m/s) along the z-direction is demonstrated by tracking the number of ions starting evenly distributed along the circumference of a circle with a 3 cm diameter in the transverse plane, by assuming the initial transverse velocity to be zero. From the simulation results, the ions are focused e ectively in the case of a quadrupole lens having twice the length of the middle one.

Performance of the Sumy nuclear microprobe with the integrated probe-forming system

The integrated probe-forming system for the Sumy nuclear microprobe comprises two doublets of magnetic quadrupole lenses of new design. Each doublet has been made from a single piece of soft iron by electro-discharge machining. This paper describes the performance tests of the microprobe including the beam scanning control and data acquisition systems. In the first runs a spot size of about 2 μm (FWHM) was obtained for the high beam current mode (up to 200 pA) by scanning a conventional copper grid with 1000 meshes per inch. Simulated beam optics parameters are compared with the experimental data.

Recent status of the Kiev nuclear probe

The modified Van de Graaff accelerator with proton beam energy W ⩽ 3 MeV has been installed and put into operation at the TMM laboratory in Kiev. The laboratory incorporates the nuclear probe (NP) beam line, coupled to this accelerator. A short version of an optimized probe-forming system (PFS) has been developed for the Kiev NP. The system is based on divided triplet of the magnetic quadrupole lenses (MQLs). This PFS has two working regimes for the probe operations. The results of numerical calculations of the geometrical and ion-optical parameters of the PFS are presented. It is shown that this versatile PFS is a promising design for a modern nuclear nano-probe. A new precision adjustable MQL has been designed. Three lenses, the slit systems and target chamber are manufactured and installed at the Kiev probe beam line. Also a new data acquisition system for the Kiev NP is being developed.

Optimization of the working distance of an ion microprobe-forming system

A high-resolution ion microprobe necessitates the use of a small working distance (the distance from the final quadrupole lens of a probe-forming system to the specimen) in order to produce a large demagnification. But at the same time a small working distance is a source of a number of practical difficulties. We have presented an approach for determining a working distance that provides the best spatial resolution with the main practical limitations taken into account. We used a probe-forming system acceptance as a criterion of optimality. The calculations have revealed the existence of an optimal working distance in a set of common probe-forming systems, but it can be achieved only after changing of a design of a final quadrupole lens. We proposed a possible design of conic lens that allows solving the problem of detectors location and creating a short focus system. Three-dimensional calculations of magnetic field within this lens predicted a good quality of field structure.

Modeling and magnetic measurements of TNK synchrotron radiation source magnets

The TNK synchrotron radiation source is being built by Budker Institute of Nuclear Physics on the base of Lukin State Research Institute of Physical Problems. Magnetic system for the storage ring of TNK synchrotron radiation source was produced at the BINP. It consists of 6 superperiods and includes 24 dipole magnets, 72 quadrupole lenses, 36 sextupole lenses and 12 octupole lenses.The storage ring will operate in a wide range of energies—from 450 to 2200 MeV—which corresponds to 0.3–1.5 T magnetic field in dipole magnets. Dipole magnets have H-shape solid yokes from Armco iron with a curved form. Dipole gap is 42 mm and yoke straight length is 1447 mm. The results of 3D magnetic field modeling executed by means of Mermaid 3D are presented. All dipole magnets were magnetically measured by special Hall probe measurement system developed in BINP. The results of magnetic measurements and modeling are compared and analyzed.

高エネルギー電子移動解離が可能なタンデム質量分析装置の開発

A JEOL JMS-HX110 double-focusing mass spectrometer was combined with the collision cell and spherical electric sector of a HITACHI M80-B instrument to perform tandem mass spectrometry experiments. A quadrupole lens doublet was mounted between the mass spectrometer and the collision cell to improve ion transmission into the collision cell. The detection system was also improved to expand the mass range of product ions. These improvements provided reliable spectra of high-energy electron transfer dissociation (HE-ETD) of peptides using an alkali metal target. The present results demonstrated that HE-ETD by a single collision with an alkali metal target could determine the amino acid sequence and phosphorylation site of peptides.

Hi high-sensitivity detector for the neutrino investigations on the electron magnetic spectrometer

At present, the Udmurt State University together with the Physical-Technical Institute Ural Branch Russian Academy of Science have build and are adjusting the unique 100-cm electron magnetic spectrometer with double focusing by the uniform field 2 that has the resolution of 10−4 [1]. For the precise determination of the energy of electrons that are formed during the reaction ve+ d ⟩ e− +p + p with the use of the electron magnetic spectrometer, an experimental unit for the system of highly susceptible high-speed parallel electron recording based on microchannel plates has been developed. The electrons formed penetrate into an energy-analyzer with the help of a quadrupole lens where they are dispersed by energies in the magnetic field and focused on the spectrometer focal plane. The presence of the focal plane in spectrometers with magnetic focusing gives a unique opportunity of the simultaneous record of electrons having different energies that are focused upon it, which is not possible to carry out on electrostatic spectrometers. For the signal increase, a herringbone assembly with three microchannel plates is used; each plate has multiplication factor of 106 and a resistive position-sensitive sensor. This type of a detector is several orders more efficient than an ordinary channel electron multiplier.

Optimization of electrostatic lens systems for low-energy scanning microcolumn applications

The optimization of a low-energy scanning microcolumn is proposed by adopting a modified Einzel lens sandwiched between an aligner and a deflector. The modified Einzel lens is composed of four electrodes, and the two center electrodes are specially designed quadrupole lenses having keyhole type rather than circular apertures. The outer electrodes of the Einzel lens having circular apertures are grounded, and the quadrupole lens is operated by applying the quadrupole voltages. The effects of the separated deflector system and the static quadrupole lens were investigated by analyzing the scanning electron beam spot at the target, and the results show that the proposed system can improve the performance of the scanning microcolumn.