Deceleration Lens Research Articles

Compact 2D electron analyzer CoDELMA: Simultaneous wide reciprocal and real space analysis using wide-angle deceleration lens, CMA and projection lens

A compact wide-acceptance angle (around ± 50°) high-energy-resolution 2D electron analyzer CoDELMA (Compact DELMA) is proposed, constructed and tested. CoDELMA is composed of a recently-proposed variable-deceleration-ratio wide-acceptance-angle electrostatic lens (VD-WAAEL), a cylindrical mirror analyzer (CMA) and a projection lens. After a brief review of VD-WAAEL, the use of a plane grid in the lens is presented as a new design option, which allows keeping the focusing angle almost constant irrespective of the deceleration ratio. A detailed consideration is given to the combination of CMA and a projection lens, which allows simultaneous analysis of wide reciprocal ( ± 8°) and real space ( ± 5 mm) at the entrance of CMA. CoDELMA is the successor to the previously developed DELMA instrument including a concentric hemispherical analyzer. The whole system of CoDELMA becomes much more compact than that of DELMA owing to the use of VD-WAAEL and CMA, and this results in considerable reduction of the production cost. Results of test measurement of energy spectrum and angular distribution using an electron gun as an excitation source confirmed that the energy resolution and the acceptance angle are almost the same as the designed values.

Design and simulation of a low-energy single ion irradiation system for micro/nano-biosample investigation

A low-energy single ion irradiation system is developed in its initiation in Thailand to follow one of the trends in novel ion beam technology exploitation. Single ion irradiation of materials is a highly technological development of ion beam technology. The developed single ion irradiation systems worldwide are primarily in the MeV-energy range and for single cell studies, and recently the trend has been extended to the low-energy range (< 100 keV) but focused on microelectronic applications. Based on our previous research on low-energy ion beam irradiation of biological cells and DNA, we design and simulate a low-energy single ion implantation system, aiming at eventual construction of such a novel ion beam apparatus for applications to the biological studies. In the system, the ion energy is decreased to orders < 1 keV by the existing deceleration lens, then the low-energy ion beam passes through µm slits, and finally, low-energy single ions are obtained by beam scanning with appropriate frequencies from scanner plates and detected by a single ion detection device. Conceptual design, calculation and simulation of this single ion system are presented.

Deceleration of highly charged Ni ions with compressed longitudinal kinetic energy distribution by a falling potential

Higher-precision optical clocks based on highly charged ions (HCIs) have become one of the means to explore new physics beyond the standard model. Usually, HCIs are produced by electron bombardment with high kinetic energy. Therefore, to realize an optical clock, the deceleration of HCIs is necessary. In this study, the design and operation of a deceleration beamline to produce low-energy HCIs are presented. We used time-of-flight technology to select pure 58Ni12+ ions. The longitudinal kinetic energy distribution of the ion beam was compressed from 11.4(4)qV (q is the electric charge of ions) to 2.2(3)qV by employing a rapidly decreasing voltage. Adopting a deceleration lens system, the longitudinal kinetic energy of the 58Ni12+ ions was reduced from 678.2(3)qV to 2.0(3)qV.

A compact, flexible low energy experimental platform of highly charged ions for atomic physics experiments

A new, compact and flexible low energy experimental platform of highly charged ions (HCIs) based on an electron beam ion source of the Dresden EBIS-A type is presented. The so-called IMP EBIS-A Facility of the Institute of Modern Physics (IMP) in Lanzhou is designed as a user facility for the state-resolved charge exchange studies in HCIs with atoms and molecules collisions by cold target recoil ion momentum spectroscopy. The important feature of this facility is that it can provide high charge state and low energy heavy ions at room temperature and limited space. The IMP EBIS-A facility consists of a Dresden EBIS-A ion source, a Wien filter as well as beam focusing and beam diagnostics elements. All components are installed on a small high voltage platform connected with an ion beam deceleration and acceleration lens assembly. The testing results reached and exceeded the expectation of the design. Utilizing the cold target recoil ion momentum spectroscopy, the first experiment of state-resolved charge transfer based on the IMP EBIS-A facility was introduced.

Critical low-energy Ar-ion beam conditions to induce direct DNA double strand break

Abstract Ultra-low-energy ion interaction with naked DNA has been an interesting research topic as it can reveal fundamentals involved in charged particle irradiation effect on life as well as biological evolution. This study was a detailed investigation on ultra-low-energy argon ion bombardment effects on naked DNA. Argon ion beam was decelerated by a deceleration lens to ultra low energy ranging from about 1 keV down to a few tens of eV to bombard naked DNA plasmid pGFP to fluences of 1, 2 and 4 × 1015 ions/cm2. After ion bombardment, gel electrophoresis analyzed changes in the DNA topological form. The result showed that the DNA form changed, including from original supercoiled to damaged relaxed and linear forms, certainly depending on the ion energy and fluence. The DNA form changes as functions of the ion energy and fluence were quantified. It was found that the critical Ar-ion beam conditions were the energy 750 eV to be the lowest with the fluence 2 × 1015 ions/cm2 which could induce the linear DNA form, indicating direct double strand breaks, a more severe damage of DNA which might lead to mutation.

Low energy highly charged ion beam facility at Inter University Accelerator Centre: Measurement of the plasma potential and ion energy distributions

A deceleration lens coupled to one of the beam lines of the electron cyclotron resonance based low energy beam facility at Inter University Accelerator Centre is reported. This system is capable of delivering low energy (2.5 eV/q–1 keV/q) highly charged ion beams. The presence of plasma potential hinders the measurements of low energies (&amp;lt;50 eV), therefore, plasma potential measurements have been undertaken using a retarding plate analyzer in unison with the deceleration assembly. The distributions of the ion energies have been obtained and the effect of different source parameters on these distributions is studied.

Measurement of ultra-low ion energy of decelerated ion beam using a deflecting electric field

In investigation on ultra-low-energy ion bombardment effect on DNA, an ion beam deceleration lens was developed for high-quality ultra-low-energy ion beam. Measurement of the ion energy after deceleration was necessary to confirm the ion beam really decelerated as theoretically predicted. In contrast to conventional methods, this work used a simple deflecting electrostatic field after the deceleration lens to bend the ion beam. The beam bending distance depended on the ion energy and was described and simulated. A system for the measurement of the ion beam energy was constructed. It consisted of a pair of parallel electrode plates to generate the deflecting electrical field, a copper rod measurement piece to detect ion beam current, a vernier caliper to mark the beam position, a stepping motor to translate the measurement rod, and a webcam-camera to read the beam bending distance. The entire system was installed after the ion-beam deceleration lens inside the large chamber of the bioengineering vertical ion beam line. Moving the measurement rod across the decelerated ion beam enabled to obtain beam profiles, from which the beam bending distance could be known and the ion beam energy could be calculated. The measurement results were in good agreement with theoretical and simulated results.

English

This work focuses on the design and implementation of an electrostatic lens system to produce high-intensity, low-energy ion beams, by means of numerical simulation of the beam trajectories (SIMION 7). The lens design was optimized using the simulation data obtained with a performance characteristics&nbsp; of the electrostatic lens system. This lens system maintains good beam focal quality for the deceleration of heavy ion beams of argon ions of with space charge of 10 mA. The beam emittance and beam diameter as a function of the gap width for a decel voltage of 45 kv of a deceleration lens system for a singly charged argon ion trajectories were investigated.&nbsp; A&nbsp; gap width of 5 mm and a tube diameter&nbsp; of 26 mm&nbsp; were found to be the minimum values. Also, a minimum of 24 mm of inner tube diameter was obtained for the relation between the inner tube diameter and the beam diameter. Beam emittance and beam diameter as a function of the focusing points for a decel voltage of 45 kv of a deceleration lens system for a singly charged argon ion trajectories was studied. A minimum of 455 mm was obtained at the outer exit of the deceleration lens system. While for the beam diameter, a minimum of 460 mm was deduced. It was found&nbsp; also that, a minimum of&nbsp; Vdecel = 43 kV, deceleration voltage was obtained for the relation between the deceleration voltage and beam emittance. Also, a minimum of&nbsp; Vdecel = 49 kV was found for the relation between the decelration voltage and beam diameter. Key words: Deceleration lens system and decel voltage, SIMION computer program, Beam emittance and beam radius.

Measurement of Ultra-low Ion-Beam Energy

Measurement of ion-beam energy is important for assuring equipment operation. When an ion beam is decelerated, its energy becomes very low; the measurement of such low energy is investigated here. Low ion-beam energy has been measured using a retarding field and detector. This research, however, used a deflecting electrostatic field, a simpler and more accurate method. The basic principle of the electrostatic-field application for measuring ion-beam energy is that when an ion beam passes through parallel plates of the electrical field, the beam will be bent from its axial trajectory as a function of the applied field. The bending distance of the ion beam can be used to determine the ion-beam energy. Results of measuring ion-beam energy in this study were compared with theory and simulation results. The SIMION program version 8.0 was used to perform the simulation. A system to measure the ion-beam energy was designed, constructed and installed. The system consisted of a pair of parallel electrode plates, a copper rod measurement piece, a vernier caliper, a stepping motor and a webcam-camera. The entire system was installed under an ion-beam deceleration lens inside the big chamber of the 30-kV bioengineering vertical ion-beam line (CMU3) at Chiang Mai University. The copper rod was moved by the stepping motor to measure the ion-beam current profile, which depended on the beam spot position. The beam profiles were compared between the plates, with and without the electrostatic field, for extracting the ion-beam bending distance and then the ion-beam energy. The ion-beam current, which was on order of 10 nA, was measured by a digital nano-ammeter. Argon ion beams at various energies, ranging from 10 to 20 keV, passed through the deceleration lens resulting in ion energy lower than 1 keV. The measurement results were in good agreement with theoretical and simulated results, demonstrating that the method worked well.

An ion beam deceleration lens for ultra-low-energy ion bombardment of naked DNA

Study of low-energy ion bombardment effect on biological living materials is of significance. High-energy ion beam irradiation of biological materials such as organs and cells has no doubt biological effects. However, ion energy deposition in the ion-bombarded materials dominantly occurs in the low-energy range. To investigate effects from very-low-energy ion bombardment on biological materials, an ion beam deceleration lens is necessary for uniform ion energy lower than keV. A deceleration lens was designed and constructed based on study of the beam optics using the SIMION program. The lens consisted of six electrodes, able to focus and decelerate primary ion beam, with the last one being a long tube to obtain a parallel uniform exiting beam. The deceleration lens was installed to our 30-kV bioengineering-specialized ion beam line. The final decelerated-ion energy was measured using a simple electrostatic field to bend the beam to range from 10eV to 1keV controlled by the lens parameters and the primary beam condition. In a preliminary test, nitrogen ion beam at 60eV decelerated from a primary 20-keV beam bombarded naked plasmid DNA. The original DNA supercoiled form was found to change to relaxed and linear forms, indicating single or double strand breaks. The study demonstrated that the ion bombardment with energy as low as several-tens eV was possible to break DNA strands and thus potential to cause genetic modification of biological cells.

Ion Beam Simulation Using a Lens System for Acceleration and Deceleration of Low Energy Ion Beam

Ion Beam Simulation Using a Lens System for Acceleration and Deceleration of Low Energy Ion Beam The characteristics of electrostatic lens systems are studied with a view to applications in an ion-beam source. Rays are traced with the SIMION simulator, which offers a realistic description of space charge effects. Design of the lens system was done by using SIMION computer program. A parallel beam of singly charged nitrogen ions of diameter 10 mm with energy of 6 keV was started at a distance of 150 mm before entering the acceleration/ deceleration lens system. The lens system was optimized using the simulation data obtained with a SIMION computer program for calculating ion trajectories with and without space charge included. In order to design this lens system, we studied the two and three electrode lens systems with different parameters. Beam emittance as a function of the gap width of the deceleration lens system wasb studied for singly charged nitrogen ion trajectories downstream at 200 mm. Influence of the deceleration voltage on the deceleration electrode with different voltages of the four electrodes on the beam emittance was investigated with gap widths of 3, 5, 10, 15 and 21 mm. Deceleration lens system was used as an acceleration lens system by changing and optimising the voltage on each electroden of the lens system. Both the beam emittance and the beamb diameter were calculated at exit of the lens system at distance of 60 mm. The following calculations have been done with and without space charge.

Slow Highly Charged Ions by Electrostatic Deceleration

An electrostatic, cylindrical deceleration lens has been designed, fabricated and tested to slow down beams of highly charged ions. Highly charged ions from an electron cyclotron ion source at a few tens of keV per charge state are decelerated to a few eV/q using the electrostatic lens. The lens enables the study of the interaction of highly charged ions with matter at very low collision velocities.

An electrostatic deceleration lens for highly charged ions

The design and implementation of a purely electrostatic deceleration lens used to obtain beams of highly charged ions at very low energies is presented. The design of the lens is such that it can be used with parallel as well as diverging incoming beams and delivers a well focused low energy beam at the target. In addition, tuning of the final energy of the beam over a wide range (1 eV/q to several hundred eV/q, where q is the beam charge state) is possible without any change in hardware configuration. The deceleration lens was tested with Ar(8+), extracted from an electron cyclotron resonance ion source, having an initial energy of 30 keV/q and final energies as low as 70 eV/q have been achieved.

An electron cyclotron resonance ion source based low energy ion beam platform

To satisfy the requirements of surface and atomic physics study in the field of low energy multiple charge state ion incident experiments, a low energy (10 eV/q-20 keV/q) ion beam platform is under design at IMP. A simple test bench has been set up to test the ion beam deceleration systems. Considering virtues such as structure simplicity, easy handling, compactness, cost saving, etc., an all-permanent magnet ECRIS LAPECR1 [Lanzhou all-permanent magnet electron cyclotron resonance (ECR) ion source No. 1] working at 14.5 GHz has been adopted to produce intense medium and low charge state ion beams. LAPECR1 source has already been ignited. Some intense low charge state ion beams have been produced on it, but the first test also reveals that many problems are existing on the ion beam transmission line. The ion beam transmission mismatches result in the depressed performance of LAPECR1, which will be discussed in this paper. To obtain ultralow energy ion beam, after being analyzed by a double-focusing analyzer magnet, the selected ion beam will be further decelerated by two afocal deceleration lens systems, which is still under design. This design has taken into consideration both ions slowing down and also ion beam focusing. In this paper, the conceptual design of deceleration system will be discussed.

Approach for simultaneous measurement of two-dimensional angular distribution of charged particles. II. Deceleration and focusing of wide-angle beams using a curved mesh lens

Recently, it was shown that using an ellipsoidal mesh in an einzel-type lens, spherical aberration can be corrected over a wide acceptance angle of up to 120 degrees. The present paper creates the possibility for beam analysis by achieving dramatic improvements in deceleration lens capabilities. This provides a scheme for simultaneous angular distribution measurement suitable for application to high-energy charged-particle beams up to around 10 keV. We consider the behavior of wide-angle charged-particle beams in electrostatic fields given by simple solutions of the Laplace equation, starting with a discussion on a spherically symmetric deceleration field. A beam focusing over a wide acceptance angle of 100 degrees is found in a special spherically symmetric field. However, in many cases of the spherically symmetric field, focusing of wide-angle beams is obstructed by the presence of spherical aberration. We show that the spherical aberration can be corrected by two kinds of deformation of the spherically symmetric field, a deformation of the field under a spherical boundary condition and an ellipsoidal deformation of the field. We study practical realization of such fields under the use of a few electrodes and a curved mesh (spherical or ellipsoidal mesh). Some variations of the arrangement of electrodes are considered, and simple designs of deceleration lenses with wide acceptance angles of up to 120 degrees are obtained. Here fine focusing of wide-angle beams can be achieved in a three-electrode deceleration lens with an ellipsoidal mesh.

KVI Lamb-shift polarimeter

The design and operation of a Lamb-shift polarimeter is discussed. This polarimeter is used to measure the polarization of proton and deuteron beams extracted from the KVI polarized-ion source. The major components of the Lamb-shift polarimeter (LSP) are described in some detail. These include the deceleration lens system, cesium neutralization oven, spin filter, metastable-atom detection system, and the solenoid. Typical operating parameters of the LSP will be given together with some representative spin-polarization measurements. The design criterion of measuring the polarization of a H+ or D+ beam within 60 s and with a statistical uncertainty smaller than 2% has been met.

Improved abundance sensitivity in MC-ICP-MS for determination of236U/238U isotope ratios in the 10−7to 10−8range

A multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS)—Nu Plasma HR—equipped with an ion deceleration filter (‘high abundance sensitivity channel’) was optimized for the determination of extremely low uranium isotope ratios and applied for the first time for the analysis of 236U/238U isotope ratios in the 10−8 to 10−7 range in isotopic reference material IRMM-184, as well as in two unknown samples obtained in the frame of a round-robin exercise. The application of the ion deceleration lens system in the Nu Plasma ICP-MS allowed a reduction of peak tailing from 238U+ ions at m/z = 236 down to 3 × 10−9, whereas the absolute sensitivity for uranium was reduced by only about 30%. Thus, abundance sensitivity was improved by almost two orders of magnitude and the minimum determinable 236U/238U ratio was improved by more than one order of magnitude compared with conventional sector-field ICP-MS or TIMS. However, interference by 235U1H+ ions deteriorated the accuracy and increased the measurement uncertainty up to 48%, in particular in the case of samples enriched in 235U. Deviation of the measured value from the certified ones varied from −24% to 17.7% but was within the measurement uncertainty.

Preparative Separation of Mixtures by Mass Spectrometry

A specially designed mass spectrometer which allows for preparative separation of mixtures is described. This mass spectrometer allows for large ion currents, on the order of nanoamperes, to be produced by electrospray and transmitted into a high vacuum. Accumulation of nanomole quantities of collected and recovered material in several hours is demonstrated. The use of high-velocity ions reduces space charge effects at high ion currents. Separation of mass occurs simultaneously for all ions, providing a 100% duty cycle. The use of a linear dispersion magnet avoids compression at higher m/z ratios. A deceleration lens slows the ions to allow for soft landing at low kinetic energy. The ions are neutralized by ion pairing on an oxidized metal surface. Retractable landing plates allow for easy removal of the separated components.

Ion/Molecule Reactions of Silver Cluster Cations with Crown Ethers in a Cylindrical Ion Trap

For observing gas-phase ion/molecule reactions of metal cluster cations, a cylindrical ion trap time-of-flight mass spectrometer was newly constructed. This apparatus consists of an external sputtering ion source, ion deceleration lens system, cylindrical ion trap and time-of-flight mass analyzer with four toroidal electric sectors. Using this apparatus, ion/molecule reactions of silver cluster cation, Ag5+, with crown ether, 12-crown-4 (12C4), were observed. The cluster-ligand complexes, [Ag5(12C4)n]+ (n=1–3) and fragmentations of the cluster induced by adducts of crown ether molecules were also observed.

Minimization of dry etch damage in III-V semiconductors

Dry etch damage is a potential worry when etching III-Vsemiconductors. Even though very low levels of damage are possible in moderndry etch processes, it is nevertheless of interest to be able to detect anyresidual damage and understand its origins. We have used measurements ofphotoluminescence intensity from GaAs and InGaAs quantum well heterostructuresto probe the damage in a non-invasive way. At low damage levels, two factorsinfluencing possible damage penetration have been found: the ratio of atomicto molecular ions in the discharge and the effect of ambient light. Sampleswere etched using SiCl4 reactive ion etching and also a more complexmulti-component discharge. Comparative studies were made on samples bombardedby the separate constituent ions of a SiCl4 discharge using amass-resolving ion implanter fitted with a deceleration lens. The experimentsshow that molecular ions contribute less to deep damage than do atomic ions.This is relevant, for example, if using high pump powers to sustain thedischarge, such as in ICP or ECR. Further studies of laser illumination on thesample during etching show that a form of radiation enhanced diffusion canmodify the damage distribution. This is relevant, for example, if laserinterferometry is used for end-point detection. Thus for low damage inlow damage etch processes, etch parameters that minimize atomic ion content inthe discharge should be used and ambient illumination should be avoided ifpossible.