External Ion Injection Research Articles

Maintaining the PM Removal Efficiency of a Two-Stage ESP With External Ion-Injection Discharge via a Water Film on the Collection Plate and Cleaning of the Ionizer

A two-stage electrostatic precipitator (ESP) with a reduced footprint, external ion-injection discharge, and water film on the collection plate was developed for long-term operation. For optimal particulate matter (PM) removal efficiency, the ionizer of the external ion injection system was fixed at a distance of 5 mm from the bias plate. Under these operating conditions, the 0.3- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m PM (PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> ) removal efficiency was reduced to approximately 70% due to low migration velocity. The application of an additional collection plate extended the residence time of the charged particles in the electric field, which resulted in a removal efficiency exceeding 95%. However, long-term operation (675 min) of the two-stage ESP with external ion-injected discharge resulted in spark generation due to contamination of the ionizer, and the PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5</sub> and PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> removal efficiencies decreased linearly from 80.4% to 62.2% and 87.7% to 68.2%, respectively. Changing the ionizer to a pin shape with electrical specifications similar to those of carbon fibers resulted in water film formation on the collection plate. The PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5</sub> and PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> removal efficiencies remained at their initial levels for 120 min. The two-stage ESP with external ion-injected discharge operating with a water film is likely suitable for long-term operation in an industrial setting.

Design of target irradiation and diagnostic chamber to study ps-laser generated plasma as a source of singly charged ions for external injection into an electron beam ion source.

High repetition-rate (∼10 kHz) ps-lasers are becoming available on the market with reasonable cost and may offer several advantages compared to ns-lasers by generating nearly continuous beams of singly charged ions appropriate for the "slow" injection mode into the Electron Beam Ion Source (EBIS). To evaluate these advantages, we will perform studies of a ps-laser generated plasma using a laser with a pulse duration of 8 ps and energy up to 5 mJ per pulse. A vacuum chamber equipped with a 3D target positioner, a focusing lens, and a Faraday Cup has been designed and built for this study. Lens-to-target distance variations have been measured using a laser tracker over the whole range of horizontal and vertical translation for all five targets we will use. The variations were found to be within ±150 µm. This degree of "target flatness" should be acceptable for our experimental conditions. Ion currents and ion pulse durations of various elements (from Al to Ta) will be measured for different target irradiation conditions (focal spot size and laser pulse energy). The results obtained will allow us to specify all parameters and geometry of a laser ion source based on a ps-laser to provide external ion injection into the relativistic heavy ion collider EBIS.

Maximized Effective Energy Output of Contact‐Separation‐Triggered Triboelectric Nanogenerators as Limited by Air Breakdown

Recent progress in triboelectric nanogenerators (TENGs) has demonstrated their promising potential as a high‐efficiency mechanical energy harvesting technology, and plenty of effort has been devoted to improving the power output by maximizing the triboelectric surface charge density. However, due to high‐voltage air breakdown, most of the enhanced surface charge density brought by material/surface optimization or external ion injection is not retainable or usable for electricity generation during the operation of contact‐separation‐triggered TENGs. Here, the existence of the air breakdown effect in a contact‐separation mode TENG with a low threshold surface charge density of ≈40–50 µC m−2 is first validated under the high impedance external load, and then followed by the theoretical study of the maximized effective energy output as limited by air breakdown for contact‐separation‐triggered TENGs. The effects of air pressure and gas composition are also studied and propose promising solutions for reducing the air breakdown effect. This research provides a crucial fundamental study for TENG technology and its further development and applications.

Cryogenic linear Paul trap for cold highly charged ion experiments

Storage and cooling of highly charged ions require ultra-high vacuum levels obtainable by means of cryogenic methods. We have developed a linear Paul trap operating at 4 K capable of very long ion storage times of about 30 h. A conservative upper bound of the H(2) partial pressure of about 10(-15) mbar (at 4 K) is obtained from this. External ion injection is possible and optimized optical access for lasers is provided, while exposure to black body radiation is minimized. First results of its operation with atomic and molecular ions are presented. An all-solid state laser system at 313 nm has been set up to provide cold Be(+) ions for sympathetic cooling of highly charged ions.

The MAXEBIS at GSI as a test ion source for charge breeding and for HITRAP

The electron beam ion source MAXEBIS, developed and built at the University of Frankfurt, has been installed at GSI to serve as an offline test ion source for the HITRAP project and for use as a test setup for charge breeding explorations. The setup has been equipped with new diagnostics and beam optics devices. Two ion sources dedicated to the production of singly charged ions for external ion injection into the MAXEBIS have been included. First time of flight (TOF) spectra with external injected, charge-bred argon ions were taken. However, these spectra indicated beam losses in the beam transport from the multipassage spectrometer (MPS) to the MAXEBIS. In order to understand the losses, the beam transport has been simulated with the SIMION code and the beam line has been modified accordingly. Measurements of the MAXEBIS' beam emittance, using the "nondestructive" beam profile method, have been performed as well as measurements of the electron current density via charge state analysis of the TOF spectra. The injection and breeding efficiency of the MAXEBIS have been determined for the first time. The results of the measurements and the planned experiments will be discussed.

Development and Construction of the Al'fa Irradiation Complex for Producing Track Membranes

The Al'fa irradiation complex has been developed and built at the Joint Institute of Nuclear Research. The purpose of this complex is to irradiate polymer films used in the production of track memebranes. The complex contains an isochronous cyclotron with external ion injection, a system for extracting and transporting accelerated ions, and an irradiation setup for the initial material – a polyethylene film. The Al'fa irradiation complex can produce track membranes from polyethyleneterephtalate (lavsan) up to 25 μm thick and up to 40 cm wide.

Measurement of external ion injection and trapping efficiency in the ion trap mass spectrometer and comparison with a predictive model

The efficiency of injecting and trapping ions from an external ion source in a quadrupole ion trap mass spectrometer was measured and compared against a simulation employing a simple hard-sphere collision model. A commercial ion trap mass spectrometer was modified with the addition of a variable energy ion gun, split Faraday cup/electron multiplier detector, and the capability to measure the ion current incident on the ion trap inlet and exit end caps. The entire instrument was modeled using the ion optics simulation program SIMION and user programs were applied in SIMION which modeled the collisions between the injected ions and the helium buffer gas. The model was based on simple hard-sphere collision physics with randomized collision angles and collision probability converging to the mean free path (mfp); the helium buffer gas was assumed to be at rest relative to the injected ions. The measured trapping efficiency of Cs + with helium buffer gas at optimum conditions was 3–5%. The trapping efficiency predicted by the model and the dependence on buffer gas pressure (mfp) agreed with the measured efficiencies within the uncertainties of the model predictions and experimental variance. The fidelity of the simulation was shown to be sensitive to the spatial resolution of the model when predicting the dependence of trapping efficiency on q z. It was concluded that a hard-sphere collision model was adequate for predicting the effects of helium buffer gas pressure on ion injection and trapping within the range of injection energies and buffer gas pressures tested.

Experimental results from the Brookhaven National Laboratory test electron beam ion source

At Brookhaven National Laboratory, an Electron Beam Ion Source (EBIS) is operational and has produced charge states such as N7+, Ar16+, and Xe26+ using neutral gas injection. Ions such as Na7+ and Tl41+ have been produced using external ion injection. The BNL EBIS effort is directed at reaching intensities of interest to RHIC, approximately 3×109 particles/pulse which will require EBIS electron beams on the order of 10 A. Pulsed electron beams up to 1.14 A have been produced using a 3 mm LaB6 cathode. Ion yields corresponding to 50% of the maximum trap capacity for electron beams up to 0.5 A have been obtained. The goal for the TestEBIS is to produce a uranium ion charge state distribution peaked at U45+ with 50% of the trap capacity for a 1 A electron beam.

Simulation of External Ion Injection, Cooling and Extraction Processes with SIMION 6.0 for the Ion Trap/Reflectron Time-of-flight Mass Spectrometer

In this work we have developed a PC-based simulation to study ion injection, cooling and extraction processes for multiple ions in an trap/reflectron time-of-flight (IT/reTOF) system. This simulation is based upon SIMION 6.0 with user written programs in which a 3D collision model is used to describe ion--buffer gas molecule interactions. The results of various simulations describing the relation between the trapping efficiency for external injection of ions into the trap and the RF phase, and the effects of initial kinetic energy and ramp-up rate on dynamic trapping of externally produced ions are discussed. Further, single-pulsing and bipolar-pulsing schemes for ejecting ions from the trap are examined. The simulations show that bipolar pulsing can markedly improve the resolution. In the bipolar ejection mode the relation between resolution and the extraction voltages and RF ramp-off rate are studied.

The BNL EBIS program: status and plains

Recently an Electron Beam Ion Source (EBIS), on long term loan from Sandia National Laboratories, has been put into operation at Brookhaven National Laboratory. This source is being primarily used as a test device to answer questions relevant to the eventual design of an EBIS-based heavy ion preinjector for RHIC; a secondary objective is to determine parameters of an EBIS capable of delivering fully stripped light ions up to neon for medical applications. Such a source can easily produce all ions in charge states as needed, but the challenge lies in reaching intensities of interest to RHIC (2-3 × 109 particles/pulse). The source studies are planned to address issues such as scaling of the electron beam current in stages up to 10 A, possible onset and control of instabilities, external ion injection, parametric studies of the ion yield, charge state distributions and emittance of the extracted ion beam, ion cooling in the trap, and other technical and physics issues.

Development of an electron-beam ion source for a relativistic heavy-ion collider preinjector

At Brookhaven National Laboratory (BNL), an electron-beam ion source (EBIS) is operational as a test bed for development of a high current EBIS for relativistic heavy-ion collider (RHIC). Previously, the goal of most EBIS research has been to produce bare or nearly bare nuclei. At BNL, the EBIS is required to produce only medium charge states of heavy ions, e.g., Au35+, since there is further stripping at higher energies. The BNL effort is directed at reaching intensities of interest to RHIC, approximately 3×109 particles/pulse, which will require an EBIS electron beam on the order of 10 A. Initial tests using a 1 mm LaB6 cathode have produced electron beam currents up to the design value of 110 mA. A 2 mm LaB6 cathode has been installed and in a first run has produced currents up to 350 mA. This source has so far produced charge states up to Ar16+ using neutral gas injection, and up to Tl50+ using external ion injection. Results of these studies and ion injection trials are presented.

Increased ion intensity and reliability of the Stockholm electron beam ion sourcea)

The electron beam ion source, CRYSIS, produces highly charged ions for injection into the heavy ion storage ring—CRYRING at MSL, as well as low energy atomic physics experiments and the Stockholm–Mainz Penning trap recently installed at MSL. CRYSIS has produced ions up to Ar18+ and 136Xe52+. Pulsed beams of Ar13+ ions 60 μs in duration have been injected into CRYRING via an RFQ and ions of charge up to 136Xe44+ have been used in atomic physics experiments with pulse duration 10–250 ms. A vacuum separation of the cryostat and ionization volumes has been made. Temperature control and measurement of internal electrodes have increased the gas injection efficiency and reduced the memory effect associated with a cryogenic EBIS. External ion injection has been added as an alternative to neutral gas injection for introducing the species to be ionized to high charge states. Monitoring of the radio frequency noise signal with a spectrum analyzer has aided in the propagation of quiet, high current (450 mA) dc electron beams. These quiet electron beams have been used to produce extracted ion pulses of higher intensities than in previous operation.

Increased ion intensity and reliability of the Stockholm electron beam ion source (abstract)a)

The electron beam ion source, CRYSIS, produces highly charged ions for injection into the heavy ion storage ring—CRYRING at MSL, as well as low energy atomic physics experiments and the Stockholm–Mainz Penning trap recently installed at MSL. CRYSIS has produced ions up to Ar18+ and 136Xe52+. Pulsed beams of Ar13+ ions 60 μs in duration have been injected into CRYRING via an RFQ and ions of charge up to 136Xe44+ have been used in atomic physics experiments with pulse duration 10–250 ms. A vacuum separation of the cryostat and ionization volumes has been made. Temperature control and measurement of internal electrodes have increased the gas injection efficiency and reduced the memory effect associated with a cryogenic EBIS. External ion injection has been added as an alternative to neutral gas injection for introducing the species to be ionized to high charge states. Monitoring of the radio frequency noise signal with a spectrum analyzer has aided in the propagation of quiet, high current (450 mA) dc electron beams. These quiet electron beams have been used to produce extracted ion pulses of higher intensities than in previous operation.

Computer Simulation of the Operation of a Three-Dimensional Quadrupole Ion Trap

A computer simulation of the motion of ions in a three-dimensional (3-D) quadrupole ion trap has been performed with a Gateway 386 PC/AT computer. The SIMION program was used as the main program to calculate the potential array of the ion trap space. Several user-written programs were interfaced to the SIMION program to simulate the effects of changing various operating conditions, such as the radio-frequency (rf) potential, the collisional buffer gas, external ion injection, dc ejection from the trap, and resonance ejection. With the use of this simulation, the total storage mass range could be obtained as a function of rf voltage and frequency. The simulations show, as expected, that the collisional buffer gas plays an important role in both stabilizing the trajectory of high-kinetic-energy ions (hot ions) inside the ion trap and trapping ions injected from an external source. Several different buffer gases were studied for their effects upon the trapping motion. In addition, both the total mass ejection that results from applying a dc pulse on the output end-cap electrode and the ion ejection that results from applying an rf frequency to the end cap to produce resonance ejection were also studied with this simulation program. It is demonstrated that a simple PC computer using a modified SIMION program provides results very similar to those expected from theory or from previous work.

External ion injection into an electron beam ion source

In this paper we discuss the design, construction and results obtained with an external ion injection system into the Cornell superconducting solenoid, cryogenic electron beam ion source CEBIS II. A small sputter-PIG ion source with cathodes made from the material to be ionized is used as a source of dc currents of singly charged ions which are transported and injected into the ionization region of the EBIS. The injection system uses a 90° electrostatic quadrupole deflector which directs the beam from the sputter-PIG into the electron beam ion source during injection, and acts as an einzel lens during ion extraction from CEBIS II.

Open trapped ion cell geometries for Fourier transform ion cyclotron resonance mass spectrometry

Fourier transform ion cyclotron resonance mass spectrometry is evaluated in trapped ion cells which substitute open rectangular trapping electrodes for trapping plates positioned perpendicular to the magnetic field. Compared with closed cells, the open cell geometry offers improved access to the cell interior with obvious benefits for external ion injection. The well depth along the z-axis centerline of the open cell is about 37% of the applied potential for cubic geometry but increases to 81% for an elongated cell with aspect ratio two. Isopotential field maps are created to compare axial and radial components of trapping and excitation fields for open and closed orthorhombic cells. Radial trapping electric fields are somewhat larger in the center of the open cells but axial excitation fields are a factor of two smaller compared with the closed cell. An open elongated cell with an aspect ratio of two is constructed and compared with a closed cell of similar aspect ratio. Experimentally, a −57 Hz V −1 shift in cyclotron frequency owing to the radial trapping field is obtained for the open cell compared with a −32 Hz V −1 shift for the closed cell. However, axial ejection is significantly reduced in the open cell compared with the closed cell. Suggestions are given for generalizing the open cell to a mutisegmented electrode assembly in which excitation, detection and trapping are performed interchangeably with the same electrodes. For example, capacitive coupling of the excitation potential to the trap electrodes is suggested as a simple means of eliminating axial ejection during excitation.

Fast neutral beam ion source coupled to a Fourier transform ion cyclotron resonance mass spectrometer

The coupling of an autoneutralizing SF−6 fast ion-beam gun to a Fourier transform ion cyclotron resonance (FT/ICR) mass spectrometer is described. The fast neutral beam provides for secondary-ion-type FT/ICR mass analysis [e.g., production of abundant pseudomolecular (M+H)+ ions] of involatile samples without the need for external ion injection, since ions are formed at the entrance to the ICR ion trap. The design, construction, and testing of the hybrid instrument are described. The feasibility of the experiment (for both broadband and high-resolution FT/ICR positive-ion mass spectra) is demonstrated with tetra-butylammonium bromide and a Tylenol■ sample. The ability to analyze high molecular weight polymers with high mass resolution is demonstrated for Teflon■. All of the advantages of the fast neutral beam ion source previously demonstrated with quadrupole mass analysis are preserved, and the additional advantages of FT/ICR mass analysis (e.g., high mass resolving power, ion trapping) are retained.

Status of the Berkeley small cyclotron AMS project

A small, low-energy cyclotron (“cyclotrino”) has been designed and built at Berkeley for direct detection dating of 14C. The system combines the use of a negative ion source to reject 14N with the high resolution of a cyclotron to reject other background ions. In order to allow the dating of old and small samples, the present system incorporates a high-current external ion source and injection beamline. The system is expected to be operational by mid-1988.

Topics in high resolution spectroscopy of stored ions

Recent developments in stored ion spectroscop are discussed with emphasis on the following aspects: (i) Very high resolution experiments. (ii) Precision spectroscopy of one-electron ions. (iii) Measurement of the magnetic moment of the bound electron. (iv) Feasibility of external ion injection to extend ion storage techniques to highly charged and possibly radioactive ions. The question of what can be learned from these experiments about nuclear structure and quantum electrodynamical contributions to the hyperfine interaction and the atomic Zeeman effect is addressed.

External Ion Sources and Injection Lines at the Bonn Isochronous Cyclotron

The complex of external ion source facilities at the Bonn Isochronous Cyclotron is described. A universal ion source of the Penning type was developed for the production of intense beams of multiply charged ions. Details of this ion source and performance figures are presented. An atomic beam polarized ion source is used for the production of polarized protons and deuterons. A modified atomic-beam polarized ion source using a superconducting solenoid ionizer is under construction. For the combined installation of the universal ion source and the polarized ion source a compact beam transport system has been developed which allows the optimum matching with the cyclotron. A buncher with triangular shaped pulses is used in order to increase the beam intensities. Ionoptical and technical details of the external beam lines and the axial injection are presented.