Penning-type Ion Source Research Articles

PENNING-TYPE H– ION SOURCE WITH METAL HYDRIDE CATHODE IN PULSATING REGIME

The features of H– ion emission from gas-feed-free Penning-type ion source with metal hydride cathode have been studied in pulsating regime. The metal hydride cathode provided local injection of hydrogen in activated state and impacts on Penning discharge ability to emit H– ions in the longitudinal direction. For stimulation of pre-excited hydrogen desorption from metal hydride the voltage pulse (4.5 kV, τ ≈ 15 µs) was performed against the background constant voltage of 6 kV on the anode of the discharge. The H– ion current of about 0.2 mA was obtained.

The emission of H− ions from Penning-type ion source with metal hydride cathode in pulsating regime

The operation in pulsating regime of gas-feed-free Penning-type H− ion source with metal hydride cathode and extraction in the longitudinal direction has been investigated. Hydrogen is stored in metal hydride in atomic state followed by the formation of rovibrationally excited H2* molecules due to the process of nonequilibrium desorption. It impacts on a Penning discharge ability to emit negative hydrogen ions in the longitudinal direction and provides local gas injection to the discharge without any external gas supply. The AC power input of 65 W during τ≈15 μs was performed against the background DC one of 5 W. The extracted axial flux of charged particles was separated in an electromagnetic filter followed by the registration of H− current. The H− ion current of about 0.22 mA was obtained. In the DC regime it was only 5uA, which is order of magnitude below the current obtained with the present pulsating regime of source implementation.

System for Measuring Emittance Characteristics of Ion Sources

The article presents the results of the development of a system for measuring emittance characteristics of ion sources studied at the IAP NAS of Ukraine with the aim of obtaining the ion beams with a high brightness. The emittance measurement system is based on the scheme of an electrostatic scanner and consists of two main parts: the scanner, which moves in the direction perpendicular to the beam axis using a stepper motor, and the electronic system of control, processing and data acquisition. The electronic system contains a Raspberry pi 3B microcomputer, precision DAC/ADCs, the high-voltage amplifier of a scanning voltage up to ±500 V on deflection plates of the scanner and a wide range current integrator. The determination of the emittance consists in measuring the ion beam intensity distribution when the scanner moves along the x-coordinate and the electrostatic scanning along the x´ angle. The obtained two-dimensional data array allows determining the main characteristics of ion beam: geometric 90% emittance, the root mean square (rms) emittance, the Twiss parameters and phase ellipse of rms emittance, the beam current profile and the angle current density distribution. To test the performance and functionality of the system, the emittance characteristics of the penning type ion source were measured. The working gas was helium, and the beam energy varied within 7–15 keV. At 13 keV of beam energy the following emittances of the He+ ions beam was obtained: 90% emittance is 30 π∙mm∙mrad, rms emittance is 8.4 mm∙mrad, and the normalized rms emittance is equal to 0.022 mm∙mrad. The developed system for measuring the emittance of the ion beams is characterized by a short measurement time of 10-15 minutes.

The increasing of H−current from Penning ion source with electrically biased metal hydride cathode

The possibility of the current increasing of negative hydrogen ions H− extracted in the longitudinal direction from gas-feed-free Penning type ion source with metal hydride cathode by the electric cathodes bias has been investigated. The separation of negative ions from the extracted flux of charged particles was performed by an electromagnetic filter, which consists of a magnetic coil for electron diverting and a grid under positive potential for positive ion reflection. The optimum for the effective extraction of H− ions has been determined. The H− ion current of 10 μA was obtained at an input power of 6 W.

Simulation and optimization of a negative hydrogen Penning ion source

The results of a Particle-In-Cell Monte-Carlo Collision simulation of a cold cathode Penning type ion source are presented. The source is designed to generate H− ions through the volume production process. Twenty-one important processes including electron and heavy particle collisions are introduced into the simulation. The main focus was the energy distribution of electrons which has a large effect on the H− production rate in the volume production. The dependence of the energy distribution of electrons on the axial magnetic field was investigated. The large sensitivity of the H− production rate to the energy distribution of electrons was measured. It was observed that for an anode with a 5 mm radius increasing the axial magnetic field in the range of 0.5–1.1 T results in the increase in the H− density almost by a factor of 14. In addition, it was found that the anode with a radius of 5 mm was the most efficient anode in H− production among the anodes with radii from 3 to 6 mm.

Measurement of the atomic ion fraction of ion emitted from a miniature penning ion source

Penning-type ion source performance for neutron generator applications is characterized partly by the atomic ion fraction, providing one path by which source performance can be improved for increased neutron yields. A miniature penning ion source has been fabricated to investigate the atomic ion fraction of deuterium plasma by a mass-energy analyzer. The discharge current and atomic ion fraction increase with the increase of anode voltage and pressure. Effects of electrode materials on discharge characteristics have been studied. The atomic ion fraction could increase about 2% of the original atomic fraction by Au cathode instead of steel cathode, and it could increase about 1% of the original atomic fraction by Al cathode. The results can provide useful information for improving source performance by selecting more suitable anode voltage, pressure and electrode material.

ULTRA-LOW INTENSITY PROTON BEAMS FOR RADIATION RESPONSE RELATED EXPERIMENTS AT THE U-120M CYCLOTRON

The U-120M cyclotron at the Nuclear Physics Institute (NPI) of the Czech Academy of Sciences in Rez is used for radiation hardness tests of electronics for high-energy physics experiments. These tests are usually carried out with proton fluxes of the order of 10<sup>5</sup>–10<sup>9</sup> proton·cm<sup>−2</sup>·s<sup>−1</sup>. Some tests done for the upgrade of the Inner Tracking System of the ALICE experiment at CERN, however, required proton beam intensities several orders of magnitude lower. This paper presents a method which has been developed to achieve the proton beam flux of the order of 1 proton · cm<sup>−2</sup>·s<sup>−1</sup>. The method is mainly based on reduction of the discharge current in the cyclotron internal Penning type ion source. Influence of this new operation mode on the lifetime of ion source cathodes is discussed.

Investigation on Operating Parameters of the Homemade Penning-Type Ion Source for Cyclotron

A Penning-type ion source for a cyclotron producing PET radioisotopes has been made. To determine the performance of the ion source for further developments, an investigation on the operating parameters has been conducted. The investigation was carried out by experiments on an ion source test device. The investigated operating parameters were the puller voltage, the magnetic field, the hydrogen gas flow rate, and the cathode current. The results showed that the puller voltage was the most sensitive parameter to change ion beam current, and at a voltage of 8 kV an ion beam current of 35 µA was obtained. The puller voltage is still likely to be raised if the current beam is to be increased. Increasing the magnetic field beyond approximately 450 gauss caused the ion beam to saturate. It was obtained that a moderate range of gas flow rate on the value of 5-10 cc/min, producing a high beam current with no significant effect to decrease a vacuum level . Cathode current magnitudes of up to 1 mA significantly affect the beam current, while above this value the beam current tends to be constant Received: 04 October 2014 ; Revised: 28 April 2015; Accepted: 05May 2015

ISHN Ion Source Control System. First Steps Toward an EPICS Based ESS-Bilbao Accelerator Control System

ISHN (Ion Source Hydrogen Negative) consists of a Penning type ion source in operation at ESS-Bilbao facilities. From the control point of view, this source is representative of the first steps and decisions taken towards the general control architecture of the whole accelerator to be built. The ISHN main control system is based on a PXI architecture, under a real-time controller which is programmed using LabVIEW. This system, with additional elements, is connected to the general control system. The whole system is based on EPICS for the control network, and the modularization of the communication layers of the accelerator plays an important role in the proposed control architecture.

Development of hollow anode penning ion source for laboratory application

The research work presented here focuses for the development of miniature penning type ion source. One hollow anode penning type ion source was developed in our laboratory. The size of the ion source is 38 mm diameter and 55 mm length. The ion source consists of two cathodes, a hollow anode and one piece of rare earth permanent magnet. The plasma was created in the plasma region between cathodes and the hollow anode. The J × B force in the region helps for efficient ionization of the gas even in the high vacuum region∼1×10 −5 Torr. The ions were extracted in the axial direction with help of the potential difference between the electrodes and the geometry of the extraction angle. The effect of the extraction electrode geometry for efficient extraction of the ions from the plasma region was examined. This ion source is a self extracted ion source. The self extracted phenomena reduce the cost and the size of the ion source. The extracted ion current was measured by a graphite probe. An ion current of more than 200 μA was observed at the probe placed 70 mm apart from the extraction electrode. In this paper, the structure of the ion source, effect of operating pressure, potential difference and the magnetic field on the extracted ion current is reported.

Influence of magnetic field on the electric breakdown in penning ion source

A cold-cathode penning-type ion source has been developed in our laboratory to study the electric breakdown in this type of sources. The breakdown voltage was measured as a function of axial magnetic field, in the range of 440-600 G, and anode length, in steps of 14, 20, and 24 mm. The measurement was performed with stainless steel cathodes in argon gas at pressure of 4 × 10(-2) mbar. Furthermore, a model was developed to explain the breakdown voltage data. In the construction of the model, the first Townsend coefficient was not directly used to avoid difficulties originating from the non-uniformity of the electric field. The empirical parameters of the model were obtained using the experimental data. The equation γ = c × (E(z)/N)(n), expressing the effective secondary emission coefficient in terms of reduced electric field, which was needed in the modeling process, was inspired from previous works. The parameters c and n were then calculated from the empirical parameters of the model. The n parameter turned out to be 0.59, which differs from the value reported by other authors merely by 1.6%. Three values, 0.010, 0.013, and 0.017 corresponding to the three anodes were obtained for the c parameter. These numbers are in good agreement with 0.01, which has been reported in the previous works. It was also found that the value of n has a decisive impact on the breakdown voltage curve in the high breakdown voltage region.

Development of compact size penning ion source for compact neutron generator

For long-life operation, easy to mount and compact in size penning type ion sources are widely used in different fields of research such as neutron generators, material research, and surface etching. One penning type ion source has been developed in our laboratory. Applying high voltage of 2 kV between two oppositely biased electrodes and using permanent magnet of 500 gauss magnetic field along the axis, we had produced the glow discharge in the plasma region. The performance of this source was investigated using nitrogen gas. Deuterium ions were produced and extracted on the basis of chosen electrodes and the angle of extraction. Using a single aperture plasma electrode, the beam was extracted along the axial direction. The geometry of plasma electrode is an important factor for the efficient extraction of the ions from the plasma ion source. The extracted ion current depends upon the shape of the plasma meniscus. A concave shaped plasma meniscus produces converged ion beam. The convergence of extracted ions is related to the extraction electrode angle. The greater the angle, the more the beam converges. We had studied experimentally this effect with a compact size penning ion source. The detailed comparison among the different extraction geometry and different electrode angle are discussed in this paper.

The APΓO-2 technological facility for ion-beam-assisted deposition

The APΓO-2 technological facility for ion-beam-assisted deposition is described. This facility is used to obtain composite coatings under bombardment by gas ions with energies of several tens of keV. The design features of the Penning-type ion source and the double-arm electron-beam evaporator are presented.

The nuclear microprobe at the University of Arizona

A nuclear microprobe has been operational at the University of Arizona since early 1994. It utilizes a magnetic quadrupole doublet (model QL-300 from Microscope Associates, Inc.) with an 11 mm diameter aperture and lens lengths of 6 cm each. The magnetic pole tips are electrically insulated to enable electric rotational alignment and beam rastering by application of varying voltages to the pole tips. Ion beams are obtained from a 5.5 MV model CN, High Voltage Engineering Corp. Van de Graaff accelerator with a Penning type ion source. Present mininum beam spot size is about 2 μm obtained with a 4 MeV H 2 + beam with a current of about 40 pA. To date, the instrument has been successfully used to map concentrations of Hg, Cr, and As in rabbit renal slices using PIXE.

A multipurpose implanter with various target chambers for basic studies on the influence of ion bombardment on material properties

A multipurpose apparatus with several exchangeable target chambers for implantation of gaseous and metal ions into various target materials is described. An ion beam from a Penning-type ion source with energies between 20 and 120 keV is mass-analyzed with a sector magnet and directed into a primary target chamber with target holders for flat and rotating cylindrical samples. In addition to this chamber several exchangeable chambers can be brought into the beam line. They serve for irradiation of large area targets, under various angles with a goniometer, in situ Mössbauer spectroscopy, ion beam assisted vapour deposition or powder irradiation.

IBA using a small tandem and a single-ended Van de Graaff

Using an NEC 5SDH-2 tandem and an upgraded KN-4000 single-ended Van de Graaff machine we are investigating the depth profiles of 1,2H, 4He and 6,7Li which have been implanted or dispersed into silicon wafers, SiO2/Si, SiO2/magnetic bubble garnet, soda-lime glass and stainless steel. The tandem is used to generate an 8 MeV 16O beam for ERD measurements of these light elements and also a 15N4+ beam for profiling hydrogen by means of the 1H(15N, αγ)12C reaction. The Van de Graaff has a maximum terminal voltage of 4.75 MV and accelerates 15N2+ ions for 1H profiling and 3He+ ions for highly sensitive 2H measurements by means of the 2H(3He, pα) reaction. An RBS investigation is running instead of PIXE experiments which have been terminated some years ago. We are using two types of homemade cold-cathode Penning-type ion source (PIG). The one has a side-extraction design for the tandem, and the other is an end-extraction source for the Van de Graaff. Owing to very low gas consumption, both sources are suitable for generation of ions of expensive isotopes such as 3He and 15N. We will report the experience with IBA using both types of electrostatic machines.

A Penning-type ion source with an expansion cup for impact processes

An ion source designed to perform ion-impact studies in the energy range up to 10 keV is described. It is a magnetically confined, oscillating electron-bombardment type with a cold cathode and expansion cup. It gives a helium ion current of approximately 150 mu A at normal operating conditions (V/sub d/=1.8 kV, V/sub e/=5 kV, and magnetic field=80 G). Measurements have been carried out to find the influence of pressure, discharge voltage, magnetic field, and extracting voltage on the ion-source properties. The ion beam is significantly increased with discharge voltage up to approximately 310 mu A for V/sub d/ approximately=3 kV. However, it is less affected with extracting voltage. At low pressure, the beam is influenced by the magnetic field to give a current increase of 30 mu A through the magnetic range up to 135 G, while it is almost unaffected by the magnetic field at high pressure. It showed an energy spread of 32 eV at a discharge voltage of 1.8 kV and an extraction voltage of 2 kV.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A penning type ion source with high efficiency and some applications

Abstract A Penning type ion source has been developed for the application in definite sputtering experiments and surface etching. The source produces ion currents up to 200μA for energies between 2.5 and 50keV. By electrostatic ion optics the beam diameter can be varied From 0.3 to 20 mm by changing the focusing conditions. The distributions of intensity and energy will be discussed for different beam parameters. Some examples of different surface topographies generated by ion bombardment of single crystals of Pb, Ag and Al using this ion source are demonstrated.

Operation and Life of the Zetatron: A Small Neutron Generator for Borehole Logging

The zetatron is a small sealed-off D-T accelerator being used for pulsed neutron production in Uranium borehole logging experiments. The tube utilizes a zirconium gas reservoir, Penning type ion source, and up to 130 kV ion extraction with ion beam focussing and secondary electron supression. The mixed D-T beam is incident on a scandium film target and produces in the pulse mode up to 8 × 106 neutrons/sec peak rate at a source current of 2.5 A and target voltage of 130 kV. In the borehole logging application the tube, operating at 100 pps, dissipates an average power of about 10 watts. Life testing has demonstrated an average tube functional life of 148 hours and a shelf life in excess of one year. Life limitations include a steady degradation in neutron output of about 50% in 100 hours and eventual tube puncture fractures that are catastrophic.

A Cold-cathode ion source for mass spectrometry

A small Penning-type ion source with an ion-current-neutral conversion sensitivity of 2 × 10 −2 A torr −1 has been constructed. Ion extraction is by way of a channel in one magnet pole face where a retarding-potential plot has shown that 95% of the ions have an energy less than 100 eV. The source is utilized with a high-energy ion stop and a quadrupole mass filter with an out-of-line-of-sight ion collector.