Cold Cathode Penning Ion Source Research Articles

Electric field design of cold cathode Penning ion source for miniaturization neutron tube

It is of great significance to study the optimum electric field strength of cold cathode Penning ion source (PIG), which is used on high yield neutron tube. The electric field in the ion source depends largely on the relationship between the voltage of anode and the thickness of anticathode. In the case of constant magnetic strength, the discharge modes of PIG can be distinguished by the relation between electric potential and pressure. Based on this relationship, we re-designed and optimized the PIG, and got the expected discharge mode. COMSOL was used to simulate the model, and a better extracted beam intensity (10.31μA) and a higher proton fraction (24 %) were obtained at an extracted voltage of −80 kV. It is estimated that the yield is higher under −80 kV than the previous design, which can reach 6×108n/s. This study can provide reference for the development of high yield neutron tube ion sources.

The magnetic field design of a solenoid for the cold-cathode Penning ion source of a miniature neutron tube

A high-yield and beam-stable neutron tube can be applied in many fields. It is of great significance to the optimal external magnetic field intensity of the cold-cathode Penning ion source (PIS) and precisely controls the movement of deuterium (D), tritium (T) ions and electrons in the source of the neutron tubes. A cold-cathode PIS is designed based on the solenoidal magnetic field to obtain better uniformity of the magnetic field and higher yield of the neutron tube. The degree of magnetic field uniformity among the magnetic block, double magnetic rings and solenoidal ion sources is compared using finite element simulation methods. Using drift diffusion approximation and a magnetic field coupling method, the plasma distribution of hydrogen and the relationship between plasma density and magnetic field intensity at 0.06 Pa pressure and a solenoid magnetic field are obtained. The results show that the solenoidal ion source has the most uniform magnetic field distribution. The optimum magnetic field strength of about 0.1 T is obtained in the ion source at an excitation voltage of 1 V. The maximum average number density of monatomic hydrogen ions (H+) is 1 × 108 m−3, and an ion-beam current of about 14.51 μA is formed under the −5000 V extraction field. The study of the solenoidal magnetic field contributes to the understanding of the particle dynamics within the PIS and provides a reference for the further improvement of the source performance of the neutron tube in the future.

Experimental characterization of the internal ion source for the AMIT compact cyclotron

The ion source is one of the most relevant elements in a cyclotron, since it determines the injection into the accelerator. An internal cold-cathode Penning ion source has been chosen for the AMIT compact cyclotron. This kind of source is extensively used in cyclotrons to produce negative hydrogen ions. The compactness of the accelerator constrain the beam diagnostic in the cyclotron, motivating the development of an external experimental facility for the commissioning of the ion source. In this paper, the validation of the ion source design and the characterization of the H− beam production are presented. Different chimney geometries modifying the distance between the plasma column and the extraction wall have been tested to obtain the best relation between ion production and plasma conditions. In addition, experimental measurements of the beam profile have been carried out. Current experimental results provide relevant information for the operation in the final cyclotron assembly and the final beam current optimization.

Dependence of emittance of the He+ beam extracted from a Penning ion source on the design of the source, a Particle-In-Cell simulation.

The dependence of the emittance of He+ beam extracted from a cold cathode Penning ion source on source discharge voltage, anode length, and cathode to anode distance was studied. The 2D3V particle-in-cell Monte Carlo simulation technique was utilized to perform the analysis. Different dimensions for components of the ion source such as anode length and cathode to anode distance were considered. The increase in the cathode to anode distance led to a reduction in rms emittance, almost independent of discharge voltage. This study indicated that the rms emittance slightly improves on increasing the anode length.

Improved gating device of time-of-flight ion mass analyzer for ion sources.

A gating device is a critical component in a time-of-flight (TOF) ion mass analyzer for identifying ion species extracted from ion sources according to their mass-to-charge ratio. It consists of several concentric ring electrodes to deflect as many ions as possible within a very short gate time, thus increasing the ion current collected in a Faraday cup. In this study, we further improve the ion collection efficiency of the gating device by minimizing potential distortion along the paths of ions, by modifying the structure of gate electrodes and applying a bipolar gate pulse on them. Using the improved gating device, we find that the ion beam current increased by nearly 50% compared to the conventional one without changing the noise level. The improved TOF system is well applied to identify the spectrum of ion species extracted from a cold cathode Penning ion source, depending on the operating conditions.

Improvement of extracted ion beam from cold cathode Penning ion source

A direct current cold cathode Penning ion source is operated at the optimum parameters and pressure equal to 7×10−4 mmHg using argon gas. It consists of a copper cylindrical hollow anode and two movable molybdenum discs cathodes are placed symmetrically at two ends of the anode. Argon ion beam is extracted from the ion source by using extractor of different aperture diameter equal to 2.5, 3, 3.5, 4 and 4.5mm respectively. The extractor is placed at different distances from the ion exit aperture equal to 5, 10, 15 and 20mm respectively. It is found that at extractor aperture diameter equal to 3.5mm, ion exit aperture - extractor distance equal to 10mm and extraction potential applied on the extractor is equal to −500V, the optimum extracted ion beam current equal to 543 μA can be obtained. A comparison for Penning ion source without and with the extractor is made at the same optimum operating parameters, it is found that the extracted ion beam current from Penning ion source with the extractor increases about twice its initial value of Penning ion source without the extractor.

Study the optimum dimensions and operating parameters of Penning ion source

In this work, design and construction of a DC cold cathode Penning ion source is described. It consists of cylindrical hollow anode and two movable disc cathodes that are placed symmetrically at two ends of the anode. The electrical discharge and the output ion beam characteristics of the ion source are measured using argon gas. It is found that the optimum dimensions of anode–cathode distance, ion exit aperture diameter, and ion exit aperture – Faraday cup distance are equal to 8, 1.5, and 30 mm, respectively. The ion source efficiency was calculated at discharge current equal to 1.2 mA, different anode–cathode distances and pressures using argon gas. It is found that at anode–cathode distance equal to 8 mm and pressure equal to 7 × 10−4 mmHg, a maximum ion source efficiency equal to 27.1% can be obtained. The surface hardness of molybdenum specimen is measured after exposure to argon ion beam for two hours at pressure equal to 7 × 10−4 mmHg, discharge voltage equal to 3.5 kV, discharge current equal to 0.6 mA, and output ion beam current equal to 165 μA using argon gas. It is found that the surface hardness of molybdenum specimen is decreased by a factor of 24.2%.

Study the effect of some parameters on the extracted ion beam from cold cathode Penning ion source

ABSTRACTA cold cathode Penning ion source was designed and operated at the optimumconditions. Its characteristics were determined using nitrogen and argon gases atpressure equal to 9×10-4 mmHg. Efficiency of this ion source was determinedusing nitrogen and argon gases. Also, ion source aspect ratio was determinedusing argon gas. The effect of negative voltage applied on Faraday cup usingargon gas was studied. Finally, a simple retarding electrostatic field energyanalyzer has been designed to determine the ion energy distribution.

Characterization of a cold cathode Penning ion source for the implantation of noble gases beneath 2D monolayers on metals: Ions and neutrals

Argon ion kinetic energy spectra at different discharge voltages (between 480 and 600 V) of a commercial cold cathode ion source IQP10/63 are reported. The high kinetic energy cut-off depends on the discharge voltage and the corresponding plasma potential due to excess positive charges which is found to be about 136 V. Exposure of single layer hexagonal boron nitride on rhodium to the beam of the ion source leads to the formation of nanotents, i.e., stable atomic protrusions. A positive bias voltage is applied to the target sample to block the positive ions produced by the ion source. However, application of a positive bias potential (800 eV), which is higher than the kinetic energy cut-off, still allows the formation of nanotents and its observation with scanning tunneling microscopy. This indicates that the ion source also produces neutral atoms with kinetic energies higher than the penetration threshold across a single layer of hexagonal boron nitride.

Dynamical changes of ion current distribution for a Penning discharge source using a Langmuir probe array

A paralleled plate electrode and a 9-tip Langmuir probe array located 1 mm behind the extraction exit of a cold cathode Penning ion source are employed to measure the total current and the dynamical changes of the ion current in the 2D profile, respectively. Operation of the ion source by 500 V DC power supply, the paralleled plate electrode and the Langmuir probe array are driven by a bias voltage ranging from -200 V to 200 V. The dependence of the total current and the dynamical changes of the ion current in the 2D profile are presented at the different bias voltage. The experimental results show that the distribution of ion current is axial symmetry and approximate a unimodal distribution.

Design parameter investigation of a cold-cathode Penning ion source for general laboratory applications

An investigation of different design parameters of a cold-cathode Penning ion source is described. The Penning source had an iron cathode body, samarium cobalt permanent magnet, stainless steel anode and iron cathode faceplate. The faceplate extraction orifice diameter, anode shape and permanent magnet location were adjusted. Discharge current–voltage characteristics and current to a grounded target were measured for the different ion source configurations. Results indicate that for hydrogen and helium operation, the largest orifice, cylinder anode and baseline magnet location provides optimum source operation. Specifically, a continuous positive hydrogen ion target current of 1.0 ± 0.15 mA was attainable at only 1.6 × 10−4 Torr of pressure. At 1.0 mTorr of hydrogen pressure a target current of 2.0 ± 0.15 mA was possible. These results far surpass the design goal of 1 mA hydrogen ion beam at 1 mTorr of pressure. This cold-cathode Penning ion source design has potential application in a wide variety of laboratory research and development projects.

An overview of the ion beam laboratory at Beijing Institute of Physics

A multi-user MeV ion beam system has been installed and has been operating since 1983. It was used for research projects in various areas such as solid state physics, materials science and atomic physics. The operational characteristics and experiences, modifications, and end-station developments are discussed. The system is based on a small 2 × 1.7 MV Tandetron accelerator (General Ionex Corporation, USA) with a negative sputtering ion source and a home-made cold cathode Penning ion source with a charge-exchanger. Ions of almost all elements can be extracted with a large switching magnet to form three small angle beam lines. There are five beam lines installed. A summary of the beam lines that are being constructed for the activities of the laboratory will also be given. These include: Rutherford backscattering spectrometry (RBS), channeling analysis, particle-induced X-ray emission (PIXE), nuclear reaction analysis (NRA), elastic recoil detection analysis (ERDA), high-energy ion implantation (HEII). A proton microprobe, an atomic collision system for various optical measurements, and a cross-beam RBS-implantation end-station coupled with a 200 keV implanter are also installed in the laboratory.

A cold-cathode pig source for high-intensity Li 3+ ion

An internal cold-cathode Penning ion source has been developed at a cyclotron to accelerate Li beams. A block of single-crystal LiF was used for the charge material and located in the anode chamber opposite the slit. The pulsed-mode operation of the arc yielded high currents up to 2.2 μA for Li 3+ ions.

A Rotatable Cold Cathode Penning ion Source

A rotatable cold cathode Penning ion source has been designed and is now operating in the Oak Ridge Isochronous Cyclotron (ORIC). Previous sources for positive heavy ions have been severely limited in life-time by cathode sputtering and buildup of sputtered cathode material. The new ion source extends the cathode lifetime by a factor of ~ 6. The source cathodes are discs of tantalum, 7/8 in. in diameter and 3/8 in. thick. Upon completion of an ion source burn at one position on the circular edge of the cathode discs, each disc is rotated to an unused position for the next burn. Provision exists for continuous rotation of the cathodes. The plasma collimating holes, where the sputtered cathode tantalum is deposited, also are on discs with six possible positions. The new source has resulted in increased accelerated beam currents and greater stability for heavy ions. The source has also been used to produce light ion beams (H, D, ?) over a wide range of intensities.