Duoplasmatron Type Ion Source Research Articles

Analysis of Ion-Species of a Dedicated Duoplasmatron-type Ion Source for a 100 keV-Rage Compact Ion-Microbeam System

Hydrogen-ion beam species generated by a dedicated duoplasmatron-type ion source that was developed for a MeV compact ion-microbeam system was experimentally analyzed in a test bench to study the ion source feature. Bimolecular and trimolecular hydrogen-ion beams were mainly generated by the duoplasmatron-type ion source. The ratio of the two different molecular hydrogen-ion beams was controlled by turning hydrogen-gas pressure. This experiment showed that the duoplasmatron-type ion source could produce a single molecular hydrogen-ion beam for ion-microbeam applications.

Reduction of a beam diameter by decreasing the divergence angle of an incident beam in a compact ion microbeam system producing several-hundred-keV beam

A compact ion microbeam system, which comprises a three-stage acceleration lens and a duoplasmatron-type ion source and produces beam of several hundred kiloelectron-volts, has been developed to form a beam that has a diameter of several micrometers. Previous studies have indicated that a small divergence angle of an incident beam is required to improve the demagnification of the three-stage acceleration lens. A simulation of an ion beam extraction demonstrated that the optimum distance between the anode and the extraction electrode in the ion source could lead to an ion beam being generated with the smallest possible divergence angle. As a result, a hydrogen beam with a 2.6μm diameter was experimentally produced at 120keV.

Decrease in the operating gas pressure in an ion source

The results of use of a cold hollow cathode with a multipole magnetic field in a duoplasmatron-type ion source are described. The operating parameters of a duoplasmatron with the developed cathode and a duoplasmatron with a cold hollow two-cylinder cathode are compared. It is shown that the use of a cathode with a multipole magnetic field offers additional possibilities of reducing the operating gas pressure in an ion source and contributes to an increase in both the current and the phase density of the ion-beam current at the output of a charged-particle source and to a decrease in the phase volume of this beam.

Test results of the proton injector of the Proton Engineering Frontier Project accelerator

One of the goals of the Proton Engineering Frontier Project (PEFP) is to develop a 100 MeV proton accelerator. As a low energy part, a 20 MeV proton linac has been developed and tested. The 20 MeV accelerator consists of a 50 keV proton injector, a 3 MeV radio frequency quadrupole, and a 20 MeV drift tube linac. The proton injector includes a duoplasmatron type ion source and a low energy beam transport. After a preliminary test with 1 mA peak current of the 20 MeV accelerator, the proton injector was modified with the goal of increasing the 20 MeV beam current up to 20 mA peak value. The modifications include the reduction of the proton injector length, installation of a beam current monitor, and electron trap and supplement of the solenoid and steering magnets. In this paper, the modifications of the PEFP proton injector are described and initial test results are presented.

Progress in submicron width ion beam system using double acceleration lenses

The submicron ion beam system has been developed for formation of tens keV H 2 + beam with 0.1 μm width using a duoplasmatron-type ion source and an acceleration lens system. The 33 keV H 2 + beam of 0.28 μm in width was obtained using plasma sheath acceleration in our previous study. In this study, the parallel ion beam extraction was newly introduced using the non-magnetic anode with a hole tapered with Pierce angle to minimize the beam divergence angle in the ion source without the plasma sheath acceleration. The 46 keV H 2 + beam of 0.16 H 2 + in width was obtained by this improvement.

Development of a sub-micron ion beam system in the keV range

The sub-micron ion beam system has been developed using the duoplasmatron-type ion source and special lenses with the double functions of the beam focusing and acceleration. The beam width was about 0.43 μm for about 30 keV hydrogen ions, though the value was slightly larger than the one estimated from the beam transport calculation. The slow drifting of the beam spot position within 0.4 μm was observed during the experimental time of about 10 min. The improvements by means of introducing the beam injection system enabled us to achieve the beam width of 0.28 μm and a slight drift of the beam spot within 0.3 μm .

Ion sources for linac of Moscow Institute for Nuclear Research

Ion sources for 600 MeV linac of Moscow INR are described. It is possible to accelerate in the linac intense unpolarized and polarized proton and negative hydrogen ion beams with average current up to 0.5 mA. The unpolarized proton beam is produced by a duoplasmatron type ion source. After acceleration to 750 keV, a beam with peak current 120 mA within normalized phase space area 0.15 π cm mrad is obtained. The surface-plasma H− ion source operating in noiseless mode produces pulsed H− beam with current 80 mA. Polarized proton beam with peak current 6 mA and polarization 80% is generated by the atomic beam-type polarized proton source.

A 400 keV ion accelerator for surface study

A 400 keV static ion accelerator is designed to fulfill the requirements on the ion beam quality arising from medium energy ion scattering (MEIS) experiments. The normalized emittance of the modified duoplasmatron type ion source is 0.35 mm mrad MeV 1 2 for a H + ion beam, obtaining a beam current of 60 μA. A rotating disk high voltage generator DISKTRON, developed in ULVAC Corp., is working satisfactorily. The maximum output power of the generator is 1 mA at 400 kV and the voltage stability is of the order of 10 −4. A voltage regulator with a feedback circuit keeps the output voltage at desired values even against to ± 10% change of load current. The total system of the ion accelerator, the output beam quality and the toroidal electrostatic energy analyser in the ultra high vacuum chamber are described.

Neutron Generator with a Self-Target Using D-T Reactions

A mixture of deuterium and tritium ions from a high yield modified Duoplasmatron type ion source was accelerated up to 200 KeV and the yield of 14 MeV neutrons on a stainless steel target with a galvanized Ni layer, on which Ti was evaporated, was measured. The Neutron yield per unit current obtained by this method was lower by a factor of about 15 than that obtained by accelerating a D+ beam on a tritium impregnated target, but because there was no limitation on the beam current, imposed by the life of targets, a neutron yield of 2×1011 n/s was obtained. Since the neutron yield at this energy range varies as fourth power of the accelerating voltage, it can be expected to obtain much more neutrons for higher accelerating voltages.

Dynamag Ion Source with Open Cylindrical Extractor

A description is given of a duoplasmatron type ion source which features a novel, open cylindrical extractor electrode, a visible arc chamber and a short-path magnetic circuit. The glass spacer in the arc chamber permits observation of the plasma and filaments. The short magnetic circuit gives high plasma density at low magnet and arc currents. The open extraction geometry provides high pumping speed to the source and reasonable tolerances for anode alignment. Above a critical value of extraction voltage the ion emission is independent of voltage. At 16 kV, a 5 mA beam of mixed hydrogen ions can be obtained through an 0.008 in. anode aperture. Gas consumption is about 5 atm.-cc/ hr. with a conversion efficiency of about 70%. Proton yield is usually better than 50% of the total beam current under these conditions. The emittance (phase space area) is about 3 mrad.-cm. MeV? at 1.0 mA.

Pulse Shortening in the Duoplasmatron Type Ion Source

An arc pulsing method is widely used to obtain high intensity pulsed ion beams from the Duoplasmatron type ion source. In this method, it is found that anode current and, therefore, ion current pulse widths are smaller than voltage pulse width applied to the cathode. Factors affecting pulse shortening, such as gas pressure in discharge region, applied voltage, etc., have been investigated. Pulse shortening in ion beam current may be caused by the formation of the semispherical-shaped double electric layer, which focuses and accelerates electrons in plasma, near the cathode side of the capillary of the intermediate electrode.

Some Properties of a Duoplasmatron Ion Source

The ion flux density from the anode cup of a duoplasmatron type ion source was measured under the same conditions as the source operation with a special double probe. The ion flux density of 2.64×1018n/cm2 sec was obtained at the source pressure of 460μ. Torr., the arc current of 1.0 amp. and the magnetic field strength of 1100 gauss. The ion flux density is almost proportional to the arc current, the area of the anode aperture and the magnetic field strength in the region below 2000 gauss. Above this region of the magnetic field the saturation effect was observed. The ion flux density has a maximum value at the source pressure of about 200μ Torr. and decreases quickly at higher pressure side, but slightly at lower pressure side.