Refractory rf ovens and sputter probes for electron cyclotron resonance ion source.

Beams from electron cyclotron resonance ion source (ECRIS) with radio frequency ovens for refractory material (using a Mo coil) were recently demonstrated; results for Ti and V are here discussed, with temperature T(s) > or = 2300 K stably maintained and extracted current of about 1000 nA for V(8+) and V(9+). The status of sputter probes is also reported, and the reason why trapping efficiency may be lower than in the oven case are investigated. The simple tubular probe concept show typical currents of Sn(18+) about 250 nA, for the most abundant isotopes, but an operating pressure of about 300 microPa may be required. Some preliminary experiments were performed with Penning probes, showing that transmission of Sn or Pr from Penning cathode to ECRIS plasma is limited. Placement of tin onto anticathode and use of collimator between Penning and ECRIS are also discussed.

Experimental comparison of time-of-flight mass analysis with magnetic mass analysis.

A series of experiments was carried out in which both a magnetic analyzer (mass separator) and a time-of-flight (TOF) spectrometer were used for ion charge/mass spectral analysis of the ion beam formed by a dc Bernas ion source made for semiconductor implantation. The TOF analyzer was a detachable device that provides rapid analysis of charge-to-mass composition of moderate energy ion beams. The magnetic analyzer was a massive device using a 90 degrees -sector bending magnet with radius of the central orbit of 35 cm. Comparison of these two methods for measuring ion beam composition shows good agreement.

Front-end simulation of injector for terawatt accumulator.

A terawatt accumulator (TWAC) accelerator/storage ring complex with the laser ion source is in progress at ITEP. The new injector I4 based on the radio frequency quadrupole (RFQ) and interdigital H-mode (IH) linear accelerator is under construction. The front end of the new TWAC injector consists of a laser ion source, an extraction system, and a low energy beam transport (LEBT). The KOBRA3-INP was used for the simulation and optimization of the ion source extraction system. The optimization parameter is the maximum brightness of the beam generated by the laser ion source. Also the KOBRA3-INP code was used for LEBT investigation. The LEBT based on electrostatic grid lenses is chosen for injector I4. The results of the extraction system and LEBT investigations for ion beam matching with RFQ are presented.

Bernas ion source discharge simulation.

As the technology and applications continue to grow up, the development of plasma and ion sources with clearly specified characteristic is required. Therefore comprehensive numerical studies at the project stage are the key point for ion implantation source manufacturing (especially for low energy implantation). Recently the most commonly encountered numerical approach is the Monte Carlo particle-in-cell (MCPIC) method also known as particle-in-cell method with Monte Carlo collisions. In ITEP the 2D3V numerical code PICSIS-2D realizing MCPIC method was developed in the framework of the joint research program. We present first results of the simulation for several materials interested in semiconductors. These results are compared with experimental data obtained at the ITEP ion source test bench.

Status of ITEP decaborane ion source program.

The joint research and development program is continued to develop steady-state ion source of decaborane beam for ion implantation industry. Both Freeman and Bernas ion sources for decaborane ion beam generation were investigated. Decaborane negative ion beam as well as positive ion beam were generated and delivered to the output of mass separator. Experimental results obtained in ITEP are presented.

Ion sources for energy extremes of ion implantation.

For the past four years a joint research and development effort designed to develop steady state, intense ion sources has been in progress with the ultimate goal to develop ion sources and techniques that meet the two energy extreme range needs of meV and hundreads of eV ion implanters. This endeavor has already resulted in record steady state output currents of high charge state of antimony and phosphorus ions: P(2+) [8.6 pmA (particle milliampere)], P(3+) (1.9 pmA), and P(4+) (0.12 pmA) and 16.2, 7.6, 3.3, and 2.2 pmA of Sb(3+)Sb(4+), Sb(5+), and Sb(6+) respectively. For low energy ion implantation, our efforts involve molecular ions and a novel plasmaless/gasless deceleration method. To date, 1 emA (electrical milliampere) of positive decaborane ions was extracted at 10 keV and smaller currents of negative decaborane ions were also extracted. Additionally, boron current fraction of over 70% was extracted from a Bernas-Calutron ion source, which represents a factor of 3.5 improvement over currently employed ion sources.

Molecular ion sources for low energy semiconductor ion implantation (invited).

Smaller semiconductors require shallow, low energy ion implantation, resulting space charge effects, which reduced beam currents and production rates. To increase production rates, molecular ions are used. Boron and phosphorous (or arsenic) implantation is needed for P-type and N-type semiconductors, respectively. Carborane, which is the most stable molecular boron ion leaves unacceptable carbon residue on extraction grids. A self-cleaning carborane acid compound (C4H12B10O4) was synthesized and utilized in the ITEP Bernas ion source resulting in large carborane ion output, without carbon residue. Pure gaseous processes are desired to enable rapid switch among ion species. Molecular phosphorous was generated by introducing phosphine in dissociators via 4PH3 = P4 + 6H2; generated molecular phosphorous in a pure gaseous process was then injected into the HCEI Calutron-Bernas ion source, from which P4(+) ion beams were extracted. Results from devices and some additional concepts are described.

First experiments with the negative ion source NIO1.

Neutral Beam Injectors (NBIs), which need to be strongly optimized in the perspective of DEMO reactor, request a thorough understanding of the negative ion source used and of the multi-beamlet optics. A relatively compact radio frequency (rf) ion source, named NIO1 (Negative Ion Optimization 1), with 9 beam apertures for a total H(-) current of 130 mA, 60 kV acceleration voltage, was installed at Consorzio RFX, including a high voltage deck and an X-ray shield, to provide a test bench for source optimizations for activities in support to the ITER NBI test facility. NIO1 status and plasma experiments both with air and with hydrogen as filling gas are described. Transition from a weak plasma to an inductively coupled plasma is clearly evident for the former gas and may be triggered by rising the rf power (over 0.5 kW) at low pressure (equal or below 2 Pa). Transition in hydrogen plasma requires more rf power (over 1.5 kW).

Project of electro-cyclotron resonance ion source test-bench for material investigation.

Development of new materials for future energy facilities with higher operating efficiency is a challenging and crucial task. However, full-scale testing of radiation hardness for reactor materials is quite sophisticated and difficult as it requires long session of reactor irradiation; moreover, induced radioactivity considerably complicates further investigation. Ion beam irradiation does not have such a drawback; on the contrary, it has certain advantages. One of them is high speed of defect formation. Therefore, it provides a useful tool for modeling of different radiation damages. Improved understanding of material behavior under high dose irradiation will probably allow to simulate reactor irradiation close to real conditions and to make an adequate estimation of material radiation hardness. Since 2008 in Institute for Theoretical and Experimental Physics, the ion beam irradiation experiments are under development at the heavy ion radio frequency quadrupole linac and very important results are obtained already [T. V. Kulevoy et al., in Proceedings of the International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators, IAEA Vienna, Austria, 2009, http://www.pub.iaea.org/MTCD/publications/PDF/P1433_CD/darasets/papers/ap_p5_07.pdf]. Nevertheless, the new test bench based on electro-cyclotron resonance ion source and high voltage platform is developed. The project of the test bench is presented and discussed.

Gas feeding molecular phosphorous ion source for semiconductor implanters.

Phosphorus is a much used dopant in semiconductor technology. Its vapors represent a rather stable tetratomic molecular compound and are produced from one of the most thermodynamically stable allotropic forms of phosphorus-red phosphorus. At vacuum heating temperatures ranging from 325 °C, red phosphorus evaporates solely as P4 molecules (P4/P2 ∼ 2 × 10(5), P4/P ∼ 10(21)). It is for this reason that red phosphorus is best suited as a source of polyatomic molecular ion beams. The paper reports on experimental research in the generation of polyatomic phosphorus ion beams with an alternative P vapor source for which a gaseous compound of phosphorus with hydrogen - phosphine - is used. The ion source is equipped with a specially designed dissociator in which phosphine heated to temperatures close to 700 °C decomposes into molecular hydrogen and phosphorus (P4) and then the reaction products are delivered through a vapor line to the discharge chamber. Experimental data are presented reflecting the influence of the discharge parameters and temperature of the dissociator heater on the mass-charge state of the ion beam.

Application of the Ta liner technique to produce Ca beams at INFN-Legnaro National Laboratories (INFN-LNL).

The ECR ion sources are able to produce a wide variety of highly charged metallic ion beams thanks to the development of different techniques (ovens, sputtering, direct insertion, metal ions from volatile compounds (MIVOC)). In the case of the ovens, the sticking of the hot vapors on the surface of the plasma chamber leads to high material consumption rates. For elements like Ca, a tantalum liner inserted inside the chamber can be used to limit this phenomenon. The modeling of temperature distribution inside the chamber with and without the liner was carried out with COMSOL-multiphysics code. Results of simulation and the comparison with experiments performed at INFN-Legnaro National Laboratories with Ca beams are discussed.

Development of the ion source for cluster implantation.

Bernas ion source development to meet needs of 100s of electron-volt ion implanters for shallow junction production is in progress in Institute for Theoretical and Experimental Physics. The ion sources provides high intensity ion beam of boron clusters under self-cleaning operation mode. The last progress with ion source operation is presented. The mechanism of self-cleaning procedure is described.

Installation of a versatile multiaperture negative ion source.

Neutral Beam Injectors (NBI), which need to be strongly optimized in the perspective of DEMO reactor, request a thorough understanding of the negative ion source used and of the multi-beamlet optics. A relatively compact RF ion source, named NIO1 (Negative Ion Optimization 1), with 9 beam apertures for a total H(-) current of 130 mA, 60 kV acceleration voltage, is being installed at Padua, in Consorzio RFX, to provide a test bench for source optimizations in the framework of the accompanying activities in support to the ITER NBI test facility. NIO1 construction and status of the overall installation, including a high voltage deck and an optical cavity ring down spectrometer are here summarized and reported. Plasma and low voltage beam operations are discussed. Development of a sampling beam calorimeter (with small sampling holes, and a segmented cooling circuit) is also discussed.

Molecular phosphorus ion source for semiconductor technology.

This paper presents results on the generation of molecular phosphorus ion beams in a hot filament ion source. Solid red phosphorous is evaporated mainly as tetra-atomic molecules up to a temperature of 800°C. Thus, one of the main conditions for producing maximum P(4)(+) fraction in the beam is to keep the temperature of the phosphorous oven, the steam line and the discharge chamber walls no greater than 800°C. The prior version of our ion source was equipped with a discharge chamber cooling system. The modified source ensured a P(4)(+) ion beam current greater than 30% of the total beam current.

Development of a versatile multiaperture negative ion source.

A 60 kV ion source (9 beamlets of 15 mA each of H(-)) and plasma generators are being developed at Consorzio RFX and INFN-LNL, for their versatility in experimental campaigns and for training. Unlike most experimental sources, the design aimed at continuous operation. Magnetic configuration can achieve a minimum ∣B∣ trap, smoothly merged with the extraction filter. Modular design allows for quick substitution and upgrading of parts such as the extraction and postacceleration grids or the electrodes in contact with plasma. Experiments with a radio frequency plasma generator and Faraday cage inside the plasma are also described.

Numerical simulation of gridded electrostatic lens.

Gridded electrostatic lenses are frequently used in extraction systems and low energy ion beam transport line. Typically, for numerical simulation the grid is treated as a metal plate transparent for beam particles. The influence of real grid geometry on the beam dynamics in the gridded lens has been investigated by KOBRA-3d code. Beam emittance growth for different lens parameters has been investigated. Approximating expressions for obtained results are presented. The grid geometry providing minimal beam distortions is proposed.

Rhenium ion beam for implantation into semiconductors.

At the ion source test bench in Institute for Theoretical and Experimental Physics the program of ion source development for semiconductor industry is in progress. In framework of the program the Metal Vapor Vacuum Arc ion source for germanium and rhenium ion beam generation was developed and investigated. It was shown that at special conditions of ion beam implantation it is possible to fabricate not only homogenous layers of rhenium silicides solid solutions but also clusters of this compound with properties of quantum dots. At the present moment the compound is very interesting for semiconductor industry, especially for nanoelectronics and nanophotonics, but there is no very developed technology for production of nanostructures (for example quantum sized structures) with required parameters. The results of materials synthesis and exploration are presented.

First beams from the new electron cyclotron resonance source LEGIS (LEGnaro ecrIS) at INFN-LNL.

From April 2008 the PIAVE injector for the ALPI booster was involved in the upgrade of the high voltage platform housing an electron cyclotron resonance (ECR) source. A 14.5 GHz SUPERNANOGAN type ECR replaced the existing source ALICE; at the same time, the whole platform beam line was redesigned and beam shaping and diagnostic system were installed. The source and the platform were ready to be put into operation in January 2009. PIAVE's commissioning was started from late March and completed in May 2009 using an argon beam. A description of the upgrade will be given in the following; beam quality leading to an improved transmission through the injector will be shown. Results on first gaseous and metallic beams produced will also be given.

Design of a versatile multiaperture negative ion source.

Negative ion sources are a key component of the neutral beam injector to be installed in the International Thermonuclear Experimental Reactor. At present research and development activities address several important issues related to beam extraction, optics, and optimization. Together with the design of real size devices and the accumulation of atomic cross section databases, a relatively small negative ion source [130 mA of H(-) at 60 kV, named Negative Ion Optimization phase 1 (NIO1)] is under construction at Consorzio RFX to contribute to benchmark numerical simulation tools and to test components, such as emittance scanners, beam dumps, and cesium ovens. NIO1 design, magnet configuration, and rf coupling simulations are described.

Boron ion source based on planar magnetron discharge in self-sputtering mode.

An ion source based on a planar magnetron sputtering device with thermally isolated target has been designed and demonstrated. For a boron sputtering target, high target temperature is required because boron has low electrical conductivity at room temperature, increasing with temperature. The target is well-insulated thermally and can be heated by an initial low-current, high-voltage discharge mode. A discharge power of 16 W was adequate to attain the required surface temperature (400 degrees C), followed by transition of the discharge to a high-current, low-voltage mode for which the magnetron enters a self-sputtering operational mode. Beam analysis was performed with a time-of-flight system; the maximum boron ion fraction in the beam is greater than 99%, and the mean boron ion fraction, time-integrated over the whole pulse length, is about 95%. We have plans to make the ion source steady state and test with a bending magnet. This kind of boron ion source could be competitive to conventional boron ion sources that utilize compounds such as BF(3), and could be useful for semiconductor industry application.