A vertical compact ion implanter for novel applications in biotechnology and gemmology

Abstract

In our efforts in developing ion beam technology for novel applications in biology and gemology, one of the most emphasized research programs in the country, a compact ion accelerator/implanter especially for the purpose was constructed with the support of IAEA under project THA5049-90-02, Establishing an Ion Beam Biotechnology Center to Develop Improved Crops for Agriculture and Horticulture. The designing of the machine was aimed at providing our users with user friendly, convenient and easy operation of a simple accelerator for ion implantation of biological living materials and gemstones for crop mutation and gene transformation inductions as well as for modification of gemstones, which would eventually contribute to the national agriculture, biomedicine and gem-industry developments. For convenient holding irregularly sized and shaped biological and gemological samples which were hard to hold vertically, the machine was in a vertical setup so that the samples could be placed horizontally and even without fixing. For a high beam current and intensity and a simple structure, the machine was a non-mass-analyzing ion implanter using mixed molecular and atomic nitrogen (N) ions so that material modifications could be more effective. For a homogeneous ion implantation, the machine was equipped with a focusing/defocusing lens and an X-Y beam scanner. For fast evacuation and short vacuum exposure to better maintain biological living samples surviving, the target chamber was made relatively small while supported by a powerful pump. To save equipment materials and costs, most of the components of the machine were taken from abandoned ion beam facilities, while the IAEA supported two main power supplies. The total maximum accelerating voltage of the accelerator could be up to 100 kV, which was ideally necessary for crop mutation induction and gem modification by ion beams from our experience. The entire facility consisted of, from the top to the bottom, a modified duoplasmatron ion source, an Einzel lens, a home-made accelerating tube, a small beam diagnosis chamber, an X-Y electrical scanner, and a target chamber. Inside the target chamber there were a sample holder stage and a beam current measurement plate which coordinated a Faraday cup in the beam diagnosis chamber to check the beam current. A stack of power supplies and controllers managed the operation of the facility. The whole system was housed in an appropriately-sized air-conditioned room to reduce the humidity from the tropical environment. The total height of the machine was about 2 meters. The N-ion beam current could be hundreds of μA and the maximum beam spot at the target was 8 cm in diameter. N-ion implantation of local rice seeds and cut gemstones was carried out. Various phenotype changes of grown rice from the ion-implanted seeds and improvements in gemological quality of the ion-bombarded gemstones were observed, demonstrating the IAEA-supported ion accelerator/implanter successfully completed and working satisfactorily. The success in development of such a low-cost and simple-structured ion accelerator/implanter provides developing countries with a model of utilizing our limited resources to develop novel accelerator-based technologies and applications.