Precision Control for Beam Irradiation Dose by Developing a Real-time Dose Monitoring System
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Precision Control for Beam Irradiation Dose by Developing a Real-time Dose Monitoring System Yong Seok Hwang, Maengjun Kim, Jaekwon Suk, Chan Young Lee, Jun Mok Ha, Chorong Kim, Dong Seok Kim, Sunmog Yeo, Myung-Hwan Jung, Won-Je Cho, Hye-Ran Jeon, Jae S. Lee and Jun Kue Park∗ Korea Multipurpose Accelerator Complex, Korea Atomic Energy Research Institute, Gyeongju 38180, Korea (Received 8 January 2020; revised 5 March 2020; accepted 6 March 2020) We have developed a real-time dose monitoring system for a low-energy ion-beam facility. Before we developed the monitoring system, the system had given a substantial error of ±23% when we irradiated an ion beam with a dose as much as 3.0 × 1016 cm−2 on the Si substrate. Moreover, a low irradiation dose as small as 1013 cm−2 was scarcely able to be controlled because of a too short irradiation time of several seconds, producing a greater dose error. To develop a real-time dose monitoring system, in this work, we employed a current integrator in conjunction with a beam stopper, by which a dose of 3.0 × 1016 cm−2 can be exactly irradiated on the sample with less than ±6% error, which was ensured by the measurements of Rutherford backscattering spectroscopy. Keywords: Real-time dose monitoring system, Ion-beam facility, Rutherford backscattering spectroscopy DOI: 10.3938/jkps.77.395
I. INTRODUCTION The gas ion beam facility installed at the Korea Multipurpose Accelerator Complex (KOMAC) has been providing various kinds of ion beam outputs, such as H+ , N+ , Ar+ , and He+ , for many scientific users [1]. Moreover, more kinds of gas ions have been developed in this facility. For reliable beam irradiation effects on matter by using this facility, precision irradiation doses as one intends should be made [1–3]. Previously, however, from a scientific point of view, we often encountered unacceptable beam-irradiation effects on matter. In many cases, due to a greater dose uncertainty, a low irradiation dose may frequently invoke some deviation from the irradiation dependence. Thus, exact control of beam irradiation doses is essential if accurate beam irradiation effects on matter are to be obtained [2,3]. Before we had developed a real-time dose monitoring system, we used a digital oscilloscope to estimate the dose irradiated [4], the current coming from Faraday cups being converted to a voltage signal and then being integrated. It took a long time to analyze the total charge because of the big data size recorded at a rate of ∼1Mb/sec wasting much memory space, thus making estimates of the irradiation doses difficult. In this older system, we needed to keep monitoring doses irradiated and stopped the irradiation by pushing a button manually when the irradiating dose seems to be consistent with the intended dose. This method frequently led to ∗ E-mail:
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pISSN:0374-4884/eISSN:1976-8524
an unwanted error in controlling the irradiation dose. In this work, we have developed a real-time beam monitoring and control system, for which we employed a digital current integrator an
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