Sang-Pil Yun

MFM and gas adsorption isotherm analysis of proton beam irradiated multi-walled carbon nanotubes

To enhance the gas adsorption properties and modify the physical properties of carbon nanotubes, multi-walled carbon nanotubes (MWCNTs) were irradiated by high-energy proton beams, and the physical properties including morphology and local surface structure were investigated by using a transmission electron microscope (TEM), magnetic force microscope (MFM) and a gas adsorption isotherm apparatus which can deeply probe the fine structure of surface. Interestingly, clearer MFM images were obtained from the proton irradiated samples which supports that carbon exhibits magnetism under proton bombardments, although the intrinsic magnetic property is not understood. The layering properties of argon on MWCNTs were measured from 59 to 69 K and the interaction of argon on the surface was analyzed. The calculated values of isosteric heat of adsorption demonstrated that higher interaction of gas molecules with surface is found from the proton irradiated MWCNTs. This result strongly supports that the local surface modification, partial defects, for example, were created due to the external high energy impacts. Our results are worthy to note that gas adsorption technique can provide the fine atomic resolution which beyond the one of TEM and MFM.

Proton beam energy measurement using semiconductor detectors at the 45MeV test beam line of PEFP

For the pilot and feasibility studies on the development of beam utilization technologies of PEFP (proton engineering frontier project), the test beam line was installed at the MC-50 cyclotron of KIRAMS (Korea institute of radiological and medical sciences) [1-2]. The energy measurement of proton beam with high accuracy is very important for the some experiments such as radiation hardness test of semiconductor devices for the spacecraft, detector development and test for the nuclear physics, etc. Energy measurement of 35 MeV and 45 MeV proton beam using a 5 mm thick Si(Li) in air was performed. The energy was controlled by Al degrader in the range of 0.02 mm~6.2 mm. The measured value was compared to the results of code simulation using SRIM 2003.

Commissioning of the RI Production Beam Line of KOMAC

A radioisotope (RI) production beam line has developed at Korea Multi-purpose Accelerator Complex (KOMAC) in 2015 and the commissioning started in 2016. The beam parameters of the beam line are 100 MeV beam energy with a maximum 30 kW beam power, which is driven by KOMAC 100 MeV proton linac. The main components of the beam line are a beam transport system, a target transport system, a cooling system for target and hot cell. KOMAC has a plan to commission the beam line and get an operation license in 2016 and start user service in 2017. In this paper, the development and initial commissioning results of the RI production beam line are presented.

Diffusion and Thermal Stability of Implanted Hydrogen in ZnO Nanorods

The 20-MeV proton-beam with a fluence of 10 cm was irradiated on ZnO nanorods. The effects of protonbeam irradiation on ZnO nanorods are investigated by using H nuclear magnetic resonance (NMR) spectroscopy. After irradiation, new and modified NMR resonance lines are observed in H NMR spectra. The diffusion and thermal stability of each proton species are investigated from the laboratoryand rotating-frame spin-lattice relaxation data depending on temperature. Understanding the properties of thermally stable hydrogen species created by the beam irradiation may promise many possible applications, since the hydrogen stable up to high temperature only meets the device working conditions.

Solid Targetry for the Isotope Production Facility at the KOMAC 100 MeV Linac

The construction of the isotope production facility was recently completed on the 100 MeV proton linac at the KOMAC (Korea Multi-purpose Accelerator Complex). To produce the Sr-82 and Cu-67, we have prepared the solid targetry which consist of target transportation system , target cooling system and a hot-cell for remote handling. The Isotope production targets are made of RbCl pellet, Zn metal disc and stainless steel cladding. For the proton beam irradiation, the targets are transported by target drive system which consist of drive chain and guide rail by remotely. In this paper, we will report the detailed design, fabrication and operation status of the solid targetry at the KOMAC isotope production facility. TARGET PREPARATION To design RI target, we have derived the optimum thickness of target materials considering the beam energy loss by the beam window, cooling water and target claddings through SRIM calculation [2]. Figure 1 describes the typical target configuration for Sr-82 production, which is consisted of 1 RbCl target and aluminum dummy target. Figure 1: Target configuration for Sr-82 production. For the Sr-82 and Cu-67, the pressed RbCl pellet and Zn metal disc was prepared. These target materials have the natural abundance of isotopes and they are encapsulated in stainless steel cladding with o.d. of 60 mm and i.d. of 50 mm with 0.3 mm window for the proton irradiation. To prevent the leakage of the radioactive species inside target claddings, the cladding is fabricated by laser welding. After the target cladding fabrication, the leakage tests have been conducted by using the penetration test. Figure 2 shows the fabricated proto-type target claddings after welding process. (a) RbCl pellet and its target cladding (b) Zn disc and its target cladding Figure 2: The proto-type target for Sr-82 / Cu-67 production.