C. Thongbai

Femtosecond electron pulses production system

The SURIYA project is designed to generate femtosecond (fs) electron pulses at the Fast Neutron Research Facility (FNRF), Thailand. The fs electron pulses production system consists mainly of a thermionic cathode RF-gun, a magnetic bunch compressor in form of an alpha magnet (α-magnet), a linear accelerator (linac), a beam transport line, and various electron beam diagnostic instruments. This system aims to produce a 20-25 MeV electron beam with micropulses of less than 100 fs in length. Theses pulses can be used either for direct experimentation or to produce fs pulses of intense coherent far infrared radiation (FIR) and/or x-ray. In this paper, an overview of the system and characteristics of its major components will be presented.

Generation of Femtosecond Electron and Photon Pulses

Femtosecond (fs) electron and photon pulses become a tool of increasing importance to study dynamics in ultrafast processes. Such short electron pulses can be generated from a system consisting of a thermionic-cathode thermionic-cathode thermionic-cathode RF-gun and a magnetic bunch compressor. The fs electron pulses can be used directly or used as a source to produce equally short electromagnetic radiation pulses via certain kind of radiation production processes. At the Fast Neutron Research Facility (FNRF), Thailand, we are especially interested in production of radiation in Far-infrared and X-ray regime. In the far-infrared wavelengths, the radiation emitted from fs electron pulses is emitted coherently resulting high intensity radiation. In the X-ray regime, development of fs X-ray sources is crucial for application in ultrafast sciene.

Simulation of Irradiation-Based Processing System for Natural Rubber Vulcanization

Natural rubber is an important export product of Thailand, which presently contributes about 40% of global production and export. In order to make the natural rubber latex to be durable material, the proper vulcanization process is needed. In typical vulcanization process, chemical substances are added to improve the rubber properties. This may cause some problems e.g. toxicity, blooming effects and unpresented smell due to the additive substances. Vulcanization using an accelerated electron beam does not need to add possibly toxic chemical compounds, especially sulfur. Thus, it was proved to be an alternative method for high quality natural rubber vulcanization. This paper presents about simulation of electron beam irradiation for natural rubber vulcanization with variable electron beam energy and current of 0.5-4 MeV and 10-100 mA, respectively. These ranges of the electron beam energy and current will give adjustable absorb dose, which is the most important parameter for electron beam processing. The absorb energy and its distribution in the natural rubber latex are simulated by using a Monte Carlo method program, GEometry ANd Tracking 4 (GEANT4), with the aim to find the optimal conditions of electron beam properties for sufficient natural rubber vulcanization. Study results of the energy distribution for electron beam penetration in the natural rubber latex are presented and discussed in this paper.

Studies on Electron Linear Accelerator System for Polymer Research

This research focuses on modification of an electron linear accelerator system for irradiation of natural rubber latex and polymeric materials at the Plasma and Beam Physics Research Facility, Chiang Mai University, Thailand. This is in order to study the change of material properties due to electron beam irradiation. The main accelerator system consists of a DC thermionic electron gun and a short standing-wave linac. This system will be able to produce electron beams with variable energy in the range of 0.5 to 4 MeV. The linac macro pulse frequency is adjustable within the range of 20 to 1000 Hz. The macro pulse duration is 4 μs. The electron pulse current can be varied from 10 to 100 mA. This lead to the electron dose of about 0.44 to 4.4 Gy-m/min. In this paper, overview of the accelerator and the irradiation system is presented. Results of low-level RF measurements of the accelerating structure are also reported and discussed. INTRODUCTION Electron beam processing can be used to modify chemical and physical properties of materials with the aims to enhance their qualities, to promote commercial value and to reduce undesirable by-products [1]. Using electron beams produced from an accelerator is an alternative method to the conventional ones using gamma rays or chemical additives. In some applications, electron beam irradiation processing can produce unique effects that cannot be duplicated by other means. One of good examples, which is in our interest, is the natural rubber vulcanization. The cross-linking process can happen without heating and in the absence of chemical vulcanization agents [2]. Furthermore, the electron beam vulcanization has the advantages of being very low cytotoxicity and having potential in reduction of extractable protein, which is considered to be primary source of the allergic reaction. This research aims to develop a linear accelerator system for natural rubber vulcanization and polymer crosslinking by using major parts of the accelerator system from a defunct medical linac donated to the Plasma and Beam Physics Research Facility, Chiang Mai University. This electron accelerator system will be used to define optimal conditions for natural rubber vulcanization and for polymer cross-linking with medium energy electron beams of 0.5 to 4 MeV for future development of a practical industrial unit of the electron beam processing system. Overview of the accelerator system and the processing unit as well as some study results concerning the accelerating structure are reported and discussed in this paper. METHODOLOGY Electron Accelerator System The completed system of electron beam irradiation for natural rubber vulcanization and polymer cross-linking consists of the electron linear accelerator system (as shown in Fig. 1), electron beam measurement and analysis components, the beam sweeper and the movable stage for the sample container, and the control system for the linac operation and for the electron beam treatment on the natural rubber and polymer. The whole system will be located inside the underground radiation shielding hall at the Plasma and Beam Physics Research Facility. The main components for the radio-frequency (RF) wave generator and the accelerating structure are adopted from a 4-MeV medical linac, which was donated from the Maharaj Nakorn Chiang Mai Hospital, Thailand. The systems for beam measurement and analysis, the beam sweeper and the rubber processing experimental station will be developed at the laboratory. Figure 1: Schematic layout of the electron linear accelerator for rubber vulcanization. As shown in Fig. 1, the accelerator system consists of a DC electron gun, a standing-wave linear accelerator equipped with a related radio-frequency (RF) system and a sweeping coil with a vacuum horn chamber. The DC electron gun is a Pierce-type electron gun with a circular thermionic cathode with diameter of 4.86 mm. The linear accelerator (linac) composes of five TM010-mode standingwave resonant cavities that can be used to accelerate electron to reach the maximum energy of about 4 MeV for the supplied RF power of 2 MW. The RF wave is transported from a 2-MW magnetron to the linac via a ____________________________________________ *Corresponding author: sakhorn.rimjaem@cmu.ac.th Proceedings of IPAC2016, Busan, Korea TUPOY039 08 Applications of Accelerators U02 Materials Analysis and Modification ISBN 978-3-95450-147-2 1985 C op yr ig ht

Progress on Reflective Terahertz Imaging for Identification of Water in Flow Channels of PEM Fuel Cells

This work reports an application of reflective terahertz (THz) imaging for identification of water distribution in the proton exchange membrane (PEM) fuel cell. The THz radiation generated from relativistic femtosecond electron bunches is employed as a high intensity source. The PEM fuel cell is designed specifically for the measurement allowing THz radiation to access the flow field region. The THz image is constructed from reflected radiation revealing absorptive area of water presence. The technique is proved to be a promising tool for studying water management in the PEM fuel cell. Detailed experimental setup and results will be described.

THz radiation based on femtosecond electron bunches and THz imaging

The THz radiation from femtosecond electron bunches is focused on a sample which will be scanned using an xy-translation stage. The transmission intensity at different points of the sample are detected to construct a THz image. THz images of some samples were demonstrated using the THz imaging system.

Femtosecond Electron and Photon Pulses Facility in Thailand

Femtosecond electron and photon pulses facility has been established as SURIYA project at the Fast Neutron Research Facility (FNRF). Femtosecond electron bunches can be generated from a system consisting of an RF gun with a thermionic cathode, an alpha magnet as an magnetic bunch compressor, and a linear accelerator as a post acceleration section. Femtosecond electron pulses can be used directly or used as a source to produce equally short electromagnetic (EM) radiation pulses via certain kind of radiation production processes. At SURIYA project, we are interested especially in production of radiation in Far‐infrared (FIR) regime. At these wavelengths, the radiation from femtosecond electron pulses is emitted coherently resulting in high intensity radiation. Overview of the facility, the generation of femtosecond electron bunches, the theoretical background of coherent transition radiation and the recent experimental results will be presented and discussed in this paper.

Radiation Production Using Femtosecond Electron Bunches

Femtosecond electron bunches can be generated from a system consisting of an RF gun with a thermionic cathode, an alpha magnet, and a linear accelerator and can be used to produce femtosecond (fs) electromagnetic radiation pulses. At the Fast Neutron Research Facility (FNRF), Thailand, we are especially interested in production in Far-infrared (FIR) and x-radiation. In the far-infrared, radiation is emitted coherently for wavelengths which are longer than the electron bunch length, yielding intense radiation. Although, the x-rays emitted are incoherent, its femtosecond time scale is crucial for development of a femtosecond x-ray source.

Beam Characterizations at Femtosecond Electron Beam Facility

The SURIYA project at the Fast Neutron Research Facility (FNRF) has been established and is being commissioning to generate femtosecond (fs) electron bunches. Theses short bunches are produced by a system consisting of an S-band thermionic cathode RF-gun, an alpha magnet (α-magnet) serving as a magnetic bunch compressor, and a SLAC-type linear accelerator (linac). The characteristics of its major components and the beam characterizations as well as the preliminary experimental results will be presented and discussed in this paper.