Author: Sakaue, K.
Paper Title Page
MOOBA03 Development of a High-power Coherent THz Sources and THz-TDS System on the basis of a Compact Electron Linac 37
  • M. Kumaki, K. Sakaue, M. Washio
    RISE, Tokyo, Japan
  • R. Kuroda, H. Toyokawa, K. Yamada
    AIST, Tsukuba, Ibaraki, Japan
  The high-power terahertz time-domain spectroscopy (THz-TDS) has been developed on the basis of a compact S-band electron linac at AIST, Japan. It is strongly expected for inspection of dangerous materials in the homeland security field. The linac consists of a photocathode rf-gun, two acceleration tubes and a magnetic bunch compressor. The 40 MeV, 1 nC electron bunch is generated and compressed to less than 1 ps. THz radiations are generated in two methods with the ultra-short bunch. One is THz coherent synchrotron radiation (CSR). The other is THz coherent transition radiation (CTR). In the preliminary experiment, it was observed that the focused CTR had the donut profile in a transverse fields due to its initial radial polarization, so that it made Z-polarization. In case of the THz-TDS experiment, CTR was controlled to linearly polarization with the polarizer and focused to an EO crystal to obtain a THz temporal waveform which leads to THz spectrum with Fourier transform. The timing measurement between CTR and a probe laser was realized with OTR using a same optical photodiode. In this conference, we will describe details of our linac and results of the THz-TDS experiment.  
slides icon Slides MOOBA03 [3.342 MB]  
TUPPD034 Multi-bunch Beam Generation by Photo-cathode RF Gun for KEK-STF 1479
  • M. Kuriki, S. Hosoda, H. Iijima
    HU/AdSM, Higashi-Hiroshima, Japan
  • A. Ayaka
    Sokendai, Ibaraki, Japan
  • H. Hayano, J. Urakawa, K. Watanabe
    KEK, Ibaraki, Japan
  • G. Isoyama, R. Kato, K. Kawase
    ISIR, Osaka, Japan
  • S. Kashiwagi
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  • K. Sakaue
    RISE, Tokyo, Japan
  Funding: MEXT, Quantum beam project.
KEK-STF is doing R&D of Super-Conducting (SC) accelerator technology for ILC (International Linear Collider), based on 1.3 GHz RF system. For STF and ILC, the pulse length is 1ms and the repetition is 5Hz. We developed a L-band Normal-Conducting RF gun designed by DESY to provide electron beam over such long pulse duration. For NC Photo-cathode RF gun, such high duty and long pulse operation is a challenging task, because the detuning by the heat load of cavity dissipation power is significant. The RF gun provides the electron pulse train to SC accelerator modules which will be operated at 31.5 MV/m gradient. Precise RF control is essential for SC accelerator because the beam loading and input RF power should be well ballanced for a stable operation. The beam test to demonstrate the stable opeation is very important for SC accelerator R&D. The system is also used to demonstrate high-flux quasi-monochromatic X-ray generation by inverse Compton scattering at KEK-STF. The experiment is carried out from April 2012 to November 2012 at KEK-STF. We report the latest status of the multi-bunch generation by the RF gun.
TUPPD058 Development of an RF Electron Gun for Ultra-Short Bunch Generation 1536
  • Y. Koshiba, T. Aoki, K. Sakaue, M. Washio
    RISE, Tokyo, Japan
  • T. Takatomi, J. Urakawa
    KEK, Ibaraki, Japan
  At Waseda University, various researches are done using a photocathode rf electron gun with a 1.6 cell cavity. Now we are developing a new rf cavity specialized for producing an ultra-short electron bunch, with the collaboration of High Energy Accelerator Research Organization (KEK). We have used SUPERFISH for designing the new rf cavity and PARMELA for beam tracking. The new rf cavity has an extra cell following the 1.6 cell. The extra cell can chirp the energy of electron bunch so we call it ECC (Energy Chirping Cell). ECC chirp the energy because we shortened the length of iris just before the ECC and also the length of ECC itself. Moreover, electric field in ECC is made to be stronger than others. We have confirmed on PARMELA that ECC rf gun can generate an 100pC electron bunch less than 200fsec with the energy of 4.5MeV at about 2.5m away from the cathode. Such an ultra-short electron bunch enables us to generate a coherent terahertz light using ultra-short electron bunch by synchrotron radiation or transition radiation. In this conference, we would like to introduce the detail of the design of this new ECC rf gun, the present progresses and future prospects.  
WEOBB02 Refraction Contrast Imaging via Laser-Compton X-Ray Using Optical Storage Cavity 2146
  • K. Sakaue, T. Aoki, M. Washio
    RISE, Tokyo, Japan
  • M.K. Fukuda, Y. Honda, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  We have been developing a pulsed-laser storage technique in a super-cavity for a compact x-ray sources. The pulsed-laser super-cavity enables to make high peak power and small waist laser at the collision point with the electron beam. Recently, using 357 MHz mode-locked Nd:VAN laser pulses which stacked in a super-cavity scattered off a multi-bunch electron beam, we obtained a multi-pulse x-rays through the laser-Compton scattering. Then, we performed a X-ray imaging via laser-Compton X-ray. The images have edge enhancement by refraction contrast because the X-ray source spot size was small enough. This is one of the evidences that laser-Compton X-ray is high quality. Our laser-Compton experimental setup, the results of X-ray imaging and future prospective will be presented at the conference.  
slides icon Slides WEOBB02 [4.393 MB]  
WEPPD055 Gamma-rays Generation with 3D 4-mirror Cavity for ILC Polarized Positron Source 2645
  • T. Akagi, S. Miyoshi
    Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima, Japan
  • S. Araki, Y. Funahashi, Y. Honda, T. Okugi, T. Omori, H. Shimizu, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • H. Kataoka, T. Kon
    Seikei University, Japan
  • M. Kuriki, T. Takahashi
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
  • K. Sakaue, M. Washio
    RISE, Tokyo, Japan
  • R. Tanaka, H. Yoshitama
    Hiroshima University, Higashi-Hiroshima, Japan
  We are conducting gamma-rays generation experiment by the laser-Compton scattering using a Fabry-Perot cavity. We developed a 3D 4-mirror cavity, and it is installed at the KEK-ATF. By using a 3D 4-mirror cavity, small laser spot can be achieved with stable resonant condition. In addition, we aim 1900 times enhancement of input laser power by a 4-mirror cavity to increase the number of gamma-rays.  
THPPR049 Study on Electron Microbeam Generation for MRT Based on Photo-cathode RF-Gun 4086
  • Y. Yoshida, K. Sakaue, M. Washio
    RISE, Tokyo, Japan
  We have been developing an MRT (Microbeam Radiation Therapy) based on Cs-Te photo cathode RF-Gun at Waseda University. MRT is proposed to treat tumor by using array of several micro-meter parallel beams. In this therapy, irradiated normal tissue repairs itself, by contrast, even a non-irradiated tumor tissue dies. In the other words, the microbeam enhances the radiation sensitivity difference between normal and tumor issues. Therefore, MRT is considered one of the most useful tumor therapies in the future. We have generated electron microbeam by tungsten collimator slit and analyzed their dose distribution in air and in the PMMA phantom. We have used radiochromic film called GAFCHROMIC dosimetry film type HD-810 to measure them. We have compared these experimental results with Monte Carlo simulation of the dose distribution using the EGS5 code. In this conference, we would like to report the electron microbeam procedure, optimization of irradiation condition, evaluation of microbeam specifications and future prospects.