Author: Miyajima, T.
Paper Title Page
WG1007
 Status of 500-kV DC Gun at JAEA  
 
  • N. Nishimori, R. Hajima, R. Nagai
    JAEA, Ibaraki-ken, Japan
  • Y. Honda, M. Kuriki, T. Miyajima, M. Yamamoto
    KEK, Ibaraki, Japan
  • H. Iijima
    HU/AdSM, Higashi-Hiroshima, Japan
  • M. Kuwahara, T. Nakanishi, S. Okumi
    Nagoya University, Nagoya, Japan
  
  We have developed a 500-kV DC gun at JAEA. It is difficult to apply DC high voltage on a ceramic insulator with a stem electrode because of field emission from the electrode. By employing a segmented insulator with rings which guard the ceramics from the field emission, we succeeded in applying 500-kV on the ceramics for eight hours without any discharge in Dec. 2009. This high voltage testing was performed with a simple configuration without NEG pumps and electrodes. In Jul. 2009, we reached 380kV with electrodes in place before we suffered field emission problem from the cathode electrode. Then we generated beam at 300kV in Nov. 2010. After beam generation we have continued high voltage testing with electrodes in place. In Jul. 2011, we reached 510kV, before suffering another field emission problem from cathode electrodes. The problem may be attributed to small dust inside our gun chamber. We are trying to reach 550kV by solving the small dust problem. Our current status of development will be presented in the workshop.  
slides icon Slides WG1007 [6.486 MB]  
 
WG2010
 Strategy of the Lattice and Optics Design of 2 loop Compact ERL and Multi-GeV ERL  
 
  • M. Shimada, K. Harada, Y. Kobayashi, T. Miyajima, N. Nakamura, S. Sakanaka
    KEK, Ibaraki, Japan
  • R. Hajima
    JAEA, Ibaraki-ken, Japan
  
  Multi-GeV class energy recovery linac (ERL) is considered as a successor of X-ray light source, Photon Factory. As an optional light source, XFEL-O is planned to be operated by utilizing the ERL loop as a recirculating linac to accelerate an electron beam twice. In both ERL and XFEL-O projects, the extreme low emittance is necessary to achieve the high performance. Therefore, an emittance growth induced by space charge (SC) effects and coherent synchrotron radiation (CSR) wake is the critical issue in an optics design. The SC effects are remarkable in non-relativistic energy region such as an injector and after energy recovering. CSR wake affect an electron bunch in the bending magnets. To evaluate the beam quality including the effects, we utilize the 6D tracking codes, General Particle Tracer (GPT) and 'elegant'. The codes are switched at the reasonable electron energy: it is named self-consistent start-to-end simulation (S2E). The S2E simulation has been demonstrated for the 200 MeV class Compact ERL (cERL) with a double loop circulation. We report the strategy of lattice design and S2E simulation for the multi-GeV ERL as well as cERL.  
slides icon Slides WG2010 [2.290 MB]  
 
WG2022
 Envelope Matching from Injector to Main Linac for ERL  
 
  • T. Miyajima, K. Harada, Y. Kobayashi, N. Nakamura, T. Obina, S. Sakanaka, M. Shimada
    KEK, Ibaraki, Japan
  • R. Hajima
    JAEA, Ibaraki-ken, Japan
  • J.G. Hwang
    Kyungpook National University, Daegu, Republic of Korea
  
  Since the brilliance of electron beams in Energy Recovery Linac (ERL) is primarily determined by the performance of its injector, the improvement of the injector performance is essential issue. After the injector, the electron beams are accelerated by a main linac to relativistic energy region, in which an emittance growth due to space charge force can be ignored. Because an injected beam with lower energy and a returned beam with higher energy pass through the same main linac, the beam optics in the main linac is restricted to design a reasonable optics throughout the return loop. Therefore, minimization of the emittance, and matching of beam optics to that of the return loop have to be carried out during the injector optimization. The injector parameters have been optimized using multi-objective method with genetic algorithm and a particle tracking code GPT. However, the optimized emittance was far larger than a target emittance, so that some conflict between the minimization of emittance and the restriction of beam optics have been found in the optimization. We report the optimization results, and the strategy to avoid the conflict and to produce a reasonable beam performance.  
slides icon Slides WG2022 [2.786 MB]  
 
WG2025 Investigation of the Effect of Space Charge in the compact-Energy Recovery Linac 78
 
  • J.G. Hwang, E.-S. Kim
    Kyungpook National University, Daegu, Republic of Korea
  • T. Miyajima
    KEK, Ibaraki, Japan
  
  Compact energy recover linear(ERL) accelerator is a prototype of the 5 GeV ERL accelerator at KEK. The injector system has two SRF cavities which have the frequency of 1.3 GHz. It accelerates the bunches to the energy of 5 MeV. This beam was injected to the main ring and then it was accelerated to energy of 35 MeV at the main superconducting RF linac. Due to the low beam energy on the main ring, the investigation of the effect of space charge (SC) which causes the growth of the energy spread is important to produce the low emittance beam. For the production of the low emittance beam, the optimization of the merger was performed. To obtain smaller emittance at the exit of merger, the effect of the energy spread was also investigated by changing of the kd which is defined by the ratio of energy spread to length of the bunch. In this calculation, we got the noralized transverse emittance of 0.74 mm-mrad at the exit of merger section. The effect of the SC was estimated on the main SRF section, arc section and deceleration section. From the results of the study of SC effect in the c-ERL, it is shown that the optics distortion due to the SC needs to be corrected.  
slides icon Slides WG2025 [0.980 MB]  
 
WG4002
 Beam Instrumentation for the Compact ERL at KEK  
 
  • T. Obina, K. Haga, T. Honda, Y. Honda, T. Miyajima, M. Tadano, R. Takai, Y. Tanimoto, M. Tobiyama, T. Uchiyama
    KEK, Ibaraki, Japan
  • S. Matsuba
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
  
  At KEK, construction of the Compact ERL (cERL) is under way. Design status of beam instrumentations such as BPMs (stripline electrode) and screen monitors are described. Requirements for detection circuit and other signal processing equipemnts and data transfar/archiving system are also reported.  
slides icon Slides WG4002 [2.347 MB]