• H. Fares, Y. Kuwamura, M. Yamada
  Kanazawa University, Kanazawa

In the Cherenkov free electron laser, the interacted electron with the electromagnetic (EM) wave can be represented as a point particle or as a spatially spreading electron wave in the classical or quantum mechanical framework, respectively. In our previous theoretical analysis for the optical region, the electron is described by a plane wave with finite spreading length. This electron wave model was successfully implied for the optical region whereas the spreading length of the electron wave is greater than the wavelength of the optical wave. In this work, when the EM wavelength is sufficiently greater than the spreading length of the electron wave, such as in the microwave region, the electron is assumed to be a spatially localized point particle. This classical analysis is performed using same parameters used in the quantum electron wave model, such as a coupling coefficient between the electron beam and the EM field and the electron relaxation time. Also, we present analytical expressions to describe the stimulated and spontaneous emissions. We show that the classical treatment is consistent with the quantum analysis applied in the optical regime.

• S. Ushijima, H. Fujisawa, M. Ichikawa, Y. Iwashita, H. Tongu, M. Yamada
  Kyoto ICR, Uji, Kyoto

A compact neutron source using Li(p,n) or Be(p,n) reaction is proposed. The proton linac consists of ECR ion source, LEBT(Low Energy Beam Transport), RFQ linac and post accelerator. We assume that energy of the proton beam is 3MeV and its peak current is 40 mA operated at the repetition rate is 25Hz with the pulse width of 1ms. The beam from the ion source should be matched to the RFQ, where solenoid coils can handle the large current beam in this LEBT section. To reduce energy consumption in LEBT we're trying to design the Hybrid Electromagnet that consists of solenoid coils and permanent magnets. We use PANDIRA, TRACE-2D, and PBGUNS computer codes in order to simulate the magnetic field and the beam transport through LEBT. In this paper the design of this magnet and the result of its beam matching based on simulation will be presented.

• M. Yamada, M. Ichikawa, Y. Iwashita, T. Kanaya, H. Tongu
  Kyoto ICR, Uji, Kyoto
• K.H. Andersen, P.W. Geltenbort, B. Guerard, G. Manzin
  ILL, Grenoble
• M. Bleuel
  RID, Delft
• J.M. Carpenter, L. Jyotsana
  ANL, Argonne
• M. Hino, M. Kitaguchi
  KURRI, Osaka
• K. Hirota
  RIKEN, Wako, Saitama
• S.J. Kennedy
  ANSTO, Menai
• K. Mishima, H.M. Shimizu, N.L. Yamada
  KEK, Tsukuba

We have developed a motorized magnetic lens for focusing of pulsed white neutron beams. The lens is composed of two concentric permanent magnet arrays, in sextupole geometry, with bore of 15 mm and magnet length of 66 mm. The inner magnet array is stationary, while the outer array is rotated (the frequency of the modulation of magnetic field inside the bore ν ≤ 25Hz), providing a sextupole magnetic field gradient range of 1.5x10⁴T/m² ≤ g' ≤ 5.9x10⁴T/m². By synchronization of a pulsed neutron beam with the sinusoidal modulation of the magnetic field in the lens, the beam is focused, without significant chromatic aberration, over a wide neutron wavelength band. We have constructed a focusing-SANS (Small Angle Neutron Scattering) test bed on the PF2-VCN (Very Cold Neutron) beam line at the Institut Laue-Langevin in Grenoble. The beam image size matched the source size (≈ 3mm) over of wavelength range of 30Å ≤ λ ≤ 48Å with focal length of ~ 2.3 m. Further, we have demonstrated the performance of this device for high resolution time-of-flight (tof) SANS for a selection of polymeric & biological samples, in a compact geometry of just 5 m.

• M. Ichikawa, H. Fujisawa, Y. Iwashita, H. Tongu, S. Ushijima, M. Yamada
  Kyoto ICR, Uji, Kyoto

We aim to develop a small and high intensity proton source for a compact accelerator based neutron source. Because this proton source shall be located close to RFQ for simplification, ratio of H⁺ to molecular ions such as H²⁺ or H³⁺ must be large. Therefore, we selected an ECR ion source with permanent magnets as small and high intensity ion source. ECR ion sources can provide high H⁺ ratio because of their high plasma temperature. Using permanent magnets makes the ion source small and running cost low. Because there is no hot cathode, longer MTBF is expected. Usually, gas is fed into ion sources continuously, even if ion sources run in pulse operation mode. But, continuous gas flow doesn't make vacuum in good level. So, we decided to install pulse gas valve directly to the plasma chamber. Feeding the gas only when the ion source is in operation reduces the gas load to the evacuation system and the vacuum level can be kept high. Up to now, we developed the first and second model of the ion source. And the research is being conducted using the second model. Recent experimental results will be presented.