A. Ogata

Effect of different catalysts on the decomposition of VOCs using flow-type plasma-driven catalysis

This paper presents the effect of different catalysts on the decomposition of benzene and toluene using flow-type plasma-driven catalyst (PDC) system. Three representative materials of titanium dioxide, two types of gamma-alumina and two zeolites were tested. Several types of metal catalysts (Ag, Ni, Pt, Pd) and their loading amount were also investigated for the optimization of the PDC system. Three key factors of energy consumption, carbon balance and safety of products were emphasized in evaluating the performance of different catalysts. The type of catalysts greatly influenced on the carbon balance, CO₂ selectivity, ozone formation, while no much difference was observed in the degree of enhancement in energy efficiency. Pt/gamma-Al₂O₃ catalyst was found to be effective in enhancing the CO₂ selectivity. The CO₂ selectivity increased as Ag-loading amount on TiO₂ catalyst increased. The 4.0 wt% Ag/TiO₂ catalyst was effective in suppressing the formation of NO₂ and N₂O. Zeolites showed comparable decomposition efficiency and good carbon balance, while the CO₂ selectivity was poor compared to the other catalysts. Mechanical mixing of 2.0 wt% Ag/H-Y zeolite with Pt/gamma-Al₂O₃ was effective in enhancing the CO ₂ selectivity without changing other performance

Plasma wake-field accelerator experiments at KEK☆

Abstract We report on a plasma wake-field accelerator experiment using a high-intensity 250 MeV electron beam of the linac at KEK (National Laboratory for High Energy Physics, Japan). The experiment provedthe plasma wake-fields excited by a train of several bunches accelerate a trailing bunch. We observed an approximately 4 MeV shift of beam energy in a 1 m long plasma with a density of 4 × 1011 cm−3. We describe the present status and the future plan of experimets based on a new scheme of a plasma wake-field accelerator driven by a train of multiple bunches.

Plasma lens and wake experiments in Japan

Plasma lens and wake experiments performed and planned in Japan are reviewed. Overdense plasma lens experiments were conducted at the University of Tokyo on a 18 MeV linac. The change in energy distribution of linac beams caused by the plasma wakefield was measured at KEK on a 500 MeV linac. Laser wakefield acceleration experiments are planned at Osaka University using a 30TW Nd:glass laser.

Experiments of high energy gain laser wakefield acceleration

Abstract The wakefield acceleration of electrons has a great potential for the future accelerator because of its high accelerating field gradient. We have obtained over 100xa0MeV acceleration gain by the wakefield generated by a 2xa0TW Tixa0:xa0sapphire laser system. In the acceleration experiment, the 17xa0MeV electrons from a linac were used for the injection beam. The synchronization between the RF signal and the laser pulse was achieved within the time jitter of 3.7xa0ps. Due to the self-focusing and ionization, a long propagation length and high field gradient were realized. The self-focusing effect of the laser was confirmed by the laser spotsize measurement along the beam axis. The plasma density oscillation was measured by using the frequency domain interferometry. The acceleration gain expected from the plasma density measurement was consistent with the result of the acceleration experiments.

Femtosecond electron beam generation and measurement for laser synchrotron radiation

One of the S-band twin linacs (18L linac) of Nuclear Engineering Research Laboratory of University of Tokyo is modified in order to produce femtosecond electron single bunch for femtosecond X-ray generation via Thomson backward scattering, namely laser synchrotron radiation. Laser photocathode RF gun and chicane-type magnetic pulse compressor are installed at the S-band linac. 10 ps (FWHM) laser pulse generates 5 MeV, 10 ps (FWHM), 1 nC electron single bunch, which is accelerated up to 20 MeV in the S-band accelerating tube and compressed to 200 fs (FWHM) by the chicane. Design study has been performed by using the code of PARMELA and the installation has been finished. For precise and reliable measurement of the compressed pulse length, the comparison of measurement between the femtosecond streak camera and coherent transition radiation interferometry was carried out. Good agreement between them for 1—10 ps (FWHM) pulses was achieved. A new Michelson interferometer for the 200 fs pulse is now under construction. ( 1998 Elsevier Science B.V. All rights reserved.

A Proof-of-principle Experiment of Laser Wakefield Acceleration

A principle of the laser wakefield particle acceleration has been tested by the Nd : glass laser system with the peak power of 30 TW and the pulse duration of 1 ps. The particle acceleration up to 18 MeV/c has been demonstrated by injecting 1.0 MeV/c electrons emitted from a solid target by an intense laser impact. The corresponding field gradient achieves 1.7 GeV/m.

On optical resolution of beam size measurements by means of synchrotron radiation

Abstract This Letter deals with resolution limited by diffraction in optical measurements of beam sizes by means of synchrotron radiation. We treat the synchrotron radiation as a laser-like Gaussian beam with a small opening angle. Truncation caused by a lens with finite size is taken into account. It is shown both theoretically and experimentally that the measurement is marginal but possible under the diffraction, if the lens diameter is large enough compared with the spot size of the radiation.

A table-top X-ray FEL based on the laser wakefield accelerator-undulator system

Laser wakefield acceleration makes it possible to build a compact electron linac. While acceleration is attributed to longitudinal wakefields, transverse wakefields simultaneously generated by a short laser pulse can serve as a plasma undulator with a very short wavelength equal to half of the plasma wavelength. We propose a new FEL concept for X-rays based on a laser pulses delivered from a table-top terawatt laser. The system is composed of the accelerator and undulator stages in a table-top size. A low energy electron beam is accelerated due to laser wakefields in the accelerator stage. A bunched electron beam travelling to the opposite direction of driving laser pulses produces a coherent X-ray radiation in the undulator stage. A practical configuration and its analysis are presented.

Femtosecond single-bunched linac for pulse radiolysis based on laser wakefield acceleration

A conceptual design of a linac for pulse radiolysis is presented based on laser wakefield acceleration. Pulse radiolysis spectroscopically studies the initial stage of chemical reactions induced by electron beams. Single-bunched beams with a bunch-length on the order of a femtosecond are ideal for this purpose. The present design gives pure 20 pC single-bunches with an RMS bunch length of less than 10 fs. It accelerates and compresses only the head part of a high-current beam from a photocathode. Some practical problems concerning the design are also presented.

Wakefield accelerator using twin linacs

Abstract A collinear wakefield test facility using two linacs with a common test section is described. Beams from one linac excite wakefields in a test medium s