Acceleration greater than an order of magnitude larger than that predicted by a linear theory was... more Acceleration greater than an order of magnitude larger than that predicted by a linear theory was observed in a moderate underdense plasma wakefield when the time delay between the drive and test bunches was less than one plasma oscillation period.
We started a project to develop a very compact accelerator for cancer therapy. To reduce the size... more We started a project to develop a very compact accelerator for cancer therapy. To reduce the size of the system, we adopted a laser plasma ion source using a compact ultra-high intensity laser. We have performed ion generation experiments in which the laser parameters were as follows: The wave length and the pulse duration were 800 nm and 50 fs,
Cold neutrons are good probe for nano meter scale objects. While some huge facilities as spallati... more Cold neutrons are good probe for nano meter scale objects. While some huge facilities as spallation neutron sources are under construction, small local (satellite) neutron sources will help to test new ideas on research. Such small ones are considered to be complementary parts of the huge facilities. Because the threshold energy of the d-d reactions is fairly low, irradiation of deuterated polyethylene (CD2) target by laser induced energetic deuterons may generate neutrons. A preliminary experiment performed with 1TW laser irradiating CD2 foil just before another thick CD2 target is described.
Plasma wakefield caused by a train of 14-MeV linac bunches was detected by a coaxial diode detect... more Plasma wakefield caused by a train of 14-MeV linac bunches was detected by a coaxial diode detector. The pulse period was 350 ps, while the duration of the pulse train was 6 μs. The time evolution of the plasma wave was explained by a simple linear model. The damping time of the plasma wave was derived from the experiments
This paper proposes the use of a solid-state plasma lens in the fs linacs, in which the bunch rad... more This paper proposes the use of a solid-state plasma lens in the fs linacs, in which the bunch radii of the beams are much larger than the lengths. Although gas plasmas degrade vacuum, solid-state plasmas do not. Another problem is that a return current flowing in the beam region of plasmas decreases the focusing power of the lens. By orientating anisotropic plasmas, we can constrain the return current, while maintaining the focusing power.
We have demonstrated the acceleration of a monoenergetic electron beam by a laser-produced wakefi... more We have demonstrated the acceleration of a monoenergetic electron beam by a laser-produced wakefield. Experiments were performed by focusing 2-TW laser pulses of 50 fs on supersonic gas-jet targets. The focused intensity was 5 × 1018 W/cm2 (a0 = 1.5). At an electron density of 1.5 × 1020 cm−3, the clear monoenergetic electron beam from the plasma was obtained at 7 to 15 MeV. The Stokes satellite peak in the forward scattering explained the energy spectra of electrons at various plasma densities well. Although the wakefield propagated 500 microns, which was far beyond the dephasing length, monoenergetic electron beams were obtained.
Acceleration greater than an order of magnitude larger than that predicted by a linear theory was... more Acceleration greater than an order of magnitude larger than that predicted by a linear theory was observed in a moderate underdense plasma wakefield when the time delay between the drive and test bunches was less than one plasma oscillation period.
We started a project to develop a very compact accelerator for cancer therapy. To reduce the size... more We started a project to develop a very compact accelerator for cancer therapy. To reduce the size of the system, we adopted a laser plasma ion source using a compact ultra-high intensity laser. We have performed ion generation experiments in which the laser parameters were as follows: The wave length and the pulse duration were 800 nm and 50 fs,
Cold neutrons are good probe for nano meter scale objects. While some huge facilities as spallati... more Cold neutrons are good probe for nano meter scale objects. While some huge facilities as spallation neutron sources are under construction, small local (satellite) neutron sources will help to test new ideas on research. Such small ones are considered to be complementary parts of the huge facilities. Because the threshold energy of the d-d reactions is fairly low, irradiation of deuterated polyethylene (CD2) target by laser induced energetic deuterons may generate neutrons. A preliminary experiment performed with 1TW laser irradiating CD2 foil just before another thick CD2 target is described.
Plasma wakefield caused by a train of 14-MeV linac bunches was detected by a coaxial diode detect... more Plasma wakefield caused by a train of 14-MeV linac bunches was detected by a coaxial diode detector. The pulse period was 350 ps, while the duration of the pulse train was 6 μs. The time evolution of the plasma wave was explained by a simple linear model. The damping time of the plasma wave was derived from the experiments
This paper proposes the use of a solid-state plasma lens in the fs linacs, in which the bunch rad... more This paper proposes the use of a solid-state plasma lens in the fs linacs, in which the bunch radii of the beams are much larger than the lengths. Although gas plasmas degrade vacuum, solid-state plasmas do not. Another problem is that a return current flowing in the beam region of plasmas decreases the focusing power of the lens. By orientating anisotropic plasmas, we can constrain the return current, while maintaining the focusing power.
We have demonstrated the acceleration of a monoenergetic electron beam by a laser-produced wakefi... more We have demonstrated the acceleration of a monoenergetic electron beam by a laser-produced wakefield. Experiments were performed by focusing 2-TW laser pulses of 50 fs on supersonic gas-jet targets. The focused intensity was 5 × 1018 W/cm2 (a0 = 1.5). At an electron density of 1.5 × 1020 cm−3, the clear monoenergetic electron beam from the plasma was obtained at 7 to 15 MeV. The Stokes satellite peak in the forward scattering explained the energy spectra of electrons at various plasma densities well. Although the wakefield propagated 500 microns, which was far beyond the dephasing length, monoenergetic electron beams were obtained.
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Papers by Atsushi Ogata