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ABSTRACT: We have developed a new driver laser system with repetition rate of 0.1 Hz for the double target x-ray laser at Japan Atomic
Energy Agency. We named the new driver laser TOPAZ. TOPAZ delivers two beams with energy of < 5 J and duration of ̃ ps. Ni-like
Mo and Ag lasers at wavelength of 18.9 nm and 13.9 nm respectively have been successfully generated using TOPAZ
12/2008: pages 161-166;
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ABSTRACT: The photoionization process in xenon clusters irradiated with a soft x-ray laser pulse (hν=89.2 eV, intensity: ~1010 W/cm2) was examined using a time-of-flight mass spectrometer, where the laser photon energy was high enough to ionize Xe 4d inner
electrons (threshold: 67.55 eV for 4d5/2 and 69.54 eV for 4d3/2). The dominant ion yield resulting from Auger decay of 4d hole was Xe3+ ion. This showed that the double Auger transition probability would be enhanced in the cluster environments. In order to
clarify the decay dynamics of 4d inner holes, the electron energy spectrum was measured. It was found that the distinct photo-
and Auger electron lines were not observed, while the energy distribution implies the production of a low temperature cluster
plasma.
12/2008: pages 453-459;
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T. Kawachi,
M. Kishimoto,
M. Kado,
N. Hasegawa,
M. Tanaka, Y. Ochi,
M. Nishikino,
M. Ishino,
T. Imazono,
T. Ohba, [......],
Y. Fukuda,
H. Kotaki,
A. Pirozhkov,
J. Ma,
A. Sagisaka,
M. Mori,
J. Koga,
S. Bulanov,
H. Daido,
T. Tajima
[show abstract]
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ABSTRACT: Recent progress in x-ray laser (XRL) research in Japan Atomic Energy Agency (JAEA) is reviewed. The repetition-rate of the
x-ray laser has been improved from each0 minutes to0 seconds (0.1 Hz) by installing new driver laser, TOPAZ, which allows
us to promote the applications of fully spatial coherent3.9 nm laser in the wide variety of research fields such as material
science, single-shot x-ray holography and atomic physics. In order to improve the present performance of the x-ray lasers,
we have investigated the possibilities of the enhancement of the peak brilliance using v-groove target and the generation
of circularly polarized x-ray laser under a strong magnetic field. Towards shorter wavelength x-ray lasers, we have investigated
several schemes. One is the use of reflection of the light by relativistic plasma mirror driven by laser-wake-field, and the
other is photo-pumping scheme using Kα emission from a solid target.
12/2008: pages 3-12;
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N. Hasegawa,
T. Kawachi,
A. Sasaki,
H. Yamatani,
A. Iwamae,
M. Kishimoto,
M. Tanaka, Y. Ochi,
M. Nishikino,
Y. Kunieda,
H. Kawazome,
K. Nagashima,
H. Yoneda
[show abstract]
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ABSTRACT: We proposed the method of generation of the circularly polarized x-ray laser using the Zeeman splitting. External magnetic
field of 20 T was applied to the gain medium plasma to separate the degenerated lines of nickel-like molybdenum x-ray laser.
The splitting of the x-ray laser line was clearly obtained, and the strength of the magnetic field estimated from the quantity
of the x-ray laser line splitting was quite higher compared with that of the external magnetic field. It implies that there
might be alternative mechanism for enhancement of the magnetic field in the gain medium plasma.
12/2008: pages 99-105;
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S Namba,
K Takiyama,
N Hasegawa,
M Kishimoto,
M Nishikino,
T Kawachi,
K Sukegawa,
H Yamatani,
M Tanaka, Y Ochi,
K Nagashima
[show abstract]
[hide abstract]
ABSTRACT: The xenon clusters were irradiated with a soft x-ray laser pulse having a wavelength of 13.9 nm (hv = 89.2 eV) and intensity of up to 2×1010W/cm2 for the first time. The photon energy was high enough to photoionize inner-shell electrons (4d) of the Xe atom. In contrast to the results obtained in synchrotron radiation experiments, the enhancement of double Auger decay probability with increasing cluster size and x-ray laser intensity was observed.
Journal of Physics Conference Series 06/2008; 112(4):042057.
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[show abstract]
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ABSTRACT: The interaction of large Xe clusters with a soft x-ray laser pulse having a wavelength of 13.9 nm and an intensity of up to 2x10(10) W/cm2 was investigated using a time-of-flight ion mass spectrometer. The corresponding laser photon energy was sufficiently high to photoionize Xe 4d innershell electrons. It was found that Xe3+ ions (which result from double Auger decay of 4d vacancies) became the dominant final ionic product with increasing cluster size and x-ray intensity. This is in contrast to the results of synchrotron radiation experiments involving free Xe atoms, in which Xe2+ is the dominant resultant ion species. Possible mechanisms responsible for the enhancement of the double Auger transition probability in x-ray laser and cluster interaction are discussed.
Physical Review Letters 08/2007; 99(4):043004. · 7.37 Impact Factor
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[show abstract]
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ABSTRACT: The interaction of large xenon clusters with an x-ray laser pulse having a wavelength of 13.9 nm and intensity of up to 2x1010 W/cm2 was investigated using a time-of-flight ion mass spectrometer. The photon energy is high enough to photoionize the inner-shell
electron of the Xe atom. In contrast to the experiment at synchrotron radiation, the enhancement of double Auger decay probability
with increasing cluster size and x-ray laser intensity was observed for the first time.
12/2006: pages 511-515;
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[show abstract]
[hide abstract]
ABSTRACT: We developed new power amplifier using a zigzag slab Nd:glass to generate the TCE x-ray lasers more frequently. The chirped
laser light at the wavelength of 1053 nm was amplified to > 10 J and then compressed to be ~1.6 ps at repetition rate of 0.1
Hz. By using the amplified laser light, gain saturated x-ray laser with the Ni-like silver at wavelength of 13.9 nm was obtained.
12/2006: pages 45-49;
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K. Nagashima,
M. Kishimoto,
T. Kawachi,
N. Hasegawa,
M. Tanaka, Y. Ochi,
M. Nishikino,
K. Sukegawa,
H. Yamatani,
Y. Kunieda,
Y. Kato
[show abstract]
[hide abstract]
ABSTRACT: We are developing plasma x-ray lasers pumped by ultra-short pulse lasers and have concentrated our efforts on developing a
silver x-ray laser (13.9 nm) with spatially full coherence by means of a double target method. Recently, we have succeeded
in developing a unique new pumping laser system, which is a CPA laser consisting of OPCPA and zigzag-slab type glass amplifiers.
The OPCPA was adopted for improving the controllability of pumping pulses instead of a regenerative amplifier and the zigzag-slab
amplifiers were adopted for increasing the repetition rate.
12/2006: pages 29-36;
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ABSTRACT: We have recently reported the successful development of a fully coherent X-ray laser (XRL) at 13.9 nm by an oscillator-amplifier configuration with two targets. In the experiment, a seed XRL beam from the first target is injected into a plasma amplifier at the second target. The observed XRL beam has full spatial coherence and 0.2 mrad of nearly diffraction-limited divergence. In order to improve the output fluence, the amplification properties of the XRL beam have been investigated using various plasma lengths of the second amplifier target. The output energy has been improved by a factor of ten, increasing the length of the gain region to 10 mm, resulting in about 0.2 μJ of output energy.
IEEE Journal of Selected Topics in Quantum Electronics 12/2004; · 3.78 Impact Factor
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ABSTRACT: We have measured temporal durations of Ni-like transient collisional excitation X-ray lasers (4d4p, J=01) using a high-speed X-ray streak camera coupled with a flat field grating spectrometer. The pumping laser pulse consisted of a 400-ps prepulse and a 4.8-ps main pulse derived from a Nd:glass laser system with chirped pulse amplification. A quasi-traveling-wave pumping using a six-step mirror was adopted to synchronize the X-ray laser pulse and the onset of gain in a plasma medium. The X-ray laser outputs from three different materials, silver (Z=47), palladium (Z=46) and molybdenum (Z=42), showed that the X-ray laser duration became shorter as the atomic number decreased.
Applied Physics B 04/2004; 78(7):961-963. · 2.19 Impact Factor
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K. Nagashima,
M. Tanaka,
M. Nishikino,
M. Kishimoto,
M. Kado,
T. Kawachi,
N. Hasegawa, Y. Ochi,
K. Sukegawa,
R. Tai,
Y. Kato
[show abstract]
[hide abstract]
ABSTRACT: We have succeeded in developing a laser-pumped X-ray laser with full spatial coherence at 13.9nm. The X-ray laser beam with a very small divergence of 0.2mrad was generated from double target experiments, where a seeding light from the first laser medium was amplified in the second laser medium. The observed divergence was close to the diffraction limit value within a factor of two. The seeding light was amplified in the second medium without refraction influence and the gain coefficient was 7.9cm-1. From the measurement of visibility, it was found that the spatial coherent length was longer than the beam diameter.
Applied Physics B 01/2004; 78(7):927-932. · 2.19 Impact Factor
