Focusing a femto-second laser (1 mJ/pulse repetition 1 kHz) on a special tape, a strong radiation consisting of the
electron beam of ~ 200 keV and X-rays of ~ 6.4 keV (5 %) has been generated. It has been verified that the radiation
source is sufficient to kill the tumor cells and the DNA laddering structure in the in-vivo test is obtained. More test
implanting the tumor under the skin of mouse and irradiating the laser-generated radiation, we have shown the radiation
has a clear powerful therapeutic capability. For about 80 % of mice irradiated, their tumor disappeared. For further
clinical test use, a compact laparoscope-type unit mounted on an articulated arm has been constructed and it can generate
the necessary amount of the radiation dose.
A localized X-ray source for the pin-point treatment of cancers using femto-second laser has been developed. Particular
emphasis is put on i) stable emission of X-rays, ii) a sufficient dose and iii) a sufficient photon energy for the treatment.
Almost 80 % of the objectives listed above has been realized and the first X-ray irradiation test on cancer cells shows a
significant effect on the cancer DNA.
Laser propulsion has many advantages over other conventional methods of producing thrust in space applications. For example, laser energy can be delivered to a remote objects such as space debris which otherwise is impossible to make thrust on its surfaces to remove from the orbits. However, essential advantage of laser propulsion lies in the fact that the characteristics of laser propulsion can be controlled over wide range of parameters by changing laser irradiation conditions. This advantage is based on the capability of controlling specific energy carried by propellant. The specific energy is a key parameter of thrust performance since it determines the propellant temperature or expanding velocity and thus propulsion efficiency. A number of researches so far conducted have treated laser plasma interactions created on solid surfaces with laser parameters such as wavelength, pulse width, intensity, as well as ambient gas pressure. The present study will give a new insight to laser plasma interactions and/or new mechanism of laser thrust generation. Laser energy is deposited inside solid target and, as an initial condition, confined by solid material. Since the confinement time is an order of milli-second, both shock waves and thermal conduction can tale part in the energy transfer process and therefore, give more controllable parameters over the thrust characteristics. In this manner, specific energy carried by target material or propellant can be controlled by changing the depth of energy deposition region. This will give a new dimension of controlling laser plasma characteristics for laser propulsion. In this paper, experimental results and physical insights will be presented as to propelled mass and velocity dependence on laser energy and temporal behavior of impulse generation, as well as enhancement of impact generation over the conventional ablation scheme.
KEYWORDS: Solar cells, Solar energy, Laser energy, Semiconductor lasers, Energy efficiency, Cryogenics, Systems modeling, Telecommunications, Sun, Laser systems engineering
A use of the energy transmission system is proposed to supply the scientific rover to confirm the existence of ice on the moon at the bottom of craters in the lunar polar region, where no sun light reaches at all through the year and it is a cryogenic environment. A small system model has been fabricated that it is principally possible. A full size rover model is now going on and 100 m energy transmission experiment will be done soon. Major technological problems to be solve to realize the system in the actual lunar exploration is also discussed.
In order to increase the plasma production efficiency in the laser triggered lightening experiment, it is proposed that a hyper-velocity micro-particle flow produced by a chemical explosion shall be used along the laser beam path. A preliminary experiment to verify the proposal has successfully been done in the laboratory using 100 J 80 nsec CO2 laser pulse.
Generation of thrust by laser propulsion has gained reality and much attention due to the recent development of high average-power lasers and demonstrations of sizeable object launching. Generating thrust requires a large amount of energy or high average power, but the question is how it is provided. This study deals with effectiveness of highly repetitive ultrashort laser pulses on generating high momentum coupling coefficient, Cm in vacuum condition. Two laser parameters, pulse width and repetition rate, have been studied in terms of the enhancement of Cm. It was found that with pico- and femtosecond pulse ablation, higher Cm is generated compared with longer pulse duration although it is on the same scaling as longer pulse duration. With high repetition rate pulses (80 MHz), more than one order of magnitude enhancements in Cm have been observed compared with single pulse interaction.
This paper will discuss the laser conditions for producing efficient thrust on debris. In order to obtain high thrust for given laser energies, thermal energies dissipated into laser ablation and debris bulk have to be minimized. It was suggested that this minimization can be achieved by using ultrashort pulse interactions where laser pulse duration is too short for thermal conduction to take place deep into debris. The results of momentum coupling coefficients measured with ps and ns pulse duration will be presented.
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