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Journal Articles

High spatiotemporal-quality petawatt-class laser system

Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya; Sasao, Hajime; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Okada, Hajime; Kondo, Shuji; et al.

Applied Optics, 49(11), p.2105 - 2115, 2010/04

 Times Cited Count:39 Percentile:86.23(Optics)

We have developed a femtosecond high intensity laser system, which combines both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric chirped-pulse amplification (OPCPA) techniques, that produces more than 30-J broadband output energy, indicating the potential for achieving peak powers in excess of 500-TW. With a cleaned high-energy seeded OPCPA preamplifier as a front-end in the system, for the compressed pulse without pumping the final amplifier we found that the temporal contrast in this system exceeds 10$$^{10}$$ on the sub-nanosecond timescales, and is near 10$$^{12}$$ on the nanosecond timescale prior to the peak of the main femtosecond pulse. Using diffractive optical elements for beam homogenization of 100-J level high-energy Nd:glass green pump laser in a Ti:sapphire final amplifier, we have successfully generated broadband high-energy output with a near-perfect top-hat-like intensity distribution.

Journal Articles

Electron optical injection with head-on and countercrossing colliding laser pulses

Kotaki, Hideyuki; Daito, Izuru; Kando, Masaki; Hayashi, Yukio; Kawase, Keigo; Kameshima, Takashi*; Fukuda, Yuji; Homma, Takayuki; Ma, J.*; Chen, L. M.*; et al.

Physical Review Letters, 103(19), p.194803_1 - 194803_4, 2009/11

 Times Cited Count:52 Percentile:88.18(Physics, Multidisciplinary)

Journal Articles

Experimental studies of the high and low frequency electromagnetic radiation produced from nonlinear laser-plasma interactions

Kando, Masaki; Pirozhkov, A. S.; Fukuda, Yuji; Esirkepov, T. Z.; Daito, Izuru; Kawase, Keigo; Ma, J. L.*; Chen, L. M.*; Hayashi, Yukio; Mori, Michiaki; et al.

European Physical Journal D, 55(2), p.465 - 474, 2009/09

 Times Cited Count:17 Percentile:64.98(Optics)

Nonlinear interaction of intense laser beams with plasma causes a number of different regimes of generation of high energy particle beams and of strong radiation with the emitted photon energy from the X-ray to THz frequency range. The review of the first proof-of-principle experiment and the latest progress on the flying mirror is presented. A low frequency EM radiation emission has also been observed in our experiments. The interpretation invokes the relativistic electromagnetic solitons. The solitons are formed in an underdense plasma in the process of the laser pulse frequency downshift. They store a portion of EM wave energy with the polarization inherited from the laser and emit it at the plasma-vacuum interface in a form of the low frequency EM bursts. We present the results of the polarization-resolved measurements.

Journal Articles

Elongation of plasma channel for electron acceleration

Chen, L.-M.; Nakajima, Kazuhisa; Hong, W.*; Hua, J. F.*; Kameshima, Takashi; Kotaki, Hideyuki; Sugiyama, Kiyohiro*; Wen, X.*; Wu, Y.*; Tang, C.*; et al.

Chinese Optics Letters, 5(S1), p.S133 - S135, 2007/05

Journal Articles

Recent progress on the development and analysis of the ITPA global H-mode confinement database

McDonald, D. C.*; Cordey, J. G.*; Thomsen, K.*; Kardaun, O. J. W. F.*; Snipes, J. A.*; Greenwald, M.*; Sugiyama, L.*; Ryter, F.*; Kus, A.*; Stober, J.*; et al.

Nuclear Fusion, 47(3), p.147 - 174, 2007/03

 Times Cited Count:44 Percentile:29.82(Physics, Fluids & Plasmas)

This paper describes the updates to and analysis of the International Tokamak Physics Activity (ITPA) Global H-node Confinement Database version 3 (DB3) over the period 1994-2004. Global data, for the energy confinement time and its controlling parameters, have now been collected from 18 machines of different sizes and shapes: ASDEX, ASDEX Upgrade, C-Mod CoMPASS-D, DIII-D, JET, JFT-2M, JT-60U, MAST, NSTX, PBX-M, PDX, START, T-10, TCV, TdeV, TFTR and TUMAN-3M. A wide range of physics studies has been performed on DB3 with particular progress made in the separation of core and edge behavior, dimensionless parameter analyses and the comparison of the database with one-dimensional transport code. A key aim of the database has always been to provide a basis for estimating the energy confinement properties of next step machines such as ITER, and so the impact of the database and its analysis on such machines is also discussed.

Journal Articles

Scaling of the energy confinement time with $$beta$$ and collisionality approaching ITER conditions

Cordey, J. G.*; Thomsen, K.*; Chudnovskiy, A.*; Kardaun, O. J. W. F.*; Takizuka, Tomonori; Snipes, J. A.*; Greenwald, M.*; Sugiyama, L.*; Ryter, F.*; Kus, A.*; et al.

Nuclear Fusion, 45(9), p.1078 - 1084, 2005/09

 Times Cited Count:51 Percentile:84.74(Physics, Fluids & Plasmas)

The condition of the latest version of the ELMy H-mode database has been re-examined. It is shown that there is bias in the ordinary least squares regression for some of the variables. To address these shortcomings three different techniques are employed: (a)principal component regression, (b)an error in variables technique and (c)the selection of a better conditioned dataset with fewer variables. Scalings in terms of the dimensionless physics valiables, as well as the standard set of engineering variables, are derived. The new scalings give a very similar performance for existing scalings for ITER at the standard beta, but a much improvement performance at higher beta.

Journal Articles

The Spectrum and laser properties of ytterbium doped phosphate glass at low temperature

Dai, S.*; Sugiyama, Akira; Hu, L.*; Liu, Z.*; Huang, G.*; Jiang, Z.*

Journal of Non-Crystalline Solids, 311(2), p.138 - 144, 2002/11

Low-temperature absorption and fluorescence spectra of the Yb3+ ions were measured in phosphate glass with compositions of (60-65)P$$_{2}$$O$$_{5}$$-(4-8)B$$_{2}$$O$$_{3}$$-(5-10)Al$$_{2}$$O$$_{3}$$-(10-15)K$$_{2}$$O-(5-10)BaO-(0-2)La$$_{2}$$O$$_{3}$$-(0-2)Nb$$_{2}$$O$$_{5}$$-(4-87)Yb$$_{2}$$O$$_{3}$$ in mol-%. Temperature dependence of lifetime from $$^{2}$$F$$_{5/2}$$ upper level of YB$$^{3+}$$ was investigated with a cryostat. The glass laser performance pumped by 940 nm laser diode was measured at different temperature range. At 8 K, glass laser oscillation had a slope efficiency of 4% and a maximum power of 2 mW at the peak laser wavelength of 1001 nm.

Journal Articles

Study of a new ytterbium doped phosphate laser glass

Dai, S.*; Hu, L.*; Sugiyama, Akira; Izawa, Yasukazu*; Liu, Z.*; Jiang, Z.*

Chinese Science Bulletin, 47(3), p.255 - 259, 2002/02

 Times Cited Count:7 Percentile:52.85(Multidisciplinary Sciences)

A new type of ytterbium doped phosphate laser glass has been produced and studied about physical and optical properties such as thermo-mechanical properties, nonlinear properties, crystalline phase, micro defects and spectroscopic properties. In the glass forming process, newly developed OH removing technology was adopted. From the reduction of OH concentration in the glass, upper state fluorescence lifetime reached 2.2 ms. Additionally, the glass shows remarkable athermal property of 0.42$$times$$10E$$^{-6}$$/K, which is around one-tenth of QX/Yb glass.

Journal Articles

Elastic and inelastic scattering of $$^{58}$$Ni+$$^{90,94}$$Zr

Sugiyama, Yasuharu; Napoli, D. R.*; A.M.Stefanini*; L.Corradi*; C.Signorini*; F.Scarlassara*; *; Ikezoe, Hiroshi; *; *; et al.

European Physical Journal A, 4(2), p.157 - 164, 1999/00

 Times Cited Count:1 Percentile:10.62(Physics, Nuclear)

no abstracts in English

Oral presentation

Plasma density profile measurement of discharged capillary for laser electron acceleration

Kameshima, Takashi; Kotaki, Hideyuki; Kando, Masaki; Daito, Izuru; Kawase, Keigo; Fukuda, Yuji; Chen, L. M.; Faenov, A. Y.; Pikuz, T. A.*; Homma, Takayuki; et al.

no journal, , 

In recent years, It is noted to use of discharge capillary for laser plasma electron acceleration in order to solve the limit owing to laser focal distance. As the higher plasma density is, the lower the refraction index is, laser propagetes into and interacts plasma, keeping its focal size because discharge plasma behaves like optical fiber. This tequnique would make acceleration space much longer, compared to conventional method with several mm length. This time, we measured plasma density profile inside capillary in order to research optimum distribution of the refraction index, which is very important for R&D of capillary. Here, we will talk about the experimental result.

Oral presentation

Ablative capillary discharge for laser plasma electron acceleration

Kameshima, Takashi; Kotaki, Hideyuki; Kando, Masaki; Daito, Izuru; Kawase, Keigo; Fukuda, Yuji; Chen, L. M.; Homma, Takayuki; Kondo, Shuji; Bulanov, S. V.; et al.

no journal, , 

Recently, it is noticed to generate plasma by using capillary discharge in order to solve a limit due to focal distance of laser, which is one of problems in laser plasma electron acceleration. Since the higher its plasma density, the lower plasma refraction index is, a laser propagates in plasma with its focal size kept and interacts plasma in same principle of optical fiber by distributing plasma as its outside is more dense than its inside. In 2006, KEK, JAEA, and Chinese Academy Engineering Physics(CAEP) carried out a collaboration experiment, where we succeed in generating 560MeV electron beam by using discharge capillary. The result will be informed.

Oral presentation

Ablative capillary discharge for laser plasma electron acceleration

Kameshima, Takashi; Kotaki, Hideyuki; Kando, Masaki; Daito, Izuru; Kawase, Keigo; Fukuda, Yuji; Chen, L. M.; Homma, Takayuki; Kondo, Shuji; Bulanov, S. V.; et al.

no journal, , 

Recently, it is noticed to use discharge capillary for removing an acceleration length limit due to laser focus, which is one of problems to solve in laser plasma electron acceleration. Inside discharge plasma, laser propagates with its initial spot size kept and interacts plasma because the plasma distribution has the same refraction structure as optical fiber. In 2006, KEK, JAEA and Chinese Academy Engineering Physics (CAEP) carried out collaboration experiment. We succeeded the production of 560MeV electron beam by using discharge capillary. The experimental result will be reported.

Oral presentation

Improvement of the stability of the laser accelerated electron beam by using colliding laser pulses

Kotaki, Hideyuki; Daito, Izuru; Kando, Masaki; Hayashi, Yukio; Kawase, Keigo; Kameshima, Takashi; Fukuda, Yuji; Homma, Takayuki; Ma, J.*; Chen, L. M.*; et al.

no journal, , 

no abstracts in English

Oral presentation

Laser electron acceleration in cm-scale capillary-discharge plasma channel

Kameshima, Takashi; Kotaki, Hideyuki; Kando, Masaki; Daito, Izuru; Kawase, Keigo; Fukuda, Yuji; Chen, L. M.*; Homma, Takayuki; Kondo, Shuji; Esirkepov, T. Z.; et al.

no journal, , 

The acceleration method of laser plasma electron acceleration has very strong electric field, however, the acceleration length is veryshort. Hence, the energy gain of electron beams were confined to be approximately 100 MeV. Recently, this problem was solved by using discharge capillary. The feature of plasma was used that high dense plasma has low refractive index. Distributing plasma inside capillary as low dense plasma is in the center of capillary and high dense plasma is in the external side of capillary can make a laser pulse propaget inside capillary with initial focal spot size. Experiments with capillary were performed in China Academy of Engineering Physics (CAEP) and Japan Atomic Energy Agency (JAEA). We obtained the results of 4.4 J laser pulse optical guiding in 4 cm capillary and 0.56 GeV electron production in CAEP in 2006, and 1 J laser pulse optical guiding in 4 cm capillary and electron beams productions.

Oral presentation

Improvement of the stability of laser accelerated electron bunch using counter-crossing and head-on laser pulses

Kotaki, Hideyuki; Daito, Izuru; Kando, Masaki; Hayashi, Yukio; Kawase, Keigo; Kameshima, Takashi; Fukuda, Yuji; Homma, Takayuki; Ma, J.*; Chen, L. M.*; et al.

no journal, , 

15 (Records 1-15 displayed on this page)
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