We review a number of instruments employed in a high-intensity J-KAREN-P laser-solid interaction experiment and discuss the applicability of the diagnostics to the best target position determination with a ~10 μm accuracy, while the focal spot size was ~1 μm and peak intensity was up to 7×1021 W/cm2. We discuss both front- and back-side diagnostics, some of them operated in the infrared, visible and ultraviolet ranges, while others in the extreme ultraviolet, soft X-ray and gamma-ray ranges. We found that the applicability of some of the instruments to the best at-focus target position determination depends on the thickness of the target.
We report on the J-KAREN-P laser facility at QST, which can provide PW peak power at 0.1 Hz on target. The system
can deliver short pulses with an energy of 30 J and pulse duration of 30 fs after compression with a contrast level of
better than 1012. Such performance in high field science will give rise to the birth of new applications and breakthroughs,
which include relativistic particle acceleration, bright x-ray source generation, and nuclear activation. The current
achieved laser intensity on target is up to > 9x1021 Wcm-2 with an energy of ~9 J on target. The interaction with a 3 to 5-
μm stainless steel tape target provides us electrons with a typical temperature of more than 10 MeV and energetic proton
beams with typical maximum energies of > 40 MeV with good reproducibility. The protons are accelerated in the Target
Normal Sheath Acceleration regime, which is suitable for many applications including as an injector into a beamline for
medical use, which is one of our objectives.
Experimental demonstration of multi-charged heavy ion acceleration from the interaction between the ultra-intense short pulse laser system and the metal target is presented. The laser pulse of <10 J laser energy, 36 fs pulse width, and the contrast level of ~1010 from 200 TW class Ti:sapphire J-KAREN laser system at JAEA is used in the experiment. Almost fully stripped Fe ions accelerated up to 0.9 GeV are demonstrated. This is achieved by the high intensity laser field of ∼ 1021Wcm−2 interacting with the solid density target. The demonstrated iron ions with high charge to mass ratio (Q/M) is difficult to be achieved by the conventional heavy ion source technique in the accelerators.
We demonstrate a new ion diagnosis method for high energy ions by utilizing a combination of a single CR-39 detector and plastic plates, which enables to detect high energy ions beyond the detection threshold limit of the CR-39. This detection method coupled with a magnetic spectrometer is applied to identify high energy ions of 50 MeV per nucleon in laser-driven ion acceleration experiments using cluster-gas targets.
Review of results, obtained by using recently proposed new imaging detector, based on formation of color centers in LiF
crystal and LiF film, for in situ high performance measurements of near-field and far-field properties of soft X-ray lasers
(SXRL) beams is presented. Experiments have been carried out with laser-driven transient-collision plasma SXRL and
free electron SXRL beams. It was demonstrated that due to favorable combination of high spatial resolution, high
dynamic range and wide field of view this technique allows measuring not only intensity distribution across the full
beam and in local areas, but also permits to evaluate coherence and spectral distribution of radiation across the beam.
Experimental diffraction patterns in the images of periodical structures are analyzed by comparison with the modeled
ones in the last case. The estimated accuracy of measurements is between 10-20%.
M. Nishiuchi, K. Ogura, A. Pirozhkov, T. Tanimoto, A. Yogo, H. Sakaki, T. Hori, Y. Fukuda, M. Kanasaki, A. Sagisaka, M. Tampo, H. Kiriyama, T. Shimomura, K. Kondo, S. Kawanishi, C. Brenner, D. Neely
KEYWORDS: Aluminum, Laser systems engineering, Skin, Laser therapeutics, Electrons, Ions, Medical laser equipment, Laser applications, Particles, Current controlled current source
This paper presents the experimental investigation of laser-driven proton acceleration using a table top Ti:Sapphire laser system interacting with the thin-foil targets during the course of medical
application of the laser-driven proton beam.
The proton beam with maximum energy of upto 14~MeV is generated in 60 TW mode.
The number of protons at ~10 MeV is estimated to be over 105 proton/sr/MeV/shot with
beam having half divergence angle of 5~degree.
If 10 Hz operation is assumed 2 Gy dose is possible to irradiate during 10 min onto a ~1 mm tumor just under the skin.
In contrast to the previous condition of our apparatus with which we
demonstrated the DNA double-strand breaking by irradiating the laser-driven proton beam onto the
human cancer cells in-vitro test,
the result reported here has significant meaning in the sense that
pre-clinical in-vivo test can be started by irradiating the laser-driven proton beam
onto the skin of the mouse, which is unavoidable step before the real radiation therapy.
The paper is devoted to experimental and theoretical studies of ablation of condensed matter by optical (OL),
extreme ultraviolet (EUV) and X-ray lasers (XRL). Results obtained at two different XRL are compared. The
first XRL is collision Ag-plasma laser with pulse duration τL = 7 ps and energy of quanta hv=89.3 eV, while
the second one is EUV free electron laser (EUV-FEL) and has parameters τL = 0.3 ps and energy of quanta 20.2
eV. It is shown that ablation thresholds for these XRL at LiF dielectric are approximately the same. A theory is
presented which explains slow growth of ablated mass with fluence in case of XRL as a result of transition from
spallative ablation near threshold to evaporative ablation at high fluencies. It is found that the metal irradiated
by short pulse of OL remains in elastic state even in high shear stresses. Material strength of aluminum at very
high deformation rates V/V ~ 109 s-1 is defined.
Electromagnetic wave generation in the extreme ultraviolet (XUV) and infrared (IR) wavelength range occurs
during the interaction of intense short laser pulses with underdense plasmas. XUV pulses are generated through
laser light reflection from relativistically moving electron dense shells (flying mirrors). A proof-of-principle and
an advanced experiment on flying mirrors are presented. Both of the experiments demonstrated light reflection
and frequency upshift to the XUV wavelength range (14-20 nm). The advanced experiment with a head-on
collision of two laser pulses exhibited the high reflected photon number. IR radiation, which is observed in the
forward direction, has the wavelength of 5 μm and dominantly the same polarization as the driving laser. The
source of the IR radiation is attributed to emission from relativistic solitons formed in the underdense plasma.
M. Sherrill, J. Abdallah, G. Csanak, E. Dodd, Y. Fukuda, Y. Akahane, M. Aoyama, N. Inoue, H. Ueda, K. Yamakawa, A. Ya Faenov, A. Magunov, T. Pikuz, I. Yu. Skobelev
A model that solves simultaneously both the electron and atomic kinetics was used to generate synthetic X-ray
spectra to characterize high intensity ultrashort-laser-driven target experiments. A particle-in-cell simulation
was used to model the laser interaction for both cluster and foil targets and provided the initial electron energy
distribution function (EEDF) for a Boltzmann solver. Previously reported success in the spectroscopic characterization
of an irradiated Ar cluster target has motivated the authors to apply this technique in a feasibility study
to assess the possibility of recording time resolved spectra of a 10 micron Ti foil target irradiated by a 500 fs,
I= 1.0 × 1018W/cm2 short-pulse laser. Though this model suggests that both Ar cluster and Ti foil plasmas are
held in a highly non-equilibrium state for both the EEDF and the ion level populations for several picoseconds,
the spectral line features of the foil experiment was shown to evolve too quickly to be seen by current ultrafast
time resolved spectrometers.
High resolution x-ray emission spectra of plasma created by laser irradiation of rare-gas (Ar, Kr, Xe) clusters have been measured at laser intensities over 1019 W/cm2 and 30-fs pulse duration. To make these measurements possible, in addition to the effort to decrease a prepulse intensity using Pockels cell switches, micron-size clusters were produced using a specially designed conical nozzle. The Boltzmann equation and a detailed collisional radiative model are solved simultaneously as a function of time to model the time integrated x-ray spectra of the transient plasma. The results are quantitatively in good agreement with the experimentally observed x-ray emission spectra of Ar clusters.
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