Toshiyuki Shizuma

Proton acceleration to 40 MeV using a high intensity, high contrast optical parametric chirped-pulse amplification/Ti:sapphire hybrid laser system.

Using a high-contrast (10(10):1) and high-intensity (10(21) W/cm(2)) laser pulse with the duration of 40 fs from an optical parametric chirped-pulse amplification/Ti:sapphire laser, a 40 MeV proton bunch is obtained, which is a record for laser pulse with energy less than 10 J. The efficiency for generation of protons with kinetic energy above 15 MeV is 0.1%.

Nondestructive Detection of Heavily Shielded Materials by Using Nuclear Resonance Fluorescence with a Laser-Compton Scattering γ-ray Source

We perform a proof-of-principle experiment for a nondestructive method for detecting the elemental and isotopic composition of materials concealed by heavy shields such as iron plates with a thickness of several centimeters. This method uses nuclear resonance fluorescence (NRF) triggered by an energy-tunable laser-Compton scattering (LCS) γ-ray source. One-dimensional mapping of a lead block hidden behind 1.5-cm-thick iron plates is obtained by measuring an NRF γ-ray of a lead isotope 208Pb. We observe a 5512-keV γ-ray from 208Pb excited by the quasi-monochromatic LCS γ-rays with energies up to 5.7 MeV. The edge position of the lead block is consistent with the exact position within the uncertainty.

Evidence for nucleosynthesis in the supernova gamma process: universal scaling for p nuclei.

Analyzing the solar system abundance, we find two universal scaling laws concerning the p and s nuclei. They indicate that the gamma process in supernova (SN) explosions is the most probable origin of the p nuclei that has been discussed with many possible nuclear reactions and sites in about 50 years. In addition, the scalings lead to new concepts: a universality of the gamma process and a new nuclear cosmochronometer. We carry out gamma-process nucleosynthesis calculations for typical core-collapse SN explosion models, and the results satisfy the observed scalings.

First demonstration of energy-recovery operation in the JAERI superconducting linac for a high-power free-electron laser

An energy-recovery linac (ERL) for a high-power free-electron laser (FEL) has been designed and constructed at Japan Atomic Energy Research Institute (JAERI). The construction of the ERL was completed and first energy-recovery operation and first FEL lasing have been demonstrated. We present the design overview and the performance of the JAERI-ERL. Future plans towards a 10-kW FEL are also described.

Photodisintegration cross section measurements on {sup 186}W, {sup 187}Re, and {sup 188}Os: Implications for the Re-Os cosmochronology

Cross sections of the {sup 186}W, {sup 187}Re, {sup 188}Os({gamma},n) reactions were measured using quasimonochromatic photon beams from laser Compton scattering with average energies from 7.3 to 10.9 MeV. The results are compared with the predictions of Hauser-Feshbach statistical calculations using four different sets of input parameters. In addition, the inverse neutron capture cross sections were evaluated by constraining the model parameters, especially the E1 strength function, on the basis of the experimental data. The present experiment helps to further constrain the correction factor F{sub {sigma}} for the neutron capture on the 9.75 keV state in {sup 187}Os. Implications of F{sub {sigma}} for the Re-Os cosmochronology are discussed with a focus on the uncertainty in the estimate of the age of the galaxy.

Sub-MeV tunably polarized X-ray production with laser Thomson backscattering

Reported in this article is the generation of unique polarized x-rays in the sub-MeV region by means of the Thomson backscattering of the Nd:YAG laser photon with a wavelength of 1064 nm on the 150 MeV electron from the microtron accelerator. The maximum energy of the x-ray photons is estimated to be about 400 keV. The total energy of the backscattered x-ray pulse is measured with an imaging plate and a LYSO scintillator. The angular divergence of the x-rays is also measured by using the imaging plate. We confirm that the x-ray beam is polarized according to the laser polarization direction with the Compton scattering method. In addition, we demonstrate the imaging of the object shielded by lead with the generated x-rays.

Nondestructive detection of hidden chemical compounds with laser Compton-scattering gamma rays

A nondestructive assay method for measuring a shielded chemical compound has been proposed. The chemical compound is measured by using a nuclear resonance fluorescence (NRF) measurement technique with an energy tunable laser Compton-scattering (LCS) gamma-ray source. This method has an advantage that hidden materials can be detected through heavy shields such as iron plates of a thickness of several centimeters. A detection of a chemical compound of melamine, C(3)H(6)N(6), shielded by 15-mm-thick iron and 4-mm-thick lead plates is demonstrated. The NRF gamma-rays of (12)C and (14)N of the melamine are measured by using the LCS gamma-rays of the energies of up to 5.0 MeV. The observed ratio ((12)C/(14)N)(exp)=0.39+/-0.12 is consistent with (C/N)(melamine)=0.5.

Electromagnetic structure of 98Mo

Abstract The nucleus 98 Mo was multiply Coulomb excited using 20 Ne, 84 Kr and 136 Xe beams. Eighteen E2 and M1 reduced matrix elements connecting 7 low-lying levels have been determined using the least-squares code GOSIA. The results are compared with the predictions of an extended version of the IBM1 model. The quadrupole sum rules approach was used to determine the shape parameters in two 0 + (ground and first excited) states. The rotational invariants 〈Q 2 〉 and 〈 cos 3δ〉 obtained show the shape coexistence in 98 Mo nucleus: the triaxial ground state and the prolate first excited state.

Proton-induced Nuclear Reactions Using Compact High-Contrast High-Intensity Laser

A multi-MeV proton beam driven by a compact laser with an intensity of ?1020 W/cm2 is used to induce the nuclear reaction 11B(p,n)11C. The total activity of 11C produced after 60 shots of laser irradiation is found to be 11.1?0.4 Bq. The possibility of thin layer activation (TLA) analysis using a high-intensity ultrashort-pulse laser is discussed.

New s-process path and its implications for a 187Re-187Os nucleo-cosmochronometer

We study a new s-process path through an isomer of 186Re to improve a 187Re-187Os nucleo-cosmochronometer. The nucleus 187Re is produced by this new path of 185Re(n, γ)186Rem(n, γ)187Re. We measure a ratio of neutron-capture cross sections for the 185Re(n, γ)186Rem and 185Re(n, γ)186Reg reactions at thermal neutron energy because the ratio with the experimental uncertainty has not been reported. Using an activation method with reactor neutrons, we obtain the ratio of Rth = 0.54% ± 0.11%. From this ratio we estimate the ratio of Maxwellian-averaged cross sections in a typical s-process environment at kT = 30 keV with the help of the temperature dependence given in a statistical-model calculation because the energy dependence of the isomer/ground ratio is smaller than the absolute neutron-capture cross section. The ratio at kT = 30 keV is estimated to be Rst = 1.3% ± 0.8%. We calculate the s-process contribution from the new path in a steady-flow model. The additional abundance of 187Re through this path is estimated to be Ns = 0.56% ± 0.35% relative to the abundance of 186Os. This additional increase of 187Re does not make any remarkable change in the 187Re-187Os chronometer for an age estimate of a primitive meteorite, which has recently been found to be affected strongly by a single supernova r-process episode.