Dual nanoprecipitation and nanoscale chemical heterogeneity in a secondary hardening steel for ultrahigh strength and large uniform elongation

Wang, S.*; Wang, J.*; Zhang, S.*; Wei, D.*; Chen, Y.*; Rong, X.*; Gong, W.; Harjo, S.; Liu, X.*; Jiao, Z.*; et al.

Journal of Materials Science & Technology, 185, p.245 - 258, 2024/06

https://doi.org/10.1016/j.jmst.2023.10.048

Nanoprecipitates and nanoscale retained austenite (RA) with suitable stability play crucial roles in determining the yield strength (YS) and ductility of ultrahigh strength steels (UHSSs). However, owing to the kinetics incompatibility between nanoprecipitation and austenite reversion, it is highly challenging to simultaneously introduce high-density nanoprecipitates and optimized RA in UHSSs. In this work, through the combination of austenite reversion treatment (ART) and subsequent flash austenitizing (FA), nanoscale chemical heterogeneity was successfully introduced into a low-cost UHSS prior to the aging process. This chemical heterogeneity involved the enrichment of Mn and Ni in the austenite phase. The resulting UHSS exhibited dual-nanoprecipitation of Ni(Al,Mn) and (Mo,Cr) C and nanoscale austenite stabilized via Mn and Ni enrichment. The hard martensitic matrix strengthened by high-density dual-nanoprecipitates constrains the plastic deformation of soft RA with a relatively low fraction, and the presence of relatively stable nanoscale RA with adequate Mn and Ni enrichment leads to a marginal loss in YS but keeps a persistent transformation-induced plasticity (TRIP) effect. As a result, the newly-developed UHSS exhibits an ultrahigh YS of 1.7 GPa, an ultimate tensile strength (UTS) of 1.8 GPa, a large uniform elongation (UE) of 8.5 percent, and a total elongation (TE) of 13 percent. The strategy of presetting chemical heterogeneity to introduce proper metastable phases before aging can be extended to other UHSSs and precipitation-hardened alloys.

J-PARC Linac and RCS; Operational status and upgrade plan to 2 MW

山本 風海; 守屋 克洋; 沖田 英史; 山田 逸平; 地村 幹; Saha, P. K.; 菖蒲田 義博; 田村 文彦; 山本 昌亘; 森下 卓俊; et al.

Journal of Neutron Research, 26(2-3), p.59 - 67, 2024/01

https://doi.org/10.3233/JNR-240003

J-PARC Linacおよび3GeVシンクロトロン(RCS)は、1MWの大強度ビームを中性子実験施設および主リングシンクロトロンに供給するために運転している。これまで進めてきたビーム調整および機器改良により、当初想定よりもはるかに低いビームロス量で1MWのビーム運転を行うことが出来ている。現在のビーム出力はビームロスではなくRCSの高周波加速空胴の電源容量によって制限されている。近年、RCSグループではより少ない消費電力でビームを加速することのできる新しい構造の加速空胴の開発に成功した。この空胴によって、利用運転中に加速空胴で消費される電力を大幅に削減することが出来、さらに1MW以上の大出力での運転も可能となる。これまでの試験結果から、RCSの加速空胴を全て新しい物へ更新すれば、1.5MW以上の大出力も可能となる事が判っている。今後、中性子利用および主リングシンクロトロンの更なる成果創出のため、2MWを目標にRCSで必要な改良について検討を行った。その結果、高周波空胴の更新以外にも、高周波増幅器の増強やビームモニタの増強が必要であることが判ったため、今後順次更新を進める。

Laser stripping for 1.3 GeV H beam at the SNS

Gorlov, T.*; Aleksandrov, A.*; Cousineau, S.*; Liu, Y.*; Oguz, A. R.*; Kay, M.*; Saha, P. K.

Proceedings of the 2022 North American Particle Accelerator Conference (NAPAC 2022) (Internet), p.702 - 704, 2022/08

https://doi.org/10.18429/JACoW-NAPAC2022-WEPA33

The conventional method of H charge-exchange injection by using a solid stripper foil has serious drawbacks such as, a short foil lifetime, unexpected failure and moreover a high residual radiation due to uncontrolled foil scattering beam losses at high-intensity operation. To overcome all those issues, an H stripping by using only lasers or by laser assisted are being extensively studied at J-PARC and the Spallation Neutron Source (SNS) at Oak Ridge, USA, respectively. However, a reduction of the laser power to realize the laser stripping is a common issue at both labs. In this research, different schemes and methods of laser stripping, especially for an effective excitation of the ground state hydrogen atom are considered. Among all methods the most realistic and practical scheme seems to be the sequential excitation scheme by using two types of laser. In this case, a laser power can be reduced to 1/25 as compared to a single step excitation. Due to a lower H energy, a deep UV laser is used at J-PARC. Such a reduction of the laser power is further useful for a realistic implementation.

Studies of laser power reduction for the laser stripping of 400 MeV beam at J-PARC RCS

Saha, P. K.; 原田 寛之; 金正 倫計; 米田 仁紀*; 道根 百合奈*; 渕 葵*; 佐藤 篤*; Liu, Y.*

JPS Conference Proceedings (Internet), 33, p.011025_1 - 011025_7, 2021/03

BB2019-1158.pdf:0.7MB

https://doi.org/10.7566/JPSCP.33.011025

We proposed and also preparing for a POP (Proof-of-Principle) demonstration of a completely non-destructive H stripping method by using only lasers at J-PARC. To reduce the laser power, which is one of the critical issues in this case, we have studied an extensive manipulations of the H beam as well advanced uses of the lasers in this research. These includes utilizing a dispersion derivative of the H beam to cope with its large momentum spread, while multi-pass laser system to utilize multiple interactions of the H beam with lasers. We have estimated that the laser power can be reduced to more than one order of magnitude by applying a combination of these two methods. The detail simulation and experimental results of the H beam manipulations as well as development status of the multi-pass laser system are presented in this paper.

Super-absorbent polymer valves and colorimetric chemistries for time-sequenced discrete sampling and chloride analysis of sweat via skin-mounted soft microfluidics

Kim, S. B.*; Zhang, Y.*; Won, S. M.*; Bandodkar, A. J.*; 関根 由莉奈; Xue, Y.*; Koo, J.*; Harshman, S. W.*; Martin, J. A.*; Park, J. M.*; et al.

Small, 14(12), p.1703334_1 - 1703334_11, 2018/03

https://doi.org/10.1002/smll.201703334

This paper introduces super absorbent polymer valves and colorimetric sensing reagents as enabling components of soft, skin-mounted microfluidic devices designed to capture, store and chemically analyze sweat released from eccrine glands. The valving technology enables robust means for guiding the flow of sweat from an inlet location into a collection of isolated reservoirs, in a well-defined sequence. Analysis in these reservoirs involves a color responsive indicator of chloride concentration with a formulation tailored to offer stable operation with sensitivity optimized for the relevant physiological range. Evaluations on human subjects with comparisons against ex situ analysis illustrate the practical utility of these advances.

Status of proof-of-principle experiment for 400 MeV H stripping to protons by using only lasers in the 3-GeV RCS of J-PARC

Saha, P. K.; 原田 寛之; 山根 功*; 金正 倫計; 三浦 昭彦; 岡部 晃大; Liu, Y.*; 吉本 政弘; 加藤 新一; 入江 吉郎*

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (インターネット), p.866 - 870, 2017/12

http://www.pasj.jp/web_publish/pasj2017/proceedings/PDF/WEP0/WEP024.pdf

The conventional H stripping injection by using solid stripper foil has serious issues not only because of high residual radiation at injection area due to uncontrolled beam losses caused by the foil and beam interaction, but also for the short lifetime, especially in high intensity accelerators. In order to overcome those issues, we proposed an alternative method of H stripping by using only lasers. Experimental study for a POP (proof-of-principle) demonstration of the present principle is under preparation for 400 MeV H stripping in the 3-GeV RCS of J-PARC. The studies of laser beam itself and also the H beam optimization studies to match with given laser pulses are in progress, where the first interaction of the H beam and the laser is planned to perform in this fiscal year. The status and detail strategy of the present research are summarized in this work.

Theoretical elucidation of space charge effects on the coupled-bunch instability at the 3 GeV Rapid Cycling Synchrotron at the Japan Proton Accelerator Research Complex

菖蒲田 義博; Chin, Y. H.*; Saha, P. K.; 發知 英明; 原田 寛之; 入江 吉郎*; 田村 文彦; 谷 教夫; 外山 毅*; 渡辺 泰広; et al.

Progress of Theoretical and Experimental Physics (Internet), 2017(1), p.013G01_1 - 013G01_39, 2017/01

AA2016-0375.pdf:3.07MB

https://doi.org/10.1093/ptep/ptw169

大強度のビームを加速すると、一般にビームは不安定になることが知られている。それは、周回中のビームと加速器の機器には電磁相互作用(ビームのインピーダンス)があるからである。ビームを不安定にならないようにするためには、ビームのインピーダンスが閾値を超えなければ良いことが分かっていて、それは、インピーダンスバジェットと呼ばれている。J-PARC 3GeVシンクロトロンは、キッカーというビームを蹴り出す装置がインピーダンスバジェットを破っていることが、建設初期の段階から明らかにされており、1MWビームの達成を阻害することが懸念されてきた。今回、ビームの構成粒子自身の電荷に由来する電磁相互作用(空間電荷効果)には、ビームを安定化させる効果があることを理論的に明らかにした。また、ビームのパラメータや加速器のパラメータを適切に選べば、J-PARC 3GeVシンクロトロンのような低エネルギーのマシーンでは、従来のインピーダンスバジェットを破ることは、1MWビームを達成する上で致命傷にはならないことを実験的にも実証した。

Temporal changes of radiocesium in irrigated paddy fields and its accumulation in rice plants in Fukushima

Yang, B.*; 恩田 裕一*; 脇山 義史*; 吉村 和也; 関本 均*; Ha, Y.*

Environmental Pollution, 208(Part B), p.562 - 570, 2016/01

https://doi.org/10.1016/j.envpol.2015.10.030

In this study, we investigated the temporal changes of radiocesium in soil, irrigation water, and rice plant in two adjacent rice paddies, with and without surface-soil-removal practice, in Fukushima Prefecture for over three years (2012 to 2014). Our results showed that radiocesium migrated into 24-28 cm soil layers and that the concentration and inventory of radiocesium in paddy soils generally decreased. The newly added radiocesium to paddies through irrigation water contributed only the maximum values of 0.15% and 0.75% of the total amount present in normal and decontaminated paddies, respectively, throughout the study period. The change trend of radiocesium concentration in suspended sediment in irrigation water exponentially decreased. Radiocesium accumulation in rice plant also decreased with time in both paddies. However, the transfer factor of radiocesium for rice plant in the decontaminated paddy increased compared with normal paddy.

The Kicker impedance and its effect on the RCS in J-PARC

菖蒲田 義博; Saha, P. K.; 外山 毅*; 山本 昌亘; Chin, Y. H.*; 入江 吉郎*

Proceedings of 54th ICFA Advanced Beam Dynamics Workshop on High-Intensity, High Brightness and High Power Hadron Beams (HB 2014) (Internet), p.369 - 373, 2015/03

http://epaper.kek.jp/HB2014/papers/tho2ab02.pdf

http://epaper.kek.jp/HB2014/talks/tho2ab02_talk.pdf

Measurements demonstrate that the kicker impedance dominates along the RCS. Based on a newly developed theory, the impedance is measured by observing the beam-induced voltages at the ends of power cable of the kicker. Toward one mega-watt goal, it is essential to take advantage of tune manipulations and the space charge damping effect. We propose the reduction scheme of the kicker impedance by attaching the resistors combined with four diodes in parallel at the ends of the kicker cables, to pursue the ultimate goal at the RCS.

Anisotropic two-dimensional electron gas at the LaAlO/SrTiO (110) interface

Annadi, A.*; Zhang, Q.*; Renshaw Wang, X.*; Tuzla, N.*; Gopinadhan, K.*; L, W. M.*; Roy Barman, A.*; Liu, Z. Q.*; Srivastava, A.*; Saha, S.*; et al.

Nature Communications (Internet), 4, p.1838_1 - 1838_7, 2013/05

https://doi.org/10.1038/ncomms2804

We report the observation of unexpected conductivity at the LaAlO/SrTiO interface prepared on (110)-oriented SrTiO, with a LaAlO-layer thickness-dependent metal-insulator transition. Density functional theory calculation reveals that electronic reconstruction, and thus conductivity, is still possible at this (110) interface by considering the energetically favourable (110) interface structure, that is, buckled TiO/LaO, in which the polarization discontinuity is still present. The conductivity was further found to be strongly anisotropic along the different crystallographic directions with potential for anisotropic superconductivity and magnetism, leading to possible new physics and applications.