Capturing the non-equilibrium state in light–matter–free-electron interactions through ultrafast transmission electron microscopy

Ultrafast transmission electron microscope(UTEM) with the multimodality of time-resolved diffraction, imaging,and spectroscopy provides a unique platform to reveal the fundamental features associated with the interaction between free electrons and matter. In this review, we summarize the principles, instrumentation, and recent developments of the UTEM and its applications in capturing dynamic processes and non-equilibrium transient states. The combination of the transmission electron microscope with a femtosecond laser via the pump–probe method guarantees the high spatiotemporal resolution, allowing the investigation of the transient process in real, reciprocal and energy spaces. Ultrafast structural dynamics can be studied by diffraction and imaging methods, revealing the coherent acoustic phonon generation and photoinduced phase transition process. In the energy dimension, time-resolved electron energy-loss spectroscopy enables the examination of the intrinsic electronic dynamics of materials, while the photon-induced near-field electron microscopy extends the application of the UTEM to the imaging of optical near fields with high real-space resolution. It is noted that light–free-electron interactions have the ability to shape electron wave packets in both longitudinal and transverse directions, showing the potential application in the generation of attosecond electron pulses and vortex electron beams.

Theoretical study of the enhancement of saturable absorption of Kr under x-ray free-electron laser

The generation of hollow atoms will reduce the probability of light absorption and provide a high-quality diffraction image in the experiment. In this paper, we calculated the ionization rate of the Kr atom under x-ray free-electron laser(XFEL) using Hartree–Fock–Slater model and simulated the ionization model of Kr atom using Monte–Carlo method to determine the response of the hollow atom of Kr atom to the XFEL photon energy. Calculating the correlation between the total photoionization cross-section of the ground state of Kr atom and the photon energy, we determined three particular photon energies of 1.75 ke V, 1.90 ke V, and 14.30 ke V. The dynamics simulation under the experimental condition's17.50 ke V photon energy was achieved by implementing the Monte–Carlo method and calibrating the photon flux modeling parameters. Consequently, our calculated data are more consistent with experimental phenomena than previous theoretical studies. The saturable absorption of Kr at 1.75 ke V, 1.90 ke V, 14.30 ke V, and 17.50 ke V energies was further investigated by using the optimized photon flux model theory. We compared the statistics on main ionization paths under those four specific photon energies and calculated the population changes of various Kr hollow atoms with different configurations.The results demonstrate that the population of hollow atoms produced at the critical ionization photon energy is high. Furthermore, the change of population with respect to position is smooth, which shows a significant difference between the generation mode of ions with low and high photon energies. The result is important for the study of medium-and high-Z element hollow atoms, which has substantial implications for the study of hollow atoms with medium and high charge states, as well as for the scaling of photon energy of free electron lasers.

Leser-Trélat征并发前列腺癌1例

患者男，58岁。因躯干部皮肤起黑褐色斑丘疹20年余．近2个月突然增多来我科就诊。患者诉20年前下腹部长褐色斑丘疹，无明显自觉症状，遂未予治疗。近5年来皮损渐累及胸、背部及双上肢共约二四百个，近2个月突然增加一百多个．原有皮疹亦较前面积增大。发病以来，无发热乏力，精神尚可，饮食正常，大小便正常。

恶性黑棘皮病并发Leser-Trélat征1例

患者男,72岁。全身褶皱部、乳晕肥厚、色素沉着3个月,周身泛发性丘疹伴剧痒2个月。皮肤科情况:颈部、腋窝、腹股沟、肛周皮肤肥厚、色素沉着,呈绒毛状或乳头瘤样增生,双侧乳头和乳晕角化、色素沉着,颈部、躯干及四肢散在米粒至黄豆大肤色至淡褐色角化性丘疹及斑丘疹。皮损组织病理示(上胸部):表皮角化过度,棘层肥厚,乳头瘤样增生,基底层色素增加;(右侧腹股沟):表皮中度角化过度,乳头瘤样增生,乳头似指样向上凸出,棘层中度肥厚,基底层色素增加,真皮浅层少许淋巴细胞浸润。诊断:恶性黑棘皮病并发Leser-Trélat征。

Leser-Trélat征

报告1例Leser-Trélat(莱泽-特雷拉)征并发鼻咽癌。患者男,70岁。30年前躯干部出现脂溢性角化,近3个月胸部皮损突然增多并出现呼吸困难,CT及鼻咽部病灶组织病理检查证实为鼻咽癌。

Development of a high-repetition-rate lumped-inductance kicker magnet prototype for the beam switchyard of SHINE

The Shanghai high-repetition-rate X-ray free-electron laser and extreme light facility(SHINE)operates at a maximum repetition rate of 1 MHz.Kicker magnets are key components that distribute electron bunches into three different undulator lines in a bunch-by-bunch mode.The kicker field width must be less than the time interval between bunches.A lumpedinductance kicker prototype was developed using a vacuum chamber with a single-turn coil.The full magnetic field strength was 0.005 T.This paper presents the requirements,design considerations,design parameters,magnetic field calculations,and measurements of the kicker magnets.The relevant experimental results are also presented.The pulse width of the magnetic field was approximately 600 ns,and the maximum operation repetition rate was 1 MHz.The developed kicker satisfies the requirements for the SHINE project.Finally,numerous recommendations for the future optimization of kicker magnets are provided.

初诊为脂溢性角化病的Leser-Trelat征一例

Leser-Trelat征是指成年人突然出现大量瘙痒性脂溢性角化皮损合并内脏恶性肿瘤的征象。如果脂溢性角化病患者皮损短期内出现体积增大、数量增多并伴瘙痒,常提示内脏肿瘤,应进行相关排癌检查,特别是皮损的表皮生长因子免疫组化分析。本文就1例脂溢性角化病的Leser-Trelat征合并肺癌患者的诊治过程进行报道,以提高临床医师对该病的认识。

恶性黑棘皮病并发Leser-Trélat征

报告1例恶性黑棘皮病并发Leser-Trélat征。患者男,69岁。全身褶皱部位皮肤色素沉着、乳头瘤样增生,伴瘙痒半年。皮肤科检查:颜面部、双侧腹股沟、腋窝、肛周皮肤色素沉着,呈绒毛状或乳头瘤样增生;双眼睑缘和唇红区及颊黏膜乳头瘤样增生。双侧乳头和乳晕角化及色素沉着,颈部、上胸部、腹部及四肢可见米粒至黄豆大疣状角化性丘疹。胃镜检查及胃黏膜组织病理检查示贲门-胃底低分化腺癌。诊断:恶性黑棘皮病并发Leser-Trélat征。

恶性黑棘皮病并发Leser-Trélat征及牛肚掌

报告1例恶性黑棘皮病并发Leser-Trélat征及牛肚掌。患者男,77岁。面部、腋窝变黑7个月,躯干及上肢褐黑色斑丘疹6个月,1年前行胃癌根治性切除术。皮肤科检查:面部、颈部、胸部、背部及双上肢可见200余个米粒至黄豆大圆形或椭圆形扁平褐色斑丘疹。面部及双侧腋窝可见色素沉着,腋下、眶周及唇部乳头瘤样病变,双侧手掌散在粟粒状细小光滑乳头状凸起,呈牛肚掌样外观。皮损组织病理检查:角化过度,棘层肥厚呈乳头瘤样增生,棘层内可见角囊肿。诊断:恶性黑棘皮病并发Leser-Trélat征及牛肚掌。

Review of fully coherent free-electron lasers

Generation of intense, fully coherent radiation with wide spectral coverage has been a long-standing challenge for laser technologies. Several techniques have been developed in recent years to extend the spectral coverage in optical physics, but none of them hold the potential to produce X-ray laser pulses with very high-peak power. Urgent demands for intense X-ray light sources have prompted the development of free-electron lasers(FELs), which have been proved to be very useful tools in many scientific areas. In this paper, we give an overview of the basic principle of FELs, techniques for realizing fully coherent FELs, and the development of fully coherent FEL facilities in China.

Picosecond terahertz pump-probe realized from Chinese terahertz free-electron laser

Electron energy relaxation timeτis one of the key physical parameters for electronic materials.In this study,we develop a new technique to measureτin a semiconductor via monochrome picosecond(ps)terahertz(THz)pump and probe experiment.The special THz pulse structure of Chinese THz free-electron laser(CTFEL)is utilized to realize such a technique,which can be applied to the investigation into THz dynamics of electronic and optoelectronic materials and devices.We measure the THz dynamical electronic properties of high-mobility n-GaSb wafer at 1.2 THz,1.6 THz,and 2.4 THz at room temperature and in free space.The obtained electron energy relaxation time for n-GaSb is in line with that measured via,e.g.,four-wave mixing techniques.The major advantages of monochrome ps THz pump-probe in the study of electronic and optoelectronic materials are discussed in comparison with other ultrafast optoelectronic techniques.This work is relevant to the application of pulsed THz free-electron lasers and also to the development of advanced ultrafast measurement technique for the investigation of dynamical properties of electronic and optoelectronic materials.

ANGULAR SPECTRUM PROPERTY OF SPONTANEOUS EMISSION IN A TWO-DIMENSIONAL UNDULATOR FREE-ELECTRON LASER

The angular spectrum of spontaneous emission in a two-dimensional undulator free-electron laser is analyzed theoretically. Numerical calculation shows that the 3-th harmonic spontaneous emission power density can be greatly enhanced by using a two-dimensional undulator, for which l=s, so the harmonic number can be selected by selecting l. Therefore, the higher harmonic operation of a free-electron laser can be realized selectively.

Synchrotron-Infrared Microscopy Analysis of Amyloid Fibrils Irradiated by Mid-Infrared Free-Electron Laser

Amyloid fibrils are widely recognized as a cause of serious amyloidosis such as Alzheimer’s disease. Although dissociation of amyloid fibril aggregates is expected to lead to a decrease in the toxicity of the fibrils in cells, the fibril structure is robust under physiological conditions. We have irradiated amyloid fibrils with a free-electron laser (FEL) tuned to mid-infrared frequencies to induce dissociation of the aggregates into monomer forms. We have previously succeeded in dissociating fibril structures of a short peptide of the thyroid hormone by tuning the oscillation frequency to the amide I band, but the detailed structural changes of the peptide have not yet been determined at a high spatial resolution. Synchrotron-radiation infrared microscopy (SR-IRM) is a powerful tool for in situ analysis of minute structural changes of various materials, and in this study, the feasibility of SR-IRM for analyzing the microscopic conformational changes of amyloid fibrils after FEL irradiation was investigated. Reflection spectra of the amyloid fibril surface showed that the amide I peaks shifted to higher wave numbers after the FEL irradiation, indicating that the initial β-sheet-rich structure transformed into a mixture of non-ordered and turn-like peptide conformations. This result demonstrates that conformational changes of the fibril structure after the FEL irradiation can be observed at a high spatial resolution using SR-IRM analysis and the FEL irradiation system can be useful for dissociation of amyloid aggregates.

Use of a Mid-Infrared Free-Electron Laser (MIR-FEL) for Dissociation of the Amyloid Fibril Aggregates of a Peptide

Amyloid fibrils are deposited in various tissues in the body, and are linked to the putative causes of serious diseases such as amyloidosis. Although the conditions of the disease would be expected to improve if the fibril structure could be destroyed, the aggregated structure is stable under physiological conditions. Recently, we found that the amyloid fibrils of lysozyme could be refolded into their active form by using a mid-infrared free-electron laser (MIR-FEL) tuned to the amide I band (corresponding to the C=O stretch vibration), with the MIR-FEL having specific oscillation characteristics of a picosecond pulse structure, a tunable wavelength within mid-infrared frequencies, and high photon density. In the study, we tested the usability of the FEL for dissociation of aggregates of pathological amyloid fibrils by using a short peptide of human thyroid hormone. The fibrils (after being placed on a glass slide) were irradiated using the FEL tuned to the amide I band (1644 cm?1), and those in situ were analyzed by Congo-Red assay, scanning-electron microscopy, and transmission-electron microscopy. All of the results obtained using these microscopic analyses indicated that the amyloid fibril formation was considerably decreased by FEL irradiation. Moreover, upon irradiation, a strong fibril peak at the amide I band in the infrared spectrum was transformed into a broad peak. These results imply that the β-sheet-rich structure of the amyloid fibrils changed into non-ordered or unspecified structures after the FEL irradiation. This FEL irradiation system, combined with various analytical methods, shows promise for the dissociation of amyloid aggregates.

The MING proposal at SHINE:megahertz cavity enhanced X‑ray generation

The cavity-based X-ray free-electron laser(XFEL)has promise in producing fully coherent pulses with a bandwidth of a few meV and very stable intensity,whereas the currently existing self-amplified spontaneous emission(SASE)XFEL is capable of generating ultra-short pulses with chaotic spectra.In general,a cavity-based XFEL can provide a spectral brightness three orders of magnitude higher than that of the SASE mode,thereby opening a new door for cutting-edge scientific research.With the development of superconducting MHz repetition-rate XFEL facilities such as FLASH,European-XFEL,LCLS-II,and SHINE,practical cavity-based XFEL operations are becoming increasingly achievable.In this study,megahertz cavity enhanced X-ray generation(MING)is proposed based on China’s first hard XFEL facility-SHINE,which we refer to as MING@SHINE.

On Riemann-Type Weighted Fractional Operators and Solutions to Cauchy Problems

In this paper,we establish the new forms of Riemann-type fractional integral and derivative operators.The novel fractional integral operator is proved to be bounded in Lebesgue space and some classical fractional integral and differential operators are obtained as special cases.The properties of new operators like semi-group,inverse and certain others are discussed and its weighted Laplace transform is evaluated.Fractional integro-differential freeelectron laser(FEL)and kinetic equations are established.The solutions to these new equations are obtained by using the modified weighted Laplace transform.The Cauchy problem and a growth model are designed as applications along with graphical representation.Finally,the conclusion section indicates future directions to the readers.

含自频移啁啾超短脉冲间相互作用的数值研究

采用拟解法给出了Ginzberg—Landau方程类孤波解的参数表达式 .通过数值模拟对啁啾超短脉冲间的相互作用进行了研究 .结果表明 ,随着相邻孤子间距离的减小 ,它们之间的相互作用变得越来越严重 .传统的不等振幅法在一定程度上可以抑制孤子间的相互作用 ,通过选取合适的振幅比 ,找到了相邻孤子间相互作用平衡的最小距离 ,这对提高光纤传输的比特率具有十分重要的意义 .讨论了多孤子间的相互作用 。

激光打靶实验数据采集与处理系统

本文简要叙述了国外激光打靶联网状况、网络技术发展趋势。提出了激光打靶实验数据在线采集和处理系统结构图，介绍了“神光”激光打靶实验微机网络系统，并对实验结果进行了讨论。

自由电子激光与混沌

对自由电子激光的混沌问題作了评述,讨论了自由电子激光中电子与光场的不稳定性、电子轨道混沌与光场混沌之间的相互影响与关联。指出用混沌理论研究手段对探索自由电子激光的重要意义和途径。