腔靶内爆区超热电子实验研究

利用１０道滤波荧光谱仪（ＦＦＳ）研究了强激光和薄壁腔靶相互作用时超热电子产生的特征，结合ＧａＡｓ硬Ｘ射线角分布探头，受激喇曼莠射光探头，针孔相机的测量结果，分析得出：在内爆腔靶中，超热电子产生的源区，大部分超热电子静电场和转换体约束在源区，只有小部分能量较高的超热电子进入到内爆区，内爆靶区超热电子总能量占超热电子总能量的约２０％，占入射激光能量的１％－３％。     

0．53μm激光产生的超热电子的实验观测

介绍了在“神光”Ｉ号装置上利用波长０．５３ｐμｍ、脉宽τ约７５０ｐｓ、能量６０～２３０Ｊ激光（靶面激光强度１×１０￣（１３）～５×１０￣（１５）Ｗ／ｃｍ￣２）照射Ａｕ盘靶和Ａｕ拄黑腔靶产生超热电子的实验观测结果与分析。实验测量１０ｋｅＶ以上硬Ｘ光谱和通量表明：采用倍频激光可以使超热电子能量明显比基频光小一个量级左右，超热电子温度Ｔ＿ｈ、热电子温度Ｔ＿ｅ均降低一半左右，受激Ｒａｍａｎ散射光能量Ｅ＿（ＳＲＳ）减少二个多量级。在我们的实验条件下，Ａｕ盘靶（等离子体定标尺度Ｌ≤１００μｍ）产生超热电子的主要机制可能是双等离子体衰变和共振吸收，此外还有受激Ｒａｍａｎ散射（ｎ≈ｎ＿ｃ／４），１００μｍ＜Ｌ≤２４０μｍ超热电子产生的主要机制是ＴＰＤ，此外还有ＳＲＳ（ｎ≈ｎ＿ｃ／４）；黑腔靶（Ｌ≥３００μｍ）超热电子产生的主要机制是ＳＲＳ（ｎ＜ｎ＿ｃ／４）。     

1．053μm激光在腔靶中反常吸收和超热电子的研究

从１９９０年到１９９３年，在神光Ⅰ上我们利用多种能量卡计和谱仪，全面系统地研究了基频光在腔靶中产生的反常吸收和超热电子。实验获得了腔靶反常吸收光谱、能量和硬Ｘ光谱，给出了ＳＲＳ能谱和能量、超热电子能量和温度与激光参数和靶型的关系，证明了采用短波长激光。     

腔靶超热电子产生硬X射线的理论模拟

利用计算得到的原子数据参数，定量地计算了强激光与金腔靶相互作用时，其超热电子产生的硬Ｘ射线的角分布、空间分布、硬Ｘ射线转换效率等参量．为进一步诊断腔靶内超热电子的状况提供了必要的理论依据．     

激光聚变实验测量和诊断技术的新进展──激光间接驱动干净辐射场的建立和诊断

介绍了我们在激光惯性约束聚变（ＩＣＰ）实验测量和诊断技术方面取得的新进展。着重介绍了激光聚变黑洞靶辐射场干净性的实验测量及其诊断技术。采用改进后的带视场限制系统的散射光探测器和改进型法拉第杯分别测量了内爆区散射激光和快离子特性。巧妙设计腔靶结构，利用高能针孔相机和ＦＦ谱仪测量硬ｘ射线空间分布及能量变化，定出了进入内爆区中的超热电子量。     

黑洞靶X光产生机制实验研究

本文报导了黑洞靶Ｘ光产生机制实验研究。实验采用波长为１．０５３μｍ，能量为３００－７００Ｊ／束，脉宽为６００－１０００ｐｓ的高斯型激光脉冲。利用三台亚千Ｘ光能谱仪，三台软Ｘ光针孔相机、一台软Ｘ光透射光栅谱仪和十个平响应亚千Ｘ射线二极管对十余种结构、尺寸腔靶实验进行测量。实验给出了腔靶发射Ｘ光的空间分辨像、时间过程、光谱结构及空间角分布测量结果。通过分析，基本弄清了黑洞靶Ｘ光产生机制。     

1MeVSi~＋衬底加温注入Al＿（0．3）Ga＿（0．7）As／GaAs超晶格和GaAs的晶格损伤研究

用卢瑟福背散射／沟道技术研究了１ＭｅＶＳｉ￣＋在衬底加温和室温下以不同剂量注入Ａｌ＿（０．３）Ｇ＿（０．７）Ａｓ／ＧａＡｓ超晶格和ＧａＡｓ后的晶格损伤。在衬底加温下，观察到Ａｌ＿（０．３）Ｇａ＿（０．７）Ａｓ／ＧａＡｓ超晶格和ＧａＡｓ都存在一个动态退火速率与缺陷产生速率相平衡的剂量范围，以及两种速率失去平衡的临界剂量。超晶格比ＧａＡｓ更难以损伤，并且它的两种速率失去平衡的临界剂量也大于ＧａＡｓ中的相应临界剂量，用热尖峰与碰撞模型解释了晶格损伤积累与注入剂量和衬底温度的关系。用ＣＮＤＯ／２量子化学方法计算了ＧａＡｓ和Ａｌ＿ｘＧａ＿（１－ｘ）Ａｓ中化学键的相对强度，并根据计算结果解释了注入过程中Ａｌ＿（０．３）Ｇａ＿（０．７）Ａｓ／ＧａＡｓ超晶格和ＧａＡｓ中晶格损伤程度的差别。     

利用金刚石探测器测量软X光辐射功率

使用天然Ⅱａ型金刚石光电导探测器（ＰＣＤ），测量激光等离子体发射的软Ｘ光辐射。由于探测器在２００ｅＶ～２２００ｅＶ之间具有平响应特性，可以不加滤片直接测量Ｘ光功率和能量。金刚石ＰＣＤ与软Ｘ光能谱仪和平响应Ｘ光二级管的测量结果基本一致。     

系列柱形薄壁腔靶制备工艺研究

为了从实验上深入研究超热电子产生规律，从而减少或抑制超热电子对惯性约束聚变（ＩＣＦ）的危害，我们制备了一系列薄壁腔靶，以供实验研究。本文详细地描述了柱形薄壁腔靶的制备工艺。利用ＮＧ－１０４型精密单向纵切车床，采用金刚石刀具车削，提高心轴质量，表表粗糙度可达０．１μｍ。采用电镀和磁控溅射二种方法镀膜，为了使腔靶壁厚均匀，在镀膜时，必须使心轴匀速旋转。利用磁控溅射在腔靶外表面再涂上１μｍ左右厚的二氧化硅，以提高超薄壁腔靶的强度和自立能力。在腐蚀心轴时，必须仔细控制酸的浓度，防止在腐蚀时因产生气泡太多，太快而使腔靶破裂。用Ｘ射线照相法和扫描电子显微镜测量腔靶的几何参数。制备系列柱形薄壁腔靶达到指标为：壁厚范围２～３０μｍ，壁厚均匀性小于１０％，表面粗糙度０．２～０．３μｍ。最后介绍了在“神光Ⅰ”上打靶结果。结果表明，实验值与理论值符合较好。     

“神光Ⅱ”基频光黑腔靶实验超热电子诊断

介绍“神光Ⅱ”首次进行大能量基频光黑腔靶实验超热电子实验观测,采用十道滤波荧光谱仪(FFS)测量腔靶发射15—250keV硬x射线谱,由高能x射线谱通量推断超热电子占入射激光能量份额ηhe为13%—16%,由谱的斜率推断超热电子温度Th为35—45keV,由超热电子能量和受激拉曼散射光(SRS)能量的关联,推断超热电子产生的机理,并给出了不同腔靶在不同激光能量EL下超热电子产生的特征 关键词： 1.053μm激光 超热电子 黑腔靶 大能量激光     

MECHANISM OF HOT ELECTRON GENERATION AND STIMULATED RAMAN SCATTERING IN LASER CAVITY TARGET PLASMA

Stimulated Raman Scattering (SRS) and X-ray spectrum emitted from many kinds of targets were experimentally investigated on the Nd:glass laser facility Shenguang-I in Shanghai, China. By theoretical analysis and computer simulation for these experiments, the result showed that the mechanism of hot electron generation in laser cavity target was mainly SRS, according to detailed comparison between the cavity target and the plane target. Other results, such as the energy fraction and temperatures of hot electron, energy and angular distribution and wave spectrum in SRS, were also presented in detail.     

A hot cavity laser ion source at IGISOL

A development program is underway at the IGISOL (Ion Guide Isotope Separator On-Line) facility, University of Jyväskylä, to efficiently and selectively produce low-energy radioactive ion beams of silver isotopes and isomers, with a particular interest in N = Z ⁹⁴Ag . A hot cavity ion source has been installed, based on the FEBIAD (Forced Electron Beam Induced Arc Discharge) technique, combined with a titanium:sapphire laser system for selective laser ionization. The silver recoils produced via the heavy-ion fusion-evaporation reaction, ⁴⁰Ca(⁵⁸Ni, p3n)⁹⁴Ag , are stopped in a graphite catcher, diffused, extracted and subsequently ionized using a three-step laser ionization scheme. The performance of the different components of the hot cavity laser ion source is discussed and initial results using stable ^{107, 109}Ag are presented.     

Kinetics analysis of chemiluminescence in discharge-driven HF chemical lasers

The chemiluminescence spectrum in the optical cavity of discharge-driven hydrogen ?uoride(HF) chemical laser is measured.The result reveals that the spectra of the helium and fluorine(F) atoms are the major components.Moreover,the green chemiluminescence in the downstream of the optical axis is mostly composed of the 60P20 spectral line of the HF molecule.The analysis shows that,except for the cold pumping reaction,the recombination of the F atoms and the hot pumping reaction also occur in the optical cavity.Due to the hot pumping reaction and the optical cavity temperature in a specific range,the 60P20 line becomes the strongest HF molecule in the downstream region of the optical axis.After the hot pumping reaction,the green chemiluminescence always appears in the downstream region of the optical axis when the optical cavity temperature varies in a greater range.     

Molecular dynamics study of the stability of a carbon nanotube atop a catalytic nanoparticle

The effect of spontaneously generated coherence (SGC) on the quantum heat engine (QHE) consisting of a laser system is studied in terms of its dynamical evolution and the generation of coherences. The QHE is coupled to the two thermal photon reservoirs, a squeezed thermal bath as well as to a cavity mode. The coherence associated with the transition interacting with squeezed reservoir and the average thermal photon number of the hot (as well as cold) reservoir shows a non monotonous behavior between them. The dynamics along with generated coherences of the system and the laser power emitted depend sensitively on the hot, cold and squeezed reservoir parameters.     

New N2O laser band in the 10 μm wavelength region

Fifty new laser lines have been observed in continuous emission from an N₂O laser by placing a hot N₂O absorber cell inside the laser cavity to suppress the regular laser lines. The new lines are identified as rotation-vibration transitions of the (00⁰2–10⁰1) band of N₂O.     

Preparation of the four-qubit cluster states in cavity QED and the trapped-ion system

This paper proposes a simple scheme to generate a four-atom entangled cluster state in cavity quantum electrodynamics. With the assistantce of a strong classical field the cavity is only virtually excited and no quantum information will be transferred from the atoms to the cavity during the preparation for a four-atom entangled cluster state, and thus the scheme is insensitive to the cavity field states and cavity decay. Assuming that deviation of laser intensity is 0.01 and that of simultaneity for the interaction is 0.01, it shows that the fidelity of the resulting four-atom entangled cluster state is about 0.9886. The scheme can also be used to generate a four-ion entangled cluster state in a hot trapped-ion system. Assuming that deviation of laser intensity is 0.01, it shows that the fidelity of the resulting four-ion entangled cluster state is about 0.9990. Experimental feasibility for achieving this scheme is also discussed.     

Near-infrared cavity enhanced absorption spectroscopy of hot water and OH in an oven and in flames

A compact diode laser operating around 1.5 μm was used to measure cavity enhanced absorption spectra of hot water molecules and OH radicals in radiative environments under atmospheric conditions. Spectra of air were measured in an oven at temperatures ranging from 300 K to 1500 K. These spectra contained rovibrational lines from water and OH. The water spectra were compared to simulations from the HITRAN and HITEMP databases. Furthermore, spectra were recorded in the flame of a flat methane/air burner and in an oxyacetylene flame produced by a welding torch. The results show that cavity enhanced absorption spectroscopy provides a sensitive method for rapid monitoring of species in radiative environments. Received: 22 February 2001 / Revised version: 23 April 2001 / Published online: 7 June 2001     

Optically-Pumped Far-Infrared Laser Lines in Hydrazine, Methanol, Heavy Water, and Ammonia: New Laser Lines and Frequency Measurements

A far-infrared laser cavity designed to favor short-wavelength laser lines was used to generate optically-pumped far-infrared laser radiation. New far-infrared laser lines were discovered in hydrazine, heavy water, ammonia, and several short-wavelength lines previously discovered in methanol were observed. Wavelength, frequency, and relative intensity measurements were performed on laser lines in the wavelength range 42.4 to 253.7 m. Each far-infrared frequency measurement was obtained by mixing the far-infrared radiation with radiation from two reference CO₂ lasers and from a microwave synthesizer in a metal-insulator-metal diode. The pump laser was a high-Q Fabry Perot resonator oscillating on 275 grating-selected laser lines including regular, sequence, and hot band lines.     

Temporal dynamics of high repetition rate pulsed single longitudinal mode dye laser

Theoretical and experimental studies of temporal dynamics of grazing incidence grating (GIG) cavity, single-mode dye laser pumped by high repetition rate copper vapour laser (CVL) are presented. Spectral chirp of the dye laser as they evolve in the cavity due to transient phase dynamics of the amplifier gain medium is studied. Effect of grating efficiency, focal spot size, pump power and other cavity parameters on the temporal behaviour of narrow band dye laser such as build-up time, pulse shape and pulse width is studied using the four level dye laser rate equation and photon evolution equation. These results are compared with experimental observations of GIG single-mode dye laser cavity. The effect of pulse stretching of CVL pump pulse on the temporal dynamics of the dye laser is studied.     

Residual pump light as a probe of self-pulsing instability in an ytterbium-doped fiber laser

Self-pulsing instability in the ytterbium-doped fiber (YDF) laser is investigated with the pump-bypassed cavity configuration. The residual pump light acts as a probe of the intracavity dynamics, and the temporal behavior of the light shows correlations with the self-mode locking instability in the original cavity and the sustained self-pulsing instability in the modified cavity of the YDF laser. The results suggest that the interactions among stimulated emission, pump absorption and/or reabsorption could account for self-pulsing instability in the YDF laser. The pump-bypassed laser cavity configuration can be used to investigate the instabilities of various kinds of fiber lasers.