An excimer source of visible light

A gas-discharge excimer radiation source in the visible spectral region has been developed on the basis of a mixture of cadmium diiodide vapors and helium excited by a repetitively pulsed barrier discharge. The source radiation spectrum consists mainly of superimposed spectral bands of emission of cadmium iodide in the range 470–700 nm. The mean radiation power from the source surface (114.5 cm²) is 55 W, the pulse power is 105 kW, and the efficiency is ～10%. Approximately 90% of the radiation power is concentrated in the red region, which is much higher than in high-pressure sodium lamps at comparable energies deposited into the working mixtures. Such sources can be used to efficiently control photosynthesis and the growth and development of plants and algae.     

Frequency-domain fluorescence microscopy with the LED as a light source

We describe a frequency-domain lifetime fluorometer based on a microscope and a modulated light-emitting diode (LED) excitation source (370/460 nm), which operates in the frequency range 120 Hz–250 MHz. We collected multifrequency phase and modulation fluorescence responses from cellular areas as small as 10–15 µm in diameter. We also collected fluorescence lifetime data from cells stained by a lipophilic coumarin sensitized europium fluorophore, Coum-Eu, with a millisecond lifetime, and Ru(bpy)₂phe-C₁₂, with microsecond lifetime. Nanosecond lifetimes from native nuclei stained with SYTO 14 and SYTO 16 probes were measured as well. We demonstrate that a simple LED excitation source can, for many applications, successfully replace complex and expensive laser systems, which have been used for cellular frequency-domain lifetime measurements. As the LEDs are very stable with low noise, it will be possible to image even smaller sample areas using brighter LEDs. With availability of modulated LEDs emitting at several wavelengths covering almost the entire visible spectrum it is easy to assemble a system for the fluorophore of choice. The ability to select an excitation source for a given fluorophore and low price make such an excitation source even more practical.     

Examining water trees in polythene using a flexible light source

A battery powered flexible surgical light can be used as an inexpensive light source for transmission microscopy through 2 mm thick walls of polythene cups, where it is not possible to use a conventional condenser. With ASA 400 film photographic exposure times are 5–10 s. The illuminator has been used to study water trees in polythene.     

A wide-aperture Cerenkov counter with a water radiator

The design of a Cerenkov counter with a water radiator (200×400 mm), containing a wavelength shifter, is described. The counter was used for π- andK-meson selection in a positive-particle beam with 250–1000-MeV/c momentum.     

LED的光谱分布可调光源的设计

介绍了一种光谱分布可调光源的设计,该光源由积分球和大量不同颜色的LED组成.在可见波段.这种光源能产生不同光谱曲线,可以模拟很多不同光源的光谱分布.该项设计通过仿真使光源的光谱分布模拟目标光源的光谱分布,并设计了电源控制箱精确地控制每个LED模块.光源的面非均匀性为0.53%,角度特性在±10°以内,最大偏差为0.77%.这种新型光源在光辐射测量中可以作为一种传递标准.     

Design and evaluation of an imaging spectrophotometer incorporating a uniform light source

Accounting for light that is diffusely scattered from a surface is one of the practical challenges in reflectance measurement. Integrating spheres are commonly used for this purpose in point measurements of reflectance and transmittance. This solution is not directly applicable to a spectral imaging application for which diffuse reflectance measurements are desired. In this paper, an imaging spectrophotometer design is presented that employs a uniform light source to provide diffuse illumination. This creates the inverse measurement geometry to the directional illumination/diffuse reflectance mode typically used for point measurements. The final system had a spectral range between 400 and 1000 nm with a 5.2 nm resolution, a field of view of approximately 0.5 m by 0.5 m, and millimeter spatial resolution. Testing results indicate illumination uniformity typically exceeding 95% and reflectance precision better than 1.7%.     

Point light source detection characteristics of a SEC vidicon digital TV camera

Optimization of the point source detection properties of a Secondary Electron Conduction (SEC) vidicon TV camera tube as a detector of point light sources such as star fields or certain optical spectra requires the accurate determination of peak height, half-peak width, background, and location of the point image. Two perpendicular Gaussian curves have been used to define a point image, allowing changes in the parameters of these Gaussian curves to be used in the study of SEC vidicon point source properties as a function of electrical and optical parameters. Peak height was shown to depend on priming time and a method was developed to reduce the priming time by almost an order of magnitude by momentarily raising the target voltage during priming. Power supply specifications needed for 0.1 pixel (picture element) addressing accuracy were found to be +/-0.03 V. Focus current was optimized to obtain the best sensitivity and resolution over the entire target. Peak height, background, and half-peak width were found to be strongly dependent on readout beam current. Target voltage, over the limited range examined, was found to affect only the gain without compromising other image parameters, so that any value could be used, consistent with gain and sensitivity required.     

Advanced light ion source extraction system for a new electron cyclotron resonance ion source geometry at Saclay

One of the main goal of intense light ion injector projects such as IPHI, IFMIF, or SPIRAL2, is to produce high current beams while keeping transverse emittance as low as possible. To prevent emittance growth induced in a dual solenoid low energy transfer line, its length has to be minimized. This can be performed with the advanced light ion source extraction system concept that we are developing: a new ECR 2.45 GHz type ion source based on the use of an additional low energy beam transport (LEBT) short length solenoid close to the extraction aperture to create the resonance in the plasma chamber. The geometry of the source has been considerably modified to allow easy maintenance of each component and to save space in front of the extraction. The source aims to be very flexible and to be able to extract high current ion beams at energy up to 100 kV. A specific experimental setup for this source is under installation on the BETSI test bench, to compare its performances with sources developed up to now in the laboratory, such as SILHI, IFMIF, or SPIRAL2 ECR sources. This original extraction source concept is presented, as well as electromagnetic simulations with OPERA-2D code. Ion beam extraction in space charge compensation regime with AXCEL, and beam dynamics simulation with SOLMAXP codes show the beam quality improvement at the end of the LEBT.     

星上LED定标光源的可行性研究

对发光二极管作星上定标光源的可行性进行了分析研究.测量了LED的工作稳定性,对LED做了开合试验,讨论了它的电流特性.在真空环境下,分析了LED的冷热特性和抗辐射性能.结果表明,LED持续点燃1 200 h的衰减量＜1.2X;其开合重复性很好,但存在10～15 min的不稳定性;改变电流会引起LED发光强度和波长不同程度的变化;温度的变化也同样会影响LED的发光强度、正向偏压以及峰值波长.真空状态下,由于传输介质不同,LED的发光强度会有所增加,但其封装材料真空挥发产生的影响不大;在抗辐射外壳的保护下,空间辐射对LED发光强度的影响不超过0.5%/a.经过分析讨论,证明将LED应用于星上定标是可行的.     

An Aerogel Threshold Cerenkov Counter

The results of a study of the properties of aerogel manufactured at the Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, are presented. The technology of the production of aerogel samples and the optical characteristics of these samples are briefly described. A formula relating the refractive index of the aerogel to its density with regard to the dispersion of light is analyzed. The results of testing of an aerogel threshold Cerenkov counter are presented. Testing was performed using a beam of charged particles with momenta p ranging from p = 0.4–2.5 GeV/. The efficiency of pion detection with p 1 GeV/ was 97%; the efficiency of proton detection with p 2.5 GeV/c, 4%.     

A nanosecond light source for scintillation-and Cerenkov-detector calibration

A nanosecond blue-light source with increased brightness is described. A light-emitting diode by NICHIA is used. The pulse shaper triggering the light-emitting diode is based on avalanche transistors. The number of photons per pulse is ∼10⁹ at a light-pulse duration of ∼2 ns.     

Angle-resolved photoemission spectroscopy with a femtosecond high harmonic light source using a two-dimensional imaging electron analyzer

An experimental setup for time- and angle-resolved photoemission spectroscopy using a femtosecond 1 kHz high harmonic light source and a two-dimensional electron analyzer for parallel energy and momentum detection is presented. A selection of the 27th harmonic (41.85 eV) from the harmonic spectrum of the light source is achieved with a multilayer MoSi double mirror monochromator. The extinction efficiency of the monochromator in selecting this harmonic is shown to be better than 7:1, while the transmitted bandwidth of the selected harmonic is capable of supporting temporal pulse widths as short as 3 fs. The recorded E(k) photoelectron spectrum from a Cu(111) surface demonstrates an angular resolution of better than 0.6 degrees (=0.03 A(-1) at E(kin,e)=36 eV). Used in a pump-probe configuration, the described experimental setup represents a powerful experimental tool for studying the femtosecond dynamics of ultrafast surface processes in real time.     

Design of a compact electron cyclotron resonance ion source for medium charge state light ions

At the Australian Nuclear Science and Technology Organization we are developing a new isotope ratio mass spectrometer based on the measurement of multiple charge state ions. We have carried out a review of our existing ECR ion source and identified a number of design flaws. For the new instrument, we are producing a new ECR source and have refined the design, in particular by using 3D simulations to improve the magnetic confinement field and by a combination of simulations and experiments to improve the design of the microwave coupling.     

Construction of a new unclipped digital correlator for quasielastic light scattering

An unclipped digital correlator that we have built has been described. Our digital correlator can be easily incorporated (with only a moderate cost) in an established light scattering laboratory equipped with a computer.     

A simple method for making composite anaglyph transparencies for viewing from a single light source

This paper presents an easy technique that enables one to make composite anaglyph transparencies in any size up to 11 × 14 inches from SEM or TEM negatives. For viewing with an overhead projector, right and left images are printed on separate, fine-grain positive films, usually 5 × 7 to 8 × 10 inches in size. Standard black and white printing techniques are used throughout. The red and green stereo code is added to the two photographic emulsions with chemical toners. The transparencies are then superimposed, aligned, and presented using an overhead projector. As with other anaglyph processes, red and green spectacles are used for viewing.     

Time-resolved momentum imaging system for molecular dynamics studies using a tabletop ultrafast extreme-ultraviolet light source

We describe a momentum imaging setup for direct time-resolved studies of ionization-induced molecular dynamics. This system uses a tabletop ultrafast extreme-ultraviolet (EUV) light source based on high harmonic upconversion of a femtosecond laser. The high photon energy (around 42 eV) allows access to inner-valence states of a variety of small molecules via single photon excitation, while the sub--10-fs pulse duration makes it possible to follow the resulting dynamics in real time. To obtain a complete picture of molecular dynamics following EUV induced photofragmentation, we apply the versatile cold target recoil ion momentum spectroscopy reaction microscope technique, which makes use of coincident three-dimensional momentum imaging of fragments resulting from photoexcitation. This system is capable of pump-probe spectroscopy by using a combination of EUV and IR laser pulses with either beam as a pump or probe pulse. We report several experiments performed using this system.     

Diamond colour centres as a nanoscopic light source for scanning near‐field optical microscopy

Recently it was shown that a single molecule at cryogenic temperatures could be used as a local light source for illumination of a sample in the near field. Conventional light-emitting systems such as dye molecules and semiconductor quantum dots could also be used for this purpose, but they suffer from lack of photostability. However, colour centres in diamond have been found to be remarkably stable against bleaching and blinking effects. Here we present the first SNOM images taken with nanoscopic diamond crystals as a light source.     

Phase measurement using an interferometer having a filamentary spatial filter and an extended source of polychromatic light

The theory of phase measurement by means of the interferometer using a filamentary spatial filter (IFSF) is extended to the case in which the source has finite width. Experimental results satisfactorily coincide with theoretically obtained characteristics. The examination of accuracy suggests that the error in phi/2pi can be easily restricted to within 0.01. It is hoped that the IFSF will improve efficiencies in the measurement of dispersive power of a fluid and the method of coincidence being used in the measurement of a distance between reflecting surfaces, because it can simultaneously measure phases in various wavelengths if a polychrometer is set in the rear of the image plane.     

被动型CPT原子钟光源系统的设计与实现

简要介绍了相干布局数囚禁(CPT)原子钟的机理,分析了典型的CPT原子钟的系统构成.在此基础上,针对CPT原子钟的特点,以Rb原子钟为设计对象,设计并制作了一种可出射稳定激光频率并能与其他CPT原子钟相兼容的光源系统.该光源系统采用热电致冷器(TEC)对激光器进行温度控制,利用直接数字频率合成(DDS)技术和锁定放大(LIA)技术实现激光器光频稳定.测试结果表明,光源系统温度对波长的控制精度为0.001 2 nm,在此条件下,系统可以很好地完成激光光频的锁定.