Design and implementation of a compact high-throughput echelle spectrometer using off-the-shelf off-axis parabolic mirrors for analysis of biological samples by LIBS (Conference Presentation)

This work presents the development of an Echelle spectrometer that is optimized for the characterization of laser-driven plasma emission of biological samples for application in smart laser surgery systems. Despite the compact (portable) and cost-efficient design of the developed spectrometer, it allows analyzing the spectrum of a plasma emitted from bone, and its surrounding soft tissues (bone marrow, muscle, and fat) in nearly the same way as a full-sized Echelle spectrometer as used in commercial laser-induced breakdown spectroscopy (LIBS) systems. Most of the commercially available Echelle spectrometers on the market use a long focal length on-axis mirror to have a reasonable F number (which defines the optical throughput of the system) and low aberration. While a long focal length requires less tilting of the mirror than a shorter focal length (the higher the tilt angle, the higher the aberration), a long focal length increases the system size and decreases sensitivity (i.e., less optical throughput). In this work, a parabolic 90o off-axis mirror with a focal length of 152.4 mm and a diameter of 50.8 mm, which leads to an F-number of 3, has been used. This low F-number provides a high optical throughput compared to other similar commercial Echelle spectrometers with F-numbers of 10 or more [1-5]. Since most of the important peaks in biological tissue are in the interval of 240 to 840 nm [6], the design was done by using off-the-shelf aluminum mirrors with a UV-enhanced coating for both collimating and focusing purposes to cover this range with sub-Angstrom resolution. Both collimating and focusing mirrors were chosen with the same radius of curvature and declination angle (opposite direction) to cancel the coma. In this antiparallel configuration, the second parabolic mirror largely eliminates the aberrations from the first one. Moreover, we positioned the Echelle grating under the condition of quasi-Littrow design to have high diffraction efficiency with an off-axis angle in the horizontal plane. A ruled reflection grating with dispersion perpendicular to that of the Echelle grating was utilized as a cross dispenser (order separator) after the Echelle grating to distinguish the overlapping diffraction harmonics. The spectrometer has been connected to a gated ICCD to measure time-resolved spectra. The developed spectrometer was installed on a 3-tier utility cart, the inducing laser (Q-switched Nd:YAG) for LIBS was placed on the middle tier, and the last tier was dedicated for calibration instruments (a NIST traceable balanced Deuterium-Halogen light source for intensity calibration, and some gas/vapor spectral lamps including Mercury-Argon, Argon, Neon, and Krypton for wavelength calibration). The portability feature of this LIBS setup provides a remarkable value for testing and characterizing different biological samples on-site. This is a great capability especially if the target sample has the potential of being contagious. This setup is meant to be used for so-called smart laser osteotomies, i.e., the osteotome will be able to identify the type of the tissue being cut through the feedback provided by LIBS [6-8]

Krzysztof Lipiński (1957-2013) – wrażliwy poeta i wnikliwy obserwator spraw ludzkich, mistrz słowa i przekładu

Artykuł stanowi krótkie przedstawienie sylwetki Krzysztofa Lipińskiego, wybitnego germanisty, literaturoznawcy, przekładoznawcy  i tłumacza z uwypukleniem subiektywnie wybranych obszarów, w któych zbiegały się zainteresowania przedstawionego mistrza i autorów artykułu.

High-resolution atomic absorption spectrometer for the simultaneous multielement analysis

The advantages of electrothermal atomic absorption analysis, such as high sensitivity, lower chemical and spectral influences, and lower consumption of samples and argon in comparison with the inductively coupled plasma atomic emission spectrometry have motivated the development of the equipment for the simultaneous atomic absorption determination of elements groups. The solution of this problem, and the achievement of detection limits close to those of atomic absorption analyzers with line-spectrum sources, require a high-speed system for recording the absorption of sample vapor in the wavelength range of 190-800 nm with high spectral resolution. This paper is devoted to the development of a “Grand-AAS” atomic absorption spectrometer based on a high-resolution “Grand-2” spectral instrument with MAES multichannel analyzer of emission spectra, XWS-65 plasma continuum source and electrothermal atomizer. In the constructed device, the information on the spectral composition of vapor during a 1-2 s pulse of electrothermal atomization of the sample is recorded using the two hybrid assemblies of photodetector linear arrays. Thus, about 60 thousand measuring channels of the MAES analyzer simultaneously record absorption spectra in the spectral regions of 190-350 and 350-780 nm with a resolution of 10 and 30 pm respectively, and with a speed of 500 spectra/s. This equipment allows one to simultaneously receive atomic absorption signals for all recorded analytical lines of the elements. Automatic signal processing, including nonatomic absorption correction and linearization of calibration curves, is performed using one of the modules of the “Atom” software. Experiments have shown that in the practical use of “Grand-AAS”, the range of direct determination of metals in multielement solutions was up to 4 orders of magnitude of the concentration with the detection limits of up to hundredths of µg/l. Due to the high brightness of the source and the luminosity of polychromators, the device is comparable in detection limits to the commercial continuum-source “ContrAA” spectrometer for the sequential determination of elements.Такие преимущества электротермического атомно-абсорбционного анализа, как высокая чувствительность определений, меньшие химические и спектральные помехи, малое потребление проб и аргона в сравнении с атомно-эмиссионной спектрометрией с индуктивно связанной плазмой, побуждают искать возможности создания аппаратуры для одновременного атомно-абсорбционного определения группы элементов. Для решения этой задачи и достижения пределов обнаружения, близких к показателям атомно-абсорбционных анализаторов с источниками линейчатого спектра, необходима быстродействующая система регистрации поглощения паров пробы в диапазоне длин волн 190-800 нм с высоким спектральным разрешением. Настоящая работа посвящена созданию атомно-абсорбционного спектрометра «Гранд-ААС», на базе спектрального прибора высокого разрешения «Гранд-2» с многоканальным анализатором эмиссионных спектров МАЭС, плазменного источника непрерывного спектра XWS-65 и электротермического атомизатора. В созданном приборе информацию о спектральном составе паров при 1-2 секундном импульсе электротермической атомизации пробы регистрируют с помощью двух гибридных сборок линеек фотодетекторов. Таким образом, около 60 тысяч измерительных каналов анализатора МАЭС одновременно регистрируют спектры поглощения в спектральных областях 190-350 и 350-780 нм с разрешением 10 и 30 пм, соответственно, и быстродействием 500 спектров/с. Такая техника позволяет одновременно получить сигналы атомного поглощения для всех регистрируемых аналитических линий элементов. Автоматическая обработка сигналов, включающая коррекцию неатомного поглощения и линеаризацию градуировочных графиков, осуществляется с помощью модуля программы «Атом». Эксперименты показали, что при практическом использовании «Гранд-АСС» диапазон прямого определения металлов в многоэлементных растворах составляет до 4 порядков концентраций при пределах обнаружения до сотых долей мкг/л. Благодаря высокой яркости источника и светосиле полихроматоров, прибор не уступает по пределам обнаружения коммерческому спектрометру ContrAA с источником непрерывного спектра, предназначенному для последовательного определения элементов