Helium detection

Reinhardt M, Quiring G, Ramirez Wong RM, Wehrs H, Muller J (2010) Helium detection using a planar integrated micro-mass spectrometer. International Journal of Mass Spectrometry 295 145-148... 

Fig. 8.9 Hydrogen flux data from a 100 xm thick unalloyed ptdladium foiL Sieverts Law is followed very well, and the square root dependence implies that hydrogen is transported through the membrane in a dissociated form. The membrane, sealed by copper gaskets, was essentially 100% selective towards hydrogen with no leak to helium detected. Permeability at 440°C was 1.9 x 10 mol m- s-> Pa- -5...

This took place between 27 August 1987 and 9 September 1987 and enabled the leak to be located (infrared thermograph, xenon and helium detection in the mter-vessel space)... 

Riley DJ, Mann M, MacLaren DA, Dastoor PC, Allison W, Teo KBK, Amaratunga GAJ, MUne W (2003) Helium detection via field ionization from carbon nanotubes. Nano Lett 3 1455-1458... 

The detection opportunities for leaks using a leak detector, which works with a mass spectrometer for the helium detection, are unmatched. However, there are also known disadvantages of this method. 

The helium detection without using expensive high vacuum and without critical components is desirable for leak testing of industrial plants. In recent years a new type of helium sensor was therefore developed, which can detect helium selective and sensitive, without requiring high vacuum conditions and without the need of hot cathode filaments. It is reahsed a simple and rehable hehum detector with this so-called Wise Technology sensor, which is particularly suitable for industrial plants. 

The idea of the novel helium detection is a helium partial pressure sensor based on the known method of separating gases by a semipermeable membrane with gas-specific permeation. The component of the gas which is to be detected, in this case helium, is separated in the non-ionised state using the membrane. The amount of the separated helium is measured behind the membrane in a hermetically sealed volume, using a total pressure measurement in the evacuated volume. The change of total pressure in the enclosed volume corresponds to the helium partial pressure in front of the sensor membrane with a high selectivity for helium. 

Gr. helios, the sun). Janssen obtained the first evidence of helium during the solar eclipse of 1868 when he detected a new line in the solar spectrum. Lockyer and Frankland suggested the name helium for the new element. In 1895 Ramsay discovered helium in the uranium mineral clevite while it was independently discovered in cleveite by the Swedish chemists Cleve and Langlet at about the same time. Rutherford and Royds in 1907 demonstrated that alpha particles are helium nuclei. 

Alternatively, ions of any one selected m/z value can be chosen by holding the magnetic field steady at the correct strength required to pass only the desired ions any other ions are lost to the walls of the instrument. The selected ions pass through the gas cell and are detected in the singlepoint ion collector. If there is a pressure of a neutral gas such as argon or helium in the gas cell, then ion-molecule collisions occur, with decomposition of some of the selected incident ions. This is the MS/MS mode. However, without the orthogonal TOF section, since there is no further separation by m/z value, the new ions produced in the gas cell would not be separated into individual m/z values before they reached the detector. Before the MS/MS mode can be used, the instrument must be operated in its hybrid state, as discussed below. 

Precursor ions are selected by Ql and passed into the collision cell (Q2 orq2 of Figure 33.5). Here, collision with an inert gas (argon or helium) causes dissociation to occur, and the resulting fragment (product) ions are detected by scanning Q3 (Figure 33.6). 

Extraterrestrial dust particles can be proven to be nonterrestrial by a variety of methods, depending on the particle si2e. Unmelted particles have high helium. He, contents resulting from solar wind implantation. In 10-)J.m particles the concentration approaches l/(cm g) at STP and the He He ratio is close to the solar value. Unmelted particles also often contain preserved tracks of solar cosmic rays that are seen in the electron microscope as randomly oriented linear dislocations in crystals. Eor larger particles other cosmic ray irradiation products such as Mn, Al, and Be can be detected. Most IDPs can be confidently distinguished from terrestrial materials by composition. Typical particles have elemental compositions that match solar abundances for most elements. TypicaUy these have chondritic compositions, and in descending order of abundance are composed of O, Mg, Si, Ee, C, S, Al, Ca, Ni, Na, Cr, Mn, and Ti. 

Superfluid helium can pass easily through openings so small that they caimot be detected by conventional leak detection methods. Such leaks, permeable only to helium II, are called supedeaks. They can be a source of fmstrating difficulties in the constmction of apparatus for use with helium II. 

Different combinations of stable xenon isotopes have been sealed into each of the fuel elements in fission reactors as tags so that should one of the elements later develop a leak, it could be identified by analyzing the xenon isotope pattern in the reactor s cover gas (4). Historically, the sensitive helium mass spectrometer devices for leak detection were developed as a cmcial part of building the gas-diffusion plant for uranium isotope separation at Oak Ridge, Tennessee (129), and heHum leak detection equipment is stiU an essential tool ia auclear technology (see Diffusion separation methods). 

Consumer Products. Laser-based products have emerged from the laboratories and become familiar products used by many millions of people in everyday circumstances. Examples include the supermarket scaimer, the laser printer, and the compact disk. The supermarket scanner has become a familiar fixture at the point of sale in stores. The beam from a laser is scaimed across the bar-code marking that identifies a product, and the pattern of varying reflected light intensity is detected and interpreted by a computer to identify the product. Then the information is printed on the sales sHp. The use of the scanner can speed checkout from places like supermarkets. The scanners have usually been helium—neon lasers, but visible semiconductor lasers may take an impact in this appHcation. 

Mass Spectrometer. The mass spectrometer is the principal analytical tool of direct process control for the estimation of tritium. Gas samples are taken from several process points and analy2ed rapidly and continually to ensure proper operation of the system. Mass spectrometry is particularly useful in the detection of diatomic hydrogen species such as HD, HT, and DT. Mass spectrometric detection of helium-3 formed by radioactive decay of tritium is still another way to detect low levels of tritium (65). Accelerator mass spectroscopy (ams) has also been used for the detection of tritium and carbon-14 at extremely low levels. The principal appHcation of ams as of this writing has been in archeology and the geosciences, but this technique is expected to faciUtate the use of tritium in biomedical research, various clinical appHcations, and in environmental investigations (66). 

Elastic recoil spectrometry (ERS) is used for the specific detection of hydrogen ( H, H) in surface layers of thickness up to approximately 1 pm, and the determination of the concentration profile for each species as a function of depth below the sample s surfece. When carefully used, the technique is nondestructive, absolute, fast, and independent of the host matrix and its chemical bonding structure. Although it requires an accelerator source of MeV helium ions, the instrumentation is simple and the data interpretation is straightforward. 

S2-4 Helium burning as additional process for nucleogenesis 19S4 Slow neutron absorption added to stellar reactions 195S-7 Comprehensive theory of stellar synthesis of all elements in observed cosmic abundances 196S 2.7 K radiation detected... 

Optical detection of magnetic resonance (ODMR) was attempted for measurements of the pH effects on the triplet state of purine to investigate the protonation site of purine at low temperatures (78JA7131). The ODMR spectrum did not show the presence of more than one triplet state at liquid helium temperatures. Since the protonated tautomers 1H,9H (3a) and H,1H (3b) have similar bond structures, their triplets should have similar zero-field parameters and are thus not easy to distinguish by ODMR. 

Figure 12.9 Typical pyrolysis chromatogram of fraction from a styrene-acTylonitiile copolymer sample obtained from a miciocolumn SEC system 1, acrylonitrile 2, styrene. Conditions 5 % Phenylmetliylsilicone (0.33 p.m df) column (50 m X 0.2 mm i.d.) oven temperature, 50 to 240 °C at 10 °C/min carrier, gas, helium at 60 cm/s flame-ionization detection at 320 °C make-up gas, nitrogen at a rate of 20 mL/min. P indicates tlie point at which pyrolysis was made. Reprinted from Analytical Chemistry, 61, H. J. Cortes et ai, Multidimensional cliromatography using on-line microcolumn liquid cliromatography and pyrolysis gas cliromatography for polymer characterization , pp. 961-965, copyright 1989, with permission from tlie American Chemical Society.

Figure 12.22 SFC-GC analysis of aromatic fraction of a gasoline fuel, (a) SFC trace (b) GC ttace of the aromatic cut. SFC conditions four columns (4.6 mm i.d.) in series (silica, silver-loaded silica, cation-exchange silica, amino-silica) 50 °C 2850 psi CO2 mobile phase at 2.5 niL/min FID detection. GC conditions methyl silicone column (50 m X 0.2 mm i.d.) injector split ratio, 80 1 injector temperature, 250 °C earner gas helium temperature programmed, — 50 °C (8 min) to 320 °C at a rate of 5 °C/min FID detection. Reprinted from Journal of Liquid Chromatography, 5, P. A. Peaden and M. L. Lee, Supercritical fluid chromatography methods and principles , pp. 179-221, 1987, by courtesy of Marcel Dekker Inc.

The purity of the product was checked by vapor phase chromatography on a polyethylene glycol on Teflon column at 72°, 15 p.s.i., and a flow rate of 102 ml. of helium per minute. The sample appeared to be homogeneous, but, since the amine tails badly on the column, it is not possible to detect the presence of a small amount of water (less than 3%). 

Helium, the first member of the group, was detected in the spectrum of the Sun in 1868. Because of its low density (7 that of air), helium is used in all kinds of balloons and in synthetic atmospheres to make breathing easier for people suffering from emphysema. 

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