Modernization of the Element 2 mass spectrometer

To perform direct elemental analysis of solids, it is proposed to complement an Element 2 ICP mass spectrometer commercially produced by Thermo Electron Corp. with a glow-discharge ion source based on a hollow cathode. The analyzed sample, in the form of a rod 1.0–2.5 mm in diameter and 15–20 mm in length, is set along the axis of the cathode cavity with an inner diameter of 15–16 mm and a depth of 15 mm. The cathode is placed in a discharge chamber, which, using a viton seal, is substituted for the ICP-source sampler. The use of a plasma mirror and getter evacuation of the source chamber allows a decrease in the source’s hydrocarbon background by a factor of 10³–10⁴. The ion source is evacuated by a mechanical pump of the mass spectrometer and an additional turbomolecular pump. Ion sources in a mass spectrometer are replaced (a change from one analytical method to another) within 5 min. The ion current extracted from the IS allows analysis of conducting solids with a sensitivity at a level of several ppb (10⁻⁷%) at a resolution of the mass spectrometer of 4000. Combining two easily replaceable ICP and GD ion sources in a single high-resolution analyzer significantly extends the analytical capabilities of the Element 2 mass spectrometer. Original Russian Text ? G.G. Sikharulidze, 2009, published in Pribory i Tekhnika Eksperimenta, 2009, No. 2, pp. 98–100.     

Ion processes in a liquid-xenon ionization chamber under high-intensity pulsed irradiation

The current of positive ions in a liquid-xenon ionization chamber was studied under intense pulsed irradiation of the chamber with bremsstrahlung from a microtron. The dose absorbed in xenon during a radiation pulse was varied from 0.1 to 1.3 × 10⁴ μGy. It has been revealed that, in the dependence of the current on the irradiation dose, a deviation from a simple linear dependence is observed at a pulse dose of ∼4 μGy (∼0.2D _cr). Calculations show that recombination is the main cause of such deviation. A space charge appearing in the chamber under high irradiation intensities leads to a decrease in the electric field. The manifestation of the effects of a space charge becomes substantial when the field in a certain part of the chamber drops almost to zero. Under particular irradiation conditions, the space charge manifested itself in this study beginning with doses in a pulse of ∼50 μGy. The joint effect of the recombination and the space charge resulted in a dependence of the type of i ∼ D ^1/3. The influence of the ion current on the energy resolution of the ionization spectrometer is calculated for γ quanta detected during intervals between irradiation pulses. It is shown that a substantial impairment of the resolution begins at doses appreciably lower than the critical dose. The influence of the ion current becomes greater, as the dimensions of the chamber increase.     

A device for the preliminary separation of ions for mass spectrometry analysis

A device for the preliminary separation of ions based on an ion mobility increment spectrometer with cylindrical geometry of its electrodes is described. The device is operated in tandem with an atmospheric-pressure ionization mass spectrometer. The use of the spectrometer in the preliminary separation of ions of the target substance from ions of the chemical noise is illustrated by investigating the vapor above a water solution of acrylamide (CH₂=CH-CO-NH₂) with a concentration of 1.4 × 10⁻⁵ mol/L. The resolution of the device is rather low, R ∼ 10–20; nevertheless, thanks to its simplicity and availability, the device may find application to routine chemical analysis and in portable instruments.     

Ultimate characteristics of an X-ray prism spectrometer

X-ray prism spectrometry schemes for experimental investigations of fast processes are considered. Diamond and beryllium prism dispersion parameters and special features of transmission spectra for crystal prisms are analyzed. It is shown that relative energy resolution E/ΔE at photon energies E ∼ 10 keV may reach 10³–10⁴ and the total working spectral band is ∼100 keV. This opens unique possibilities for measuring fine structures of single-shot absorption spectra for quasi-parallel beams and continuous monitoring of the fundamental and high-frequency harmonics of an X-ray free electron laser. Original Russian Text ? A.G. Tur’yanskii, 2009, published in Pribory i Tekhnika Eksperimenta, 2009, No. 4, pp. 150–158.     

A hyperboloid mass spectrometer with a monopolar ion trap

A hyperboloid mass spectrometer with an analyzer utilizing a three-dimensional ion trap bounded by the planez=0 is described. Potential distribution in a monopolar trap is numerically simulated and the influence of distortion function ΔU(z, r) on the trajectories of charged particles is investigated. Mass peaks for various operating modes of the analyzer are calculated. An experimental mass spectrometer with a monopolar ion trap has been investigated. Spectra of the residual atmosphere and of that with tetrachloromethane CCI₄ puffed into the vacuum chamber have been measured. The resolution obtained isR _0.5=1.2×10³.     

Detection of neutrons and γ rays by a xenon pulsed ionization chamber

The applicability of a xenon γ-ray spectrometer based on a high-pressure (50 atm) xenon cylindrical ionization chamber to thermal neutron detection is discussed. The reaction of radiative capture of thermal neutron capture ¹³¹Xe(n, γ)¹³²Xe* followed by emission of 668-keV γ rays detectable by the spectrometer is used. The response of the xenon spectrometer with a sensitive volume of 0.2 L is analyzed. The measured thermal neutron detection efficiency is 0.08%. The advantage of the detector is its capability of simultaneously detecting both thermal neutrons and γ rays, which allows precise and high-efficiency identification of radioactive and fissile materials.     

An automatic system for controlling the UV-radiation dose

A photodetector based on an ⁺-GaAs/n-ClInPc heterojunction, photosensitive in the 200- to 1000-nm wavelength range, is described. The ClInPc absorbtance is high:K _λ=2×10⁷ m⁻¹ for λ=220 and 380 nm. The photosensitivity of the photodetector is 2250 V/W (S=1 cm²). An automatic system for controlling the UV-radiation dose was developed on the basis of this photoreceiver.     

CsI(Tl)-calorimeter calibration with positive-kaon decay products

The CsI(Tl) calorimeter was calibrated in the KEK-E246 experiment withK _μ2-andK _π2-positivekaon decays. The following calorimeter parameters were obtained: an energy resolution (σ) of 4.1% forE=242.5 MeV, a π⁰ invariant-mass resolution (σ) of 5.6%, and an angular resolution (σ) of 3.1^o.     

A Wideband spectrometer for NMR studies

The design of a wideband decimeter-wave (200–900 MHz) spectrometer with a magnetic induction of up to ∼10 T is described. This spectrometer is intended for studying electronic-nuclear oscillations in antiferromagnets at low temperatures (4.2−1.3 K). Critical field H _c = 2.5 ± 0.3 T of a reorientation transition in a noncollinear antiferromagnet Mn₃Al₂Ge₃O₁₂ at temperature T ≈ 1.3 K was determined from a ⁵⁵Mn²⁺ NMR spectrum.     

Compact mass spectrometer on permanent magnets

Preliminary results of development and testing of prototype compact mass spectrometer on permanent magnets are presented. The feature of the mass spectrometer is the ability to record mass spectra by mass scanning due to partial shunting of a magnetic flux in the gap of the mass analyzer. Ion-optical scheme of the mass analyzer has an ions deflection angle φ _m = 120° and the radius of the central trajectory r _m = 60 mm. The device can record mass range from 11 to 23 amu, with the accelerating voltage of 1 kV and the resolution of about 200. Inner volume of the mass analyzer chamber with the ion pump is about 500 cm³. Dimensions of the mass spectrometer together with electronic unit (height/length/width)—230 × 450 × 450 mm. The power consumption is not exceeding 60 W, in standby mode (the mode to maintain a high vacuum) is less than 10 W. The weight is 30 kg. The mass spectrometer is designed for educational purposes, however, it can be used as the basis to develop devices for isotopic analysis of the light chemical elements in medicine, geology, agricultural chemistry.     

Characteristics of the detecting equipment for the nanosecond tagged-neutron technology

Detecting equipment for the nanosecond tagged-neutron technology has been developed, and its characteristics have been studied. The principles of arrangement and operation of the readout electronics based on the selection of useful events according to specified criteria and data accumulation by a buffer-memory unit with subsequent transfer of data arrays to a remote computer for processing and visualization. The main selection criterion is the presence of signals from α- and γ detectors within the time gate and amplitude ranges in the absence of overlapped events. A prototype of a setup for testing the developed equipment was assembled and experimental studies of its characteristics were performed. The time resolution attained in the recording of α-γ coincidences is 1.0 ± 0.1 ns at an amplitude resolution of the γ detector of 3.6–3.8%. Original Russian Text ? K.A. Balygin, M.D. Karetnikov, A.I. Klimov, K.N. Kozlov, E.A. Meleshko, I.E. Ostashev, G.V. Yakovlev, 2009, published in Pribory i Tekhnika Eksperimenta, 2009, No. 2, pp. 122–132.     

A radiation foil bolometer for measuring the energy losses of fast Z-pinches

A radiation foil bolometer intended for measuring radiation-energy fluxes and plasma flows in high-power pulsed plasma X-ray sources is studied. In the bolometer, the radiation or ion-flow energy is absorbed by a 13-μm-thick niobium foil preliminarily heated to T ≈ 1900 K by a quasi-constant current lasting 2 s. Radiation from the foil was fed through an 8-m-long light guide to a semiconductor photodetector. The sensitivity of the instrument obtained from the results of calibrations is 0.56 J/V cm². The time resolution of this technique (∼2.5 μs) is determined by the foil heating time. In experiments with megaampere Z-pinches, the time resolution attained allows detection of the radiation energy independently of the energy of expanding plasma flows. In this case, the photoelectric effect from X-rays and the conductivity of expanding plasma do not affect the operation of the radiation bolometer. The working capacity of the bolometer was demonstrated at the Angara-5-1 facility in experiments with high-current Z-pinches with a radiation output energy of 50–100 kJ/pulse. The measurements performed have shown that the energy flux density of plasma expanding in the direction perpendicular to the pinch axis is at most 5% of the energy flux density of soft X-rays.     

Laser NIR lifetime spectrometer with nanosecond time resolution

A laser lifetime spectrometer (fluorometer) for recording the luminescence kinetics in the range 950–1400 nm with a time resolution of 1 ns is described. The performance capabilities of the facility are demonstrated by an example of studying the near-IR luminescence of molecular singlet oxygen ¹O₂. The fluorometer allows measurements of quenched luminescence of ¹O₂ with a quantum yield of up to 6 × 10⁻⁹.     

An adaptive γ-ray spectrometer with a high event processing rate

A fast γ-ray spectrometer adaptable to the scintillator type is described. This spectrometer is capable of processing a γ-ray energy spectrum (with a resolution of <4% in the energy range from 20 keV to 10 MeV) in a sequence of time intervals in the real-time mode at a counting rate of up to 10⁶ cps. Digitization of the detector signals by a 14-bit ADC with a sampling rate of 64 MHz and real-time data stream processing are used to separate overlapping events and correctly generate energy spectra.     

A time-of-flight measurement system for the HADES wide-aperture dielectron spectrometer

The HADES spectrometer and a time-of-flight detector based on long-sized (50–250 cm) scintillation counters are described. The detector is designed for identification of electrons, pions, and protons with momenta of 0.1–1.5 GeV/c at a flight distance of 220–250 cm. The operating conditions are analyzed, and the requirements to the detector and counter design are formulated. The design of the counters and their arrangement in the spectrometer are considered. The results of experimental studies of such characteristics of long counters as the light attenuation length in a scintillator and temporal and spatial resolutions, dependeing on the location of the point of the particle’s hit on the counter, are presented. Analysis of the data has shown that the main factor determining the spatial resolution of long counters is the quality of the polishing of the side faces of the scintillators, which determines the effective (averaged over the scintillator side surfaces) coefficient of total internal reflectionR. It is shown that, forR>-0.99, it is quite possible to achieve temporal and spatial resolutions of 100 ns and 2–3 cm, respectively, for scintillators with a length of up to 250 cm and a cross section of 1–20 cm². Foreign and Russian photomultipliers were used in the counters.     

The 5N neutral particle beamline of the U-70 accelerator (Institute for High Energy Physics)

The 5N neutral particle beamline at the U-70 accelerator (Institute for High Energy Physics), which has been designed to produce a high-intensity neutron beam with the highest possible energy, is described. The average neutron energy is ∼51 GeV, and the beam intensity is up to 10⁷ neutrons per spill. For several years, this beam has been used to investigate charmed particles and narrow baryon resonances in neutron-nucleus interactions and search for exotic multiquark states with the aid of the EXCHARM spectrometer. Original Russian Text A.N. Aleev, V.A. Arefiev, A.A. Aseev, Yu.G. Basha, V.P. Balandin, A.P. Bugorsky, T.S. Grigalashvili, B.N. Guskov, A.A. Zhuravlev, V.N. Zapolsky, A.I. Zinchenko, I.M. Ivanchenko, N.N. Karpenko, M.N. Kapishin, V.D. Kekelidze, D.A. Kirillov, I.G. Kosarev, N.A. Kuzmin, M.F. Likhachev, A.L. Ljubimov, D.T. Madigozhin, A.N. Maximov, N.A. Molokanova, A.N. Morozov, F.N. Novoskoltsev, Yu.K. Potrebenikov, Yu.P. Petukhov, V.E. Simonov, V.N. Spaskov, G.T. Tatishvili, P.Z. Hristov, I.P. Yudin (EXCHARM Collaboration), 2009, published in Pribory i Tekhnika Eksperimenta, 2009, No. 3, pp. 5–12.     

A laser spectrometer of field-asymmetric ion mobility

A method for analyzing a substance has been experimentally tested. The method combines the field-asymmetric ion mobility spectrometry and laser ionization of molecules under atmospheric pressure. Pulsed radiation of the fourth harmonic of an YAG: Nd³⁺ laser (λ = 266 nm) and a spectrometer with a cylindrical analysis camera were used. The results of detecting nitrocompounds—trinitrotoluene, cyclotrimethylenetrinitramine (hexogen, RDX), etc.—are presented. The experimental detection limits of the spectrometer are 5 × 10⁻¹⁵ g/cm³ (cyclotrimethylenetrinitramine) and ≤3 × 10⁻¹⁵ g/cm³ (trinitrotoluene).     

A plasma generator based on nonself-sustained low-pressure glow discharge with a large-volume hollow cathode

The results of studying nonself-sustained glow discharges in an electrode system with a hollow cathode with a volume of 0.25 m³ are presented. A high-current (up to 35 A) nonself-sustained glow discharge at low pressures (0.3–1.0 Pa) is initiated and sustained with the help of an auxiliary cold-hollow-cathode arc discharge. When the current of a nonself-sustained glow discharge increases from 2 to 35 A, its burning voltage changes from 40 to 300 V. These values are much lower than the voltage for a self-sustained glow discharge in the same electrode system. At a discharge current of 30 A, the electron concentration at the center of the hollow cathode is n _e ∼ 10¹⁰–10¹¹ cm⁻³ and the electron temperature is T _e ≈ 2 eV. The discharge considered can be used in the system for modification of materials and products.     

A low-voltage ionization chamber for the ITER

An ionization chamber with an operating supply voltage of 10 V has been designed for use at the ITER. The sensitivity of the chamber filled with air at atmospheric pressure is 100–200 times higher than the sensitivity of the chamber pumped down to a pressure of 10⁻³–10⁻⁴ Torr. It is shown that application of the supply voltage modulation technique allows the pickup noise to be substantially reduced; as a result, the amplifier can be located at a large (70–100 m) distance from the chamber. Results of the experiments aimed at testing this technique on the T-10 facility are described. Original Russian Text ? Yu.V. Gott, M.M. Stepanenko, 2009, published in Pribory i Tekhnika Eksperimenta, 2009, No. 2, pp. 117–121.     

A calorimetric spectrometer measuring single pulses of relativistic microwave generators

A calorimetric spectrometer measuring individual pulses radiated by wideband relativistic microwave oscillators is described. The calorimetric spectrometer comprises two calorimeters and a set of low-pass filters. In the development of such a spectrometer, the basic feature consists in the high radiation power (∼10⁸ W) and low pulse energy (∼1 J). To prevent the microwave surface discharge, the calorimeters have a rather large area (∼0.1 m²). The calorimeters’ sensitivity is 0.05 J. Frequency responses of the filters were measured experimentally and calculated with the help of a three-dimensional version of the KARAT computer code. The experimental spectrum of a wideband relativistic microwave plasma oscillator measured in a frequency range of 5–40 GHz is presented.