Yu. V. Chichagov

A portable mass spectrometer for direct monitoring of gases and volatile compounds in air and water samples

A portable automated mass-spectrometric system allows direct testing of gases and volatile substances in both air and water samples in in situ and on-line modes and is intended for studies in ecology, oceanology, and for testing technological processes. The parameters, the instrument design and operating modes, and the units included in it are described. The choice of the design of the membrane input system, which ensures low threshold levels of detecting goal compounds (down to a few ppb for toluene and benzene) and the dependence of this choice on the measurement mode and the state and composition of the investigated sample are considered. The results of tests of the mass-spectrometer in the mode of direct selective and total inspection are presented.

Small-size mass spectrometer for determining gases and volatile compounds in air during breathing

We describe an automated mass spectrometer for diagnostics of deceases from the composition of exhaled air. It includes a capillary system, which performs a rapid direct feeding of the sample to the instrument without changing substantially its composition and serves for studying the dynamics of variation of the ratio between various components of exhaled air. The membrane system for introducing the sample is intended for determining low concentrations of volatile organic compounds which are biomarkers of pathologies. It is characterized by selective transmittance and ensures the detection limits of target compounds at the parts per million–parts per billion (ppm–ppb) level. A static mass analyzer operating on permanent magnets possesses advantages important for mobile devices as compared to its dynamic analogs: it is more reliable in operation, has a larger dynamic range, and can be used for determining the concentration of components in the mixture one-by-one or simultaneously. The curvilinear output boundary of the magnetic lens of the mass analyzer makes it possible to reduce its weight and size by 2.5 times without deteriorating the mass resolution. We report on the results of testing of the instrument and consider the possibility of its application for early detection of deceases of respiratory and blood circulation system, gastrointestinal tract, and endocrine system.

A membrane inlet system equipped with a piezoelectric lock for introduction of gaseous samples into a mass-spectrometer

The design of a membrane inlet system, which is equipped with a metal-sealed piezoelectric vacuum lock, for introducing samples into a mass spectrometer, is described. The membrane interface is characterized by a selective permeability for volatile target compounds and allows their detection in air with a high sensitivity in a proximate measurement mode using automated portable or mobile mass spectrometers. The system provides short instrument response times (∼1 s) owing to the use of a thin membrane material (tens of microns) and excludes hazardous consequences of a possible destruction of the membrane. The inlet system is controlled via application of voltage to the lock, thus enabling blocking of the gas flow that is supplied to the instrument within several hundredth parts of a second. Testing results are presented.

A Membrane Inlet for a Portable Mass Spectrometer

A system of membrane injection of a sample into a portable mass spectrometer which is used for determining the concentration of organic components in complex mixtures is described. Spectra of samples containing alkanes from methane to hexane have been measured. The data obtained using the membrane and diaphragm inlets to are compared. The potentialities of membrane inlets for portable mass spectrometers intended for environmental and process monitoring are shown.

Interfacing of a Coordinate-Sensitive Detector Based on Charge-Coupled Devices for Recording Ions with a Portable Static Mass Spectrograph

An IDS 2030 IonCCD coordinate-sensitive detector (Analytical/CMS Field Products) is interfaced with a small-sized mass spectrograph developed at the Ioffe Physical Technical Institute, Russian Academy of Sciences. The measurement data obtained with the mass spectrograph using an IonCCD detector and a Magnum-5901-37029PS channel secondary electron multiplier (Photonics USA Inc., United States) are compared. The results of measurements are discussed, and the prospects for using the IonCCD coupled with a microchannel plate are assessed.

Electronic and software systems of an automated portable static mass spectrometer

The electronic systems of a small high-sensitivity static mass spectrometer and software and hardware tools, which allow one to determine trace concentrations of gases and volatile compounds in air and water samples in real time, have been characterized. These systems and tools have been used to set up the device, control the process of measurement, synchronize this process with accompanying measurements, maintain reliable operation of the device, process the obtained results automatically, and visualize and store them. The developed software and hardware tools allow one to conduct continuous measurements for up to 100 h and provide an opportunity for personnel with no special training to perform maintenance on the device. The test results showed that mobile mass spectrometers for geophysical and medical research, which were fitted with these systems, had a determination limit for target compounds as low as several ppb(m) and a mass resolving power (depending on the current task) as high as 250.

Cherenkov gamma-ray telescopes: Past, present, future. The ALEGRO project

A brief overview of the history of atmospheric Cherenkov gamma-ray telescopes is given. Topical problems of modern astrophysics and fundamental physics to be solved with these instruments are listed. The ALEGRO project of a low-threshold gamma-ray observatory is characterized in detail. The aim of this project is to examine cosmic gamma-ray sources (especially the rapidly variable gamma-ray sources, gamma-ray transients) with high statistics of detected photons in the energy range of 5–50 GeV.

ALEGRO: A new-generation Cherenkov gamma observatory

The concept of a new-generation terrestrial Cherenkov gamma observatory is proposed on the basis of the results of numerical modeling and research and development work. The key parameters of this observatory are estimated. Its primary objective should be the observation of cosmic gamma-ray sources in the 5–50 GeV energy range. Neither ground-based Cherenkov gamma observatories nor orbital gamma telescopes are presently able to perform such observations efficiently.

Signal generator exciting an electromagnetic field for ion beam transport to the vacuum chamber of a mass spectrometer

A high-voltage high-frequency signal generator is described that excites an electric field for ion beam transport from an ion source to the vacuum chamber of a mass spectrometer. Excitation signals to the number of two are high-frequency sine-wave out-of-phase signals with the same amplitudes. The amplitude and phase of the signals vary from 20 to 100 V and from 10 kHz to 1 MHz, respectively. The generator also produces a controlled bias voltage in the interval 50–200 V. The frequency and amplitude of the signals, as well as the bias voltage, are computer-controlled via the USB interface.

Setup for taking the radiation spectra of wideband semiconductors

A setup is developed for measuring the spectra of wideband semiconductors (III nitrides) and related heterostructures. The setup makes it possible to trace the time distribution of the luminescence intensity at a fixed wavelength with a resolution of ±5 ns and a sampling rate of up to 10 MHz in the time interval from several microseconds to several hundreds of microseconds. Also, it plots the integral intensity of luminescence versus the wavelength. Precision measurement conditions are provided.