Instruments and Experimental Techniques最新文献

The system of magnetic measurements in large volumes based on Hall probes has been developed in the Institute for High Energy Physics (IHEP). An example of its practical use to measure the topography of the spectrometric magnet’s field of the SPASCHARM experiment at the U-70 accelerator complex is described. In these measurements, the special attention has been paid to calibrations, monitoring the stability of parameters, and of the accuracy in positioning the probes in the magnet aperture and in their orientation. Further development of the system and the study of its capabilities for improving the accuracy, reducing the measurement time and, in general, increasing its flexibility in applications are also presented.

The NICA (Nuclotron-based Ion Collider fAcility) accelerator complex consists of a collider and an injection complex. The injection complex of heavy ions includes ion source, linear accelerator, a 25 T m SC Booster synchrotron, a 38 T m SC synchrotron Nuclotron, and beam transfer lines. One of the main tasks in complex commissioning and tuning are the measurement and correction of the beam closed orbit. The software, written for orbit correction, was successfully tested during the commissioning runs. The paper describes the software and hardware developments for orbit measurement and correction.

Molecular beam mass spectrometry (MBMS) has been adapted at the gas dynamic stand LEMPUS-2 to study the free molecular beam particle-scattering process on particles of the background gas. The verification of the used technique in noncondensing flows was carried out, and the results of measuring the effective scattering cross sections of argon atoms and nitrogen molecules were compared with the known literature data. The process of atoms and small argon clusters (oligomers) scattering on carbon dioxide particles located in the background space at different average sizes of clusters 〈N〉 formed in the flow is investigated. When 〈N〉 ≈ 48, the obtained scattering cross-sections for argon atoms, dimers, and trimers is 39, 17, and 6 Å², respectively. With an increase in the average cluster size in the flow, the effective scattering cross-section of argon atoms decreases. The paper discusses the causes of the detected effect as well as the features of MBMS use for the study of supersonic clustered jets.

The use of one of the electrodes of a small-sized vacuum spark gap as a single Langmuir probe made it possible, without violating the conditions for the formation of the initiating discharge, to record with high time resolution the flows of charged particles and plasma emitted from the starting system and to measure their main parameters. Emission of suprathermal electrons and ions and turbulent plasma was detected. The method of time integration of the signal from the probe confirmed the hypothesis that the anomalously large ion saturation current to the probe is associated with buildup of electrostatic oscillations in the plasma. Signs of macroscopic charge separation at the leading edge of the plasma flow were discovered. The energies of suprathermal particles, the electron temperature, and the density of the emitted plasma were estimated. The probe method has proven to be a completely reliable and productive tool for studying fast processes.

The proposed concept of the design and electronics of a fast monitor of the position and intensity of a synchrotron radiation beam is presented. Sensors based on radiation-resistant materials, leucosapphire and silicon carbide, are investigated as possible detectors for the fast beam monitor. Tests of detectors based on leucosapphire and silicon carbide have shown that both materials are suitable as photodetectors for recording fast signals from short flashes of a white beam of synchrotron radiation from each electron bunch in the storage ring. Current pulses generated by detectors based on these materials have a duration of up to 20 ns. In this case, the signal generated by a sensor based on silicon carbide exceeds the corresponding signal from a sensor based on leucosapphire by 3.9 times, provided that the thickness of the sensors is the same.

The use of electromagnetic valves for generating pulsed flow modes of a high-density supersonic jet in the second and submillisecond ranges is analyzed. It has been shown that “slow” second-range valves do not allow achieving a quasi-stationary mode with a high gas flow rate compared to a stationary outflow; submillisecond-range “fast” valves generate gas pulses with parameters necessary to simulate high-flow conditions at background gas pressures that do not overload the high-vacuum pumping system. It is found that the submillisecond valve provides the ability to simulate instantaneous flow rates of up to several tens of grams of a product per second in a pulse at pressures in the prechamber of up to 2 MPa and a pressure in the surrounding space of 1–3 Pa. A set of sonic and supersonic nozzles has been implemented with an electromagnetic valve device and power-supply and control systems that provide the gas outflow from the nozzle prechamber during a controlled period of time from 0.3 to 1.5 ms with a given duty cycle varying from several tens to thousands. The generated gas pulses have a trapezoidal shape with a quasi-stationary core.

In Tokamak experiments, the MDSPlus database is commonly used for data management. It collects and stores data from each subsystem. However, the complexity and high coupling of the system make it vulnerable to failure. If one module malfunctions, it can cause the entire system to collapse, hindering future maintenance and expansion. To address this issue, this paper proposes a data acquisition and management system based on the PCI-1706 multi-channel synchronous data acquisition cards and the MDSPlus database, along with a data Scope program. The data acquisition system employs a multi-process design to achieve synchronization among multiple channels by using an external clock and trigger signal. Meanwhile, the data management system utilizes MDSPlus, and a client Scope program is developed to enable remote data access and analysis. The reflection memory card is employed to establish a network for data interaction between the server and the acquisition machine, enhancing storage speed. Experimental tests have confirmed the multi-card and multi-channel synchronous acquisition functions of the data acquisition system, as well as the remote data access capability of the Scope program. This system exhibits advantages such as low cost, simple structure, stable operation, and easy maintenance. It proves to be effective in Tokamak device experiments and can also serve as a reference for other data management systems.

A setup design is proposed for measuring magnetization curves by the differential sweep method. On the described setup, a number of magnetization curves were measured for both classical magnetic fluids and samples obtained by their solidification. The measurement results are compared with the results obtained using a vibrating-sample magnetometer. It is shown that the vibrating-sample magnetometer gives significantly lower values compared to the differential method when measuring the magnetization of a magnetic fluid. When measuring the magnetization of a cured magnetic-fluid sample, a complete coincidence of the results obtained by both measurement methods is observed. The discovered phenomenon is explained by the aggregation of particles in the magnetic fluid under the influence of a magnetic field. Estimations of the relative delay in the movement of aggregates are consistent with the observed divergence in the magnetization magnitude.

A technique based on thermoluminescent LiF(Mg,Ti) lithium fluoride detectors has been developed to study the spectral composition of  X-ray radiation of femtosecond laser plasma in a wide range of photon energies from 1 keV to almost 1 MeV. This technique has been experimentally tested together with matrix-type semiconductor detectors. The plasma parameters have been measured under the action of a femtosecond pulse with a peak intensity of ~10¹⁸ W/cm² on a metal (copper) target, and good agreement is demonstrated between data from different detector types in terms of determining both the spectrum shape and the coefficient of the laser-pulse energy conversion into an X-ray flux. The temperature of hot electrons has been estimated, and its value exceeds 100 keV. The X-ray flux of copper K-lines, which exceeds 10⁹ per shot, has been determined. The advantages and drawbacks of techniques for measuring spectra in problems of laser-plasma interaction are considered.

Bit flip errors were detected in microcontroller memory cells after irradiation by laser accelerated proton beams. The protons with energies of up to 6 MeV originated from the back surface of 6-μm-thick aluminum foils under the action of laser pulses from 200 TW femtosecond facility. It was established that the failures were caused by single event effects and cross section of the effects was estimated. The experiment demonstrates for the first time the possibility of using laser-plasma accelerators to study single event effects from low-energy protons.