SU356965A1 - Pulsed radio spectrometer-relaxometer nuclear quadrupole resonance - Google Patents

Description

(54) PULSE RADIOSPECTROMETER-RELAXOMETER OF NUCLEAR SQUARE-HIGH RESONANCE |

The invention relates to radio spectroscopy and is intended to study the physicochemical properties of a solid by the method of nuclear quadrupole resonance (NQR) using the observed nuclear induction and spin echo signals arising in a substance after exposure to a test sample of radio frequency pulses.

Known pulse radiospectrometers NQR on the operating frequency of 2-70 MHz, 50-150 MHz, 150-300 MHz.

In known spectrometers, the test substance is placed inside a single-layer coil inductor, which is an integral part of the resonant system of a high-frequency pulse generator (LINE). As the operating frequency of the spectrometer increases, the number of turns in the coil decreases. This leads at frequencies above 250 MHz, firstly, to a significant decrease in the intensity of the high-frequency field inside the coil and, secondly, to a decrease in the "coupling of the magnetic fluxes of the NQR signal with the inductor, which significantly reduces the sensitivity, especially to NQR signals with wide lines and limits the operating range of known spectrometers.

NQR sensor with high sensitivity in the operating frequency range of 300-1000 MHz.

In the proposed NQR spectrometer, an inductor (spiral resonator) is used, which is tuned to the working frequency of the HWF using an automatic resonator tuning (AIR) system. GIHF and local oscillator are made on coaxial type circuits, which allows to cover the working range of 300-1000 MHz.

The drawing shows the block diagram of the proposed spectrometer.

The high-frequency energy of the generator 1 through an attenuator 2 acts on the resonator 3 - an inductor with the test substance. The signal "echo matter" is received in the receiving path of the spectrometer through the signal mixer 4 by the receiver 5. The weak signals are accumulated in the accumulation unit 6. The resonator is tuned to the operating frequency of the IHRF by means of the APR 7, through the pulse unit 8.

Using a mixer 9 for the automatic frequency control (AFC) of the local oscillator 10, as well as the AFC block I and the frequency adjusting mechanism 12, an automatic conjugation of the local oscillator and LIHF is provided. The scheme includes mechanisms for restructuring of the GIHR 13.

In the proposed spectrometer, the inductor is not included directly in the oscillatory system of gIHF.

This, firstly, greatly simplifies the design of the GIVCH, makes it similar to the local oscillator design, secondly, most significantly, it allows you to choose an inductor with a large number of turns, and therefore increase the intensity of the high-frequency magnetic field inside the sample coil, t . e. increases the efficiency of observation of the NQR signal. Third, the possibility of thermostating the sample. A coaxial-type resonator with an internal spiral conductor (spiral resonator) was chosen as the inductor. Smooth restructuring of the resonator is carried out by a constructive end capacitance. This makes it possible to investigate matters with different electrical and magnetic permeabilities at different temperatures. The operating range of the spectrometer is divided into subbands, which are determined by the resonator used.

Subject invention

Pulsed radio spectrometer-relaxometer nuclear quadrupole resonance, which contains a high-frequency pulse generator and a local oscillator, interconnected by an automatic frequency control system, an inductor, a pulse unit, a receiving device, an accumulation unit and a signal observation device, characterized in that, in order to increase sensitivity

a high-frequency spectrometer, 300–1000 MHz, the inductor is made as a separate spiral-type resonator connected to the unit by automatic adjustment of the resonator, and the local oscillator and high-frequency pulse generator are made on coaxial-type circuits.

//