JPS6062053A - Medical mass spectrometer - Google Patents

Abstract

PURPOSE:To increase the life of a heater by preventing any wear of the heater which might be caused by an ineffective thermionic current by judging whether the positional relationship between the heater and an ion source is good or bad. CONSTITUTION:The ratio of a thermionic current flowing into a trap electrode 6 to the total thermionic current discharged from a heater 4 is obtained in order to judge whether the positional relationship between the heater 4 and the slit 5 of an ion source is good or bad. The level of the thus obtained ratio is displayed on a displayer 17. At the same time, it enters one of the input terminals of a comparator 18 and compared with a predetermined threshold level (E119) to drive an alarm circuit 20 when the above level is not higher than the threshold level or a thermionic current which can contribute to ionization decreases to below a certain percentage level. When an alarm is produced by the alarm circuit 20, it is possible to introduce thermions discharged from the heater 4 efficiently into the ion source by controlling the positional relationship between the heater 4 and the slit 5.

Description

[Detailed description of the invention] [Technical field of invention] This invention relates to a medical mass spectrometer.

[Technical background of the invention and its problems] In recent years, there has been an increasing need for measuring oxygen consumption and carbon dioxide production in the fields of pulmonary function testing and patient monitoring. In order to perform these measurements, it is essential to measure the concentrations of oxygen and carbon dioxide in the breathing gas. On the analysis side, infrared absorption method,
Although methods using electrode methods and the like have been developed, mass spectrometry is the superior method for measuring oxygen and carbon dioxide simultaneously and with high precision.

However, this mass spectrometry method also has problems. That is, in order to achieve highly accurate measurement using water droplets, it is necessary to stably ionize the breathing gas. Since ionization is carried out by the collision of thermionic electrons, a beam of focused thermionic electrons of sufficient 1Pr is required for 7'C to maintain accurate measurement. For this reason, a method is generally used in which a thermionic beam emitted from a heater is guided to an ion source through a slit. However, because it is difficult to determine the optimal positional relationship between the heater and the slit, the thermoelectrons emitted from the heater are sometimes measured without being efficiently sent to the ion source. In order to prevent this and maintain accurate measurements, an increase in the amount of thermionic emission from the electron beam is required. However, in this case, there is a problem that the consumption of the heater increases due to the inactive thermionic current blocked by the slit among the thermionic electrons emitted by the heater, and the life of the heater is shortened.

[Purpose of the Invention] The invention improves the drawbacks of the conventional analyzer described above, and is a medical mass analyzer that can determine whether thermionic electrons emitted from the heater are being efficiently guided into the ion source. [Summary of the Invention J9] This invention aims to provide an analyzer in which thermionic electrons emitted from a heater are obstructed by conductive islands and slits in the ion source and are therefore ineffective. Measure the thermionic current that has become irradiated, and determine whether the positional relationship between the heater and the slit of the ion source is good or bad based on the ratio of the two, and determine whether the thermionic electrons emitted from the heater are efficiently guided into the ion source. It is designed to determine whether or not there is a vehicle.

[Effects of the Invention] According to the present invention, since it is possible to determine whether the positional relationship between the heater and the slit of the ion source is good or bad, it is possible to prevent the heater from being worn out due to an invalid thermionic current, thereby extending the life of the heater. Become.

Furthermore, the fact that the heater, once installed, deforms over time can serve as a guideline for optimal design of the structure of the heater itself.

[Embodiments of the Invention] Hereinafter, the present invention will be described in detail with reference to embodiments of the drawings. A sample gas led through a gas introduction pipe (1) enters an analysis tube (2) and is sent into an ion chamber (3). The ion chamber (3) is maintained at voltage ■1. Thermionic electrons for ionizing the sample gas are supplied from the heater (4). The heater (4) is heated by an electric current, and the voltage V2 from the ion chamber (3) is applied. (Thermionic electrons emitted from the heater (4), which is kept at a low voltage, are focused on the ion chamber (3) by the sleeve of the ion chamber (3).
It flows into. Most of the remaining thermoelectrons collide with the sample gas in the ion chamber (3), ionize the gas, and then flow into the front trap electrode (6). The trap electrode (6) is kept at a higher voltage than the ion chamber (3) by a pressure 4. The ionized gas molecules are pushed out by the beam force (7) and sent into the ion lens (9) through the slit (8). Libera electrode (
7) is kept at a higher voltage than the ion chamber (3) by the stain pressure ■5.

Now, the current flowing into the trap electrode (6) is caused by the resistance RId
It is detected as a voltage by I and amplified by an isolation amplifier I. On the other hand, the trap electrode (6) and the ion chamber (3)
)K flowing in, that is, the total thermoelectron current emitted from the heater (4), is detected as a voltage by the resistor RJ3, and is amplified by the isolation amplifier a3.

Next, the outputs of the isolation amplifier 1ll) and Q31 are input to the divider circuit QIK at the same time that each value is displayed on the display (1→, (to)), and the ratio of the two, that is, the trap electrode (6)
The thermionic current that contributed to the ionization of the gas flowing into the
The ratio of the total thermal electron current emitted from the heater (4) is output from the divider circuit ae. The value of this ratio is displayed by the indicator αη and at the same time is compared with a preset threshold value E1α1 entered at one input terminal of the comparator θ barrel. When it decreases below the percentage, the alarm circuit (■) is activated. When an alarm is generated by the alarm circuit (A), K adjusts the positional relationship between the heater (4) and the slit (5).
Adjustment can be made so that the emitted thermoelectrons can be guided into the ion source more efficiently.

In the above embodiment, the heater (4) and the ion source slit (5) are determined by taking the ratio of the thermionic current flowing into the trap electrode (6) and the total thermionic current emitted from the heater (4). ), but the ion chamber (3) is more sensitive than the heater (4).
It is also possible to detect the value of the thermionic current flowing into K and to calculate the ratio with the thermionic current flowing into the trap (6).

[Brief explanation of drawings]

The drawing is a block diagram of an embodiment of the present invention. 01... Gas introduction pipe, 3... Ion chamber, 4...
Heater, 5...Slit, 6...Trap electrode, 11. ．． 13...Isolated amplifier,
16...Division circuit. Agent: Patent attorney Kensuke Chika (and 1 other person)

Claims (3)

[Claims] (1) An ion chamber into which gas is introduced, a heater that emits thermionic electrons to ionize the gas in the ion chamber, and a trap electrode that captures thermionic electrons released from the heater and penetrating the ion chamber. , comprising means for detecting the thermionic current flowing into the trap electrode, and calculation means for calculating the ratio of the thermionic flow rate detected by the means to the amount of thermionic current emitted from the heater. Medical mass spectrometer. (2) The calculation means detects the total hot electron current emitted from the heater, and calculates the ratio of the hot electron current flowing into the trap electrode to the total hot electron current. A medical mass spectrometer according to scope 1. (3) A claim characterized in that the calculation means detects the thermionic current flowing into the ion chamber from the heater, and calculates the ratio of the thermionic current flowing into the trap electrode to this thermionic current. Medical mass spectrometer 0 described in paragraph 1