The detection device and method of the ion gas leak detector mainly rely on the principle of mass spectrometry. By ionizing gas molecules and using a magnetic field to deflect them, different masses of gas ions are separated and detected according to the different deflection radii. The following introduces the core principle, detection device, detection method, key indicators, and application scenarios from five aspects:
core principle
Ionic gas leak detectors, especially helium mass spectrometer leak detectors, are based on mass spectrometry technology as their core principle. Mass spectrometry technology is a technique that ionizes gas molecules and separates them based on the mass to charge ratio (mass to charge ratio) of gas ions under the action of electric and magnetic fields. In leak detectors, this principle is used to detect leaks of specific gases such as helium.
detection device
The detection device of the ion gas leak detector mainly includes the following parts:
Ion source: used to ionize gas molecules entering the leak detector, forming positive ions. Ionic sources typically emit electrons by heating a filament, which collide with gas molecules to ionize them.
Analyzer: It is a uniform magnetic field region used to separate ions of different masses by moving them along different trajectories. The analyzer is usually designed using magnetic polarization conversion or quadrupole mass spectrometer.
Collecting electrode: used to collect specific ions (such as helium ions) that pass through the outlet slit of the analyzer, and convert them into electrical signals through resistors for amplification and measurement.
Vacuum system: including mechanical pumps, molecular pumps, etc., used to provide the vacuum conditions required for the normal operation of leak detectors. The vacuum system ensures that gas ions can move freely in the analyzer without interference from air molecules.
Electrical system: including feeding, control, amplification and other parts, used to provide power for ion sources, analyzers, etc., and control the working status of leak detectors. At the same time, the electrical system is also responsible for amplifying the weak electrical signals transmitted from the collection electrode for accurate measurement.
detection method
The detection methods of ion gas leakage detector mainly include the following:
Spray method: Connect the tested device or component to the leak detector, and use a spray gun filled with leak indicating gas (such as helium) to spray sequentially at suspicious locations in the tested container. If there is a leak, the gas will enter the interior of the container and enter the ionization chamber, which will be indicated by the leak detector.
Helium hood method: Use a hood (such as a plastic bag) to wrap around the suspicious part or the entire container being inspected, and then fill the hood with leak gas. If the instrument or sound system reacts, it indicates that there is a leak in the covered part. This method increases the concentration of the leak gas and increases its residence time in the leak hole, thereby improving the sensitivity of leak detection. But the disadvantage is that it cannot accurately determine the location of the leakage hole, so it is usually necessary to use the spraying method to further determine the specific location of the leakage hole.
Suction nozzle method: Fill the inside of the inspected container with several atmospheres of leak gas, and then use a specially designed suction nozzle (flow limiting membrane hole or conduit) to search outside the container. When there is a leak in the container, the leaked gas will escape outward through the leak hole. When the suction nozzle is facing the leak hole position, the leak will be sucked into the mass spectrometer together with the surrounding air, producing a strong signal.
key metrics
Sensitivity: Refers to the minimum leakage rate that a leak detector can detect. The higher the sensitivity, the smaller the leakage that the leak detector can detect.
Resolution ability: refers to the ability of a leak detector to distinguish ions of different masses. The higher the resolution, the more accurate the leak detector is in identifying gases.
Minimum detectable partial pressure: refers to the minimum partial pressure of a specific gas component corresponding to the difference between the low and high values of the output current drift (i.e. noise value) of a leak detector after operating for a period of time without an ion peak. The smaller the minimum detectable pressure, the stronger the detection capability of the leak detector.
Maximum working pressure: refers to the maximum pressure that the leak detector can withstand under normal working conditions. Beyond this pressure, the sensitivity of the leak detector may decrease or be damaged.
Application scenarios
Ionic gas leak detectors are widely used in various scenarios that require gas leak detection, such as:
Vacuum equipment manufacturing and maintenance: used to detect leaks in vacuum systems and ensure the normal operation of vacuum equipment.
In the field of nuclear energy, it is used to detect helium gas leaks in equipment such as magnetic resonance imaging (MRI) scanners, ensuring the safety and stability of the equipment.
Manufacturing industry: used for product quality assurance testing, such as detecting gas cylinder inflation rooms, conduit devices and edges, and leakage of gas stored in drum shaped cylindrical containers.
Medical field: used for complete testing of anesthetic gas bottles, catheters, membrane materials, and leak detection of glove boxes.