JPS6235253Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a final charged particle detection device in a mass spectrometer or various electron energy spectroscopy devices.

In the above-mentioned charged particle analyzer, in the final charged particle detection, which detects specific charged particles sorted by mass or energy, there is no error in the path other than the regular charged particle optical system that sorts out the specific charged particles. Certain floating charged particles enter and become background noise in the detection signal. Such problems are particularly severe in secondary ion mass spectrometers and gas chromatograph mass spectrometers. The specific particles that have passed through the regular charged particle optical system, that is, the target charged particles to be detected, and the floating charged particles have different energies when they enter the detector, so the energy changes depending on the energy of the incident particles. If the detector outputs a pulse signal, it is possible to level-sort the output signal and distinguish between the detection signal of the target charged particle and the detection signal of the floating charged particle. Detectors such as the above do not have responsiveness to the energy of incident charged particles with energy above a certain value, so they cannot reduce the level of background noise.
It has been difficult to obtain detection sensitivity commensurate with the high sensitivity of electron multiplier tubes.

The purpose of this invention is to remove the influence of floating charged particles, increase the S/N ratio, and obtain high sensitivity in a charged particle analyzer that uses an electron multiplier tube as a charged particle detector. A charged particle detection device is provided in which a grid is provided in front of a charged particle entrance and an appropriate voltage is applied to repel floating charged particles so that they do not enter an electron multiplier. The present invention will be explained below with reference to Examples.

The figure shows an embodiment of the present invention in which a channel tron is used as an electron multiplier. 1 is a channel tron, I is a charged particle entrance, and C is an electron collector. HV is a high-current, high-voltage power supply that applies an appropriate voltage between the collector C and the electron exit end of the channeltron 1 and between both ends of the channeltron 1. Three grids G1, G2,
G3 is placed. 2 is grid G1, G2,
It is an insulator that supports G3. This example shows the case of positive ion detection, where the charged particle entrance I and the third grid G3 of the channeltron 1 are at ground potential, and the first and second grids G1 and G2 are at ground potential.
A positive voltage of Vr volts, which is obtained by dividing the output voltage of the high-voltage DC power supply HV, is applied. Since the wall of the vacuum chamber of the analyzer is at ground potential, the first grid G1 in the figure
A decelerating electric field is formed in front of the first grid G1 for positive ions that enter the channel tron 1 from the left side of the grid, and positive ions with energy less than Vr electron volt are repelled by G1 and enter the channel. Unable to enter Tron. In general, floating ions have lost more energy than ions that have passed through a regular charged particle optical system, so Vr
By appropriately selecting the target ions, the target ions can be made to enter the channeltron, while floating ions of lower energy can be repelled, making it possible to significantly reduce the noise level.

In the above embodiment, the grids for repelling unnecessary ions are double grids of G1 and G2, but they may be single grids. By doubling this grid, you can make the individual grids coarser and have the same effect as a narrower single grid, and if you make the grid lines of the front and back grids overlap correctly in the front and back, it will be easier to detect. Since the target ions are incident perpendicularly to the grid plane, it is possible to reduce the number of ions that collide with the grid lines and cause loss.

The device of the present invention has almost the same energy selectivity as an electron multiplier because the above-mentioned configuration prevents floating particles with lower energy than the target charged particles to be detected from entering the detector. When using a detector that does not eliminate the noise caused by floating charged particles, which cannot be removed using electrical circuits, the noise caused by floating charged particles is significantly reduced, and the high sensitivity of electron multiplier tubes can be fully utilized. An analytical device is obtained.

[Brief explanation of the drawing]

The drawing is a circuit diagram of an apparatus according to an embodiment of the present invention. 1... Channel tron, I... Charged particle entrance, HV... High voltage DC power supply, G1, G2, G3...
...Grid.

Claims (1)

[Scope of utility model registration request] A charged particle detection device in which a grid is disposed in front of a charged particle entrance of an electron multiplier, and a voltage is applied to the grid to prevent low-energy charged particles from entering the electron multiplier.