JPH0355239Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a time-of-flight mass spectrometer, and more particularly to an apparatus with improved S/N ratio.

[Prior art] A time-of-flight mass spectrometer irradiates a sample with an ion beam, irradiates secondary neutral particles emitted from the sample with a laser pulse beam in the ultraviolet region to ionize them, and detects the ions. Mass spectrometry is performed based on the difference in flight time to the instrument.

FIG. 2 is a diagram for explaining such an apparatus, where 1 is a sample, and when the sample 1 is irradiated with an ion beam 2, secondary neutral particles 3 are emitted from the surface of the sample 1. The secondary neutral particles 3 are guided into an ionization region (ion source) 5 formed within an analysis tube 4. The ion source 5 is irradiated with a laser pulse beam 7 from a laser source 6, and the secondary neutral particles 3 emitted from the sample 1 are ionized by the laser pulse beam 7. After the ionized ions are accelerated by an accelerating electrode in the ion source 5, the ion reflector 8 is placed in the analysis tube 4.
fly towards. Ions flying in the direction of the ion reflector are eventually decelerated by the deceleration electric field 8a formed in the ion reflector 8, further reflected by the reflected electric field 8b, and detected by the channel plate 9. Ions detected by the channel plate 9 are output as an amount of charge proportional to the number of ions. This electrical signal from the channel plate 9 is converted into a voltage and amplified by a preamplifier 10, as shown in FIG. 1
1 is a filter amplifier, and the electric signal (voltage) from the preamplifier 10 is converted by the filter amplifier 11 into an electric signal as shown in FIG.
It is recorded as a mass spectrum by the transient recorder 12.

[Problems to be solved by the invention] By the way, in such an apparatus, the laser pulse beam 7 from the laser source 6 is transmitted through the analysis tube 4.
The laser light from this laser pulse beam is diffusely reflected within the analysis tube 4, the ion reflector 8, etc., and is finally detected by the channel plate 9. This diffusely reflected laser light is also an input signal to the channel plate 9, like the ions, and the large signal A caused by this laser light is much larger than the detection signal B caused by ions, as shown in FIG. Therefore, a relatively small signal (detection signal) caused by the ions is superimposed on a large signal (background) caused by the laser light diffusely reflected within the analysis tube. Therefore, if the gain of the channel plate 9 is increased in order to sufficiently detect relatively small signals due to ions, the level of the output voltage of the preamplifier 9 will exceed the allowable value of the input voltage of the filter amplifier 10. Therefore, the gain of the channel plate 9 cannot be made sufficiently large, and therefore,
It is not possible to improve the S/N ratio.

The purpose of the present invention is to eliminate the above-mentioned drawbacks and provide a time-of-flight mass spectrometer that improves the S/N ratio by preventing diffuse reflection of laser light in the analysis tube by a laser beam for ionization. There is.

[Means for Solving the Problems] The present invention for achieving the present purpose is to irradiate a sample with an ion beam, and collect secondary neutral particles emitted from the sample into an analysis tube that is irradiated with the laser beam. In an apparatus that performs mass spectrometry by guiding the ions to an ionization region of It is characterized by the fact that it is coated with paint.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a schematic diagram of an embodiment of the present invention, and the same components as those of the conventional device shown in FIG. 2 are given the same numbers. In FIG. 1, reference numeral 13 denotes a conductive, black, non-reflective paint applied to the inside of the analysis tube 4.
It is coated on the portion where the laser light from the ion reflector 8 is diffusely reflected when it is incident. When a conductive non-reflective paint is applied inside the analysis tube 4,
Even if the laser light enters the analysis tube 4, the laser light is absorbed by the non-reflective paint inside the analysis tube and is not diffusely reflected, so that the laser light is not detected by the channel plate 9. Therefore, the background caused by laser light diffusely reflected in the analysis tube, etc., unlike the conventional apparatus, is hardly detected, and only relatively small signals caused by ions are detected, thereby improving the S/N ratio. or,
Since the paint applied to the inside of the analysis tube is conductive, it does not affect the flight trajectory of the ions, which are not charged by the ions and fly, so the resolution is not affected.

[Effects of the invention] As detailed above, according to the invention, since the conductive non-reflective paint is applied to the inside of the analysis tube, even if laser light from a laser beam for ionization enters the inside of the analysis tube, A time-of-flight mass spectrometer is provided in which diffuse reflection of this laser light can be prevented, thereby improving the S/N ratio.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of an embodiment of the present invention;
The figure is a schematic configuration diagram of a conventional device, and FIGS. 3, 4, and 5 are diagrams for explaining the conventional device. DESCRIPTION OF SYMBOLS 1...Sample, 2...Ion beam, 3...Secondary neutral particles, 4...Analysis tube, 5...Ion source, 6...
... Laser source, 7 ... Laser pulse beam, 8
...Ion reflector, 9...Channel plate,
10...Preamplifier, 11...Filter amplifier, 12...Transient recorder, 13...
...Non-reflective paint film.

Claims (1)

[Scope of utility model registration request] irradiating a sample with an ion beam, guiding secondary neutral particles emitted from the sample to an ionization region in an analysis tube where the laser beam is irradiated, and ionizing them;
An apparatus for performing mass spectrometry by reflecting the ions with an ion reflector formed in the analysis tube and determining the difference in flight time to the detector, characterized in that the inside of the analysis tube is coated with a conductive non-reflective paint. Time-of-flight mass spectrometer.