JPH0414845Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a detector that is used in a measuring instrument such as a mass spectrometer and detects + ions, - ions, etc.

(Prior Art) Secondary electron multipliers, channeltrons, multichannel plates, and the like are widely used as detectors for detecting minute ion currents and electron currents in mass spectrometers and the like.

Furthermore, a Daly type secondary ion detector is also used, in which a scintillator is disposed opposite to an ion-electronic converter, and a photomultiplier tube is provided to receive light generated from the scintillator.

In a Dalley-type secondary ion detector, electrons generated from an ion-electron converter are drawn in by an electric field between the scintillator and the scintillator and collide with the scintillator, and the light generated from the scintillator is detected by a photomultiplier tube.

Furthermore, by inserting a secondary electron multiplier between the collector slit and the secondary electron multiplier, the ions passing through the collector slit are accelerated by the inserted secondary electron multiplier. A detector with increased sensitivity has been reported (MASS SPECTROSCOPY, Vol. 33, No. 2).
No., pp. 145-147 (1985)).

According to this detector, it is reported that detection sensitivity can be obtained about three times as much as that of a conventional detector using only a secondary electron multiplier.

However, in the case of these detectors, there is a limit in detection sensitivity for trace analysis such as biological component analysis and pollution analysis.
The limit is about 1μl.

Increasing the voltage applied to the dynode in a secondary electron multiplier increases the gain, but since the noise is amplified along with the signal, the S/N ratio (signal-to-noise ratio) does not improve, and therefore the sensitivity increases. do not.

(Problem to be solved by the invention) Therefore, the inventors of the present invention have developed a detector that can significantly improve the detection limit, for example, approximately 10 times or more, compared to conventional secondary electron multiplier tubes. ,
We developed a detector with the structure shown in Figure 3.

In FIG. 3, 14 is a secondary electron multiplier tube as a multiplier, and seven stages of dynodes D _y1 to D _y7 are provided. The number of dynode stages can be changed as appropriate. A voltage is applied between the dynodes D _y1 to D _y7 so as to amplify the secondary electrons generated at each stage. A channel tron can also be used as a multiplier instead of the secondary electron multiplier 14.

A scintillator 22 is provided on the exit side of the secondary electron multiplier tube 14. A metal film 24 is formed on the surface of the scintillator 22. A scintillator 22 having a metal film 24 is placed at the outlet of the secondary electron multiplier tube 14 so as to face inside the secondary electron multiplier tube 14, and is integrated with the secondary electron multiplier tube 14 via an insulator 26. is firmly fixed. scintillator 2
2 can also be separate from the secondary electron multiplier 14.

A light guide 28 is provided on the back side of the scintillator 22.
A photomultiplier tube 30 is provided via the photomultiplier tube 30. The light guide 28 is made of synthetic resin, quartz glass, or the like, and has a structure that allows light to pass through efficiently.

Note that 16 is a deflector that controls the direction of charged particles incident on the first stage dynode D _y1 , and 18 is a deflector that controls the direction of secondary electrons emitted from the final stage dynode D _y7 and directs them to the scintillator 22. It is a guiding deflector.

Various materials are used for the scintillator 22, but one example is a phosphor with an RMA number of P46.
Y ₃ A _l5 O ₁₂ ; Ce can be mentioned. metal film 2
4 is, for example, an aluminum vapor deposited film.

In the detector shown in FIG. 3, the secondary electron multiplier tube 14
When a charged particle or a neutral particle is incident on the first stage dynode D _y1 , secondary electrons are generated from the dynode D _y1 . The secondary electron is the second stage dynode
_The amplified secondary electrons are amplified by D _y2 , and the amplified secondary electrons are further amplified by the third stage dynode _{D y3} , and _{so on .} The secondary electrons generated at the dynode D _y7 enter the scintillator 22 . The light generated by the scintillator 22 is guided to a photomultiplier tube 30 through a light guide 28 and detected.

By applying a voltage to the metal film 24 on the surface of the scintillator 22, the secondary electrons generated at the final stage dynode _Dy7 can be accelerated and made to enter the scintillator 22.

In the detector shown in FIG. 3, it is thought that the secondary electrons from the multiplier 14 are once converted into light by the scintillator 22, thereby reducing noise and improving the S/N ratio.

The object of the present invention is to enable a detector as shown in FIG. 3 to perform detection with even higher sensitivity and to perform detection over a wider dynamic range.

(Means for Solving the Problems) In the detector of the present invention, a multichannel plate is provided close to the final stage dynode or exit of the multiplier that converts incident particles into secondary electrons and amplifies them. A scintillator that converts electrons into light is provided at the exit of the channel plate, a photomultiplier tube is provided at a position that receives light from the scintillator, and a photomultiplier tube is provided between the multiplier and the multichannel plate to convert electrons into light. A first collector for collecting electrons is removably inserted, and a second collector for collecting electrons is removably inserted between the multichannel plate and the scintillator, and the output of the first collector and the output of the second collector are removably inserted. It is possible to select either the output or the output of the photomultiplier tube.

The objects to be detected in the present invention are charged particles and neutral particles, which are collectively referred to as charged particles.

(Embodiment) FIG. 1 shows an embodiment in which a secondary electron multiplier is used as a multiplier. It should be noted that the same parts as in FIG. 3 are given the same symbols and their explanation will be omitted.

D _y1 to _{D y12} are dynodes of the secondary electron multiplier tube 31 . Although this example shows one having 12 stages of dynodes, the number of stages of dynodes is not limited to this.

A multichannel plate 32 is provided close to the exit of the final stage dynode D _y12 . A scintillator 22 that converts electrons into light is provided at the exit of the multichannel plate 32, and a photomultiplier tube 30 is provided on the back side of the scintillator 22 to receive light from the scintillator 22. The output terminal of the photomultiplier tube 30 is led to a preamplifier.

From the first stage dynode D _y1 to the last stage dynode
A resistor r is provided between each of the dynodes up to D _y12 . A voltage V ₁ is applied between the first stage dynode D _y1 and the last stage dynode D _y12 to amplify secondary electrons between the dynodes, and a resistor r
It is divided by.

A potential difference V ₂ is applied between the final stage dynode D _y12 and the entrance surface of the multi-channel plate 32 in order to draw the electrons generated at the final stage dynode D _y12 into the multi-channel plate 32. Further, there is a potential difference V ₃ between the entrance surface and the exit surface of the multi-channel plate 32 for amplifying the electrons incident on the multi-channel plate 32.
is given.

In this embodiment, a secondary electron multiplier 31, a multichannel plate 32, and a scintillator 22 are integrally assembled. The photomultiplier tube 30 is provided so that its light receiving surface is in direct contact with the scintillator 22.

In the detector of this example, the first stage dynode
If an ion is incident on D _y1 as an example of a charged particle, the ion is amplified as an electron current between dynodes D _y1 to _{D y12} and then flows between the final stage dynode D _y12 and the entrance surface of the multichannel plate 32. It is accelerated by the potential difference and enters the multi-channel plate 32. The electron current amplified by the multichannel plate 32 is converted into light by the scintillator 22, and is amplified again as an electron current by the photomultiplier tube 30. The output signal from the photomultiplier tube 30 is sent to a signal processing system via a preamplifier.

In the embodiment of FIG. 1, the final stage dynode
An electrode plate serving as a collector for collecting electrons can be inserted between D _y12 and the entrance of the multi-channel plate 32, and a signal from the inserted collector is sent to the preamplifier via the wiring 34. Furthermore, an electrode plate serving as a collector for collecting electrons can be inserted between the outlet of the multi-channel plate 32 and the scintillator 22, and the signal from the inserted collector is sent to the preamplifier via the wiring 36. Make it. Then, the detection signal flow passes through the photomultiplier tube 30, the detection signal flow passes through the wiring 34, or the wiring 3.
6 can be selected.

When the signal strength is strong, a collector is inserted between the final stage dynode D _y12 and the entrance of the multi-channel plate 32 to read the signal, and when the signal strength becomes weak, the collector is inserted between the exit of the multi-channel plate 32 and the scintillator 22. A collector is inserted between them to read the signal, and when the signal intensity becomes the weakest, the signal is read through the scintillator 22 and the photomultiplier tube 30.

In this way, by changing the position at which the signal is read, detection with a wide dynamic range can be performed.

FIG. 2 shows another embodiment.

While the detector of FIG. 1 uses a secondary electron multiplier tube 31 as a multiplier, the detector of this embodiment uses a channel tron 40 as a multiplier.

A multichannel plate 32 is provided at the outlet of the channeltron 40. The arrangement of the multichannel plate 32, scintillator 22, and photomultiplier tube 30 is the same as in FIG.

A voltage V ₁ ' for amplifying secondary electrons is applied between the entrance and exit of the channel tron 40, and between the exit of the channel tron 40 and the entrance surface of the multi-channel plate 32, and between the entrance surface of the multi-channel plate 32. The same voltages V ₂ and V ₃ as in FIG. 1 are applied between and the exit surface, respectively.

The operation of the detector of this embodiment is the same as that of the detector of FIG.

In addition, in the detector of this embodiment as well, as in the case of FIG. A collector for collecting electrons can also be inserted between the outlet of the plate 32 and the scintillator 22. Signals from each collector are led to a preamplifier via wiring 34, 36. The flow of the detection signal through the photomultiplier tube 30, the flow of the detection signal through the wiring 34, or the flow of the detection signal through the wiring 36 can be selected.

In the above embodiment, the multichannel plate 32 and the scintillator 22 are integrally assembled with the secondary electron multiplier 31 or the channeltron 40 as a multiplier. Only the channel tron 40 and the multichannel plate 32 may be integrated. Furthermore, a secondary electron multiplier 31 or a channel tron 4
The multichannel plate 32, the scintillator 22, and the photomultiplier tube 30 may be integrally assembled in the photomultiplier tube 30.

(Effect of the invention) In the detector of the invention, a secondary electron multiplier, a multichannel plate, a scintillator, and an electron multiplier are combined in this order, and between the secondary electron multiplier and the multichannel plate, Collectors that collect electrons are removably inserted between the multichannel plate and the scintillator, and the output of the collectors or the output of the photomultiplier tube can be selected, so that the signal can be changed from a strong signal to a weak signal. Detection can be performed over a wide dynamic range. When detecting the weakest signal, the incident charged particles are converted into electrons, amplified by a multiplier and a multichannel plate, converted into light by a scintillator, and then further amplified by a photomultiplier tube. This makes it possible to detect extremely weak charged particles.

Additionally, in addition to the voltage applied to the multiplier and the photomultiplier tube, the voltage applied between the inlet and outlet surfaces of the multichannel plate can also be adjusted to obtain the optimum sensitivity. becomes easier.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention;
FIG. 2 is a schematic sectional view showing another embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view showing the detector developed by the present inventors. 22...scintillator, 30...photomultiplier tube, 31...secondary electron multiplier tube, 32...multichannel plate, 40...channeltron.

Claims (1)

[Scope of utility model registration request] A multichannel plate is provided close to the final stage dynode or the exit of the multiplier that converts incident particles into secondary electrons and amplifies them, and a scintillator that converts electrons into light is provided at the exit of this multichannel plate. A photomultiplier tube is provided at a position that receives light from the scintillator, and a first collector that collects electrons is removably inserted between the multiplier and the multichannel plate. A second collector that collects electrons is removably inserted between the scintillators, and one of the output of the first collector, the output of the second collector, and the output of the photomultiplier tube can be selected. A detector for charged particles, etc., characterized in that: