JP2009187771A - Merging/separation mechanism of charged particles and neutral particles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of maintaining transmission efficiency of charged particles to a certain extent even in the case there are collisions between charged particles and gas. <P>SOLUTION: This is a merging and separation mechanism of charged particles and neutral particles having: four electrode rods which are arranged along an optical axis having a bent portion bent in a certain plane and at equal spacings from the optical axis so as to surround the optical axis at angular intervals of 90°, and of which the position of both end parts are aligned while maintaining mutually parallel relations; and an entrance electrode and an exit electrode which are arranged to interpose the four electrode rods so as to cross at right angles the optical axis and each have a first aperture at a position to cross the optical axis and a second aperture at a position to cross the extension line of an orbit going straight from the bent portion of the optical line without bending. The electrode rods are arranged at the angular positions of obliquely 45° from the optical axis against the plane including the bent optical axis and the charged particles and/or neutral particles enter from the aperture of the entrance electrode and are emitted from the aperture of the exit electrode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a merging or separating mechanism for charged particles and neutral particles, which is effective for use in a mass spectrometer.

  As a mechanism for separating charged particles and neutral particles, there is a conventional case (Patent Document 1) of a structure in which a deflecting electrode of an electrostatic field placed in a space evacuated to vacuum is used. The structure is shown in FIG.

  In this example, when the charged particles and neutral particles are separated from the particle beam entering from the entrance 20 and only the charged particles are taken out from the exit 29, the shielding plate 28 is blocked by the central axis / neutral particle trajectory O. It is only necessary to block the flight of neutral particles while being inserted into the position and apply the same voltage to the four deflection electrodes 21 to 24 to form an electric field that can draw the trajectory I of the charged particles.

  On the other hand, when only the neutral particles are taken out from the outlet 29, the four shielding electrodes 21 to 24 are charged with the previous shielding plate 28 moved to a position removed from the central axis / neutral particle trajectory O. What is necessary is just to apply the voltage of the electric field formation conditions which cannot draw the orbit I of a particle.

Japanese Patent No. 3497367 JP 2000-243347 A

  There may be demands such as taking out only one particle from a particle beam containing both charged particles and neutral particles, or removing them, or separating them separately, and so on. Is the object of the present invention.

  In the structure shown in FIG. 1 of the conventional example, if there is a collision between residual gas in the space of the particle or an intentionally introduced gas and the particle in the space, the kinetic energy of the particle is lost. In addition, the charged particles having various kinetic energies lose their balance with the forces received from the deflection electrodes 21 to 24 on the orbit, and therefore, the particles other than those that have not collided cannot draw the orbit toward the outlet 29. .

  Even if the voltage applied to the deflection electrode is set in various combinations, the field formed by it will be a condition where charged particles with a limited kinetic energy that can balance the force received from it can pass. As a result, the transmittance of charged particles is reduced as a result.

  By the way, as a method of deflecting the traveling axis of charged particles, Patent Document 2 describes an example in which a quadrupole electrode rod to which a high-frequency voltage is applied is bent. However, in this case, even if the trajectory of the ions can be deflected, the neutral particles that go straight will diverge against the electrode rod because the bent electrode rod blocks the axis of travel, and the neutral particles are lost. As a result, it can no longer be extracted as a neutral particle beam.

  In view of the above points, an object of the present invention is to provide a method for maintaining the transmission efficiency of charged particles to some extent even when collisions between charged particles and gas have to be taken into consideration, compared to neutral particles. It is to provide.

In order to achieve this object, the merging or separating mechanism of charged particles and neutral particles according to the present invention is:
Along the optical axis having a bent portion bent in a certain plane and at equal intervals from the optical axis so as to surround the optical axis at 90 ° intervals, the positions of both ends are maintained while maintaining the mutual parallel relationship. 4 aligned electrode bars,
The four electrode rods are arranged so as to be orthogonal to the optical axis, and intersect with the first opening at the portion that intersects the optical axis and the extended line of the trajectory straightly advanced without bending the bent portion of the optical axis. A charged particle and neutral particle merging or separating mechanism comprising an inlet electrode or an outlet electrode having a second opening in position,
The electrode rod is disposed at a position inclined at an angle of 45 ° from the optical axis with respect to the plane including the bent optical axis, and charged particles and / or neutral particles are incident from the opening of the entrance electrode, It is configured to emit from the opening of the exit electrode,
By applying a predetermined high-frequency voltage, a DC voltage for mass filter function, and a DC voltage for setting an axial potential to the electrode bar, and a predetermined DC voltage for forming an axial electric field to the outlet electrode and the inlet electrode, The neutral particles are made to travel along the shape of the bent portion of the electrode rod, and the charged particles and the neutral particles are joined or separated by moving the bent portion of the electrode rod straight.

  In addition, the four electrode rods are characterized in that the high frequency voltage and the mass filter function DC voltage are superimposed and applied so as to have opposite polarities between adjacent electrodes.

  Further, the axial potential setting DC voltage is characterized in that voltages having the same polarity are applied to all electrodes.

  Further, the DC voltage for forming an axial electric field is positive in the transport direction of charged particles when transporting and storing positive charged particles, and is negative in the transport direction of charged particles when transporting and storing negative charged particles. It is characterized in that a voltage having a polarity that generates an electric field gradient is applied.

  In addition, a gas having a predetermined pressure can be introduced into a space region surrounded by the four electrode rods.

According to the merged or separated mechanism of charged particles and neutral particles of the present invention,
Along the optical axis having a bent portion bent in a certain plane and at equal intervals from the optical axis so as to surround the optical axis at 90 ° intervals, the positions of both ends are maintained while maintaining the mutual parallel relationship. 4 aligned electrode bars,
The four electrode rods are arranged so as to be orthogonal to the optical axis, and intersect with the first opening at the portion that intersects the optical axis and the extended line of the trajectory straightly advanced without bending the bent portion of the optical axis. A charged particle and neutral particle merging or separating mechanism comprising an inlet electrode or an outlet electrode having a second opening in position,
The electrode rod is disposed at a position inclined at an angle of 45 ° from the optical axis with respect to the plane including the bent optical axis, and charged particles and / or neutral particles are incident from the opening of the entrance electrode, It is configured to emit from the opening of the exit electrode,
By applying a predetermined high-frequency voltage, a DC voltage for mass filter function, and a DC voltage for setting an axial potential to the electrode bar, and a predetermined DC voltage for forming an axial electric field to the outlet electrode and the inlet electrode, Since the neutral particles are allowed to travel along the shape of the bent portion of the electrode rod, and the neutral particles move straight along the bent portion of the electrode rod, the charged particles and the neutral particles are joined or separated.
Even when collisions between charged particles and gas have to be taken into account, it has become possible to provide a method for maintaining a certain degree of transmission efficiency of charged particles, whose passage conditions are stricter than those of neutral particles.

  Embodiments of the present invention will be described below with reference to the drawings.

[Example 1]
FIG. 2 shows an embodiment of a separation mechanism for charged particles and neutral particles according to the present invention. In FIG. 2, the basic structure is divided into five drawings: a front view, a plan view, a right side view, a three-dimensional view, a quadrupole section, and a wiring diagram.

  The basic structure is such that a portion shown as a quadrupole 2 is sandwiched between the entrance electrode 1 and the exit electrode 3. The quadrupole 2 is arranged at equal intervals along the central axis (also referred to as an optical axis) having a bent portion bent in a certain plane and surrounding the central axis at 90 ° intervals. These four electrode rods are aligned at both ends while maintaining the parallel relationship. Further, at least the surfaces of these electrodes are conductive, and voltage, current, etc. are supplied to them. However, the power supply for that is omitted.

  Furthermore, these are usually stored and installed in a vacuum vessel, and there may be a case where an arbitrary gas component is supplied to this space with its kind and amount controlled. In addition, although not illustrated in the figure, a control system and a unit such as a sequencer and a computer for controlling each voltage supplied to the constituent electrodes and its set value control, and a vacuum exhaust device and the like are provided. ing.

  The entrance electrode 1 and the exit electrode 3 have an opening on an extension line of the central axis 6. In this example, the outlet electrode 3 has a charged particle outlet 4 provided on a downstream extension line that is bent and stretched at the bent portion of the central axis, and straightly extends without bending the bent portion of the central axis. A neutral particle outlet 5 provided on the downstream extension line of the track is provided as a particle outlet. The entrance electrode 1 is also opened in the same manner, but is omitted. In addition, the entrance electrode 1 and the exit electrode 3 are arrange | positioned so that it may orthogonally cross with a central axis.

  In this case, the quadrupole 2 is a round bar electrode (also called a pole), and as shown in the figure, once bent upward on the two-dot chain line in the middle A and on the two-dot chain line in B. This time it is bent back downward. The bending angle can be increased when the kinetic energy of the charged particles is low, but conversely, the angle becomes small when the kinetic energy is high.

  As a set of four round bar electrodes having such a shape, 45 ° obliquely from the optical axis (± 1 °, allowable value is medium with respect to a plane including the optical axis bent from the entrance electrode 1 toward the exit electrode 3 It depends on the diameter and angle of the spread of the active particle beam (the best is 45 °). This positional relationship can be confirmed by a “quadrupole section and wiring diagram” showing a section cut by a plane perpendicular to the central axis 6. The arrangement can also be confirmed by a “three-dimensional view”. The four electrode rods are aligned at both ends.

The quadrupole 2 is applied with high-frequency and direct-current voltages as in the example shown in the “quadrupole section and wiring diagram”. Symbols in the expression are V ₀ : high frequency amplitude voltage value, ω: angular frequency, t: time, θ: phase, U ₁ : DC voltage value (for mass filter function), U2: DC voltage value (axis potential) That is, for offset potential setting).

  In this case, the configuration of the front stage of the entrance electrode 1 and the rear stage of the exit electrode 3 is omitted. However, in actuality, the source of the incident particle beam, the selection of the emitted charged particles and neutral particles, or the detection and use thereof are used. The parts to be connected are configured.

FIG. 3 shows a simulation example when charged particles and neutral particles are incident on the configuration illustrated in FIG. In the case of positively charged particles at the entrance electrode 1 and the exit electrode 3, both DC voltages U ₃ and U ₄ applied to the entrance electrode 1 and the exit electrode 3 have a magnitude relationship of U ₃ > U ₄ , respectively. If negative charged particles are targeted, both DC voltages U ₃ and U ₄ applied to the entrance electrode 1 and the exit electrode 3 are applied in a magnitude relationship of U ₃ <U ₄ , respectively. This is because the charged particles can move from the upstream side to the downstream side of the quadrupole 2 by the electric field gradient formed by the DC voltages U ₃ and U ₄ .

The four electrodes of the quadrupole 2 include V ₀ · cos (ωt + θ) + U ₁ + U ₂ in one set of opposing electrodes, and V ₀ · cos (ωt + θ) −U _{1 in the other set.} A voltage of + U ₂ is applied. Note that the value of U ₁ is set low because the optical axis is bent. This reduces the mass resolution but improves the transmittance. If the mass of the charged particle is not specified, U ₁ is normally zero.

  Under this condition, a particle beam in which charged particles and neutral particles that are incident from the opening of the entrance electrode 1 on the central axis 6 are mixed is exited at an angle at which the neutral particles that are not affected by the electric field are incident. Whereas the particles move straight toward the electrode 3 side, the charged particles are influenced by the AC electric field formed by the quadrupole 2 and proceed to the exit electrode 3 side while vibrating in the radial direction.

  Since the quadrupole 2 is formed in a shape having a bent portion at the position A and the position B, the charged particles that have traveled in the vicinity of this position are bent along the orbit along the bending direction. Go. In this case, only the trajectory of the charged particle is changed so that the traveling axes of the charged particle and the neutral particle are parallel to each other.

  As shown by the charged particle trajectory 7, the charged particle travels through the charged particle outlet 4 of the opening provided in the outlet electrode 3 with a certain width while vibrating in the radial direction. As in the neutral particle trajectory 8, the beam travels straight with a spread depending on the initial width and angle at the time of incidence, and only the beam within the range of the hole diameter of the neutral particle outlet 5 passes through the neutral particle outlet 5. Other than that, it strikes the exit electrode 3 and the progress is blocked. This state is depicted in a front view and a right side view in such a way that the beam trajectory passes through the electrode rod, the electrode plate, and the like.

  The above is the operation under the condition that there is no collision with the gas component particles, but in the case of FIG. 4, when the particle mean free path is shorter than the size of the structure and there is particle collision (the presence of helium gas) The following is a simulation of the situation for an example in which the mean free path is 3 mm. However, since it only considers the decrease in kinetic energy due to collision, it does not fully reflect the actual situation, but at least the charged particle trajectory is maintained, the radial amplitude is small, and the beam diameter is narrowed Is confirmed.

[Example 2]
The bending in the middle of the quadrupole portion shown in the first embodiment may not be a straight polygonal line but may be a bending with a smooth S-shaped curve. Furthermore, when the traveling direction of the charged particles is not made parallel as in the first embodiment but is emitted at a different angle, the bending angle may be different every two bendings. It does not have to be returned in the form.

  Further, a bending structure having a shape of drawing an arc may be used, and an example of such a case is shown in FIG. The bent portion of the quadrupole 2 is bent in an arcuate shape, and as a result, the charged particle outlet 4 is located on the downstream extension line in the curved direction of the electrode rod and in the middle as seen in the right side view. The active particle outlet 5 is disposed on the downstream extension line of the trajectory that has straightly traveled without curving the curved portion of the electrode rod.

  In the trigonometric illustration, the portion whose shape is difficult to grasp is shown as a whole by a three-dimensional view and a three-dimensional cut-out sectional view. The arrangement of the electrode rods is the same as that in Example 1 under the condition that the position is 45 ° (± 1 °) obliquely in this example. The voltage supply to each part of the electrode is the same as in the first embodiment.

  The operation is almost the same as in the first embodiment. The trajectory of the charged particles follows the bending direction of the quadrupole 2, but the neutral particle beam takes a trajectory that maintains the direction at the time of incidence. FIG. 6 shows an example in which the trajectories of charged particles and neutral particles are simulated under high vacuum. The particle trajectories are shown in perspective.

  As a three-dimensional drawing, a “three-dimensional 1/4 cut-out cross-sectional view” and a “three-dimensional vertical cross-sectional view” further show how orbits are separated. Further, the “vertical sectional view” shows a charged particle trajectory 7 passing through the vicinity of the center of the inscribed circle of the quadrupole 2 and a neutral particle trajectory 8 passing through the gap between the two lower electrode bars.

  When the extension of the orbit of the neutral particles is large, the portion facing the neutral particle orbit 8 on the inscribed circle side of the electrode rod can be scraped off. An example of this is shown in “Vertical sectional view during neutral particle passage enlargement processing” in FIG. 6, and there was almost no influence on the trajectory of the charged particle beam by machining the inside of the electrode rod.

  FIG. 7 shows a simulation example in which gas is introduced into this space to lower the degree of vacuum and the collision with gas particles is taken into consideration. However, although it is the same as that of Example 1, only the loss of the kinetic energy due to collision with the gas particle is taken into account for both the charged particle and the neutral particle. Changes in flight direction due to collisions with gas particles are not taken into account for simplicity.

  However, even if it is a simple calculation, when a charged particle decreases its kinetic energy, it can confirm the average behavior that its flight trajectory is deflected along the bent direction of the quadrupole 2. .

  When there is a collision with a gas particle, a phenomenon called “cold cooling” causes the vibration width of the charged particle to become narrower and the thickness of the charged particle beam to change. Can be confirmed. In particular, if the right side views of the respective figures are compared, it can be more clearly discriminated at the orbital portion in flight in the quadrupole space.

[Example 3]
In the example shown in FIG. 8, the relationship between the inlet and the outlet is reversed in the structure of the second embodiment. In other words, the bent electrode rod of the quadrupole 2 is arranged on the entrance side of the charged particle beam. Accordingly, as shown in the left side view, the charged particle inlet 9 is on the upstream extension line in the bending direction of the electrode rod, and the neutral particle inlet 10 is straight without bending the curved portion of the electrode rod. It is placed on the upstream extension of the track that was retroactively extended. The arrangement of the electrode rods constituting the quadrupole 2 is the same as that in the first embodiment under the condition that the position of the diagonal 45 ° (± 1 °) is set also in this example.

  Portions that are unclear in the plan view are shown in a three-dimensional view and a three-quarter cut-out sectional view. The voltage supply is the same as in Example 1, but the applied DC voltage is such that an electric field gradient is generated in a direction in which charged particles are accelerated from upstream to downstream, that is, from the left to the right in the example of FIG. Is set so that a potential gradient is generated. This is set so that the potential of the outlet electrode 3 is lower than that of the inlet electrode 1. This relationship is when the polarity of the charged particles is positive, and is opposite when the polarity of the charged particles is negative.

  However, if the kinetic energy of the incident particles is relatively high, or if the mean free path of the space where the quadrupole 2 is placed is not short, the collision probability is small, so there is no need to provide a potential gradient. In some cases. A high-frequency voltage and a direct-current voltage are applied to the quadrupole 2 as in the first embodiment.

  FIG. 9 shows the operation in this case by particle beam trajectory simulation. The charged particle beam is incident separately from the charged particle inlet 9 and the neutral particle beam is incident separately from the neutral particle inlet 10, and merges in the vicinity of the bending of the quadrupole 2. In this orbit from the vicinity to the exit, an opportunity for collision between charged particles and neutral particles is created.

  These particles proceed to the charged / neutral particle outlet 11, which is a common exit, while receiving the interaction. Usually, a monitor, an analyzer, a particle receiving device, etc. are placed and used after this. The interaction in this case assumes a physical / chemical reaction, but observes and uses the result of the difference between charged particles and neutral particles.

  This example does not show an example of a simulation considering the collision by lowering the degree of vacuum, but the trajectory is almost the same as that of the second embodiment. However, the incident of charged particles is from the bent portion of the quadrupole 2, and the details are slightly different because the linear portion of the quadrupole 2 is located in the exit direction. In Example 4 to be described later, a case of a collision is also shown, so that the situation can be referred to.

[Example 4]
FIG. 10 shows an example of merging / separating a charged particle beam and a neutral particle beam. It is an example of the structure which combined the beam trajectory separation of Example 2 raised previously and the beam trajectory merge of Example 3. FIG. The pair of bent quadrupoles 2 face each other across the intermediate electrode 12 on the straight portion side, and the bent portion side is arranged in the direction in which the beam enters and exits. Is a joint that matches.

  Note that the intermediate electrode 12 here is not necessarily required if there is no difference in the degree of vacuum between the spaces of the respective quadrupoles 2.

  The entrance electrode 1, the intermediate electrode 12, and the exit electrode 3 are preceded by a direct current voltage for forming a potential gradient in the quadrupole space, and the quadrupole 2 is preceded by a high frequency and direct current voltage for guiding charged particles. Similarly, the arrangement of the electrode rods constituting the quadrupole 2 is inclined at 45 ° (± 1 °) as in the previous example.

  FIG. 11 shows a simulation of the state of merging and separation of both charged and neutral particles. The first half where charged particles and neutral particles are incident and the two beams merge is the same as in the third embodiment. It can be said that the operation in the second half where the mixed beam of charged particles and neutral particles is separated is the same as that of the second embodiment.

  The charged particle trajectory 7 has a large radial amplitude in the vicinity of the intermediate electrode 12, but is because the electrode voltage is not sufficiently optimized. The average trajectory axis of the charged particle is a quadrupole. It can be seen that it is bent along the axis 2 or goes straight. On the other hand, since the neutral particle beam is not deflected by the electric field, it travels as a beam having a predetermined spread determined by the initial angle, position and kinetic energy at the time of incidence. Anything that collides will be more expansive.

  FIG. 12 shows a simulation that considers collisions with gas particles under conditions where the degree of vacuum is lowered by introducing gas or reducing the displacement of the vacuum pump. However, trajectory changes due to neutral particle collisions are not taken into account.

[Example 5]
As a modification of the first embodiment, when neutral particles are not used after the orbital separation, the neutral particle outlet 5 portion is previously blocked by a slanting reflecting deflection plate and taken out from the neutral particle outlet 5. Alternatively, the neutral particle beam may be reflected and deflected so as not to reach the subsequent stage.

[Example 6]
As a modification of the first embodiment, a quadrupole 2 for separating a charged particle beam and a neutral particle beam is arranged in a pre-pole disposed in a front stage of a mass filter of a normal quadrupole mass spectrometer, or in a rear stage. Used as a post pole.

  In this configuration, since the operation is performed to eliminate the neutral particle beam, the neutral particle take-out port is not provided. The DC voltage applied to the quadrupole in this part forms an axial potential with the same polarity and value for the four poles.

  By deflecting only the charged particle trajectory in this way and eliminating the neutral particle beam, detector noise can be reduced. Further, in this method, since the quadrupoles are arranged at an angle of 45 °, the neutral particle beam does not fly in the gap between the electrode rods and collide with the electrode rods to contaminate the rod surface.

  Can be widely used for research on charged particles and neutral particles.

It is a figure which shows an example of the separation mechanism of the conventional charged particle and neutral particle. It is a figure which shows one Example of the separation mechanism of the charged particle and neutral particle concerning this invention. It is a figure which shows one Example of the simulation by the separation mechanism of the charged particle and neutral particle concerning this invention. It is a figure which shows another Example of the simulation by the separation mechanism of the charged particle and neutral particle concerning this invention. It is a figure which shows another Example of the separation mechanism of the charged particle and neutral particle concerning this invention. It is a figure which shows another Example of the simulation by the separation mechanism of the charged particle and neutral particle concerning this invention. It is a figure which shows another Example of the simulation by the separation mechanism of the charged particle and neutral particle concerning this invention. It is a figure which shows one Example of the confluence | merging mechanism of the charged particle and neutral particle concerning this invention. It is a figure which shows one Example of the simulation by the joining mechanism of the charged particle and neutral particle concerning this invention. It is a figure which shows one Example of the joining / separation mechanism of the charged particle and neutral particle concerning this invention. It is a figure which shows one Example of the simulation by the joining / separation mechanism of the charged particle and neutral particle concerning this invention. It is a figure which shows another Example of the simulation by the joining / separation mechanism of the charged particle and neutral particle concerning this invention.

Explanation of symbols

1: entrance electrode, 2: quadrupole, 3: exit electrode, 4: charged particle exit, 5: neutral particle exit, 6: central axis (optical axis), 7: charged particle trajectory, 8: neutral particle trajectory 9: charged particle inlet, 10: neutral particle inlet, 11: charged / neutral particle outlet, 12: intermediate electrode, 20: incident port, 21: deflection electrode, 22: deflection electrode, 23: deflection electrode, 24: Deflection electrode, 25: body, 26: body, 27: separator, 28: stopper, 29: exit port, I: ion trajectory, O: central optical axis

Claims (5)

Along the optical axis having a bent portion bent in a certain plane and at equal intervals from the optical axis so as to surround the optical axis at 90 ° intervals, the positions of both ends are maintained while maintaining the mutual parallel relationship. 4 aligned electrode bars,
The four electrode rods are arranged so as to be orthogonal to the optical axis, and intersect with the first opening at the portion that intersects the optical axis and the extended line of the trajectory straightly advanced without bending the bent portion of the optical axis. A charged particle and neutral particle merging or separating mechanism comprising an inlet electrode or an outlet electrode having a second opening in position,
The electrode rod is disposed at a position inclined at an angle of 45 ° from the optical axis with respect to the plane including the bent optical axis, and charged particles and / or neutral particles are incident from the opening of the entrance electrode, It is configured to emit from the opening of the exit electrode,
By applying a predetermined high-frequency voltage, a DC voltage for mass filter function, and a DC voltage for setting an axial potential to the electrode bar, and a predetermined DC voltage for forming an axial electric field to the outlet electrode and the inlet electrode, Charging characterized in that it proceeds along the shape of the bent portion of the electrode rod, and the neutral particles move straightly along the bent portion of the electrode rod so that the charged particles and neutral particles merge or separate. Mechanism of merging or separating particles and neutral particles. 2. The charged particle according to claim 1, wherein the high frequency voltage and the mass filter function DC voltage are applied to the four electrode rods so as to have opposite polarities between adjacent electrodes. Mechanism of merging or separating neutral particles. 2. The mechanism for merging or separating charged particles and neutral particles according to claim 1, wherein the axial potential setting DC voltage is applied with voltages having the same polarity in all electrodes. The DC voltage for forming an axial electric field is a negative electric field gradient in the transport direction of charged particles when transporting and storing positive charged particles, and a positive electric field in the transport direction of charged particles when transporting and storing negative charged particles. 2. A mechanism for merging or separating charged particles and neutral particles according to claim 1, wherein a voltage having a polarity that causes a gradient is applied. The charged particle / neutral particle merging or separating mechanism according to claim 1, wherein a gas having a predetermined pressure can be introduced into a space region surrounded by the four electrode rods.

Images