JP2511670B2 - Magnetic shield - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetically shielded probe. Specifically, the present invention is a probe using the motion of electrons or ions, such as an ionization vacuum gauge, a phototube, an electron multiplier, and a quadrupole mass spectrometer, in the presence of an external magnetic field such as a fusion device. A magnetically shielded stylus for use in a location.

(Prior Art) A case will be described in which the probe utilizing the motion of electrons or ions is an ionization vacuum gauge. The conventional one is shown in FIG.

In FIG. 1, in order to measure the degree of vacuum inside the vacuum vessel wall 1, an ionization vacuum gauge probe 2 is attached to the measurement port 3. An ionization vacuum gauge probe 2, an electrode 4 such as a filament, a grid, and a collector, a current introduction terminal 5 for electrode attachment, and a current introduction terminal support substrate 7 that supports the current introduction terminal 5 via an electrical insulator 6 such as ceramic. .

A magnetic shield cover 8 is placed outside the ionization vacuum gauge probe 2 and the measurement port 3. The reason why the magnetic shield cover 8 is placed is as follows.

Since the measurement port 3 and the current introduction terminal support substrate 7 have a portion in contact with the vacuum portion, stainless steel that emits a small amount of gas is used. Without the magnetic shield cover 8, stainless steel is a non-magnetic material, so that when an external magnetic field is applied, the magnetic field is also applied to the electrode 4 portion. This magnetic field changes the trajectories of electrons and ions in the vicinity of the electrode 4, so that the sensitivity of the ionization vacuum gauge probe 2 changes. If the magnetic shield cover 8 made of a magnetic material such as electromagnetic soft iron magnetically shields, even if an external magnetic field is applied, the magnetic field in the vicinity of the electrode 4 is small, and the trajectories of electrons and ions are almost unchanged from before the magnetic field was applied. And the sensitivity is not compromised.

(Problems to be Solved by the Invention) However, since the cord is connected to the current introducing terminal 5, the magnetic shield cover 8 needs the hole 9 for connecting the cord. In order to obtain a sufficient shield coefficient, the hole 9 for connecting the cord must be made as small as possible.
Therefore, the current introduction terminal 5 is passed through the hole 9 for connecting the cord.
The task of connecting the cords with the is not easy. Even when the ionization vacuum gauge probe 2 is damaged and needs to be replaced, the entire magnetic shield cover 8 must be removed.

The outer diameter of the magnetic shield cover 8 is larger than the outer diameter of the current conducting terminal supporting board 7. For this reason, the space to be magnetically shielded becomes large, and therefore the magnetic shield cover 8
Not only becomes larger, but its thickness also becomes thicker.

(Means for Solving Problems) The present invention has been invented in order to eliminate the above problems, in which a magnetic shield material such as electromagnetic soft iron is used for the current introduction terminal support substrate 7, and the magnetic shield cover 8 is used. Is arranged around the measurement port 3 and the current introduction terminal support substrate 7 and the magnetic shield cover 8 are connected.

(Operation) According to the present invention ,. The current introducing terminal support substrate 7 also becomes a part of the magnetic shield, and it is not necessary to place the magnetic shield cover 8 on the outside of the current introducing terminal support substrate 7, so that not only the cord connection work and the probe replacement work become easy, but also the magnetic shield The size of the shield can also be reduced.

(Example) A specific example of the present invention will be described with reference to FIG.

The current introduction terminal support substrate 7 is made of a magnetic shield material such as electromagnetic soft iron. The measurement port 3 is made of stainless steel as in the conventional case, but the magnetic shield cover 8 is welded around the measurement port 3 or fixed with bolts (the case of welding is shown in the figure) to introduce the current. The terminal support substrate 7 and the magnetic shield cover 8 are connected with bolts 11. Even if an external magnetic field is applied, since the current introducing terminal support substrate 7 and the magnetic shield cover 8 are magnetic shield materials, the magnetic field is small in the vicinity of the electrode 4, and the trajectories of electrons and ions hardly change from those before application of the magnetic field. , Sensitivity does not change.

In this embodiment, it is not necessary to provide the magnetic shield cover 8 on the outside of the current introducing terminal support substrate 7, and the current introducing terminal 5 and the cord are connected through the cord connecting hole 9 as in the conventional example. There is no need, and connection work becomes very easy.

Even when the ionization vacuum gauge probe 2 is damaged and needs to be replaced, the current introduction terminal support substrate 7 can be replaced by removing it from the measurement port 3 and the magnetic shield cover 8, and the ionization vacuum gauge probe 2 can be replaced as in the conventional example. It is not necessary to remove the entire magnetic shield cover 8 outside the vacuum gauge probe 2, and replacement work is facilitated.

In this embodiment, the outer diameter of the magnetic shield cover 8 can be equal to or less than the outer diameter of the current introduction terminal supporting board 7. The outer diameter of the magnetic shield cover 8 can be smaller than that of the conventional example in which the outer diameter of the current introduction terminal supporting substrate 7 is always larger. In addition, the released gas can be sufficiently reduced by subjecting the portion of the current introducing terminal support substrate 7 that is in contact with the vacuum portion to a surface treatment such as plating.

 Another specific example will be described with reference to FIG.

The magnetic shield cover 8 is rotatable around the measurement port 3, and the magnetic shield cover 8 and the current introduction terminal supporting board 7 are connected by bolts with the measurement port collar 13 sandwiched therebetween. Introduction terminal support substrate 7
A vacuum sealing material 10 such as a rubber O-ring is inserted between them.

In the embodiment of FIG. 2, it was necessary to connect the measurement port 3 and the magnetic shield cover 8 by welding or bolts, but in this embodiment, it is not necessary to connect the measurement port 3 and the magnetic shield cover 8. No, magnetic shield cover 8
And the current introduction terminal support substrate 7 are connected with a bolt, the ionization vacuum gauge probe 2 and the magnetic shield cover 8 are supported by the measurement port 3, and the vacuum sealing material 10 is also the measurement port collar 1 and the current introduction terminal support substrate. Since it is sandwiched between 7, it is easy to assemble the magnetically shielded probe head.

If the required magnetic shield coefficient cannot be obtained with only one magnetic shield layer, a large magnetic shield can be obtained by inserting the magnetic shield inner layer 14 between the measurement port 3 and the magnetic shield cover 8 as shown in FIG. The coefficient can be obtained.

In the above examples, the case where the probe is an ionization vacuum gauge is described, but the photo shield, the electron multiplier, the electron such as the quadrupole mass spectrometer, or the magnetic shield probe that uses the motion of ions. Is also the same.

(Effects of the Invention) As described above, when the magnetically shielded probe of the present invention is used in a space with a magnetic field such as a nuclear fusion device, cord connection work and probe exchange work are In addition to being easy, the size of the magnetic shield can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view of a conventional magnetically shielded ionization vacuum gauge probe. 2 to 4 are all explanatory views of an embodiment of the present invention. In the figure, 1 ... Vacuum container wall; 2 ... Ionization vacuum gauge probe; 3 ... Measuring port; 4 ... Electrode; 5 ... Current introducing terminal; 6 ... Electrical insulator; 7 ... Current introducing terminal Support substrate; 8 ...... Magnetic shield cover; 9 ...... Cord connection hole; 10 ...... Vacuum seal material; 11 ......
Fixing bolt; 12 ... Welded part; 13 ... Measuring port collar; 14
The inner layer of the magnetic shield. The dotted line shows a non-magnetic material and the shaded area shows a magnetic material.

Claims (4)

(57) [Claims] 1. In a magnetically shielded probe comprising an electrode, a current introducing terminal, a current introducing terminal supporting substrate, a measuring port supporting these, and a magnetic shield cover, the current introducing terminal supporting substrate is composed of a magnetic shield material. The magnetic shield cover is arranged around the measurement port, and the current introduction terminal support substrate and the magnetic shield cover are connected to each other. 2. A magnetic shield cover is rotatable around the measuring port, and the magnetic shield cover and the current introducing terminal support substrate are connected by sandwiching the measuring port collar, and the measuring port collar and the current introducing terminal are supported. The magnetically shielded probe according to claim 1, wherein a vacuum sealing material is inserted between the substrates. 3. The magnetically shielded probe according to claim 1, wherein an inner layer of the magnetic shield is inserted between the magnetic shield cover and the measurement port. 4. The magnetically shielded probe according to claim 1, wherein the probe is an ionization vacuum gauge, a phototube, an electron multiplier, or a quadrupole mass spectrometer.