JP2015220014A - Magnetic field generation device comprising magnetic field variation mechanism for arbitrarily changing magnetic field at magnetic field generation position, and magnetic field adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic field variation mechanism capable of eliminating the need for power and cooling water, of reducing maintenance costs, of resolving troubles caused by power supply and cooling water, of having a simple structure, of being applied to a compound functional magnet and the like with a magnetic field gradient, and of changing a magnetic field drastically and ununiformly.SOLUTION: A magnetic pole 1 is arranged at the center. A permanent magnet 2 is arranged on both sides of the magnetic pole 1. A magnetic body 3 is arranged outside the permanent magnet 2. An external magnetic body plate 10 is arranged on an opposite side to a magnetic field generation position. The external magnetic body plate 10 is attached to an external magnetic body drive shaft 15 provided on an upper surface of the magnetic body 3, and can be moved in a Y-direction. The generated magnetic field is arbitrarily changed by moving the external magnetic body plate 10 without moving the magnetic pole 1.

Description

  The present invention relates to a dipole magnet having a mechanism for greatly and non-uniformly changing a magnetic field, and in particular, has a mechanism for arbitrarily changing a magnetic field generated by a permanent magnet by moving an external magnetic plate. The present invention relates to a magnetic field generator including a dipole magnet.

  Usually, an electromagnet is used for a dipole magnet that requires a large change in magnetic field. In the case of using an electromagnet, a current for generating a magnetic field is required, and in the case of a strong magnetic field, water for cooling a large current is also required. For example, in the case of a large accelerator facility, the annual power consumption by magnets is enormous, and undesirable jitter and drift due to cooling water exist. In addition, the problem of magnetic field stop due to failure of the power supply and the cooling water system is unavoidable, which has a serious influence on the reliability and safety of the equipment.

  There are dipole magnets using permanent magnets, but a technique is used in which the magnetic field is finely adjusted by shims during magnet manufacture and adjustment, or the entire magnet is moved to open and close the gap to change the magnetic field strength and magnetic field distribution. When a permanent magnet is used, the current and cooling water required for an electromagnet are not necessary, but the magnetic field cannot be changed greatly during normal use. The method of opening and closing the gap by moving the entire magnet requires a complicated and expensive structure that resists a strong magnetic field attractive force. In addition, for example, a composite function magnet having a gradient of a dipole magnetic field in the horizontal direction (Combined magnet), or a magnet having an arbitrary magnetic field gradient in the traveling direction (Z direction) of charged particles (Longitudinal gradient bend), etc. When manufacturing a magnet having a magnetic field gradient toward the direction, if the magnetic field is changed by opening and closing the gap as in the prior art (Patent Document 1), the magnetic pole itself moves, so the magnetic field distribution itself changes, It cannot be applied to a magnet having an arbitrary magnetic field gradient as described above. Recently, in the development of new accelerators such as next-generation radiation light sources or particle beam cancer treatment devices, bipolar magnets that guide the traveling direction of charged particles as desired inside them, and various magnets included in them, There has been a need for a magnet having a complicated magnetic field distribution rather than a simple structure as in the past, that is, a structure in which magnetic poles are parallel and a magnetic field is constant. Furthermore, recently, in these apparatuses, power saving is an important required performance.

  The magnetic field adjustment methods that have been proposed so far are aimed at improving the variation of the magnetic field generated during production and obtaining a uniform magnetic field (Patent Documents 1 and 2). A magnetic field adjustment method for changing an arbitrary magnetic field gradient using a magnet having a complicated magnetic field distribution has not been obtained.

Japanese Unexamined Patent Publication No. 5-152120 Japanese Patent Laid-Open No. 10-162998

  The present invention eliminates the need for electric power and cooling water, reduces maintenance costs, eliminates problems caused by power supply and cooling water, has a simple structure, and has a magnetic field gradient including a multi-function magnet. On the other hand, an object is to provide a mechanism for changing to a desired magnetic field.

ADVANTAGE OF THE INVENTION According to this invention, the magnetic field generator which comprises the magnetic field change mechanism of the following aspect in the dipole magnet by a permanent magnet is provided.
[1] A dipole magnet using a permanent magnet is provided with a magnetic field changing mechanism that arbitrarily changes the magnetic field of the magnetic field generation location by changing the position of the pair of external magnetic plates composed of one or more pairs. A magnetic field generator characterized by this.
[2] The magnetic field according to [1], wherein the magnetic field changing mechanism includes the external magnetic plate and an external magnetic plate driving shaft for movably attaching the external magnetic plate. Generator.
[3] The dipole magnet can change the magnetic field distribution arbitrarily in the traveling direction of the charged particles, the dipole magnet with the magnetic poles facing in parallel, the combined function magnet having the gradient of the dipole magnetic field in the horizontal direction, or the charged particle traveling direction. The magnetic field generator according to [1] or [2], which is a magnet (Longitudinal gradient bend) having an arbitrary magnetic pole shape.
[4] Using the magnetic field generation device according to any one of [1] to [3], the external magnetic plate is brought close to or separated from the leakage magnetic field without leaking the magnetic flux path and moving the magnetic pole. And a magnetic field adjustment method, wherein the magnetic field intensity at the magnetic field generation position is arbitrarily changed.

  The magnetic field change mechanism includes a plurality of external magnetic plate driving shafts and a plurality of external magnetic plates that are movably attached to the respective external magnetic plate driving shafts, and are adjacent to each other. And an external magnetic plate that is movably connected to each other.

  According to the present invention, since a permanent magnet is used, no current or cooling water is required, maintenance costs can be reduced, and troubles caused by the power source and cooling water can be eliminated.

  According to the magnetic field adjustment method of the present invention, from the state in which most of the magnetic field flows through the external magnetic plate and does not flow to the magnetic field generation position, to the state in which the majority of the magnetic field flows to the magnetic field generation position without flowing the magnetic field through the external magnetic plate. It is possible to vary the magnetic field arbitrarily over a wide range, significantly and non-uniformly.

  Since the magnetic field adjustment method of the present invention does not move the magnetic pole, it can be applied to a dipole magnet having a magnetic field gradient represented by a composite function magnet.

  Since the magnetic field adjustment method of the present invention uses a leakage magnetic field that is much smaller than the magnetic field between the gaps, the external magnetic plate can be easily driven, and a simple and inexpensive structure can be achieved.

It is a front view which shows the basic composition of the magnetic field generator containing the dipole magnet of this invention. It is explanatory drawing which shows the state which changes the magnetic field in the dipole magnet shown in FIG. 3 is a graph showing a relationship between a moving distance of an external magnetic plate and a magnetic field in the magnetic field change shown in FIG. 2. It is a front view which shows the basic composition in case a magnetic pole is made into a composite function magnet and a magnetic field is changed with a pair of external magnetic material plate. It is a side view which shows the aspect by which the some external magnetic body plate is attached to the some shaft for external magnetic body drive.

Preferred embodiment

  Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings, but the present invention is not limited thereto.

  FIG. 1 shows a basic configuration of a magnetic field generator including a dipole magnet having a magnetic field change mechanism of the present invention. As is well known to those skilled in the art, since the dipole magnet has a line-symmetric structure with the symmetry line as the center, only a half is shown.

  The dipole magnet of FIG. 1 has a magnetic pole 1 at the center, a permanent magnet (PM) 2 on both sides of the magnetic pole 1, a magnetic body 3 as a magnetic flux leakage shield on the outside of the permanent magnet 2, and an external magnetism on the opposite side of the magnetic field generation location. Each body plate 10 is arranged. In FIG. 1, the external magnetic plate 10 is attached to an external magnetic drive shaft 15 (see FIGS. 4 and 5) provided on the upper surface of the magnetic body 3 and is movable in the Y direction in the figure.

  FIG. 4 has the same configuration as FIG. 1 except that a composite functional magnet having a surface inclined in the X direction is used as the magnetic pole 1A.

  As the magnetic pole 1, a magnetic body made of iron, cobalt, nickel, gadolinium, and an alloy (permendule or the like) containing these alone or in combination can be used without limitation. However, in the single magnet, the magnetic body may be composed of a plurality of types or a single type.

  The shape of the magnetic pole 1 is not limited to a shape in which the top surface and the bottom surface are parallel to each other, and may be a magnet (such as a composite function magnet) that is inclined in the X direction or the Z direction in the drawing.

  As the permanent magnet 2, a permanent magnet such as a neodymium magnet, a ferrite magnet, or an alnico magnet can be used without limitation.

  As the magnetic body 3, a magnetic body made of iron, cobalt, nickel, gadolinium, and an alloy (permendur, soft iron, etc.) containing these alone or in combination can be used without limitation.

  The external magnetic material plate 10 can use a magnetic material made of iron, cobalt, nickel, gadolinium, and an alloy (permendur, soft iron, etc.) containing these alone or in combination without limitation. The external magnetic plate 10 may be a single plate (a pair of upper and lower) having a large area, or may have a shape in which a plurality of magnetic plates are arranged as shown in FIG. Although it is desirable that the thickness of the external magnetic material plate 10 be sufficient to change the magnetic field (several centimeters or more), it is not limited to this.

  The external magnetic body driving shaft 15 is not particularly limited as long as it can hold the external magnetic body plate 10 at a predetermined height position. For example, a screw groove may be provided on the outer peripheral surface of the external magnetic body drive shaft 15 to have a function of driving the external magnetic body plate 10 in a desired direction (usually in the vertical direction in FIG. 5).

  The position adjustment of the external magnetic plate 10 is performed by using the rotation of the external magnetic drive shaft 15 as described above, or by using a position adjusting mechanism (not shown) such as a screw mechanism installed separately. Can do. The position adjustment of the external magnetic plate 10 can be performed manually or using a machine such as a motor. Position adjustment can be performed on site or remotely using a remote control device such as GPIB (General Purpose Interface Bus). After the position adjustment, the position of the external magnetic plate 10 is held by fixing the adjustment mechanism or using a fixing device that fixes the external magnetic plate 10 so as not to move.

  FIG. 5 is a side view of a magnetic field generation apparatus including a dipole magnet, and shows a mode in which a plurality of external magnetic body driving shafts 15 are attached to the upper surface of the magnetic body 3. External magnetic plates 10a to 10e are attached to the external magnetic drive shafts 15a to 15e, respectively. The positions of the external magnetic plates 10a to 10e can be changed independently, and the distance from the magnetic body 3 can be gradually increased or decreased in a specific direction. Or by arrange | positioning each external magnetic body plate 10a-10e in a different height position, the distance from the magnetic body 3 can be changed arbitrarily with respect to a specific direction, and arbitrary magnetic field distribution is formed. Can do. In FIG. 5, a magnetic field distribution having a magnetic field gradient in the Z direction is generated by setting the distance inclined in the Z direction (see the lower graph in FIG. 5). In addition, the magnetic body 3 is more effective by dividing the magnetic body 3 with a low relative permeability or by dividing the magnetic body 3 into a plurality of parts and interposing a non-ferromagnetic material such as an air layer between the parts. A magnetic field gradient can be created.

  The magnetic field adjustment method of the present invention will be described with reference to FIG. The magnetic field excited by the permanent magnet (PM) 2 forms a magnetic field at the magnetic field generation location via the magnetic pole 1 and again passes through the magnetic pole (not shown, the magnetic pole in the lower half of the magnet) to function as a return yoke. It returns to the permanent magnet (PM) 2 through the magnetic body 3. The magnetic field flow (magnetic flux) always forms a closed orbit (loop). At this time, the magnetic field can be leaked to the external magnetic material plate 10 side by not providing a shielding body (magnetic material) for confining the magnetic field on the external magnetic material plate 10 side opposite to the magnetic field generation location. Next, by changing the position of the external magnetic material plate 10 by the external magnetic material driving shaft 15, the magnetic field of the magnetic field generation location can be continuously changed over a wide range (FIG. 3). In the present invention, unlike the conventional gap opening / closing method, the magnetic pole is not moved at all.

  An example of the numerical calculation results is shown in FIGS. In this figure, soft iron is used for the magnetic pole 1, the magnetic body 3, and the external magnetic body plate 10, and a neodymium magnet is used for the permanent magnet (PM) 2. The thickness of the magnetic body 3 (vertical height in FIG. 2) is 15 centimeters, and the thickness of the external magnetic body plate 10 is 5 centimeters. “5 cm thickness” in FIG. 3 means the thickness of the external magnetic plate. That is, FIG. 3 shows the change of the magnetic field when the position of the external magnetic plate having a thickness of 5 cm is changed. In FIG. 3, the position of the outer magnetic plate 10 (Outer plate position (y) [mm]) (the vertical position in FIG. 2) is taken as the horizontal axis, and the magnetic field at the location where the magnetic field is generated (Magnetic field By [T]). Is shown on the vertical axis. Since the thickness of the magnetic body 3 is 15 centimeters, the value on the horizontal axis is 15 centimeters when the external magnetic body plate 10 is closest to the magnetic body 3. From FIG. 3, it is clear that the magnetic field at the magnetic field generation point is large and continuously changes in accordance with the change in position of the external magnetic material plate 10.

  A method of changing the magnetic field in the case of the magnetic pole 1A tilted in the X direction shown in FIG. 4 will be described. In this method, the magnetic field can be changed regardless of the shape and inclination of the magnetic pole. Also in the case shown in FIG. 4, the magnetic field at the magnetic field generation location can be changed simply by moving the position of the external magnetic plate 10 up and down. At this time, in the magnetic pole 1A inclined in the X direction, there is a magnetic field gradient at the magnetic field generation location (in FIG. 4, the magnetic field is strong on the left side of the black circle, which is the magnetic field generation location, and the magnetic field is weak on the right side). In the method of the present invention, only the value of the magnetic field can be changed without changing the gradient of the magnetic field at all. In this regard, the conventional magnetic field adjustment method using the gap driving method is greatly different from the fact that when the magnetic field at the position of the black circle is changed, the gradient of the magnetic field (the magnetic field distribution around the black circle) automatically changes.

Claims (4)

In a dipole magnet using a permanent magnet, a magnetic field changing mechanism that arbitrarily changes the magnetic field of the magnetic field generation location by changing the position of one or more pairs of external magnetic plates without moving the magnetic poles. A magnetic field generator characterized by comprising. 2. The magnetic field generation apparatus according to claim 1, wherein the magnetic field changing mechanism includes the external magnetic material plate and an external magnetic material plate driving shaft on which the external magnetic material plate is movably attached. The dipole magnet is a dipole magnet in which the magnetic poles face in parallel, a combined function magnet having a dipole magnetic field gradient in the horizontal direction, or an arbitrary magnetic pole that can arbitrarily change the magnetic field distribution in the traveling direction of the charged particles. The magnetic field generator of Claim 1 or 2 which is a magnet (Longitudinal gradient bend) which has a shape. Using the magnetic field generator according to any one of claims 1 to 3, the magnetic flux path is leaked, and the external magnetic plate is brought close to or separated from the leakage magnetic field without moving the magnetic pole, thereby A magnetic field adjustment method, wherein the magnetic field strength is arbitrarily changed.