JPS6195298A - Pulse magnetic-field generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to an accelerator such as a synchrotron device.
In order to extract the accelerated charged particles, a rectangular pulse am is applied in the sub-microsecond range. The present invention relates to a pulsed magnetic field generating device having a pulsed electromagnet for deflecting charged particles in addition to the charged particles, and particularly relates to a pulsed magnetic field generating device suitable for demagnetizing a residual magnetic field generated in the pulsed electromagnet after passing a pulsed current.

[Conventional technology]

Pulsed electromagnets that use magnetic materials as cores are known in pulsed magnetic field generators. In the above pulsed electromagnet, after applying a pulsed current to form am, it is necessary to return the residual magnetic field to zero in order to operate the pulsed electromagnet under the same conditions at g. For this purpose, conventionally, pulse 1
! It was necessary to use a damped alternating current generating circuit to demagnetize the residual magnetic field of the magnet and a demagnetizing coil wound around the core of the pulsed electromagnet.

Below, conventional pulsed electromagnets and their magnetization and demagnetization will be explained using drawings.

Figure 2 shows a perspective view of a conventional pulsed electromagnet.

In the figure, 11 is a magnetic core, 12m. 12be
and 13av 13b are conductors for passing pulse current, and the pulse current is 12. →1zb and l3-→13
．． It flows in the direction of. Reference numeral 14 denotes a demagnetizing coil through which a current flows to demagnetize the magnetic core 11 . 3 is the magnetic flux density generated in the magnetic pole gap of the magnetic core 11.

FIG. 3 is a block diagram showing an example of a conventional pulsed magnetic field generation circuit including the pulsed electromagnet shown in FIG. There is. 17 is.

Connection cable, 1g is the pulse magnet shown in Figure 2, 19
20 is a control circuit, 21 is a control line, SW1 and SW2 are switches controlled by the control circuit 19, and RLi is a terminating resistor having a resistance value R. Moreover, the above Is, +6.17°+9.
SW1 and SW1 will hereinafter be collectively referred to as drive circuit +00 depending on the case.

Conductor 12 of pulsed electromagnet 18 in FIG. , 13. Characteristic impedance Z expected from charging cable 16°Characteristic impedance Z of cables such as connection cable 17
The configuration is such that a ninth-order relationship is established between e r and the terminal resistance value R8.

Z*=Zc=R* (1)
That is, from the charging cable 16, the switch SW2. Connection 11
] Cable 17. pulse? Impedance matching is achieved up to the r1 magnet 18 and the terminating resistor RL.

In addition, in FIG. 3, the above 16 and sw, , sw, and 1
The shadow W of the wiring for connecting 7, 17, 18, and RL is configured with a negligible distance.

FIG. 4 is a sectional view of the magnetic core 11 shown in FIG. 2, in which the average magnetic path length is Q and the magnetic pole gap length is d.

FIG. 5 shows the external magnetic field H in the magnetic core 11.

It is a so-called BH characteristic diagram showing the relationship with magnetic flux density B.

FIG. 6 is a magnetization characteristic diagram obtained by converting the physical quantities on the vertical and horizontal axes in FIG. 5 in order to calculate the magnetic flux density generated in the magnetic pole gap. The dashed line indicates the initial magnetization curve.

FIG. 7 conceptually shows the waveform of the attenuated alternating current applied to the demagnetizing coil 14 to demagnetize the magnetic core 11, with the vertical axis representing the current value and the horizontal axis representing time.

Next, the operation of the pulse electromagnet 18 shown in FIG. 2 will be explained using FIGS. 2 to 7.

First, the magnetic core l of the pulse electromagnet 18 in FIG.
It is assumed that l is in a demagnetized state. The control circuit 19 turns on the switch SW□, and the DC power supply 15 charges the charging cable 16 with electric charge. After charging, switch SW is turned off. When the output voltage of the DC power supply 15 is V-, charge that generates V- is also accumulated in the charging cable 16.

When a pulsed magnetic field is required, the control circuit 19 turns on the switch SW to discharge the charge stored in the charging cable 16. The current flows through the switch swt, the single connection cable 17, and the conductor 12. .

+2. , terminating resistor @R'E, , conductor 13be 13a
L: Flows.

This fl is a square wave, and the peak current value IP and pulse widths P and J are expressed by the following equation.

L engineer.

P, = 2・□ (3) Here, Ll
, is the length of the charging cable 16, and the V beam.

is the current propagation speed at .

As shown in Figure 2, the coil through which the pulsed current of the pulsed electromagnet flows is connected to the conductors 12°+ 12b+ 13b+ and 1
It is a -turn coil consisting of 3. Generally, the magnetomotive force is determined by the product of the current value and the number of turns of the coil, so the pulse current 1. The magnetomotive force of a coil with - turns is .

ll in the magnetic pole gap! Assuming that field leakage is negligible, in Fig. 4, the average pulse current is given by Q, the path length, and d, the magnetic pole gap length.

The relationship between the external magnetic field H and the magnetic flux density Bp is given by the following equation.

B.

Ip = H, -9+□・d(4) μO Here, μ. is the magnetic permeability in vacuum, and is approximately the same value in air.

Based on the magnetization characteristic diagram in FIG. 6 and the above equation (4).

What are the specific values of the above external magnetic field H1 and magnetic flux density B? You can ask for it.

In FIG. 6, equation (4) is represented by the straight line (a) in the figure. Point A, where the straight line (a) and the initial magnetization curve (for one point (r)) coincide, is the point that indicates the magnetized state.

(hereinafter referred to as the initial magnetization point), coordinates to the initial magnetization point.

That is, 13.・d/μ. The magnetic flux density B at external magnetic field IIJ is determined from Hl·Q.

This initial magnetization point A corresponds to point A' on the initial magnetization curve (dotted chain line) in the B-H characteristic diagram of FIG. That is, a magnetic flux density B and an external magnetic field H8 are generated in the pulse electromagnet 18 during the time of the pulse intensity PIJ.

Next, the residual magnetic flux density B7 of the magnetic pole gap will be explained.

In FIG. 3, the pulsed current passing through the pulsed electromagnet 18 reaches a termination resistor RL having a termination resistance value R1. Since the terminating resistance value R4 has impedance matching as shown in equation (1), the pulse current is not reflected.

After passing the pulse current, I, = O, and the above (4)
The equation therefore becomes straight line (b) in FIG.

On the other hand, since the magnetic core 11 has hysteresis characteristics,
The state of magnetization moves from initial magnetization point A to point C.

When the coercive force is expressed as Hc, the differential magnetic susceptibility μ- is H=±He
Therefore, the magnetization characteristic curve becomes Hc in Fig. 6.
It becomes almost parallel to the vertical axis in the vicinity of 1. The residual magnetic flux density B1 of the magnetic pole gap when =O can be approximated by the following equation.

B, #-・μ. -He (5) Next, demagnetization will be explained. In order to always operate the pulse electromagnet 18 under the same conditions, it is necessary to eliminate the above-mentioned residual magnetic flux. For this reason, conventional devices require the following operations.

The attenuated alternating current generating means 20 is driven by the control line 21 of the control circuit 19 shown in FIG. 3, and the attenuated alternating current I shown in FIG.
flow.

The current value at point 1' in Figure 7 is the straight line (c) in Figure 6.
The value that satisfies the relationship between and the magnetization characteristic curve, that is, -
where =Ip:>It.

Furthermore, the straight line <d) corresponds to the electrical current at point 2' in FIG.

As a result, the magnetization state becomes point 1 in FIG.

Furthermore, in the same manner, E>I,...>
I n-.

〉■1. By applying the f4 flow (7th field) that satisfies the conditions to the degaussing coil 14, the state of magnetization is changed to point l9 point 2. in FIG. ..., that is, point l9 point 2 in Figure 5
Moving from point 1 to point 3, the attenuation alternating current T attenuates and the magnetic core becomes demagnetized.

Regarding the above technology, please refer to the internal report of the High Energy Physics Research Institute.

rFLILL A)'ERTtJFIE KTCKEI
+ ,'IAGNETs FORKEK)'I(OT
ONSYNCHROTRON (in Japanese
e) J, Koji Takada, AMARCH1977.

[Problem that the invention seeks to solve]

As mentioned above, even in the conventional pulsed magnetic field generator,
Although there is a technology to eliminate residual magnetic flux, it requires extra attenuation alternating current generating means, degaussing coils, etc., which makes the structure of the pulsed magnetic field generator complicated and large, and at the same time it is extremely difficult to use. The problem was that it was expensive.

For example, - To give an example, the magnetic flux density is 50o Gauss.

When the characteristic impedance of the cable is about 25 ohms, the excitation 6Ji current is 800 amperes (peak value).

The driving voltage reaches about 40 kilovolts. Therefore.

Naturally, the degaussing current also requires a large current of several hundred amperes, which is commensurate with the degaussing current, so the equipment also becomes larger.

The price reaches over 10 million yen.

The present invention aims to extremely simplify the means for degaussing, simplify the handling and maintenance of the pulsed magnetic field generator, and significantly reduce the price of the pulsed a-field generator.

[Means for solving problems]

The present invention provides a pulsed field generating device comprising a pulsed electromagnet that generates a pulse a@ by passing a pulsed current, and a drive circuit that converts the pulsed current into I[J. The device also includes a terminating resistor having a large resistance value, and further includes a delay cable having a characteristic impedance substantially the same as the characteristic impedance between the pulse electromagnet and the terminating resistor.

[Effect]

By the above-mentioned technical means, the charging cable 16° connection cable 17. Pulsed electromagnet 18. The pulse current transmission path made up of the delay cable and the delay cable is configured such that its negative end is terminated with a resistance value greater than the characteristic impedance, and the other end is terminated with the open end of the charging cable 16.

Since there is impedance mismatch at both ends of the transmission line, the pulse current is repeatedly reflected at both ends of the transmission line due to the action of this transmission line, and an oscillating waveform whose amplitude gradually attenuates mainly due to the loss caused by the terminating resistor. becomes.

In addition, the delay cable obtains a transmission time corresponding to the necessary pulse width between the pulse electromagnet 18 and the terminating resistor, so that the reflected wave at the leading edge of the pulse current from the terminating resistor The waveform of the trailing edge of the pulse current passing through the electromagnet 18 is operated so as not to overlap within the pulse electromagnet 18. A more detailed explanation will be given below using an actual jN example.

〔Example〕

FIG. 8 is a perspective view of a pulsed FFI magnet according to an embodiment of the present invention, and FIG. 1 is a block diagram of an example of a pulsed magnetic field generator using the pulsed electromagnet. 1 One embodiment of the present invention will be described in detail.

In FIG. 1, 22 is a delay cable as pulse current delay means, and RL is a terminating resistor having a resistance value Ro. Other symbols appear in FIGS. 2 and 3.

Here, conductor 12□13. The characteristic impedance looking into the pulse electromagnet 18 is Z, □, conductor +2h, +3
+.

[Pulsed electromagnet] The characteristic impedance considering 8 is 2.2. The characteristic impedance of the cables 16, 17, and 22 is set to ZC, and the cables 16, 17, and 22 are configured to satisfy the following relationship with the terminating resistance value R2 of the terminating resistor RL.

Zm, = Z-n = Zc < Rs (
6) Figure 9 shows the time change of the attenuated pulse current flowing through the pulse electromagnet 18.
The time when 8 is turned on is defined as zero.

τ1. τ! , τ, are each expressed by the following equations.

τ,: The time it takes for the pulse current to propagate through the connection cable 17 (=□) ■ τ,: The L time that the pulse current travels back and forth through the delay cable 22 (=2・□) τ,: The connection cable 17 and charging cable 16 Lts + Ltt (=2・□) However, L□, L2. Andri. are each cable 16
, 17.22 length, V is the propagation velocity of the pulse current.

Moreover, the pulse width P1. So that +＜τ□. Set. The purpose of this is that the incoming and reflected pulsed currents overlap within the pulsed electromagnet 18;

This is to avoid the problem of incomplete demagnetization, and when the leading edge of the pulsed current that has passed through the pulsed electromagnet 18 is reflected by the terminating resistor ORLs and reaches the 18 again, the trailing edge of the same pulsed current is 18 has already passed.

The operation of this embodiment will be explained below. In FIG. 1, the switch SW1 is turned on by a control signal from the control circuit 19, and the charging cable 16 is charged. If the output voltage of the control/circuit 19 is -, then the charging cable 16 also has a voltage V-
The electric charge that occurs is being charged.

After turning off the switch SW1, when a pulsed magnetic field is required, the switch SW! is controlled by the control circuit 19.
Turn on. As a result, a pulse current is applied to the pulse electromagnet 18 via the switch SW and the connection cable 17.

The peak current value IP+pulse width P of the pulse current and the pulse magnetic flux density B generated in the magnetic pole gap are:

Similar to the conventional device, these values are obtained using equations (2), (3), and point A in FIG. 6, respectively. Further, the residual magnetic flux density is also expressed by equation (5).

The pulsed current that has passed through the pulsed electromagnet 18 further passes through the delay cable 22 and reaches the terminating resistor RL.

Since the terminating resistance value R7 is in the relationship shown in equation (6), the pulse current has a peak current value i/, shown in FIG. Electromagnet】Reflected to the 8 side.

I', = r・IP (7) Here, (
From equation 6), o<r<t.

Reflected pulse current 11. generates a magnetic field in the opposite direction when passing through the pulsed electromagnet 18, passes through the connection cable 17, and reaches the charging cable 16. Charging cable 16
Since the terminal end of is open, one reflected pulse current is reflected again, but the peak current value remains unchanged at 1'.

The pulsed current reflected by the charging cable 16 propagates again toward the pulsed electromagnet 1B.

While repeating the above operation, the peak current value of the nine reflected pulse currents approaches zero.

The relationship between the reflected pulse current passing through the pulse electromagnet 18 and time is as shown in FIG. 9, and the peak current value of each pulse current is
The relationship between the incident pulse current and the peak current value 1 is expressed by the following equation.

r',=r''·IP (s) The current waveform in FIG. 9 is an oscillating current similar to the damped alternating current waveform (FIG. 7) in the conventional device.

On the other hand, since the 9 reflection coefficient 11F changes depending on the value of the terminating resistor taR, 1'1 can be changed by R8.

Therefore, by adjusting R8, the magnetization state of the magnetic core 11 can be changed from point 1 to point 2 to point 3 to 9 points on the B-H characteristic as shown in FIG. It can be moved as... As a result, the magnetic core 11 can be demagnetized by the action of one reflected pulse current as in the conventional case.

〔Effect of the invention〕

As explained above, the pulsed electromagnet has the same characteristic impedance as the pulsed current drive circuit.

By arranging a delay cable having approximately the same characteristic impedance as the above characteristic impedance between the termination resistor and further making the termination resistance value larger than the characteristic impedance.

There is an advantage that the residual magnetic flux generated in the magnetic core of the pulsed electromagnet by the incident pulsed current can be automatically demagnetized by utilizing the reflection of the pulsed current.

In addition, a very expensive attenuated alternating current generator, which is required in conventional pulsed magnetic field generators, is required.

Eliminates the need for degaussing coils, etc., and uses delay cables and termination resistors that are extremely inexpensive and easily available on the market.
Since it can achieve exactly the same purpose as the conventional method, it is also economically effective.

There are also significant savings in operating and maintenance costs due to the greatly simplified means for degaussing.

Nine preferred embodiments of the present invention have been described in detail by way of example with reference to the nine drawings. However, the materials, properties, and shapes of the component parts described in this example.

Unless otherwise specified, the relative arrangement, etc., is as follows:
The scope of the present invention is not intended to be limited to these, but are merely illustrative examples.

For example, the characteristic impedances of each cable and pulse electromagnet do not necessarily have to be strictly equal, and it is sufficient that the reflection of the pulse current does not become extremely bad.
The same holds true for the imaginary component of impedance.

Further, regarding the length of the delay cable, although a delay cable having a propagation delay time of half or more of the pulse width of the pulse current is exemplified, the length may be shorter than that if there is no practical problem.

Further, although the case where the pulse electromagnet has one winding has been described, the same effect can be expected even if the pulse electromagnet has a plurality of windings.

Further, although the pulse current waveform has been described in the case of a square wave, the same applies to, for example, a sine wave, a trapezoidal wave, etc.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a perspective view of a conventional pulsed electromagnet, and FIG. 3 is a block diagram of an embodiment of the present invention. A block diagram of a conventional pulsed magnetic field generator, FIG. 4 is a sectional view of the magnetic core, and FIG. 5 is a B-H characteristic diagram of the magnetic core.
Fig. 6 is a magnetization characteristic diagram, and Fig. 7 is a magnetization characteristic diagram. FIG. 8 is a perspective view of an embodiment of a pulsed electromagnet according to the present invention, and FIG. 9 is a diagram of attenuated alternating current waveforms according to an embodiment of the present invention. 11...Magnetic core 12ag 12bv 13a+ 13b...Conducting wire 14
... Demagnetizing coil 15 ... DC power supply 16 ...
・Charging cable 17...Connection cable 18・
...Pulse electromagnet 19...Control circuit 20...
Attenuated alternating current generation circuit 22...Delay cable RL,, RL,...Terminal resistor Z J...Pulse electromagnet input impedance Z1□・
... Pulse electromagnet output impedance ZC ... Cable characteristic impedance B ... Magnetic flux density H.
...External magnetic field A...Initial magnetization point Party...Average magnetic path length d...Magnetic pole gap length P,...Pulse width Patent application filed by Nippon Telegraph and Telephone Public Corporation

Claims (1)

[Claims] In a pulsed magnetic field generator comprising a pulsed electromagnet that generates a pulsed magnetic field by applying a pulsed current, and a drive circuit that drives the pulsed current to the pulsed electromagnet, a resistance value greater than a characteristic impedance of the pulsed electromagnet is provided. A pulsed magnetic field generating device comprising: a terminating resistor having a terminating resistor; and a pulse current delaying means having a characteristic impedance substantially the same as the characteristic impedance, which is disposed between the pulsing electromagnet and the terminating resistor.