JPH01193656A - Current detector - Google Patents

Abstract

PURPOSE:To obtain a current detector with a higher S/N ratio, by connecting signals from four current detectors arranged along a beam duct to a voltage detector to extract a fine signal current alone due to an charged particle from detection signals thereof. CONSTITUTION:A sensor section is made up of four magnetic cores 2 wound with a coil and a metallic case 5. Voltage detectors 40 are arranged at an equal interval at the tip of a signal transmission line 70 to be connected separately to an arithmetic device 50. Signals V1, V2, V3 and V4 of the detectors undergoes an arithmetic processing by a specified equation and a fine current signal due to a charged particle is extracted to be shown on a current display device 60. This enables detection with a high S/N ratio against a large noise signal caused by a high frequency electromagnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a general accelerator for accelerating charged particles, and particularly to a detector suitable for monitoring minute currents.

[Conventional technology]

Conventionally, a current converter using a coil is a common current detector used in accelerators. Regarding this, please refer to KEK-77-21 (1978) (KEK-7
7-21 (1978)). A diagram of the principle of this current converter is shown in FIG. The current detector 10 includes a magnetic core 2, a coil 1 wound around it, and a resistor 4.
It is based on the principle that an induced voltage is induced in the coil 1 by the unsteady magnetic field generated by the charged particle beam 3, and by measuring the voltage across the resistor 4, the current value of the charged particle beam 3 can be determined. ing.

[Problem to be solved by the invention]

When the above-mentioned conventional technology is used in an accelerator, there are the following problems. As shown in FIG. 3, a current detector 10 is generally installed in a beam duct 21 in an accelerator. At this time, when the high frequency acceleration cavity 20 is located on the extension of the beam duct 21, a high frequency electromagnetic field 3o higher than the cutoff frequency leaks from the high frequency acceleration cavity 20 along the beam duct 21.

This more or less always exists. When this high frequency electromagnetic field 3o passes through the position where the current detector 10 is installed, the high frequency magnetic field is detected by the current detector 10 as noise. When detecting minute currents caused by charged particle beams, this high-frequency magnetic field causes noise signals, so S
There is a problem in that the /N ratio decreases, and in some cases, virtually no minute current signal is detected at all.

An object of the present invention is to improve the S/N ratio when a current detector detects a weak current.

[Means to solve the problem]

The above object is achieved by installing four conventional current detectors along the beam duct and processing each signal as follows to extract only the current signal component. As shown in FIG. 1, a conventional current detector 1
A current detector with a high S/N ratio is obtained by installing four zeros at equal intervals along the beam detector and extracting only minute current signals due to charged particles using the respective detection signals.

[Effect]

Hereinafter, the effects of the present invention will be explained. Let Vlt Vzt Va, Va be the detection signals of four minute current signal detectors installed at equal intervals along the beam duct.

V1=A+ε...(1)V
z = Ae' 0 + (eJcP-(2)V a
"A e"θ+εe2J'f' −(3
)V4=Ae"θ+ie"'f'...
・(4) Here, A and ε are complex quantities, and V
l.

Only real components are detected for Vz, Va, and V4.

The term A is a noise signal due to high frequency electromagnetic waves leaking from the high frequency acceleration cavity, and the term ε is a minute current signal due to charged particles. The phase O is proportional to the in-tube phase velocity of the high-frequency electromagnetic wave, and the phase is an unknown quantity proportional to the traveling velocity of the charged particles. Equations (1), (2), (3), and (4) include four unknown quantities A, 0. These are four independent equations for t and 'f'. Thereby, by processing these four equations, it is possible to extract the minute current signal ξ due to the charged particles.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. Four voltage detectors 40 are arranged at equal intervals at the end of the signal transmission line 70 of the sensor section, which is composed of four magnetic cores 2 around which a coil 1 is wound and a metal case 5 in which they are installed. Each signal V1? A current detector is constituted by a device 60 that inputs Vz, Va1, and V4 to a calculator 50 and displays a minute current value as a result of the calculation. With the above configuration, the minute current signal ε shown in equations (1) to (4) is calculated and extracted from the four data of the signal Vt+ Vi1 Va1 Va (7).

According to this embodiment, a minute current detection signal with a high S/N ratio can be obtained.

A second embodiment of the present invention will be described. The first embodiment assumes that all four current sensors have the same characteristics. Here, we will consider a case where the characteristics of individual current sensors are different. At this time, equations (1) and (2).

(3) and (4) are expressed by the following equations.

Vl = νt(A+ε)...(5)
Vz = v 2 (Ae' 0 + [e”/)
-(6)V3=vscAe"0+ie"P)
・=(7)V4=v4(Ae"e+ie"'P)
-(8) As is clear from equations (5) to (8), the voltage value vl, VZIV3. In order to extract a minute current value from Vi, calibration coefficients sil, si2. C3. Measure the si number, v1/ν1. V2/ν2. V3/ν3. V4/
94 as a new voltage value and apply it to the first embodiment.

This second embodiment is shown in FIG. In the first embodiment, a new calibration calculator 41 is added to the voltage detector 40 and the calculator 5.
It is characterized by being installed between 0 and 0. Thereby, there is an effect unique to this embodiment that even if the characteristics of the individual current sensors are different, it is possible to detect a minute current.

〔Effect of the invention〕

According to the present invention, it is possible to detect minute current signals caused by charged particles in an accelerator with a high S/N ratio with respect to large noise signals caused by a high frequency electromagnetic field from a high frequency acceleration cavity.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of one embodiment of the present invention, Fig. 2 is an explanatory diagram of the conventional example, Fig. 3 is an explanatory diagram showing problems, and Fig. 4 is an explanatory diagram of the second embodiment of the present invention. It is. DESCRIPTION OF SYMBOLS 1... Coil, 2... Magnetic core, 10... Current detector, 21... Beam duct, 40... Voltage detector, 60... Current display device.

Claims (1)

[Claims] 1. Arrange four current sensors consisting of a magnetic core wrapped with a coil, a resistor, and a case in which they are installed along the beam duct, connect the signal from the current detector to a voltage detector, and A current detector comprising: a calculation device that extracts only a minute signal due to charged particles from a detection signal; and a device that displays a minute current value as a result of the calculation.