JPS6222114B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a broadband electron beam detection device using a continuous dynode electron multiplier.

Electron beam detection devices using continuous dynode electron multipliers (so-called channeltrons) have recently been widely used. The principle of this type of detection device is that a potential difference is applied between both ends of a continuous dynode, and the secondary electrons generated by the electron beam incident on one end of the dynode are multiplied one after another, and the secondary electrons are collected at the collection electrode provided at the other end of the dynode. This detects changes in current value due to collected secondary electrons. Generally, when trying to detect a slow electron beam, the input end of a continuous dynode is
It is necessary to maintain a positive potential of about 100 V and apply a high voltage of about 2 to 4 KV to the other end of the dynode, that is, the output end. In this case, it is common to use a capacitor to extract the signal from the output end, which is kept at a high potential, by AC coupling, but this has made it difficult to detect input signals with low frequency components.
The present invention aims to solve such problems, and is characterized by detecting a signal from the low potential side of a continuous dynode and adding the detected signal to the detected signal from the high potential side. It is.

FIG. 1 shows an embodiment of the present invention, in which the high potential end A of a continuous dynode 1 is connected to the output +E _b of a high voltage power supply via a resistor R ₁ (about 100KΩ), and the low potential end Part B is resistance R ₂ (approximately 10MΩ), R ₃
(100KΩ) to ground. Such a connection provides a potential difference of about 2 to 4 KV between the AB terminals of the dynode 1. In conventional equipment, the first
As shown in the figure, only the signal detected from the output end A of the dynode 1 via the capacitor 2 and amplified by the amplifier 3 was used as the output signal. A voltage signal is extracted from the connection point of resistors R ₂ and R ₃ provided on the end side by DC coupling, amplified by an amplifier 4, and then only the low frequency component is extracted by a low-pass filter 5. This signal is applied to an adder circuit 7 consisting of an operational amplifier 6 and a resistor, and added to the detection signal obtained by the conventional method.

FIG. 2 is a schematic representation of the degree of signal amplification A in the apparatus of FIG. 1 as a function of the frequency f of the electron beam input signal. In Figure 2, the curve indicated by 8 shows the output characteristics of amplifier 3 detected from the high potential side of the device in Figure 1, and since capacitor 2 is used, the degree of amplification on the low frequency side is low. In particular, the degree of amplification for DC signals is zero. In Figure 2, the curve shown at 9 shows the output characteristics of the amplifier 4 detected from the low potential side of the dynode.Since the capacitance between the dynode itself and ground is large, the input capacitance of the detection signal is large. Therefore, high frequency signals are not detected, but signals in the low frequency region can be detected up to direct current. If curves 8 and 9 in Fig. 2 were added as they were, the degree of amplification would be particularly high in a specific frequency range, so
A low frequency filter 5 is provided between the amplifier 4 and the adder circuit 7 in the device shown in FIG. 1, and the device is configured so that the curve 9 in FIG. 2 becomes the characteristic curve shown by the dotted line 10. In this way, the output signal obtained from the output of the adder circuit 7 has improved characteristics, especially in the low frequency region, compared to that of the conventional device.

Note that the present invention is not limited to the embodiment shown in FIG. 1; for example, instead of providing a low-frequency filter in the low-voltage detection circuit, a high-frequency filter may be provided in the high-potential detection circuit, and the degree of signal amplification may be improved. It is possible to flatten the frequency characteristics of .

As explained in detail above, according to the present invention, the frequency characteristics of electron beam detection using a continuous dynode electron tube are significantly improved, and great effects can be obtained when used in various electron beam measurement devices.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a schematic diagram showing the characteristics of the device shown in FIG. 1... continuous dynode, 2... capacitor, 3,
4...Amplifier, 5...Low frequency filter, 7...Addition circuit.

Claims (1)

[Claims] 1. In a device using a continuous dynode electron multiplier having an AC coupling detection means for detecting a signal by AC coupling from the high potential side end where multiplied electrons are collected, the continuous dynode electron multiplier DC coupling detection means for detecting a signal by DC coupling from the low potential side end where signal electrons are incident; means for adding the outputs of the DC coupling detection means and the AC coupling detection means; An electron beam detection device comprising a filter circuit for flattening the frequency characteristics of the circuit until signals are added.