JPH0329759Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a radiation measuring device that measures radiation in a vacuum using a microchannel plate as a sensor.

[Technical background of the invention and its problems]

FIG. 1 shows a conventional example of a radiation measuring device using a microchannel plate as a sensor. A vacuum container 1 is always kept in a high vacuum state by a vacuum pump 10, and when radiation 2 enters here and enters a microchannel plate (hereinafter referred to as MCP) 3,
Here, the electrons are multiplied and converted into a charge pulse at the anode 3.
Output from a. The output from the MCP 3 is amplified to a distinguishable level by a preamplifier 4, and compared with an externally set voltage in order to remove noise components by a waveform shaping circuit 5. Charge levels equal to or higher than the set charge level are counted as logic pulses. 6 and is counted and sent to a required data processing device 7. 8,9
are a high-voltage power supply and a bias power supply for electron multiplication in MCP3, respectively, and high-voltage power supply 8 is normally
1000 to 1500V, and the bias power supply 9 applies 100 to 200V, respectively.

With the conventional device described above, there is no problem if the vacuum pump 10 is operating normally and the vacuum container 1 is maintained at a high vacuum, but if the vacuum pump malfunctions, the vacuum level may drop or the MCP 3 may If you open the lid of vacuum container 1 while applying high voltage,
There were many cases where MCP3 was completely destroyed.

[Purpose of the invention] The purpose of the invention is to provide a radiation measuring device that can avoid permanent destruction of the MCP even when a decrease in the degree of vacuum occurs.

[Summary of the idea]

The present invention is a radiation measuring device that measures radiation incident into a vacuum container maintained at a high vacuum by an MCP placed in the container, and a vacuum probe is provided in the vacuum container to determine the degree of vacuum within the container. is characterized in that the high voltage applied to the MCP is cut off by a signal from the vacuum probe when the vacuum level falls to a vacuum level that allows for a predetermined margin for the vacuum level that causes permanent damage to the MCP. A radiation measuring device was realized and the intended purpose was achieved.

[Example of idea]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 2 and 3 show an embodiment of the radiation measuring device according to the present invention. In FIG. 2, a vacuum vessel 1, an MCP 3, a preamplifier 4, a waveform shaping circuit 5,
The components of the counter 6, data processing device 7, high voltage power source 8, bias power source 9, and vacuum pump 10 are the same as those in the device shown in FIG.

Then, a vacuum probe 11 is provided near the MCP 3 in the vacuum container 1, and a high voltage power supply 1 for the vacuum probe is installed.
A high voltage is applied by the current detector 13.
are connected in series. On the other hand, a resistor 14 is connected in series to a high voltage power supply 8 that applies a high voltage to the MCP 3, and its output is connected to the MCP 3 on one side and the emitter of a high voltage switch transistor 15 on the other side. The collector of the high voltage switch transistor 15 is connected to the positive electrode of the high voltage power supply 8, and the base thereof is connected to the output signal of the current detector 13.

An example of the vacuum probe 11 is shown in FIG. A pair of probe electrodes 11b, 1 are attached to the probe support 11a.
1c has a protruding shape, and is provided near the MCP 3 with a green plate 16 sandwiched therebetween. The distance d between the probe electrodes 11b and 11c and the applied voltage _V3 are determined using Patsien's law to ensure that discharge occurs between the probe electrodes at a vacuum level that allows for a predetermined margin for the vacuum level at which the MCP3 undergoes permanent damage. Set it to happen.

In the radiation measuring device according to the embodiment of the present invention configured as described above, when the degree of vacuum in the vacuum container 1 decreases due to, for example, stopping the vacuum pump 10, the vacuum probe 11 first discharges. At this time, the current detector 13
is activated and outputs a vacuum level reduction signal to the outside. This signal enters the base of the high-voltage switch transistor 15, turns on the high-voltage switch transistor 15, cuts off the high voltage being applied to the MCP 3, and prevents permanent damage to the MCP 3. Further, when the high voltage switch transistor 15 is turned on, the high voltage power supply 8 is protected by the resistor 14 connected in series.

It should be noted that the present invention is not limited to the embodiments described above, and can be implemented with modifications as described below.

[1] The vacuum probe is not limited to the one shown in FIG. 3, and a vacuum gauge capable of high-speed operation that flows a small amount of gas may be used instead.

[2] In addition to the vacuum probe near MCP3,
If it is provided near the vacuum pump 10 or near the opening of the vacuum container 1, there is an advantage that a decrease in the degree of vacuum can be detected more quickly.

[3] The radiation measuring device according to the present invention can be used as a sensor.
Since it uses MCP, it can be directly applied to measurements of electron beams or charged particles in vacuum.

[Effect of idea]

As described in detail above, according to the present invention, a vacuum probe is provided in the vacuum container in which the MCP is placed, and the vacuum probe is installed in the vacuum container so that the vacuum level within the vacuum container does not decrease to a level that would cause permanent damage to the MCP. Since the high voltage applied to the MCP is quickly detected by detecting a drop in the voltage, it is possible to prevent permanent damage to the MCP and completely eliminate the problems of conventional devices. .

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional example of a radiation measuring device using MCP as a sensor, Fig. 2 is a block diagram showing a radiation measuring device according to an embodiment of the present invention, and Fig. 3 is a block diagram showing a radiation measuring device according to an embodiment of the present invention. It is a detailed view. 1... Vacuum vessel, 2... Incident radiation, 3... Microchannel plate (MCP), 4... Preamplifier, 5... Waveform shaping circuit, 6... Counter, 7
...Data processing device, 8...High voltage power supply, 9...Bias power supply, 10...Vacuum pump, 11...Vacuum probe, 11a...Probe support, 11b, 1
1c... Probe electrode, 12... High voltage power supply for vacuum probe, 13... Current detector, 14... Resistor,
15... High voltage switch transistor, 16...
...Zetryoku board.

Claims (1)

[Scope of utility model registration request] In a radiation measurement device that measures radiation incident into a vacuum container maintained at a high vacuum using a microchannel plate placed in the container, a pair of probe electrodes are provided protruding from a probe support at an interval, and one A high voltage is applied between the pair of probe electrodes by a dedicated high voltage power supply, and a vacuum probe with a current detector connected in series is provided in the vacuum container, and a high voltage is applied to apply a high voltage to the microchannel plate. A resistor is connected in series with the power supply, and one output of this resistor is connected to the microchannel plate and the other is connected to the emitter of a high voltage switch transistor, and the collector of this high voltage switch transistor is connected to the microchannel plate. The output signal of the current detector is connected to the base of the transistor, and the distance between the pair of probe electrodes of the vacuum probe and the voltage to be applied are A radiation measurement device characterized in that the microchannel plate is set so that discharge occurs between the probe electrodes at a degree of vacuum that allows for a predetermined margin in the degree of vacuum that causes permanent damage.