JP2687834B2 - Charge converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for converting a positive ion beam from an ion source into a negative ion beam, and more specifically, to a charge conversion device installed before a tandem electrostatic accelerator. Regarding

[0002]

2. Description of the Related Art A tandem electrostatic accelerator has the advantages that it can obtain energy several times as high as the acceleration voltage and that the ion source can be placed near the ground potential. In such a tandem electrostatic accelerator, it is necessary to generate a negative ion beam in the preceding stage.

As a charge conversion device for producing the negative ion beam, an alkali metal (for example, lithium) filled in a container is heated to a high temperature to be evaporated,
There is a structure in which a positive ion beam from an ion source is passed through the vapor and a negative ion beam is generated by charge conversion (absorption of electrons from alkali metal) that occurs during the passage. The reason why the alkali metal is used in this type of charge conversion device is that when the alkali metal collides with positive ions, electrons are easily emitted to the positive ions.

[0004]

By the way, in the above-mentioned charge conversion apparatus, since alkali metal is consumed during operation, the alkali metal is replenished before the ion beam charge conversion becomes impossible. Therefore, it is required to detect the remaining amount of the alkali metal in the container, that is, to predict the depletion of the alkali metal, but there is no suitable method therefor.

That is, in order to utilize the alkali metal for charge conversion, it is necessary to heat the alkali metal to a high temperature,
Therefore, it is impossible to adopt a general method such as providing a peep window for confirming the remaining amount of the alkali metal in the charge conversion container or the like.

The present invention has been made in view of such circumstances, and its purpose is to know the remaining amount of alkali metal in a container for charge conversion before charge conversion becomes impossible. It is to provide a charge conversion device having a structure capable of

[0007]

In order to achieve the above-mentioned object, the charge conversion device of the present invention, as shown in FIG. 1 corresponding to the embodiment, stores alkali metal M in a container (charge conversion cell) 1. A means for detecting the temperature (temperature detector 2) and, based on the detected temperature value, after the temperature of the alkali metal M in the container 1 starts to change, the point at which the temperature change stops is taken as the starting point. After that, means (for example, the computer 3) for obtaining the time until the temperature starts to change again is provided,
It is characterized in that the stop time t of the temperature change is used as information for knowing the amount of the alkali metal M in the container 1.

[0008]

First, the alkali metal M filled in the container 1
Is in a molten state during the operation of the apparatus, and is gradually cooled to become a solid after the operation of the apparatus is stopped, that is, the heating by the heater 12 is stopped.

[0009] Here, like other general metals, when the alkali metal is cooled from a molten state and changes its state to a solid, the temperature drop is temporarily stopped by the release of latent heat in the cooling process. There is a period during which the temperature remains constant (see FIG. 4). Moreover, the stop time t changes in correlation with the amount of metal.

Therefore, in the present invention, focusing on the above points,
Stop time t of temperature drop (change) due to the above-mentioned latent heat release
Is detected, the remaining amount of the alkali metal M in the container 1 is obtained from the detected value.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. First, in the tandem electrostatic accelerator, as shown in FIG. 2, the positive ion beam extracted from the ion source A is negatively ionized by the charge conversion device B, and the negative ion beam is grounded at both ends to a central portion. The negative ion beam is converted into positive ions at the center of the accelerating tube C by guiding the negative ion beam to the inside from one end side of the accelerating tube C to which a positive high voltage is applied, and accelerating the ion. The target D can be irradiated with a high-energy ion beam by accelerating again toward.

Further, as shown in FIG. 1, the charge conversion device B has a charge conversion cell 1 having an ion inlet 1a and an ion outlet 1b disposed therein, and an alkali metal such as lithium in the boiler portion 11. M is accommodated. Then, the alkali metal M is heated by the heater 12 to fill the inside of the cell 1 with the alkali metal vapor, and a positive ion beam from the ion source A is passed through the vapor to generate a negative ion beam. Is configured to.

A temperature detector 2 is arranged inside the charge conversion cell 1. The detector 2 is for detecting the temperature of the alkali metal M filled in the cell, and for example, a thermocouple or the like is used, and its voltage signal is supplied to the computer 3 via the A / D converter 4.

The computer 3 operates in the following manner.
The voltage signal from the temperature detector 2 is taken in every moment, and the stop time t of the temperature drop described above is obtained based on each voltage data, and the stop time t and the preset threshold value are set. The value Th is compared, and the alarm device 5 is instructed to issue an alarm according to the comparison result.

FIG. 3 is a flow chart showing the operation of the computer 3, and the operation of the embodiment of the present invention will be described below with reference to this figure. First, at the time when the operation of the apparatus is stopped (when the heater 12 is turned off), the values detected by the temperature detector 2 are sampled moment by moment, and the temperature of the alkali metal M in the charge conversion cell 1 is calculated from these data. After monitoring the temperature, the time until the temperature starts to decrease again after the temperature starts to decrease, that is, the stop time t shown in the temperature decrease curve in FIG. Ask.

Next, the determined stop time t and the set threshold value T
When h is compared with h and the stop time t is long (t> Th), it is confirmed that the operation of the apparatus is restarted, and then the process returns to the initial step. On the other hand, the stop time t is the threshold Th
In the following cases, the alarm device 5 is instructed to issue an alarm, and after that, it is confirmed that the charge conversion cell 1 has been replenished with the alkali metal M and that the operation of the device has been restarted. Return to step.

Here, the threshold value Th is the charge conversion cell 1
The stop time t with respect to the amount of change of the alkali metal M inside is measured and investigated in advance, and based on the calibration data,
By setting the value corresponding to the remaining amount of the alkali metal before the time when the charge conversion efficiency of the device is lowered, the alkali metal M can be replenished before the use of the device becomes impossible. . Further, if the stop time t obtained from the temperature detection value is converted using the above calibration data, it becomes possible to quantitatively know the remaining amount of the alkali metal M in the charge conversion cell 1.

In the above embodiment of the present invention, the output of the temperature detector 2 is taken into the computer 3 and the stop time t is reached.
However, in the present invention, for example, the output of the temperature detector 2 is changed to XY.
The temperature drop curve shown in FIG. 4 is recorded / displayed by supplying it to a recording device such as a plotter or a display device such as a CRT, and the operator monitors the curve, whereby the alkali metal M in the charge conversion cell 1 is monitored. It is also possible to adopt a method of predicting the depletion of.

In the above embodiment, the alkali metal M
The remaining amount of the alkali metal M is obtained from the stop time at the time of the temperature drop. However, the present invention is not limited to this, and the temperature rising process of the alkali metal M in the charge conversion cell 1, that is, the operation of the apparatus is performed. In the heating process after the start, alkali metal M
When the state changes from solid to liquid, the time when the temperature rise (change) is temporarily stopped by absorption of latent heat may be detected, and the remaining amount of the alkali metal M may be obtained from the stop time.

[0020]

As described above, according to the charge conversion device of the present invention, the temperature of the alkali metal in the charge conversion cell (container) is detected, and the temperature change stop time based on the detected value is used. Since it is configured so that the remaining amount of alkali metal can be confirmed, it is possible to predict in advance the depletion of alkali metal in the charge conversion cell (container), which allows the conversion device to be used before it becomes unusable. Measures such as replenishing metal can be taken. As a result, improvement of the operating rate of the device can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of essential parts of an embodiment of the present invention.

FIG. 2 is a block diagram showing the basic configuration of a tandem electrostatic accelerator.

FIG. 3 is a flowchart showing the operation of the computer 3 according to the embodiment of the present invention.

FIG. 4 is a temperature drop curve showing a cooling process from a molten state of an alkali metal.

[Explanation of symbols]

 A ... Ion source B ... Charge conversion device 1 ... Charge conversion cell 1a ... Ion inlet 1b ... Ion outlet 11 ... Boiler unit 12 ... Heater 2 ... Temperature detector 3 ... Computer 5 ... Alarm device

Claims (1)

(57) [Claims] 1. A container containing an alkali metal and a heater for heating the alkali metal are provided, and a positive ion beam from an ion source is passed through the alkali metal vapor generated in the container by the heater heating. In the device for converting to a negative ion beam by means of means for detecting the temperature of the alkali metal in the container, based on the temperature detection value, after the temperature of the alkali metal in the container begins to change, the Starting from the time when the temperature change stops,
After this, means for determining the time until the temperature starts to change again is provided, and the stop time of the temperature change is used as information for knowing the amount of alkali metal in the container. Charge conversion device.