JPH0441563Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a probe current setting device for an electron beam probe in an X-ray microanalyzer or the like.

In an X-ray microanalyzer or the like, the probe current, that is, the current of the electron beam that irradiates the sample, is adjusted by changing the power of the condenser lens of the electron beam. However, if the electron acceleration voltage of the probe is changed while the power of the condenser lens is kept constant, the probe current will also change.

This invention allows even if the electron acceleration voltage of the probe is changed,
This was done with the aim of obtaining a probe current setting device that prevents the probe current from changing.

The present invention uses a probe current setting means, an electron acceleration voltage detection means of the probe, a signal indicating the probe current output from the probe current setting means, and an output signal of the acceleration voltage detection means, and sets the acceleration voltage as a parameter. A control circuit that calculates a condenser current value corresponding to the probe current set from the functional relationship between the power of the condenser lens and the probe current, and a control circuit that calculates the current value of the above calculated value to the condenser lens. The present invention provides a probe current setting device consisting of a condenser lens power supply that supplies a power supply to a condenser lens.

The present invention will be explained below with reference to Examples. FIG. 1 shows the relationship between the power of the condenser lens and the probe current using the electron acceleration voltage Acc of the probe as a parameter. Now, if a certain constant probe current is iP and the power of the condenser lens to obtain this probe current is ic, then ic changes depending on the electron acceleration voltage Acc, and ic=iof(Acc)...(1) It can be expressed in the form of In equation (1), io is the reference value and is a function of the probe current ip, and the reference acceleration voltage is ao
When io = (ip) ...(2), (ip) is the parameter ao in Figure 1.
This gives the curve when .

FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention. 1 is a probe current setting circuit, which is a potentiometer to which a constant voltage is applied;
A probe current setting knob (not shown) is coupled to the slider S. Let the voltage of the slider S be e1. e1 is a signal indicating the probe current. 2
is an electron acceleration voltage detection section of the probe, and its output signal and the voltage of e1 are input to the control circuit 3. By substituting equation (2) into equation (1) above, ic=F(Acc,
ip), so it can be expressed in the form ic=Fr(Acc)×ip, and sufficient accuracy can be obtained by setting Fr(Acc)=√, so the control circuit 3 receives the input e1 and Acc signals. Therefore, e2=√×
It calculates e1 and outputs voltage signal e2. 4 is a condenser lens power supply circuit, and a voltage signal e
A current proportional to 2 is passed through the condenser lens 5 to give a predetermined power, and the probe current is adjusted to the set value.

Conventionally, in X-ray microanalyzers, the probe current changes when the electron acceleration voltage is changed, so it was necessary to readjust the probe current, but with the present invention, the probe current can be adjusted arbitrarily even if the acceleration voltage is changed. Automatically adjusted to the set constant value.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the power of a condenser lens, probe current, and accelerating voltage, and FIG. 2 is a block diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Probe current setting circuit, 2... Accelerating voltage detection section, 3... Control circuit, 4... Condenser lens power supply circuit, 5... Condenser lens.

Claims (1)

[Scope of utility model registration request] Based on the probe current setting means, the electron acceleration voltage detection means of the probe, and the output signals of both of the above means, from the functional relationship between the power of the condenser lens and the probe current with the acceleration voltage as a parameter,
An electronic probe, etc. consisting of a control circuit that calculates a condenser lens current value corresponding to a set probe current, and a condenser lens power supply that is controlled by the control circuit and supplies the current of the above calculated value to the condenser lens. probe current setting device.