JPS6017049B2 - streak camera device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a streak camera device suitable for observing temporal changes in the intensity of light that changes at high speed, particularly for observing single light pulses.

(Background of the Invention) First, the basic configuration and operation of a streak camera will be briefly explained.

FIG. 1 is a schematic diagram of a streak camera device showing a streak tube in a perspective view.

FIG. 2 is a graph for explaining the positional relationship between the deflection voltage, the trigger pulse, and the twill point on the crab light surface.

In FIG. 1, the incident light L from the light source to be measured passes through the slit la to have a rectangular cross section, and then passes through the streak tube 2.
is made incident on the photocathode 21 of. This light causes the photocathode 21 to generate photoelectrons. While this photoelectron beam is accelerated and moves in the direction of the crab light surface 22 of the streak tube 2, it is deflected perpendicularly to the longitudinal direction of the incident slit by the sweep voltage applied to the deflection plates 23 and 24, and the crab light beam is It reaches above surface 22. Since the intensity of the deflection electric field generated between the deflection plates 23 and 24 changes over time, the degree to which the photoelectrons are deflected changes depending on the time point at which the photoelectrons pass between the deflection plates 23 and 24.

Therefore, the time point at which photoelectrons pass between the deflection plates 23 and 24 corresponds to the position on the pot light surface 22, and if the incident light L has a temporal change in intensity, the light and shade of the image will appear on the crab light surface 22. It appears as.

This image is called a streak image. In this way,
Changes in the intensity of the incident light L can be estimated based on the position on the crab light surface 22 and its brightness.

In order to measure pulsed laser emission that occurs within a few nanoseconds to several tens of picoseconds and chemiluminescence phenomena induced by pulsed laser using such a streak camera device, it is necessary to use a corresponding high-speed camera. It is necessary to generate a deflection voltage that changes with speed.

However, it is not easy to generate a deflection voltage with good linearity that changes at such a high speed. Therefore, only a portion with good linearity in the middle of a voltage several times the deflection voltage required to sweep the effective surface of the crab light surface 22 from the upper end to the lower end is used for deflection.

Further, an appropriate bias voltage is applied so that only the portion of the deflection voltage with good linearity sweeps from the upper end to the lower end of the crab light surface. It is necessary to synchronize the generation of this deflection voltage and the occurrence of the measured event.

Therefore, an optical delay means (
(not shown) to reach the slit la arranged on the input surface of the streak tube 2.

The photoelectric conversion element 5 detects the light before it enters the optical delay means and converts it into an electrical signal.

The trigger circuit 4 delays the electrical signal and generates a trigger pulse for starting the deflection voltage generating circuit 3.

Next, with reference to FIG. 2, the waveform of the incident pulsed light with the desired time relationship and the position on the crab light surface corresponding to the deflection voltage will be explained.

FIG. 2a is a graph showing the deflection voltage, where the horizontal axis is the time axis T and the vertical axis is the voltage V.

FIG. 2b is a graph showing a group of photoelectrons based on incident light ideally matched to the deflection voltage at the position of the deflection plate, where the horizontal axis is the time axis T and the vertical axis is the charge Q.

FIG. 2c shows the position on the crab light plane corresponding to the deflection voltage.

Assume that a trigger signal is input to the deflection voltage generation circuit 3 at time t shown in FIG. 2A, and a deflection voltage 41 is generated.

Assume that the photoelectron group 42 based on the light that caused the trigger signal to be generated passes through the center of the deflection space formed by the deflection plates 23 and 24 between times a and Th in FIG.

When the deflection voltage 41 shown in FIG. 2A is Va (Va>0), the photoelectrons that have reached the center of the deflection space formed by the deflection plates 23 and 24 form an emission line at the position indicated by A on the crab light surface 22 of the streak tube. The photoelectrons that reach the center of the deflection space when the deflection voltage 41 reaches Vb (Vb 0) generate a bright line at the position indicated by B on the flute light surface 22 of the streak tube.

Therefore, the photoelectron group forms a streak image between A and B in FIG. 2c.

The level of Vp of the deflection voltage 41 corresponds to the position of the same virtual surface as the total optical surface 22, and the level of Vq corresponds to the position N of the same virtual surface as the total optical surface 22.

Therefore, if the deflection voltage is at the level of Vp or Vq, the photoelectrons that reach the center of the deflection space will pass through the crab optical surface 2.
It is not possible to reach the effective surface of 2. Trigger signal Tt
Since the deflection voltage is maintained at Vp before it is input to the deflection voltage generating circuit 3, the position of the leak image by the deflected electron beam, that is, the bridging start position, is at the position M outside the crab light plane. be.

The above explanation is an ideal case, and it is extremely difficult to create such a synchronized state.

For example, it is desired to scan between positions A and B on the crab light surface in FIG. There are extremely difficult demands.

Normally, the voltage (Vp-Vq) requires several kilovolts.

To adjust the delay time of the trigger signal, obtain the optical path length of the optical system, the delay time of the electrical system, and the trigger response characteristics of the high-voltage circuit under pre-designed conditions, and insert an appropriate delay circuit into the electrical system, for example. Even if such considerations were taken, complete synchronization was not possible.

Therefore, a method is used to adjust the synchronization by repeating trial and error adjustment while actually observing the pulsed light.

During the adjustment, if the set delay time is too short (the trigger pulse is generated too quickly), the rope line is at position N outside the crab light surface 22 and does not appear on the fin light surface.

Conversely, when the delay time is too long (when the trigger pulse is generated slowly), the twill line is located at a position M outside the crab light surface 22 and similarly does not appear on the crab light surface. This makes the adjustment even more difficult.

(Object of the Invention) An object of the present invention is to provide a streak camera device that facilitates the above-mentioned adjustment and is particularly suitable for observing single light pulses.

(Structure of the Invention) In order to achieve the above object, the streak camera device according to the present invention includes a conversion surface that converts an incident particle beam into photoelectrons, a crab light surface, an electric field generating means that accelerates the photoelectrons in both directions of the crab light, a streak tube having a deflection plate that generates a deflection electric field in a direction perpendicular to the travel path along the path along which the photoelectrons are accelerated; and a deflection plate that generates a deflection electric field that exceeds the effective length of the optical surface of the streak tube in the scanning direction. a first deflection voltage generation circuit that applies a voltage to the deflection plate; and a second deflection circuit that applies a deflection voltage to the deflection plate that generates a deflection electric field within the effective length of the optical surface of the streak tube in the scanning direction. a voltage generation circuit; a control circuit for selecting which of the first or second deflection voltage generation circuit to operate; and a control circuit for selecting the deflection voltage generation circuit selected by the selection circuit in synchronization with generation of the particle beam. A trigger circuit to be activated and a delay means to adjust the time from the generation point of the particle beam to be measured until the particle beam reaches the photocathode of the streak tube or the point at which the trigger circuit is activated. ing.

In the streak camera device having the above configuration, first, the control circuit selects a second deflection voltage generation circuit that applies a deflection voltage to the deflection plate to generate a deflection electric field within the effective length of the light receiving surface of the streak tube in the scanning direction. By operating the lens in such a manner, the streak image can always be placed within the crab light plane.

In the first deflection voltage generation circuit, a streak image often does not appear on the crab light surface, and it is difficult to even judge whether the deflection voltage is generated late or early.

By selecting the second deflection voltage generating circuit, it becomes easy to judge whether it is slow or fast, and by adjusting the delay means based on this judgment, a streak image can be brought to the center of the crab light plane. After this adjustment is completed, when the second deflection voltage generating circuit is selected and operated, a streak image appears on the crab optical surface on an enlarged time axis. This makes it possible to observe changes in light that change rapidly with high precision. (Example) Hereinafter, the present invention will be described in more detail with reference to the drawings and the like.

FIG. 3 is a circuit diagram showing an embodiment of the streak camera device according to the present invention.

The construction of the streak tube 2, which is schematically illustrated, is the same as that described in detail above in FIG.

Also, the light source, the slit la, the optical path from the light source to the slit la, the optical delay means inserted into the optical path, etc. are omitted. A portion 30 surrounded by a broken line in FIG. 3 includes first and second deflection voltage generation circuits, a changeover switch for selecting one of the deflection voltage generation circuits, and the like.

The first deflection voltage generating circuit is a circuit that generates a deflection voltage that generates a deflection electric field between the deflection plates 23 and 24 that exceeds the effective length of the rear light surface 22 of the streak tube 2 in the scanning direction.

The second deflection voltage generation circuit is a circuit that generates a deflection voltage that causes the machine to generate a deflection electric field between the deflection plates 23 and 24 of the streak tube 2 that exceeds the effective length of the crab light surface 22 in the scanning direction. .

Voltage sources E and E2 are the voltage sources of the first and second deflection voltage generation circuits, respectively, and the output voltage of E is 2.4KV.
, that of E2 is 0.9KV.

Constant current sources 1 and 12 are constant current circuits included in the first and second deflection voltage generating circuits, respectively, and the current value of constant current sources 1 and 12 is three times that of constant current sources 12. Bias power supplies B and B are bias power supplies included in the first and second deflection voltage generation circuits, respectively. Bias power supply $ and output voltage of B2 are 1.2KV and 0.4KV respectively
It is. Capacitors C, , C2 and relatively high resistance value resistors R, , R2 are commonly used in the first and second deflection voltage generating circuits.

Note that a relationship of C and C2 is given between the capacitors. Switches S, S3, and S4 are changeover switches for selecting one of the deflection voltage generation circuits, and are
It is switched by a signal from 1.

The switching position shown in FIG. 3 shows a state in which the second deflection voltage generating circuit is selected.

The switch S2 is a trigger switch formed, for example, by a semiconductor switch.

The selected deflection voltage generating circuit can be operated from the time when the trigger switch S2 is closed.

When the first deflection voltage generation circuit is selected by the changeover switches S, S3, and S4, the capacitors C,
is charged to 2.4 KV by the power source E, via the resistor R,.

At this time, since the capacitor C, has accumulated electric charge that generates E, -B, (voltage of 1.V), there is a gap between the deflection plate 23 of the streak tube 2 and the other deflection plate 24 which is grounded. 2. Tour V-1. A voltage of V (=1.Fox V) appears.

When the trigger switch S2 is closed in this state, the charge in the capacitor C is discharged by constant current condensation.

This condition is shown in FIG. 4a by the curve indicated by the numeral 44. When the second deflection voltage generation circuit is selected by the changeover switches S, S3, and S4, the capacitor C
, are set to 0. Charged to chick V.

At this time, since the capacitor C has accumulated a charge that generates E2-& (voltage of 0.4 KV), the voltage between the deflection plates 23 and 24 of the streak tube 2 is 0. A voltage of chick V-0.4KV will appear. In this state, trigger switch S2
When the capacitor C is opened, the charge in the capacitor C is discharged by the constant current source 12. This state is shown in Figure 4a with the number 43.
It is shown by the curve shown.

Each of the curves 43 and 44 shows the conversion of the deflection voltage after the trigger switch S2 is closed, and they intersect when the deflection voltage becomes zero. In FIG. 4b, when a photoelectron passes through the center of the deflection space formed by the deflection electrodes 23 and 24, the deflection voltage is 1. If it is pine V, a competing point will occur at the position of M on the virtual crab light surface, and 11. If is V, a bright spot will similarly occur at the position N on the virtual light-receiving surface, indicating that it cannot actually be observed on the back light surface.

Further, when the photoelectron passes through the center of the deflection space, if the deflection voltage is 0.4KV, a bright spot will be generated at the position C of the crab light surface 22, and if it is -0.4KV, the crab light surface 22 will be D of
This shows that bran dots occur at certain locations. Next, an example of observing a single pulse of light using the apparatus of the embodiment will be described in detail.

First, the control circuit 31 forms a second deflection voltage generation circuit.

When the light source to be measured is excited in this state, the already adjusted timing and trigger pulse are generated, and the second deflection voltage generating circuit generates a deflection voltage as shown at 43 in FIG. 4.

As a result, photoelectrons caused by the light emission of the light source to be measured cause the crab light surface 22 to emit light somewhere from C to D.

If the emission is at or near C, it means that the trigger pulse occurs too late relative to the measurement event; if it is at or near D, it means that the trigger pulse occurs too late relative to the measurement event. It means that it is too early for

If the light emission occurs at C or a position close to C, the electrical delay of trigger pulse generation is shortened or the optical path length from the light source to slit la is increased.

If the light emission occurs at D or a position close to D, the electrical delay of trigger pulse generation is lengthened or the optical path length from the light source to slit la is shortened.

In this state, when the control circuit 31 forms the first deflection voltage generating circuit and excites the light source to be measured, a streak image of the light source to be measured should appear at the center of the crab light surface 22.

(Effects of the Invention) As explained above, the streak camera device according to the present invention is provided with a second deflection voltage generating circuit that generates a deflection electric field within the effective length of the rear optical surface of the streak tube in the scanning direction. and the first deflection voltage generating circuit can be used by switching.

If the control circuit first selects the second deflection voltage generating circuit and performs the measurement, it is possible to easily know whether or not the deflection voltage generation time point is appropriate for the measurement event. Based on the results, those relationships can be easily adjusted. After completing the adjustment,
If the first deflection voltage generating circuit is switched and used by the control circuit, a streak image of the event can be generated at the center of the optical surface of the streak tube. This streak image is formed by being deflected at a portion of the curve 44 in FIG. 4a with excellent linearity, and it is possible to obtain a streak image with excellent linearity and high time resolution.

[Brief explanation of the drawing]

FIG. 1 is a perspective view for explaining the structure of a streak camera. FIG. 2 is an explanatory diagram showing the waveform of the incident pulsed light at the position on the crab light surface corresponding to the deflection voltage of the streak tube and the desired time relationship. is a graph showing the deflection voltage, where is the voltage V; FIG.
Figure c is a graph showing the position on the optical surface corresponding to the deflection voltage. FIG. 3 is a circuit diagram showing in detail an embodiment of the deflection voltage generating circuit of the streak camera device according to the present invention. FIG. 4 is an explanatory diagram showing the operation of the embodiment, in which FIG. 4a is a graph showing the deflection voltage waveform, and FIG. 4b is a graph showing the relationship between the deflection voltage waveform and the position of the streak image. L...
...Incoming light, 1...Slit plate, la...
...Slit, 2...Streak tube, 4...Trigger circuit, 21...Photocathode, 22...Crab optical surface,
23, 24... Deflection plate, 25... Electron beam trajectory, 3, 30... Deflection voltage generation circuit,
31... Changeover switch control circuit, 41, 43
, 44... Deflection voltage waveform, E,, E2... Voltage source, S, S3, S4... Changeover switch, S2
...Trigger switch, R,, R2...
High resistance, C,, C2...Capacitor, 1,,1
2... Constant current circuit, B, B2... Bias power supply. 1 figure, 2 figures, 3 figures, 4 figures

Claims (1)

[Scope of Claims] 1. A conversion surface that converts an incident particle beam into photoelectrons, a fluorescent surface, electric field generating means that accelerates the photoelectrons in the direction of the fluorescent surface, and a path along which the photoelectrons are accelerated and moves along the moving path. a streak tube having a deflection plate that generates a deflection electric field in the orthogonal direction; and a first deflection voltage that applies to the deflection plate a deflection voltage that generates a deflection electric field that exceeds the effective length of the fluorescent surface of the streak tube in the scanning direction. a second deflection voltage generating circuit that applies to the deflection plate a deflection voltage that generates a deflection electric field within the effective length of the fluorescent surface of the streak tube in the scanning direction; and the first or second deflection generator. a control circuit that selects which of the voltage generation circuits to operate; a trigger circuit that activates the deflection voltage generation circuit selected by the selection circuit in synchronization with the generation of the particle beam; and generation of the particle beam to be measured. A streak camera device comprising a delay means for adjusting the time from the time point until the particle beam reaches the photocathode of the streak tube or the time point at which the trigger circuit is activated. 2. The streak camera device according to claim 1, wherein the conversion surface is a photocathode.