JP3390913B2 - Infrared imaging video bolometer, frame member used therefor, and method of measuring incident power distribution using infrared imaging video bolometer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared imaging video bolometer, a frame member used therein, and an incident power distribution measuring method using the infrared imaging video bolometer.

[0002]

2. Description of the Related Art IR imaging bolometer (IRI
B) was created as a detector that measures the amount of plasma radiation from the temperature change of a metal thin film [TFR Group (presented b
y AL Pecquet), Journal of Nuclear Materials, 93
-94, 377 (1980), JC Ingraham and G. Tonini, Re
v. Sci. Instrum. 61, 2976 (1990)]. The method of using an IR camera for measuring the temperature change of a thin film was first proposed in a paper describing the relationship between the thin film temperature during operation, wavelength, and signal-to-noise ratio [G. Apruzzese and G. Tonini, Rev. Sc
i. Instrum. 61, 2976 (1990)]. The two-dimensional IRIB concept initially introduced the use of a two-dimensional partitioned matrix to project the temperature rise of the absorber [GA Wurd
en, in Diagnostics for Experimental Thermonuclear
Fusion Reactors, edited by PE Stott et al. (Ple
num, New York, 1996), pp. 603-606]. Then, it developed into a two-dimensional array composed of each pixel in a metal thin film [GA Wurden, BJ Peterson and S. Sudo, Re.
v. Sci. Instrum. 68, 766 (1997), GA Wuerden, U.
S. Patent 5,861,625]. This technique, known as the Infrared Imaging Bolometer (IRIB), has already been designed, assembled, and tested on CHS equipment [GA Wurden and BJ Peterson, Rev. Sci. Instu.
rm. 70, 766 (1999)]. Details about IRIB are shown below.

As shown in U.S. Patent 5,861,625
In addition, two identically shaped markers with a two-dimensional hole pattern
A thin metal film is sandwiched between the discs,
Figure 2 shows a two-dimensional array in which thin films are exposed on both sides from the holes in
Shown in. Pass one side of the array through a pinhole or slit.
It faces the emitted plasma radiation. On the other hand, IR power
Mela is the back side of the blackened thin film array, as shown in Figure 2.
The thin film array is directed at the incident plasma
The emitted light causes a temperature rise of the pixel. Each copper mask
It acts as a heat sink for the pixels, and each pixel
The sensitivity K of each pixel depends on the size, thickness, and thermal characteristics of the
The thermal diffusion time τ is determined. Thin film thickness t _fIs assumed
Should be decided to stop the highest energy photon
Is.

The diameter of the thin film should be determined so that the heat diffusion time of each pixel matches the frame interval Δt of the camera. The relationship between the pixel diameter d _pix and its thermal diffusion time is given by equation (1),

[0005]

[Equation 1]

Κ is the thermal diffusion coefficient due to the metallic properties of the thin film.

If this value is large, there is a problem that the measurement time interval is not sufficient and the amount of heat absorbed before the next measurement does not fall to the reference value. However, if this value is small, heat diffusion is rapid. Happen too much to. Spatial resolution is determined by the pinhole and camera view structure. Each pixel is signal calibrated by injecting a choppered He-Ne laser light of a certain frequency with a known laser output power into the blackened film surface and measuring the values of τ and κ. The emitted light power to each pixel is given by equation (2).

[0008]

[Equation 2]

Here, T is the temperature of the metal thin film in consideration of the temperature of the mask, as in the case of the resistance type metal film bolometer.

[0010]

By the way, in the conventional bolometer as described above, various problems are caused by a matrix-shaped mask divided into segments.

The first is that due to heat exchange between adjacent pixels, which are recesses on the copper mask, heat leaks past the mask to pixels that have no inherent signal, such as crosstalk.

Second, a part of the edge of the pixel on the mask is a shadow of the edge part of the mask. The third problem arises from the above shadow, but when the carbon spray used for blackening is sprayed on the metal thin film, the spray is because the surface of the metal thin film and the copper mask on it are not on the same plane. That is, the carbon film is not uniform.

In addition, a large number of pixels are fixed by a mask divided into segments, and a part of the metal thin film covering the mask becomes a shadow of the mask to make it unusable, so that the spatial resolution is lowered. is there.

The present invention has been made to solve the above problems, and provides an improved infrared imaging video bolometer, a frame member used for the same, and an incident power distribution measuring method using the infrared imaging video bolometer. The purpose is to do.

[0015]

The infrared imaging video bolometer of the present invention comprises a vacuum vessel in which plasma is confined and a vacuum vessel attached to the vacuum vessel. The inner surface is black by spraying carbon to avoid light reflection from the plasma. A light shield tube that has been converted to an infrared vacuum window provided on the end surface of the tube and attached to the vacuum container, and a plate provided on the end surface of the tube opposite to the infrared vacuum window, A plate having pinholes or slits for taking in light from plasma, a frame member provided in parallel with the plate, attached to the tube apart from the plate, having a thin film, and the infrared vacuum window. and a infrared camera views the film in the frame member through the frame member is a metal And the membrane, a two frames of a thermally conductive material, rhino in each frame the metal thin film
A frame having a size slightly smaller than the width, and the frame is held so that the metal thin film is sandwiched by the frame so as to cover the window and exposed on both sides. .

The frame member for an infrared imaging video bolometer of the present invention comprises two frames made of a metal thin film and a heat conductive material, and each frame is made of the metal.
A frame provided with a window slightly smaller than the size of the thin film, the metal thin film being sandwiched by the frame so as to cover the window and held so as to be exposed on both sides. And

It is preferable that the frame member has a cavity capable of blocking light while adjusting the pressure on both sides of the metal thin film.

An incident power distribution measuring method using an infrared imaging video bolometer according to the present invention comprises a step of measuring a thin film temperature distribution of the frame member using the infrared imaging video bolometer, and a step of measuring the metal using an FTCS algorithm. Determining the incident power distribution on the thin film.

IR imaging video bolometer (I
RVB) uses a copper frame member to remove the mask that separates the pixels from the IRIB and to hold the large metal film as shown in FIG. This IRVB
This increases the detectable area by about 60%, which in turn increases the spatial resolution by about 25%.

The problem of the concave portion on the mask described above is
This can be overcome by fixing the copper frame and the metal film in tight contact with the screw near the edge of the copper frame member, and further improvement is possible by using an indium gasket.

Further, it is possible to prevent a shadow from being formed on the metal thin film by the copper mask. Further, this IRVB has the flexibility in experiments that the sensitivity can be adjusted to the signal strength because the size and number of bolometer pixels can be changed according to the experimental situation.

Another feature is that the IRIB image is a divided image, while the IRVB can obtain a full video image of the plasma radiation.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION (1) Configuration of the Invention The overall configuration of the infrared imaging video bolometer of the present invention is the same as the configuration shown in FIG. That is, the vacuum container 1 confines the plasma. A light shield tube 3 is attached to the vacuum container 1, and its inner surface is blackened by spraying carbon to avoid light reflection from plasma. An infrared vacuum window 5 is provided on the end surface of the tube 3 and is attached to the vacuum container 1.

A plate 7 is provided on the end surface of the tube 3 on the side opposite to the infrared vacuum window 5, and a pinhole or slit 9 is formed so that light from the plasma is introduced into the tube 3. A frame member (mask) 11 is provided in parallel with the plate 7, and is attached to the tube 3 while being separated from the plate 9. The frame member 11 has a thin film.

An infrared video camera 13 is provided in the vicinity of the infrared vacuum window 5 so that the thin film of the frame member 11 can be viewed through the infrared vacuum window 5.

The structure of the frame member 11 including the IRVB thin metal film 27 will be described with reference to FIGS.

A. The round copper frame 21 shown in FIG. 4 is composed of two frames, a front frame 21a and a back frame 21b, and is made of non-oxidized copper having the following holes. Further, the frame 21 is provided with a square window 29 having a size smaller than that of the metal thin film 27.

Four holes, that is, holes 23 for assembling bolts, are arranged at equal intervals along the edge for mounting the frame 21 of the light shield.

Frame 21 for tightening the bolts
4 holes on each side of top, bottom, left and right, hole for fixing bolt 25
Has been opened. This fixes the metal thin film 27 and provides sufficient thermal contact between the metal thin film 27 and the frame 21.

To prevent the air pressure from differing on both sides of the metal thin film 27, a vent hole 31 as shown in FIGS. 5 and 6 is formed so that the air can pass through. At that time, since the light does not directly pass through the vent hole (hole) 31 and the other cannot be seen through the vent hole 31 when viewed from either side, the structure is as shown in FIG. 6 when viewed from a cross section. It is a crank type.

A large rectangular window 29 is opened in the center of the frame 21, and its size is slightly smaller than that of the metal thin film 27.

B. The metal thin film 27 has a thickness of 1 to 4 μm and can be made of aluminum, gold, or another metal.

C. Stainless steel bolts, washers, and nuts are used to sandwich and secure the metal film 27 between the two copper frames 21.

D. The metal thin film 27 and the frame 21 on the IR camera 13 side are painted black with carbon spray in order to increase the emissivity of the metal thin film 27 to improve the measurement sensitivity.

E. The indium gasket used between the metal film 27 and the frame 21 is optionally used to improve the thermal contact between the metal film 27 and the frame 21.

(2) Operation of the present invention a. Method for Determining Incident Power from Measured Temperature of IR Camera The incident power distribution on the metal thin film 27 as a function of time is F for solving the thermal diffusion equation for the metal thin film 27.
Using the TCS (Forward Time Center Space) algorithm, the following equation is used to obtain the temperature distribution on the metal thin film 27 in the time function measured by the IR camera.

[0037]

[Equation 3]

Each parameter is as follows.

X-horizontal position on metal thin film 27 y-vertical position on metal thin film t-time P _rad (x, y, t) -radiation power t incident on metal thin film 27 _f- thickness of metal thin film 27-heat conductivity of metal thin film 27-width of bolometer pixel Δt-time interval T (x, y, t) of each frame of IR camera 13-temperature of metal thin film 27- The conditions for a stable solution for the thermal diffusion coefficient FTCS algorithm are:

[0040]

[Equation 4]

And is used to determine the minimum value of l _bol . The temperature measurements of the image of the IR pixels that make up each pixel of the video bolometer can be averaged to reduce noise and increase sensitivity.

If necessary, the pixel size l _bol can be made larger than the minimum value in order to improve the SN ratio by sacrificing the temporal resolution and the spatial resolution depending on the signal level. This method unique to IRVB can be used more flexibly as needed than IRIB whose spatial resolution is fixed by a copper mask.

B. Since t _f may blacken the mask surface on the IR camera 13 side in the calibration assembly process of the metal thin film 27, κ and k may become non-uniform.
Signal calibration is required. Equation (3) can be rewritten in the form of equation (2).

[0044]

[Equation 5]

Therefore, calibration is done by determining two quantities for each bolometer pixel. This calibration is done for each IR pixel by κ (x, y) and τ (x,
The maximum effect is achieved by determining y) and averaging the quantities on the IR pixels that make up the bolometer pixel. The heat time τ is measured by rapidly heating the metal thin film 27 and measuring the temperature delay time of each pixel after the heat source moves. The sensitivity K of each IR pixel is such that the metal thin film 27 is heated by a light source having a constant intensity, and a thermal equilibrium state occurs

[0046]

[Equation 6]

It can be relatively measured by measuring the temperature distribution in. Metal thin film for flame temperature 27
The temperature distribution above is compared with the temperature distribution of the perfectly uniform metal film 27 given by equation (6).

[0048]

[Equation 7]

The edges of the metal thin film 27 are x = ± a /
2, y = ± b / 2, and S _heat is the power density from a constant heat source on the metal thin film 27. Since S _heat is not known, the ratio of the measured temperature to this temperature distribution is generalized to the central pixel of the IR camera 13 on the thin film making the relative calibration of each pixel.

[0050]

[Equation 8]

Output power Pla from the He-Ne laser
When ser is known, the Gaussian distribution of laser light is given by equation (9).

[0052]

[Equation 9]

Here, α and β represent the radii of the laser beams in the x and y directions, respectively, and are the values when the center of the thin film is heated by the laser. The initial time of the thin film 27 is t =
When set to 0, the temperature change T _laser obtained at a position away from the center of the thin film 27 is

[0054]

[Equation 10]

Where α, β << a, b. When the thermal limit value of the thin film 27 that has reached the thermal equilibrium state (t = ∞) is taken, integrated on the IR pixel, and divided by the area, the center temperature T _center of the IR pixel is obtained.

[0056]

[Equation 11]

Solving the equation (11) for K _center , the amount of heat K (x,
y) is determined by the following equation.

[0058]

[Equation 12]

(3) Results Presented by the Present Invention Using the above equation, a test was conducted to examine the accuracy of the FTCS algorithm that gives the incident power on the metal thin film 27.

First, the laser incident power on the metal thin film 27 is modeled by the Gaussian distribution given by the equation (9). The solid line in FIG. 7 shows the results when P _laser = 20 mW and α = β = 4 mm. The incident power density of this model is the value expected from a typical LHD plasma (10 mW / cm ² ). Then, the resulting temperature distribution change of the metal thin film 27 is calculated using the equation (10) when the Fourier series terms (m, l) are up to 70 for each element.

In the present study, calculation is performed assuming a uniform gold thin film 27 (a = b = 9 cm, t _f = 1 μm, k
= 3.16 W / cm ° C., κ = 1.27 cm ² / s). FIG. 8 shows an example of changes in the temperature distribution of the metal thin film 27 in the first 40 ms when the time resolution Δt = 4 ms. The vertical axis represents the temperature change from room temperature. The temperature level in this case is the current I
It is much higher than the accuracy of the R camera 13 (0.025-0.1 ° C).

Finally, when the temperature distribution change is used, the incident power distribution is calculated by the FTCS algorithm using the equation (3) using l _{bo l} = 1 mm given by the equation (4).
The results are shown by the broken line in FIG. The peak difference between the distribution obtained by this calculation and the original Gaussian distribution is 6% or less. This shows that the thermal spray power distribution can be accurately reproduced by the FTCS algorithm.

[0063]

When compared to IRIB, IRVB has the following advantages.

1) For a mask in which the end portions of the pixel holes on the mask are shaded with respect to the thin film and the contact between the thin film and the mask is incomplete due to the curved mask. There are no incidents.

2) The spatial resolution is improved by about 25%.

3) A video image of the emitted light power is obtained using the FTCS algorithm.

4) A qualitative real-time video image of the plasma radiation is obtained.

5) A flexible pixel size can be selected to meet the data needs according to various parameters of the plasma experiment.

6) The SN ratio is improved by 2 to 5 times.

[Brief description of drawings]

FIG. 1 Conventional infrared imaging bolometer (IR
The figure which shows arrangement | positioning of the mask and thin film of IB).

FIG. 2 is a diagram showing an overall configuration of a conventional IRIB and an infrared imaging video bolometer (IRVB) of the present invention.

FIG. 3 is a plan view showing an arrangement of a mask and a thin film of an infrared imaging video bolometer (IRVB) of the present invention, showing an FTCS algorithm geometrical arrangement.

FIG. 4 is a perspective view showing an arrangement of a mask and a thin film of an infrared imaging video bolometer (IRVB) of the present invention.

FIG. 5 is an exploded view showing an air passage hole of the infrared imaging video bolometer (IRVB) of the present invention.

FIG. 6 is a cross-sectional view showing an air passage hole of the infrared imaging video bolometer (IRVB) of the present invention.

FIG. 7: Incident power density profile (solid line) and FTC
The graph of the Gaussian model of the S algorithm calculation result (broken line).

FIG. 8 is a graph showing the change in thin film temperature distribution with time as a parameter, this data being used for the FTCS algorithm calculations whose results are shown in FIG. 7.

[Explanation of symbols]

1 ... Vacuum container 3 ... Optical shield tube 5 ... Infrared vacuum window 7 ... Plate 9 ... Pinhole or slit 11 ... Frame member 13 ... Infrared video camera 21 ... Copper frame 21a ... Front frame 21b ... Back frame 23 ... Assembly bolt holes 25 ... Hole for fixing bolt 27 ... Metal thin film 29 ... windows 31 ... Bent Hall

Front page continuation (56) References The Institute of Electrical Engineers of Japan Material Optical and Visual Research Association, Japan, The Institute of Electrical Engineers of Japan, September 29, 1999, LAV-99-7-9 / 11-17,23 ~ 26 Rev. Sci. Instrum. 1999, vol. 70 No. 1 part 2,255-259 Rev. Sci. Instrum. 1997, vol. 68 No. 1 part 2,766 to 769 Fusioin Engineer and design, 1997, vol. 34/35, 301-305 (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01J 1/02 G01J 1/42 G01J 5/48 G01V 8/12 H01L 27/14 H04N 5/30-5 / 335

Claims (5)

(57) [Claims] 1. A vacuum container in which plasma is confined, a light shield tube attached to the vacuum container, the inner surface of which is blackened by carbon spray to avoid light reflection from the plasma, and which is provided on an end surface of the tube. An infrared vacuum window attached to the vacuum container, and a plate provided on the end surface of the tube on the side opposite to the infrared vacuum window, having a pinhole or slit, A plate for taking in, a frame member provided parallel to the plate, attached to the tube apart from the plate, and having a thin film, and an infrared camera for viewing the thin film of the frame member through the infrared vacuum window, The frame member includes two frames made of a metal thin film and a heat conductive material. The arm have slightly smaller one <br/> windows are provided than the size of the metal thin film, the metal thin film is sandwiched between the frame so as to cover the window, the plasma side and the infrared camera
An infrared imaging video bolometer, comprising: a frame held open to the side ; 2. The infrared imaging video bolometer according to claim 1, wherein the frame member further has a cavity capable of adjusting pressure on both sides of the metal thin film and blocking light. 3. A metal thin film and two frames made of a heat conductive material, each frame being provided with a single window slightly smaller than the size of the metal thin film. Is sandwiched by the frame so as to cover the window , the plasma side and the infrared camera
A frame member for an infrared imaging video bolometer, comprising: a frame held so as to be exposed to the side . 4. The red of claim 3, wherein the frame further has a cavity capable of regulating pressure on both sides of the metal thin film and blocking light.
Frame member for outside line imaging video bolometer . 5. A method of measuring a thin film temperature distribution of the frame member using the infrared imaging video bolometer of claim 1, and a step of obtaining an incident power distribution on the metal thin film using an FTCS algorithm. Method for measuring incident power distribution using infrared imaging video bolometer.