The improvement of scientific visualization methods [1-10] is
largely determined by the capabilities of modern registration tools. The
eight-channel 16-frame electro-optical camera is designed for high-speed image
recording of fast-flowing processes in the nano- and microsecond time ranges.
The appearance of the camera is shown in the Fig. 1.
Figure 1 - 8-channel 16-frame camera
"NANOGATE 22/16".
A simplified
optoelectronic circuit of the camera is shown in Figure 2.
Figure
2 – Optical-electronic circuit of the camera.
The recorded image, passing through the input lens, falls on a pyramidal
mirror beam-splitting system with eight electron-optical channels (EOC). The
hardware composition of the channel: shutter - a planar image intensifier tube
(IIT) with a diameter of 18 mm; image transfer – a 1:1 projection lens with an
aperture of 18°;
sensor - a CCD sensor with a size of 15.4×15.4 mm, 2048×2048
elements. The sensitivity of each channel is independently regulated by
adjusting the voltage on the microchannel plate of the image intensifier, which
allows you to study processes with a wide range of brightness. Each of the
eight channels registers two frames, the parameters of which are set
independently both in terms of exposure time (5 ns
÷
20 microseconds) and in
the inter-frame interval (5 ns
÷
1000 microseconds).
Each channel can operate
in multiple exposure mode, registering several phases of the process per frame.
The latest modification of NANOGATE-22/16 is a dust- and moisture-proof version
of the camera, has increased reliability and is designed to work in landfill
conditions. This application is not available for foreign cameras of a similar
class – CORDIN Model 222 (USA) and pco.dicam C8 UHS (Germany) [11,12].
Table 1 - The main technical characteristics
of the NANOGATE-22/16 camera
|
Parameter
|
Value
|
|
The number of independent electron-optical channels
|
8
|
|
The number of frames recorded during a single launch
|
16
|
|
The spectral range of the IIT photocathode
|
from 400 to 850 nm
|
|
The working diameters of the IIT photocathodes
|
18mm
|
|
The duration of the gating (gate) pulse (set
independently for each channel in 1 ns increments)
|
from 5 ns to 20 µs
|
|
Spatial resolution at all values of the duration of
strobe pulses, at least
|
44 pairs of lines/mm
|
|
The time interval between frames (channels)
|
from 5 ns to 20 µs
|
|
Shutter release time delay (set in 5 ns increments)
|
from 80 ns to 1,000 µs
|
|
The absolute error of setting the shutter delay
|
10-5
|
|
Temporary instability (jitter) of the EOC trigger,
no more (in another version of the camera, instability of less than 1 ns is
possible due to a deterioration in the absolute error of the shutter delay
value to 5 × 10-2)
|
5
ns
|
|
The voltage on the microchannel plates of the II
T
(set in 1 V
increments)
|
from 400 to 850 V
|
|
Resolution
|
2048×2048
|
|
The ADC bit rate
|
12
bit
|
|
Extension of the saved image file
|
*tiff
|
|
The number of fiber-optic communication lines (fiber
optic lines) for communication with a computer
|
8
|
|
The length of the fiber optic cable
|
from 5 to 300 m
|
|
Overall dimensions (without lens)
|
575×265×295mm
|
|
Power consumption
|
60
W
|
Application of the NANOGATE-22/16 camera in experiments.
All experiments were performed by the staff of the IPHF RAS under the
guidance of leading researcher Dudin S.V. [13,14].
Experiment No. 1. Registration of a detonation converging wave.
Figure 3 – The explosive charge and the process of preparing
the experiment.
Experience preparation.
The detonation converging wave is launched from 24 points evenly spaced around
the circumference of the disk. Numbering of frames from left to right and from
top to bottom. The exposure time of all frames is 20 ns. The intervals between
frames are 1.4 microseconds.
Figure 4 – Results of registration
in the experiment.
In the 8th and
16th frames, the multiple exposure mode is enabled (superimposing multiple IIT
exposures on one frame in the CCD matrix). In the 8th frame, exposures are made
at moments 2, 4, 6 and 8 frames. In the 16th frame, exposures are made at
moments 11, 13, and 15 of the frame. With a set of precision parameters, the
NANOGATE-22/16 camera has the ability to measure the spatiotemporal
characteristics of fast-flowing processes in the nanosecond time domain with an
error of up to 1%. The results of 3x exposure in the 16th frame are shown
below, the times of which coincide with the times of the above 3 frames.
Figure 5 – Construction of the 16 registration frame.
From the analysis of the
images obtained in each of the 16 frames, including those in which the multiple
exposure mode was turned on, it was concluded that in such an experiment, it is
possible to register not 16, but 64 phases (at least) of the detonation
converging wave. To do this, in each of the 16 frames, the 4-fold exposure mode
is turned on with an interval between repeated exposures Trep = 1/64×
Texp, after about 290 ns (the entire recording time was Texp = 18.2
microseconds). Such a number of phases of the detonation converging wave has
made it possible to register a change in the velocity and shape of the
detonation converging wave as it moves from the periphery of the disk to the
center.
Experiment No. 2.
The development of
detonation in a bulk high explosive (HE). During the experiment, the velocity
spread of the detonation wave (DW) in a bulk HE was measured. During the
experiment, the detonation rates from each initiating detonation cord (DC) have
been measured. The information obtained allow us to estimate not only the
average speed of the engine, but also the magnitude of its standard deviation
(SD), which is the most important characteristic of any HE. Additionally, the
effectiveness of using the strobing mode of the NANOGATE 22/16 camera during
experiments of this type has been tested. Due to the fact that in all
experiments the velocity of the detonation wave front at different phases of
the process ranged from 2.5 to 9 km/s, the exposure duration of each of the 16
frames was set to 10 ns. The values of the moment of registration (Δ
i) are indicated from the time of the
explosive pulse. In the seventh frame, the multiple exposure mode is enabled
(the IIT shutter opens 6 times and the integral image from the IIT screen
accumulates in one frame of the CCD matrix). An image of six phases of the
process, four of which are duplicated in other channels to verify the accuracy
of the inter-frame positioning of the
NANOGATE 22/16
camera
as a whole. The multiplicity of the DW images is caused by the use of a
household mirror, which forms parasitic reflections from the glass surface.
Figure 6 – Results of registration in experiment No. 2.
Despite the simultaneous initiation of all DC of equal length, the time
of transmission of detonation to the tested explosive is different. Such a
difference in timing is more or less characteristic of any multipoint
initiation systems due to technological variations in the parameters of
explosives in the DC. Nevertheless, the analysis of the propagation of DW in
the vertical direction makes it possible to measure the vertical velocity of DW
from each initiation point with high accuracy. The average speed of the engine
was 5.630 km/s.
Experiment No. 3.
Testing of a cylindrical implosive device. The annular DW is formed by
the supply HE rods. The symmetry of the converging DW is ensured by the use of
a focusing system (FS). The purpose of the experiment is to work out the FS, to
clarify the parameters of the mathematical model of
explosive kinetics.
Figure 7 – Results of registration in experiment No. 3.
The exposure duration in each frame is 10 ns, the interval between frames
is 1 microsecond. To demonstrate the recording quality at an exposure duration
of 10 ns, Figure 8 shows an enlarged image of the 13th frame separately. Figure
8 – Registration frame No. 13 in experiment No.3. )
Figure 8 – Registration
frame No. 13 in experiment No.3.
Experiment No. 1.
Registration of the propagation of the
detonation wave of the photosensitive explosive composition VS-2[15,16]. Strips
of photosensitive explosive VS-2 measuring 10×80 mm, applied to a
polished aluminum sheet measuring 23x100x0.15 mm, were attached with adhesive
tape to a witness plate with dimensions of 60x300x4 mm (Figure 9).
Figure 9 – The witness plate with the composition of VS-2.
The initiation of the VS-2 composition was carried out using an EVIS-3
gas discharge emitter, remote at a distance of 14 mm. The streamer of the gas
discharge emitter was located at a distance of 10 mm from the edge of the strip
with the composition VS-2. The appearance of the experimental installation is
shown in Figure 10.
Figure 10 – The appearance
of the experimental installation
The exposure duration in
each frame is 20 ns, the interval between frames is 1 microsecond.
|
|
|
|
Frame
¹5 (10 µs)
|
Frame
¹6
(11 µs)
|
|
|
|
|
Frame
¹7 (12 µs)
|
Frame
¹8 (13 µs)
|
|
|
|
|
Frame
¹9 (14 µs)
|
Frame
¹11 (16 µs)
|
|
|
|
|
Frame
12 (17 µs)
|
Frame
13 (18 µs)
|
|
|
|
|
Frame
14 (19 µs)
|
Frame
15 (20 µs)
|
Figure 11 – Fragments of
registration frames in experiment No. 1.
Based on the
data obtained, the dynamics of the movement of the detonation wave front was
estimated. The assessment was carried out at two points: the coordinates of the
maximum (1) and minimum (2) remote part of the detonation wave front relative
to the right edge of the strip with the composition of VS-2. The average
velocity of the detonation wave front in the experiment was 4375 m/s.
Experiment
No.2. Explosive throwing of a
barrier simulator model.
In the experiment, the design of a small-size explosive throwing device was
worked out, the integrity of the barrier simulator model was monitored.
Registration was carried out against the background of a scattering screen
illuminated by explosive light sources. The exposure duration in each frame is
100 ns, the interval between frames is 5 microseconds.
Figure 12 – Fragments of registration frames in
experiment No. 2
According to the obtained motion picture of
the barrier simulator model, the speed of movement of the silhouette boundary
was determined, which amounted to 1900 m/s.
Experiment No. 3.
Optical recording by a high-speed NANOGATE 22/16
camera of the throwing process of an barrier simulator model (BSM) using a
model explosive throwing device (ETD) against the background of a scattering
screen.
Figure 13 – Photo of the working field in experiment No. 3
Figure 14 – Registration frames in experiment No. 3.
The speed of movement of the BSM silhouette boundary was determined using
14 frames with an assumed frame-to-frame interval of 8.75 microseconds
(shooting speed 114270 fps).
Figure 15 is a graph of the
speed change.
The values of
the angle of rotation of the BSM silhouette boundary have been measured. The
measurement results are shown in Table 2.
Table 2 – Measurement results
|
Time, ms
|
The angle of the BSM
silhouette,°
|
|
0,000
|
37,2
|
|
0,009
|
37,2
|
|
0,018
|
37,8
|
|
0,026
|
39,4
|
|
0,035
|
41,2
|
|
0,044
|
41,5
|
|
0,053
|
41,7
|
|
0,061
|
41,7
|
|
0,070
|
41,7
|
|
0,079
|
42,0
|
|
0,088
|
42,7
|
|
0,096
|
42,9
|
|
0,105
|
43,2
|
|
0,114
|
43,5
|
Experiment No.
4. Registration of the nature of detonation transmission through a steel plate
with a thickness of 10 mm (300x200x10 mm) by the electron-optical camera
Nanogate-22/16 on the second charge of the TNT-Hexogen 40/60 mixture (total
weight 0.34 kg). The registration of an electrical signal from the
"CONTROL" output of the Nanogate-22/16 electron-optical camera
determined the image formation times. The assembly included two charges
measuring 100x100x10 mm, separated by a steel plate (glued to it) with a
thickness of 10 mm, in the center of one of which an electric detonator is
installed.
The
appearance of
the installation is shown in Figure 16.
Figure 16 – The appearance of the installation.
Registration
was carried out during the daytime at an ambient temperature of plus 19°C
and an atmospheric pressure of 746 mm Hg.
Figure 17 - The sequence of frames in Experiment No. 4.
A digital
oscilloscope registered a signal from the CONTROL output of Nanogate-22/16.
Cursor measurements determine the frame construction times relative to the
synchro pulse of the explosive installation of the
demolition
set.
The measurement results are shown in Table 4, and the waveform of the
recorded signals is shown in Figure 18. Table 4 – Image construction times. Nanogate-22/16.
Figure 17 – The sequence
of frames in Experiment No. 4.
Table 3 –
Nanogate Settings-22/2
|
Parameter
|
Value
|
|
launch
delay,
 s
|
3
|
|
exposure, ns
|
500
|
|
image size,
pixels
|
1660õ1248
|
|
shooting
speed, frame/s
|
500 000
|
|
focal
length, mm
|
300
|
|
aperture
|
2,8
|
|
IIT voltage,
V
|
600
|
A digital
oscilloscope registered a signal from the CONTROL output of Nanogate-22/16.
Cursor measurements determine the frame construction times relative to the
synchro pulse of the explosive installation of the demolition set. The
measurement results are shown in Table 4, and the waveform of the recorded
signals is shown in Figure 18.
Table 4 – Image
construction times Nanogate-22/16
|
Frame no.
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
|
time
, µ
s
|
3,2
|
5,2
|
7,2
|
9,2
|
11,2
|
13,2
|
15,2
|
17,2
|
|
Frame no.
|
9
|
10
|
11
|
12
|
13
|
14
|
15
|
16
|
|
time
, µ
s
|
19,2
|
21,2
|
23,2
|
25,2
|
27,2
|
29,2
|
31,2
|
33,2
|
Figure 18 – Waveform of the signals recorded in the
experiment
Separately, in Fig.19, the frames are
highlighted after the calculated output of the shock wave to the frontal
surface of the second (passive) HE2 charge (tx = 9.7 microseconds).
|
|
|
|
Ò = 11 µ
s
|
Ò = 15 µ
s
|
|
|
|
|
Ò = 17 µ
s
|
Ò = 19 µ
s
|
Figure 19 - Individual frames of the process.
When the DW
reaches the surface of the passive charge, there is an annular expansion of the
"internal" backlight (by glue), making visible the inscription on the
back surface of the charge (t = 11 µs.). Upon reaching the front of the
luminous zone of the periphery of the charge, a shock wave in the air (t= 19
µs) is formed, and "hot spots" appear in the charge with the growth
towards the center of the charge.
Experiment
No. 5.
Registration by the Nanogate-22/16 electron-optical camera of the fact of
detonation transfer from a TNT-Hexogen 40/60 charge with a size of 100x105x10
mm to a similar charge through a steel plate with a thickness of 20 mm
(300x200x20 mm) (HE charges are glued to it with epoxy resin). Two electric
detonators are installed in the upper part of the active charge HE1. The
appearance of the installation is shown in Figure 20.
Figure 20 – The appearance
of the installation (HE1 on the right, HE2 on the left).
Figure 21
shows individual frames of the detonation transmission process.
|
|
|
|
|
|
The recorded
back surface of the HE2 charge; the estimated time for the release of SW to
the front surface of the HE2 charge = 11,6 µs
|
t=11 µs
|
t=15µs
|
t=17µs
|
|
|
|
|
|
|
t=19µs
|
t=21µs
|
t=23µs
|
t=33µs
|
Figure
21
- Detonation transmission
Figure 22 – Moving the
boundaries of the shock wave front
Figure 23 – Propagation of
the boundaries of the luminous zone
The propagation of the
shock wave front along the adhesive layer through the HE2 charge with a light
transmission coefficient of 0.1 (frame 2-7) was recorded, followed by
detonation excitation in the entire charge (frame 6-16). The displacement of
the anterior and posterior boundaries of the shock wave front propagating in
the adhesive layer is estimated (see frame 2-7 (t=9-15 microseconds). The graph
of movement from time is shown in Figure 22. According to registration frames
6-16, the propagation of the boundaries of the luminous zone in the horizontal
and vertical directions was estimated (Figure 23). Thus, it was shown that with
an increase in the thickness of the steel plate to two thicknesses HE1, the
initiation of HE2 is possible with the interaction of two DW in HE1 (for
example, in the plane between the detonators). The appearance of the plate
after the experiment is shown in Figures 24, 25.
|
|
|
|
à)
|
b)
|
Figure 24 – The
appearance of the steel plate after the experiment: a) from the side of the
main charge b) from the side of the passive (additional) charge).
Figure 25 – Large-scale
rupture of a steel plate
The
developed domestic camera NANOGATE-22/16 has confirmed its characteristics in
the study of fast processes and will be used in measurement techniques for
experiments on a rocket track (on a dynamic loading bench.
This article was prepared with the support of grant RNF ( project Ü 20-19-00613).
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