v10308u Hamamatsu Photonics, K.K.,, v10308u Datasheet - Page 7

• Manufacturer Part Number: v10308u
• Description: Image Intensifiers
• Manufacturer: Hamamatsu Photonics, K.K.,

Figure 4: Typical Transmittance of Window Materials
A photocathode converts light into electrons. This conversion efficiency
depends on the wavelength of light. The relationship between this
conversion efficiency (photocathode radiant sensitivity or quantum
efficiency) and wavelength is called the spectral response
characteristic. (See spectral response characteristics on page 2.)
An MCP is a secondary electron multiplier consisting of an array of
millions of very thin glass channels (glass pipes) bundled in parallel
and sliced in the form of a disk. Each channel works as an
independent electron multiplier. When an electron enters a channel
and hits the inner wall, secondary electrons are produced. These
secondary electrons are then accelerated by the voltage (V
applied across the both ends of the MCP along their parabolic
trajectories to strike the opposite wall where additional secondary
electrons are released. This process is repeated many times along the
channel wall and as a result, a great number of electrons are output
from the MCP.
The dynamic range (linearity) of an image intensifier depends on the
so-called strip current which flows through the MCP during operation.
When a higher linearity is required, using a low-resistance MCP is
recommended so that a large strip current will flow through the MCP.
The channel diameter of typical MCPs is 10 µm. High resolution type
MCPs, however, use a 6 µm channel diameter.
MCP Structure and Operation
The phosphor screen generally absorbs ultraviolet radiation, electron
beams or X-rays and emits light on a wavelength characteristic of that
material. An image intensifier uses a phosphor screen at the output
surface to convert the electrons multiplied by the MCP into light.
Phosphor screen decay time is one of the most important factors to
100
10
1
100
TII B0099EB
MCP (MICROCHANNEL PLATE)
120
MgF
PHOSPHOR SCREEN
2
PHOTOCATHODE
INPUT WINDOWS
INPUT ELECTRODE
160
CHANNEL
BOROSILLICATE
GLASS
SYNTHETIC
SILICA
WAVELENGTH (nm)
INPUT
ELECTRON
200
240
STRIP CURRENT
300
V D
CHANNEL WALL
* Collimated transmission
400
FIBER *
OPTIC
PLATE
OUTPUT
ELECTRODE
OUTPUT
ELECTRONS
TMCPC0002EC
500
MCP
)
consider when selecting a phosphor screen type. When used with a
high-speed CCD or linear image sensor, a phosphor screen with a
short decay time is recommended so that no afterimage remains in the
next frame. For nighttime viewing and surveillance, a phosphor with a
long decay time is suggested to minimize flicker. Figure 5 shows
typical phosphor spectral emission characteristics and Figure 6 shows
typical decay characteristics.
We also supply phosphor screens singly for use in detection of
ultraviolet radiation, electron beams and X-rays.
Figure 6: Typical Decay Characteristics
Please select the desired type according to the readout method.
Most photocathodes have a high electrical resistance (surface
resistance) and are not suited for gate operation when used separately.
To allow gate operation at a photocathode, a low-resistance
photocathode electrode (metallic thin film) is usually deposited
between the photocathode and the incident window. Gate operation
can be performed by applying a high-speed voltage pulse to the low-
resistance photocathode electrode. Metallic thick films or mesh type
electrodes are provided rather than metallic thin films since they offer
an even lower surface resistance. The gate operation time is
determined by the type of photocathode electrode.
Since the semiconductor crystals of the GaAs and GaAsP
photocathodes themselves have low resistance, no photocathode
electrode film needs to be deposited for gate operation.
Figure 5: Typical Phosphor Spectral Emission Characteristics
* Decay time obtained following to the continuous input light removal.
100
10
10
10
10
10
OUTPUT WINDOW MATERIAL
60
20
80
40
-1
-2
0
350
10
2
1
0
TII B0079EE
TII B0078EE
-8
SCREEN PEAK CURRENT 8 nA/cm
P47
400
P47
GATE OPERATION
10
100 ns
-7
P24
1 ms
450
WAVELENGTH (nm)
10
DECAY TIME (s)
P46
-6
100 ns
500
10
P24
1 ms
-5
550
100 ns
10
2
600
-4
EYE
RESPONSE
INPUT LIGHT
PULSE WIDTH
P43
10
650
P43DC*
1 ms
-3
P46
700
10
-2
6