Teledyne ProEM Series, System Manual

Page: 20 / 162

20 ProEM System Manual Issue 3
2.2.1.1 EMCCD Technology and On-Chip Multiplication Gain
The principal difference between an electron-multiplying CCD (EMCCD) and a
traditional CCD is the presence of an extended serial register in the new device. See
Figure 2-3 .
Figure 2-3: EMCCD Array Structure Comparison: Frame Transfer, Kinetics, Full Frame
Electrons are accelerated from pixel to pixel in the extended portion of the serial
register (also referred to as a multiplication register) by applying higher-than-typical
CCD clock voltages. This causes secondary electrons to be generated in the silicon by
impact ionization. The degree of multiplication gain is controlled by increasing or
decreasing the clock voltages for this register (gain is exponentially proportional to the
voltage). Although the probability of generating secondary electrons is fairly low
(typically 0.01 per stage), over the large number of stages of a typical multiplication
register, the total gain can be quite high.
This technology combines the ease of use and robustness of a traditional CCD with the
gain capabilities of an intensified CCD in a single device. The combination of this
technology with frame-transfer readout makes the ProEM cameras excellent choices
for experiments where fast framing and low light sensitivity are required.
NOTE:
As the on-chip multiplication introduces additional noise, it
is recommended that the multiplication be used only as
required. For more information, refer to the
On-Chip
Multiplication Gain technical note. This technical note can
be accessed by going to the Teledyne Princeton
Instruments web site:
www.princetoninstruments.com
.
2.2.2 Cooling
Dark current is reduced in ProEM camera systems through thermoelectric cooling of
the CCD arrays. Cooling by this method uses a Peltier cooler in combination with
air-circulation (i.e., fan,) and/or circulating coolant. To prevent condensation and
contamination from occurring, cameras cooled this way are evacuated. Due to CCD
size/packaging differences, the lowest achievable temperature can vary from one
ProEM model to the next. refer to the specific system's data sheet for cooling
performance.
Frame-transfer Area
Sensor Area
ProEM:512BK EMCCD
Sensor Area
Masked Area
Sensor Area
ProEM:1600
2
B/1600
4
B EMCCD ProEM:512B/1024B EMCCD
Low Noise
For standard, high dynamic
range applications
Multiplication Gain
For high speed, low
light level applications applications
Readout
Amplifier
Output or Sensor Node
Output or Sensor Node
Extended Multiplication Register
d Serial Register
Frame-transfer Area
Sensor Area
High Voltage Clock
Readout
Amplifier
Normal Voltage Clock
Standar
4
4
11
-0
126
_
000
3