Specifications

Version 1.1 rev Jan 2013
Page 48
iXon Ultra
, Features and Functionality
3.2 - COOLING
The EMCCD sensor is cooled using a Thermoelectric (TE) cooler. TE coolers are small, electrically powered devices
with no moving parts, making them reliable and convenient. A TE cooler is actually a heat pump, i.e. it achieves a
temperature difference by transferring heat from its “cold side” (the EMCCD sensor) to its “hot side” (the built-in heat
sink). Therefore, the minimum absolute operating temperature of the EMCCD depends on the temperature of the heat
sink. Andor’s state-of-the-art Ultravac
TM
design allows minimum cooling temperature performance unrivalled by other
manufacturers. The maximum temperature difference that the iXon Ultra TE device can attain is dependent on the
following two factors:
• Heatgeneratedinthesensorwillvarywithreadoutmode
• TE-cooler“hotside”Temperature
For very 7 degrees cooling, dark current approximately halves. However, for a given temperature the actual dark current
can vary by more than an order of magnitude from device to device. Cameras are specied in terms of the minimum
dark current achievable, rather than minimum temperature.
3.2.1 - Cooling options
The heat that builds up on the heat sink must be removed and this can be achieved in one of the two following ways:
1. Air cooling: a small built-in fan forces air over the heat sink
2. Water cooling: external water is circulated through the heat sink using the water connectors on the head and
this can take one of the following forms:
 •Recirculation
 •Chilling
All Andor iXon Ultra systems support both cooling options. Irrespective of which method is being employed, it is
not desirable for the operating temperature of the EMCCD simply to be dependent on, or vary with, the heat sink
temperature. Therefore, a temperature sensor on the EMCCD (combined with a feedback circuit that controls the
operating current of the cooler) allows stabilization of the EMCCD to any desired temperature within the cooler operating
range.
3.2.2 - Heat generated in the EMCCD
The primary source of heat generated in the iXon Ultra EMCCD is from the Vertical Clocks. These can be either the
‘storage’ or ‘image’ clocks, and are used to transfer charges in the EMCCD vertically, down to the ‘shift register’ to be
amplied and digitized. Increasing the horizontal readout rate from 10 MHz to 17 MHz has no impact on these, however
the reduced time performing horizontal readout means that a higher proportion of a readout cycle is spent using vertical
shifts i.e. more heat generated in the sensor per unit time.
Boosting the amplitude of the vertical clocks will generate the most heat, however any mode which increases the
number of vertical clocks per unit time may also impact cooling. Readout settings which may affect minimum cooling
are:
• verticalshiftspeed
• verticalbinninge.g.regionofinterestorFullVerticalBinning(FVB)
Moving from Full Image readout to FVB will reduce minimum achievable EMCCD temperature by approximately 10°C.