SEIX 17-20 octobre 2005 - Atelier Calcium

UNE NOUVELLE CAMÉRA PAR HAMAMATSU : ELECTRON MULTIPLYING
CCD C9100 HIGH SPEED WITH LOW LIGHT LEVELS
Bruno Combettes
Hamamatsu Photonics France rue du saule trapu, parc du moulin de Massy, BP 229 91882
MASSY Cedex
• Sensor is designed based on the frame transfer back thinned CCD technology.
• Multiplication register is added on the serial register.
• In the multiplication register, up to 50 volts is applied to the one of charge transfer
gate (GS) in order to get the multiplication gain.
• Electrical field under the transfer gate (GS) accelerates the signal electron and
energetic collision occurs in the silicon matrix.
• Such collision will result in an occasional extra electron in the transferred charge.
• This is called IMPACT IONIZATION
• Every stage in the multiplication register has a statistical chance of 1.0% to 1.6% of
creating an impact ionization event.
• When multiplied by 500 steps ,for example, this generates several thousand times
“gain”.
• Mathematically gain is given by G=(1+g)N
– where N is the stage number in the multiplication register and g is the
probability of generating a secondary electron.
– For example, N is 500 and g is 1.5%(0.015), then G is 1710.
• The normal read noise of a camera becomes “relatively” very small compared to this.
• High speed readout at low intensity with low “relative read noise” is the main
advantage of this technology.
• Advantage
– Readout noise is constant and fixed.
– Gain is controllable.
– When signal is gained up bigger than Readout noise, then it relatively readout
noise becomes less than 1 electron.
Cooling is the most important technology for EM-CCD.
• Why?
– Dark current is the part of signal.
– At high gain, dark current becomes a main source of back ground noise.
– EM Gain is the function of temperature. Need -50 degree C cooling to get
2000 times gain.
– Sensor gain is strongly affected by the sensor temperature and it must be very
stable against ambient temperature movement.
– Only very stable sensor temperature realizes the quantitative measurement.
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