119
Thermo Fisher Scientific
Operation Manual HM550
Theory of operation
Specimen and chamber cooling, defrosting
Chapter 4
Theory of operation
e chamber, the microtome and the specimen head are cooled by a
refrigeration machine.
In the rear area of the microtome chamber is an evaporator which the
cold coolant flows through as well as through the specimen head. Due
to the heat extraction from the microtome chamber a cooling down of
the microtome and/or cryo chamber to -35°C can be achieved.
e temperature of the microtome and/or chamber can be adjusted
continuously down to -35°C. For this, pre-select the desired tempera-
ture as set value on the control panel. e actual value is constantly
measured and sent to the control unit.
By means of an installed thermo-electrical element, controlled tempera-
tures down to -50°C can be achieved on the specimen head.
On the left side of the microtome chamber, there are freezing stations
(fast freezing stations) which can be cooled down to a temperature of
-35°C depending on the cryo chamber temperature. is fast freezing
station has 12 positions for one chuck each. e instrument can option-
ally be equipped with an active deep freezing device.
e station can be cooled down to -60°C by means of a Peltier cooling
element. is Peltier cooling element has four positions for one chuck
each. e eight positions correspond to the conventional fast freezing
stations.
e specimen temperature control serves for a more efficient working
with the cryostat. For various specimens, different cutting temperatures
can be achieved very quickly.
After having cut, the specimen can be detached quickly from the chuck
by using the function detach. Another possibility to detach the speci-
men is to warm it up outside the chamber.
e specimen temperature control is supplied via a secondary cooling
circuit. e coolant flows through the cooling head serving as an evapo-
rator of the system and cools it in combination with a Peltier element.
A thermo-electrical element is coupled with the evaporator housing on
the specimen head. Via a set value input for the specimen head on the
control panel, the electronics control the thermo-electrical element at
any desired temperature b10°C and -50°C.
Specimen and
chamber cooling,
defrosting
