For high precision analytical techniques with an integrated pyrolysis step, spatial and temporal temperature consistency inside the pyrolysis reactor is a crucial characteristic for high quality measurements.

In the daily laboratory routine, the durability of the furnace and its heating tube, respectively, is not only an important issue from the cost perspective. The exchange of the furnace, the heating tube and elements passed through, respectively, interrupts the measuring routine and each time requires a time-consuming start-up of the system.

Context: system optimization at the AWI for highest demands

In the context of climate research, the Alfred Wegener Institute for Polar and Marine Research is decisively involved into retrieval and analysis of ice cores. For the comprehension of the historical development of the atmosphere’s gas composition, gas inclusions of ice core segments with an age of up to 800.000 years are extracted and analyzed. These ice cores are intersected on the ice shields of the Antarctic and Greenland with high logistical efforts and under extreme conditions. Segmentation of an ice core

Accordingly, there exist highest demands in respect to reliability and precision of the used laboratory analytics. The correct reconstruction of the isotope composition of greenhouse gases like the hydrogen isotopy of methane requires constant measuring conditions. In particular, the minimal sample quantities available make it indispensable to have a very high stability of the pyrolysis conditions.

Constructive improvements

Technical details had been developed at the AWI which considerably increase temperature constancy as well as the durability of the parts of the high temperature tube furnace.

• The furnace has a ceramic three point bearing at the front and rear face of the sinter heating tube (e.g. SiC). This can be precisely adjusted in order to compensate for thermal deformation and to allow for the use of heating tubes of different diameters. Touchings of the heating tube with other parts of the furnace (insulation, ceramic reactor) causing temperature hot spots are effectively avoided which increases the durability of the oven considerably.

• Furthermore, the ceramic reactor (e.g. a two hole ceramic tube containing the pyrolysis capillary and the temperature sensor) can be exactly centered along the furnace’s longitudinal axis by special mounting brackets. The concentric air gap between reactor and heating tube precludes hot spots and guaranties for well defined temperature conditions inside the reactor.

• The oven has an intelligent temperature control on the basis of a pulsed current with amplitude regulation which continuously compensates for the change in resistivity of the SiC heating element caused by aging. This allows for an undisturbed operation over the entire lifespan of the sintered heating tube.