Temperature Control in DC Spark System II

Anders Korsbäck

Context

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Introducing sample temperature control into DC Spark System II makes several

interesting measurements possible

Direct effect of temperature on breakdown rate

In-situ annealing of samples

Temperature control was originally attempted in 2011-2012 but abandoned

Lack of gap distance control to compensate for thermal expansion

Temperature controller was damaged and broken in lab mishap

Installation of liquid nitrogen line in lab was delayed

Time was running out for people, other things got priority

Controller has now been repaired and put together after many trials and even

more errors (thanks to Kyrre for helping out!)

Overview of controller

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Sample heating is carried out by electron bombardment of a plate in thermal (but not electrical – our

modification) contact with sample

Filament is heated ohmically, thermally emitted electrons are accelerated by 650 V potential to hit heater

anode and deposit their kinetic energy into it

EBHC runs feedback control, using thermocouple reading as input signal and regulating the filament

voltage and current

Nominal temperature range -180 °C to +1000 °C (+1200 °C without cooling)