Abstract
Abstract. The SPectrometer for Ice Nuclei (SPIN) has been modified to access ice nucleation at low temperatures. The modification consists of a reconfiguration of components from SPIN's cooling system to provide refrigerant with a low boiling point to the chamber. We describe the setup modification and determine the temperature and humidity range accessible to experiments. The modification extends the measurement range of SPIN to 208 K, which enables measurements in the temperature regime relevant for ice formation in cirrus clouds. This addition of low-temperature capability allows for far more comprehensive measurements of the temperature- and humidity-dependent ice nucleation of test substances, to investigate fundamentals of ice nucleation mechanisms. We present exemplary data of heterogeneous ice nucleation on silver iodide and homogeneous ice nucleation in solution droplets to demonstrate the usefulness of the modified SPIN setup for precision measurements to detect discrepancies between experiments and widely used theories.
Highlights
The fundamental understanding of atmospheric ice formation is a complex problem that has been under investigation for almost a century (Findeisen, 1938)
We describe a mechanically uncomplicated way to modify the cooling system of the SPectrometer for Ice Nuclei (SPIN) instrument to expand its T and relative humidity (RH) range in which experiments can be performed
SPIN is a parallel-plate continuous flow diffusion chamber (CFDC) manufactured by Droplet Measurement Technologies (DMT)
Summary
The fundamental understanding of atmospheric ice formation is a complex problem that has been under investigation for almost a century (Findeisen, 1938). Part of the complexity of studying ice nucleation experimentally arises from different mechanisms that initiate ice formation at different temperatures and humidities. We describe a mechanically uncomplicated way to modify the cooling system of the SPectrometer for Ice Nuclei (SPIN) instrument to expand its T and RH range in which experiments can be performed. SPIN is a parallel-plate CFDC manufactured by Droplet Measurement Technologies (DMT). It follows the working principle discussed in Rogers (1988) with the parallel-plate design from Stetzer et al (2008). We describe how experimental conditions (T , RH) are generated by controlling the wall plate temperatures and how much the limits of achievable experimental conditions are extended by modifying the cooling system
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