1. Chamber with Controlled Atmosphere (AIRFLY) Michal Doubrava – CTU Prague Václav Vacek – CTU Prague Libor Nožka, Miroslav Hrabovský, Petr Schovánek, Miroslav Palatka, Miroslav Pech, Dušan Mandát – Joint Laboratory of Optics, Olomouc Martina Boháčová, Jan Řídký – Institute of Physics of Academy of Sciences of the Czech Republic

2. Purpose of Chamber Simulation of Earth atmosphere up to about 30 km above its surface

3. Variables to Handle Operating pressures from 1010 mbar (standard atmosphere) to about 0 mbar Operating temperatures from normal ambient temperature 20 °C to about -50 °C Moisture content of inside atmosphere

4. The First Prototype Cooling performance generated by liquid nitrogen flow through two heat exchangers Regulated flow-rate Robust, heavy construction

5. The First Chamber Problems Chamber started to leak after a few hours of cooling (as cold penetrates through body) Insufficient cooling performance during the last experiment at Van der Graaf accelerator site (too high energy dissipation)

6. The Second Prototype Cooling effect realized by dry ice (CO 2 ), that has melting temperature -79 °C Standard stainless steel vacuum “cross” should secure leak-tightness Temperature controlled through “heating” tape that is wound round the cylindrical surfaces Other equipment (PMT`s, etc.) is placed in nitrogen atmosphere to prevent the condensation of air moisture on it

7. Overview Placement of “heating” tape

8. Initial Tests May 2006, Prague Two runs, each with 5 kg of dry ice Packing of dry ice lasts more than 5 hours The first run with dry ice only The second run with implemented “heating” tape (up to 25 W)

9. The First Tests Overview

10. Temperature Profile

11. Further Steps, Improvements More tests should be performed in order to learn the behavior of the chamber and to discover possible imperfections of this design Difficult to estimate the behavior of chamber when installed on a beam line Installation of additional circuit with liquid nitrogen (tube heat exchanger) could assure the cooling power N 2 flush line recommended – to reduce condensation of moisture on the dry ice crystals

12. N 2 Flush Line Should prevent the air moisture condensation that disables dry ice crystals movement Unmovable crystals create the air-gap around chamber that decreases the cooling performance

13. Summary Two different prototypes available so far The first one worked relatively normally in Frascati, so can be used there again (if leakage problem is solved) if necessary The second prototype could be acceptable for measurements in States (AWA, Van der Graaf) but needs more testing before its final usage