The SARG Exo - Planets Search: the SARG iodine cell 

The SARG cell, made of quartz, has a path length of 50 mm with a thin tube on its center to allow filling of the cell. 

The iodine filling was performed following the procedure described by Marcy and Butler (1992, PASP, 104,270), fixing the sublimation temperature at 46 C. In order to avoid dameges to the thin tube, vulnerable against thermal shocks, the cell is hosted by an highly conductive case. The cell is kept at its working temperature (61 C) by a thermal control device (three thermofoils). 

The cell location  is in the preslit sub - unit of the spectrograph, between the SARG derotator and the L3 lens (that focalize light onto the slit), approximatively in the middle of the collimated part of the light path. 

To prevent large thermal losses toward the spectrograph (thermalized at 20 degrees), SARG cell is designed with a double window system and provided with a thick insulating layer. The SARG iodine cell was designed by S. Desidera, filled by G. Favero (Padua Chemistry Dep., see Photo). The mechanical componets were made by A. Calì (Catania Astrophysical Observatory) and cabling by G. Farisato (Padua Astronomical Observatory). For details see: Desidera S., 2000, Search for Extrasolar Planets Using the SARG Iodine Cell, PhD Thesis, University of Padua.