A NEW SAMPLE CHAMBER WITH TEMPERATURE AND HUMIDITY CONTROL FOR LIPID AND FIBER S

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Many x-ray experiments studying lipids, lipid-protein interactions and biological fibers require the ability to accurately monitor and control the temperature and hydration state of the specimen. In these experiments the measurements need to be done under a variety of different temperature/hydration conditions. On BL4-2 the typical exposure time for one measurement ranges from a few seconds to at most a few minutes, thus in order to make efficient use of the experimental time, the control of the sample environment should not only be accurate but also be reasonably fast. A new sample chamber has been designed to meet these requirements, incorporating Peltier elements together with PID control electronics, and allows us to quickly change and reliably control the temperature and humidity conditions inside the sealed chamber. The chamber is mounted on a standard goniometer head, which is usually held by a Huber goniostat mounted on the standard motorized sample stage at BL4-2. With this we can easily change the tilt angle of the sample with respect to the beam during the experiment which is necessary for experiments on aligned samples supported on a flat substrate. A PC is used to communicate with the control electronics through a serial port (RS232) and all the control parameters can be set remotely. This serial port communication will allow us in near future to integrate the chamber control into the DCS/Blu-Ice beam line software.