Ultra-low vibration closed-cycle cryostat for X-ray applications

Low temperature sample environment is required for the next generation X-ray sources with a sub-micron beam size. The success of the full potential employment of small coherent X-ray beams will highly depend on the position control of the sample relative to the beam and the ability of sample stabilization. The cryostats currently in use are heavy, cumbersome and can only be used at facilities where diffractometers with a through- hole on a phi stage or with an offset chi circle are installed. Many X-ray diffraction facilities utilizing high brightness synchrotron beamlines employ modern diffractometers for specifically designed sample stages which cannot fit cryostats currently available on the market. An ultra-low vibration system based on a flexible coupling principle will allow us to obtain the required nm level of vibrations. The cryostat will incorporate the ability to manipulate the sample with an integrated multi-axis stage that will allow the sample precise positioning relative to the X-ray beam. A high degree of X-ray access will be also provided. The integration of flexible cooling lines will add a superior freedom in positioning the cryocooler relative to the sample chamber mounted on a goniometer. Phase I of the project will be devoted to the cryostat engineering design development and vibration measurements of a mock-up first generation cryostat. It is necessarily to mechanically decouple the cryostat from different sources such as vacuum pumping system, cryocooler, the cryostat mounting table and sometimes from acoustic vibrations. The first generation of the cryostat will be manufactured to make vibration measurement with Michelson interferometer. The cryostat will be cooled by a closed cycle Gifford-McMahon (GM) cryocooler. Vibration mitigation studies will be conducted. The experimental results will be used for the development of a full-featured cryostat in Phase I. The compact cryostat proposed in this SBIR project will be specifically designed for X-ray applications. It will be significantly more compact than current cryostats used for X-ray diffraction at modern high-brightness synchrotrons. The cryostat proposed here will have a compact sample chamber suitable for modern goniometers which will open up new possibilities for diffraction measurements of samples at cryogenic temperatures. The cryostat will be based on a closed cycle cryocooler that does not require liquid helium to operate, resulting in savings of up to hundreds of thousands of dollars per year. The cryostat will provide a nm level of vibrations of the sample holder which is so critical for modern synchrotron facilities.