Center of Cryogenic Metrology's (CCM) calibration is base on the ITS-90. The calibration range in CCM is from 0.65K to room temperature. The ITS-90 is maintained on a set of SPRTs and RIRTs, these standard thermometers were intercompared with standard thermometers of other national measurement laboratories, such as INGC in Italy, NMI in Netherland, NMI in Australia, NPL in Britain and NIM in China. The best accuracy of CCM calibration is 3 mK for RIRT and 5 mK for SPRT respectively, the worst uncertainty of calibration is 0.1K for industrial sensors. The temperature standards maintained at the CCM are authorized by the China State Bureau of quality and technical supervision to provide calibration service all around China.
The measurement standards in CCM have been examined and deemed to be qualified to carry out metrological verification, calibration and test over China. We have developed quality management systems to promote the need to meet the customer, regulatory, statutory requirements.
Calibration services for cryogenic temperature sensors.
The pure metal superconducting fix point apparatus of NIST and gas triple point bottle of INGC (Italy) have been introduced to develop the 3He thermostat and establish the cryogenic measurement standard apparatus. Meanwhile, standard rhodium-iron resistance thermometer and standard platinum resistance thermometer for cryogenic temperature have been introduced from NPL to compose the group of standard resistance thermometers of CCM to maintain the ITS-90.
Study on cryogenic temperature sensors
With cryogenic thermometer measurement device, we have carried out investigations on temperature measurement technology and performance tests of several types of cryogenic thermometers. Cooperated with other institution, we have produced miniature metal shell rhodium-iron resistance thermometer and extended the temperature range of miniature ceramic framework platinum resistance thermometer to 20K, which has been widely applied in cryogenic engineering and cryogenic physics.
The reproducing of 4He λ point
The innovative reproducing technology of 4He λ point has been proposed in CCM and acquired the patent with the advice of academician Hong Chaosheng. It indicated by the experimental data that with this technology a transition temperature with temperature fluctuation less than 3μK can be obtained. This result will bring forward the time that a sealed lambda cell can be recognized as a fixed point device of the first quality.
The CCM provides services to domestic institutes and universities for temperature measurement and test, which cover fields like cryogenic physics, high-temperature superconduction, cryogenic engineering and spaceflight engineering. CCM has been the specified temperature measurement and test laboratory for quality system certification.
The CCM has cooperated with the main foreign national temperature measurement and test laboratories such as INGC (Italy), NML (Australia) and INM (Netherland). With the intercommunication and collaboration especially the international comparison of the standard cryogenic resistance thermometer, the CCM preserves the temperature standard comparable to the INGC. The comparing results validate the consistency of the temperature standard of CCM with the INGC and the measuring data of the CCM.
Besides the service of temperature measurement and test, CCM also participated in the spaceflight cryogenic tests. In 1996, we completed the cryogenic pressure-bearing and cryogenic seal tests of the sub-controlling valves of the rocket engine. We also designed and built the specified cryogenic thermostat to create the cryogenic, high pressure and vacuum condition, with which we provided a great deal of data for Long March Ⅲ rocket. In 1998, we succeeded in an experimental setup to test the seal performance of the flange with large diameter in the condition of cryogenic temperature (20K), high pressure (24MPa) and high vacuum (10-3Pa). And in 2003, we began to research on and set up the testing apparatus of the cryogenic thermal properties for the thermal insulation materials, which gave direct guidance for the structure design and the selection of thermal insulation material of the cryogenic fuel reservoir for the new type carrier rocket., we finished the verification regulation of Ni-Cr/Au+0.07at.%Fe thermocouple in 2003 and the calibration specification for cryogenic resistance thermometers with negative sensitivity in 2004.