Commissariat à l'Energie Atomique (EuTuCHe@CEA)
| Organisation: | Commissariat à l'Energie Atomique |
|---|---|
| Location: | Grenoble, France |
| Website: | http://www-drfmc.cea.fr/sbt | http://www.eutuche.eu/cea |
| Contact: | Alain Girard |
This infrastructure is made of two installations: TSF and TSF-f, both working with super fluid and normal helium, which are complementary and will open independently for external users.
Specifications
- very High Reynolds ( up to 2 107 so far) He flow production
- high flexibility of flow conditions, due to the large variation of helium properties over the temperature range available (2.2 K to 5 K)
- both super fluid and normal grid turbulence measurements possible in the same experiment, with adjustable fraction of the super fluid component (from 1.6 to 2.2 K)
- micron- and sub-micron size hot-wire anemometer, second sound probes for super fluid turbulence measurement, miniature pressure sensors
- two complementary facilities working with both normal and super fluid helium, one offering high flexibility, the other unsurpassed performance in terms of helium mass flow rate
EuTuCHe@CEA makes particularly use of the phase transition experienced by Helium at 2.2 K, thus allowing to make experiments at very High Reynolds values with normal (above 2.2 K) and super fluid helium (below 2.2 K). It will contribute to the understanding of the fundamental differences between frictionless and normal turbulence.
CEA-SBT in Grenoble has a world-wide recognized expertise in cryogenic engineering. CEA/SBT had built a He refrigerator providing a large refrigeration power over a temperature range of 1.5 to 5 K, for both applied and fundamental studies, in the domain of helium cooling of superconducting magnets for fusion, and also in the domain of super fluid helium cooling of accelerators (LHC project). More fundamental studies of two phase super fluid helium flows have also been performed, and more recently a turbulence experiment has been set up and funded under the French National Agency for Research, to study some specificities of superfluid turbulence. This project has been made possible by the unique conjunction of a multidisciplinary expertise at CEA and in the geographical area around Grenoble:
- The LEGI (Laboratoire des Ecoulements Géophysiques et Industriels) has a strong theoretical and experimental expertise in fundamental turbulence, usually at room temperature
- The CNRS/Institut Neel has always been a pioneer in cryogenic turbulence, in the domain of turbulent convection, turbulent jet generation and super fluid turbulence
- CEA/SBT expertise in large refrigerators
- And theoretical expertise at CEA/Saclay and ENSLyon
This unique environment has been made possible the construction at CEA of a large facility for helium turbulence study, using the large refrigerator available at CEA, together with the expertise in the field of instrumentation of the above mentioned laboratories. Now, CEA is ready to open this facility to external users. Two facilities are made available by CEA: the main facility is the TSF facility.
The TSF facility
The TSF facility enables to work in super fluid as well as in normal liquid helium. This is a large cryostat connected to the 400 Watt/1.8K refrigerator providing Re in the 107 range.
The 400W/1.8K Refrigerator is in operation since 2004, when it achieved its nominal performances, namely 400W at 1.8K. The refrigeration power available ranks from 120W at 1.5K to 800W at 4.5K. All the temperature levels in between have been fully explored, and temperature can be adjusted in the range of 1.5 to 4.5 K continuously. Noisy screw compressors are located in a separate building, while the cold box stays in the main hall at the vicinity of the 26 m2 control room. Compared to the refrigerators available at CERN in the EuTuCHe@CERN, it offers the possibility to operate below the super fluid transition, down to 1.6K.
Reynolds numbers of up to Re ~ 2x107 have been obtained on the test line in the 1.5 m long 30 mm inner diameter pipe with a mean flow velocity of 8 m/s. Stability better than 0.05K has been maintained over more than one hour. The Rλ achieved with the grid used in earlier experiments was about 400. The test line is presented below: it is equipped with hotwire anemometer, second sound vortex probe, acoustic scattering vorticity sensors and miniature pressure transducer. This line is today inserted at one end of the cold box of the refrigerator. The potential user can perform modifications to this line, and bring a new grid for example, or new sensors, for testing different turbulence properties.
In a very near future (mid 2009), the facility will be upgraded to bring more flexibility: A new cryostat will be installed, of larger dimensions and totally independent of the refrigerator. The space available in this upgraded TSF cryostat will roughly fit in a cylinder of 4m in height and 2 m in inner diameter. Lines providing liquid helium (normal or super fluid) and return pumping line and connections to cryogenic circulating pump are located at the bottom of this virtual cylinder, ensuring easy access for assembly of experimental inserts. An additional 20.000 litres of liquid helium reservoir can be used during transient to boost the performances. This cryostat is presented above, with its connection to the refrigerator.
Measurements available
The line is basically equipped with the detectors mentioned above, together with the electronics. Sensors dedicated to helium flow characterization are very small, which puts a heavy constraint on the mechanical and robustness aspects: all helium facilities will certainly take a great benefit from the results obtained in the JRAs to improve the sensors under cryogenic conditions. Users wishing to install new types of sensors in the TSF facility will need to test these sensors under similar cryogenic conditions before inserting their sensor in the TSF facility, which requires validation of the sensor before it is inserted in the extreme flow conditions in the test line. The second facility - the TSF-f (for TSF flexible) facility may help them to quickly validate these sensors.
The TSF-f facility
The TSF-f facility is a dedicated cryostat working exactly in the same conditions as the TSF facility; only the size of the line and the mass flow rates are different: it is therefore a very reliable test bench for helium sensors. Such a facility is today available at the CNRS/Institut Neel, but it is not very convenient for access to external users. Therefore a new cryostat is under study at CEA, and it will be available beginning of 2009. This smaller and flexible liquid helium cryostat will be used to achieve smaller scale experiments, but with high Reynolds numbers. Due to its flexibility, it can be used to develop and calibrate the instrumentation for further use in the TSF facility, or in any cryogenic facility. It will be equipped to work both in normal sub-cooled liquid helium or in sub-cooled super fluid. If needed, a small removable circulating pump will enable flow to test some sensors.
