New-generation Instruments Deserve Ultrafast Cryostas
E. Bourgeat-Lami, J. Gonthier, J.-P. Gonzales, F. Lapeyre, E. Lelièvre-Berna, O. Losserand, Y. Memphis, P. Mendes, X. Tonon, S. Turc
Institut Laue Langevin, 71 Avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France
The performance of the new-generation instruments are impressive, to a point where the time required to change the sample temperature leads to unacceptable beam-time losses. The user request is strong: we must boost the performance of the cryostats to enhance the scientific output — without compromising the temperature stability and range.
In a first approach, we proposed to replace the bottom of the existing calorimeters with a copper ring integrating a liquid nitrogen precool loop and a Thermocoax heater which we proposed to call CryoBooster. When cooling the sample down, liquid nitrogen is injected into the base of the calorimeter until the regulation temperature reaches about 80K. When heating the sample, the Thermocoax brings heat in concert with the heater of the exchanger and the temperature raises more rapidly. A gain factor of 3 was reached but the prototype remained too fragile and complex to be used at a user facility.
We tested another and much simpler solution: to enhance the efficiency of the heat exchanger. Indeed, calculations show that only 20% of the enthalpy is exploited in existing systems. We present the performances of two modified top-loading Orange cryostats. The time required to change the temperature, up and down, is decreased by a factor 3. This is 6 times better than any dry system providing the same sample bore.