Method of regulating the temperature of an element cooled by a cryorefrigerator with periodic operation

1. A method of regulating the temperature of an element ( 10 ) cooled by a cryorefrigerator ( 2 ) with periodic operation, the method being characterized in that it comprises the following steps:

a) measuring at least the periodic time variation of the temperature T of the element ( 10 ), this variation serving to obtain a temperature signal representative of the periodic operation of the cryorefrigerator ( 2 );

b) constructing an “equivalent” periodic heat flux signal (S φeq , S* φeq ) as a function of the temperature signal obtained in step a);

c) constructing a heat flux control signal (S W ) depending on the equivalent heat flux signal constructed in step b), said heat flux control signal (S W ) also serving, by return, in the construction of the equivalent heat flux signal (S φeq , S* φeq ) during step b); and

d) injecting a heat flux (W) into the element ( 10 ) on the basis of the heat flux signal (S W ) constructed in step c), in order to compensate for the measured periodic variations in the temperature T of the element.

2. A method according to claim 1 , wherein the heat flux control signal (S W ) also depends on a control signal (S C ) for improving the compensation of the periodic variations in the temperature of the element at low frequencies.

3. A method according to claim 2 , wherein the heat flux (W) injected into the element in step c) depends on the difference between the control signal (S C ) and the equivalent heat flux signal (S φeq , S* φeq ) constructed in step b) in order to limit the heat power injected into the element that is needed for compensating periodic variations of its temperature.

4. A method according to claim 1 , wherein step b) also comprises an additional step consisting in delaying the previously constructed equivalent heat flux signal (S φeq ) relative to the phase of the temperature signal determined in step a).

5. A method according to claim 4 , wherein a step is provided that consists in estimating the value of the time delay.

6. A method according to claim 5 , wherein the estimation of the time delay comprises the following steps:

b 1 ) injecting an identification signal for identifying the time delay in a thermal system ( 100 ′) comprising the element for which it is desired to regulate the temperature, and a device ( 100 ) for performing the method, the identification signal presenting a waveform and a frequency close to those of the signal representative of the operation of the cryorefrigerator;

b 2 ) determining the phase shift φ of the identification signal at the output from the thermal system, this phase shift being associated with the time delay that is to be estimated;

b 3 ) calculating the phase shift φ 0 of this identification signal with a model representing the thermal behavior of the thermal system ( 100 ′) in the absence of any delay;

b 4 ) calculating the phase shift φ r associated with the time delay using the following relationship:

φ r =φ−φ 0

b 5 ) estimating the time delay at least on the basis of the phase shift φ r calculated in step b 4 ) and of the frequency of the identification signal, said delay being used for delaying the equivalent heat flux signal.

7. A device for performing the method according to claim 1 for regulating the temperature of an element ( 10 ) cooled by a cryorefrigerator ( 2 ) with periodic operation, the device being characterized in that it comprises:

at least one temperature sensor ( 101 ) for measuring the periodic variation in the temperature T of the element ( 10 ) associated with the periodic operation of the cryorefrigerator ( 2 );

a processor or a set of processors ( 102 , 103 , 106 , 107 , 108 ) for determining the equivalent heat flux (S φeq , S* φeq ) associated with said periodic variation of the temperature T of the element ( 10 );

at least one actuator ( 104 ) for injecting a heat flux (W) into the element ( 10 ) on the basis of a heat flux control signal (S W ) depending on the equivalent heat flux signal (S φeq , S* φeq ); and

a connection line ( 109 ) for injecting the heat flux control signal (S W ) to the input at least of said processor or set of processors ( 102 ) for determining the equivalent heat flux (S φeq , S* φeq ).

8. A device according to claim 7 , wherein the processor ( 103 ) is provided that are capable of delivering a control signal (S C ) for improving the compensation of the periodic variations in the temperature of the element at low frequencies.

9. A device according to claim 7 , wherein the actuator ( 104 ) for injecting a heat flux into the element ( 10 ) comprise a variable magnetic field generator associated with an isothermal heat bath for adiabatically magnetizing or demagnetizing a device connected to the element ( 10 ).

10. A device according to claim 7 , wherein said temperature sensor ( 101 ) for determining the periodic variation of the temperature of the element ( 10 ) and said means ( 104 ) for injecting a heat flux (W) into the element ( 10 ) are arranged side by side.

11. A cryogenic installation for cooling an element ( 10 ) with a cryorefrigerator ( 2 ) with periodic operation, said installation including a stabilizer ( 3 ) connected to the cryorefrigerator ( 2 ) and a cooling circuit ( 4 ) having a first heat exchanger ( 41 ) connected to the stabilizer ( 3 ), and a second heat exchanger ( 42 ) connected to the element ( 10 ), the installation being characterized in that it further comprises a device according to claim 7 .