Helium management control system
A helium management control system for controlling the helium refrigerant supply from a common manifold supplies cryogenic refrigerators with an appropriate helium supply. The system employs sensors to monitor and regulate the overall refrigerant supply to deliver an appropriate refrigerant supply to each of the cryogenic refrigerators depending on the computed aggregate cooling demand of all of the cryogenic refrigerators. An appropriate supply of helium is distributed to each cryopump by sensing excess and sparse helium and redistributing refrigerant accordingly. If the total refrigeration supply exceeds the demand, or consumption, excess refrigerant is directed to cryogenic refrigerators which can utilize the excess helium to complete a current cooling function more quickly. If the total refrigeration demand exceeds the total refrigeration supply, the refrigerant supply to some or all of the cryogenic refrigerators will be reduced accordingly so that detrimental or slowing effects are minimized based upon the current cooling function.
1. A cryopump, comprising:
a cryopanel;
a cryogenic refrigerator which is configured to cool the cryopanel, the cryogenic refrigerator including a drive motor configured to drive the cryogenic refrigerator, the cryogenic refrigerator being coupled to at least one compressor configured to supply a refrigerant, the at least one compressor including a high pressure supply line and a low pressure exhaust line; and
a controller to control consumption of the refrigerant in the cryogenic refrigerator during a cooling operation bringing the temperature of the cryogenic refrigerator down to operating temperature by varying the speed of the drive motor based on a differential pressure between the high pressure supply line and the low pressure exhaust line of the cryogenic refrigerator.
2. The cryopump as in claim 1 wherein the controller operates using at least three modes of control: normal, over pressure, and under pressure.
3. The cryopump as in claim 2 wherein if the differential pressure is greater than an over pressure mode setpoint, the controller is configured to respond via the cooling operation by operating in over pressure mode, and increasing the drive motor speed.
4. The cryopump as in claim 3 wherein the over pressure mode set point is a pressure differential of 205 psi.
5. The cryopump as in claim 3 wherein the controller is configured to respond to the over pressure mode by decreasing a temperature setpoint of the cryopump.
6. The cryopump as in claim 5 wherein decreasing the temperature setpoint further includes causing the cryogenic refrigerator to consume additional helium and reducing a temperature of the cryopump.
7. The cryopump as in claim 2 wherein if the differential pressure is less than an under pressure mode setpoint, the controller is configured to respond by operating in under pressure mode and decreasing the drive motor speed.
8. The cryopump as in claim 7 wherein the under pressure setpoint is a pressure differential of 190 psi.
9. The cryopump as in claim 7 wherein the controller is configured to operate in under pressure mode by increasing a temperature setpoint of the cryopump.
10. The cryopump as in claim 9 wherein increasing the temperature setpoint further includes allowing the cryogenic refrigerator to warm and consume less helium.
11. The cryopump as in claim 7 wherein the under pressure mode setpoint is used by the controller to vary the speed of the drive motor to match a temperature of a first stage of the cryopump to the temperature setpoint, using closed loop control.
12. The cryopump as in claim 2 further including:
a compressor bank having the at least one compressor configured to supply the refrigerant to the cryogenic refrigerator;
the cryogenic refrigerator arranged to consume the refrigerant; and
the controller configured to regulate refrigerant supply to the cryogenic refrigerator in response to pressure readings from the high pressure supply line and the low pressure exhaust line.
13. The cryopump as in claim 12 wherein the controller is configured to regulate the refrigerant supply in response to a differential pressure (DP) between the high pressure supply line and the low pressure exhaust line.
14. The cryopump as in claim 2 wherein the controller operating in the over pressure mode or the under pressure mode prevents any further changes to the cryopump in order to allow the cryopump to stabilize.
15. The cryopump as in claim 3 wherein the controller compares a differential pressure (DP) between a high pressure supply line and a low pressure exhaust line with the over pressure mode setpoint.
16. The cryopump as in claim 7 wherein the controller compares a differential pressure (DP) between the high pressure supply line and the low pressure exhaust line with the under pressure mode setpoint.
17. The cryopump as in claim 13 wherein the electronic controller is further configured to:
compute an available quantity of the refrigerant; and
regulate consumption of the refrigerant based, at least in part, on the computed available quantity of the refrigerant and the differential pressure (DP).
18. A system of controlling as cryopump, the system comprising:
a cryopanel;
a cryogenic refrigerator which is configured to cool the cryopanel, the cryogenic refrigerator including a drive motor configured to drive the cryogenic refrigerator;
a controller to control consumption of refrigerant in the cryogenic refrigerator during a cooling operation bringing the temperature of the cryogenic refrigerator down to operating temperature by varying the speed of the drive motor based on a differential pressure between a high pressure supply line and low pressure exhaust line of the cryogenic refrigerator; and
a compressor bank, coupled to the cryogenic refrigerator, having at least one compressor configured to supply the refrigerant, the at least one compressor including the high pressure supply line and the low pressure exhaust line.
19. The system of controlling the cryopump as in claim 18 wherein the controller is configured to regulate refrigerant supply to the cryogenic refrigerator in response to a differential pressure (DP) between the high pressure supply line and the low pressure exhaust line.
20. A system of controlling as cryopump, the system comprising:
a cryopump including a cryogenic refrigerator and a drive motor configured to drive the cryogenic refrigerator, the cryogenic refrigerator being coupled to at least one compressor configured to supply a refrigerant, the at least one compressor including a high pressure supply line and a low pressure exhaust line; and
an electronic controller configured to control a cryopump, the electronic controller controlling consumption of the refrigerant in the cryopump during a cooling operation to bring the temperature of the cryogenic refrigerator down to operating temperature by varying the speed of the drive motor based on a differential pressure between the high pressure supply line and the low pressure exhaust line of the cryogenic refrigerator.