Vacuum-insulating system and method for generating a high-level vacuum

• US 7,297,055 B2
• Filed: 03/16/2004
• Issued: 11/20/2007
• Est. Priority Date: 03/16/2004
• Status: Expired due to Fees

• Current Assignee: OL Security LLC (Intellectual Ventures LLC)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Sar, David R., Withrow, Jerry D.
• Primary Examiner(s): Tyler, Cheryl
• Assistant Examiner(s): PETTITT, JOHN F
• Application Number:
  US10/802,064
• Publication Number:
  US 20050204752A1
• Time in Patent Office: 1,344 Days
• Field of Search: 62/555
• US Class Current: 62/55.5
• CPC Class Codes: F17C 2201/0104 cylindrical
• CPC Class Codes: F17C 2201/0133 toroidal
• CPC Class Codes: F17C 2201/032 with substantially vertical main axis
• CPC Class Codes: F17C 2201/056 Small (<1 m3)
• CPC Class Codes: F17C 2203/0391 by vacuum
• CPC Class Codes: F17C 2203/0617 with one layer
• CPC Class Codes: F17C 2221/013 Carbone dioxide
• CPC Class Codes: F17C 2221/05 Ultrapure fluid
• CPC Class Codes: F17C 2223/0192 Three-phase, e.g. CO2 at triple point
• CPC Class Codes: F17C 2223/033 Small pressure, e.g. for liquefied gas
• CPC Class Codes: F17C 2223/043 in the gas
• CPC Class Codes: F17C 2227/0353 using cryocooler
• CPC Class Codes: F17C 2227/0369 in or on a vessel
• CPC Class Codes: F17C 2227/045 by vacuum
• CPC Class Codes: F17C 2250/032 using computers
• CPC Class Codes: F17C 2260/044 Avoiding pollution or contamination
• CPC Class Codes: F17C 2270/05 for industrial use
• CPC Class Codes: F17C 2270/0527 Superconductors
• CPC Class Codes: F17C 2270/0536 Magnetic resonance imaging
• CPC Class Codes: F17C 3/08 by vacuum spaces, e.g. Dewar flask for household use A47J41/02
• CPC Class Codes: F17C 3/085 : Cryostats
• CPC Class Codes: H01F 6/04 : Cooling
• CPC Class Codes: Y10S 417/901 : Cryogenic pumps

Abstract

A method of generating a high-level vacuum comprises evacuating a chamber having a substantially-pure gas therein to a medium-level vacuum, and freezing the residual gas to generate the high-level vacuum within the chamber. Impurities, such as atmospheric air, may be purged from the chamber by evacuating the chamber to a medium level vacuum (e.g., around 10⁻² Torr) and subsequently filling the chamber with the gas. This purging process may be repeated multiple times to decrease the level of impurities in the gas filling the chamber. The substantially-pure gas may have an impurity-level of less than approximately 100 PPM and may comprise carbon-dioxide, although the scope of the invention is not limited in this respect. The medium level vacuum may range between approximately 1×10⁻² Torr and 5×10⁻² Torr allowing the use of a roughing pump, and the high-level vacuum may range between approximately 1×10⁻⁵ and 1×10⁻⁸ Torr.

Claims

1. A method of generating a high-level vacuum comprising:

evacuating a chamber having a substantially-pure gas therein;

freezing residual gas in the chamber to generate a high-level vacuum within the chamber;

purging impurities from the chamber with the gas by filling the chamber with the gas;

repeating the filling and the evacuating to reduce impurities from the chamber and to obtain a high concentration of the gas within the chamber; and

after filling the chamber with the gas, evacuating the chamber prior to freezing to generate a medium-level vacuum,

wherein the substantially-pure gas has in impurity-level of less than approximately 100 parts per million (PPM), and

wherein the gas is carbon-dioxide and has a freezing point of above approximately 100 degrees Kelvin at the medium-level vacuum.

2. The method of claim 1

wherein the chamber comprises a magnet chamber, and wherein freezing comprises reducing the temperature within the chamber by cooling the magnet.

3. The method of claim 2 further comprising after freezing the gas, further cooling the magnet to a cryogenic temperature,

wherein the vacuum within the chamber is to provide insulation for the cryogenically-cooled magnet.

4. A vacuum insulation system comprising:

a chamber having a substantially-pure gas therein at less than atmospheric pressure;

a cooling element to freeze residual gas in the chamber to generate a high-level vacuum within the chamber; and

a gas cylinder having the substantially-pure gas therein at a higher-than atmospheric pressure, the gas cylinder to at least slightly pressurize the chamber with the gas prior to the vacuum pump evacuating the chamber before freezing,

wherein the substantially-pure gas has an impurity-level of less than approximately 100 parts per million (PPM), and

wherein the gas is carbon-dioxide and has a freezing point of above approximately 100 degrees Kelvin at the medium-level vacuum.

5. The system of claim 4 further comprising a magnet within the chamber, and wherein the cooling element is to reduce a temperature within the chamber by cooling the magnet to at or below a freezing point of the gas at the medium-level vacuum.

6. The system of claim 5 wherein after freezing the gas, the cooling element is to further cool the magnet to a cryogenic temperature, and wherein the high-level vacuum within the chamber is to provide insulation for the cryogenically-cooled magnet.

7. The system of claim 5 wherein the magnet is an electromagnet cooled to a superconducting temperature to generate a high-level magnetic field for a radar tube in a radar system.

8. A vacuum insulation system comprising:

a chamber having a substantially-pure gas therein at less than atmospheric pressure; and

a cooling element to freeze residual gas in the chamber to generate a high-level vacuum within the chamber, the chamber having essentially no other gasses therein other than the substantially-pure gas;

a medium-level vacuum pump to reduce the pressure within the chamber to a medium-level vacuum before the cooling element operates to freeze the gas; and

a magnet within the chamber,

wherein the cooling element is to reduce a temperature within the chamber by cooling the magnet to at or below a freezing point of the gas at the medium-level vacuum, and

wherein the magnet is a superconducting magnet in a magnetic-resonance-interference (MRI) diagnostic imaging system.

9. A vacuum insulation system comprising:

a chamber having a substantially-pure gas therein at less than atmospheric pressure; and

a cooling element to freeze residual gas in the chamber to generate a high-level vacuum within the chamber,

wherein the chamber is to insulate an infrared seeker head of a missile, the chamber being provided with the substantially-pure gas therein,

wherein the system further comprises a cooling liquid to freeze the substantially-pure gas within the chamber after launch of the missile to generate in flight the high-level vacuum within the chamber, the cooling liquid to further cool the seeker head to at least a near-cryogenic temperature, and

wherein the cooling liquid comprises liquid argon, and wherein the substantially-pure gas is carbon-dioxide, and wherein the chamber is initially provided with the medium-level vacuum.