Cryostat with active neck tube cooling by a second cryogen

Patent metadata

Field	Value
Publication number	US-10352501-B2
Application number	US-201615194923-A
Country	US
Kind code	B2
Filing date	Jun 28, 2016
Priority date	Jul 1, 2015
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

A cryostat arrangement has an outer jacket, a first tank with a first cryogen, and a second tank with a second liquid cryogen which boils at a higher temperature than the first cryogen. The first tank comprises a neck tube, whose hot upper end is connected to the outer jacket at ambient temperature and whose cold lower end is connected to the first tank at a cryogenic temperature. The arrangement uses a riser pipe protruding into the second tank through which the second liquid cryogen can flow out of the second tank and into a first heat exchanger in thermal contact with the neck tube. An outflow line is provided through which second cryogen evaporating from the first heat exchanger can flow out and into an optional second heat exchanger. It is thus possible to greatly reduce heat input from the neck tube into the first tank.

First claim

The invention claimed is:

1. A cryostat arrangement for storage of a first cryogen, the cryostat arrangement having an outer jacket and a first tank installed within the outer jacket with the first cryogen in addition to a second tank holding a second liquid cryogen, wherein the first cryogen boils at a lower temperature than the second cryogen and wherein the first tank comprises a neck tube whose hot upper end is connected to the outer jacket at ambient temperature and whose cold lower end is connected to the first tank at cryogenic temperature, the arrangement comprising:
a riser pipe protruding into the second tank such that the second liquid cryogen can flow out of the second tank through the riser pipe, a lower end of the riser pipe being located in the second liquid cryogen in the second tank, and
a first heat exchanger into which the riser pipe opens directly or indirectly with the riser pipe's upper end, the first heat exchanger having an outflow line such that evaporating second cryogen from the first heat exchanger can flow out through the outflow line, the first heat exchanger being located outside of the neck tube in direct thermal contact therewith so as to provide local cooling via the second cryogen from the riser pipe.

2. The cryostat arrangement according to claim 1 , wherein a level of the second liquid cryogen in the riser pipe is above a level in the second tank because of a pressure difference between the outflow line and a gas volume above a liquid surface in the second tank, and the first heat exchanger is fed with second liquid cryogen from the riser pipe.

3. The cryostat arrangement according to claim 1 , further comprising an exhaust line through which evaporating second cryogen vents from the second tank, wherein the exhaust line has a flow resistance device and a pressure difference between the outflow line and a gas volume above the liquid surface in the second tank can be controlled by the flow resistance device.

4. The cryostat arrangement according to claim 3 , wherein the flow resistance device comprises a control valve.

5. The cryostat arrangement according to claim 1 wherein the outflow line has a pump, and wherein a pressure difference between the outflow line and a gas volume above the liquid surface in the second tank can be controlled by the pump.

6. The cryostat arrangement according to claim 5 , wherein the pump comprises a control valve.

7. The cryostat arrangement according to claim 1 further comprising a second heat exchanger arranged in thermal contact with the neck tube above the first heat exchanger, the second heat exchanger providing additional local cooling using evaporating second cryogen from the first heat exchanger.

8. The cryostat arrangement according to claim 7 further comprising a temperature sensor arranged on the neck tube adjacent to the second heat exchanger.

9. The cryostat arrangement according to claim 1 wherein a distributor tank is arranged in thermally conducting contact with the second tank in the outer jacket above the second tank, and wherein second liquid cryogen from the riser pipe is fed into the distributor tank and second liquid cryogen can be conveyed out of the distributor tank into the first heat exchanger.

10. The cryostat arrangement according to claim 9 , wherein the distributor tank has the form of a ring.

11. The cryostat arrangement according to claim 1 wherein the outflow line is connected directly or indirectly to a branch piece and the branch piece is connected directly or via a flow resistance device to an exhaust line, and wherein the exhaust line is connected to the second tank.

12. The cryostat arrangement according to claim 1 further comprising at least one of a flow meter located in the outflow line for determining a flow rate of second cryogen flowing out through the outflow line and a flow meter located in an exhaust line through which evaporating second cryogen vents from the second tank for determining a flow rate of the second cryogen outgassing through the exhaust line.

13. The cryostat arrangement according to claim 1 further comprising a temperature sensor arranged on the neck tube adjacent to the first heat exchanger.

14. The cryostat arrangement according to claim 1 further comprising a pressure sensor located in the second tank.

15. The cryostat arrangement according to claim 14 wherein the pressure sensor is located near the lower end of the riser pipe.

16. The cryostat arrangement according to claim 1 further comprising a filling level sensor located in the second tank.

17. The cryostat arrangement according to claim 1 wherein the cryostat arrangement is used for cooling a superconducting magnet assembly as part of a magnetic resonance apparatus.

18. A method for operating a cryostat arrangement according to claim 1 , the method comprising adjusting a pressure difference between the outflow line and a gas volume above a liquid surface in the second tank so that there is a flow of the second cryogen through the heat exchanger.

19. The method according to claim 18 , further comprising the following steps:
i) detecting at least one parameter selected from
a) a flow rate on the outflow line or on an exhaust line through which evaporating second cryogen vents from the second tank, using a flow meter,
b) a temperature on the neck tube, using a temperature sensor,
c) a pressure difference between a pressure of the second liquid cryogen and a pressure in the outflow line, using a pressure sensor and
d) a filling level in the second tank, using a filling level sensor,

ii) comparing a value of the detected at least one parameter with a predetermined value of that parameter, and
iii) adjusting a pressure difference between the outflow line and the gas volume above the liquid surface in the second tank
a) as a function of a filling level in the second tank or
b) so that the at least one parameter detected in step (i) is substantially equal to the predetermined value of that parameter.

20. The method according to claim 18 wherein the pressure difference between the outflow line and the gas volume above the liquid surface in the second tank is adjusted by means of a pump or a flow resistance device.

Assignees

• Bruker Biospin Gmbh

Inventors

• Wikus Patrick
• Bonn Steffen

Classifications

• F17C2270/02

  for medical applications · CPC title

• F17C2260/031

  due to heat transfer · CPC title

• F17C2250/00

  Accessories; Control means; Indicating, measuring or monitoring of parameters · CPC title

• H01F6/04 Primary

  Cooling · CPC title

• F17C2221/014

  Nitrogen · CPC title