Cryogen free cooling apparatus and method

Abstract

A cryogen free cooling apparatus comprises at least one heat radiation shield ( 54 ) surrounding a working region ( 20 ) and located in a vacuum chamber ( 4 ). A cryogen free cooling system has a cooling stage coupled to the heat radiation shield ( 54 ). Aligned apertures ( 56,58 ) are provided in the heat radiation shield and vacuum chamber walls. Sample loading apparatus has a sample holding device ( 2 ) attached to one or more elongate probes ( 3 ) for inserting the sample holding device through the aligned apertures ( 56,58 ) to the working region ( 20 ); and a thermal connector enables the sample holding device to be releasably coupled for heat conduction via said connector to a cold body or cold bodies within the vacuum chamber so as to pre-cool a sample on or in the sample holding device.

1 . A cryogen free cooling apparatus comprising at least one heat radiation shield surrounding a working region and located in a vacuum chamber; a cryofree cooling system such as a mechanical cooler such as a GM cooler, Stirling cooler or pulse tube device, having a cooling stage coupled to the heat radiation shield; aligned apertures in the heat radiation shield and vacuum chamber wall; sample loading apparatus having a sample holding device attached to one or more elongate probes for inserting the sample holding device through the aligned apertures to the working region; and a thermal connector, whereby the sample holding device can be releasable coupled for heat conduction via said connector to a cold body or cold bodies within the vacuum chamber so as to pre-cool a sample on or in the sample holding device, characterized in that the or each probe is releasably coupled to the sample holding device whereby a first operation of the probe(s) causes the sample holding device to be connected to a support at the working region, and a subsequent operation enables the probe(s) to be released from the sample holding device and retracted. 
     
     
         2 . Apparatus according to  claim 1 , wherein the or one cold body is formed by a surface linked to a cold plate coupled to a cooling stage of the cooling system. 
     
     
         3 . Apparatus according to  claim 1 , wherein the or one cold body is formed by a heat radiation shield, whereby the first connector can be releasably coupled for heat conduction to the heat radiation shield. 
     
     
         4 . Apparatus according to  claim 3 , further comprising a second heat radiation shield located inside the first radiation shield and surrounding the working region, the cryogen free cooling system having a second cooling stage, colder than the first cooling stage, coupled to the second heat radiation shield, the second radiation shield having an aperture aligned with the apertures of the first heat radiation shield and vacuum chamber wall so as to allow the sample holding device to pass therethrough, whereby the sample holding device can be releasably coupled for heat conduction to the second heat radiation shield acting as the or a cold body. 
     
     
         5 . Apparatus according to  claim 4 , wherein the second heat radiation shield is held at a temperature of less than 6K. 
     
     
         6 . Apparatus according to  claim 1 , wherein the first heat radiation shield is held at a temperature of between 45K and 90K. 
     
     
         7 . Apparatus according to  claim 1 , wherein the cold body is the coldest body within the cooling apparatus, the thermal connector enabling a weak thermal connection to be achieved with the sample holding device and subsequently a stronger thermal connection allowing a greater rate of heat flow. 
     
     
         8 . Apparatus according to  claim 1 , wherein the vacuum chamber aperture includes a closure system such as a vacuum valve. 
     
     
         9 . Apparatus according to  claim 1 , wherein the or each heat radiation shield aperture is closable by a respective closure system. 
     
     
         10 . Apparatus according to  claim 9 , wherein the closure system for the aperture of the or each heat radiation shield comprises one or more flexible flaps or hinged and sprung flaps. 
     
     
         11 . Apparatus according to  claim 1 , wherein the sample loading apparatus comprises two or more elongate probes, each coupled to the sample holding device. 
     
     
         12 . Apparatus according to  claim 11 , wherein the or each probe is rotatable about its axis relative to the sample holding device. 
     
     
         13 . Apparatus according to  claim 11 , wherein the or each probe is screw threaded at one end to define the thermal connector, the connector cooperating with a screw thread on the or one of the cold bodies to achieve a thermal connection therebetween. 
     
     
         14 . Apparatus according to  claim 1 , wherein one or more of the thermal connectors comprises one or more thermally conductive springs fitted to make thermal contact between the or one cold body and the sample holding device. 
     
     
         15 . Apparatus according to  claim 14 , wherein the conductive springs comprise composite material with high thermal conductivity and high spring force. 
     
     
         16 . Apparatus according to  claim 1 , wherein the sample loading apparatus is rotatable relative to the vacuum chamber and heat shield(s) so as selectively to align with the or each thermal connector or with the respective aperture so as to allow the sample holding device to be passed therethrough. 
     
     
         17 . (canceled) 
     
     
         18 . Apparatus according to  claim 1  wherein the sample loading apparatus further includes a vacuum vessel in which the sample holding device and elongate probe or probes are movably mounted, the vacuum vessel being connectable to the aperture of the vacuum chamber wall. 
     
     
         19 . Apparatus according to  claim 1 , wherein the cryogen free cooling system comprises a mechanical cooler such as a GM cooler, Stirling cooler or pulse tube device. 
     
     
         20 . Apparatus according to  claim 1 , wherein the sample holder includes one or more electrical connectors to allow electrical and thermal connections to be made to a cold body in the working region. 
     
     
         21 . Apparatus according to  claim 1 , wherein the sample holder includes one or more optical connectors such as fiber optic connectors to allow electrical and thermal connections to be made to a cold body in the working region. 
     
     
         22 . A method of loading a sample into the working region of cryogen free cooling apparatus according to  claim 18 , the method comprising:
 placing a sample in or on the sample holding device;   securing the vacuum vessel of the sample loading apparatus to the vacuum chamber and aligned with the aperture of the vacuum chamber;   evacuating the vacuum vessel;   opening the aperture of the vacuum chamber and operating the or each elongate probe to insert the sample holding device through the opened aperture so that the sample holding device is thermally coupled to a cold body;   allowing the sample in or on the sample holding device to be cooled as a result of heat conduction to the cold body; and either
 a) disconnecting the sample holding device from the cold body; and operating the or each elongate probe to insert the sample holding device into the working region, or 
 b) strengthening the thermal connection to the cold body to increase heat flow away from the sample and further cool the sample, and detaching the sample holding device from the or each elongate probe and withdrawing the or each elongate probe and subsequently closing the closure system of the aperture of the vacuum chamber. 
   
     
     
         23 . A method according to  claim 22 , further comprising a second heat radiation shield located inside the first radiation shield and surrounding the working region, the cryogen free cooling system having a second cooling stage, colder than the first cooling stage, coupled to the second heat radiation shield the second radiation shield having an aperture aligned with the apertures of the first heat radiation shield and vacuum chamber wall so as to allow the sample holding device to pass therethrough, whereby the sample holding device can be releasably coupled for heat conduction to the second heat radiation shield acting as the or a cold body, wherein prior to reaching the working region, the sample holding device is thermally coupled to the second heat radiation shield, cooled by allowing heat to flow to the second radiation shield, disconnected from the second radiation shield, and the sample holding device is then inserted into the working region. 
     
     
         24 . (canceled)