GB2197981A

GB2197981A - Cold stage for a microscope

Info

Publication number: GB2197981A
Application number: GB08723069A
Authority: GB
Inventors: Clare Frances Byrne; Peter Knowles
Original assignee: Marconi Co Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1986-11-14
Filing date: 1987-10-01
Publication date: 1988-06-02
Also published as: GB8627288D0; GB8723069D0

Abstract

A sample stage for an electron microscope is arranged to be cooled by a Joule-Thompson miniature cooler using a gas coolant. The sample stage 1 is sited at the tip of a "cold finger" 3 which is cooled by high pressure gaseous nitrogen supplied through inlet pipe 5 connected to manifold 7, and to which the outlet pipe 6 is also secured. The valve 9 in the inlet pipe is controlled in response to the sample stage temperature to regulate the cooling thereof. The small size of the device allows it to be accommodated in the microscope in addition to the standard ambient temperature stage. The two sample stages are mounted on the same translation platform, so modification of the microscope is minimal. <IMAGE>

Description

Cold Stage for a Microscope This invention relates to a cold stage for a microscope and to a microscope assembly incorporating such a cold stage. It is particularly suitable for use with an electron microscope.

In order to study materials at very low temperatures it is necessary to build into a microscope assembly a sample stage (i.e. a platform on which a sample can be mounted) which can be maintained at the required low temperature. Conventional methods by which such a cold stage is provided involve considerable modification of the microscope and can be expensive. This arises because of the bulk of the necessary apparatus - the sample stage itself, the cooling mechanism, conventionally using liquid refrigerants, and translation mechanisms.

An object of this invention is to provide a small cold stage intended to overcome these problems.

According to the invention a microscope includes a sample stage arranged to be cooled by a Joule-Thompson device using a gas coolant. The microscope, which may be an electron microscope, preferably also includes a further sample stage arranged to be maintained at ambient temperature. Both sample stages are mounted preferably on the same translation platform, for movement of the sample in the plane transverse to the optical axis. The supply of gas to the cooling device may be controlled by a valve responsive to the temperature of the cooled sample stage to maintain a steady controlled temperature.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, of which Figure 1 shows a cold stage in accordance with the invention; and Figure 2 shows the cold stage together with an ambient stage.

Referring to Figure 1, the sample stage 1 is positioned at the tip of a "cold finger" 3 which contains a Joule-Thompson miniature cooler. Coolant gas, for example, nitrogen is supplied to the cold finger 3 at high pressure via inlet pipe 5. The gas expands in the Joule-Thompson cooler, taking heat from the finger and the sample stage 1. The low pressure gas is then extracted via exhaust pipe 6. Connections between the inlet and outlet pipes 5, 6 and the cooler are provided at a manifold 7.

The temperature of the sample stage 1 can be controlled between ambient temperature and the boiling point of the coolant gas by means of a valve 9 in the high pressure inlet pipe 5. This valve is slaved to a temperature sensor (not shown) on the sample stage so that a steady sample temperature is maintained. Modification necessary to accommodate the cooling mechanism is minimal because of the small size of the inlet and exhaust pipes 5, 6.

The sample stage is mounted on a translation platform 11 which allows movement of the sample in a horizontal plane. The small size of the cold finger 3 means that the same translation platform 11 can be used for the standard ambient temperature sample stage of the microscope as shown in Figure 2. The cold stage is thus accommodated as an additional sample stage without removing or substantially modifying the standard facility.

The translation platform 11 can be moved from side to side (X-direction) and in and out (Y-direction). The translation mechanism itself is not shown. The cold sample stage 1 and an ambient stage 2 are mounted on a block 4 which is bolted to a base plate 8 on which the manifold 7 is mounted. The ambient stage 2 can also be rotated and tilted. The construction may also allow very limited tilting (i.e rotation about the X or Y axes) of the cold stage.

To prevent ice and liquefied air collecting on the cold sample it should be housed in an evacuated chamber. This requirement makes the invention particularly suitable for electron microscopes in which the sample space is necessarily evacuated.

Claims

1. A microscope including a sample stage arranged to be cooled by a Joule-Thompson device using a gas coolant.

2. A microscope according to Claim 1 including a further sample stage arranged to be maintained at ambient temperature.

3. A microscope according to Claim 2 wherein both sample stages are mounted on the same translation platform for movement of the sample in the plane transverse to the optical axis.

4. A microscope according to any preceding claim wherein the supply of gas to said Joule-Thompson device is controlled by a valve responsive to the temperature of the cooled sample stage to maintain a steady controlled sample temperature.

5. An electron microscope according to any preceding claim.

6. A microscope substantially as hereinbefore described with reference to the accompanying drawings.