Abstract: A cryogenic cooling system that includes a cooled plate thermally coupled to a cryogenic refrigerator, a target assembly that includes a target refrigerator configured to achieve a lower base temperature than the cryogenic refrigerator, and a heat switch assembly with one or more gas gap heat switches. The heat switch assembly has a first end thermally coupled to the cooled plate and a second end thermally coupled to the target assembly. A sorption pump is configured to control thermal conductivity across the heat switch assembly based on the temperature of the sorption pump. The sorption pump is thermally coupled to the cryogenic refrigerator by a thermal link extending from the cooled plate to the heat switch assembly, with the sorption pump positioned along the thermal link between the cooled plate and the heat switch assembly.

Abstract: A charged particle beam source for a surface processing apparatus is disclosed. The charged particle beam source comprises: a plasma chamber; a plasma generation unit adapted to convert an input gas within the plasma chamber into a plasma containing charged particles; and a grid assembly adjacent an opening of the plasma chamber. The grid assembly comprises one or more grids each having a plurality of apertures therethrough, the one or more grids being electrically biased in use so as to accelerate charged particles from the plasma through the grid(s) to thereby output a charged particle beam, the major axis of which is substantially perpendicular to the plane of the grid assembly.

Abstract: A quench protection arrangement for a superconducting magnet is disclosed. The arrangement comprises: a superconducting magnet comprising a plurality of magnet sections; a plurality of varistors, wherein each of the plurality of varistors is electrically connected in parallel across a respective one of the plurality of magnet sections; and a heater arrangement electrically connected to the plurality of varistors and configured to apply heat to each of the plurality of magnet sections in response to a change in a voltage across any one or more of the plurality of varistors. A method of protecting a superconducting magnet is also disclosed.

Abstract: A cryogenic cooling system is provided having a vessel, the vessel comprising extending along a longitudinal axis and configured to receive a sample probe movable along the longitudinal axis. One or more cooling members are thermally coupled to the vessel so as to produce a thermal gradient along the longitudinal axis of the vessel. A vent extends along the outside of the vessel and is configured to provide a pathway for a flow of gas from an inlet of the vent to an outlet of the vent. The inlet is in gaseous communication with the inside of the vessel and the outlet is in gaseous communication an environment external to the vessel. The inlet is arranged at a position along the vessel configured to obtain a temperature below 63 kelvin during operation of the one or more cooling members, and the outlet is arranged at a position configured to maintain a temperature above 273 kelvin when the outlet has a temperature below 63 kelvin.

Abstract: There is provided a method of reducing noise in a cryogenic cooling system associated with a mechanical refrigerator forming part of said cooling system. The method comprises: monitoring vibrations in the cooling system during operation of the mechanical refrigerator; and modulating an operating frequency of the mechanical refrigerator based on the monitored vibrations so as to reduce the amplitude of said vibrations. This allows noise within the cooling system to be reduced.

Abstract: A system for preventing collisions between components in a particle beam instrument is disclosed. The system is particularly beneficial in use with instruments wherein moveable components are used within a chamber that obscures them from being viewed from outside the chamber. The system comprises: a capacitance sensor configured to monitor the capacitance between a first component and a second component of the instrument, and a proximity module configured to: derive a capacitance parameter from the monitored capacitance between the first component and the second component; and output a proximity alert signal in accordance with a comparison between the derived capacitance parameter and a predetermined capacitance parameter threshold value.

Abstract: A method and system for analyzing a specimen in a microscope are disclosed.

Abstract: A cryogenic cooling system is provided comprising: a mechanical refrigerator, a heat pipe and a heat switch assembly. The mechanical refrigerator has a first cooled stage and a second cooled stage. The heat pipe has a first part coupled thermally to the second cooled stage and a second part coupled thermally to a target assembly. The heat pipe is adapted to contain a condensable gaseous coolant when in use. The heat switch assembly comprises one or more gas gap heat switches, a first end coupled thermally to the second cooled stage and a second end coupled thermally to the target assembly. The cryogenic cooling system is adapted to be operated in a heat pipe cooling mode in which the temperature of the second cooled stage is lower than the first cooled stage and wherein the temperature of the target assembly causes the coolant within the second part of the heat pipe to be gaseous and the temperature of the second cooled stage causes the coolant in the first part of the heat pipe to condense.

Abstract: A method and system for processing a diffraction pattern image obtained in an electron microscope are disclosed.

Abstract: A system for preventing collisions between components in a particle beam instrument is disclosed. The system is particularly beneficial in use with instruments wherein moveable components are used within a chamber that obscures them from being viewed from outside the chamber. The system comprises: a capacitance sensor configured to monitor the capacitance between a first component and a second component of the instrument, and a proximity module configured to: derive a capacitance parameter from the monitored capacitance between the first component and the second component; and output a proximity alert signal in accordance with a comparison between the derived capacitance parameter and a predetermined capacitance parameter threshold value.

Abstract: A cryogenic cooling system is provided comprising a first stage 6, a second stage 7, and a third stage 8, wherein the second stage 7 is arranged between the first stage 6 and the third stage 8. A first dilution unit 12 is provided comprising a first still 11 and a first mixing chamber 13, wherein the first still 11 is thermally coupled to the first stage 6 and the first mixing chamber 13 is thermally coupled to the third stage 8. A second dilution unit 32 is further provided comprising a second still 31 and a second mixing chamber 33, wherein the second still 31 is thermally coupled to the first stage 6 and the second mixing chamber 33 is thermally coupled to the second stage 7.

Abstract: A cryogenic refrigeration system is provided having particular application in cooling a Magnetic Resonance Imaging system. The cryogenic refrigeration system comprises a conduit arranged as a cooling circuit through which a coolant fluid is pumped, the conduit being in thermal communication with a least one cooled stage for cooling the coolant fluid to a first temperature, and wherein the conduit comprises a cryotrap in communication with the coolant fluid, the cryotrap being operable to remove contaminants from the coolant fluid by cryogenic pumping. The conduit further comprises a flow impedance for cooling the coolant fluid to a second temperature lower than the first temperature, and a hydrogen filter upstream of the flow impedance and in communication with the coolant fluid, the hydrogen filter being cooled to a temperature below the freezing point of hydrogen in the coolant fluid and operable to remove contaminant hydrogen from the coolant fluid.

Abstract: A method for forming a gas gap heat switch is provided comprising the following steps: (a) providing first and second conductors, and first and second connecting members, wherein the connecting members each have a thermal conductivity at least five times smaller than that of the conductors when at a temperature of 100K; (b) fusing the first conductor to the first connecting member and the second conductor to the second connecting member; (c) aligning the conductors such that the first and second conductors extend along a common major axis; (d) bringing proximal ends of the aligned conductors into contact with each other when said conductors are at a first temperature; and (e) joining the first connecting member to the second connecting member so as to form a chamber around at least the proximal ends of the conductors.

Abstract: A method is provided for performing electron diffraction pattern analysis upon a sample in a vacuum chamber of a microscope. Firstly a sample is isolated from part of a specimen using a focused particle beam. A manipulator end effector is then attached to the sample so as to effect a predetermined orientation between the end effector and the sample. With the sample detached, the manipulator end effector is rotated about a rotation axis to bring the sample into a predetermined geometry with respect to an electron beam and diffraction pattern imaging apparatus so as to enable an electron diffraction pattern to be obtained from the sample while the sample is still fixed to the manipulator end effector. An electron beam is caused to impinge upon the sample attached to the manipulator end effector so as to obtain an electron diffraction pattern.

Abstract: A cryogenic cooling system can include a cooling device and a sample holder. The system can also include a first optical member having a first aperture and a first collimator, where the first collimator is positioned to collimate the light. The system can further include a second optical member having a second aperture and a second collimator where the second collimator is positioned to collimate the light, the first optical member being mounted to the cooling device and the second optical member being mounted to the sample holder. When the sample holder is mounted to the cooling device, a relative position of the first optical member and the second optical member allows the light to pass between the first and second apertures via the first collimator and second collimator separated by a physical gap to allow optical communication between the first optical member and the second optical member.

Abstract: A method and apparatus for analysis of a specimen in a microscope are provided. A first survey is performed that collects analytical data from a region of interest on the specimen surface using a first set of conditions. A second survey is performed that collects additional analytical data from selected parts of the region of interest on the specimen surface using a second set of conditions, different from the first set of conditions. The analytical data from the first survey is used to select the parts used for data collection in the second survey and to decide the order in which they are used.

Abstract: Apparatus for controlling a cryogenic cooling system is described. A supply gas line (3A) and a return gas line (3B) are provided which are coupled to a compressor (1) and to a mechanical refrigerator (2) via a coupling element (4). The coupling element is in gaseous communication with the supply (2A) and return gas lines and supplies gas to the mechanical refrigerator (2). The pressure of the supplied gas is modulated by the coupling element in a cyclical manner. A pressure sensing apparatus (6) monitors the pressure in at least one of the supply and return gas lines. A control system (5) is used to modulate the frequency of the cyclical gas pressure supplied by the coupling element in accordance with the pressure monitored by the pressure sensing apparatus. An associated method of controlling such a system is also described.

Abstract: A method for forming a gas gap heat switch is provided comprising the following steps: (a) providing first and second conductors, and first and second connecting members, wherein the connecting members each have a thermal conductivity at least five times smaller than that of the conductors when at a temperature of 100K; (b) fusing the first conductor to the first connecting member and the second conductor to the second connecting member; (c) aligning the conductors such that the first and second conductors extend along a common major axis; (d) bringing proximal ends of the aligned conductors into contact with each other when said conductors are at a first temperature; and (e) joining the first connecting member to the second connecting member so as to form a chamber around at least the proximal ends of the conductors.