Patent ID: 9640364
Date: 2017-05-02
CPC Classifications: G21K,H01J

Claim:
1. A gas field ion source, comprising: an external housing, an internal housing within the external housing, an electrically conductive tip within the internal housing, a gas supply configured to supply a gas to the internal housing, the gas supply comprising a tube terminating within the internal housing, an extractor electrode having a hole to permit ions generated in the neighborhood of the tip to pass through the hole into the external housing, a flapper valve between the internal and the external housing, the flapper valve being configured to increase a flow of gas from the internal housing to the external housing when the flapper valve is opened, and a control configured to open the flapper valve when changing between operating the gas field ion source in a first mode of operation and a second mode of operation, wherein the gas supply is configured so that: in the first mode of operation of the gas field ion source, the gas supply supplies a first noble gas; and in the second mode of operation of operation of the gas field ion source, the gas supply supplies a second noble gas.