Double pulsed time-of-flight mass spectrometer

A method for improving mass discrimination during an analysis of atoms or molecules in a time-of-flight mass spectrometer, such method conducted within an evacuated chamber, which comprises:

• rapidly removing, at a first well defined time, such atoms or molecules from a surface containing such atoms or molecules in a region of a uniform electric field of a selected strength;
• rapidly ionizing, at a second well defined time after a selected time delay, T.sub.o, the removed atoms or molecules within said uniform electric field with an ionizing beam in a defined region having an average diameter, d, said defined region separated from said surface a first defined distance, R, where R is at least 11/2 times said diameter, d;
• accelerating ions produced by said ionizing in said uniform field region over a second defined distance, S.sub.1 ;
• passing said ions from said uniform electric field into a field-free region for drifting therein a third defined distance, S.sub.2 ;
• passing said ions from said field-free region into a relatively short, high-energy acceleration region to strike an ion detector to produce a signal corresponding to the arrival of said ions;
• measuring said signal as a function of arrival time to obtain such analysis;
• and
• wherein said strength of said uniform electric field, for a given value of R, S.sub.1, S.sub.2, and T.sub.o, is chosen to minimize the arrival time spread of ions of a particular mass at said detector.

A method for improving mass discrimination during an analysis of atoms or molecules in a time-of-flight mass spectrometer, such method conducted within an evacuated chamber, which comprises:

• rapidly removing, at a first well defined time, such atoms or molecules to be analyzed from a surface containing such atoms or molecules in a region of a uniform electric field of a selected strength;
• rapidily ionizing, at a second well defined time after a selected time delay, T.sub.o, the removed atoms or molecules within said uniform electric field with an ionizing beam in a defined region, said defined region being the entire distance from said surface, a first defined distance, R, where R is equal to or less than 1/5 of a second defined distance, S.sub.1 ;
• accelerating ions produced by said ionizing in said uniform field region over said second defined distance, S.sub.1 ;
• passing said ions from said uniform electric field into a field-free region for drifting therein for a third defined distance, S.sub.2, said distance S.sub.2 being six times said second defined distance S.sub.1 ;
• further accelerating said ions in a short accelerating region, having an field strength much greater than said field strength of said uniform electric field adjacent said surface, to strike an ion detector to produce a signal corresponding to the arrival of said ions;
• and
• measuring said signal as a function of arrival time to obtain such analysis.

A method for improving mass discrimination during an analysis of atoms or molecules in a time-of-flight mass spectrometer, such method conducted within an evacuated chamber, which comprises:

• rapidly removing, at a first well defined time, such atoms or molecules to be analyzed from a surface containing such atoms or molecules in a region of a uniform electric field of a selected strength;
• rapidily ionizing, at a second well defined time after a selected time delay, T.sub.o, the removed atoms or molecules within said uniform electric field with an ionizing beam in a defined region having an average diameter, d, said defined region being spaced from said surface a first defined distance, R, where d is small compared to R;
• accelerating ions produced by said ionizing beam in said uniform field region over a second defined distance, S.sub.1 ;
• passing said ions from said uniform electric field into a field-free region for drifting therein for a third defined distance, S.sub.2, said distance S.sub.2 being two times the difference between distance S.sub.1 and R;
• passing said ions into a relatively short accelerating region, having an field strength much greater than said field strength of said uniform electric field adjacent said surface, to strike an ion detector to produce a signal corresponding to the arrival of said ions;
• and
• measuring said signal as a function of arrival time to obtain such analysis.

A method for improving mass discrimination and enriching a specific mass during an analysis of atoms or molecules in a time-of-flight mass spectrometer, such method conducted within an evacuated chamber, which comprises the steps of:

• freezing such atoms or molecules upon a surface;
• rapidly removing, at a first well defined time, such atoms or molecules from said surface in a region of a uniform electric field of a selected strength;
• rapidly ionizing, at a second well defined time and after a selected time delay, T.sub.o, such atoms or molecules with an ionizing beam in a defined region spaced a first defined distance, R, from said surface;
• accelerating ions produced by said ionizing in said uniform field of a second defined distance, S.sub.1 ;
• passing said ions into a field-free region for drifting therein for a third defined distance, S.sub.2 ;
• passing said ions through a switchable electric field into a high-energy acceleration region containing an electron detector and an ion implantation electrode, said detector producing a signal corresponding to the arrival of ions at the implantation electrode due to electrons ejected from said electrode;
• switching said electric field in proper timing to direct selected ions of such specific mass to said surface and remaining ions to said implantation electrode;
• repeating said steps from said removing step to said switching until a desired enrichment level of such mass is achieved;
• then permitting said ions of such specific mass to strike said detector;
• and
• measuring said signal from said detector as a measure of such enrichment and analysis of such specific mass.