Negative ion source

Patent · 01 January 1987

OSTI ID:866175

Delmore, James E ^[1]

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1. Idaho Falls, ID

A method and apparatus for providing a negative ion source accelerates electrons away from a hot filament electron emitter into a region of crossed electric and magnetic fields arranged in a magnetron configuration. During a portion of the resulting cycloidal path, the electron velocity is reduced below its initial value. The electron accelerates as it leaves the surface at a rate of only slightly less than if there were no magnetic field, thereby preventing a charge buildup at the surface of the emitter. As the electron traverses the cycloid, it is decelerated during the second, third, and fourth quadrants, then reeccelerated as it approaches the end of the fourth quadrant to regain its original velocity. The minimum velocity occurs during the fourth quadrant, and corresponds to an electron temperature of 200.degree. to 500.degree. for the electric and magnetic fields commonly encountered in the ion sources of magnetic sector mass spectrometers. An ion source using the above-described thermalized electrons is also disclosed.

• Research Organization: EXXON NUCLEAR IDAHO CO
• DOE Contract Number: AC07-79ID01675
• Assignee: United States of America as represented by United States (Washington, DC)
• Patent Number(s): US 4649279
• OSTI ID: 866175
• Country of Publication: United States
• Language: English

Related Subjects

/250/315/
200
500
above-described
accelerates
apparatus
approaches
arranged
below
buildup
charge
commonly
commonly encountered
configuration
corresponds
crossed
crossed electric
cycloid
cycloidal
decelerated
degree
disclosed
electric
electron
electron emitter
electron temperature
electron velocity
electrons
emitter
encountered
field
fields
filament
fourth
hot
hot filament
initial
leaves
magnetic
magnetic field
magnetic fields
magnetic sector
magnetron
mass
mass spectrometer
mass spectrometers
method
minimum
negative
occurs
original
path
portion
preventing
providing
quadrant
quadrants
rate
reduced
reduced below
reeccelerated
regain
region
resulting
sector
sector mass
slightly
source
sources
spectrometers
surface
temperature
thermalized
third
traverses
value
velocity