Alpha Particle

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The majority of alpha standards listed on pages 36–39 are spectroscopy grade and are suitable for the most exacting research requirements as well as for routine counting room applications. Standards that emit radon gas, most notably Th-228 and Ra-226, should not be used in gross alpha applications. Most sources are prepared by electrodeposition of the desired nuclide on a mirror finish platinum surface foil and are fixed to the surface by diffusion-bonding. These sources exhibit narrow line widths, generally less than 20 keV FWHM for high specific activity nuclides such as Po-210 and Am-241.

Even the lowest intensity uncovered alpha source may deteriorate with time, showing signs of removable activity as well as decreased spectral resolution. This is caused by the migration of the active material into the substrate and by the accumulation of dust and grime. For these reasons the source should be stored in a closed container when not in use. The inside of the container should be checked periodically for free activity. EZIP considers the useful life of alpha sources with long halflives to be two years. We recommend a program of scheduled replacement for these sources. Cf-252 sources are all supplied with a 100 μg/cm2 gold cover. Please note that the gold will not prevent the loss of fission fragments and EZIP suggests the following procedures be followed when handling any Cf-252 source:
- The container should be opened and handled in a hood, glove box, or other well-ventilated enclosure
and only by qualified personnel.
- If possible, when not in use, the source should be stored under vacuum or in inert atmosphere to prevent corrosion.

These sources are not warranted as suitable for any specific application nor is EZIP liable for any damage or contamination to facilities or equipment resulting from their use. All activities of Ra-226 and Th-228 standards are supplied with a 100 μg/cm2 gold cover which is sufficient to prevent loss of radioactive recoil daughter products.

The general warranty does not apply to any open source of Cf-252, Th-228, or Ra-226. Additional gold covering up to 200 μg/cm2 is available upon request. All electroplated sources are prepared +/- 30% of nominal activity.

Alpha Particle Standards—Type A-1
The type A-1 source is permanently fixed in an aluminum holder 1” diameter x 0.125” high (25.4 mm x 3.18 mm). The active diameter is 0.197” (5.0 mm). All alpha standards are offered as spectral grade sources up to the activity and active diameters listed unless otherwise noted. All electroplated alpha standards are manufactured to a tolerance of +/-30% of the nominal activity. All AF type sources are delicate surface sources; the active surface of the source must not be wipe tested or touched.

Alpha Particle Standards—Type A-2

The type A-2 source is permanently fixed in an aluminum holder 0.5” diameter x 0.250” high (12.7 mm x 6.35 mm). The active diameter is 0.197” (5.0 mm). All alpha standards are offered as spectral grade sources up to the activity and active diameters listed unless otherwise noted. All electroplated alpha standards are manufactured to a tolerance of +/-30% of the nominal activity.

Alpha Particle Standards—Type PM
The PM source is mounted in a plastic holder from which it can be separated for installation in a counting chamber or device. The holder is 1” diameter x 0.125” high (25.4 mm x 3.18 mm). The removable active foil is 0.438” (11.1 mm) in diameter with the active diameter 0.197” (5.0 mm). The foils are platinum or platinum clad nickel between 0.005” and 0.010” (0.127 mm and 0.254 mm) thick. All alpha standards are offered as spectral grade sources up to the activity and active diameters listed unless otherwise noted. All electroplated alpha standards are manufactured to an accuracy of +/-30% of the nominal activity.

Alpha Particle Standards—Type PM
The PM source is mounted in a plastic holder from which it can be separated for installation in a counting chamber or device. The holder is 1” diameter x 0.125” high (25.4 mm x 3.18 mm). The removable active foil is 0.438” (11.1 mm) in diameter with the active diameter 0.197” (5.0 mm). The foils are platinum or platinum clad nickel between 0.005” and 0.010” (0.127 mm and 0.254 mm) thick. All alpha standards are offered as spectral grade sources up to the activity and active diameters listed unless otherwise noted. All electroplated alpha standards are manufactured to an accuracy of +/-30% of the nominal activity.

Composite Alpha Source—AF Comp
The composite alpha source is designed to be used as an energy marker for alpha spectroscopy systems. Pu-239, Am-241 and Cm-244, 0.01 μCi (370 Bq) each, are electroplated onto a polished platinum or platinum clad nickel foil. The active area is 0.197” (5.0 mm). The source is supplied uncovered. These nuclides provide alpha particles from approximately 5100 to 5800 keV and exhibit line widths typically less than 20 keV FWHM. This energy range is wide enough to provide a valid energy calibration for most alpha emitting nuclides. The source, when purchased as a NIST traceable standard, can also be used to determine detector efficiencies for alpha particles. Total activity and individual activities are provided on the Certificate of Calibration. The composite alpha source is available in the type A-2, A-1, and PM configurations as described on pages 36–38.

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