Cobalt 60 secondary gamma-ray standard, 1 rd (10E6 dps)

Background on secondary gamma-ray standards, Object IDs 1994.0125.55, .56, .57, & .58
Instruments used for radiation detection, measurements, or surveys need to be calibrated periodically. A radioactive source (not necessarily calibrated) is used to confirm the satisfactory operation of an instrument. A standard source is a radiation source exhibiting a disintegration (e.g., disintegrations per second or dps), emission or exposure rate certified by or traceable to the U.S. National Institute of Standards and Technology (NIST), formerly the National Bureau of Standards (NBS). NIST maintains the primary radiation sources, and makes available and/or certifies secondary sources for instrument calibration. For details on survey instrument calibration, see:
Detailed description of Cobalt 60 secondary gamma-ray standard, 1 rd, Object 1994.0125.55
Glass ampoule, approximately 3” long, 5/8” in diam., held by cotton wool in test-tube shaped transparent container capped by a shiny steel screw-cap 5 3/4” long, 7/8” diam. About two-thirds of the ampoule volume contains a slightly pinkish-tinged liquid. A small paper label is glued on the ampoule with typed legend: Co[E]60 / “1 rd”.
Received with NBS certificate, dated 1948 Jan. 30, stating that the ampoule contains 1.59 rutherfords (rd) per milliliter, and a subsequent correction that it contains 1.59 rd, total. (Herbert Clark’s letter 1994 May 4, identifies the rutherford as unit of radioactivity, 1 rd = 10E6 dps, introduced in 1946, but short-lived. The new unit is the Becquerel (bq), where 1 bq = 1 dps). The plastic container for the ampoule has a small adhesive label with the following printed words: “Caution Radioactive Material”.
Currently not on view
Object Name
gamma-ray standard, secondary, Co60
date made
National Bureau of Standards
Physical Description
liquid with cobalt 60 (overall material)
plastic (overall material)
cotton (overall material)
steel (overall material)
paper (overall material)
glass (overall material)
overall (transparent, capped plastic container): 5 3/4 in x 7/8 in; 14.605 cm x 2.2225 cm
glass ampoule: 3 in x 5/8 in; 7.62 cm x 1.5875 cm
ID Number
accession number
catalog number
Science & Mathematics
Science & Scientific Instruments
Measuring & Mapping
Modern Physics
See more items in
Medicine and Science: Modern Physics
Modern Physics
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Rensselaer Polytechnic Institute. Department of Chemistry
Additional Media

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