Americium-241 for research

• Alpha spectrometry

  Energy calibration of alpha spectrometers^{2, 3, 4}

  Thin Am-241 sources give sharp lines at 5.486 and 5.443 MeV for calibrating silicon alpha detectors.

  More: Energy calibration of alpha spectrometers

  Radiochemistry labs calibrate energy and check resolution with thin sources, often mixed with other alpha emitters such as Pu-239 and Cm-244 so that well-separated peaks span the energy range.

  A typical detector resolves the 5.486 MeV line to about 18 to 20 keV. Thicker sources broaden the peaks and add a tail on the low-energy side.

• Radiation detection

  Low-energy detector calibration^{5, 6}

  Its 59.5 keV gamma ray and neptunium L X-rays are recommended standards for calibrating detectors at low energy.

  More: Low-energy detector calibration

  The IAEA lists Am-241 among the nuclides with evaluated emission probabilities for detector efficiency calibration: the 59.5 keV line in about 36 of 100 decays, the 26.3 keV line, and Np L X-rays from about 12 to 21 keV.

• Elemental analysis

  X-ray fluorescence excitation^{7, 8, 9}

  The 59.5 keV line excites K X-rays of elements from copper to thulium and L X-rays of tungsten to uranium.

  More: X-ray fluorescence excitation

  Portable and laboratory XRF systems have used Am-241 sources, often annular ones around the detector, to measure metals in soil, sediment and other samples. Elements such as tin and barium show their K lines beside the scattered 59.5 keV peak.

• Radiation protection

  Alpha contamination monitors^{10, 11, 12}

  Wide-area Am-241 reference sources calibrate alpha surface contamination monitors.

  More: Alpha contamination monitors

  The IAEA names Am-241 or Pu-239 as the reference nuclides for calibrating alpha surface contamination monitors, with sources specified by surface emission rate. ISO 8769 recommends a source area of at least 100 cm².

  Am-241 alpha particles travel only about 4.2 cm in air and lose most of their energy near the end of the track, so a probe's response falls sharply as it moves from contact to 2 cm off the surface.

• Environmental radioanalysis

  Gross alpha counting¹³

  EPA Method 900.0 prescribes Am-241 for calibrating gross alpha counts of drinking water.

  More: Gross alpha counting

  Labs add an Am-241 standard to tap water aliquots with 0 to 100 mg of dried residue on 2-inch planchets and plot counting efficiency against residue weight. Each sample's efficiency is read from that curve.

• Aerosol science

  Charge neutralizers for particle sizing^{14, 15}

  Am-241 is one of the sources that bring aerosol particles to a known bipolar charge distribution before mobility sizing.

  More: Charge neutralizers for particle sizing

  Mobility particle size spectrometers pass the aerosol through a bipolar diffusion charger, where a radioactive source makes positive and negative ions. The resulting charge fractions follow the Wiedensohler approximation, which the instrument uses to turn measured mobility into particle size.

• Radiobiology

  Alpha-particle irradiation of cells¹⁶

  Am-241 irradiators deliver alpha particles to cells grown on thin Mylar, for studies of densely ionizing radiation.

  More: Alpha-particle irradiation of cells

  In one benchmark irradiator, Am-241 foils behind 1.5 µm Mylar windows delivered 2.9 MeV alpha particles to cultured human fibroblasts. Survival fell exponentially with dose, and per gray the alpha particles were about 7.6 times as effective as Cs-137 gamma rays.

• Alpha spectrometry standard

  Thin Am-241 layer plated on a polished disk, uncovered

  Energy and efficiency calibration

  Feasibility review
• Alpha check source

  Am-241 on a metal disk, open face

  Alpha counter and probe checks

  Feasibility review
• Sealed gamma disk

  Am-241 sealed in a disk that holds the alphas in

  59.5 keV detector checks

  Feasibility review
• Wide-area reference source

  Even deposit on a backing plate

  Alpha contamination monitor calibration

  Feasibility review
• Annular XRF source

  Ring-shaped sealed source

  X-ray fluorescence excitation

  Feasibility review

Activity, certificate and lead time are set with the manufacturer at quote.

Source: IAEA LiveChart of Nuclides, ENSDF evaluation by M. S. Basunia (literature cutoff 15 March 2006), retrieved 25 September 2026 [1]. Reference values; a manufacturer's certificate states the activity of a specific source.

• ¹³³Ba

  Barium-133 for research

  Ba-133 · Half-life 10.55 years

  Gamma lines from 81 to 384 keV and cesium X-rays near 31 keV: a standard for low- and mid-energy calibration.

• ¹³⁷Cs

  Cesium-137 for research

  Cs-137 · Half-life 30.08 years

  One gamma line at 662 keV and a 30-year half-life: a long-lived reference for detector and calibrator checks.

• ⁵⁷Co

  Cobalt-57 for research

  Co-57 · Half-life 271.7 days

  The source behind iron Mössbauer spectroscopy, and a 122 keV standard for detectors and cameras.

• ⁶⁰Co

  Cobalt-60 for research

  Co-60 · Half-life 5.27 years

  Two gamma rays in cascade, at 1173 and 1332 keV: a standard for high-energy calibration and coincidence work.

• ¹⁵²Eu

  Europium-152 for research

  Eu-152 · Half-life 13.52 years

  Gamma lines from 122 to 1408 keV in one source: a standard for calibrating germanium detectors across their range.

• ¹²⁵I

  Iodine-125 for research

  I-125 · Half-life 59.41 days

  A high specific activity label for proteins, peptides and receptor ligands, counted in a gamma counter.

1. IAEA Nuclear Data Section. LiveChart of Nuclides, Am-241 decay data (ENSDF evaluation). Retrieved 25 September 2026. www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html
2. U.S. EPA, NRC, DOE, et al. Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP), Volume II, Chapter 15: Quantification of radionuclides. NUREG-1576, EPA 402-B-04-001B. 2004. www.epa.gov/sites/default/files/2015-05/documents/402-b-04-001b-15-final.pdf
3. U.S. EPA, NRC, DOE, et al. Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP), Volume II, Chapter 16: Data acquisition, reduction, and reporting for nuclear-counting instrumentation. NUREG-1576, EPA 402-B-04-001B. 2004. www.epa.gov/sites/default/files/2015-05/documents/402-b-04-001b-16-final.pdf
4. Chichester DL, Johnson JT, Pope TR, et al. In-field alpha spectrometry system for uranium enrichment verification of uranium hexafluoride. Nucl Instrum Methods Phys Res A. 2023;1054:168311. doi.org/10.1016/j.nima.2023.168311
5. International Atomic Energy Agency. X-ray and Gamma-ray Standards for Detector Calibration. IAEA-TECDOC-619. Vienna: IAEA; 1991. www-pub.iaea.org/MTCD/Publications/PDF/te_619_web.pdf
6. International Atomic Energy Agency. Update of X Ray and Gamma Ray Decay Data Standards for Detector Calibration and Other Applications, Volume 1. Vienna: IAEA; 2007. www-pub.iaea.org/MTCD/Publications/PDF/Pub1287_Vol1_web.pdf
7. U.S. Environmental Protection Agency. Method 6200: Field portable X-ray fluorescence spectrometry for the determination of elemental concentrations in soil and sediment. Washington: EPA; 2007. www.epa.gov/sites/default/files/2015-12/documents/6200.pdf
8. International Atomic Energy Agency. In Situ Applications of X Ray Fluorescence Techniques. IAEA-TECDOC-1456. Vienna: IAEA; 2005. www-pub.iaea.org/MTCD/Publications/PDF/te_1456_web.pdf
9. Kortright JB, Thompson AC. X-ray emission energies (Table 1-2). In: X-Ray Data Booklet. Berkeley: Lawrence Berkeley National Laboratory; 2009. xdb.lbl.gov/Section1/Table_1-2.pdf
10. International Atomic Energy Agency. Calibration of Radiation Protection Monitoring Instruments. Safety Reports Series No. 16. Vienna: IAEA; 2000. www-pub.iaea.org/MTCD/Publications/PDF/P074_scr.pdf
11. Abelquist EW, Clements JP, Huffert AM, et al. Minimum Detectable Concentrations with Typical Radiation Survey Instruments for Various Contaminants and Field Conditions. NUREG-1507, Revision 1. Washington: U.S. Nuclear Regulatory Commission; 2020. www.nrc.gov/docs/ML2023/ML20233A507.pdf
12. Berger MJ, Coursey JS, Zucker MA, Chang J. ESTAR, PSTAR, and ASTAR: computer programs for calculating stopping-power and range tables for electrons, protons, and helium ions. NIST Standard Reference Database 124. Gaithersburg: NIST; 2017. physics.nist.gov/PhysRefData/Star/Text/ASTAR.html
13. U.S. Environmental Protection Agency. Method 900.0: Gross alpha and gross beta radioactivity in drinking water. In: Prescribed Procedures for Measurement of Radioactivity in Drinking Water. EPA-600/4-80-032. Cincinnati: EPA; 1980. www.epa.gov/sites/default/files/2015-06/documents/epa-900.0.pdf
14. Wiedensohler A, Birmili W, Nowak A, et al. Mobility particle size spectrometers: harmonization of technical standards and data structure to facilitate high quality long-term observations of atmospheric particle number size distributions. Atmos Meas Tech. 2012;5(3):657-685. doi.org/10.5194/amt-5-657-2012
15. Kallinger P, Szymanski WW. Experimental determination of the steady-state charging probabilities and particle size conservation in non-radioactive and radioactive bipolar aerosol chargers in the size range of 5-40 nm. J Nanopart Res. 2015;17(4):171. doi.org/10.1007/s11051-015-2981-x
16. Neti PVSV, de Toledo SM, Perumal V, Azzam EI, Howell RW. A multi-port low-fluence alpha-particle irradiator: fabrication, testing and benchmark radiobiological studies. Radiat Res. 2004;161(6):732-738. doi.org/10.1667/RR3181
17. U.S. Nuclear Regulatory Commission. 10 CFR 30.71, Schedule B (exempt quantities). eCFR, current as of 23 September 2026. www.ecfr.gov/current/title-10/section-30.71
18. U.S. Nuclear Regulatory Commission. 10 CFR 30.18, Exempt quantities. eCFR, current as of 23 September 2026. www.ecfr.gov/current/title-10/section-30.18
19. U.S. Nuclear Regulatory Commission. 10 CFR 31.8, Americium-241 and radium-226 in the form of calibration or reference sources. eCFR, current as of 23 September 2026. www.ecfr.gov/current/title-10/section-31.8

Technical review by ConductScience, 25 September 2026. Next review 25 September 2027.