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Procedure for gamma-ray spectrometry measurements for activity 

calibration and impurity measurements using High Purity Germanium 

(HPGe) detectors

1. Purpose

This procedure describes the activity calibration of gamma-ray emitting sources (single or 

mixed radionuclides in solution, solid, or gas form, and in special geometries) using the 

Radiation Physics Division (RPD) High Purity Germanium (HPGe) detectors. It also 

describes the procedure for measurements of gamma-ray emitting impurities as required 

for corrections to other radionuclide calibration techniques. 

2. Scope

The HPGe detectors are used for activity (as Bq), emission rates (as gammas/sec) and 

impurity measurements of gamma-ray emitting radionuclides. Measurements include 

source calibrations for different organizations including nuclear power plants,

radiopharmaceutical companies, universities, national laboratories, as well as for the 

National Institute of Standards and Technology (NIST) Standard Reference Material 

(SRM) and radionuclide metrology research programs. 

This calibration service is relevant for radionuclides emitting gamma-rays with energies

between 35 keV and 3.5 MeV and an activity range of 1 kBq to 10 MBq. The nominal 

relative uncertainty range is 0.8 percent to 2 percent (corresponding to 1 standard 

deviation). The calibration of the HPGe system is performed by obtaining efficiency curves 

for different source geometries and source-to-detector distances using NIST SRMs and 

NIST calibrated sources. 

3. Definitions

Terms used in this procedure are listed in IEC 61452 [1] and only a few relevant terms are 

listed here. 

Activity (A): the expected number of spontaneous nuclear decays (transformations) in unit 

time from a specified energy state (excluding prompt decays from lower nuclear levels) for 

a given amount of a radionuclide. Its SI unit is the becquerel (Bq) where one Bq equals one 

decay per second. 

Background: spectral data, including peaks, not caused by decay attributable to the 

measured source but occurring in the surrounding environment or resulting from cosmicray interactions in or adjacent to the detector.

Impurities: radionuclides found in the measured sources that are not the radionuclide of 

interest.
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4. Equipment

The HPGe detectors are setup in accordance with the manufacturer-provided manual in 

combination with the methods described in the IEC 61452 standard. Additional 

information can be found in reference [8].

Gamma-ray measurements of radioactive sources (for activity or impurity analysis) are 

performed using the HPGe Gamma-Ray Spectrometry System located in Building 245, 

Room C015 (basement). This system consists of the following components:

• 5 closed-end coaxial HPGe detectors (known as B-detector, G-detector, N-detector, 

T-detector, X-detector) and 1 Si-drifted detector (known as S-detector), see Table 

1 and Annex B for detectors specifications

• In addition, a Compton suppression system (known as the R-detector) composed of 

a HPGe detector and a NaI(Tl) detector is also available.

• Most of the detectors are shielded by lead, internally surrounded by cadmium and 

copper, see Table 1

• All detectors are connected to digital electronic units (that include the power 

supply, amplifier, and MCA)

• The digital electronics are connected to a personal computer that is connected to 

the NIST network. The computer clock is set to Eastern Standard Time all year 

around and it is periodically synchronized with the NIST atomic clock.

• Gamma-Vision-32 software package for data acquisition [2]

• Genie-2000 [3] and FitzPeaks [4] software packages for data analysis

• Calibrated 54Mn, 56Co, 57Co, 60Co, 85Kr, 85Sr, 88Y, 99Mo, 109Cd, 113Sn, 125I, 125Sb, 

133Ba, 133Xe, 134Cs, 137Cs, 139Ce, 152Eu, 154Eu, 155Eu, 153Gd, 203Hg, 207Bi, 210Pb, 226Ra, 

228Th, 232U, 241Am sources are used for efficiency and energy calibration. The 57Co 

and 60Co sources are also used for periodic constancy check of the energy and 

efficiency calibration. These sources are produced from NIST SRMs, which are 

validated through intercomparisons with other National Metrology Institutions and 

the BIPM, and the periodic submission of measured sources to the International 

Reference System (SIR) for gamma-ray emitting sources at the BIPM [5]. 

The detectors are calibrated through the development of efficiency curves for different 

source geometries and various source-to-detector distances. These efficiency curves are 

verified monthly or more frequently if needed (such as when there has been a change in 

the instrument configuration), using previously calibrated 57Co and 60Co point sources for 

the HPGe detectors and 57Co point sources for the Si-drifted detector to determine the 

efficiency value and energy calibration reproducibility, see Annex E for additional 

information. 

The efficiency curves for the HPGe detectors are developed for point sources (solids), 5 mL 

ampoules (liquids), Marinelli beakers, plastic vials (different volumes) and 33 cm3spheres 

(gas) for gamma-ray emitting sources for the energy range 14 keV < E < 3.6 MeV. For 

additional information about the measurement geometries see Annex B.2.
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The efficiency curves for the Li-drifted Si detector are developed for point sources (solids), 

and 5 mL ampoules (liquids).

Table 1: Details of HPGe detectors1

B-detector G-detector N-detector T-detector X-detector S-detector

Detector HPGe HPGe HPGe HPGe HPGe Li-drifted Si

Detector 

type

n-type

closed-end 

coaxial

n-type

closed-end 

coaxial

p-type

closed-end 

coaxial

p-type

closed-end 

coaxial

p-type

closed-end 

coaxial

Planar

Detector 

dimensions

Diameter:

54.9 mm

Length: 

54.2 mm

Diameter:

58 mm

Length:

57.6 mm

Diameter:

70.4 mm

Length:

86.4 mm

Diameter:

55 mm

Length:

49 mm

Diameter:

49.7 mm

Length:

22.1 mm

Diameter:

10 mm

Length:

5 mm

Shielding Pb: 10 cm

Cd: 3 mm

Cu: 0.635 

mm

Pb: 10 cm

Cd: 3 mm

Cu: 0.635 

mm

Pb: 4.5 cm

Pb: 10 cm

Cd: 3 mm

Cu: 0.635 

mm

Pb: 10 cm

Cd: 3 mm

Cu: 0.635 

mm

None

End-cap 

window Beryllium Beryllium Aluminum Aluminum Carbon fiber Beryllium

High voltage -3.3 kV -4.4 kV -4.0 kV +3.5 kV +3.0 kV -600 V

Amplifier 

model ORTEC 927 ORTEC 

DSpec-Pro ORTEC 927 ORTEC 927 ORTEC ORTEC DSpec jr. 2.0

Shaping time 6 μs 6 μs 6 μs 6 μs 6 μs 10 μs

Energy 

range

30 keV –

3.6 MeV

14 keV –

1.9 MeV

30 keV –

1.9 MeV

30 keV –

1.9 MeV

14 keV –

1.9 MeV

5 keV –

200 keV

Number of 

channels 16384 16384 16384 16384 16384 4096

Electronics 

model Lynx ORTEC 

DSpec-Pro Lynx Lynx

ORTEC 

DSPEC 

502/502A

ORTEC 

DSpec jr. 2.0

Electronics† Digital Digital Digital Digital Digital Digital

Source 

geometries*

ps, amp, gs, 

mb ps, amp ps, amp, gs

ps, amp, gs, 

mb ps, amp ps, amp

* ps: point source; amp: 5mL glass ampoule; mb: Marinelli beaker; gs: gas sphere. For additional 

information about the measurement geometries see Annex B.2

† Settings are described in Annex D 

5. Health and Safety Precautions

Radiation Safety

Sources used for calibration purposes are of low activity. If high activity sources are 

measured, they are transported inside a lead pig to the edge of the detector in order to 

minimize exposure time when mounting the sources on the source holder. Sources not in 

use are kept in a separate room or are kept behind lead bricks when left inside the counting 

room. Calibrations are performed using Ionizing Radiation Safety Committee-approved 

1 Certain commercial equipment, instruments, or materials are identified to foster understanding. Such 

identification does not imply recommendation by the National Institute of Standards and Technology, nor 

does it imply that the materials or equipment identified are necessarily the best available for the purpose.
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protocols and non-radiological activities (e.g. moving lead pigs) are performed using 

management-approved procedures.

6. Procedures

Preliminary

• Customer contact: Customer must be informed of the need for sources to comply 

with the given specifications of geometry and activity limits.

• NIST paperwork and acceptance procedure: submit completed NIST 364 (or NIST 

365), Radioactive Material Request, for approval before arrival of materials. 

Specifically notify the Chief of Radiation Safety Division (RSD) or designate of 

the arrival and departure of all isotopes of plutonium and uranium. Complete any 

other necessary forms if necessary (i.e, NIST 64, Order No; NIST 77, Calibration 

and Test Fee Computing Form; NIST 796A, Shipper’s Declaration for Radioactive 

Materials, etc.). 

• E-Commerce: Note dates of material received (and returned) in the E-commerce 

system

Acceptance of Sources

• Sources are shipped to NIST RSD for documentation and contamination check 

upon arrival. Sources are kept in custody of NIST personnel responsible for the 

source measurements. 

• Sources to be measured by HPGe are labeled as to the source number, radionuclide, 

approximate activity and date (of arrival or, in the case of sources prepared at NIST, 

of preparation).

• NIST personnel fill out a calibration form (see Annex A) indicating the 

radionuclide, approximate activity, reference time, type of measurement required 

(e.g., activity, impurity measurement) and source type (e.g., point source, 5 mL 

ampoule, gas sphere, stainless steel disks or other type as requested by customer).

• Labeled sources are placed in the IN box, placed on top of the source cabinet in 

Room C019 Building 245. If sources are to be measured the same day they are 

received or prepared, they are kept temporarily behind lead bricks in C015.

Measurement Setup 

• Based on activity and radionuclide(s) of interest, select the detector and source-todetector distance. 

• Source-to-detector distance should be such that the count rate is less than 2000 

counts per second (less than 5 % dead time) to minimize corrections due to pileup, 

dead time and/or summing. In some cases, this cannot be achieved, and the source 

is run with a higher dead time, in this case additional corrections are applied, see 

Annex C.

• Install the required source holder according to source type (different geometries 

require different holders) and source-to-detector distance. There are several
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different source holders to accommodate solids, liquids, gas, and other possible 

geometries of the source to be measured (the holders are labeled).

Measurement Sequence

Gamma-ray spectra are acquired using Genie 2000, Maestro, and GammaVisionTM. Genie 

2000 is commercially available software developed and marketed by Mirion/Canberra and 

Maestro and GammaVisionTM are developed and marketed by AMETEK/ORTEC (see 

software manuals for additional information).

• Place the source inside or on top of the correct source holder on the selected 

detector.

• Open GammaVisionTM or Genie 2000 [2, 3]. 

• Choose the selected detector from the detector list.

• Clear old spectra if needed.

• Select counting time (preset the live time in seconds, or data taking can be stopped 

manually).

• Enter description of the source name, counting geometry and date.

• Start taking data by clicking “start.”

• Note in the logbook for the selected detector: the starting acquisition time, 

radionuclide, source number, source type, source-to-detector distance, live time,

and filename under which the spectrum is going to be saved.

• Once the data acquisition time is completed, or the counting time manually stopped 

(by clicking “stop”), save the data in the directory assigned to the selected detector 

(note that files are saved in subdirectories that reflect the month and year in which 

the source was measured). The filename should include radionuclide, source 

number, detector name, source geometry, month, and date.

• For impurity measurements the source is run only once (additional measurements 

may be required).

• For activity or gammas/sec measurements, the source is run 3 times in the same 

geometry of a given detector and in at least 3 other geometries in different detectors.

Data Analysis

Data analysis is performed by hand (with the use of spreadsheets) or by using Genie-2000 

or FitzPeaks (additional information is found in the operational manuals located in Room 

C015 or 300WSAE). The choice of the data analysis software packages was based on inhouse comparisons of the results obtained by several [3] different software packages and 

by hand (using spread sheets). In addition, the data analysis software used by customers 

was taken into account. Such commercial products are identified in order to specify these 

procedures accurately. 

• Copy the spectrum to be analyzed to another personal computer outside of the 

data acquisition room to reduce personnel radiation exposure to any sources 

remaining in the room.

• Copy the background to be used (generally the most recently run) in same folder 

where the measurement spectrum was copied.
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• Use Genie-2000 [3] or FitzPeaks [4] software depending on type of measurement 

[activity, emission rates or impurity].

• Open the file of interest

Impurity Measurements

• Use Genie-2000.

• Report results in Bq.

• Load energy/shape calibration (only) for given detector located in Genie-2000

CALFILES directory (if necessary).

• Load efficiency calibration (only) for given detector and source-to-detector 

distance located in Genie-2000 CALFILES directory.

• Perform a peak search.

• Obtain the peak area.

• Check the fit for each peak using interactive peak fit.

• Subtract the background normalized to the live time.

• Run the efficiency correction. 

• If a radionuclide library entry exists for the particular radionuclides in the source, 

run Nuclide Identification with Interference Correction. If such an entry does not 

exist for the particular radionuclides in the source, then create a library using the 

library editor before running the Nuclide Identification with Interference 

Correction. 

• Run Nuclide Identification (without Interference Correction) or Nuclide 

Identification with Interference Correction using the Detection Limits library.

• Run Detection Limits (Currie MDA). 

• Verify that all the peaks listed are identified. If necessary, manually identify the 

unidentified peaks.

• Apply all corrections needed (source decay, pulse pile-up, cascade summing, 

sample attenuation, see Annex C)

Activity Measurements

• Use Spreadsheets (such as Microsoft Excel), Genie-2000 or FitzPeaks for these 

types of measurements. 

• Create a spreadsheet (can use templates already created using Microsoft Excel, 

see Annex A for an example) that includes: list of radionuclides in the source, 

half-lives for each radionuclide (and associated uncertainty), gamma-ray energies 

(and associated uncertainty), gamma-ray emission probabilities (and associated 

uncertainty), efficiency for each gamma-ray energy (and associated uncertainty), 

live time and run time for the particular measurement, peak area (and associated 

uncertainty) and reference time for reporting the results. Gamma-ray decay data 

should be obtained from ENSDF Nuclear Data Sheets [6] or from LNE-LNHB 

[5] websites.

• Perform a peak search using Genie-2000 or FitzPeaks.

• Obtain the peak area using Genie-2000 or FitzPeaks.
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• Check the fit for each peak using interactive peak fit and extract the peak area for 

each peak of interest using Genie-2000 or FitzPeaks.

• Use the net peak area (and associated uncertainty) to calculate the source activity 

using the spreadsheet, Genie-2000 or FitzPeaks.

• Subtract background from the peak area if there is a background peak at the energy 

of the radionuclide of interest. The background spectrum should be analyzed as 

the sample spectrum to obtain the net peak area for each peak of interest.

• Apply all corrections needed (source decay, pulse pile-up, cascade summing, 

sample attenuation, see Annex C) as described in the references [1, 8].

• Use Genie-2000 to check for impurities and detection limits as described above if 

requested by the customer.

The source activity is obtained from equation (1).

A =

N(E)

T×ε(E)×P(E)

∏i Ci

(1)

where N(E) is the net number of counts in the full-energy peak, T is the live time, (E) is 

the full-energy-peak efficiency, P(E) is the gamma-ray emission probability at the energy 

E, A is the source activity and Ci is the product of the correction factors, Ci, applied to 

the measurement. The correction factors that are applied to these measurements may 

include correction due to the self-attenuation due to difference in the source density, and 

the decay correction of the radionuclide during the measurement time. 

NOTE – On some occasions the source activity per unit mass is required. In those cases, 

the activity in equation (1) needs to be divided by the mass of the source and the uncertainty 

in the mass needs to be propagated as the other variables in equation (2) (see section 7 

“Evaluation of Measurement Uncertainties”).

Reporting Results

Impurity Measurements

The Report should include (see Annex A):

• Radionuclide measured

• Source number 

• Reference date and time (e.g., measurement date and time)

• Detector and source-to-detector distances used for the measurement

• File name of the spectrum analyzed

• Impurities found including activity and uncertainty

• Activity of the main radionuclide in the source and its uncertainty

• Detection limits 

Activity or Emission Rate Measurements

The Report should include (see Annex A):
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• Radionuclides measured

• Source number 

• Reference date and time

• Detectors and source-to-detector distances used for the measurements

• Activity or emission rates of the main radionuclides in the source and the 

associated uncertainty budget

• Any gamma-ray emitting impurities (with activity and associated uncertainty 

budget)

• Detection limits

These reports are then used to create the Report of Test or Report of Calibration as specified 

in section 8.

Validation

The gamma-ray spectrometry measurements are validated by the following techniques:

• Comparison of results achieved with other validated methods.

• Evaluation of measurement uncertainty of the results based on an understanding 

of the theoretical principles of the method and practical experience of the 

performance of the method.

7. Evaluation of Measurement Uncertainties

Uncertainties on gamma-ray spectrometry measurements are determined based on the 

“Guidelines for Evaluation and Expressing Uncertainty of NIST Measurement Results” 

[7]. The Type B components are detailed below. The combined standard uncertainty of the 

activity (or emission rate) measurements is equal to the square root of the quadratic sum of 

the Type A and Type B uncertainties, with a final reported expanded uncertainty obtained 

by multiplying the combined standard uncertainty by a coverage factor of two, representing 

an interval having a level of confidence of approximately 95 %.

Type B uncertainty components:

• Decay (half-life) of the radionuclide

• Live and run times (dead time corrections)

• Peak area fit

• Background peak area variations

• Source-detector geometry

• Pulse pile-up and cascade summing (if corrections are needed)

• Variations in sample attenuation (if attenuators are used in the measurements or 

if measured source density is different from that of the calibration sources)

• Gamma-ray emission probability

• Full-energy-peak efficiency 
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The uncertainty on the impurity measurement is obtained by:

uimp/source = √u

2

eff + u

2

measure

where ueff is the uncertainty of the efficiency for the measured gamma-ray energies for the 

impurity and/or source, and umeasure is the uncertainty calculated based on the gamma-ray 

lines used to determine the activity of the measured impurity and/or source. Only the ueff

and umeasure uncertainty components are used to estimate the expanded uncertainty, as they 

are the biggest contribution. As impurity levels are generally much lower than the nuclide 

being calibrated, the uncertainty on the impurity measurement is often on the order of 5 % 

to 20 % (at 1 sigma, k = 1). The measurement report specifies the coverage factor (i.e., k

value) used to report the measurement uncertainty.

The uncertainty on the source activity (or emission rate) is obtained using uncertainty 

propagation, assuming that all measured quantities are independent. Therefore, when there 

is no correlation, the uncertainty for the source activity, A, is given by:

uA = √(

∂A

∂N)

2

uN

2 + (

∂A

∂T)

2

uT

2 + (

∂A

∂ε)

2

uε

2 + (

∂A

∂P)

2

uP

2 + ∑ (

∂A

∂Ci

)

2

uCi

2

i

(2)

where uN, uT, u€, uP, and uCi are the uncertainties associated with the quantity €N(E)€€T, 

(E), P(E), and Ci, respectively. The nominal uncertainty range is approximately between 

1 – 3 percent (expanded uncertainties, k = 2). Additional information is provided in Annex 

C.

If there is correlation, the uncertainty is evaluated using the technique described in section 

5.2 of the “Guide to the expression of uncertainty in measurement (GUM)” [13]. A tool 

created by the NIST Statistical Engineering Division is used to compute the correlation 

matrix as described in the GUM [14]. This tool can run in Excel or in R [14] and can be 

downloaded from the NIST website [15].

8. Report of Test or Calibration and Technical Review

The NIST Report of Test or Calibration contains information about the composition, the 

properties, and additional required information as stated in NIST-QM-I. 

Prior to issuance, the report undergoes a final technical review. The technical review 

must be approved (and signed) by the principal investigator, Radioactivity Group leader, 

and the RPD chief.

Reports of Test or Calibration, at a minimum, should contain or address the following, 

unless there are valid reasons for not doing so. Additional information may be provided 
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• a title (e.g., “Report of Test”, “Calibration Report” or “Report of Special Test”). 

• the first page shall be on NIST letterhead or be equivalently identified as originating 

from NIST.

• the name and address of the laboratory. 

• the NIST Calibration Services order number, and service ID number. 

• page numbers, with the last page designated as the end of the report. 

• the name and address of the customer (refer to USPS Publication 28, Postal 

Addressing Standards). 

• a description, unambiguous identification, and, when necessary, the condition of 

the item(s) tested or calibrated. 

• the principal radionuclide 

• reference time and date 

• equipment used and method of calibration (traceability to primary standard); a 

description of the calibration method; additions to, deviations, or exclusions from 

the method, if applicable. 

• certified values for activity with the units of measurement 

• decay-scheme assumptions, if applicable

• assessment of radionuclidic purity 

• overall uncertainty determinations for calibration

• the date of receipt of the test or calibration item(s), where this is critical to the 

validity and application of the results. 

• the conditions (e.g., environmental) under which the calibrations were made that 

have an influence on the measurement results, if applicable

• the date(s) of performance of the laboratory activity. 

• the date of issue of the report. 

• a statement to the effect that the results relate only to the items tested, calibrated,

or sampled; evidence or a statement that the measurement results are traceable. 

• the name of the person(s) performing the measurements and analyses; the name, 

function, and signature of the person(s) authorizing the report. 

• an explanation of the proper use and interpretation of the reported results as 

necessary (this can be in the form of an addendum).

9. Records

A record of all measurements performed is kept in a laboratory notebook located in 

Building 245 Room C015 where the detection system is located. Software manuals, and 

binders with the detailed dimensions of all the detectors are also kept in Room C015. 
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Electronic files of all the sources measured are kept in the personal computer in the same 

location. Electronic files of the data analysis, the list of the sources used for efficiency and 

energy calibration containing the RS# and the source numbers with activities and reference 

dates along with any equipment maintenance and calibrations are kept in a personal 

computer in building 245 room C300WSAE. Electronic files are backed up daily into an 

external hard drive. Calibration reports and data files will be stored in 

68_PML/682/internal/682_Shared/CalData/682.04/43090S.

10. Filing and Retention

• Calibration printouts are stored in folders identified by company, radionuclide, 

date, and service number. If the source is returned, the date that the source is 

shipped back to the customer should be entered into the folder. 

• For customer calibration, prepare calibration report and obtain required signatures. 

Make a copy for customer file and send original. Reports created and signed 

digitally are downloaded to the calibration record in the E-commerce system. 

• Calibration Records are maintained in 245/C300-3 for at least five years. The RPD 

Quality Manager shall maintain the original and all past versions of this RPD 

Procedure.

11. References

1. IEC 61452, Nuclear Instrumentation – Measurement of gamma-ray emission 

rates of radionuclides – Calibration and use of Germanium spectrometers. 

2. Gamma Vision: GammaVisionTM (latest version), HPGe Gamma-ray spectrum 

analysis and MCA emulation, ORTEC.

3. Genie-2000: Genie-2000 Software Suite (latest version), Canberra Industries, 

Inc.

4. FitzPeaks: FitzPeaks32 Version 3.40, Gamma Analysis and Calibration 

software, Jim Fitzgerald. 

5. Decay Data Evaluation Project (DDEP). The recommended data are available 

from this website hosted and updated by the Laboratoire National Henri 

Becquerel, http://www.lnhb.fr/nuclear-data/

http://www.bipm.org/en/scientific/ionizing/radionuclides/sir/.

6. National Nuclear Data Center (NNDC), Evaluated Nuclear Structure Data File 

(ENSDF), http://www.nndc.bnl.gov/ensdf/index.jsp.

7. Taylor, Barry N., and Kuyatt, Chris E., Guidelines for Evaluating and 

Expressing the Uncertainty of NIST Measurement Results, National Institute of 

Standards and Technology Technical Note 1297 (Sep. 1994).

8. Debertin K. and Helmer R.G. Gamma- and x-ray spectrometry with 

semiconductor detector, Elsevier Science, North-Holland, 1988.
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9. ETNA, Efficiency Transfer Nuclide Activity Measurement, Laboratorie 

National Henri Becquerel, 2004.

10. GESPECOR®, Version 4.2, CID Media GmbH. 

11. XCOM: Photon Cross Sections Database. NIST Standard Reference Database 8 

(XGAM). M.J. Berger, J.H. Hubbell, S.M. Seltzer, J. Chang, J.S. Coursey, R. 

Sukumar, D.S. Zucker, and K. Olsen.

12. Eri Jay Cohen, Live Time and Pile-up Correction for Multichannel Analyzer 

Spectra. Nuclear Instruments and Methods 121 pp. 25-32, 1974.

13. Evaluation of measurement data — Guide to the expression of uncertainty in 

measurement (GUM), JCGM 100 (latest version).

14. The R Project for Statistical Computing, http://www.r-project.org/, 

(http://cran.rstudio.com/) and (https://www.rstudio.com/ide/download/desktop).

15. http://www.nist.gov/itl/sed/gsg/metrology-for-microsoft-excel.cfm.
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Annex A:

A.1. Calibration form – Request for calibration
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A.2. Example of data analysis template

This example shows the data analysis performed using both software packages (Genie2000 and Fitzpeaks). The first sheet shows the data analysis for one detector geometry.

live time 74777 sec mass 0.105858 grams

run time 75900 sec

start 11/25/13 11:53 AM EST

T1/2 Sr-82 25.35 days +/- 0.03 days T1/2 Sr-85 64.85 days +/- 0.007 days

decay factor 0.988061763 Unc +/- 2.8426E-05 decay factor 0.99531624 Unc +/- 1.0135E-06

Sr-82 (keV) error energy emis prob err em prob efficiency err eff err eff % err emprob %

776.52 0.003 0.1508 0.0016 5.18E-05 4.74E-08 0.092 1.061

1395.14 0.03 0.00529 0.00007 3.44E-05 5.02E-08 0.146 1.323

Sr-85 (keV) error energy emis prob err em prob efficiency err eff err eff % err emprob %

514.0048 0.0022 0.985 0.004 7.10E-05 1.31E-07 0.184 0.406

Reference Time = 10/31/13 12:00 PM EST DF Sr-82= 1.98068785 DF Sr-85= 1.30625

Time to reference time = -24.99514 days

Genie2k

Sr-82 (keV) area err A count rate err c rate DF corr Activity error act act/g error act/g Act ref T err Act ref T

776.52 2.1971E+05 5.0533E+02 2.9382E+00 6.7578E-03 2.9737E+00 3.8093E+05 4.1502E+03 3.5985E+06 3.9206E+04 7.5451E+05 8.2203E+03

1395.14 4.9500E+03 1.0445E+02 6.6197E-02 1.3968E-03 6.6997E-02 3.6778E+05 9.1757E+03 3.4743E+06 8.6679E+04 7.2847E+05 1.8174E+04

Sr-85 (keV) area err A count rate err c rate DF corr Activity error act act/g error act/g Act ref T err Act ref T

514.0048 3.1397E+06 1.5699E+03 4.1988E+01 2.0994E-02 4.2185E+01 6.03E+05 8.04E+03 5.70E+06 7.59E+04 7.8802E+05 1.0498E+04

Fitzpeaks

Sr-82 (keV) area err A count rate err c rate DF corr Activity error act act/g error act/g Act ref T err Act ref T

776.52 2.1990E+05 8.7962E+02 2.9407973 0.011763189 2.97632943 3.81E+05 4.34E+03 3.60E+06 4.10E+04 7.5517E+05 8.5908E+03

1395.14 5.0260E+03 1.7088E+02 0.06721318 0.002285248 0.06802528 3.73E+05 1.36E+04 3.53E+06 1.29E+05 7.3965E+05 2.7007E+04

Sr-85 (keV) area err A count rate err c rate DF corr Activity error act act/g error act/g Act ref T err Act ref T

514.0048 2.6459E+06 2.3813E+04 35.3835136 0.318451623 35.5500213 5.08E+05 5.11E+03 4.80E+06 4.82E+04 6.6408E+05 6.6701E+03
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A.3. Impurity measurement results form – Summary of impurity measurements
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A.4. Activity measurement results 

Activity measurements results are normally reported in a excel file. The information contained in this file depends on the corrections 

performed for the measurements and the required information requested by the person/manufacturer of the source. An example is

shown here.

Radionuclide Energy 

(keV)

Ampoule 

Activity 

(Bq/g)

Std 

dev 

(%)

Geom 

(%)

Decay 

factor 

(%)

Peak Fit 

(%) Eff (%)

Unc 

distance 

(%)

pile-up 

corr unc 

(%)

Emis 

Prob 

(%)

Comb 

(%)

Expand 

(%) 

k=2

Bi-211 351.03 7.481E+05 0.074 0.320 0.050 0.1 0.46 0.345 0.282 1.13 1.348 2.695

Pb-211 404.834 7.497E+05 0.186 0.101 0.050 0.2 0.50 0.345 0.282 1.23 1.437 2.873

427.15 7.604E+05 0.309 0.341 0.050 0.2 0.54 0.345 0.282 1.22 1.495 2.989

704.675 7.680E+05 0.450 0.558 0.050 0.5 0.41 0.345 0.282 1.21 1.616 3.231

766.68 7.581E+05 0.237 0.403 0.050 0.4 0.42 0.345 0.282 1.30 1.568 3.137

831.984 7.614E+05 0.274 0.383 0.050 0.2 0.37 0.345 0.282 1.16 1.395 2.791

Rn-219 271.228 7.454E+05 0.085 0.338 0.050 0.1 0.75 0.345 0.282 1.29 1.599 3.198

401.81 7.514E+05 0.110 0.299 0.050 0.2 0.35 0.345 0.282 1.36 1.524 3.048

Ra-223 122.319 7.519E+05 0.253 0.514 0.050 0.5 0.40 0.345 0.282 1.45 1.743 3.486

144.27 7.613E+05 0.031 0.368 0.050 0.4 0.50 0.345 0.282 1.43 1.672 3.345

154.208 7.618E+05 0.176 0.314 0.050 0.2 0.76 0.345 0.282 1.49 1.779 3.559

269.463 7.469E+05 0.051 0.330 0.050 0.1 0.69 0.345 0.282 1.19 1.491 2.981

323.871 7.442E+05 0.135 0.261 0.050 0.2 0.45 0.345 0.282 1.36 1.539 3.077

338.282 7.489E+05 0.182 0.257 0.050 0.2 0.48 0.345 0.282 1.53 1.705 3.409

445.033 7.523E+05 0.171 0.349 0.050 0.2 0.45 0.345 0.282 1.31 1.518 3.036
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Annex B: Information about detectors and sources

B.1. List of parameters for HPGe detectors

The list of detailed dimensions for each of the HPGe detectors is kept in binders stored in 

building 245 Room C015

B.2. Information about measurement source geometries

Below is a picture showing the different types of sources measured in this system, see 

Figure 7. The HPGe detectors are calibrated to measure point sources, 5 mL ampoules, 

disks, Marinelli beakers, gas spheres and plastic vials. For all other measurement 

geometries corrections to the measured efficiency curves need to be made to account for 

the geometrical differences. Detailed information about the dimension of the 5 mL ampoule 

is shown in Figure 8. Table 2 summarizes all the source-to-detector distances for the 

different measurement geometries.

Figure 1: Picture showing the different source types measured in the HPGe detectors

Marinelli Beakers

Point Sources

Disks

Gas Spheres

Glass Ampoules

Plastic Bottles

Plastic Vials

V-vial
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Figure 2: Dimensions of 5 mL ampoules
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Table 2: List of measurement source-to-detector distances

Geometry 

name

Point 

source

5 mL 

ampoule

Steel 

disks

Gas 

sphere

Marinelli 

beaker

B-detector source-to-detector distances (cm)

1 m 90.04 88.78 90.04

35 cm 36.24 34.98 36.24 40.49

25 cm 26.14 24.88 26.14

MB 0.36

X-detector source-to-detector distances (cm)

40cm 38.23 37.30 38.23

25cm 25.08 24.15 25.08 29.34

10cm 10.05 9.12 10.05

5cm 5.00 4.07 5.00

T-detector source-to-detector distances (cm)

90cm 82.31 81.12 82.31

45cm 42.31 41.12 42.31

35cm 32.46 31.27 32.46

25cm 22.62 21.43 22.62

MB 0.32

G-detector source-to-detector distances (cm)

90cm 90.89 89.70

40cm 40.89 39.70

20cm 20.89 19.70

10cm 10.64 9.70

N-detector source-to-detector distances (cm)

1.5 m 150 150

50 cm 50

40 cm 41.48 32.59

S-detector source-to-detector distances (cm)

5 cm 5.00 5.00
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Annex C: Detailed calculations for activity measurements

The source activity is obtained from equation (1).

A =

N(E)

Tl×ε(E)×P(E)

∏i Ci

(C.1)

where N(E) is the number of counts in the full-energy peak (or net peak area), Tl is the live 

time, (E) is the full-energy-peak efficiency, P(E) is the gamma-ray emission probability 

at the energy E, A is the source activity and Ci is the product of the correction factors, Ci, 

applied to the measurements. The correction factors that are applied to these measurements 

may include correction due to the self-attenuation, to difference in the source density, and 

the decay correction of the radionuclide during the measurement time. The uncertainty on 

the source activity is obtained using uncertainty propagation, assuming that all measured 

quantities are independent. The uncertainty for the source activity, A, is given by

uA = √(

∂A

∂N)

2

uN

2 + (

∂A

∂Tl

)

2

uTl

2 + (

∂A

∂ε)

2

uε

2 + (

∂A

∂P)

2

uP

2 + (

∂A

∂Ci

)

2

uCi

2

(C.2)

where uN, uT, u(E), uP, and uCi are the uncertainties associated with the quantities N(E), Tl, 

(E), P(E), and Ci, respectively [5, 7, 8].

The detectors are calibrated using the full-energy-peak efficiency, (E). Several fullenergy-peak efficiency curves are obtained for different source geometries and various

source-to-detector distances. The full-energy-peak efficiency curves for the high purity 

germanium (HPGe) detectors are developed using different types of gamma-ray emitting 

sources (e.g., point sources, 5 mL liquid ampoules, Marinelli beakers, plastic vials, 33 cm3

gas spheres) for energies ranging from 14 keV to 3.6 MeV. In most cases the full-energypeak efficiency to be used in the activity calculation comes from a fit to the measured 

efficiencies, in this care should be taken to the function used to fit this curve. Some of the 

most commonly used fitting functions are a polynomial or a spline, an example using a 

polynomial fit is shown in the figure below (error bars are smaller than the size of the 

symbols).
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100 1000

1E-5

1E-4

1E-3 Full-energy-peak efficiency

Energy (keV)

For better accuracy in the measurements, it is recommended to do the measurements using 

the same measurement geometry (i.e., source type, source-to-detector distance) used to 

develop the full-energy-peak efficiency curves. In the case that the source type or the 

source-to-detector distance used for the measurements is different than the one used to the 

efficiency calibration, corrections should be made to account for the changes in the source 

measurement geometry.

The determination of the net peak area is normally performed by fitting the gamma-ray 

peak with a Gaussian function with additional low-energy and high-energy tails. When 

performing this fit, care should be taken to select the function used to subtract the Compton 

background; in general, a linear or a step function is used (depending on the spectral shape). 

There are several commercially available programs that can be used to perform this fit (e.g., 

Genie 2000, GammaVisionTM, Maestro, Fitzpeak), examples are shown below. 
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C.1 Possible corrections

The most common corrections used for different gamma-ray spectrometry measurements 

using HPGe detectors are listed below. Additional corrections may be needed depending 

on the type of measurements performed [8].

C.1.1. Decay correction during measurement

If we have to determine the source activity for radionuclides with half-lives that are short 

compared to the measurement time, we need to account for the decay during the counting 

interval. It is recommended to correct at the midpoint of the counting interval, so the 

correction factor is

1

Cd

= Kd =

T1/2

ln(2)tr

(1 − e

− ln(2) tr/T1/2) (C.3)

where T1/2 is the half-life, and tr is the time interval over which the source decays, 

corresponding to the run (or real) time of the measurement.

The associated uncertainty is given by:

uKd =

1

ln(2)tr

(1 − e

− ln(2)tr/T1/2) −

1

T1/2

e

− ln(2)tr/T1/2 (C.4)

The uncertainty in the measurement time t is considered to be equal to zero as the 

acquisition system provides a measurement time value to the milli-second compared to 

source acquisition times used of approximately 6 to 24 hours.

C.1.2. Decay factor correction to a reference time

If several measurements for a given source are performed at different times and the results 

need to be combined and reported at a given reference time then the activity needs to be 

corrected, and the correction factor is 

t

df C e

−

= (C.5)

where  is the decay constant ln(2)T1/2, T1/2 is the half-life, and t is the time interval over 

which the source decays between the reference time and the measurement time, see [8].

The associated uncertainty is given by:

uCdf =

ln(2) t

T1/2

2 e

− ln(2)t/T1/2 (C.6)
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The uncertainty in the measurement time t is considered to be equal to zero as the 

acquisition system provides a measurement time value to the milli-second compared to 

source acquisition times used of approximately 6 to 24 hours.

C.1.3. Pile-up correction

If the count rate in the detector is high, pile-up may occur due to dead-time. To correct for 

this effect it is necessary to determine the loss in photopeak rate as a function of increasing 

total count rate in the detector. This needs to be verified for different gamma-ray energies. 

There are two techniques that can be used to perform this correction [8].

a. This can be accomplished by measurements with a set of sources containing known 

relative amounts of different radionuclides emitting photons with energies in the 

region of interest. Such a set of sources contains: 57Co, 133Ba, 54Mn and 65Zn with 

activity ratios of approximately 1:3:6:10:15. If no pile-up losses occur the ratios of 

the measured peak area Ni (i=1,2,...) and the activity Ai should be independent of 

the total count rate, provided that the same analyzer live-time interval Tl is chosen 

each time. For each energy, the ratios Ni/( Ai Tl) can be fitted by a linear function 

of the total count rate nt. This rate is defined as the total number of counts stored in 

the entire spectrum, Nt, divided by the live-time; that is nt = Nt / Tl. 

b. This can also be accomplished by using two sources whose activities need not be 

known. One source needs to be weak with one photon energy E1 (e.g., 137Cs) and it 

needs to be kept at a fixed position. The second source needs to be stronger and 

have gamma-rays with energies lower than E1 (e.g., 57Co), and this source is moved 

at different distances from the detector in order to change the total measured count 

rate. The count rate of the peak corresponding to the energy E1 is plotted as a 

function of nt = Nt / Tl. The data are fitted by a straight line. The correction Cp = 

1/e

-τNt

, e

-τNt ≈ 1 – τNt where τ is the slope of the linear fit [12]. 

C.1.4. Coincidence summing correction

The correction depends on the decay scheme of the radionuclide under measurement [8]. 

There are several ways to compute the magnitude of this correction. There are several 

software packages that can perform these calculations (e.g., ETNA, GESPECOR). These 

corrections are not needed if the measured radionuclides are the same as the calibration 

radionuclides and if the source-to-detector distance and source geometry are kept the same 

for the calibration and the source measurements. These corrections are a function of the 

total and full-energy-peak efficiencies; the general functional form is Cs =

1

1 ± εi

(the exact 

formula depends on the number of gamma-rays with different energies that are emitted 

within the resolving time of the spectrometer). If the efficiency values are of the order of 

10-3 then the correction will be smaller than 0.1 %. These efficiency values can be achieved 

by measuring at a faraway distance or by using small detectors. 

C.1.5. Source geometry
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If the source geometry used for the measurements is the same as the one used for the HPGe 

detector calibration, then no correction is needed. These corrections take into account the 

differences in solid angle between the source and the detector as well as the differences in 

the source-to-detector distance, attenuation through air, self-attenuation in the source and 

attenuation through any changes in possible shielding surrounding the source [9]. There 

are several software packages that can perform these calculations (e.g., ETNA, 

GESPECOR [9, 10]).

The attenuation through material (i.e., air, self-attenuation, shielding) can be corrected 

using the mass attenuation coefficients [8] as follows:

CAtt =

1

e−[(μ⁄ρ)xρ]

(C.7)

where μ/ρ is the mass attenuation coefficient (in cm2/g), x is the material thickness (in cm) 

and ρ is the material density (in g/cm3). Mass attenuation coefficients and material densities 

can be obtained from XCOM [11].

For additional information about the different corrections see reference [8].
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Annex D: Electronics settings

D.1. N-detector electronics

The Lynx electronics from Mirion/Canberra are used for the N-detector. The instrument 

settings are adjusted to optimize the detector performance. The energy calibration is 

performed after the electronics setup and regularly when found out of range. The Genie 

2000 software is used for the data acquisition for this detector. 

D.2. X-detector electronics

The ORTEC DSPEC 502/502A Digital Signal Processing Gamma Spectrometers digital 

electronics are connected to the X-detector. The electronics are adjusted to optimize the 

detector performance. The energy calibration is performed after the electronics setup and 

regularly when found out of range. The GammaVision software is used for the data 

acquisition for this detector.

D.3. T-detector electronics

The Lynx electronics from Mirion/Canberra are used for the T-detector. The instrument 

settings are adjusted to optimize the detector performance. The energy calibration is 

performed after the electronics setup and regularly when found out of range. The Genie 

2000 software is used for the data acquisition for this detector. 

D.4. B-detector electronics

The Lynx electronics from Mirion/Canberra are used for the B-detector. The instrument 

settings are adjusted to optimize the detector performance. The energy calibration is 

performed after the electronics setup and regularly when found out of range. The Genie 

2000 software is used for the data acquisition for this detector. 

D.5. G-detector electronics 

The ORTEC digital electronics DSpec-Pro are connected to the G-detector. The electronics 

are adjusted to optimize the detector performance. The energy calibration is performed 

after the electronics setup and regularly when found out of range. The GammaVision 

software is used for the data acquisition for this detector. 

D.6. S-detector electronics 

The ORTEC digital electronics DSpec jr. 2.0 are connected to the S-detector. The 

electronics are adjusted to optimize the detector performance. The energy calibration is 

performed after the electronics setup and regularly when found out of range. The 

GammaVisionTM or Maestro software is used for the data acquisition for this detector. 
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Annex E: System checks

A set of 57Co and 60Co point sources are used to check the system to ensure that the system 

performance is not changing over time. These measurements are performed monthly and 

when there is a change to the system (e.g., electronics, detector).

The full-energy peak (FEP) efficiency, the full-width-half maximum (FWHM) and the 

energy calibration is measured and recorded during this system check. If differences from 

the initial calibration measurements are observed different actions are taken depending on 

the observed difference. For example:

1) If there is a difference in the energy for the measured gamma-ray peaks, then a new 

energy calibration is performed.

2) If there is a change in the FWHM or FEP efficiency this is a sign that either the 

electronics or detector are not working properly, so the reason for the change is 

determined and fixed depending on what is found. When this occurs either the 

electronics or detector usually needs to be sent for repair.
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Annex F: Procedure revisions 

Procedure for gamma-ray spectrometry measurements for activity 

calibration and impurity measurements using High Purity Germanium 

(HPGe) detectors

Document 

version 

number

Date revised Filename Reviewed by Approved by

0.00 June 2004 ProcedureGammaSpecV0.00 Leticia Pibida Leticia Pibida

1.00 May 2014 ProcedureGammaSpecV1.00 Leticia Pibida Leticia Pibida

2.00 June 2015 ProcedureGammaSpecV2.00 Leticia Pibida Leticia Pibida

3.00 March 2020 ProcedureGammaSpecV3.00 Leticia Pibida Leticia Pibida

1.00 February 2024 Procedure 23 v1.00 Leticia Pibida Alan Thompson