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Neutron Personnel Dosimetry (44060C

and 44100S)

Purpose 

This document describes the setup, measurement, and reporting procedures for 

calibrations of neutron personnel protection devices, both active (e.g., rem balls) and 

passive (e.g., albedo dosimeters). 

Scope 

This procedure covers calibration of instruments in neutron fields having intensities 

and characteristics similar to that found in nominally occupied areas. The fields available 

are those produced by californium-252 sources, either lightly encapsulated (i.e., free field 

in air) or in the center of a 15 cm radius heavy water sphere covered with cadmium. 

Results are reported in either dose equivalent (i.e., rem or sievert) for passive instruments 

or dose equivalent rate (rem/hour or sievert/hour) for active instruments. 

Definitions 

This document does not define any new terms. 

Equipment 

The equipment used for these calibrations has five broad categorizations: 

positioning equipment, neutron sources, neutron field moderating equipment, fissionable 

deposits (in fission chambers), and data acquisition equipment. 

Positioning Equipment 

A rolling cart on fixed tracks, driven by a stepping motor, is used to modify the 

distance between the source and the detector. This cart is constructed of small quantities 

of materials having relatively low neutron scattering cross sections (i.e., aluminum and 

steel) and is a height such that various types of neutron instruments can be positioned 

above it without mechanical modification of the cart itself. 

Changes in the position of the rolling cart are measured using a tape measure

permanently attached to the floor of the calibration room. A steel indicator connected to 

the bottom of the rolling cart indicates the position of the cart to approximately 1 mm.

The indicator can be read out using a video camera attached to the cart and aimed at the 

indicator. This information, in combination with the procedure for positioning the 

instrument on the cart as described in “Positioning of Detector/Phantom,” allows the 
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absolute distance between the detector and the mechanical location of the source to be set 

to approximately 1 mm resolution. 

The sources are raised and lowered using a fishing reel and Kevlar thread. This 

allows the person raising and lowering the sources to minimize exposure to radiation. 

Mechanical positioning of bare sources is achieved using an aluminum source 

holder pictured below in Figure 1. A source attached to the Kevlar thread will snugly seat 

at the bottom of the central aluminum cylinder. The source holder is attached (indirectly) 

to the steel I-beams holding up the aluminum floor above the calibration range. 

Figure 1: Source positioning apparatus.

The height of the most standard size rem ball above the rolling cart platform is set 

using a ring stand specifically designed and constructed for this purpose. A grooved 

circular ring, pictured below as both a photograph (Figure 2) and as a mechanical 

drawing (Figure 3), holds three 19.05 mm (0.75") diameter ball bearings. The center of a 

so-called “9-inch” rem ball above the bottom of the grooved ring with the ball bearings in 

position is calculated to be 11.41 cm. Aluminum legs are attached to the ring to position 

the rem ball above the rolling table platform. The heights of the bare and D2O-moderated 

sources above the rolling table platform have been measured in the past and are 31.9 cm 

and 30.3 cm, respectively. 

All distances which impact the calibration are NIST-traceable through GEI 

International Stainless Steel Ruler Model 2020A, Serial Number C27424 (or equivalent). 

The markings on this ruler were verified on 2/4/2022 to be correct within 0.0356 mm 

(0.0014 inches) by an ANAB-accredited laboratory (the cumulative deviation between 5 
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mm to 915 mm was 0.259 mm). All other rulers used in these service IDs have been 

compared against this ruler to establish traceability.

Figure 2: Ring stand used to hold “9-inch” rem ball.
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Figure 3: Mechanical design of the rem ball ring stand. The drawing is as it was 

submitted to shops and thus has non-SI units.

Environmental effects on positioning equipment 

Positioning equipment is, in principle, subject to change of size as a function of 

temperature. Because we measure using a steel measuring tape and an aluminum meter 

stick, changes in their size could cause us to position the instruments incorrectly. Steel 

has a thermal expansion coefficient of approximately 1510-6 K

-1

, while aluminum alloys 

have a coefficient of 2310-6 K

-1

. The longest distances used in these calibrations are 

around 2.5 m, which would require a temperature change of 18 K to equal our current 

positioning uncertainty for aluminum (an even larger temperature change would be 

required to degrade our measurement for steel). The temperature of the calibration range 

is controlled to ± 5 K, so this is not a significant source of uncertainty. 

Neutron Sources

Lightly encapsulated californium-252 neutron sources are essential for 

calibrations. Characteristics of the sources used in calibrations are in Table 2 in the 

Procedures section.

Neutron Field Moderating Equipment 

The D2O Sphere is described in Reference 2. 
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The PMMA phantom is specified in ANSI N13.11. 

The ISO water slab phantom is specified in ISO 8529-3:1998, section 6.2.2. 

Data Acquisition Equipment 

Because of the wide variety of instruments we receive and the need to use their 

associated electronics as part of the testing procedure, our data acquisition system is 

heavily dependent on reading out the instruments using video cameras. These video 

cameras point to the steel indicator showing the location of the rolling cart and to the 

readout of the instrument. Additional cameras show when the source is in position and 

when it has been safely put back into storage. 

Still images of the instrument readout and cart position indicator are acquired from 

digital video cameras and saved to the hard disk of a Macintosh data acquisition 

computer. Software on the computer saves the video images at specified time intervals 

for later readout and analysis. The time at which the image was taken is encoded in the 

image file name. The accuracy of the hardware/software combination has been tested by 

recording a digital stopwatch using the software and verifying that the reported delays 

from the file name and the time from the watch image were the same within the accuracy 

of both (1 second over a 20 minute measurement). 

Fissionable deposits

Fissionable deposits (usually 235U but sometimes 239Pu or other fissionable 

isotopes) in NBS/NIST custom fission chambers can be used (almost always under 

Service ID 44100S) to characterize neutron fields. The deposits used and how to use 

them, including traceability to NIST, are described in detail in reference 7. Some other 

fissionable deposits have been calibrated by ratio measurement against one or more 

deposits described in reference 7.

Software 

Although these calibrations could, in principle, be performed with a stopwatch, 

video camera, and lab notebook, the data is, in fact, acquired, time-stamped, stored, and 

analyzed using NIST-developed software. This software is stored in a source code 

versioning system on the computer of the person who performs all calibrations and is 

backed up regularly to an external storage device and to the NIST central file servers. Use 

of the software, including selections from the source code, is described in “Appendix A: 

Source Flux Calculation & Data Analysis Software,” “Appendix B: Dosimetry Video 

Data Acquisition Software,” and “Appendix C: Video Analysis Software.”

Comments in the source code versioning system will indicate validation of new 

versions of the software. While the binary parts of the experiments are constantly 

changing as calculations are made and data entered, the source code itself should be 

stable. Only validated versions of the code will be used for calibrations. 
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Safety 

ALARA procedures are observed with guidance from the NIST Gaithersburg 

Radiation Safety Division under safety evaluation SE-0031. “Distance” and “shielding” 

(being out of the room when the source is raised) are required by SE-0031 except for 

unusual and limited circumstances. For those circumstances, “Time” (staying in the 

vicinity of the source for as little time as possible) is used to limit dose. 

Standard laboratory safety procedures for lifting detectors, minimizing contact with 

cadmium, etc., are carefully observed. 

Procedures 

Device Acceptance Criteria 

Upon receipt of customer artifacts (active or passive detectors), shipping containers 

are inspected for damage. If there is significant damage of the shipping container, the 

client is contacted as quickly as practicable and guidance requested. Otherwise, the 

shipping container is opened and the devices are inspected. For dosimeters, which are 

designed to withstand large amounts of physical abuse, the only requirements are that the 

active elements have not become detached from the protective cover and that the 

protective cover has not come apart in any way. 

For active instruments, all cable connections are tested for mechanical stability, and 

displays are checked for cracks, bent dials, etc. Then the instrument is turned on, in 

“battery/ display check” mode if available. If the instrument passes this test, it is turned 

on in the most sensitive setting available. Because the neutron background in the 

calibration range is very low, a reading above 1 μSv h-1(0.1 mrem h

-1

) is a cause for 

concern (i.e., it may indicate a malfunctioning instrument) and is discussed with the 

customer before proceeding with the calibration.

Finally, to save time on alignment and setup for instruments that are not functional 

on arrival, the instrument is exposed to a neutron field to verify that it responds. If there 

is no response to the neutrons, the customer is contacted for instructions on how to 

proceed (typically the instrument is returned to the customer for repair).

Determination of Room Return 

All calibrations covered in this Procedure are conducted in the sub-basement level 

of room B-023 in building 245 on the main NIST campus at 100 Bureau Drive in 

Gaithersburg, Maryland, USA, and the room return characteristics are for that facility. 

Room return is determined and applied as described in ISO 8529-2:2000, section 6.3.3, 

with the addition of a “quartic” term (Q in the formula below) for some source-detector 

combinations. Equation (19) from that reference, with the inclusion of the quartic term,

reads: 
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The values of S, Q and A currently in use are shown in Table 1. Instruments that do not 

appear in Table 1 can be characterized by fitting uncorrected data to the above functional 

form; this characterization is usually done within Service ID 44100S. There are 

instruments that are similar to “9 inch” remmeter but have a slightly smaller diameter, up 

to 3 cm smaller. The corrections for the “9 inch” remmeter are used for these instruments.

Changes in the arrangement of materials, especially hydrogenous materials, in the 

calibration range can in principle change the room return corrections, though the amount 

of material moved or introduced would have to be large. The person performing the 

calibration ensures that no sizeable shift of material has occurred in the room before 

starting a calibration. Moving any large pieces of material to the edge of the room away 

from the detector should eliminate any effects on room return since scattering from the 

wall of the room dwarfs any scattering from a movable piece of material. After 

significant changes to the arrangement of material in the calibration range, calibrations 

shall cease until room return corrections can be verified. 

Table 1: Room Return and Air Scatter Corrections 

Device

S (Bare) 

Quadratic 

(m–2)

A (Bare) 

Air 

Scatter 

(m–1)

S 

(Moderated) 

Quadratic 

(m–2)

Q (Moderated) 

Quartic

(m–4)

A 

(Moderated) 

Air Scatter 

(m–1)

3” sphere 33 % 1.2 % 13. % 4.5 % 

Albedo Dosimeter 20 % 1.2 % 5.4 % 3.7 % 

9” Spherical 

Remmeter 5.3 % 1.2 % 7.35 % – 0.28 % 2.6 % 

Andersson-Braun 

Remmeter 1.2 % 9.53 % – 0.51 % 2.6 % 

REM500 4 % 1.2 % 4.5 % 1.4 % 

SWENDI 5.3 % 1.2 % 4.4 % 2.6 %

PRESCILA 9.8 % 1.2 % 14.3 % -0.73 % 1.4 %

Fluence Rate Calculation 

The source emission rate is calculated with the algorithms used in Reference 3. 

Parameters for sources currently in use are shown in Table 2. Source calibrations were 

done by NIST and are traceable to the NIST reference RaBe neutron source, NBS-1. 

Sources are periodically recalibrated as resources allow. 

 

T (l)

F1(l)(1+ Al)

= RF(1+ Sl2 + Ql4 )
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Table 2: Parameters Used for Source Fluence Calculation

Source Name 

Source 

Calibration 

Date 

Calibrated

Neutron

Emission Rate 

(s-1) 

Isotopic 

Calibration 

Date 

Isotopic 

Percent 

250Cf 

Isotopic 

Percent 

252Cf 

Isotopic 

Percent 

254Cf 

NS-118 2/1/94 4.79108 2/14/85 8.16 86.26 0.021 

NS-100 9/3/13 1.91106 7/2/75 8.05 87.7 0.028 

NS-39 8/17/94 6.08106 12/20/70 10.83 84.82 0.028 

Cf-144 2/20/83 1.27107 7/27/70 9.76 84.34 0.017 

NS-130 1/10/90 4.42109 2/23/87 8.33 85.08 0.014 

NS-108 10/30/86 1.123109 9/26/77 7.736 87.726 0.039 

NBS-131 1/10/94 6.87109 9/2/92 9.22 81.99 0.018 

NBS-132 5/11/98 7.11109 8/29/96 9.36 80.98 0.01 

Source fluence rate in cm-2s

-1

is converted to dose equivalent rate using the 

conversion factors in Table 1 of reference 1; these factors are approximately 16 % higher 

than factors used before June 19, 2009, as documented in the sample report at the end of 

this procedure.

Because many of the sources have aged beyond the point anticipated by the authors 

of Reference 3, an additional correction is needed: neutron emission from 248Cm. To 

calculate this quantity, the initial mass of 252Cf in the source is determined from 

information provided by the manufacturer (see Table 3). “Purification Date” is the date 

when californium was separated from all other radionuclides, and “Emission Assay Date” 

is when the mass of 252Cf in the source on that date was determined. From the initial

252Cf mass, the current mass of 248Cm is calculated from the decay of the initial quantity

using the alpha decay branching ratio of 0.969 (reference 3). The current mass of 248Cm 

is multiplied by its spontaneous fission neutron yield of 4.04104 s

–1 mg–1 to calculate 

the 248Cm contribution to the source emission rate. 
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Table 3: Parameters Used for 248Cm Contribution to Source Emission Rate

Source Name Purification Date Emission Assay 

Date

252Cf Mass on 

Emission Assay 

Date (mg)

NS-118 12/13/83 10/22/84 2.317

NS-100 10/25/77 2/13/79 2.646

NS-39 12/17/70 11/7/71 0.929

Cf-144 10/28/70 0.1311

NS-130 1/13/88 4/25/88 3.05

NS-108 10/21/80 3/13/81 2.062

NBS-131 9/2/92 4/7/93 3.641

NBS-132 6/6/96 6/6/96 3.33

44060C: Positioning of Detector/Phantom 

The vertical distance from the rolling cart platform to the center of the source has 

been previously measured as discussed in the paragraph discussing the ring stand. The 

PMMA phantom has a specific platform on which it rests to make its center be at the 

same height as the moderated source. “9-inch” REM balls have the ring stand to set their 

position. Other detectors or phantoms are usually vertically positioned using a lab jack 

and a NIST-traceable ruler. There are other specialized positioning systems (made from 

materials with negligible impact on the neutron field) that are used for instruments that 

are not as common as the “9-inch” REM balls. For these systems instrument height is 

always checked with a NIST-traceable ruler.

The horizontal position of the detector or phantom in the direction radially away 

from the source is set by moving the rolling cart to approximately the correct position 

(e.g., such that the scale reads 15.0 cm) and then measuring the distance between the 

source position and the surface of the detector. For bare sources, the distance measured is 

from the bottom center of the central vertical aluminum tube to the detector. For 

moderated sources, the instrument is moved to be almost in contact with the moderating 

sphere (such that a piece of paper can be moved with a small amount of resistance 

between the detector and sphere, but the paper will not support its own weight). For 

calculating the source center – detector center distance, the moderating sphere is assumed 

to have a radius of 15.26 cm (e.g., a detector with radius 10 cm in near contact with the 

moderating sphere would have a source center – detector center distance of 25.26 cm) as 

described in reference 2. 

The horizontal position of phantoms and detectors in the direction perpendicular to 

the axis connecting the center of the source and the center of the detector is set by 

aligning the detector/phantom using a laser alignment system. Permanent marks on the 

walls parallel to the tracks along which the rolling cart moves are used to establish a 

plane parallel to the direction of source motion. The laser is then moved such that the 

plane of laser light passes through the center of the source (whether bare or D2Omoderated). The detector is then moved perpendicular to the direction of motion such 

that it is bisected by the plane of laser light. This alignment is done before the detector is 

positioned in the direction radially away from the source.
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Establishing Traceability of Stopwatch

The stopwatch used in irradiation of dosimeters should be traceable to standard 

time. This procedure is followed several times per year (or whenever the stopwatch is 

used in a calibration if traceability has not been established within the 120 days preceding 

use) to ensure that traceability has been established.

Approximately 10 seconds before a “memorable time” (e.g., 3:00:00 PM), a 

network-connected computer’s clock is synchronized using the Network Time Protocol to 

a NIST internal Internet Time Server. At the “memorable time”, the stopwatch is started 

and the time and identifying information for the stopwatch (e.g., serial number or unique 

id from a sticker permanently attached to the stopwatch) are recorded in the laboratory 

notebook. After at least 15 minutes, and approximately 10 seconds before another 

“memorable time” (e.g., 3:15:00 PM) the computer clock is again synchronized. When 

the computer clock reaches the “memorable time,” the stopwatch is stopped. The elapsed 

time on the stopwatch and on the NIST Internet Time Server must agree to within one 

second or the stopwatch must be replaced before starting the calibration.

Experimental Procedure - Dosimeters and Other Passive Devices 

For dosimeters, the phantom is positioned as described above in “Positioning of 

Detector/Phantom.” Strips of weather stripping (~2 mm thick foam, sticky on both sides) 

are attached to the phantom, and the dosimeters are pressed against the weather stripping 

so that they will stay in position (being careful to not move the cart or phantom in the 

process). On occasion, the dosimeters are taped from the front as well using thin packing 

tape. 

If more than one dosimeter is to be irradiated, the dosimeters are arranged in a 

circle centered on the phantom’s face, with all dosimeters oriented the same with respect 

to the center of the circle (i.e., the “top” of the dosimeter is further from the center than 

the “bottom”). SP 250–12 (reference 4, page 8) states that the source detector distance is 

calculated from the source to the circle radius; this is no longer done because the position 

of the active elements within the dosimeter is difficult to determine, and the change to the 

distance is similar in size to the uncertainty in the position of the source/position of the 

dosimeter. 

After the dosimeters are positioned and the source prepared for deployment, the 

room is scanned to verify that all sources of room return (in particular personnel) are in 

appropriate locations before the source is deployed.

As soon as the source clears the top of the storage, the stopwatch (Cole-Parmer 

Model 94410-10 or equivalent) is started. The time that the source reaches the irradiation 

position is recorded. The source is left in position until the stopwatch reads the required 

time for the requested dose. At that point, the source is lowered. The time at which the 

source reaches the top of the storage system is also recorded. Assuming that the same 

time is needed to raise and lower the source, and that the dose delivered to the dosimeters 

during raising and lowering is roughly 50 % of the source-in-position dose, this should 

yield dosimeters that have the correct dose. Both of these assumptions have associated 

uncertainties, so the dose reported to the customer is the dose delivered in position plus 

50 % of the dose that would have been delivered had the dosimeters been in position 

during raising and lowering, with uncertainty in the time the source was up being the total
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time the source was being raised and lowered. Typically this is a small contribution to the 

total uncertainty. 

Any dosimeter that falls off the phantom during irradiation is reported as spoiled to 

the customer. All dosimeters (including unirradiated, irradiated, and control dosimeters) 

are stored in the same location, which is typically in the office area outside of the low 

scatter room itself. This location is partly to mitigate any possible effect of heat on 

dosimeters; the office area temperature is regulated better than the calibration range

temperature). Because dosimeters can be sensitive to heat and are sensitive to radiation

that could in principle be coming from nearby packages, they are shipped to the customer 

overnight with care taken that they will not be in storage at a shipping company’s facility 

over a weekend. 

Experimental Procedure - Active Devices 

There are two sets of procedures for active devices, depending on whether the 

device supports “integration” mode or just “ratemeter” mode. If the device will integrate 

the dose received over a long time period (minutes to hours), higher accuracy can be 

achieved. Most digital meters can do this. 

All devices are set up such that the readout fills as much of the video screen as is 

practical. Analog meters are set up such that shadows from the indicator can be readily 

distinguished from the indicator itself on saved video images. Only images containing a 

clean and unambiguous reading of the meter are accepted for analysis; other images are 

marked in the analysis software as missing data. 

After the meter is positioned and the source prepared for deployment, the room is 

scanned to verify that all sources of room return (in particular personnel) are in 

appropriate locations before the source is deployed.

Ratemeter mode devices 

Ratemeter mode devices are positioned as described in “Positioning of 

Detector/Phantom.” A source is raised (or the readout unit is attached to an electronic 

simulator of detector signals) and the refresh rate of the instrument is observed. Readouts 

of the video camera are taken, if practicable, at a rate at least three times smaller than the

refresh rate of the meter (i.e., a delay between images at least three times longer than the 

refresh time) to avoid any correlations between readings. Typically, the meter is read out 

at a rate more than ten times smaller than the refresh rate. 

At least ten readings are taken at each dose-equivalent rate so a good estimate of 

uncertainty can be extracted from the data, even if a few of the images are unreadable due 

to changes in the readout during the video frame grab. 

Integrating Devices 

These devices are also positioned as described in “Positioning of 

Detector/Phantom.” The meter is reset and the source is then raised into position as soon 

as possible (a small amount of time is needed to allow the scientific staff to evacuate the 

calibration range). The integrated dose is read out through the video camera at a rate such 

that as many digits change on the display as possible. The integrated dose vs. time is fit to 

a line. The slope of the line is the dose rate, and the uncertainty assigned to the dose rate 
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is the confidence interval for the slope of the line at the 95 % confidence level. The 

confidence interval (for the 95 % confidence level) is calculated from the fit uncertainty 

and the Student’s T distribution. The fit uncertainty is output by the Singular Value 

Decomposition, Levenberg-Marquardt, or Markov Chain Monte Carlo software used to 

fit the data, as described in reference 5.

Stability Checks 

Although these checks are only performed at the request of the customer, the 

stability of the instrument can be checked by making repeated measurements (either in 

ratemeter mode or in integration mode) in a fixed neutron field. In ratemeter mode, 

deviations from a flat line indicate stability issues; in integration mode, curvature to the 

line can be observed. Stability issues at the level of 10 % are common. If instability is 

observed in any given instrument, the sensitivity of the instrument essentially always 

increases with received dose equivalent and appears to follow an exponentially 

asymptotic functional form with either time or dose equivalent. 

A less informative stability check is to move the meter back to a previously 

measured point and re-measure the calibration factor at that point. This will often reveal 

the same level of instabilities as the above check.

Procedures for Special Tests under Service ID 44100S

Most calibrations of instruments and dosimeters are performed under Service ID 

44060C, but customers frequently have needs for non-standard calibrations. These 

special tests can be grouped into three broad categories: (1) calibration/irradiation of an 

artifact for which the room-return characteristics have not previously been measured, (2) 

calibration/irradiation of an artifact using an unusual field (such as the neutron field 

produced by an 241AmBe source), and (3) measuring characteristics of an unknown 

neutron field using fission chambers (with possible calibration/irradiation after the field 

has been characterized).

The first of these categories has already been discussed and is documented in 

reference 4. Measurements of instrument reading are collected as a function of sourcedetector distance and fit (using Levenberg-Marquardt, Singular Value Decomposition, or 

Markov Chain Monte Carlo algorithms) to the functional form in the first formula in the 

section on Determination of Room Return to extract the terms used to correct for room 

return. The corrections are applied to the existing data and a calibration report that is 

similar to a standard Service ID 44060C calibration report is provided to the customer.

The second category of special tests is when calibrations/irradiations are performed 

in one of the standard fields described in ISO 8529-x, but using a field that is not 

regularly used at NIST. In this case the guidance from ISO 8529-x (including 

particularly any spectrum-averaged fluence to dose equivalent conversion factor) is used 

to calculate the field characteristics at the point of test, and the response of the instrument 

in that calculated field is reported. Measurements of room-return response may be 

needed, depending on whether an instrument identical or similar to the device under test 

has previously provided a reliable characterization of room-return parameters.

The third category of special tests is when a not-well-known or unknown neutron 

field must be characterized. This is often a prerequisite for calibration/irradiation of a 
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detector, such as when a cold or thermal neutron beam produced at a reactor must be 

characterized to allow calibration/irradiation of a detector in the characterized field. This 

process (including uncertainties) is described in detail in reference 8 and is specifically 

documented in calibration reports.

Quality Assurance Practices

For active detectors, quality assurance is achieved through two different activities. 

First, there is an internal consistency check in the fact that a given instrument is 

calibrated at multiple distances from multiple sources, which provides calibrations at 

multiple dose equivalent rates (typically two to three sources, with two to three distances 

for each source). Although an instrument might perform differently at different dose 

equivalent rates, most instruments submitted perform the same at all dose-equivalent 

rates, within statistical uncertainty. Significant non-statistical deviations in calibrations 

would trigger a check of whether, for instance, a source had become compromised, or a 

clock was not functioning properly. Second, the consistency of calibrations for returning 

instruments is checked, as resources allow.

For both active and passive detectors, the Radiation Physics Division participates in 

appropriate national and international comparisons.

Uncertainty Analysis

The basis for the determination of uncertainties associated with the calibration of 

neutron personnel dosimetry devices is found in reference 6. Uncertainties specific to the 

type of device (active or passive) are discussed above (see “Experimental Procedure -

Dosimeters and Other Passive Devices” and “Experimental Procedure - Active 

Devices”). Our uncertainties (and central values) are periodically verified in 

measurement comparisons with other National Measurement Institutes, as specified in 

RPD-QM-II, section 4.2.2.2. 

Source strength uncertainties are derived from source strength calibrations. These 

uncertainties are Type B and are consistent for all measurements using a given source. 

Room return correction uncertainties are a fixed fraction of the room return 

correction and are Type B. See reference 4 for a discussion of the derivation of this 

uncertainty. See Table 1 in Appendix D for the fraction of the correction taken to be the 

uncertainty.

Source-detector distance uncertainties are dominated by the uncertainty in the 

position of the effective center of the instrument (see reference 4 for details and Table 1 

of Appendix D for the value), but they include a small contribution (1 mm) from 

uncertainty in the readout of distance and the measurement of source-detector distance 

during initial positioning. Because the relationship of dose-equivalent rate to sourcedetector distance goes as the inverse square, this uncertainty must be carefully 

propagated. This uncertainty is Type B. 

Uncertainty in the conversion from neutron fluence rate to dose equivalent rate

is described in reference 4. Numerical values for these uncertainties (bare and moderated 

252Cf are different) are given in Table 1 of Appendix D. 
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Instrument stability, as described at the end of section “Experimental Procedure -

Active Devices,” can be measured and reported to the client but is not added to the total 

uncertainty. This is because the way in which the calibrated instrument is used by the 

client may eliminate this uncertainty (i.e., if it is used as a field instrument this 

uncertainty will probably not manifest itself). 

A more thorough discussion of uncertainty is given in “Appendix D: Uncertainty 

Analysis.” The full uncertainty analysis can be gleaned from the source code selections 

in “Appendix A: Source Flux Calculation & Data Analysis Software.” 

Records

Procedures Specific to Dosimeters and Other Passive Devices

For passive instruments, raw data is recorded by hand in a laboratory notebook. 

Data are recorded and maintained as specified in RPD-G-06 and section 4.3.4.2 of RPDQM-II. Paper laboratory notebooks containing these data are kept in building 245, room 

B021; electronic laboratory notebooks (or equivalent) are edited on a local computer and 

archived on the NIST central file servers.

Procedures Specific to Active Devices

Raw data files (screen dumps) are copied from the data acquisition machine to 

removable storage as quickly as possible after acquisition and from removable storage to 

the desktop computer of the staff member performing analysis. These files may be 

moderately processed before copying (e.g., cropping the images to remove unneeded 

backgrounds, file format conversion) but not in a way that will visibly degrade the image.

A file containing the transcribed video data and derived averages and uncertainties 

in those averages is generated as part of the analysis. This file is stored in the appropriate 

folder on the desktop computer of the staff member performing the analysis. See 

“Appendix C: Video Analysis Software” for more information about this intermediate 

file.
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References 

1. International Organization for Standardization, Reference neutron radiations-part 

1: characteristics and methods of production. ISO 8529-1 (ISO: Geneva) (2001).

2. R.B. Schwartz and C.M. Eisenhauer, The Design and Construction of a D2OModerated 252Cf Source for Calibrating Neutron Personnel Dosimeters Used at 

Nuclear Power Reactors, NUREG/CR-1204, January, 1980. 

3. NBS Measurement Services: Neutron Source Strength Calibrations at NBS by the 

Manganese Sulfate Bath Method, E. D. McGarry and E. W. Boswell, Natl. Bur. 

Stand. (U.S.), Spec. Publ. 250–18 (Mar. 1988), Appendix C.

4. NBS Measurement Services: Neutron Personnel Dosimetry, R. B. Schwartz, Natl. 

Bur. Stand. (U.S.), Spec. Publ. 250–12 (July 1987).

5. Igor Pro Manual, available from www.wavemetrics.com with purchase of 

software. 

6. NIST Technical Note 1297, Guidelines for Evaluating and Expressing the 

Uncertainty of NIST Measurement Results.

7. ANL/NDM-118, Characteristics of the Samples in the FNG Fission Deposit 

Collection, J.W. Meadows, Argonne National Laboratory, Argonne, Illinois, 

60439 (December 1990)

8. J. A. Grundl, D. M. Gilliam, N. D. Dudey, and R. J. Popek. "Measurement of 

absolute fission rates." Nuclear Technology 25, no. 2 (1975): 237-257.

Filing and Retention

Calculations associated with a calibration, as well as electronic copies/scans of 

reports and any pertinent data (including electronic laboratory notebooks or equivalent 

and image files), are kept in directories on the NIST central file servers. To be specific, 

this is the elwood file server, and the root for Neutron Physics Group data is 

smb://elwood.nist.gov/68_PML/682/internal/682_Shared/CalData/682.03. Within that 

root directory there are subdirectories for each calibration service ID or SKU, and within 

the SKU directories are subdirectories for each fiscal year in which a calibration was 

started, and within each fiscal year directory are subdirectories for each calibration. 

(Because some calibrations have mixed SKUs, symbolic links or aliases are used to allow 

the calibration to be found via either SKU.) These directories are identified with the year 

and month of the calibration (starting date) and the name of the institution submitting the 

detectors. Calculations and analysis data are stored in Igor Text Format (.itf), which can 

be easily reloaded into Igor for later checks but are also human readable. These files are 

backed up from the analysis computer within a week of when they are changed and are 

maintained for at least as long as the valid time of the report as specified on the 

calibration folder (usually three years).

After all required signatures have been obtained, the original of the report is sent to 

the customer. A scan or copy of the final signed report is placed into the calibration 

directory. An electronic scan or copy of the final report is uploaded to the eCommerce 

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

RPD Procedure. 
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Appendix A: Source Flux Calculation & 

Data Analysis Software

Overview 

An Igor experiment file is used to calculate fluence rates, plan experiments, and 

analyze data (after basic averaging has already been done by the Video Analysis 

experiment described in “Appendix C: Video Analysis Software”). The experiment and 

associated code are mirrored onto the NIST central file server elwood in the 

68_PML/682/internal/682_Shared/CalData/682.03/44060C/SourceFluxCalc directory 

after each significant update (such as completion of a calibration).

Usage 

Planning 

Planning an experiment is done by bringing to the front either the “PlanTable” table 

or the “PlanTableDosimeter” table (depending on whether the calibration is for an active 

or passive instrument). Conversion and correction factors are set by entering 

“convAndCorr = convAndCorr9inMod” (or another appropriate conversion and 

correction wave, depending on the source and detector) on the command line. The values 

desired for dose equivalent rate or dose are entered into the appropriate columns (note: all 

columns requiring user input appear in bold) and “DoPlanCalib” or 

“DoPlanCalibDosimeter” are selected from the Macros menu, as appropriate. 

Planning for Active Instruments 

The source chosen for a given rate can be modified to keep the source surfacedetector surface distance (D_SS) and background correction (CorrPCT) in reasonable

ranges. Ideally, D_SS should be more than 5 cm (10 cm for bare sources), but the only 

requirement is that D_SS be greater than or equal to zero. Corrections, ideally, should be 

less than 10 %; they must be less than 40 %. 

D_SS, coupled with the knowledge of the relationship between the position of the 

instrument and the scale reading, allows the user to determine scale positions for each 

requested dose equivalent rate. 

Planning for Dosimeters 

Because the distance between the source center and phantom surface is set to be 50 

cm, only the irradiation time and source can be adjusted. A source is chosen such that the 

irradiation time is significantly longer than the raising and lowering time of the source, 

ideally by a factor of 100 or more

Analysis 
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For both types of instruments, the tables “AnalysisTable” and 

“AnalysisTableUncert” are brought to the front of the screen. 

Active Instruments 

The actual scale distances and instrument reading are entered into the appropriate 

(boldface) columns. D_SS is calculated on the command line from the positioning 

measurements. For data taken using the method specified in “Integrating Devices,” the 

number of measurements taken during each integration is also entered. 

Raw uncertainties are entered into the (boldface) “dReadingAbs” column in the 

“AnalysisTableUncert” table. “dReading” (in percent) is calculated on the command 

line from dReadingAbs and Reading. 

The macro “CrunchCalibNew” is used to analyze the data, and produces a 

summary of results in the history area. This macro takes one argument, which is one 

for data taken with integrating active devices, and zero for ratemeter devices. 

Dosimeters 

For dosimeters, the time during which the source is in position (i.e., subtracting the 

raising and lowering time) is entered into “TimeUp”, and the sum of the raising and 

lowering time should be entered into “dTimeUp”. After running the 

“CrunchCalibDosimeter” macro, the user should verify that D_CC is 50 cm, and D_SS is 

appropriate for the source (bare or moderated) in use. The wave “RealDose” will contain 

the total dose received by the dosimeter corrected for room-return and air scatter 

backgrounds.
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Source Code 

Selections from the source code are presented below for information. 

Function/D NActivity(Name, month, day, year)

String Name;

variable/d month,day,year

variable index;

variable answer; // create so can stuff info into isoNeuts wave.... -- akt 20150930

WAVE CfActNeutrons = root:cfCalibFolder:CfActNeutrons // -- akt 20150930

WAVE isoNeuts = root:cfCalibFolder:isoNeuts // -- akt 20150930

NVAR cfSourceCalibDate = root:cfCalibFolder:cfSourceCalibDate

NVAR cfSourceCalibVal = root:cfCalibFolder:cfSourceCalibVal

NVAR CfAtomCompCalibDate = root:cfCalibFolder:CfAtomCompCalibDate

WAVE CfActivityACC = root:cfCalibFolder:CfActivityACC

WAVE CfAtomCompCalib = root:cfCalibFolder:CfAtomCompCalib

WAVE sourceAtomComps = root:cfCalibFolder:sourceAtomComps

WAVE sourceCalibDates = root:cfCalibFolder:sourceCalibDates

WAVE sourceCalibFluence = root:cfCalibFolder:sourceCalibFluence

WAVE atomCompDates = root:cfCalibFolder:atomCompDates

WAVE CfNus = root:cfCalibFolder:CfNus

WAVE CfHalfLives = root:cfCalibFolder:CfHalfLives

WAVE CfAlphaSFRatios = root:cfCalibFolder:CfAlphaSFRatios

WAVE CfActivitySC = root:cfCalibFolder:CfActivitySC

WAVE/T sourcenames = root:cfCalibFolder:sourcenames

WAVE mgCf252onAssayDate = root:cfCalibFolder:mgCf252onAssayDate;

WAVE mgCf252EmisAssayDates = root:cfCalibFolder:mgCf252EmisAssayDates;

WAVE mgCf252FinalPurifDates = root:cfCalibFolder:mgCf252FinalPurifDates;

WAVE cm248emissionEstimate = root:cfCalibFolder:cm248emissionEstimate;

// find which source this is in the list -- index then will find all other information about the source

index = FindStringInWave(sourcenames,Name)

if( index < 0) 

return(NaN)

endif

CfAtomCompCalib[] = sourceAtomComps[index][p];

Renorm(CfAtomCompCalib); // make the isotopic composition add up to 100%

cfSourceCalibDate = sourceCalibDates[index];

// the "2^((mgCf252EmisAssayDates-mgCf252FinalPurifDates)/CfHalfLives[1])" term is to correct the Cf back to the purification date 

from the (estimated) Cf on the Assay date (assay date is usually on the source cert)

// the "0.969*(1-2^(-(cfSourceCalibDate-mgCf252FinalPurifDates)/CfHalfLives[1]))" term converts the mgCf252onPurificationDate (the 

result of the first term, and when there was only Cf-252 and no Cm-248) into Cm-248

// the "0.969" is the branching fraction for alpha decay (and hence from Cf-252 to Cm-248)

// 4.04e4 is the specific activity of Cm-248 in neutrons per mg

cm248emissionEstimate = 4.04e4*mgCf252onAssayDate * 2^((mgCf252EmisAssayDates-mgCf252FinalPurifDates)/CfHalfLives[1]);

// cm248emissionEstimate *= 0.969*(1-2^(-(cfSourceCalibDate-mgCf252FinalPurifDates)/CfHalfLives[1])); -- was 20131202

cm248emissionEstimate *= 0.969*(1-2^(-(date2secs(year,month,day)-mgCf252FinalPurifDates)/CfHalfLives[1]));

cfSourceCalibVal = sourceCalibFluence[index]-cm248emissionEstimate[index];

CfAtomCompCalibDate = atomCompDates[index];

// this is on atomic calibration date

CfActivityACC = (ln(2)*CfNus*CfAtomCompCalib/(CfHalfLives*(CfAlphaSFRatios+1))) 

// this is on source strength calibration date

CfActivitySC = CfActivityACC*exp(-ln(2)*(CfSourceCalibDate-CfAtomCompCalibDate)/CfHalfLives)

// added 20100614t110055, not yet compatible with quality manual

answer = Activity(month,day,year)+cm248emissionEstimate[index]

isoNeuts = cfActNeutrons;

isoNeuts[3] = cm248emissionEstimate[index];

return(answer)

End

Function/D Activity(month, day, year)

variable/d day,month,year

make/n=3/o/d cfAct

NVAR CfSourceCalibDate = root:cfCalibFolder:CfSourceCalibDate

NVAR cfSourceCalibVal = root:cfCalibFolder:cfSourceCalibVal

WAVE CfActivitySC = root:cfCalibFolder:CfActivitySC

WAVE CfActNeutrons = root:cfCalibFolder:CfActNeutrons
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WAVE CfHalfLives = root:cfCalibFolder:CfHalfLives

CfAct[] = CfActivitySC[p]*exp(-ln(2)*(date2secs(year,month,day)-CfSourceCalibDate)/CfHalfLives[p]);

cfAct = CfActivitySC*exp(-ln(2)*(date2secs(year,month,day)-CfSourceCalibDate)/CfHalfLives)

// print sumwave(cfAct), sumwave(cfactivitySC), cfSourceCalibVal

variable answer = cfSourceCalibVal*SumWave(cfAct)/SumWave(cfActivitySC);

CfActNeutrons = cfAct*answer/sumwave(CfAct);

return( answer );

End

Macro CrunchCalibNew(LinAnalysis )

variable LinAnalysis=0;// was the data taken in integral mode and fit to a line? 0: no, 1: yes-- akt 20030709-1515

variable whichSource=-1;

variable WeightedUncert;

String fldrSav= GetDataFolder(1)

SetDataFolder root:InstrCalibAnalysis:

SourceFluence = NActivity(sourceName, mmonth, mday, myear)

D_CC = D_SS - convAndCorr[1]

FFDE = SourceFluence*convAndCorr[0]/(D_CC)^2

CorrPct = convAndCorr[2]*D_SS/100 + convAndCorr[3]*(D_CC/100)^2 + convAndCorr[4]*((D_CC/100)^4 ) 

// non-point correction, added 8/13/98

CorrPct += 100*convAndCorr[5]/(4*D_CC^2);

RealDose = FFDE*(1 + CorrPct/100)

CalFac = RealDose/Reading

// multiply everything by two here to adhere to new NIST policy -- AKT 8/20/97

//•dQ = 2*1.2

// look up source uncertainties in wave

dQ = 2*root:cfCalibFolder:uncert[FindStringInWave(root:cfCalibFolder:tsources, sourceName)]*dReadingAbs/dReadingAbs

dCorr = 2*CorrPct/5

// next line is a hack to get index for sourceName in "sourceType" wave -- akt 20220818

dConv = FindStringInWave(root:cfCalibFolder:sourceNames, sourceName); // *dReadingAbs/dReadingAbs why was this here? it's in 

the next line... --akt 20151203

dConv = 2*(dReadingAbs/dReadingAbs)*(1 + 

(abs(cmpstr(root:cfCalibFolder:sourcetype[dConv],"bare",0)*cmpstr(root:cfCalibFolder:sourcetype[dConv],"AmBe",0)))*3)

// 20220818 updated formula above to include support for AmBe, which has uncertainties similar to bare -- AKT 8/18/2022

// change formula for "dDists" to reflect source of uncertainty better; dR/R is 0.5 cm. -- AKT 12/9/98

// "2" in there is because it goes as r^2 -- akt 20021001 1317

dDists = (2*0.5/D_CC)*100

// dCorr *= ( D_SS < 3 ? 9.0 : 1.0) 

dTotalCorrelated = sqrt(dQ^2 + dCorr^2 + dConv^2);

if( LinAnalysis ) // if linear analysis, dReading's are k=2 confidence intervals already, propogate-- akt 20031201-1137

dTotalUncorrelated = sqrt(dDists^2 + dReading^2); // -- akt 20030709-1515

else // otherwise, dReading's are standard deviations of data and need to be turned into confidence intervals -- akt 20031201-1137

// line below was only choice before; not sure why dReading is where it is -- akt 20030709-1515

dTotalUncorrelated = StudentT(erf(2/sqrt(2)),NumMeas)*sqrt(dDists^2 + dReading^2)/sqrt(NumMeas);

endif

dTotal = sqrt(dTotalCorrelated^2 + dTotalUncorrelated^2)

print "SourceFluxCalcProc $LastChangedRevision: 4289 $";

if(LinAnalysis == 0 ) // data taken in ratemeter mode -- akt 20060522

print "Did you remember to multiply dReading by 200?"

else

print "Did you remember to multiply dReading by ONLY 100?"

endif

// CalcMeanCalib(dTotalCorrelated, dTotalUncorrelated, 1) calculates the "average" correlated uncertainty -- akt 20021001 1840

// "4*" removed -- akt 20031201 1123 WeightedUncert = sqrt(4*CalcMeanCalib(CalFac, dTotalUncorrelated, 0)^2 + 

CalcMeanCalib(dTotalCorrelated, dTotalUncorrelated, 1)^2);

WeightedUncert = sqrt(CalcMeanCalib(CalFac, dTotalUncorrelated, 0)^2 + CalcMeanCalib(dTotalCorrelated, dTotalUncorrelated, 

1)^2);

make/o/n=6/t exportVarNames

make/o/n=6 exportVarMins, exportVarMaxs

variable whichExportVar=0;

print "Weighted Average Calibration Factor is ",CalcMeanCalib(CalFac, dTotalUncorrelated, 1)," ± ",WeightedUncert," %"

// exportVarNames[whichExportVar] = "AverageCalFac"; exportVarMins[whichExportVar] = CalcMeanCalib(CalFac, dTotalUncorrelated, 

1); exportVarMaxs[whichExportVar] = WeightedUncert; was -- akt 20110211

exportVarNames[whichExportVar] = "AverageCalFac"; exportVarMins[whichExportVar] = CalcMeanCalib(CalFac, dTotalUncorrelated, 

1); exportVarMaxs[whichExportVar] = WeightedUncert*exportVarMins[whichExportVar]/100.;

whichExportVar += 1;

wavestats/q CalFac

print "Statistical Average Calibration Factor is ",V_avg, " ± ", 200*V_sdev/(V_avg*sqrt(V_npnts))," %"

wavestats/q CorrPct

print "Corrections range from ", V_min, " to ", V_max

exportVarNames[whichExportVar] = "ScatterCorr"; exportVarMins[whichExportVar] = V_min; exportVarMaxs[whichExportVar] = 

V_max;

whichExportVar += 1;

wavestats/q dReading

// was -- akt 20060522 print "Type A uncertainties range from ", 2*V_min, " to ", 2*V_max

print "Type A uncertainties range from ", V_min, " to ", V_max
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exportVarNames[whichExportVar] = "UncertTypeA"; exportVarMins[whichExportVar] = 2*V_min/2; exportVarMaxs[whichExportVar] = 

2*V_max/2; // don't double double uncerts, for fit you have k=2, for ratemeter you already multiplied by 2

whichExportVar += 1;

wavestats/q dQ

print "Source uncertainties range from ", V_min, " to ", V_max

exportVarNames[whichExportVar] = "UncertSourceStrength"; exportVarMins[whichExportVar] = V_min; 

exportVarMaxs[whichExportVar] = V_max;

whichExportVar += 1;

wavestats/q dCorr

print "Correction uncertainties range from ", V_min, " to ", V_max

exportVarNames[whichExportVar] = "UncertScatterCorr"; exportVarMins[whichExportVar] = V_min; exportVarMaxs[whichExportVar] 

= V_max;

whichExportVar += 1;

wavestats/q dDists

// print "Distance uncertainties range from ", 2*V_min, " to ", 2*V_max

// exportVarNames[whichExportVar] = "UncertLocation"; exportVarMins[whichExportVar] = 2*V_min; exportVarMaxs[whichExportVar] = 

2*V_max;

// prior lines incorrect -- 0.5 cm *2 /D_CC is k=2 uncertainty

print "Distance uncertainties range from ", V_min, " to ", V_max

exportVarNames[whichExportVar] = "UncertLocation"; exportVarMins[whichExportVar] = V_min; exportVarMaxs[whichExportVar] = 

V_max;

whichExportVar += 1;

print ""

dTotalAbs = dTotal*CalFac/100 // added by akt 20220908 because I always do it by hand

SetDataFolder fldrSav

End

Macro CrunchCalibDosimeter()

variable whichSource=-1;

String fldrSav= GetDataFolder(1)

SetDataFolder root:InstrCalibAnalysis:

SourceFluence = NActivity(sourceName, mmonth, mday, myear)

//D_CC = D_SS - convAndCorr[1]

//D_CC = 50

print "Not setting D_CC today"

D_SS = D_CC + convAndCorr[1]

FFDE = SourceFluence*convAndCorr[0]/(D_CC)^2

CorrPct = convAndCorr[2]*D_SS/100 + convAndCorr[3]*(D_CC/100)^2 + convAndCorr[4]*((D_CC/100)^4 )

RealDose = FFDE*(1 + CorrPct/100)

Reading = RealDose*(TimeUp + 0.5*dTimeUp)/3600

FFDE *= (TimeUp + 0.5*dTimeUp)/3600

CalFac = RealDose/Reading

// multiply everything by two here to adhere to new NIST policy -- AKT 8/20/97

//•dQ = 2*1.2

// look up source uncertainties in wave

dQ = 2*root:cfCalibFolder:uncert[FindStringInWave(root:cfCalibFolder:tsources, sourceName)]*Reading/Reading

dCorr = 2*(Reading/Reading)*CorrPct/5

dDists = 2*(Reading/Reading)*(1.0/D_CC)*100

dConv = FindStringInWave(root:cfCalibFolder:sourceNames, sourceName)

dConv = 2*(1 + (abs(cmpstr(root:cfCalibFolder:sourcetype[dConv],"bare")))*3)*(Reading/Reading)

dReading = 2*100*dTimeUp/TimeUp;

dTotalCorrelated = sqrt(dQ^2 + dCorr^2 + dConv^2 + dDists^2);

dTotalUnCorrelated = sqrt(dReading^2);

dTotal = sqrt(dQ^2 + dCorr^2 + dDists^2 + dReading^2 + dConv^2)

dTotalAbs = dTotal*Reading/100;

print "All uncertainties are k=2"

wavestats/q CorrPct

print "Corrections range from ", V_min, " to ", V_max

wavestats/q dReading

print "Irradiation time uncertainties range from ", V_min, " to ", V_max

wavestats/q dQ

print "Source uncertainties range from ", V_min, " to ", V_max

wavestats/q dCorr

print "Correction uncertainties range from ", V_min, " to ", V_max

wavestats/q dDists

print "Distance uncertainties range from ", V_min, " to ", V_max

print ""

SetDataFolder fldrSav

End

Function PlanCalibDosimeter()

WAVE SourceFluence = root:InstrCalibAnalysis:SourceFluence

WAVE D_CC = root:InstrCalibAnalysis:D_CC

WAVE CorrPct = root:InstrCalibAnalysis:CorrPct

WAVE D_SS = root:InstrCalibAnalysis:D_SS

WAVE convAndCorr = root:InstrCalibAnalysis:convAndCorr

WAVE RealDose = root:InstrCalibAnalysis:RealDose
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WAVE mmonth = root:InstrCalibAnalysis:mmonth

WAVE mday = root:InstrCalibAnalysis:mday

WAVE myear = root:InstrCalibAnalysis:myear

WAVE FFDE = root:InstrCalibAnalysis:FFDE

WAVE TimeUp = root:InstrCalibAnalysis:TimeUp

WAVE Reading = root:InstrCalibAnalysis:Reading

WAVE/T sourceName = root:InstrCalibAnalysis:sourceName

Variable i=0

SourceFluence = NActivity(sourceName, mmonth, mday, myear)

// D_CC = 50

print "Not setting D_CC today"

D_SS = D_CC + convAndCorr[1]

FFDE = SourceFluence*convAndCorr[0]/(D_CC)^2

CorrPct = convAndCorr[2]*(D_CC + convAndCorr[1])/100 + convAndCorr[3]*(D_CC/100)^2 + convAndCorr[4]*((D_CC/100)^4 )

CorrPct += 100*convAndCorr[5]/(4*D_CC^2); // non-point correction added 5/28/02

RealDose = FFDE*(1 + CorrPct/100)

TimeUp = 3600*Reading/RealDose

End

Function PlanCalib() 

WAVE SourceFluence = root:InstrCalibAnalysis:SourceFluence

WAVE D_CC = root:InstrCalibAnalysis:D_CC

WAVE CorrPct = root:InstrCalibAnalysis:CorrPct

WAVE D_SS = root:InstrCalibAnalysis:D_SS

WAVE convAndCorr = root:InstrCalibAnalysis:convAndCorr

WAVE RealDose = root:InstrCalibAnalysis:RealDose

WAVE mmonth = root:InstrCalibAnalysis:mmonth

WAVE mday = root:InstrCalibAnalysis:mday

WAVE myear = root:InstrCalibAnalysis:myear

WAVE FFDE = root:InstrCalibAnalysis:FFDE

WAVE/T sourceName = root:InstrCalibAnalysis:sourceName

Variable i=0

SourceFluence = NActivity(sourceName, mmonth, mday, myear)

D_CC = sqrt( SourceFluence*convAndCorr[0]/RealDose )

for( i= 0; i< 25; i+=1)

CorrPct = convAndCorr[2]*(D_CC + convAndCorr[1])/100 + convAndCorr[3]*(D_CC/100)^2 + convAndCorr[4]*((D_CC/100)^4 )

CorrPct += 100*convAndCorr[5]/(4*D_CC^2); // added - akt 6/8/01

D_CC = sqrt( SourceFluence*convAndCorr[0]*(1 + CorrPct/100)/RealDose)

endfor

D_SS = D_CC + convAndCorr[1]

FFDE = SourceFluence*convAndCorr[0]/(D_CC)^2

CorrPct = convAndCorr[2]*(D_CC + convAndCorr[1])/100 + convAndCorr[3]*(D_CC/100)^2 + convAndCorr[4]*((D_CC/100)^4 )

CorrPct += 100*convAndCorr[5]/(4*D_CC^2); // non-point correction added 5/29/01

RealDose = FFDE*(1 + CorrPct/100)

End
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Appendix B: Dosimetry Video Data 

Acquisition Software

Overview 

This is the code used to acquire data from the video frame grabber. It starts the 

frame grabber software and takes data as specified on the command line. It is stable 

(i.e. neither maintenance nor updating are needed) with the current hardware setup but 

any changes would be tracked using the git software versioning system on the low 

scatter data acquisition machine. This software is mirrored onto the NIST central file 

server elwood in the 

68_PML/682/internal/682_Shared/CalData/682.03/CommonFiles/LowScatterDataAcq

directory and changes would be promptly mirrored as well.

The variables $beforeAfterDiff and $beforeAfterFrac allow data to be taken at 

precise intervals, but these depend on the system configuration. Since such precision is 

only occasionally needed, these are not available as command line options. Validation of 

these values will be done before any experiment requiring their modification, with the 

validation procedure and documentation to be entered into the laboratory notebook. 

Source Code 

#!/usr/bin/perl -w

#

# Take a bunch of screen grabs and save them in descriptive file names

#

use Getopt::Long;

use File::Path;

use Cwd 'abs_path';

my $pause = 10;

my $delay = 60;

our $howLongToSleep = $delay;

our $howmany = 10;

my $basename = '100mr';

my $destdir = '.';

my $printhelp = '';

my $printexample = '';

my $timesArray = '';

our @atTimes;

GetOptions( 'pause:i' => \$pause,

'delay:i' => \$delay,

'howmany:i' => \$howmany,

'basename:s' => \$basename,

'destdir:s' => \$destdir,

'help|usage' => \$printhelp,

'example' => \$printexample,

'timesarray:s' => \$timesArray

) or die("unknown option");;

if( $printhelp )

{

print "DosimDAQ [--pause seconds] [--delay seconds] [--howmany numImages]\n";

print " [--basename fileBaseName] [--destdir destination_directory] [--example]\n";

print " [--timesarray perlSource]\n";

exit;

}
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if( $printexample )

{

print "/Users/akt/Documents/LowScatterDataAcq/DosimDAQSS.pl --delay 60 --howmany 12 --destdir ./mod/ --basename 100mr\n";

print "/Users/akt/Documents/LowScatterDataAcq/DosimDAQSS.pl --timesarray '((30) x 3, (60) x 3, (100) x 3)' --destdir ./mod/ --

basename 100mr\n";

print '/Users/akt/Documents/LowScatterDataAcq/DosimDAQSS.pl --timesarray \'my @foo = (30) ; foreach (0..21) {push @foo, int 

($foo[-1]*1.1);} ; @foo\' --destdir ./mod/ --basename 100mr'."\n";

exit;

}

if( $timesArray )

{

@atTimes = eval($timesArray);

# exit;

# example : --timesarray '((30) x 3, (60) x 3, (100) x 3)'

# example : --timesarray 'my @foo = (30) ; foreach (0..21) {push @foo, int ($foo[-1]*1.1);} ; @foo'

}

else

{

@atTimes = eval "(($delay)x$howmany)"; 

}

my $sum=0;

foreach(@atTimes)

{

 $sum += $_;

}

print join(",",@atTimes)."\n";

#exit;

print "Total time for measurements approximately $sum seconds\n";

$delay = $atTimes[0];

$howmany = scalar(@atTimes)+1;

if (open PowMgmt,"/private/var/db/SystemConfiguration/com.apple.PowerManagement.xml")

{

while(<PowMgmt>)

{

if( m/.key.Display Sleep Timer.\/key./ )

{

$nextline = <PowMgmt>;

$nextline =~ m/>([0-9]+)</;

unless( $1 == 0 )

{

print "\007\007\007";

print "Display sleep may kill DAQ\n";

}

}

}

}

# was system('open /XLR8\ Folder/Interview/InterView\ Capture'); -- akt 20080623t101700

#system('open /Applications/InterView/InterView\ Capture');

system('open /Applications/SecuritySpy.app');

sleep $pause; 

#print "(2) $pause, $delay, $howmany, $basename, $destdir\n";

#$howmany--;

# print "Destdir is (1) $destdir\n";

$destdir =~ s{/+\s*$}{}g;

$destdir = abs_path($destdir);

# print "Destdir is $destdir\n";

mkpath($destdir, 1, 0755);

die "No files will actually be written, so I'm quittin'\n" unless -d $destdir;

our $beforeAfterDiff = 0; # was 1 -- akt 20121016t1028 was 5 -- akt 20080623t101544

our $beforeAfterFrac = 0; # was -0.48; -- akt 20121016t1028

if(0)

{

my $howManyFoo = 10;

$before = time();

#print "$before\n";

foreach (1..$howManyFoo)

{

my $curTime = time();

system("screencapture $destdir/$basename".$_."foo.pdf");

print "$basename".$_."foo.pdf $curTime\n";

sleep 5;

}

$after = time();
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$beforeAfterDiff = ($after - $before)/$howManyFoo;

$beforeAfterDiff -= 5;

print "beforAfterDiff $beforeAfterDiff\n";

$beforeAfterFrac = $beforeAfterDiff - int $beforeAfterDiff;

$beforeAfterDiff = int( $beforeAfterDiff);

print "beforeAfterFrac $beforeAfterFrac\n";

$howLongToSleep = $delay - $beforeAfterDiff;

if ($beforeAfterFrac > 0.5)

{

$beforeAfterDiff += 1;

$beforeAfterFrac = $beforeAfterFrac-1;

}

print "beforAfterDiff final $beforeAfterDiff\n";

print "beforeAfterFrac final $beforeAfterFrac\n";

}

our $whichone; $whichone = 1;

my $fracErr = 0;

my $fracFudge = 0;

snapshotruler();

snapshot();

foreach $delay (@atTimes)

{

$fracErr += $beforeAfterFrac;

if (abs($fracErr) > 1)

{

$fracFudge = (($fracErr > 0) ? 1 : -1);

$fracErr -= $fracFudge;

}

else

{

$fracFudge = 0;

}

$howLongToSleep = $delay - $beforeAfterDiff - $fracFudge;

sleep $howLongToSleep;

$whichone++;

snapshot();

}

snapshotruler();

print "\a\a\a\n";

#foreach $whichone (1..$howmany)

#{

# snapshot();

# sleep $howLongToSleep unless ($whichone==$howmany)

#}

sub snapshotXLR8

{

$curTime = time();

 system("screencapture $destdir/$basename"."$curTime.pdf");

print "$basename"."$curTime.pdf ($whichone of $howmany)";

print scalar localtime;

print "\n";

}

sub snapshot

{

$curTime = time();

my $script = <<EOS;

tell application "SecuritySpy"

capture image camera name "detector" as "$destdir/$basename$curTime.jpg"

end tell

EOS

# system("screencapture $destdir/$basename"."$curTime.pdf");

osascript($script);

# print "DEBUG: $destdir/$basename$curTime.jpg\n";

print "$basename"."$curTime.pdf ($whichone of $howmany)";

print scalar localtime;

print "\n";

}

sub snapshotruler

{

 $curTime = time();

 my $script = <<EOS;

tell application "SecuritySpy"

 capture image camera name "ruler" as "$destdir/Ruler$curTime.jpg"

end tell

EOS

# system("screencapture $destdir/Ruler"."$curTime.pdf"); 

osascript($script);
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# print "DEBUG: $destdir/Ruler$curTime.jpg\n"; 

 print "$basename"."$curTime.pdf ($whichone of $howmany)";

 print scalar localtime;

 print "\n";

}

my $script = <<EOS;

tell application "SecuritySpy"

capture image camera name "detector" as "$destdir/$basename$curTime.jpg"

end tell

EOS

# for OS X 10.6, where Adobe has bad osaxen

sub osascript10p6 { system 'arch', '-i386' , 'osascript', map { ('-e', $_) } split(/\n/, $_[0]); } 

# for 10.8?

sub osascript { system 'osascript', map { ('-e', $_) } split(/\n/, $_[0]); } 
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Appendix C: Video Analysis Software

Overview

This is the code used for initial analysis of raw data. 

To start, the number of files is entered into the Macro EnterNumFiles. File names 

(with encoded date and time of acquisition) are entered into the experiment, and 

converted into date, time, and nominal dose rate by ProcessFileNames. The number of 

dose rates measured is entered into PrepareToCrunch, which makes an effort to find the 

starting and stopping values of different dose rates from the nominal dose rates. After 

confirmation that the starts and stops are correct, the data is analyzed using Crunch or 

LinAnalyzeAll, depending on whether the data is ratemeter or integration mode. This 

produces averages, standard deviations, number of points, etc.

Minor changes are sometimes made to the code (e.g., the “3000” in the call to 

CarefulUncertNonCounts in LinAnalyzeAll might be changed if a meter with 

significantly different sensitivity were used).

This software is quite stable (i.e. neither changes nor updating are regularly 

required) but it is (at the same time as the software described in Appendix A) mirrored to 

the NIST central file server elwood in the 

68_PML/682/internal/682_Shared/CalData/682.03/CommonFiles/templates/video analysi

s stationery.pxt file, with scripts used by the file mirrored in the 

68_PML/682/internal/682_Shared/CalData/682.03/CommonFiles/WaveMetrics

directory.

Source Code

Selections from the source code are presented below for information.

Macro LinAnalyzeAll()

duplicate/o measDoses uncertDoses, digits

make/d/o/n=2 W_coef, W_sigma, W_ParamConfidenceInterval

digits = 3+((measDoses/(10^floor(log(measDoses))))<2)

uncertDoses = CarefulUncertNonCounts( measDoses, digits )

// "3000" on next line comes from cts/mrem for a typical meter

// 50 cpm/(mrem/hr) is 3000 cts/mrem

uncertDoses = max(uncertDoses, measDoses / sqrt(measDoses*cpmrem) )

// uncertDoses = sqrt(measDoses);

// tempcomplex = ()

avgnomdoses = average(nomdoses,starts,stops);

averages = real(LinAnalyzeOne(measDoses,tTimes,uncertDoses,starts,stops,0))

print "returning 95% confidence interval on fit";

sdevs = imag(LinAnalyzeOne(measDoses,tTimes,uncertDoses,starts,stops,3)) // get confidence interval instead of sdev

chisqs = real(LinAnalyzeOne(measDoses,tTimes,uncertDoses,starts,stops,2))

numMeas = real(LinAnalyzeOne(measDoses,tTimes,uncertDoses,starts,stops,4))

//print "scaling standard deviations by sqrt(chisq/dof)";

//sdevs *= sqrt(chisqs/(stops-starts+1-2))

// calFacs = AvgNomDoses/averages

End

Function/C LinAnalyzeOne(doseWave, timeWave, uncertWave, startPt,stopPt,whuh)

wave doseWave, timeWave, uncertWave;

variable startPt,stopPt,whuh;

WAVE/D W_coef

WAVE/D W_sigma

WAVE/D W_ParamConfidenceInterval

CurveFit/Q line measDoses[startPt,stopPt] /X=timeWave /W=uncertWave /I=1 /F={0.950000, 4}
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// print "Chisq = ",V_chisq;

if( whuh==2 )

return V_chisq;

elseif ( whuh==4 )

return V_npnts-V_numNaNs;

elseif (whuh ==3) // return confidence interval instead of standard dev of linear fit

return (cmplx(W_coef[1],W_ParamConfidenceInterval[1]));

else

return( cmplx(W_coef[1],W_Sigma[1]) );

endif

End

// from "Video Analysis" macro file -- AKT 3/3/99 13:54

Function Average(awave, startR, stopR)

wave awave; variable startR, stopR;

wavestats/q/r=[startR, stopR] awave

return( V_avg )

end

Function Sdev(awave, startR, stopR)

wave awave; variable startR, stopR;

wavestats/q/r=[startR, stopR] awave

return( V_sdev )

end

Macro EnterNumFiles(numFiles)

variable numFiles;

make/o/t/n=(numFiles) fileList;

make/o/n=(numpnts(fileList))/d tTimes,nomDoses,measDoses,chisqs

Edit fileList, tTimes, nomdoses, measDoses;

End

Macro ProcessFileNames()

// use ls *.pict | pbcopy under OS X -- akt 20020819 1535

// variable numFiles = LoadFileNames();

// fileList = IndexedFile(mod, p, "????")

tTimes = name2timeperl(fileList)

nomDoses = name2nomDose(fileList)

ModifyTable width(fileList)=160

SetScale d 0,0,"dat", tTimes

ModifyTable format(tTimes)=8,width(tTimes)=126

End

Function/D name2timeperl(aString)

string aString;

return str2num(aString[strsearch(aString,"mr",0)+2,strlen(aString)])+date2secs(1970,1,1)- 4*3600

End

Function/D name2time(aString)

string aString;

return str2num(aString[strsearch(aString,"mr",0)+2,strlen(aString)])+2^31

End

Function name2nomDose(aString)

string aString

return str2num(aString[0,strsearch(aString,"m",0)])

End

Macro PrepareToCrunch(numberDoseRates)

variable numberDoseRates;

// added "numMeas" -- akt 20021001 1155

make/o/n=(numberDoseRates)/d averages, sdevs, AvgNomDoses, starts, stops, calFacs, numMeas //,tempcomplex

// redimension/c tempcomplex

edit starts, stops, AvgNomDoses, averages, sdevs,calFacs

FindStartsStops( nomDoses, starts, stops );

numMeas = stops-starts+1

AvgNomDoses = Average(nomDoses,starts,stops);

averages = NaN;

sdevs = NaN;

calFacs = NaN;

End

Function FindStartsStops(nomDoses, starts, stops )

wave nomDoses, starts, stops;

variable i,j;

starts[0] = 0;stops[numpnts(stops)-1]=numpnts(nomDoses)-1;
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for( i=0, j=0; i<numpnts(nomDoses); i+=1)

if( nomDoses[i+1] != nomDoses[i] )

starts[j+1] = i+1;

stops[j] = i;

j+=1;

endif

endfor

End

Macro Crunch()

averages = average( measDoses, starts, stops )

sdevs = sdev( measDoses, starts, stops)

AvgNomDoses = average( nomDoses, starts, stops )

numMeas = stops-(starts-1)

calFacs = AvgNomDoses/averages

End

Macro dCrunch()

averages = average( dmeasDoses, starts, stops )

sdevs = sdev( dmeasDoses, starts, stops)

AvgNomDoses = average( nomDoses, starts, stops )

calFacs = AvgNomDoses/averages

End

Function/d CarefulUncert(counts,digits)

// given a wave of counts and a number of digits the meter reads, return the real uncertainty in number of counts

// -- akt 2001-11-14 1203

variable counts; variable digits;

return( max(10^(floor(log(counts))-digits+1),sqrt(counts)) );

End

Function/d CarefulUncertNonCounts(reading,digits)

// given a wave of readings and a number of digits the meter reads, return the (minimum) uncertainty in reading

// -- akt 2001-11-14 1203

variable reading; variable digits;

return( 10^(floor(log(reading))-digits+1) );

End

Function/D fit4drift(coeffs, x) : FitFunc

wave coeffs; variable x;

variable result;

// coeffs = {t0, y0, R, f, tau}

x -= coeffs[0];

result = coeffs[1] + coeffs[2]*x + coeffs[2]*coeffs[3]*coeffs[4]*exp(-x/coeffs[4]);

return result;

End
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Appendix D: Uncertainty Analysis

Single Calibration Factor

For a single calibration factor, example uncertainties are shown below in Table 4. 

Table 4: Example Uncertainties

Description Type A 

(%, k=2) 

Type B 

(%, k=2) 

How Determined

(bare)

How 

Determined

(moderated)

Instrument Reading 0.4 Std. Dev. of 

readings Same as bare

Source Strength 2.6 2.6 % 2.4 %

Room Return & Air Scatter correction 1.8 0.4 * Total 

Correction Same as bare

Fluence / Dose Equivalent Conversion 2 2 % 8 %

Effective Source-Detector Distance 5.1 0.5 cm*2/ sourcedetector distance Same as bare

Quadratic Summation 0.4 6.3 

The expanded uncertainty at an approximate level of confidence of 95 % is also 

6.3 %, as the Type B uncertainties dominate the combined uncertainty.
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Full example uncertainty analysis

A detailed example of an uncertainty analysis is given here, using data taken from 

the sample report in Appendix E. The unit mrem is used here because it is the preferred 

quantity for customers of this calibration service.

The first table below contains “correlated” uncertainties. These are uncertainties 

where the source of the uncertainty does not vary between measurements, and thus the 

uncertainty cannot be reduced by taking more measurements or averaging over several 

measurements. The total correlated uncertainty is the combination in quadrature of the 

other three.

Table 5: Correlated Uncertainties

Dose Rate 

(mrem/h)

Source Strength 

Uncertainty (%)

Correction 

Uncertainty (%)

Fluence to Dose 

Equivalent Conversion 

Uncertainty (%)

Total Correlated 

Uncertainty (%)

3.0 2.6 0.92 2 3.41

10.0 2.6 2.24 2 3.97

30 2.6 1.01 2 3.43

100 2.6 1.01 2 3.43

300 2.6 1.0 2 3.43

600 2.6 1.56 2 3.63

899 2.6 2.19 2 3.94

The next table contains “uncorrelated” uncertainties. The sources of these 

uncertainties do vary between measurements. For instance, the “distance” uncertainty, 

which is partially caused by not knowing the position of the radioactive material within 

the source capsule, is different between sources and, indeed, between different raisings of 

the source because the sources can rotate freely. 

Table 6: Uncorrelated Uncertainties

Dose Rate

(mrem/h)

Source-Detector 

Distance Uncertainty 

(%)

Uncertainty of 

Readings (%)

Number of 

Measurements

Total Uncorrelated 

Uncertainty (%)

3.0 2.17 3.46 13 2.51

10.0 1.09 1.86 12 1.39

30 1.92 1.06 13 1.34

100 1.91 0.59 13 1.23

300 3.31 0.36 13 2.04

600 4.66 0.28 13 2.86

899 5.66 0.21 13 3.47

The calculation of the Total Uncorrelated Uncertainty is complicated by the fact 

that data is taken either as a collection of independent dose rates in “ratemeter” mode, or 
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as an integrated dose. If the measurement is taken in integrated mode, then the data of 

integrated dose vs. time is fit to a line, and the uncertainty is extracted from the k=2 

confidence level for the slope of the line; in this case the uncertainties are combined in 

quadrature. If the data are taken in ratemeter mode, the reading uncertainties are sample 

standard deviations of measurements and are combined with distance uncertainties using 

where n is the number of measurements, t() returns the value for the Student T given an 

integrated two-tail probability (0.9545 ~ the integrated probability for k=2) and number 

of degrees of freedom (i.e., the number of measurements). The sigma’s are the 

uncorrelated uncertainties discussed above. The example data in the table above was 

taken in ratemeter mode.

The correlated and uncorrelated uncertainties are combined in quadrature to 

calculated the uncertainty for the calibration factor for a given dose equivalent rate; they 

are separated only for their effect on the weighted average calibration factor.

The calculation of the weighted average calibration factor and its uncertainty is 

difficult. As mentioned above, the correlated uncertainties are not reduced by making 

multiple measurements (i.e., at different dose rates). Therefore, the weighted mean of the 

calibration factor is calculated using only the uncorrelated uncertainties. The standard 

weighted uncorrelated uncertainty (which is smaller than the individual uncorrelated 

uncertainties because of the multiple measurements) is calculated as well. (n.b.: the 

relative uncertainties given in the table must be converted to absolute uncertainties before 

performing the calculation).

Combining the weighted uncorrelated uncertainty with the correlated uncertainty is 

problematic because the correlated uncertainties are not equal for all measurements. To 

solve this issue, an “average” correlated uncertainty is calculated. It is calculated as a 

weighted mean of correlated uncertainty for all dose rates, using the uncorrelated 

uncertainty for the weighting (thus, measurements with, for instance, high observed 

standard deviations will not contribute to the average correlated uncertainty as much as 

measurements with low observed standard deviations).

The total uncertainty on the weighted mean is, finally, calculated as the addition in 

quadrature of the weighted uncorrelated uncertainty and the average correlated 

uncertainty.
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Appendix E: Sample Calibration Report
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