Evaluation of the Response of Film Badges to High Energy Photons 

NIOSH/DCAS
 

Greg Macievic, Ph.D 

October 4, 2011 

In response to a question raised during GSI work group discussions, NIOSH has 

evaluated the relative response of dosimeter film to the high energy bremsstrahlung 

photons produced by an electron accelerator. 

Source Term 

The electron accelerator, or betatron, produces high energy electrons which in turn 

produce spectrum of bremsstrahlung photons which vary in energy up to the maximum 

energy of the electron. The energy range of the spectrum depends on the accelerating 

voltage of the machine. The electron energy of betatrons generally range from 20 MeV 

to 35 MeV. 

The energy distribution of bremsstrahlung x-ray photons for 20 MeV and 24 MeV 

electrons is shown in Table 1 below.1 

Table 1 

Energy Region Intensity,% Intensity, % 

MeV 20 Mev 24 Mev 

0-3 69.23 65.3 

3-5 11.29 11.43 

5-10 12.66 12.65 

10-12 2.71 2.89 

12-14 1.98 2.22 

14-16 1.3 1.77 

16-18 0.67 1.46 

18-20 0.16 1.14 

20-22 0.62 

22-24 0.25 

For electrons 20 MeV electrons, 96 % of the photon intensity is in the 0 to 12 MeV range. 

The 24 MeV electron, has 92% of the photon intensity in the 0 to 12 MeV range. 

This is a working document prepared by NIOSH or its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final 

NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as 

such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its 

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NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy 

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2 

Dosimeter 

A radiation monitoring dosimeter is made up of photographic emulsion and a holder 

which incorporates filters made up of differing density materials to smooth energy 

response. The emulsion darkens with photon exposure. This darkening or density is a 

function of intensity and energy of the photons. 

The emulsion is essentially made of silver halide and a substrate. Table 2 provides the 

composition of emulsions from several manufacturers in the early 1960s2

. The 

compositions are similar with some variation based on the particular type of radiation to 

be detected. 

Table 2 

The film holder consists of a structural base and a set of filters. The number and type of 

filters provide information on the energy and type of radiation to which it is exposed. 

The filters consist of bare film, plastic and varying density metal. Of particular interest is 

the response of the film under metal filters to high energy photons. As the photon energy 

increases the density under the metal filter is greater than that of bare film. Figures 1 and 

2 below, which were taken from Attix2 et al. and Yoder and Zelac3, illustrate this effect. 

This is a working document prepared by NIOSH or its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final 

NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as 

such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its 

contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy 

Act 5 USC §552a and has been cleared for distribution. 
3 

Figure 1 

Film response with 0.020 inch tantalum filter (adapted from Brady and Iverson 1968) 

This is a working document prepared by NIOSH o r its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White P aper documents are not final 

NIOSH or ABRWH (or their techn ical support and review contractors) positions unless specifi cally marked a s 

such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its 

contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy 

Act 5 USC §552a and has been clear ed for distribution. 
 

4 

Figure 2 

Relative sensitivity of Kodak RM film as a function of photon energy and angle of 

incidence of radiation. Film under filter of 0.71 mm Sn plus 0.31 mm Pb. (Heard and 

Jones, 1963)2 

In Figure 2, the normal incidence exposure (00

), as well as the other angles of incidence, 

shows the relativ e sensitivity increasing under the metal filter (Sn-Pb) as a function 

photon energy. The similar response can be seen in Figure 1 for a different type of meta l 

filter (Ta). This effect is due, in part to the increase of the pair production interaction 

coefficient with photon energy and atomic number. 

This is a working document prepared by NIOSH o r its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White P aper documents are not final 

NIOSH or ABRWH (or their techn ical support and review contractors) positions unless specifi cally marked a s 

such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its 

contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy 

Act 5 USC §552a and has been clear ed for distribution. 
5 

Conclusion 

Film badges worn in an environment where high energy photons (>1 MeV) are present, 

such as a betatron, have an increase in response over photons below 1 MeV, with the 

magnitude of the over response increasing with increasing photon enegy. A dose based 

on the film density underneath the metal filter would be biased in the high direction. 

References 

1.	 Activation Method For Measurement Of Bremsstrahlung Photon Flux 

Produced By Electron Accelerator, Tran Duc Thiep et al, JINR, Dubna, 2005 

2.	 Attix, Roesch, Tochilin, Radiation Dosimetry 2nd Edition, Volume II 

Instrumentation, Academic Press, 1966. 

3.	 R. Craig Yoder, Ronald E. Zelac, Film Dosimetry, Chapter 5. Materials from 

Film Badge Dosimetry in Atmospheric Nuclear Tests, National Academy 

Press, 1989, National Academy of Sciences National Research Council. 

This is a working document prepared by NIOSH or its contractor for use in discussions with the ABRWH or its 

Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final 

NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as 

such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its 

contractor. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the Privacy 

Act 5 USC §552a and has been cleared for distribution.