Shani G. Radiation Dosimetry: Instrumentation and Methods

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440 Radiation Dosimetry: Instrumentation and Methods

of application, very differing detector sizes were

employed.

A spherical proton recoil proportional counter was used

by Weyrauch and Knauf [15] to measure neutron ﬂuences.

The response functions of that counter have recently been

calculated with sufﬁcient accuracy, taking into account gas

ampliﬁcation and wall effects. Neutron scattering from the

counter walls was estimated using the MCNP code. Signif-

icant progress has been made in quantitatively understand-

ing the response of the spherical counter, and it could be

shown that including the variation of gas ampliﬁcation

along the counting wire, as a result of the variation of the

electric ﬁeld strength, is sufﬁcient to explain experimental

data. A comparison between calculated and measured

response functions is shown in Figure 10.23 for an incident

neutron energy of 144 keV (ﬁltered reactor beam). In the

proton energy range from about 25 keV to 100 keV, the

shape of the calculated and measured responses agree on

the 0.1% level.

The measured pulse height distribution P(E

) is related

to the spectral neutron ﬂuence (E) by

(10.21)

where is the recoil proton energy, is the energy of

the incident neutron,

N denotes the total number of protons

in the counter, and is the neutron-proton total cross

section. The response function is normal-

ized, so that the total number of recoil protons Z is

obtained from

(10.22)

To obtain the absolute ﬂuence distribution, Equation

10.22 should be followed.

FIGURE 10.21 Calculated neutron kerma factors for carbon as a

function of incident neutron energy from 15 to 150 MeV. The ﬁgure

shows kerma factor values of Gorbatkov et al. (solid curve), the results

of Morstin et al. [62] (—

...

—

...

—

...

), and the results of Savitskaya et

al. [63] (–

–

–). (From Reference [13]. With permission.)

() NRE

,()



() E

()E









()

()

ZPE

()E









() E

()E







FIGURE 10.22 Ambient dose equivalent response, , for monoenergetic neutrons as a function of neutron energy, , for two

TEPC systems (BIO: full circles; KFA: open circles) and a moderator-type neutron dose equivalent meter (Leake: squares). The

TEPC systems were calibrated in a

252

Cf(D

O) ﬁeld. The lines serve as eye guides. The results were obtained within the framework

of an intercomparison. (From Reference [14]. With permission.)

Ch-10.fm Page 440 Friday, November 10, 2000 12:04 PM

Neutron Dosimetry 441

If the relative spectral distribution of neutrons

is known, Equation 10.22 can be used to obtain the ﬂuence

. In this case, only remains to be

determined. Normalizing



), we obtain

(10.23)

and, from Equation (10.22),

(10.24)

The principle of a multi-element tissue-equivalent pro-

portional counter dosimeter was proposed by Kliauga. [16]

It consists of 200 elements (right cylinders, diameter



height  3.6 mm) in 25 groups. Each element corresponds

to a microdosimetric proportional counter, and each group

has a common wire anode. The counter radiation cross section

is 5.3 times that of a spherical counter with the same volume.

The mechanical structure is very complex, as is shown in the

corresponding schematic diagram (Figure 10.24 ).

A multichannel tissue-equivalent proportional counter

MC-TEPC dosimeter is based on a microdosimetric tis-

sue-equivalent proportional counter. [17] The sensitivity

of this detector is enhanced by increasing the counter

radiation cross section. The 8-mm-thick cathode is drilled

with some 250 4-mm-diameter holes, and electron

swarms, created by interactions of secondary charged par-

ticles in the counting gas, are drifted along the holes’ axis

to 10 high-potential wire anodes by an electrokinetic ﬁeld.

This electric ﬁeld is obtained by a bias current ﬂowing

from the internal to the external race of the cathode.

Electrons are multiplied around and collected by the wire

anodes. The sensitivity of the detector is between 5 and 7

FIGURE 10.23 Measured pulse-height distribution (full line) compared with the calculated response (dashed line). The SP2 counter

was exposed to reactor neutrons ﬁltered through 1372 mm Si and 60 mm Ti, which produces a nearly monoenergetic neutron line

144 keV. Both curves are normalized to unity. (From Reference [15]. With permission.)



()

 E

() 



()

 E

()E





1





()



()E





-------------------------------------------------



FIGURE 10.24 Schematic view of the multi-element tissue-

equivalent

proportional counter proposed by Kliauga. (From

Reference [17]. With permission.)

Ch-10.fm Page 441 Friday, November 10, 2000 12:04 PM

442 Radiation Dosimetry: Instrumentation and Methods

times that of a multi-cellular and spherical counter of the

same external size. A view of the counter interior is shown

in Figure 10.25.

Paired miniature tissue-equivalent proportional counters

for dosimetry in high-ﬂux epithermal neutrons were

described by Burmeister et al. [18] A pair of miniature TEPCs

has been constructed with sensitive volumes of 0.0027 cm

The design is shown in Figure 10.26. The cathode of one

TEPC is made of A-150 conducting tissue-equivalent plastic.

The cathode of the paired TEPC is made of A-150 loaded

with 200



g/g of

B. The gas ﬁll is a propane-based

tissue equivalent (TE) counting gas. Propane-based tissue-

equivalent (p-TE) gas, which consists of 54% propane,

40.5% CO

, and 5.5% N

, is one of the two TE gases most

commonly used in microdosimetry ionization chambers and

in low-pressure proportional counters.

The mean energy required to form an ion pair after com-

plete dissipation of incident particle energy, W, for electrons,

protons, alpha particles, and heavy ions (

O) in

propane-based tissue-equivalent gas was summarized and

analytically represented by Bronic. [19] The energy depen-

dence of the

W value for electrons can be described as:

(10.25)

Here, is the asymptotic high-energy electron W value,

E is electron energy, and U is the average kinetic energy

of sub-ionization electrons.

The experimental data for heavier particles can be

ﬁtted using the function:

(10.26)

where



is the energy of the particle in keV amu

1

and

A, B, C, and D are ﬁtting parameters. W values for elec-

trons in propane-based TE (p-TE) gas were ﬁtted using

Equation (10.25) (Figure 10.27).

The W value for He ions shows somewhat stronger

energy dependence in propane than in p-TE gas (Figure

10.28). The average ratio of the W values in p-TE gas and

those in propane is 1.0, which is lower than the corresponding

ratio for electrons and protons (1.07), as well as for heavy ions.

The neutron sensitivity of a C-CO

ionization cham-

ber has been experimentally determined by Endo et al.

[20] in the neutron energy range of 0.1–1.2 MeV. Eleven

data were obtained which ranged from 0.04 to 0.1 as

a function of neutron energy. There were two peaks in

the spectrum of the factor and their positions corre-

sponded to the resonance energies of the kerma factors

FIGURE 10.25 Schematic view of the multi-channel tissue-equivalent proportional counter (MC-TEPC) developed at the SDOS.(From

Reference [17]. With permission.)

FIGURE 10.26 Design of 0.0027-cm

TEPC. (From Reference [18]. With permission.)

WE()



1 UE()

--------------------------





WE()

EB()ln[]

---------------------------------



Ch-10.fm Page 442 Friday, November 10, 2000 12:04 PM

Neutron Dosimetry 443

of carbon dioxide, of which the energies are about 0.4

and 1 MeV.

The paired-chamber method is the most reliable tech-

nique to separately determine kerma values in neutron and

gamma-ray mixed ﬁelds. Usually, one of the pair is a TE-

TE chamber which is made with an A150 plastic wall and

ﬁlled with tissue-equivalent gas. This chamber determines

the sum of neutron and gamma-ray kermas. The other

chamber of the pair is a C-CO

chamber which is made

with a graphite wall and is ﬁlled with carbon dioxide gas.

This chamber essentially determines the gamma- ray kerma

except for a small response for neutrons. The neutron kerma

is approximated by subtracting the gamma-ray kerma from

the sum of the gamma-ray and the neutron kerma. In actu-

ality, the effect of its small neutron sensitivities for the C-

chamber ( factor) must be considered, since the

chamber has a response of about 0.1–10%, depending on

the neutron energy. [20] The factors are approximately

proportional to the gas kerma factor.

The neutron sensitivity of the C-CO

chamber is

denoted by . The factors range from 0.04 to

0.1 and are dependent on the neutron energy, as shown in

Table 10.7. The neutron sensitivity of a C-CO

chamber is

roughly proportional to the kerma ratio where

in the gas and in the tissues. It is also proported to

the ratio , where Co means the calibration ﬁeld of

Co and n means the neutron ﬁeld. The cavity is assumed

sufﬁciently large compared to the ranges of the recoil par-

ticles. The energy deposited in the gas is due only to charged

particles liberated in the gas. The factor is expressed

(10.27)

FIGURE 10.27 W value for electrons in propane-based TE gas. Experimental data: (), Combecher; [64] (), Krajear Bronic

et al.; [65] (—) ﬁtted line, Equation (10.25). (From Reference [19]. With permission.)

FIGURE 10.28 W value for alpha particles in propane and propane-based TE gas. Experimental data: (), propane; (), propane-

based TE gas, ﬁtted lines, Equation 10.26; ( ), propane; (– –),

p-TE, experimental data; (–.–), p-TE, calculated values. (From

Reference [19]. With permission.)

…

UC

() k

UC

K

()

W

UC

UC



K

()W

W

()

Ch-10.fm Page 443 Friday, November 10, 2000 12:04 PM

444 Radiation Dosimetry: Instrumentation and Methods

where



is a normalization constant which may be related

to the effective kerma component ratio of the graphite wall

to the carbon dioxide gas.

Recombination chambers are high-pressure tissue-

equivalent ionization chambers, designed and operated in

such a way that ion-collection efﬁciency in the chambers

is governed by initial recombination of ions.

A large chamber of REM-2 type was ﬁlled to a pres-

sure of about 1 MPa with a gas mixture consisting of

methane and 5% (by weight) nitrogen. [21] The output

signal of the chamber is the ionization current (or collected

charge) as a function of collecting voltage (Figure 10.29).

All the recombination methods require the measurement

of the current (or charge) at at least two values of the

collecting voltage. The highest voltage should provide the

conditions close to saturation; i.e., almost all the ions

generated in the chamber cavity should be collected. In

practice, the maximum voltage that can be applied to the

chamber without causing a considerable dark current or

other unwanted effects is used.

Depending on the number of measured points of the

saturation curve (see Figure 10.29), one can obtain differ-

ent information:

a. The ionization current measured at maximum

applied voltage is proportional to the absorbed

dose

D (some small corrections for lack of sat-

uration can be introduced when needed).

b. Measuring at two voltages enables determina-

tion of the recombination index of radiation

quality, , that approximates the quality fac-

tor. Then the ambient dose equivalent,

can be determined as .

c. The measurement of ionization current at six

collecting voltages and mathematical analysis

of the saturation curve enable separation of low-

LET and high-LET dose fractions and determi-

nation of quality factor and (10).

d. Measuring at 15 or more collecting voltages

enables determination of crude microdosimetric

spectra terms of dose distributions in LET. The

method is based on similar but more detailed

mathematical analysis than methods used when

TABLE 10.7

The Results for the Factor as a Function of

the Neutron and the Proton Energies

Proton Neutron

energy energy

(MeV) (MeV) factor

3.0 1.2 0.095  0.008

0.100  0.009

2.9 1.1 0.100  0.008

2.8 0.99 0.110  0.009

0.120  0.010

2.7 0.90 0.086  0.007

2.6 0.78 0.076  0.006

0.076  0.010

2.5 0.69 0.072  0.006

2.4 0.57 0.072  0.006

0.074  0.010

2.3 0.48 0.076  0.006

2.2 0.37 0.075  0.009

0.089  0.010

2. 1 0.25 0.045  0.008

2.0 0.11 0.038  0.010

0.041  0.011

The uncertainty of the factor value is the standard deviation

(68% conﬁdence interval) of the mean for several measurements.

From Reference [20]. With permission.

10(

)

10() DQ



FIGURE 10.29 Example of saturation curves measured with REM-2 recombination chamber. Circles,

137

Cs reference gamma

radiation; triangles, 2.5-MeV neutrons; crosses show two points needed for determination of ICRP 21 quality factor; solid points are

needed for measurements of

(10) with ICRP 60 quality factor, and all the points are used for microdosimetric distributions. (From

Reference [21]. With permission.)

Ch-10.fm Page 444 Friday, November 10, 2000 12:04 PM

Neutron Dosimetry 445

measurements are performed at six points.

Somewhat better accuracy can be achieved in

determination of ; however, the time

needed for measurements is longer and the

mathematical analysis requires some experi-

ence. [21]

The recombination index of radiation quality (RIQ),

denoted as , is a measurable quantity that directly

approximates the radiation quality factor. Determination

of Q

involves two steps:

1. calibration of the chamber in a reference

gamma radiation ﬁeld from a

137

Cs source; dur-

ing the calibration, the recombination voltage

is determined in such a way that the ion-

collection efﬁciency ; and

2. determination of ion-collection efﬁciency,

. The investigated radiation ﬁeld

requires measurements at two voltages, as indi-

cated by crosses in Figure 10.29.

is then calculated according to its deﬁnition as:

(10.28)

Because ,

(10.29)

A recombination chamber was used by Golnik and

Zielczynski [22] for determination of . It was shown

that both and the ICRP 21 quality factor had a similar

dependence on LET. is plotted against LET in Figure

10.30 as a dashed line. Since ICRP 60 introduces a new

functional relationship between the quality factor and

LET (solid line in Figure 10.30), it is not possible to use

Q as a direct approximation of the ICRP 60 quality

FIGURE 10.30 Dependence of and quality factor (ICRP Report 60) on LET. (From Reference [22]. With permission.)

FIGURE 10.31 The relationship between and for radiations with a single value of LET. The same curve is used for

the dependence of on . Dashed lines represent the differences between and . (From Reference [22]. With permission.)

ICRP 60

10()



()0.96

mix

()

1 f

mix

()

1 f



()

---------------------------------



() 0.96

1 f

()0.04

Ch-10.fm Page 445 Friday, November 10, 2000 12:04 PM

446 Radiation Dosimetry: Instrumentation and Methods

factor. The relationship between the two is shown in

Figure 10.31.

The recombination index of radiation quality (RIQ)

was determined by Golnik et al. [23] in high-energy neu-

tron beams from the 660-MeV phasotron of the Joint

Institute for Nuclear Research, Dubna (JINR). Measure-

ments were performed with a high-pressure ion chamber

at two collecting voltages and compared with calculations

considering spectra of all secondary and tertiary charged

particles.

Measurements of were performed using a

3.8-cm

in-phantom recombination chamber of F-l type (Fig-

ure 10.32), ﬁlled with TE gas up to 500 kPa. The disc-

shaped chamber has three parallel-plate tissue-equivalent

electrodes, 34 mm in diameter (total diameter of the cham-

ber is 62 mm). The distance between electrodes is 1.75

mm. The sensitivity of the chamber is about 350 nC Gy

1

Its operational dose rate range is from 10

3

up to 1.5 Gy

 1

. Two collecting voltages, and

, were sequentially applied to the chamber

electrodes. RIQ was determined as:

(10.30)

where

i is the ionization current of the recombination cham-

ber related to the monitor reading, , and

is the ion-collection efﬁciency at collecting voltage

, determined in the gamma radiation ﬁeld of the reference

137

Cs source. In experiments described here, .

IV. TLD NEUTRON DOSIMETRY

Using TL detectors for the dosimetry in mixed neutron-

gamma ﬁelds requires knowledge of their response to

neutrons over a broad energy range. For the calculation

of the neutron ﬂuence response, the conversion of the

energy deposited by the secondary heavy charged particles

to the TL reading effect must be considered. For this

purpose, the light conversion factors for all secondaries

as a function of their energy must be known. The relative

light conversion factor is the ratio of the detector reading

coming from a mass element where the dose was absorbed

as a result of the deposition of the ion. The energy depo-

sition by secondary ions and gamma radiation generated

as a result of neutron interaction in the detector material

or in the surrounding material (detector holder, radiator)

is of fundamental importance.

Thermoluminescent materials such as LiF(TLD-100),

LiF(TLD-700,

LiF(TLD600), and CaF

(TLD-300) show

curves (TL intensity as a function of temperature, T ) in

which the different peaks exhibit a different dependence

on the LET of the radiation. This allows the separate

determination of photon and neutron doses in a mixed

(n,



) radiation ﬁeld with the two-peaks method.

The thermal neutron response of any TL materials

depends on the capture cross section of the elements of

those materials. Boron and lithium have large cross sec-

tions for thermal neutrons. All neutron reactions in LiF

used for the determination of the intrinsic response com-

ponent are summarized in Table 10.8.

The energy deposited yields ﬂuence-to-kerma con-

version factors. Figure 10.33 shows the intrinsic ﬂu-

ence-to-kerma conversion factor for different materials.

While in the low neutron energy region, the reaction

Li(n,



)

H dominates; i.e., the different contents of

cause different factors, and for high-energy neutrons,

the polyethylene reaction has the similar contribution.

The additional K/ component from the 1-mm-thick

TABLE 10.8

Selected Neutron Interactions in LiF Materials

Reaction

Q value

(MeV)

Elastic scattering

Li —

Inelastic scattering

Li 1.47128

Li(n,



)

H 4.786

Li(n, p)

He 2.7336

Elastic scattering

Li —

Inelastic scattering

Li 0.477484

Li(n,d)

He 7.76382

Elastic scattering

F —

Inelastic scattering

F 0.11

F(n,p)

O 4.0363

F(n,d)

O 5.76892

F(n,t)

O 7.55613

From Reference [24]. With permission.

RIQ()

30 V

800 V

---

i 30V()

i 800V()

--------------------









R 1 f



()



()

R 0.04

FIGURE 10.32 Cross section of the in-phantom chamber of F1 type (for historical reasons this chamber is sometimes called the

KR-13 chamber). (From Reference [23]. With permission.)

Ch-10.fm Page 446 Friday, November 10, 2000 12:04 PM

Neutron Dosimetry 447

PE radiator to the sintered LiF detector is included in

Figure 10.33.

LiF-enhanced dosimeters exposed to high ﬂuences of

thermal neutrons undergo irreversible radiation damage,

preventing their subsequent utilization.

LiF-depleted dosim-

eters do not show such an effect, but in mixed ﬁelds of high

ﬂuxes with thermal neutrons, they do not provide a simple

way of discriminating among the contributions of the ﬁeld

components. The responses to thermal neutrons and to



-rays

of some TL single crystals have been investigated by Gam-

barini et al. [25] LiF:Mg,Cu,P and LiF:Cu

single crystals

have shown a much higher sensitivity to thermal neutrons

than to



-rays.

Owing to the high cross section of

LiF for the reaction

with thermal neutrons,

Li(n,



)

H, LiF dosimeters of differ-

ent isotopic composition, exposed in thermal neutron ﬁelds,

present different sensitivities and different shapes of glow

curve. With regard to thermal neutrons,

LiF:Mg,Cu,P chips

have shown a response about nine times higher than that of

LiF:Mg,Ti, linear in the low-dose range.

In Figure 10.34, the reduction factor of the response to



-rays of TLDs exposed to thermal neutrons and afterward

annealed is shown as a function of the total nth ﬂuence under

previous exposure. The results show that

LiF chips, after

exposure to high ﬂuences of thermal neutrons, depart from

linearity, moderately for the Mg,Ti-doped phosphors and

FIGURE 10.33 Kerma factors for LiF TLDs. Additional kerma in sintered LiF TLD caused by a 1-mm thick polyethylene radiator.

(From Reference [24]. With permission.)

FIGURE 10.34 Comparison between commercial

Li-enriched and depleted LiF for



- ray irradiation after thermal neutron exposure

at different ﬂuences. TL intensities are normalized to the response after a 1 Gy -



irradiation. (From Reference [25]. With permission.)

Ch-10.fm Page 447 Friday, November 10, 2000 12:04 PM

448 Radiation Dosimetry: Instrumentation and Methods

markedly for the Mg,Cu,P-doped ones; moreover, they reveal

irreversible radiation damage which invalidates their new uti-

lization after such exposures. In contrast,

LiF chips, doped

with Mg,Ti or Mg,Cu, P, do not show such radiation damage

in the ﬂuence-investigated interval.

The different LET dependences of the low- and high-

temperature glow peaks of CaF

:Tm thermoluminescent

material (TLD-300) allow the determination of neutron and

gamma dose simultaneously.

To calibrate TLD-300 dosimeters, the individual sen-

sitivities of the two glow peaks to neutrons and photons

are experimentally determined. A calibration method was

proposed by Kriens et al. [26] The response of the

glow peak i to the mixed n-



ﬁeld relative to its sensitivity

to the



-rays used for calibration is given by:

(10.31)

where of the glow peak

i to neutrons,

relative to its sensitivity to the



-rays used for calibration,

and of the glow peak i to photons in the

mixed n-



ﬁeld, relative to its sensitivity to the



-rays

used for calibration.

With the assumption that the sensitivities of the TLD-

300 glow peaks to the photons in the mixed n-



ﬁeld are

equal to their sensitivities to the



-rays used for calibration

, the relative neutron sensitivities of the two

peaks are given by: [26]

(10.32)

Dividing Equation (10.31) by the total dose D

 D

 D



yields:

(10.33)

The linear regression of multiple values or

and determines or and or , if and

the ratios are known for multiple measuring con-

ditions. The variation of is performed by three

procedures: different phantom depths, different ﬁeld sizes,

and additional exposure to



rays.

For all calibration methods used, the mean value of the

relative sensitivities of the two TLD-300 glow peaks were

found to be k

 (0.078  0.029) and k

 (0.215  0.047)

for fast neutrons, as well as h

 (1.02  0.36) and h



(1.02  0.26) for photons of the mixed n-



beam, comparable

to recent measurement.

The relative neutron responses of both peaks in TLD-

300 chips were found by Hoffmann et al. [27] to be 0.10

and 0.32. Using this method, various dose distributions of

neutron and gamma dose in a water phantom were mea-

sured and compared with the results of GM counter mea-

surements and Monte Carlo dose calculations.

The normalized TLD readings for corresponding gam-

mas and neutrons of the low-and high-temperature glow

peaks should be different according to [27]

(10.34)

(10.35)

where

K  kerma ratio CaF

O  0.27 at 14 MeV.

From these equations, the neutron, gamma, and total dose

distribution are:

(10.36)

(10.37)

(10.38)

where is the sensitivity of the low-temperature peak

and is the sensitivity of the high-temperature peak.

The larger the difference and the higher the

kerma ratio

K, the higher the accuracy of the dose

determination.

The CaF

:Tm (TLD-300) material was used as chips

of size 3 mm  3 mm  0.9 mm. Before irradiation, the

chips were annealed at 400C for 1 h. Each dosimeter

was calibrated individually by



irradiation at an

exposure level equivalent to 130 mGy (13 rad) in muscle

tissue. [27]

After neutron irradiation, the glow curves show a very

different shape as compared to those induced by



irradiation (see Figures 10.35 and 10.36). Due to the high

LET component, the response of the low-temperature peak

1 is largely reduced, whereas the response of peak 2

remains relatively high. The peak height ratio therefore

reduces from about 3:1 for gammas to 1.1:1 for free-air

neutron irradiations.

The resulting neutron responses can then be derived

from Equations 10.34 and 10.35 to be

R

 k





sensitivity

1()

12,

R

12,



()

-------------------------------



R

12,

-----------

12,

()



------



R

D

R

D







D



D

()

------------------







K()D



()

------------------





K()D







K()



K()

-------------------------------------







----------





----------

1

----------------------------------



total







()



K 0.32



K, 0.10

Ch-10.fm Page 448 Friday, November 10, 2000 12:04 PM

Neutron Dosimetry 449

The dose is then calculated according to

(10.39)

(10.40)

where and are the normalized TL readings of

both peaks, measured as peak heights after irradiation in

the neutron ﬁeld.

TLD-300 detectors were used by Angelone et al. [28],

allowing the neutron and gamma contribution to the total

nuclear heating to be separated by using the two-peak

method. The so-called peak 3 and peak 5 show different

sensitivities to gamma and neutrons. TLD-300 was chosen

because of its sensitivity to low gamma-ray dose and its

high .

A 14-MeV neutron generator produces up to 1.0



1

14-MeV neutrons by using the D-T fusion reac-

tion. The total measured doses ranged from 4.9  10

19

Gy per neutron up to 1.9  10

14

Gy n

1

, which covers

the whole linear response range for TLD-300.

The TLD-300 dosimeters were calibrated in a second-

ary standard gamma radiation ﬁeld using a

Co source

calibrated at 0.5% up to 3.5%, depending on the dose level.

The calibration ranged from 10



Gy up to 35 Gy. Mea-

suring the response of the two main peaks of TLD-300, it

is possible to separate the neutron and gamma absorbed

doses. The corresponding equation, accounting for the fact

that the phosphors are embedded in stainless steel, is:

(10.42)

FIGURE 10.35 Glow curve of a TLD-300 dosimeter after

Co irradiation. (From Reference [27]. With permission.)

FIGURE 10.36 Glow curve of a TLD-300 dosimeter after irradiation in a 14-MeV neutron beam. (From Reference [27]. With

permission.



0.22

-------------------------





3.2P



2.2

---------------------------------



total





eff

16.2()





k

Ch-10.fm Page 449 Friday, November 10, 2000 12:04 PM