Congresso del Dipartimento di Fisica

Highlights in Physics 200511–14 October 2005, Dipartimento di Fisica, Università di Milano

The thermoluminescence peaks of quartz at intermediate temperatures and their use in dating and dose reconstruction I. Veronese, A. Giussani and M.C. Cantone

Dipartimento di Fisica, Università di MilanoINFN – Sezione di Milano

Wavelength (nm)

250 300 350 400 450 500 550 600 650 700

Te

mpe

ratu

re (

°C)

50

75

100

125

150

175

200

225

250

Temperature (°C) Lifetime peak I Lifetime peak II

140 - (23±1) min

120 (2.2±0.3) min -

100 (13±2) min (69±5) h

70 (7±1) h (30±2) d

44 (7.8±0.7) d -

15 720±70 d 580±70 y

PeakActivation

energy (eV)Frequency factor (s-

1)Method of analysis

I1.13±0.03 (3.35±2.99)•1012 PS

1.22±0.02 (3.39±1.46)•1013 ID

II1.46±0.06 (7.79±10.91)•1014 PS

1.36±0.02 (2.23±0.75)•1013 ID

12.5

13.0

13.5

14.0

14.5

15.0

15.5

16.0

16.5

17.0

250

300

350

400

450

500

550

600650

700

5075

100125

150175

200225

TL

inte

nsity

(a.

u.)

Wav

elen

gth

(nm

)

Temperature (°C)

TL dosimetry for evaluation of accidental dose using quartz extracted from recent building materials in urban settlements: assessment of the limits of the technique and of the minimum detectable dose.

SCOPE:

MATERIALS AND METHODS:- Quartz extracted from recent building materials - Automated TL reader (Risø TL-DA-12)- Techniques for the total accrued dose assessment:

regeneration dose and additive dose- Techniques for the natural dose rate assessment: gamma

spectrometry, beta dosimetry, alpha counting, flame photometry.

- Pure quartz purchased from Merck Company - High Sensitivity spectrometer for 3D TL analysis

- Secondary Standard Dosimetry Laboratory at GSF- Methods of glow curve analysis: Peak Shift (PS)

and Isothermal Decay (ID)

RESULTS:

Fig. 1 Spectral emission of pure quartz (3D vision and contour plot) in the temperature range of interest. Two main peaks (peak I and peak II) occur at approximately 135 °C and 185 °C (heating rate 1°Cs) respectively and for both of them the emission band is centered at approximately 380 nm.

Table 2 Lifetime values of peak I and II at different temperatures. The values at 15°C were extrapolated considering the exponential relationship between and the temperature.

Table 1 Trap parameters of peak I and II derived with the Peak Shift (PS) and the Isothermal Decay (ID) method.

Fig. 2 Example of recent building materials used

for the study: roof tile samples with assumed age of 74 and 58 years

respectively.

In thermoluminescence dosimetry, the accidental dose Dx can be assessed as the difference between the total accrued dose DTL and the dose due to the natural sources of radiation absorbed by the sample during its age A:

Accurate measurements of the terms contributing to Dx and of the uncertainties related to each of them were performed in order to establish the limits of the technique and the minimum detectable dose in a realistic scenario of accidental contamination.

envTLCTLx DADDDDDADD

REFERENCES:I. Veronese, A. Giussani, H.Y. Göksu, M. Martini – The trap parameters of electrons in intermediate energy levels in quartz.- Rad. Meas. 38, 743-6, 2004 I. Veronese, A. Giussani, H.Y. Göksu, M. Martini - Isothermal decay studies of intermediate energy levels in quartz – Radiat. Environ. Biophys. 43, 51-7, 2004I. Veronese - The thermoluminescence peaks of quartz at intermediate temperatures and their use in dating and dose reconstruction. Tesi di dottorato in Fisica, Astrofisica e Fisica Applicata, Università degli studi di Milano, XVII CicloI. Veronese, A. Giussani, H.Y. Göksu- Limits of thermoluminescence dosimetry using quartz extracted from recent building materials in urban settlements – J. Env. Radioact. (accepted).

Basic studies of the glow peaks of quartz occurring in intermediate temperature range (150-250°C): measurement of the emission spectrum and determination of lifetimes and trap parameters.

Fig. 3 Variation of the relative uncertainty with the age of the sample for three selected values of Dx, assuming that DTL is evaluated with a typical uncertainty of 5%. The crossed area represents the situation when

xx D. 50

The dotted parts of the lines for Dx=10 mGy and Dx=20 mGy represent the case when the accrued dose is less than the chosen threshold of 40 mGy.

In collaboration with: