Modifications of the optical properties for DAM-ADC nuclear track detector exposed to alpha particles

Author’s Accepted Manuscript Modifications of the optical properties for DAMADC nuclear track detector exposed to alpha particles Y.S. Rammah, E.M. Awad www.elsevier.com/locate/radphyschem

PII: DOI: Reference:

S0969-806X(17)30588-1 https://doi.org/10.1016/j.radphyschem.2018.01.004 RPC7734

To appear in: Radiation Physics and Chemistry Received date: 3 June 2017 Revised date: 29 December 2017 Accepted date: 7 January 2018 Cite this article as: Y.S. Rammah and E.M. Awad, Modifications of the optical properties for DAM-ADC nuclear track detector exposed to alpha particles, Radiation Physics and Chemistry, https://doi.org/10.1016/j.radphyschem.2018.01.004 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Modifications of the optical properties for DAM-ADC nuclear track detector exposed to alpha particles Y. S. Rammah*, E. M. Awad Physics Department, Faculty of Science, Menoufia University, 32511 Shebin El-Koom, Egypt

Abstract Modifications of the optical properties of diallyl maleate-allyl diglycol carbonate (DAMADC) nuclear detector induced by alpha particles are described. DAM-ADC samples were irradiated perpendicularly by thin

241

Am disk source that emits alpha particles with 5.48 MeV.

The optical absorption has been measured using the ultraviolet-visible (UV-1100) spectroscopy. It was found that DAM-ADC polymer shows substantial modifications in its optical characteristics upon irradiated with alpha particles with different energies. The optical energy band gap (Egap) for the detector was calculated for the direct and the indirect allowed transitions in K-space using two approaches (Tauc’s model and absorption spectrum fitting (ASF) method). Urbach’s energy (Ea), the number of carbon atoms per conjugated length (N), the number of carbon atoms per cluster (M), and refractive index (n) for the present samples were determined. Results reveal that the values of energy gap in direct transition are greater than those of indirect, before and after irradiation. (Egap), (Ea), (N), (M), and (n) of the present samples are changed significantly with irradiation time and value of alpha energy. Results reflect the possibility of using DAM-ADC polymer track detectors to estimate alpha particle energies using the variation of the absorbance. Keywords: DAM-ADC, UV–visible spectra, energy band gaps, carbon clusters.

Highlights: - DAM-ADC detectors have been irradiated with alpha particles with different energies. - UV–visible spectra has been studied. - Urbach’s energy and energy band gaps have been calculated. - Number of carbon atoms per conjugate length and cluster have been calculated.

1

*

Corresponding authors Y. S. Rammah Physics Department, Faculty of Science, Menoufia University, Shebin El-Koom, Egypt Mobile: 00201007763483 E-Mail: [email protected]

1. Introduction Solid-state nuclear track detectors (SSNTDs) is one of the most important classes of the polymeric materials that have been used in a wide range for radiation detection (Fink and Hnatowicz, 2007). Charged particle spectrometry and particles identification using solid-state nuclear track detectors (SSNTDs) are widely applied in many different fields, including experimental nuclear physics (Durrani and Bull, 1987; Fleischer et al., 1975). SSNTDs have been modified for many applications, such as detection of ion beam, biological filters, sensors and dosimetry (Durrani, 1982; Buford, 2005; Chakarvarti, 2009), radon and progeny measurements (Tommasino, 2001), and alpha particle spectroscopy (Awad et al., 2007, 2008). It is known that, alpha particles causes ionization along its path when it passes through polymer sample and creates damage called a latent track (Nikezic and Yu, 2004). This damage has been due to the scission of polymer chains by incident radiation, cross-linking, formation of carbon clusters and formation of new chemical bonds (Evelyn et al., 1997; Liu et al., 2002; Farinzena et al., 1995). The induced modifications of the solid state nuclear track detector by ionizing radiation (cross linking or main chain scissions) could be investigated by different spectroscopic techniques, the most common one is UV–Visible spectroscopy (Tse, 2006). 2

The main objective of this work is to investigate for first time, the optical characterization through alpha beam-induced structural modifications of DAMADC nuclear detector. α- particles irradiation on DAM-ADC polymer samples,

with different energies,

produced

optical properties that was

investigated using UV–vis spectral analysis. Energy band gaps were calculated using Tauc’s and absorption spectrum fitting (ASF) methods. The dependence of the optical energy gap Egap, number of carbon atoms per length and cluster, and refractive index of the irradiated samples of DAM-ADC detector on alpha energy is studied. 2. Material and Irradiation Facility In the present study, the DAM-ADC detector has the molecular formula [C22 H30O11], with a thickness of 1000 μm and density 1.2 g.cm-3. The main constituents of the DAM-ADC detector plate are the (15% of diallyl maleate and 85% of allyl diglycol carbonate) with polymerizing initiator. This co-polymer detector has been obtained from Yamamoto Kogaku Co., Ltd., Japan (Tsuruta, 2011). DAM-ADC samples with area of 1 cm x 1 cm were carefully cut with laser beam from large sheet. Fig.1a shows the schematic of the repeating unit of ADC and DAM structure. The samples were irradiated by

241

Am disk source that emits alpha

particles with energy 5.48 MeV and activity 0.924 mCi. In order to control of the value of energy of alpha particles, a collimator of cylindrical copper disks was used to control the length of air column; thus energy from 1 to 5 MeV was obtained (see Table 1). Irradiation process was carried out at normal pressure and room temperature. A Schematic representation of the arrangement of the detector, along with the standard source of

241

Am is depicts in Fig. 1b. Alpha particles

residual energy determined by Eq.(1) (Hassib and Amer, 1993);

3

éR - xù E = ê air ë 0.32 úû

0.677

(1)

where E is particle’s energy in MeV, Rair = the range of alpha particle in air at NTP, and x = the source- detector distance in air (cm). UV–Vis spectra of pristine and α-irradiated DAM-ADC samples were measured using UV-visible spectrometer (UVS-2700). All samples were scanned in the wavelengths ranging from 190 to 1100 nm in a step of 1.0 nm, keeping air as a reference.

3. Results and Discussion 3.1.

UV–visible Spectroscopy

Fig.2a shows the optical absorption spectra of unirradiated and alpha irradiated DAM-ADC samples. The spectra depict a shift of absorption edge towards longer wavelength with increasing of alpha irradiated energy which can be readily observed. This shift may be attributed to irradiation-induced defects in the polymeric materials (Singh and Prasher, 2005; Zaki, 2008). Irradiation of DAMADC with different alpha energies induces split of C-C bond and dehydrogenation of the polymer series and thus produces conjugated C=C bonds. Increasing of alpha energy changes the absorption peak to be seen into a broad one; the behavior is discussed as caused by the formation of extended systems of conjugate bonds which creates carbon cluster defects. The increase in the numbers of conjugated C=C with the increase in the alpha energy shifted the absorption band towards higher wavelength. Thus this shift is related also to the structure of the energy band gap of the polymer (Moura et al., 2004). This change in energy band gap leads to an increase in the electrical conductivity of the irradiated polymer sample due to 4

formation of extended system of conjugate double bonds C=C and the formation of a hydroxyl and carbonyl clusters resulted from the energy transferred from the alpha particles to the DAM-ADC detector. The absorption bands in the investigated range of wavelength area are associated to the π-π* electronic transition. This type of transition occurs in the unsaturated center on the molecules which could be containing double or triple bonds and also in aromatics systems. Figure 2b illustrates the variation of the absorbance with alpha irradiation energy at characteristic wavelength of 300 nm. A linear relationship is obtained between the alpha particle energy and the absorbance in the range of 0 to 2 MeV. This linear relationship reflects the possibility of using DAM-ADC polymer track detectors to estimate alpha particle energy using the variation of the absorbance within this range only. 3.2. Optical Energy Band Gap Determination In the present work, from the absorption spectra, the values of the direct and indirect energy band gaps of the pristine DAM-ADC polymers and those irradiated with α-particles were calculated using two methods which are Tauc’s method (Tauc, 1974) which modified by Mott and Davis (Mott and Davis, 1979) and absorption spectrum fitting (ASF) methods (Alarcon et al., 2007; Souri, 2001, 2015). 3.2.1. Optical Absorption Coefficient (α) and Urbach’s Energy (Ea) The optical absorption coefficient (α) of a material is correlated with energy of the incident electromagnetic radiation. The optical absorption coefficient (α) for polycarbonate detector film with thickness (d) in cm can be expressed in terms of absorbance A(hν) by Eq.(2) (Hassib and Amer, 1993);

5

a (hn ) = 2.303

A(hn ) d

(2)

Where (A) is the absorbance defined as A=log (I/Io), Io and I are respectively the intensity of incident and transmitted beams. In this work, the thickness of the present DAM-ADC detector samples is d=0.1 cm. The Urbach’s energy (Ea) which corresponds to the width of the localizedstates tail within an optical band gap gives more details about the optical behavior of the unirradiated and alpha-irradiated DAM-ADC samples. The Urbach’s energy (Ea) can expressed as (Urbach, 1953);

é hn ù ú ë Ea û

a (hn ) = a o exp ê

(3)

Where αo is constant. In order to calculate the values of Urbach’s energy (Ea), the logarithm of the absorption coefficient α(hv) was plotted as a function of the photon energy (hv) for pristine and alpha-irradiated DAM-ADC samples with different energies as shown in Fig.3. The values of the Urbach’s energy (Ea) were calculated by taking the reciprocal of the slopes of the linear portion in the lower photon energy region of these curves as listed in Table2. The decrease in the Urbach’s energy in case of DAM-ADC detector is due to the decrease in the crystalline nature of the polymer. The Urbach’s energy vacillation decreases with increasing alpha energy. This vacillation decrease indicates the irregularization of the band gap energy level; furthermore this is due to amorphous nature of DAMADC polymer.

3.2.2. Optical Energy Band Gaps Determination Using Tauc’s Method

6

The usual method to determine the value of optical energy gaps (Egap) between the valance and the conduction bands of non-crystalline materials is based on the Tauc’s equation (Tauc, 1974). In this method the absorption coefficient α(hν) is expressed as a function of optical energy gap (Egap) and the photons energy (hν) according to Eq.(4): C (hn - E g )

m

a (hn ) =

hn

(4)

where C is a factor depends on the transition probability and can be assumed to be constant within the optical frequency range, m characterizes the transition process in the K-space, which can take the values of 0.5, 1.5, 2, and 3 for direct allowed (DA), direct forbidden (DF), indirect allowed (IA), and indirect forbidden (IF), respectively (Urbach, 1953). However, the indirect and direct allowed band gap energies are evaluated by plotting (αhv)1/m against the photon energy (hv). The IA DA indirect allowed energy band gap E gap and direct allowed energy band gap E gap

was estimated by plotting (αhν)0.5 and (αhν)2.0 as function of the photon energy (hν), respectively as depicted in Figs. 4 and 5. The values of indirect and direct allowed energy band gaps were determined for pristine and alpha-irradiated DAMADC polymer from extrapolating the straight parts of the curves to the photon energy, hv axis. The values of different transition energies are summarized Table 2. One can observed that there is a coexistence of direct and indirect band gaps. There is an irregular decreasing of the band gap energy level in both indirect and direct allowed transition with increasing alpha energy; furthermore this is due to amorphous nature of DAM-ADC polymer. The decrease in band gap energy attributes to the decrease in the resistivity of DAM-ADC detector. This indicates that there is a change in the structural characteristics of DAM-ADC as a result of alpha irradiation. The value of energy gap in the case of indirect transitions are 7

lower than the energy gaps of direct transition, this due the presence of delocalized states between valance and conduction band (El-Badry, 2009). It may accounts for the scission of the polymer chain and formation of free radicals. It is decreasing trend of energy gap with increasing of alpha dose. This is due to the carbon enriched domains (clusters created) in polymer during the irradiation. In other word, these decreases may be attributed to irradiation induced defects and/or increase the number of conjugated bonds (–C=C–). In the wavelength rang 500840 nm studies, the absorptions are associated with π-π* electron transition. The excitation of π electron requires smaller energy and hence, transition of this type occurs at longer wavelengths. 3.2.3. Optical Energy Band gap Determination Using Absorption Spectrum Fitting (ASF) Method Absorption Spectrum Fitting (ASF) (Alarcon et al., 2007; Souri, 2001, 2015) is a method in which the value of the energy band gap for amorphous semiconductors materials can be calculated without the need for measuring the thickness of the film. In this procedure, band gap can be determined only by using the absorbance data of the material. In this method, Eq. (4) can be rewrite as a function of the wavelength (λ) as in Eq. (5) (Souri, 2001, 2015); é1 1 ù a (l ) = B(hc) m-1 l ê ú ëê l l gap ûú

m

(5)

where λgap is wavelength corresponding to the optical gap, h is Planck’s constant, and c is the velocity of the light. By the Beer–Lambert’s law, Eq. (5) can be rewrite as:

8

m

æ1 1 ö÷ A(l ) = D1l ç + D2 çl l ÷ gap ø è

(6)

where D1 = [B(hc) m-1 d / 2.303] and D2 is a constant which takes into account the reflection. Upon using Eq. (6), the optical band gap can be calculated by absorbance spectrum fitting (AFS) method without the need for the film thickness. Thus the value of band gap Egap, in eV, can be calculated from the parameter λgap ASF = hc / l g = 1239.83 / l gap ) . In other word, the value of λgap can using the relation ( E gap

be calculated by extrapolating the linear region of (A/λ) 1/m against. (1/λ) curve at (A/λ)1/m = 0. The variation of (A/ λ)0.5 and (A/ λ)2 against (1/ λ) were plotted as ASF (IA ) illustrated in Figs. 6 and 7, respectively. The values of indirect allowed E gap and ASF (DA) direct allowed E gap energy bands are summarized in Table 3. The results of

ASF band gap for the present samples are in more agreement with which obtained by Tauc’s model (see Table 2). One can notice that the values of energy gaps of indirect and direct band gap in DAM-ADC polymer detector vacillate decreasing with increasing alpha energies.

3.2.4. Number of Carbon Atoms per Conjugation Length (N) and per Cluster (M) It is known that the optical gap energy Egap is correlated with the type, number, and structural arrangement of the carbon bonds per molecule (Fink and Hnatowicz, 2007). For DAM-ADC polymer, the shift of the absorption edge from the ultraviolet to the visible light is probably attributed to a condensation of these rings into a compact carbonaceous clusters which are supposed to be the carriers of conductivity.

9

In a polymer characterized by a linear chain structure such as DAM-ADC polymer. For a linear structure the number of carbon atoms per conjugation length, N, is given by Eq.(7) (Fink et al., 1995); N=

2pb E gap

(7)

where 2β gives the band structure energy of a pair of adjacent π sites and the value of β is taken to be -2.9 eV as it is associated with π–π* optical transitions in –C=C– structure. The number of carbon atoms per conjugate length N in indirect and direct transition was determined using energy gap values which obtained in both Tauc’s and ASF methods for the present samples. The values of N corresponding to the energy gap values are listed in Tables 2 and 3. According to Robertson’s relation, which is modified by Sinha et al. (Sinha et al., 1998) and Fink and Hnatowicz (Fink and Hnatowicz, 2007), the number of carbon atom per cluster, M, is given by: æ 34.3 ö ÷ M =ç ÷ çE g a p ø è

2

(8)

The values for carbon atoms per cluster M in pristine and alpha-irradiated DAMADC samples were calculated using Eq. (9). The M values in both indirect and direct allowed transitions for DAM-ADC detector are listed in Tables 2 and 3. It is clear that the number of carbon atoms per conjugate length, N and the number of carbon atoms per cluster, M for the indirect band gap are higher than that for the direct energy band gap, and their values vacillate increase with increasing alphaenergy. This change could be attributed to cleavages of C–H bonds during the irradiation and, as a consequence, to the release of hydrogen. 3.2.5. Refractive Index Calculated

10

The refractive index, n of the present DAM-ADC samples can be calculated using the obtained values of the energy band gaps for direct and indirect transition in both Tauc’s and ASF methods by the following equation (Dimitrov and Sakka, 1996)

æE ö æ n2 -1 ö çç 2 ÷÷ = 1 - çç gap ÷÷ èn + 2ø è 20 ø

0.5

(9)

The values of refractive index, n for the pristine and alpha-irradiated samples are summarized in Tables 2 and 3 for indirect and direct energy band gaps. The refractive index of the present samples for the indirect band gap more than that for the direct energy band gap, and its value vacillate increases with increasing alphaenergy.

4. Conclusion DAM-ADC nuclear detector shows substantial modifications in its optical characteristics upon irradiated with alpha particles with different energies. These modifications which induced by alpha particles are reported. DAM-ADC samples were irradiated normally to thin

241

Am disk source. The optical absorption spectra

has been measured and show that shifting the peaks of the optical absorption. The optical energy band gaps, Egap for the detectors were calculated for the direct and the indirect allowed transitions in K-space using two methods (Tauc’s model and absorption spectrum fitting (ASF) method). Results reveal that the values of energy gap in direct transition, before and after irradiation, are greater than those for indirect one. Urbach’s energy, the number of carbon atoms per conjugated length (N), the number of carbon atoms per cluster (M), and refractive index (n) for the present samples were determined. It was found that the obtained values of theses 11

parameters are changed significantly with value of alpha energy. Results reflect the possibility of using DAM-ADC polymer track detector to estimate alpha particle energy in the range of 0 to 2 MeV only using the variation of the absorbance. It is recommended that more studies on the modifications of alpha-irradiated DAMADC polymer with different exposure time and energies should be carried out, which will lead to a better understanding of the modification’s mechanism.

12

Table 1: Source-detector distance (cm), and corresponding alpha energy (MeV) Distance (cm)

0

3.6

3.0

2.4

1.5

0.5

Energy (MeV)

0

1.0

2.0

3.0

4.0

5.0

Table 2: Optical band gap, Egap, Urbach energy, Ea, number of carbon atom per conjugated length (N), number of carbon atom per clusters (M), and refractive index (n) for pristine and α-irradiated DAM-ADC samples obtained from Tauc’s method.

Alpha

Optical band gap,

Urbach

Number of carbon

Number of carbon

energy

Egap (eV)

energy, Ea

atom per conjugated

atom per clusters (M)

(eV)

length (N)

(MeV) E

IA gap

E

DA gap

Refractive index (n)

Indirect

Direct

Indirect

Direct

Indirect

Direct

0

3.02

3.46

1.00

∼ 6.0

∼ 5.2

∼ 129

∼ 98

2.39

2.28

1

3.60

3.83

0.33

∼ 5.0

∼ 4.7

∼ 91

∼ 80

2.25

2.20

2

3.64

3.80

0.38

∼ 5.0

∼ 4.8

∼ 89

∼ 81

2.24

2.21

3

3.68

3.85

0.32

∼ 4.9

∼ 4.7

∼ 87

∼ 79

2.23

2.20

4

3.40

3.67

0.71

∼ 5.3

∼ 5.0

∼ 102

∼ 87

2.29

2.24

5

3.57

3.77

0.35

∼5.1

∼4.8

∼ 92

∼ 83

2.25

2.22

13

Table 3: Optical band gap, Egap, Urbach energy, Ea, number of carbon atom per conjugated length (N), number of carbon atom per clusters (M), and refractive index (n) for pristine and α-irradiated DAM-ADC samples obtained from ASF method.

Alpha

Optical band gap,

Number of carbon

Number of carbon

energy

Egap (eV)

atom per conjugated

atom per clusters (M)

(MeV)

Refractive index (n)

length (N) IA E gap

DA E gap

0

3.22

1

Indirect

Direct

Indirect

Direct

Indirect

Direct

3.52

∼ 5.6

∼ 5.2

∼ 113

∼ 95

2.34

2.27

3.59

3.81

∼ 5.1

∼ 5.8

∼ 91

∼ 81

2.25

2.21

2

3.63

3.87

∼ 5.0

∼ 4.7

∼ 89

∼ 79

2.24

2.20

3

3.67

3.88

∼ 4.9

∼ 4.7

∼ 87

∼ 78

2.23

2.19

4

3.41

3.57

∼ 5.3

∼ 5.1

∼ 101

∼ 92

2.29

2.26

5

3.57

3.84

∼ 5.1

∼ 4.7

∼ 92

∼ 80

2.26

2.20

14

References [1] Fink, D., Hnatowicz, V., 2007. Fundamentals of ion-irradiated polymers (Berlin, Germany: Springer Verlag). [2] Durra, S. A., Bull, R. K., 1987. Solid State Nuclear Track Detection (Pergamon Press: Oxford). [3] Fleischer, R. L., Price, P. B., Walker, R. M., 1975. Nuclear Tracks in Solids: Principles and Applications (University of California Press: California). [4] Durrani, S. A., 1982. Nucl. Tracks Radiat. Meas. 6 209. [5] Buford, P. P., 2005. Radiat. Meas. 40 146. [6] Chakarvarti, S. K. 2009. Radiat. Meas. 44 1082. [7] Tommasino, L., 2001. Radiat. Meas. 34 449. [8] Awad, E, M., Soliman, A. A., Rammah, Y. S., 2007. Phys. Lett. A 369 359. [9] Awad, E. M., Soliman, A. A., El-Samman, H. M., Arafa, W. M. Rammah, Y. S., 2008. Phys. Lett. A 372 2959. [10] Nikezic, D., Yu, K. N., 2004. Materials Science and Engineering R 46 51. [11] Evelyn, A. L., Tla, D., Zimmerman, R. L., Bhat, K., Poker, D. B., Hensley, D. K., 1997. Nucl. Instrum. Meth. B 127–128 694. [12] Liu, C., Zhu, Z., Jin, Y., Sun, Y., Hou, M., Wang, Z., Chen, X., Zhang, C., Liu, J., Li, B., Wang, Y., 2002. Nucl. Instrum. Meth. B 166–167 641. [13] Farinzena, L. S., Papaleo, R. M., Hallen, A., de Arauju, M. A., Livi, R. P., Sundquist, B. U. R., 1995. Nucl. Instrum. Meth. B 105 134. [14] Tse, K. C. C., Ng, F. M. F., Yu, K. N., 2006. Polym. Degrad. Stabil. 91:2380. [15] Tsuruta, T., Nakanishi, Y., Shimba, H., 2011. Radiat.Meas. 46 59.

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[16] Hassib, G. M., Amer, H. A., 1993. Nucl. Track. Radiat. Meas. 22 121. [17] Singh, S., Prasher, S., 2005. Radiat. Meas. 40 50. [18] Zaki, M. F., 2008. J Phys D Appl Phys. 41 175404. [19] Moura, E. A. B., Ortiz, A. V., Wiebeck, H., Paula, A. B. A., Silva, A. L. A., Silva, L. G. A., 2004. Radiat Phys Chem. 71 201. [20] Tauc, J., 1974. Amorphous and Liquid Semiconductors, (in: J. Tauc (Ed.), Plenum Press, New York). [21] Mott, N. F. Davies, E. A., 1979. Electronic Processes in Non-Crystalline Materials (Clarendon Press, Oxford). [22] Alarcon, L. E., Arrieta, A., Camps, E., Muhl, S., Rudil, S. Santiago, E, V., 2007. Appl. Surf. Sci. 254 412. [23] Souri, D., 2011. Measurement 44 717. [24] Souri, D., Tahan, Z. E., 2015. Appl. Phys. B 119 273. [25] Urbach, F., 1953. Phys. Rev. 92 1324. [26] El-Badry, B. A., Zaki, M. F., Abdul-Kader, A. M., Hegazy, T. M., Morsy, A. A., 2009. Vacuum 83 1138. [27] Fink, D., Chung, W. H., Klett, R., Schmoldt, A., Cardoso, J., Montiel, R., Vazquez, M. H., Wang, L., Hosoi, F., Omichi, H., Goppelt-Langer, P., 1995. Radiat. Eff. Defects Solids 133 193. [28] Sinha, D., Ghosh, S., Dwivedi, K. K., Fink, D., 1998. Radiat. Eff. Defects Solids 145 45. [29] Dimitrov, V., Sakka, S., 1996 J. Appl. Phys. 79 1736.

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Fig. 1. (a) The monomer structure of ADC and DAM and (b) Schematic representation of the arrangement of the detector, along with the standard source of 241 Am. (adapted from [15,23]).

1

0.8 Pristine DAM-ADC 1 MeV 2 MeV 3 MeV 4 MeV 5 MeV

0.7

Absorbance (A.U)

0.6 0.5 0.4 0.3 0.2 0.1 0 250

300

350

400

450

500

550

600

Wavelength [nm] Fig.2a: UV–visible different energies.

spectra

of

the

pristine

and

alpha-irradiated

DAM-ADC

0.8

Absorbance (A.U)

0.7

R² = 0.9977

0.6 0.5 0.4 0.3 0.2 data

0.1

Linear (data)

0 0

1

2

3

4

5

Alpha energy [MeV] Fig.2b: Characteristics absorbance vs. alpha irradiation energy at 300 nm. 2

6

with

3 0 MeV 1 MeV 2 MeV 3 MeV 4 MeV 5 MeV

2.5

Ln α

2 1.5 1 0.5 0 3.5

3.6

3.7

3.8

Photon energy, hν [eV]

3.9

4

Fig.3: Dependence of natural logarithm of the absorption coefficient (α) on photon energy (hν) for a pristine and alpha-irradiated DAM-ADC detector at different energies.

3

20 Pristine DAM-ADC 1 MeV 2 MeV 3 MeV 4 MeV 5 MeV

(αhν)0.5[cm-1eV]0.5

15

10

5

0 3

3.5

4

Photon energy, hν [eV]

Fig.4: Variation of (αhν)0.5 with (hν) for pristine and DAM-ADC samples irradiated with different alpha energies.

4

2000 Pristine DAM-ADC 1 MeV 2 MeV 3 MeV 4 MeV 5 MeV

(αhν)2[cm-1eV]2

1500

1000

500

0 3

3.5

Photon energy, hν [eV] 4

Fig.5: Variation of (αhν)2 with (hν) for pristine and DAM-ADC samples irradiated with different alpha energies.

5

0.0008 0.0007 0.0006

Pristine DAM-ADC 1 MeV 2 MeV 3 MeV 4 MeV 5 MeV

(A/λ)0.5

0.0005 0.0004 0.0003

0.0002 0.0001 0 0.0025

0.003

0.0035

λ-1, nm-1 Fig.6: Variation of (A/λ)0.5 with (λ-1) for pristine and DAM-ADC samples irradiated with different alpha energies.

6

5E-08

4E-08

Pristine DAM-ADC 1 MeV 2 MeV 3 MeV 4 MeV 5 MeV

(A/λ)2

3E-08

2E-08

1E-08

0 0.0025

0.003

0.0035

λ-1, nm-1 Fig.7: Variation of (A/λ)2 with (λ-1) for pristine and DAM-ADC samples irradiated with different alpha energies.

7