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The yields, branching ratios and angular distributions of 6–7 MeV photons produced in the 19F(p,αγ)16O reaction
Applied Radiation and Isotopes 56 (2002) 877–882
The yields, branching ratios and angular distributions of 6–7 MeV photons produced in the 19F(p,ag)16O reaction Shengyao Dinga,*, Kun Xua, Hongyan Wangb a
Ionizing Radiation Division, Institute of Atomic Energy, P.O. Box 275(20), Beijing 102413, People’s Republic of China b Radiation Metrology Center of Nuclear Industry, P.O. Box 183, Shijiazhuang 050002, People’s Republic of China Received 27 November 2000; received in revised form 23 February 2001; accepted 17 April 2001
Abstract The yields and branching ratios of 6.13, 6.92 and 7.12 MeV photons produced in the 19F(p,a!g)16O reaction were measured for incident proton energies between 340.46 and 3490 keV. The experimental data were recorded and analysed to show photon features. The branching ratios of 6.13, 6.92 and 7.12 MeV g-rays are different for different incident proton energies. The maximum yield of 6–7 MeV g-rays was found at Ep ¼ 2:63 MeV. The angular distributions for 6.13 and 7.12 MeV g-rays in the Ep ¼ 340:46 keV resonance were also measured and show to be isotropic within experimental uncertainty. r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Photon yield; Branching ratio; Angular distribution
1. Introduction The low-lying resonance in the 19F(p,ag)16O reaction has been studied by numerous workers. A variety of works have been published on both fundamental and applied areas, including nuclear spectroscopy, nuclear structure calculation, proton beam energy calibration, and nuclear astrophysics. The large body of data has been assembled and reviewed by Ajzenberg-Selove (1987). By comparison, relatively few experimental data of yields, branching ratios and angular distributions of 6–7 MeV photon produced in the 19F(p,ag)16O reactions have so far been published, even though those data provide the important value for ionizing radiation metrology. In addition, both ISO 4037-1 (1996) and ISO 4037-2 (1997) declared that the photon radiation from deexcitation of 16O in the 19F(p,ag)16O reaction is an important part of the photon reference radiation for the energy region between 4 and 9 MeV. As we know, the absolute calibrations of NaI(Tl), Ge(Li) and HpGe *Corresponding author. Fax : +86-10-6935-7178. E-mail address: [email protected] (S. Ding).
detectors by means of a-associated particle counting in the 19F(p,ag)16O reaction induced by proton beam with Ep ¼ 340:46 keV have been performed in NRCC, Canada (Mach and Rogers, 1983) and CIAE, China(Ding et al., 1992). Also the calibrations of dose meters and dose rate meters have been undertaken with 6–7 MeV photons emitted in the 19F(p,ag)16 O reaction induced by proton beam with Ep ¼ 2:7 MeV (Rogers, 1983; Duvall, 1985; Guldbake and Sch.affler, 1990). With the aim of obtaining more useful data for detector calibration with 6–7 MeV photons, the yields, branching ratios and angular distributions for 6– 7 MeV photons emitted in the 19F(p,ag)16O reaction have been studied in both 2 1.7 mV tandem accelerator and 600 kV Cockcroft–Walton accelerator of CIAE, China.
2. Experiment The main measurements were carried out in the experimental hall of the 2 1.7 mV tandem accelerator of CIAE. The photograph of the experimental arrangement is shown in Fig. 1. All of the experimental
0969-8043/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 9 - 8 0 4 3 ( 0 1 ) 0 0 0 9 2 - 6
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S. Ding et al. / Applied Radiation and Isotopes 56 (2002) 877–882
3. Results 3.1. Yields and branching ratios of 6–7 MeV photons in the bombardment by 2 1.7 mV tandem accelerator
Fig. 1. Photograph of the experimental arrangement.
instruments were set on the grid net, which was made of aluminium, for reducing the back scattering from the concrete ground. The distance between the grid net and the concrete ground is 2.0 m. There is a semicircular iron track on the aluminium net around the target from 301 to +1501. The detectors set on the carts can smoothly move along both the semicircular track and the straight track between the detector and the target. A precise position of each detector can be set up by adjusting the support both vertically and horizontally. Two detector systems were employed for this measurement: a HpGe detector with 120 cm3 active volume and a NaI(Tl) detector with F10 10 cm. The distance is 95 cm between HpGe and target, and 146 cm between NaI(Tl) and target. A 180 mg/cm2 CaF2 target with 2 mm thick tantalum backing was used. The proton beam current from tandem accelerator was limited to less than 5 mA during the measurement. A beam monitor was used for the relative normalization. In order to obtain the significant events of 6.916 and 7.115 MeV g-rays, the measurements of branching ratios and angular distributions of 6–7 MeV photon for Ep ¼ 340:46 keV resonance were carried out in the experimental hall of Cockroft–Walton accelerator. The hall with 10 m 20 m 6 m dimension provides low scattering background. The proton beam current was elevated to 40 mA during the Ep ¼ 340:46 keV resonance measurements. The NaI(Tl) detector was used as a monitor for normalization. It was located at 201 to the beam direction and 200 cm from the target. The principal detector was HpGe spectrometer at a distance of 36 cm from the target. The HpGe detector was kept at the same distance around the target in the measurement of angular distribution.
The pulse-height distributions of 6.129, 6.916 and 7.115 MeV g-rays emitted in the 19F(p,ag)16O reaction for the incident proton energy region from Ep ¼ 340 to 3490 keV were recorded by both HpGe and NaI(Tl) detectors. The results for the HpGe detector are shown in Fig. 2. Some salient features are clear in Fig. 2. The full-energy, single escape and double escape peaks associated with the 6.129 MeV transition stand out most prominently below Ep ¼ 838 keV. With the proton energy increase, the peaks associated with 6.916 and 7.115 MeV transitions become prominent and are clearly Doppler– broadened, and the yields of the 6–7 MeV photon obviously increased. To obtain the branching ratios of 6.129, 6.916 and 7.115 MeV g-rays, a total of 20 pulse-height spectra of 6–7 MeV g-rays were investigated for the incident proton energy region from Ep ¼ 1348 to 3490 keV. The results are shown in Table 1. For every individual spectrum, the background events were subtracted, the single pulse-height spectrum was analyzed from the complex spectra by a deconvolution method, and the net peak area was obtained. The total peak area was the sum of the areas of full energy, single escape and double escape peaks. One should correct the photon peak area by normalizing to the detector efficiency (Ye et al., 1994). The data listed in Table 1 are very useful for calibrating g-ray detectors as well as dose meters. It is obvious that the 6.129 MeV g-ray is prominent below Ep ¼ 1:7 MeV. Above Ep ¼ 1:7 MeV, the main g-ray is changeable from one spectrum to another, but in most cases, the yield of 7.115 MeV g-rays is prominent. Generally, the maximum yields of 6–7 MeV photons are used for routine calibration. However, the air collision kerma (Ka ) is dependent on not only the photon yield, but also photon energy, according to the following equation (ISO 4037-2, 1997): Ka ¼
X
Ei Fi ðm% tr =rÞi ;
i
where Ei is the ith interval photon energy, FI is the photon fluence in this interval EI ; and ½u#tr =rI is the average mass energy-transfer coefficient in this interval. Incident proton of Ep ¼ 2:7 MeV bombarding a thick CaF2 target have been used for calibrating dose meters or dose rate meters by many laboratories (Rogers, 1983; Guldbake and Sch.affler, 1990).
S. Ding et al. / Applied Radiation and Isotopes 56 (2002) 877–882
Fig. 2. Gamma ray spectra for the reaction of Ep ¼ 340234900 keV protons with thin CaF2 target.
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S. Ding et al. / Applied Radiation and Isotopes 56 (2002) 877–882
Table 1 The branching ratios of 6.13, 6.92 and 7.12 MeV g-rays and their total relative yield ratios (%) with incident proton energies from Ep ¼ 1348 to 3490 keV Ep (kev)
Eg ¼6.129 (MeV)
Eg ¼6.916 (MeV)
Eg ¼7.115 (MeV)
1348 1374 1554 1607 1694 1800 1948 2030 2200 2320 2400 2510 2630 2700 2800 2900 3020 3190 3200 3490
22.3 76.2 12.7 10.2 28.0 10.6 9.7 12.0 7.7 19.7 15.1 29.9 37.2 12.7 24.0 11.0 10.2 16.3 18.0 18.5
10.9 11.5 1.5 3.7 12.6 4.3 12.5 7.4 18.4 30.2 42.8 17.6 18.8 22.0 16.6 9.8 24.5 50.7 45.4 13.3
9.8 4.3 0.8 2.1 6.4 7.1 57.8 76.6 62.9 43.1 12.1 35.5 44.0 31.3 30.4 19.2 13.2 19.0 24.6 18.2
43.0 92.0 15.0 16.0 47.0 22.0 80.0 96.0 89.0 93.0 70.0 83.0 100.0 66.0 71.0 40.0 48.0 86.0 88.0 50.0
3.2. Branching ratios and angular distributions for 19 F(p,ag)16O reaction at Ep ¼ 340:46 keV resonance The high-energy region of a typical pulse-height distribution recorded by a HpGe spectrometer positioned at 551with respect to the proton beam direction is shown in Fig. 3. The full-energy, single escape and double escape peaks associated with 6.129, 6.916 and 7.115 MeV transitions are marked. The relative yield of the 6.129, 6.916 and 7.115 MeV g-rays is: I6:129 : I6:916 : I7:115 ¼ 0:9686 : 0.0036 : 0.0268, our result thus is similar to the corresponding results of 0.9701 : 0.0033 : 0.0266 (Croft, 1991), as well as to 0.9686 : 0.0055 : 0.0269 (Ajzenberg-Selove, 1987). The angular distributions of the 6.129 and 7.115 MeV g-rays are illustrated in Figs. 4 and 5, respectively. In both cases the experimental data have been corrected and normalized to the results of NaI(Tl) monitor. Both angular distributions are consistent with isotropy within the experimental uncertainty. Reliable angular distribution data for 6.916 MeV transition could not be obtained in the experimental time available because of its low intensity.
Fig. 3. A typical pulse-height distribution recorded by HpGe detector. The abbreviations FE, SE and DE refer to full energy, single escape and double escape peak features respectively.
S. Ding et al. / Applied Radiation and Isotopes 56 (2002) 877–882
881
Fig. 4. The angular distribution of 6.13 MeV gamma-rays.
Fig. 5. The angular distribution of 7.12 MeV gamma-rays.
4. Summary The yields, branching ratios and angular distributions of 6.13,6.92 and 7.12 MeV photons produced in the 19 F(p,ag)16O reaction have been measured. The results show the following features: The yields of 6.13, 6.916 and7.12 MeV photons vary with incident proton energies. The yields increase, in general with the incident proton energy increase except at some resonances. The maximum yield is found in Ep ¼ 2:63 MeV.
The Doppler effects are seen in Figs. 2 and 3. The wide pulse-height distributions are observed in photon high-energy region, especially for 6.92 and 7.12 MeV gray spectra. The reason is the lifetimes of 6.92 and 7.12 MeV g-ray levels (4.7 and 8.3 fs respectively), which are much shorter than that of 6.13 MeV g-ray level (18.4 ps). The Doppler broadening can be suppressed by coating the CaF2 target with thin aluminium film (Mach and Rogers, 1983; Ding et al., 1992). The branching ratios of 6.13, 6.92 and 7.12 MeV g-ray are different for different incident proton energies. In the
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S. Ding et al. / Applied Radiation and Isotopes 56 (2002) 877–882
low proton energy region, 6.13 MeV g-rays are salient. With the proton energy increase, the 6.92 and 7.12 MeV g-rays increase, until the yield of 7.12 MeV g-rays becomes the main part (Fig. 2). The angular distributions of 6.13 and 7.12 MeV g-rays in the resonance reaction of Ep ¼ 340:46 keV are both isotropic, which are similar with the results of Croft (1991).
References Ajzenberg-Selove, F., 1987. Energy levels of light nuclear A: 18–20. Nucl. Phys. A 475, 1. Croft, S., 1991. The absolute yield, angular distribution and resonance widths of the 6.13, 6.92 and 7.12 MeV photons from 350 keV resonance of the 19F (p,ag) 16O reaction. Nucl. Instrum. Methods A 307, 353–1358. Ding, S., et al., 1992. The establishment of quasi-monoenergetic 6–7 MeV g-ray reference radiation field and the absolute calibration for g-ray detector efficiency at Eg=MeV. At. Energy Sci. Technol. 26 (6), 9–16.
Duvall, K.C., et al., 1985. The development of a 6–7 MeV photon calibration source. Nucl. Instrum Methods B 10/11, 942–945. Guldbake, S., Sch.affler, D., 1990. Properties of high-energy photon fields to be applied for calibration purposes. Nucl. Instrum. Methods A 299, 367–371. ISO 4037-1, 1996. First Edition 1996-12-15 X and gamma reference radiation for calibrating dosemeters and doserate meters and determining their response as a function of photon energy Part 1: radiation characteristics and production methods. ISO 4037-2, 1997. First Edition 12–15 Part 2: dosemetry for radiation protection over the energy ranges 8 keV to 1.3 MeV and 4–9 MeV. Mach, H., Rogers, D.W.O., 1983. An absolute calibrated source of 16.13 MeV Gamma rays. IEEE Trans. Nucl. Sci. 30 (2), 1514–1517. Rogers, D.A., 1983. A nearly mono-mergetic MeV photon calibration source. Health Phys. 45 (1), 127–137. Ye, Z., et al., 1994. Intrinsic efficiencies and g-dose determinations for HpGe detector at MeV region. At. Energy Sci. Technol. 28, 419–427.
The yields, branching ratios and angular distributions of 6–7 MeV photons produced in the 19F(p,ag)16O reaction Shengyao Dinga,*, Kun Xua, Hongyan Wangb a
Ionizing Radiation Division, Institute of Atomic Energy, P.O. Box 275(20), Beijing 102413, People’s Republic of China b Radiation Metrology Center of Nuclear Industry, P.O. Box 183, Shijiazhuang 050002, People’s Republic of China Received 27 November 2000; received in revised form 23 February 2001; accepted 17 April 2001
Abstract The yields and branching ratios of 6.13, 6.92 and 7.12 MeV photons produced in the 19F(p,a!g)16O reaction were measured for incident proton energies between 340.46 and 3490 keV. The experimental data were recorded and analysed to show photon features. The branching ratios of 6.13, 6.92 and 7.12 MeV g-rays are different for different incident proton energies. The maximum yield of 6–7 MeV g-rays was found at Ep ¼ 2:63 MeV. The angular distributions for 6.13 and 7.12 MeV g-rays in the Ep ¼ 340:46 keV resonance were also measured and show to be isotropic within experimental uncertainty. r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Photon yield; Branching ratio; Angular distribution
1. Introduction The low-lying resonance in the 19F(p,ag)16O reaction has been studied by numerous workers. A variety of works have been published on both fundamental and applied areas, including nuclear spectroscopy, nuclear structure calculation, proton beam energy calibration, and nuclear astrophysics. The large body of data has been assembled and reviewed by Ajzenberg-Selove (1987). By comparison, relatively few experimental data of yields, branching ratios and angular distributions of 6–7 MeV photon produced in the 19F(p,ag)16O reactions have so far been published, even though those data provide the important value for ionizing radiation metrology. In addition, both ISO 4037-1 (1996) and ISO 4037-2 (1997) declared that the photon radiation from deexcitation of 16O in the 19F(p,ag)16O reaction is an important part of the photon reference radiation for the energy region between 4 and 9 MeV. As we know, the absolute calibrations of NaI(Tl), Ge(Li) and HpGe *Corresponding author. Fax : +86-10-6935-7178. E-mail address: [email protected] (S. Ding).
detectors by means of a-associated particle counting in the 19F(p,ag)16O reaction induced by proton beam with Ep ¼ 340:46 keV have been performed in NRCC, Canada (Mach and Rogers, 1983) and CIAE, China(Ding et al., 1992). Also the calibrations of dose meters and dose rate meters have been undertaken with 6–7 MeV photons emitted in the 19F(p,ag)16 O reaction induced by proton beam with Ep ¼ 2:7 MeV (Rogers, 1983; Duvall, 1985; Guldbake and Sch.affler, 1990). With the aim of obtaining more useful data for detector calibration with 6–7 MeV photons, the yields, branching ratios and angular distributions for 6– 7 MeV photons emitted in the 19F(p,ag)16O reaction have been studied in both 2 1.7 mV tandem accelerator and 600 kV Cockcroft–Walton accelerator of CIAE, China.
2. Experiment The main measurements were carried out in the experimental hall of the 2 1.7 mV tandem accelerator of CIAE. The photograph of the experimental arrangement is shown in Fig. 1. All of the experimental
0969-8043/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 9 - 8 0 4 3 ( 0 1 ) 0 0 0 9 2 - 6
878
S. Ding et al. / Applied Radiation and Isotopes 56 (2002) 877–882
3. Results 3.1. Yields and branching ratios of 6–7 MeV photons in the bombardment by 2 1.7 mV tandem accelerator
Fig. 1. Photograph of the experimental arrangement.
instruments were set on the grid net, which was made of aluminium, for reducing the back scattering from the concrete ground. The distance between the grid net and the concrete ground is 2.0 m. There is a semicircular iron track on the aluminium net around the target from 301 to +1501. The detectors set on the carts can smoothly move along both the semicircular track and the straight track between the detector and the target. A precise position of each detector can be set up by adjusting the support both vertically and horizontally. Two detector systems were employed for this measurement: a HpGe detector with 120 cm3 active volume and a NaI(Tl) detector with F10 10 cm. The distance is 95 cm between HpGe and target, and 146 cm between NaI(Tl) and target. A 180 mg/cm2 CaF2 target with 2 mm thick tantalum backing was used. The proton beam current from tandem accelerator was limited to less than 5 mA during the measurement. A beam monitor was used for the relative normalization. In order to obtain the significant events of 6.916 and 7.115 MeV g-rays, the measurements of branching ratios and angular distributions of 6–7 MeV photon for Ep ¼ 340:46 keV resonance were carried out in the experimental hall of Cockroft–Walton accelerator. The hall with 10 m 20 m 6 m dimension provides low scattering background. The proton beam current was elevated to 40 mA during the Ep ¼ 340:46 keV resonance measurements. The NaI(Tl) detector was used as a monitor for normalization. It was located at 201 to the beam direction and 200 cm from the target. The principal detector was HpGe spectrometer at a distance of 36 cm from the target. The HpGe detector was kept at the same distance around the target in the measurement of angular distribution.
The pulse-height distributions of 6.129, 6.916 and 7.115 MeV g-rays emitted in the 19F(p,ag)16O reaction for the incident proton energy region from Ep ¼ 340 to 3490 keV were recorded by both HpGe and NaI(Tl) detectors. The results for the HpGe detector are shown in Fig. 2. Some salient features are clear in Fig. 2. The full-energy, single escape and double escape peaks associated with the 6.129 MeV transition stand out most prominently below Ep ¼ 838 keV. With the proton energy increase, the peaks associated with 6.916 and 7.115 MeV transitions become prominent and are clearly Doppler– broadened, and the yields of the 6–7 MeV photon obviously increased. To obtain the branching ratios of 6.129, 6.916 and 7.115 MeV g-rays, a total of 20 pulse-height spectra of 6–7 MeV g-rays were investigated for the incident proton energy region from Ep ¼ 1348 to 3490 keV. The results are shown in Table 1. For every individual spectrum, the background events were subtracted, the single pulse-height spectrum was analyzed from the complex spectra by a deconvolution method, and the net peak area was obtained. The total peak area was the sum of the areas of full energy, single escape and double escape peaks. One should correct the photon peak area by normalizing to the detector efficiency (Ye et al., 1994). The data listed in Table 1 are very useful for calibrating g-ray detectors as well as dose meters. It is obvious that the 6.129 MeV g-ray is prominent below Ep ¼ 1:7 MeV. Above Ep ¼ 1:7 MeV, the main g-ray is changeable from one spectrum to another, but in most cases, the yield of 7.115 MeV g-rays is prominent. Generally, the maximum yields of 6–7 MeV photons are used for routine calibration. However, the air collision kerma (Ka ) is dependent on not only the photon yield, but also photon energy, according to the following equation (ISO 4037-2, 1997): Ka ¼
X
Ei Fi ðm% tr =rÞi ;
i
where Ei is the ith interval photon energy, FI is the photon fluence in this interval EI ; and ½u#tr =rI is the average mass energy-transfer coefficient in this interval. Incident proton of Ep ¼ 2:7 MeV bombarding a thick CaF2 target have been used for calibrating dose meters or dose rate meters by many laboratories (Rogers, 1983; Guldbake and Sch.affler, 1990).
S. Ding et al. / Applied Radiation and Isotopes 56 (2002) 877–882
Fig. 2. Gamma ray spectra for the reaction of Ep ¼ 340234900 keV protons with thin CaF2 target.
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S. Ding et al. / Applied Radiation and Isotopes 56 (2002) 877–882
Table 1 The branching ratios of 6.13, 6.92 and 7.12 MeV g-rays and their total relative yield ratios (%) with incident proton energies from Ep ¼ 1348 to 3490 keV Ep (kev)
Eg ¼6.129 (MeV)
Eg ¼6.916 (MeV)
Eg ¼7.115 (MeV)
1348 1374 1554 1607 1694 1800 1948 2030 2200 2320 2400 2510 2630 2700 2800 2900 3020 3190 3200 3490
22.3 76.2 12.7 10.2 28.0 10.6 9.7 12.0 7.7 19.7 15.1 29.9 37.2 12.7 24.0 11.0 10.2 16.3 18.0 18.5
10.9 11.5 1.5 3.7 12.6 4.3 12.5 7.4 18.4 30.2 42.8 17.6 18.8 22.0 16.6 9.8 24.5 50.7 45.4 13.3
9.8 4.3 0.8 2.1 6.4 7.1 57.8 76.6 62.9 43.1 12.1 35.5 44.0 31.3 30.4 19.2 13.2 19.0 24.6 18.2
43.0 92.0 15.0 16.0 47.0 22.0 80.0 96.0 89.0 93.0 70.0 83.0 100.0 66.0 71.0 40.0 48.0 86.0 88.0 50.0
3.2. Branching ratios and angular distributions for 19 F(p,ag)16O reaction at Ep ¼ 340:46 keV resonance The high-energy region of a typical pulse-height distribution recorded by a HpGe spectrometer positioned at 551with respect to the proton beam direction is shown in Fig. 3. The full-energy, single escape and double escape peaks associated with 6.129, 6.916 and 7.115 MeV transitions are marked. The relative yield of the 6.129, 6.916 and 7.115 MeV g-rays is: I6:129 : I6:916 : I7:115 ¼ 0:9686 : 0.0036 : 0.0268, our result thus is similar to the corresponding results of 0.9701 : 0.0033 : 0.0266 (Croft, 1991), as well as to 0.9686 : 0.0055 : 0.0269 (Ajzenberg-Selove, 1987). The angular distributions of the 6.129 and 7.115 MeV g-rays are illustrated in Figs. 4 and 5, respectively. In both cases the experimental data have been corrected and normalized to the results of NaI(Tl) monitor. Both angular distributions are consistent with isotropy within the experimental uncertainty. Reliable angular distribution data for 6.916 MeV transition could not be obtained in the experimental time available because of its low intensity.
Fig. 3. A typical pulse-height distribution recorded by HpGe detector. The abbreviations FE, SE and DE refer to full energy, single escape and double escape peak features respectively.
S. Ding et al. / Applied Radiation and Isotopes 56 (2002) 877–882
881
Fig. 4. The angular distribution of 6.13 MeV gamma-rays.
Fig. 5. The angular distribution of 7.12 MeV gamma-rays.
4. Summary The yields, branching ratios and angular distributions of 6.13,6.92 and 7.12 MeV photons produced in the 19 F(p,ag)16O reaction have been measured. The results show the following features: The yields of 6.13, 6.916 and7.12 MeV photons vary with incident proton energies. The yields increase, in general with the incident proton energy increase except at some resonances. The maximum yield is found in Ep ¼ 2:63 MeV.
The Doppler effects are seen in Figs. 2 and 3. The wide pulse-height distributions are observed in photon high-energy region, especially for 6.92 and 7.12 MeV gray spectra. The reason is the lifetimes of 6.92 and 7.12 MeV g-ray levels (4.7 and 8.3 fs respectively), which are much shorter than that of 6.13 MeV g-ray level (18.4 ps). The Doppler broadening can be suppressed by coating the CaF2 target with thin aluminium film (Mach and Rogers, 1983; Ding et al., 1992). The branching ratios of 6.13, 6.92 and 7.12 MeV g-ray are different for different incident proton energies. In the
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S. Ding et al. / Applied Radiation and Isotopes 56 (2002) 877–882
low proton energy region, 6.13 MeV g-rays are salient. With the proton energy increase, the 6.92 and 7.12 MeV g-rays increase, until the yield of 7.12 MeV g-rays becomes the main part (Fig. 2). The angular distributions of 6.13 and 7.12 MeV g-rays in the resonance reaction of Ep ¼ 340:46 keV are both isotropic, which are similar with the results of Croft (1991).
References Ajzenberg-Selove, F., 1987. Energy levels of light nuclear A: 18–20. Nucl. Phys. A 475, 1. Croft, S., 1991. The absolute yield, angular distribution and resonance widths of the 6.13, 6.92 and 7.12 MeV photons from 350 keV resonance of the 19F (p,ag) 16O reaction. Nucl. Instrum. Methods A 307, 353–1358. Ding, S., et al., 1992. The establishment of quasi-monoenergetic 6–7 MeV g-ray reference radiation field and the absolute calibration for g-ray detector efficiency at Eg=MeV. At. Energy Sci. Technol. 26 (6), 9–16.
Duvall, K.C., et al., 1985. The development of a 6–7 MeV photon calibration source. Nucl. Instrum Methods B 10/11, 942–945. Guldbake, S., Sch.affler, D., 1990. Properties of high-energy photon fields to be applied for calibration purposes. Nucl. Instrum. Methods A 299, 367–371. ISO 4037-1, 1996. First Edition 1996-12-15 X and gamma reference radiation for calibrating dosemeters and doserate meters and determining their response as a function of photon energy Part 1: radiation characteristics and production methods. ISO 4037-2, 1997. First Edition 12–15 Part 2: dosemetry for radiation protection over the energy ranges 8 keV to 1.3 MeV and 4–9 MeV. Mach, H., Rogers, D.W.O., 1983. An absolute calibrated source of 16.13 MeV Gamma rays. IEEE Trans. Nucl. Sci. 30 (2), 1514–1517. Rogers, D.A., 1983. A nearly mono-mergetic MeV photon calibration source. Health Phys. 45 (1), 127–137. Ye, Z., et al., 1994. Intrinsic efficiencies and g-dose determinations for HpGe detector at MeV region. At. Energy Sci. Technol. 28, 419–427.