Defect Tails in GE Implanted Si Probed by Slow Positrons and Ion Channeling

1998 ◽  
Vol 532 ◽  
Author(s):  
A P Knights ◽  
A Nejim ◽  
N P Barradas ◽  
R Gwilliam ◽  
P G Coleman ◽  
...  
Keyword(s):  
Dose Rate ◽  
Depth Distribution ◽  
Incident Angle ◽  
Dose Range ◽  
Positron Annihilation Spectroscopy ◽  
Average Dose ◽  
Ion Channeling ◽  
Open Volume ◽  
Volume Defect ◽  
Block Distribution

ABSTRACTPositron annihilation spectroscopy has been used to profile the distribution of defects following implantation of 120keV Ge+ into (100) Si in the dose range l x 1010 - lx104 cm−2 . The openvolume defect profiles can be adequately fitted assuming a simple rectangular block distribution extending to 350nm. Using anodic oxidation and etching, a procedure is described which allows details of the defect tails beyond the range of the implanted ion, usually inaccessible to positron -2 annihilation measurements, to be determined. For a time averaged dose-rate (Jr) of 0.02μA cm−2 and incident angle of 7°, open-volume defects are found to exist at concentrations exceeding 1016cm−3 at depths upto 600nm whereas the peak of the depth distribution of the implanted ions (Rp) is 76nm, measured using SIMS. When the time-average dose-rate is increased by a factor of 10, defects persist at concentrations in excess of 1017cm−3 beyond lμm and the Rp increases to 101nm. The open-volume defect profiles are compared to those deduced from Rutherford backscattering-channeling using the fitting routine DICADA.

A Raman Scattering, Ion Channelling and Photoluminescence Study of Argon Ion Radiation Damage in Cu(Ga,In)Se2 - Dose Dependence and Dose Rate Effects

1998 ◽  
Vol 540 ◽  
Author(s):  
G. Lippold ◽  
K. Weinert ◽  
M.V. Yakushev ◽  
R.D. Pilkington ◽  
K. Otte ◽  
...  
Keyword(s):  
Dose Rate ◽  
Radiation Damage ◽  
High Efficiency ◽  
Defect Density ◽  
Lattice Structure ◽  
Dose Range ◽  
Damage Mechanism ◽  
Dose Dependence ◽  
Beam Current Density ◽  
Ion Channeling

AbstractThe ternary chalcopyrite semiconductor CuInSe2 and related ternary compounds are promising materials for the production of high-efficiency thin film solar cells. In this paper we study the dose dependence of ion radiation damage produced by 30 keV and 80 keV Ar ions in single crystals and polycrystalline films of Cu(In,Ga)Se 2 over a wide dose range from 1012 to 1017 cm-2, using Raman spectroscopy and ion channeling measurements. For the first time, we also report on the dose rate dependence with a variation of the beam current density in the range 0.44 to 44 µcm-2. Even for low damage levels no significant dependence of the defect concentration or damage mechanism on the dose rate could be observed. From phonon correlation length considerations we estimate defect densities. They are in agreement with ion channeling data obtained in the 1015 to 1016 dose range, where the breakdown of the lattice structure occurs. In this dose range, the defect density is close to the concentration of implanted atoms. We conclude, that this high impurity concentration is responsible for the amorphization.

scholarly journals Radon Dose Determination and Radiological Risk in Some Mexican Caves with CR-39 Detectors

2021 ◽  
Vol 8 (2) ◽  
pp. 169-175
Author(s):  
A. Chavarria ◽  
J. I. Golzarri ◽  
G. Espinosa
Keyword(s):  
Dose Rate ◽  
Dose Range ◽  
Working Hours ◽  
Decay Chain ◽  
Average Concentration ◽  
Reference Level ◽  
Average Dose ◽  
Radiological Risk ◽  
Annual Dose ◽  
The People

Radon (222Rn) is a radioactive gas, from the 238U decay chain, that contributes in large part of the natural radiation dose to which humans are exposed. Radon is the second cause of lung cancer after tobacco. The US-EPA considers a concentration of 148 Bq/m3 for homes and 400 Bq/m3 for workplaces as the reference level. Caves are closed spaces where 222Rn, which emanates from the surrounding minerals and rocks, can accumulate and reaches large concentrations that can represent a health risk for the guides, speleologists and visitors who spend time in these spaces. This work uses the previously recorded radon concentrations in 8 caves in Mexico and calculates the average dose range and the average annual dose for each of them with the “Wise” public domain program (http://www.wise-uranium.org/rdcrn.html) to determine the level of radiological risk with 2,000 1,000 and 500 working hours per year. Karmidas cave had the highest average 222Rn concentration with 27,633.3 Bq/m3 and for 2,000 working hours per year an average annual dose rate of 347.1 mSv/y. Los Riscos cave had the lowest average concentration with 384.7 Bq/m3 and for 2,000 working hours per year an average annual dose rate of 4.832 mSv/y. These results show that all the caves studied present values,with 2,000 working hours per year, that exceed 3 mSv/y for workplaces and must be considered by the people who work in these places. A casual tourist visiting the caves does not present any radiological risk, while guides and speleologists should consider it.

scholarly journals Thermoluminescent and X-ray diffraction methods in dating of ceramics from archaeological excavations of the Orikti monument (Almaty region)

2020 ◽  
pp. 4-10
Author(s):  
Askar Bakhadur ◽  
Nadezhda Aluker ◽  
Galymzhan Bekseitov ◽  
Yerbolat Ospanov ◽  
Bolat Uralbekov
Keyword(s):  
Dose Rate ◽  
Dose Range ◽  
Sampling Site ◽  
Absorbed Dose ◽  
Average Dose ◽  
Preparation Technique ◽  
X Ray Diffraction ◽  
Absorbed Dose Rate ◽  
X Ray ◽  
Ceramic Samples

In this work, the ages of archaeological ceramics were determined by the thermoluminescent method after X-ray diffraction analysis (XRD) of ceramic samples, which confirms that quartz is the main component phase of the products. This allowed to use the sample preparation technique without isolating the quartz phase from the ceramic sample. Silicon oxide based soil-equivalent thermoluminescent detectors were used to determine the annual absorbed dose rate at the sampling site. The average dose rate at sampling site was 0.62 ± 0.02 cGy/year. Calculation of the ceramics ages was carried out after checking the linearity of lightsums accumulation for samples in the dose range up to 2000 cGy. Based on the performed studies, the ages of the ceramic products were determined that do not contradict to archaeologists dating of these products. It is proposed to use the procedure for determining ceramic samples by the thermoluminescent method after their phase composition identification by XRD. In the case of the predominant mineral composition of quartz phase (the proportion of quartz is more than 60% of the total composition of ceramics), the measurements can be carried out without the quartz isolating; while presence of clay mineral fractions commensurate with quartz levels can lead to the separation of the quartz.

scholarly journals Quantitative Assessment of 3D Dose Rate for Proton Pencil Beam Scanning FLASH Radiotherapy and Its Application for Lung Hypofractionation Treatment Planning

Cancers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 3549
Author(s):  
Minglei Kang ◽  
Shouyi Wei ◽  
J. Isabelle Choi ◽  
Charles B. Simone ◽  
Haibo Lin
Keyword(s):  
Dose Rate ◽  
Treatment Planning ◽  
Organs At Risk ◽  
Patient Treatment ◽  
Average Dose ◽  
Clinical Implementation ◽  
Flash Intensity ◽  
Dose Threshold ◽  
Rate Calculation ◽  
The Impact

To quantitatively assess target and organs-at-risk (OAR) dose rate based on three proposed proton PBS dose rate metrics and study FLASH intensity-modulated proton therapy (IMPT) treatment planning using transmission beams. An in-house FLASH planning platform was developed to optimize transmission (shoot-through) plans for nine consecutive lung cancer patients previously planned with proton SBRT. Dose and dose rate calculation codes were developed to quantify three types of dose rate calculation methods (dose-averaged dose rate (DADR), average dose rate (ADR), and dose-threshold dose rate (DTDR)) based on both phantom and patient treatment plans. Two different minimum MU/spot settings were used to optimize two different dose regimes, 34-Gy in one fraction and 45-Gy in three fractions. The OAR sparing and target coverage can be optimized with good uniformity (hotspot < 110% of prescription dose). ADR, accounting for the spot dwelling and scanning time, gives the lowest dose rate; DTDR, not considering this time but a dose-threshold, gives an intermediate dose rate, whereas DADR gives the highest dose rate without considering any time or dose-threshold. All three dose rates attenuate along the beam direction, and the highest dose rate regions often occur on the field edge for ADR and DTDR, whereas DADR has a better dose rate uniformity. The differences in dose rate metrics have led a large variation for OARs dose rate assessment, posing challenges to FLASH clinical implementation. This is the first attempt to study the impact of the dose rate models, and more investigations and evidence for the details of proton PBS FLASH parameters are needed to explore the correlation between FLASH efficacy and the dose rate metrics.

Raman and ion channeling analysis of damage in ion‐implanted GaAs: Dependence on ion dose and dose rate

1992 ◽  
Vol 71 (6) ◽  
pp. 2591-2595 ◽  
Author(s):  
U. V. Desnica ◽  
J. Wagner ◽  
T. E. Haynes ◽  
O. W. Holland
Keyword(s):  
Dose Rate ◽  
Ion Channeling ◽  
Ion Implanted

Evidence for dose and dose rate effects in human and animal radiation studies

2018 ◽  
Vol 47 (3-4) ◽  
pp. 97-112 ◽  
Author(s):  
M.P. Little
Keyword(s):  
Dose Rate ◽  
Dose Response ◽  
Low Dose ◽  
Atomic Bomb ◽  
Dose Range ◽  
Quadratic Model ◽  
Linear Quadratic ◽  
Dose Rates ◽  
Atomic Bomb Survivors ◽  
Linear Quadratic Model

For stochastic effects such as cancer, linear-quadratic models of dose are often used to extrapolate from the experience of the Japanese atomic bomb survivors to estimate risks from low doses and low dose rates. The low dose extrapolation factor (LDEF), which consists of the ratio of the low dose slope (as derived via fitting a linear-quadratic model) to the slope of the straight line fitted to a specific dose range, is used to derive the degree of overestimation (if LDEF > 1) or underestimation (if LDEF < 1) of low dose risk by linear extrapolation from effects at higher doses. Likewise, a dose rate extrapolation factor (DREF) can be defined, consisting of the ratio of the low dose slopes at high and low dose rates. This paper reviews a variety of human and animal data for cancer and non-cancer endpoints to assess evidence for curvature in the dose response (i.e. LDEF) and modifications of the dose response by dose rate (i.e. DREF). The JANUS mouse data imply that LDEF is approximately 0.2–0.8 and DREF is approximately 1.2–2.3 for many tumours following gamma exposure, with corresponding figures of approximately 0.1–0.9 and 0.0–0.2 following neutron exposure. This paper also cursorily reviews human data which allow direct estimates of low dose and low dose rate risk.

scholarly journals Activity of natural radionuclides and their contribution to the absorbed dose in the fish cubera snapper (lutjanus cyanopterus, cuvier, 1828) on the coast of Ceara, Brazil

2010 ◽  
Vol 58 (spe4) ◽  
pp. 25-32 ◽  
Author(s):  
Wagner de S. Pereira ◽  
Alphonse Kelecom ◽  
Delcy de A. Py Júnior
Keyword(s):  
Dose Rate ◽  
Standard Dose ◽  
Natural Radionuclides ◽  
Absorbed Dose ◽  
Threshold Value ◽  
Average Dose ◽  
Absorbed Dose Rate ◽  
Dose Rates ◽  
A Value ◽  
Lead 210

A methodology was developed for converting the activity concentration of radionuclides (Bq kg-1) into absorbed dose rate (Gy y-1), aiming an approach to environmental radioprotection based on the concept of standard dose limit. The model considers only the internal absorbed dose rate. This methodology was applied to the cubera snapper fish (Lutjanus cyanopterus, Cuvier, 1828) caught off the coast of Ceará. The natural radionuclides considered were uranium-238, radium-226, lead-210, thorium-232 and radium-228. The absorbed dose rates were calculated for individual radionuclides and the type of emitted radiation. The average dose rate due to these radionuclides was 5.36 µGy y-1, a value six orders of magnitude smaller than the threshold value of absorbed dose rate used in this study (3.65 10³ mGy y-1), and similar to that found in the literature for benthic fish. Ra-226 and U-238 contributed 67% and 22% of the absorbed dose rate, followed by Th-232 with 10%. Ra-228 and Pb-210, in turn, accounted for less than 1% of the absorbed dose rate. This distribution is somewhat different from that reported in the literature, where the Ra-226 accounts for 86% of the absorbed dose rate.

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