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Radiation measurements
Pergamon Press
Radiation measurements

Pergamon Press

1350-4487

Radiation measurements/Journal Radiation measurementsISTPSCIEIAHCI
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    Tissue-equivalent dosimeters based on copper doped lithium tetraborate single crystals for radiotherapy

    Tiwari, BabitaChaudhary, Rahul K.Srivastava, AnkitKumar, Rajesh...
    10页
    查看更多>>摘要：Advancements in radiotherapy techniques demand the development of stringent quality assurance (QA) pro-tocols and new dosimeters for achieving better accuracy in the measurement of the delivered dose. The objective of the present study is to assess performance of in-house developed tissue equivalent lithium tetraborate (Li2B4O7) single crystal based thermoluminescent dosimeters (TLDs) for medical dosimetry in radiotherapy. For this, single crystals of copper doped lithium tetraborate, abbreviated as LTB:Cu, were grown using the Czo-chralski crystal pulling technique and transparent TLDs of the dimensions 3x3x0.6 mm(3) in chip form were fabricated in our laboratory. Complete dosimetric characterization of TLDs was done to assess its suitability as a dosimeter for radiotherapy dosimetry. The LTB:Cu TLDs were studied for dosimetric properties such as linearity of response with delivered dose, fading, energy dependence, angular dependence and dose rate dependence. The central-axis depth dose parameters such as percentage depth dose (PDD) and output factors were measured using the developed LTB:Cu TLDs for the clinically relevant depths and field sizes and were compared with the response of commercially established TLD-100 and reference values measured by ionisationchamber. Performance of LTB:Cu TLDs has been assessed for their reliable use in dose verification of treatment planning system (TPS) and QA in radiotherapy. The TLDs were used in the clinical set up for measuring the doses to target and critical organs in the in-house developed thorax phantom and the results were compared with the TPS calculated doses. The doses were delivered using three-dimensional conformal radiotherapy (3D-CRT) and volumetric modulated arc therapy (VMAT) techniques. The planned and measured doses agreed within the acceptable limits of 3%. These studies have shown the great potential for the applicability of the developed TLDs in the radiotherapy dosimetry applications.
      原文链接:
    • NSTL
    • Elsevier

    Effect of radiation physics on inherent statistics of glow curves from small samples or low doses

    Lawless, John L.Chen, R.Pagonis, V
    16页
    查看更多>>摘要：A theory is developed to predict statistical noise in the trap populations of small samples or single grains subjected to high-energy ionizing irradiation. Using a model of the radiation process and a one-trap one center model of a thermoluminescent (TL) material, the statistical behavior of the number of occupied traps during irradiation is predicted. The model focuses on the inherent physics of the process. Experimental sources of error are not considered. The interaction of radiation with the TL material is modeled in a simple way using the Bethe equation. The trap and center populations in the TL material are modeled both with the conventional phenomenological equations and also the more general Master Equation approach. The theory predicts, as the irradiation process proceeds, the mean, standard deviation, dispersion, skewness, and kurtosis of the probability distribution of occupied traps in the TL material. For the same applied dose, the standard deviation and dispersion of the trap population depend strongly on the type of radiation as well as the shape and orientation of the material. High-energy radiation sources, such as alpha, beta, or gamma rays, are found to produce standard deviations and dispersion much larger than low-energy sources, such as UV radiation. The results are summarized in tables which enable, for useful limiting cases, easy calculation of not just standard deviation but also skewness and kurtosis for various radiation sources and geometries.
      原文链接:
    • NSTL
    • Elsevier

    A competitive radioluminescence material - LiF:Mg,Cu,P for real-time dosimetry

    Zhang, SiyuanTang, KaiyongFan, HaijunFu, Li...
    5页
    查看更多>>摘要：Currently, common radioluminescent (RL) materials have their own advantages and disadvantages in real-time dosimetry. The most attractive RL materials are tissue equivalent materials with stable sensitivity, weak afterglow, and a wide dose-rate linear range. LiF has a low effective atomic number, and previous studies have reported the RL sensitivity of LiF:Mg,Ti is dose-dependent. LiF:Mg,Cu,P can also emit RL during irradiation, which may be used for real-time dose monitoring. The purpose of this paper is to investigate dose characteristics of RL in LiF:Mg,Cu,P based on a developed optical fiber system and a commercial TL/OSL reader (Ris phi TL/OSL-DA-20C/D). The results indicated that the RL sensitivity of LiF:Mg,Cu,P is not as good as Al2O3:C, but comparable to LiF:Mg,Ti. It can be inferred that LiF:Mg,Cu,P is suitable for high dose rate measurements. LiF:Mg,Cu,P showed almost a constant sensitivity to absorbed dose and a weak afterglow signal, which implies the accurate dose rates can be obtained quickly without sensitivity corrections. In addition, LiF:Mg,Cu,P has a good linear dose-rate response ranging from 0.76 mGy/h to 8.02 Gy/h, similar to LiF:Mg,Ti, and a superior repeatability (~1.36%) to LiF:Mg,Ti. In conclusion, LiF:Mg,Cu,P is a competitive RL material for real-time dosimetry with its own advantages.
      原文链接:
    • NSTL
    • Elsevier

    Dose response of visible color center radiophotoluminescence in lithium fluoride crystals irradiated with a reference Co-60 gamma beam in the 1-20 Gy dose range

    Piccinini, M.Nichelatti, E.Pimpinella, M.De Coste, V...
    4页
    查看更多>>摘要：The visible radiophotoluminescence response of radiation-induced stable F-2 and F-3(+) color centers in nominally pure lithium fluoride crystals, irradiated with a reference Co-60 gamma beam in the 1-20 Gy dose range, was carefully investigated. After irradiation, the Stokes-shifted emission spectra of the colored crystals were measured as a function of time under continuous laser excitation at 445 nm and in stationary conditions. The F-2 radiophotoluminescence intensity remains constant; the signal, spectrally integrated in a 50 nm-wide interval centered on the F-2 emission peak at 670 nm, exhibited a linear dependence on the absorbed dose with a good signal-to-noise ratio, stability for multiple readout and long storage times. Combined with our previous in-vestigations after irradiation at similar doses with low-energy protons and clinical X-ray beams, these experi-mental results confirm the feasibility of passive solid-state dosimeters for radiotherapy based on color center radiophotoluminescence in nominally pure lithium fluoride crystals.& nbsp;
      原文链接:
    • NSTL
    • Elsevier

    Recombination pathways in a BeO yielding two main dosimetric TL peaks

    Konstantinidis, P. G.Tsoutsoumanos, E.Polymeris, G. S.Kitis, G....
    7页
    查看更多>>摘要：Apart from the commercially used Thermalox, BeOR is a new type of Beryllium Oxide fabricated by a different company in Turkey. As it is shown by other groups, this dosimeter yields two overlapping main dosimetric TL peaks in the temperature region of 100-300 degrees C and one peak at 350 degrees C. The aim of the present study is the calculation of the activation energies of these two peaks with the use of specific protocols, including the Frac-tional Glow Technique (FGT), an Isothermal Decay signal (PID) and the Peak Shape Methods (PSM). Also, these experimental procedures were conducted in two different readers, namely the Harshaw and the Risa reader, for better repeatability and in order to minimize the error of the calculations. Moreover, another goal is to correlate the activation energy values with the recombination pathways that are present in the BeOR and its corresponding peaks. Specifically, both peaks have activation energies around 1-1.3 eV in most cases, although there are some kinds of indications for a difference in the pathways, as the high-temperature region TL main peak seems to follow the localized recombination via tunneling, in contrast with the low-temperature region TL main peak which sticks to the delocalized model with the passing via the conduction band.
      原文链接:
    • NSTL
    • Elsevier

    Characterization of the neutron/y-ray discrimination performance in an EJ-301 liquid scintillator for application to prompt fission neutron spectrum measurements at CSNS

    Zhang, ZhenhuaWang, HaoqiangZhu, KunLiu, Zijun...
    6页
    查看更多>>摘要：The FIssion Neutron spectrum Detector Array (FINDA) has been designed for measurement of prompt fission neutron spectrum on the Back-n beam line at the China Spallation Neutron Source (CSNS). In order to test the neutron-y discrimination performance of the EJ301 scintillator that will be used as a detector unit in the FINDA, a comparative study using three conventional digital pulse shape discrimination (PSD) methods has been carried out. An Am-Be source has been used to generate the mixed neutron-y radiation and the waveform data has been obtained with a fast digitizer. Pulse interpolation, baseline restoration and pulses pile-up rejection have been applied for digital pulse processing. Charge comparison (CC) method and simplified charge comparison(SCC) method show a better capability of neutron-y discrimination than rise time comparison(RTC) method over the entire energy range. Rise time comparison method needs a very fast digitizer or pulse interpolation to improve the PSD ability. The analysis of neutron-y discrimination performance of the EJ301 scintillator provides a strong technical support for fast neutron measurement using the FINDA at CSNS.
      原文链接:
    • NSTL
    • Elsevier

    Image sorting of nuclear reactions recorded on CR-39 nuclear track detector using deep learning

    Tashiro, KenNoto, KazukiNizam, Quazi Muhammad RashedBenton, Eric...
    5页
    查看更多>>摘要：Deep learning has been utilized to trace nuclear reactions in the CR-39 nuclear track detector. Etch pit images on front and back surfaces of the CR-39 detector were obtained sequentially by moving the objective lens of a microscope, and merged to one image. This image merging makes it possible to combine information on the displacement of the position of the etch pits produced by single particle traversals through a CR-39 layer in a single image, thereby making it easier to recognize corresponding nuclear fragmentation reactions. Object detection based on deep learning has been applied to the merged image to identify nuclear fragmentation events for measurement of the total charge changing cross-section based on the number of incident particles (N-in) and the number of particles that passed through target without any nuclear reaction (N-out). We verified the accuracy (correct answer rate) of algorithms for extracting the two patterns of etch pit in merged images which corresponds to N-in and N-out using the learning curves expressed as a function of the number of trainings. Accuracy of N-in and N-out were found to be 97.3 +/- 4.0% and 98.0 +/- 4.0%, respectively. These results show that the object detection algorithm based on the deep learning can be a strong tool for CR-39 etch pit analysis.
      原文链接:
    • NSTL
    • Elsevier

    Measurement of the energy spectrum of laser-accelerated protons using FNTD: Development of an easy and quick method for energy spectrometry

    Kusumoto, TamonInoue, ShunsukeOgawara, RyoKodaira, Satoshi...
    5页
    查看更多>>摘要：This paper reports the derivation of energies of proton beams accelerated by an intense laser using a fluorescent nuclear track detector (FNTD), which is Al2O3 single crystal doped with C and Mg. Using the FNTD, we acquire 3D images of incoming tracks easily, consecutively and rapidly and we can follow the fluorescence intensity of the proton tracks towards their terminals. By counting the number of proton tracks that disappeared at a certain depth, we determine the range of the tracks. Then, we evaluate energies of incoming protons from the evaluated range. The maximum energy of accelerated proton is 3.3 MeV. The results obtained from FNTD measurements are in good agreement with those obtained from the relationship between the incident energy and the distance calculated from the spatial distribution of the magnetic field. The FNTD provides the energy spectrum quickly after the laser shot within few hours, much faster than conventional nuclear track detectors such as CR-39 plastic and nuclear emulsion detectors, which require several days due to the chemical treatments needed. The FNTD is a promising detector for the diagnosis of beams accelerated by an intense laser, which generates a complex mixed radiation field.
      原文链接:
    • NSTL
    • Elsevier