Radiation shielding design of a compact single-room proton therapy based on synchrotron

A synchrotron-based proton therapy(PT)facility that conforms with the requirement of future development trend in compact PT can be operated without an energy selection system.This article demonstrates a novel radiation shielding design for this purpose.Various FLUKAbased Monte Carlo simulations have been performed to validate its feasibility.In this design,two different shielding scenarios(3-m-thick concrete and 2-m-thick iron–concrete)are proved able to reduce the public annual dose to the limit of 0.1 mSv/year.The calculation result shows that the non-primary radiation from a PT system without an inner shielding wall complies with the IEC 60601-2-64 international standard,making a single room a reality.Moreover,the H/D value of this design decreases from 2.14 to 0.32 mSv/Gy when the distance ranges from 50 to 150 cm from the isocenter,which is consistent with the previous result from another study.By establishing a typical time schedule and procedures in a treatment day for a single room in the simulation,a non-urgent machine maintenance time of 10 min after treatment is recommended,and the residual radiation level in most areas can be reduced to 2.5 lSv/h.The annual dose for radiation therapists coming from the residual radiation is 1 mSv,which is 20%of the target design.In general,this shielding design ensures a low cost and compact facility compared with the cyclotron-based PT system.

Radiation Shielding Performance of Aggregates Made by Sludge with High Content of Heavy Metal

A new method to prepare radiation shielding functional aggregate is described, and an appropriate mix ratio and a reasonable calcinated condition was engaged. The y-ray shielding capability of both the new functional aggregates and some other nature aggregates had been measured. The linear attenuation coefficients （μ, cm-1） of these aggregates had been calculated at photon energies from 1 keV to 10GeV using XCOM program, and measured at the photon energies of 662 keV, showing good agreement between experimental and calculated results. The results show that the y-ray shielding capacity of the new functional aggregates has been improved substantially compared with basalt, almost equal to serpentine and high-titanium slag, and up to 80% to barite.

Comparative Study of Micro and Nano Size WO3/E44 Epoxy Composite as Gamma Radiation Shielding Using MCNP and Experiment

The radiation shielding characteristics of 50wt% WO3/E44 epoxy composite in various gamma energies from 80 keV to 1.33 MeV are investigated via the MCNP code. Thus two scales are considered for WOa filler particles： micro and nano with sizes of i #m and 5Onto, respectively. The simulation results show that W03 nano particles exhibit a larger increase in linear attenuation coefficient in comparison with micro size particles. Finally, validation of simulation results with the published experimental data shows a good agreement.

Development of high performance and high strength heavy concrete for radiation shielding structures

Heavy concrete currently used for construction contains special materials that are expensive and difficult to work with.This study replaced natural aggregate（stones） in concrete with round steel balls,which are inexpensive and easily obtainable.The diameters of the steel balls were 0.5 and 1 cm,and their density was 7.8 kg/m3.Dense packing mixture methods were used to produce heavy concrete with densities of 3500 and 5000 kg/m3.The various properties of this concrete were tested according to the standards of the American Society for Testing and Materials（ASTM）.The results indicated that the construction slump of the concrete could reach 260-280 mm and its slump flow could reach 610-710 mm.More important,its compressive strength could reach 8848 MPa.These results will significantly alter traditional construction methods that use heavy concrete and enhance innovative ideas for structural design.

An Improved Method for Correction of Air Temperature Measured Using Different Radiation Shields

The variation of air temperature measurement errors using two different radiation shields （DTR502B Vaisala,Finland,and HYTFZ01,Huayun Tongda Satcom,China） was studied.Datasets were collected in the field at the Daxing weather station in Beijing from June 2011 to May 2012.Most air temperature values obtained with these two commonly used radiation shields were lower than the reference records obtained with the new Fiber Reinforced Polymers （FRP） Stevenson screen.In most cases,the air temperature errors when using the two devices were smaller on overcast and rainy days than on sunny days; and smaller when using the imported rather than the Chinese shield.The measured errors changed sharply at sunrise and sunset,and reached maxima at noon.Their diurnal variation characteristics were,naturally,related to changes in solar radiation.The relationships between the record errors,global radiation,and wind speed were nonlinear.An improved correction method was proposed based on the approach described by Nakamura and Mahrt （2005） （NM05）,in which the impact of the solar zenith angle （SZA） on the temperature error is considered and extreme errors due to changes in SZA can be corrected effectively.Measurement errors were reduced significantly after correction by either method for both shields.The error reduction rate using the improved correction method for the Chinese and imported shields were 3.3％ and 40.4％ higher than those using the NM05 method,respectively.

Radiation shielding for the first optics enclosure at the High Energy Photon Source beamlines

Purpose The High Energy Photon Source(HEPS)is currently under construction in China and will be the brightest synchrotron radiation facility in the world.To solve the gas bremsstrahlung and synchrotron radiation hazard at HEPS beamlines,a comprehensive radiation study is performed.Method The Monte Carlo method is used to analyze the radiation field in the first optics enclosure at HEPS beamlines.First,the radiation sources including gas bremsstrahlung and synchrotron radiation are estimated.Then,the distribution of the radiation field in the hutch is calculated.Conservative parameters and a typical beamline geometry are used in the calculations.Finally,the shielding recommendations are summarized.Results and Conclusion In this paper,the considerations and bulk shielding design of the first optics enclosure at HEPS beamlines are described.The design satisfies the requirements of the radiation safety principles.

Medium-entropy(Me,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)(Me=Y and Ta):Promising thermal barrier materials for high-temperature thermal radiation shielding and CMAS blocking

With continuous enhancement of gas-turbine inlet temperature and rapid increase of radiant heat transfer,thermal barrier coating(TBC)materials with a combination of low thermal conductivity and good high-temperature thermal radiation shielding performance play vital roles in ensuring the durability of metallic blades.However,yttria-stabilized zirconia(YSZ),as the state-of-the-art TBC and current industry standard,is unable to meet such demands since it is almost translucent to high-temperature thermal radiation.Besides,poor corrosion resistance of YSZ to molten calcia-magnesia-alumina-silicates(CMAS)also impedes its application in sand,dust,or volcanic ash laden environments.In order to improve the hightemperature thermal radiation shielding performance and CMAS resistance of YSZ and further reduce its thermal conductivity,two medium-entropy(ME)oxide ceramics,ME(Y,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)and ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2),were designed and prepared by pressureless sintering of binary powder compacts in this work.ME(Y,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)presents cubic structure but a trace amount of secondary phase,while ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)displays a combination of tetragonal phase(81.6 wt.%)and cubic phase(18.4 wt.%).Both ME(Y,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)and ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)possess better high-temperature thermal radiation shielding performance than YSZ.Especially,the high-temperature thermal radiation shielding performance of ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)is superior to that of ME(Y,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)due to its narrower band gap and correspondingly higher infrared absorbance(above 0.7)at the waveband of 1 to 5μm.The two ME oxides also display significantly lower thermal conductivity than YSZ and close thermal expansion coefficients(TECs)to YSZ and Ni-based superalloys.In addition,the two ME oxides possess excellent CMAS resistance.After attack by molten CMAS at 1250℃for 4 h,merely~2μm thick penetration layer has been formed and the structure below the penetration layer is still intact.These results demonstrate that ME(Me,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)(Me=Y and Ta),especially ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2),are promising thermal barrier materials for high-temperature thermal radiation shielding and CMAS blocking.

Deriving the slope-mean shielded astronomical solar radiation spectrum and slope-mean possible sunshine duration spectrum over the Loess Plateau

Solar radiation is often shielded by terrain relief, especially in mountainous areas, before reaching the surface of the Earth. The objective of this paper is to study the spatial structures of the shielded astronomical solar radiation(SASR) and the possible sunshine duration(PSD) over the Loess Plateau. To this end, we chose six test areas representing different landforms over the Loess Plateau and the software package of Matlab was used as the main computing platform. In each test area, 5-m-resolution digital elevation model established from 1:10,000 scale topographic maps was used to compute the corresponding slope, SASR and PSD. Then, we defined the concepts of the slope-mean SASR spectrum and the slope-mean PSD spectrum, and proposed a method to extract them from the computed slope, SASR and PSD over rectangular analysis windows. Using this method, we found both spectrums in a year or in a season for each of the four seasons in the six test areas. Each spectrum was found only when the area of the corresponding rectangular analysis window was greater than the corresponding stable area of the spectrum. The values of the two spectrums decreased when the slope increased.Furthermore, the values of the stable areas of the spectrums in a year or in a season were positively correlated with the variable coefficients of the slope or the profile curvature. The values of the stable areas of the two spectrums in a year or in a season may represent the minimum value of test areas for corresponding future research on the spatial structures of the SASR or PSD. All the findings herein suggest that the spatial structures of the PSD and the SASR are caused by the interactions between solar radiation and terrain relief and that the method for extracting either spectrum is effective for detecting their spatial structures. This study may deepen our understanding of the spatial structure of solar radiation and help us further explore the distribution of solar energy in mountainous regions.

First principles investigation on Li or Sn codoped hexagonal tungsten bronzes as the near-infrared shielding material

The 52%energy of the solar radiation is contributed by near-infrared radiation(NIR,780-2500 nm).Therefore,the material design for the energy-saving smart window,which can effectively shield NIR and has acceptable visible transmittance,is vital to save the energy consumed on the temperature control system.It is important to find a non-toxic stable material with excellent NIR-shielding ability and acceptable visible transmittance.The systematic first-principles study on Li_(x)Sn_(y)WO_(3)(x=0,0.33,0.66,and y=0,0.33)exhibits that the chemical stability is a positive correlation with the doping concentration.After doping,the Fermi-energy upshifts into the conduction band,and the material shows metal-like characteristics.Therefore,these structures Li_(x)Sn_(y)WO_(3)(except the structure with x=0.33 and y=0)show pronounced improvement of NIR shielding ability.Our results indicate that when x=0 and y=0.33,the material exhibits the strongest NIR-shielding ability,satisfying chemical stability,wide NIR-shielding range(780-2500 nm),and acceptable visible transmittance.This work provides a good choice for experimental study on NIR shielding material for the energy-saving window.

Research on the measurement and shielding methods of the spatial electromagnetic radiation of the BEPCⅡLinac

Purpose The research focuses on the related measurement and shielding works for solving the spatial electromagnetic radiation and interference problems of the BEPCⅡLinac.Methods The radiation frequency and intensity can be determined by using a set of antennas connected with a spectrum analyser.Results The source of the radiation is located on the cable connectors of some device panels.The radiation intensity is significantly reduced after wrapping the connectors with the radiation shielding tape.Conclusions The entire research process includes the selection of a domestically made ultra-wideband antenna,the proposal of the measurement methods,the locating of the radiation source,the performance measurement of the radiation shielding tape and the shielding of the radiation.It provides a whole set of feasible solutions for similar problems in accelerators.

Research Progress of Metal-Based Shielding Materials for Neutron and Gamma Rays

The radiation generated by nuclear reaction is harmful to human body and equipment,thus the radiation shielding materials that employ the shielding ability from neutron and gamma rays are the best candidates according to application situations and radiation sources.In this paper,the researches of metal-based neutron and gamma rays or multiple purpose shielding materials are systematically summarized,and the respective and principal problems of these materials with respect to shielding effectiveness and other performances,such as corrosion,mechanical properties,manufacture,etc.,are discussed.Finally,the prospect of shielding materials is outlined,which suggests that the development of highly efficient and multiply functional radiation shielding materials with good environmental compatibility is one of the future development trends.

Overview and specifications of laser and target areas at the Intense Laser Irradiation Laboratory

We present the main features of the ultrashort, high-intensity laser installation at the Intense Laser Irradiation Laboratory(ILIL) including laser, beam transport and target area specifications. The laboratory was designed to host laser–target interaction experiments of more than 220 TW peak power, in flexible focusing configurations, with ultrarelativistic intensity on the target. Specifications have been established via dedicated optical diagnostic assemblies and commissioning interaction experiments. In this paper we give a summary of laser specifications available to users,including spatial, spectral and temporal contrast features. The layout of the experimental target areas is presented, with attention to the available configurations of laser focusing geometries and diagnostics. Finally, we discuss radiation protection measures and mechanical stability of the laser focal spot on the target.

Radiation protection designs of the linac for the HEPS

Purpose The high-energy photon source(HEPS)is the first fourth-generation light source under construction in China.It is designed to operate at an average current of 200 mA stored beam current with a top-up model at 6 GeV energy.Considering the linac radiation shielding design,a suitable beam loss scenario,optimized thickness for the bulk shielding and detailed structure design for dumps should be proposed.In this paper,the beam loss scenarios were determined and categorized as normal;the dose limits were presented;using these scenarios and the dose limits,the thickness of the linac tunnel was calculated and detailed designs of the main beam dumps were established.The material selection and size setting of the low-power electron beam dump were discussed.Method The Monte Carlo code is a good choice to simulate the radiation analysis.And the iSHIELD11 was used to verify the simulation calculations.Result and conclusion The designs of the linac bulk shield and dumps satisfied the requirements of radiation protection.

Preliminary study on protection of synchrotron radiation damage in CEPC main ring

Background The Circular Election–Positron Collider has been proposed by Institute of High Energy Physics(IHEP,CAS).The beam in the main ring with energy up to 120 GeV would produce intense synchrotron radiation(SR)with photon energy up to several MeV.Without shielding,this radiation would be harmful to the accelerator components.Purpose To clarify the radiation damage,analyze the source of SR,and design the shielding system to protect the accelerator.Methods The theoretical formula has been used to estimate the spectrum and distribution of SR.Several ways of designing or shielding vacuum chamber with different geometries and various materials are put forward to protect sensitive facility components.The Monte Carlo program FLUKA has been introduced to calculate cumulative dose and heat deposition in all designing cases.Results The SR in CEPC main ring would be harmful to the coil used in dipole magnets.The design based on LEP with aluminum and lead would need 23 mm lead to make the coil safe.The design based on LEP with copper would need 28 mm of outer copper.And the copper chamber and lead shield design would need 16 mm of Lead.Conclusion The theoretical formula has been used in source generation of Monte Carlo program to get the distribution of SR in CEPC main ring.The program was also used to simulate SR problems in the vacuum chamber with designs of different geometries and materials.Among these designs,the elliptical pipe with lead shield is preferred in CEPC.

Low melting point MCP-69, MCP-96, MCP-137, and MCP-200 alloys for radiation protection in radiological and therapeutic processes

Objective To evaluate the low melting-point MCP-69,MCP-96,MCP-137,and MCP-200 alloys,and characterize them for their potential to protect from the harms associated with radiation and eliminate radiation hazards during radiological procedures and treatment of cancer.Methods The Klein-Nishina formula was used to calculate the electronic and atomic cross-sections of these alloys using photon beams with energies 4,6,9,12,and 18MeV.Energy transfer coefficients,Compton mass attenuation coefficient,mass-energy transfer coefficient,and recoil energy of electrons in the specific photon energies of 4–18MeV were calculated.The alloys'effective charge number and the photon energy were key factors in determining the properties found by utilizing the Klein-Nishina formula and Compton effects.Results The cross sections and energy transfer coefficients increased with the increasing effective charge number Z of the alloys and decreased as the photon energy increased.The Compton recoil of the ejected electrons was observed to have a direct relationship with photon energy,but mass-energy transfer decreased with increasing photon energy.These alloys can replace the toxic lead for environmentally cleaned radiation applications.Conclusions These calculations and characteristics of the MCP alloys can help further determine their viability as materials for radiation shielding,their use in safe cancer diagnosis,treatment,and environmental hazards protection.

The Characteristic of Dose Equivalent Rates of Photon and Neutron Outside the Treatment Room under High-energy Electron Mode of Linac

Objective:The study aimed to explore the characteristic of dose equivalent rates(DERs)of photon and neutron outside the treatment room under high-energy electron mode(dose rate 1000 MU/min)of linac and to evaluate the effectiveness of treatment room protection.Methods:A 451 P pressurized ion chamber and a thermo neutron detector were used to measure the DERs of the photon and neutron at selected points.The effects of field size,applicator size,applicator,anthropomorphic phantom(CDP)and lead block on DER were investigated respectively.Results:The DERs of a photon at the center of shielding door(point A),control console(point B),primary shielding walls(point C,D)and roof of treatment room(point E)increased with increasing electron energy,but decreased with the increasing field size.The DERs of a photons at points A and B are smaller than 2.5μSv/h for all scenarios,while those at point D greater than 2.5μSv/h when irradiated by 18-22 Me V electron.In addition,CDP may change the DERs of a photon at points C and D about 5% to 30%.On the other hand,the DERs of neutron increase with increasing electron energy but decrease with the increase of field size and applicator size,however,the lead block and the applicator itself will change the DERs of leak neutron at point A,but its amplitude is less than 0.5μSv/h.The maximum DER of neutron at point A is 6.18μSv/h irradiated by 22 Me V electron.For other scenarios,they are all in the range of national standards limits.Conclusion:The DERs of a photon and neutron outside the treatment room mainly depend on the energy,field size and irradiation direction of the electron beam.If high-energy 18 Me V and 22 Me V electron beams will be used,the primary shielding walls and shielding doors need reconstructing or increasing thickness.