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.

Analysis of gamma-emitting radionuclides in soils around high energy accelerators

Objective To investigate the specific activities of gamma radionuclides in the soils around high energy accelerators,and to analyze the influence of rays emitted by nuclides with characteristic peaks at similar energy points on nuclide measurement results,in order to provide reference for the accurate identification of radionuclides.Methods GR5021 high-purity germanium gamma spectroscopy system was used to measure the specific activities of gamma-emitting radionuclides 226Ra,232Th,238U,40K and artificial radionuclides 54Mn,52Mn,7Be,22Na,59Fe,95Zr in six soil samples around three kinds of high energy accelerators,and the theoretical counts of the characteristic peak of 835.7keV were compared with the measured counts of the characteristic peak of 54Mn.Results The specific activity ranges of gamma-emitting radionuclides 226Ra,232Th,238U and 40K in the soils around three kinds of high energy accelerators were 55.5–171,34.9–99.9,21.9–79.3 and 247–680 Bq/kg,respectively.The specific activities of artificial radionuclides 52Mn,7Be,22Na,59Fe and 95Zr were basically lower than the minimum detection limit.A characteristic peak was found at the energy point of 835.7keV in six soil samples,and the corresponding total absorption peak counts were from 228Ac of 232Thdecay daughter.Conclusions The specific activities of gamma-emitting radionuclides were at the normal natural background levels.The specific activities of artificial radionuclides were basically lower than the minimum detection limits.For 232Th,when its specific activity is above 40 Bq/kg,characteristic peak of its decay daughter 228Ac could be misjudged as characteristic peak of 54Mn.

Conceptual design of the CEPC dumping system

Background The circular electron–positron collider(CEPC)is a double-ring collider proposed by Chinese scientists.It will be operated at centre-of-mass energy of 240,90,160 GeV and maybe also 360 GeV.Purpose The total energy stored in the collider is up to 20 MJ.It is important to extract beams safely and not to damage the dump.In this paper,a dumping system including dilution kickers and absorber core with iron shielding is discussed.Methods The Monte Carlo code FLUKA is used to obtain the deposited energy and dose-equivalent distributions.The temperature rises are calculated assuming no heat conduction.Results Compared with the melting point and upper limit of dose equivalent,the magnets parameters are determined and the dimensions of the core and shielding are optimized.Conclusion The design of the dumping system meets the requirement that the energy stored in the collider can be absorbed safely.

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.

Energetic particles’fluxes and dose in the Radiation Gene Box measured by space radiation detector onboard SJ-10 satellite

Background To evaluate the hazard of space radiation posing to the tissues,it is important to obtain exact fluxes of different radiation particles.The Radiation Gene Box(RGB)onboard SJ-10 spacecraft was an instrument designed to investigate the effects of space environment on the mESCs and drosophila.To derive the dose received by the tissues inside the RGB,the Space Radiation Detector(SRD)was installed inside it.Purpose The SRD was designed to derive the fluxes of electron,proton,hellion and gamma rays around it.If the type of the particles,the energies,the fluxes and the conversion coefficients are known,the dose received by the tissues could be evaluated.Methods The SRDwas designed as a △E-E solid-state telescope.By measuring the energy deposited in the three subdetectors,the particles’type and their energies could be discriminated.The data of SRDwere divided into 15 bins by the types of particles and their energy ranges.Results The gamma ray flux was higher than any other particle flux inside the RGB,and the electron was the most intense charge particle,while the helium ion was the most harmful radiation to the cells inside the RGB.Conclusion The dose rate inside the Radiation Gene Box was much higher than in the ground,but the integral dose of 12 days inside the RGB was about 2.13 mSv.It seemed unlikely to have obvious biological effects on the tissues of mice and drosophila.

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.