Study On Shielding Design For Beamline Stations At SSRF

Shanghai Synchrotron Radiation Facility, SSRF, is a third-generation synchrotron radiationfacility, consisted of a150MeV LINAC, a3.5GeV booster, a3.5GeV storage ring and beamlinesaround the ring. Presently, Seven beamline stations were built and available for users in Phase Iof SSRF project. Six beamlines belong to project of Dreamline and project of Protein5&6Beamlines are now in commissioning. And16beamlines in Phase II of SSRF project have beenstarted and are now in the stage of feasibility study since2013. There will more than60beamlines at SSRF in the future. The shielding design of beamline is an important part of thebeamline construction. Through rational design of effective radiation shielding materials anddevices, take into account various harmful stray radiation which is produced during theapplication of synchrotron radiation, the radiation dose to the staff working at the beamlinestations can be reduced to be as low as reasonably achievable level.In this study, source terms at SSRF beam-lines are studied by Monte-Carlo simulations.Shielding design for typical beamline stations are present by simulation on radiation dosedistribution based on construction models given by ray trace. The radiation shielding ofrepresentative beamline in Phase I is also re-evaluated. Radiation fields of typical beamlines arestudied by simulations and measurements. Based on these results, the data and methodsapplicable for shielding design of beamline stations are summarized.There are7chapters in this dissertation.In Chapter1and2, Research Status on radiation source terms and shielding designs ofbeamline stations for synchrotron sources in the world were presented. Overview of three maintypes of source terms on beam-line stations were given, which are the gas bremsstrahlunggenerated from electrons in the storage ring interaction with residual gas molecules inside thevacuum; the bremsstrahlung generated from the electron beam loss in the storage ring andinteraction with a device; the synchrotron photon radiation induced by the beam-lines. Themechanism of these three source terms were summarized.The gas bremsstrahlung is the mainshielding target at high-energy accelerator beam-line stations.The structures and layout of the typical beamline stations of SSRF are described in chapter3. These typical beamlines are Protein Micro-crystallography Beamline（BL18U）, UltrahighResolution Wide Range Photoemission Beamline (BL09U and X-ray Imaging and BiomedicalApplications Beamline（BL13W）. The general structure, key instruments, devices and maindesign parameters of the typical beamlines are intruduced from the viewpoint of radiation protection; Main considerations on radiation shielding design for these beamline stations arepresented.In chapter4, shielding design of the beamline stations were carried out by Monte Carlosimulation on radiation dose distribution based on construction models given by ray trace Gasbremsstrahlung produced in straight section vacuum were also simulated. Method forsynchrotron radiation calculation were given.In chapter5, the energy spectra, angle distribution and dose rate of gamma andphoton-neutron produced by gas bremsstahlung are calculated. Radiation shield of BL13W,representative beamline of SSRF phase I, was re-evaluated. Design of two under constructionbeamlines BL09U, and BL18U were carried out by using the ray tracing and the radiation dosedistribution calculation.Experimental measurements of the dose rate of bremsstrahlung and neutron produced byphotonuclear reaction are described in Chapter6. Measurement of radiation dose frombremsstrahlung are carried out by TLDs (thermoluminescent dosimeters) and EPDs (ElectronicPersonal Dosimeters). Dose distribution of optical enclosure of BL18U and BL09U weremeasured by using high sensitive portable dosimeters. The measurement data were comparedwith the calculated data, and showed the measured data are coinsistent with the calculated one.At last Chapter, the characteristic of radiation field of the beamline stations and the methodsusedin the shielding design for these beamline stations are summarized. Following study on theshielding design for the beamline stations at SSRF is also presented.