Radiation Safety Design for SSRL Storage Ring

In 2003, the Stanford Synchrotron Radiation Laboratory (SSRL) has upgraded its storage ring to a 3rd generation storage ring (SPEAR3). SPEAR3 is deigned to operate at 500 mA stored beam current and 3 GeV energy. The 234-meter circumference SPEAR3 ring utilizes 60-cm-thick concrete lateral walls, 30-cm-thick concrete roof, as well as 60-cm or 90-cm-thick concrete ratchet walls. A total of 3.5 x 10{sup 15} e{sup -}/y will be injected into the ring with an injection power of 4 W and an injection efficiency of 75%. Normal beam losses occur due to both injection and stored beam operations in the total of 20 low loss as well as 3 high loss limiting apertures. During the 6-minutes injection period, an instantaneous power loss of 0.05 W occurs at each low loss aperture. When averaged over the operational year, the loss of both the injection and stored beams is equivalent to an average loss of 2 mW at each low loss aperture. On the other hand, the average losses in the high loss apertures are 16 mW for the injection septum, 47 mW for the beam abort dump, and 13 mW for the ring stoppers. The shielding requirements for losses in the new ring were based on a generic approach that used both FLUKA Monte Carlo particle generation and transport code and empirical computer codes and formulae

Monte Carlo calculations for the ATLAS cavern background

A new application for simulating the ATLAS cavern background was developed. This was done using FLUGG, software that allows Geant4 geometry to be used within the FLUKA simulation framework. A Geant4 description of the ATLAS detector including its cavern was built from scratch for this application. In order to gain computing performance, our geometry is less detailed than that of GeoModel which is used in the full detector simulation, but good enough for the investigation of cavern background. Our geometry can also be used in a standalone Geant4 simulation. Thus it is possible to perform unbiased comparisons between Geant4 and FLUKA using the same complex geometry. We compared neutron and photon fluxes using the FLUKA-FLUGG application with the result of Geant4 simulations based on the QGSP_BERT and QGSP_BERT_HP physics lists. In all cases the same set of initial collision 4-vectors produced by the PHOJET event generator was used. The result from the QGSP_BERT_HP physics list, which uses the High Precision (HP) neutron model, is similar to the result of FLUKA-FLUGG and the differences in the fluxes between them are within 40% in most regions of the ATLAS cavern. The result from the QGSP_BERT physics list, which does not include the HP model, does not agree with either of the previous two results

Code intercomparison and benchmark for muon fluence and absorbed dose induced by an 18-GeV electron beam after massive iron shielding

In 1974, Nelson, Kase, and Svenson published an experimental investigation on muon shielding using the SLAC high energy LINAC. They measured muon fluence and absorbed dose induced by a 18 GeV electron beam hitting a copper/water beam dump and attenuated in a thick steel shielding. In their paper, they compared the results with the theoretical mode ls available at the time. In order to compare their experimental results with present model calculations, we use the modern transport Monte Carlo codes MARS15, FLUKA2011 and GEANT4 to model the experimental setup and run simulations. The results will then be compared between the codes, and with the SLAC data.Comment: 10 pp. Presented paper at the 12th Workshop on Shielding Aspects of Accelerators, Targets and Irradiation Facilities, SATIF-12, Fermilab, April 28-30, 201

Overview of the FLUKA code

Abstract The capabilities and physics models implemented inside the FLUKA code are briefly described, with emphasis on hadronic interaction. Examples of the performances of the code are presented including basic (thin target) and complex benchmarks, and radiation detector specific applications. In particular the ability of FLUKA in describing existing calorimeter performances and in predicting those of future ones, as well as the use of the code for neutron and mixed field radiation detectors will be demonstrated with several examples

Induced Activity Calculations in View of the Large Electron Positron Collider Decommissioning

The future installation of the Large Hadron Collider (LHC) in the tunnel presently housing the Large Electron Positron collider (LEP) requires the dismantling of the latter after more than 10 years of operation. The decommissioning of an accelerator facility leads to the production of large amounts of waste, which in the case of an electron accelerator mostly is of very low level of radioactivity. LEP is classified as Nuclear Basic Installation (Installation Nucleaire de Base, INB) in France, where no unconditional clearance levels are fixed for the specific activity in materials to be released into the public domain. In the case of LEP, the possible sources of induced activity taken here into account are: localized beam losses, distributed beam losses and synchrotron radiation. Reference values of induced specific activity at saturation, normalized to lost beam power, were determined by comparing Monte-Carlo calculations carried out with the FLUKA code and experimental results. These figures are directly employed to estimate the expected amount of low level radioactivity around localized beam loss points in LEP. Regarding the synchrotron radiation, calculations of the total production of radionuclides from photon, thermal neutron and fast neutron activation in the aluminum vacuum chamber, the lead shielding and the magnet pole-faces of a dipole, showed that at beam energies less than 105 GeV, none of the components will be considered as radioactive for decay periods of longer then ten days

Predicting Induced Radioactivity at High Energy Accelerators

Radioactive nuclides are produced at high-energy electron accelerators by different kinds of particle interactions with accelerator components and shielding structures. Radioactivity can also be induced in air, cooling fluids, soil and groundwater. The physical reactions involved include spallations due to the hadronic component of electromagnetic showers, photonuclear reactions by intermediate energy photons and low-energy neutron capture. Although the amount of induced radioactivity is less important than that of proton accelerators by about two orders of magnitude, reliable methods to predict induced radioactivity distributions are essential in order to assess the environmental impact of a facility and to plan its decommissioning. Conventional techniques used so far are reviewed, and a new integrated approach is presented, based on an extension of methods used at proton accelerators and on the unique capability of the FLUKA Monte Carlo code to handle the whole joint electromagnetic and hadronic cascade, scoring residual nuclei produced by all relevant particles. The radiation aspects related to the operation of superconducting RF cavities are also addressed

A Monte Carlo Calculation of Muon Flux at Ground Level from Primary Cosmic Gamma Rays

The Monte Carlo program FLUKA was used to calculate the number of muons reaching detection level in events initiated by primary cosmic gamma ray interactions in the atmosphere. The calculation was motivated by the desire to gauge the sensitivity of arrays like that of Project GRAND to primary gamma cosmic rays while measuring single muons at detection level. Because direct gamma pair production is not a significant source of muons, normally the presence of muons is not considered as a signal for gamma rays. However, due to their non-negligible cross section for hadron production, high-energy gamma rays can initiate hadronic showers containing a large number of pions. These can decay producing secondary muons which then have a good chance of reaching detection level. The complete kinetic energy and space distribution of such muons can be predicted by simulating in detail the whole process by means of Monte Carlo techniques. However, the code used must be capable of handling both hadron-nucleus and photon-nucleus interactions. Unlike most available Monte Carlo particle transport programs, such interactions are implemented in FLUKA, up to several tens of TeV, based on Dual Parton and Vector Meson Dominance models. The FLUKA capability to describe hadronic cascades generated in the atmosphere by primary cosmic hadrons has already been shown in several studies. In the present paper, the investigation has been extended to primary gamma rays. The number of muons per photon is presented as a function of the primary energy in the region between 3 GeV and 10 TeV. As the energy of primary photons rises, their flux falls, whereas the number of muons per gamma rises. Combining these two effects, it can be predicted that gamma ray energies in the 30 GeV region produce the most muons at detection level. The radial and kinetic energy distributions of the muons are also presented

Radiation Transport Calculations and Simulations

This article is an introduction to the Monte Carlo method as used in particle transport. After a description at an elementary level of the mathematical basis of the method, the Boltzmann equation and its physical meaning are presented, followed by Monte Carlo integration and random sampling, and by a general description of the main aspects and components of a typical Monte Carlo particle transport code. In particular, the most common biasing techniques are described, as well as the concepts of estimator and detector. After a discussion of the different types of errors, the issue of Quality Assurance is briefly considered

(M) IMPACT OF GAS BREMSSTRAHLUNG ON SYNCHROTRON RADIATION BEAMLINE SHIELDING AT THE ADVANCED PHOTON SOURCE +

The Advanced Photon Source (APS) currently under construction at Argonne National Laboratory will be one of the world’s brightest synchrotron radiation facilities. The storage ring, capable of storing currents up to 300 mA at 7.0 GeV and 200 mA at 7.5 GeV, will produce very intense and energetic synchrotron radiation (Ec = 24 keV for bending magnets and Ec = 37.4 keV for wigglers, where Ec is the critical energy). The synchrotron radiation (SR) beam lines consisting of experimental enclosures and transport lines will have to be shielded against synchrotron radiation and gas bremsstrahlung scattered from beam line components. For insertion devices placed in the straight sections (length = 15 m), the gas bremsstrahlung produced by the interaction of the primary stored beam with residual gas molecules or ions in the storage ring vacuum chamber dominates the SR beam line shielding. The impact of gas bremsstrahlung on the SR beam line shielding is discussed in this paper