ISIS is a pulsed neutron spallation source located at the Rutherford Appleton Laboratory (UK). The 163 m circumference rapid cycling (50 Hz) synchrotron accelerates 3E13 protons per pulse from 70 to 800 MeV and then delivers these to one of two neutron producing target.
Over the past year there has been a concerted effort to improve understanding of activation of certain accelerator components. This is important as it may help to understand and improve beam setup and tuning procedures, impart extra knowledge for maintenance and help plan for future upgrades to the facility.
Three main projects have been completed so far: a study of the specific activity of W-187 within the second neutron producing target, a study of the activation and residual dose rate of the ISIS beam collimation system (compared to measurements) as reported at IPAC'14, and a study of the impact in terms of beam scattering and activation of the intermediate muon producing target in our proton beamline.
Details of these three projects will be discussed, outlining the approach, results and challenges faced and solved. Our future plans for the use of the FLUKA code within the group will also be discussed (eg potential projects including beam scattering through a thin charge stripping foil located in a strong magnetic field, characterisation of beam loss monitors and scintillator diagnostics, calculating the concentration of tritium in neutron target cooling water, etc)
Status of the FAIR pbar target
At FAIR, a proton beam from the SIS100 synchrotron with a kinetic energy of 29 GeV will be used for the pbar production. Every 10 seconds 2.5E13 protons will be accelerated in the SIS100 to 29 GeV and a bunch of 50 ns duration will be formed. Antiprotons will be produced in collision of these protons with a nickel target. Immediately behind the target, a pulsed magnetic horn will be placed to collect the antiprotons emerging from the target with energies around 3 GeV and within a cone of about 80 mrad.
Due to the high activation during the antiproton production a transport concept for the activated components has to be developped since only remote handling is possible. Recent FLUKA calculations of the prompt and the remanent dose of the tarets station itself and the handling components are presented. Also the work on the collimator design of the antiproton beamline by using Fluka is discussed briefly.
Comparisons of Prompt Radiation Fields and Material Activations Induced by Four Accelerators in Taiwan
With an increasing number of large accelerator facilities in Taiwan, the dose assessment and measurement technology for accelerator radiation becomes more and more important. The accelerators of interest include a 3-GeV electron synchrotron in National Synchrotron Radiation Research Center, a 235-MeV proton therapy accelerator in Chang Gung Memorial Hospital, a proposed 400-MeV/A carbon ion therapy accelerator in Taipei Veterans General Hospital, and a 30-MeV high-current proton cyclotron that may be used for an accelerator-based boron neutron capture therapy facility. Radiation fields associated with an accelerator operation differ considerably to those around nuclear power plants or radionuclides in many aspects, such as mixed radiation fields, wide-range energy distributions and specific time structures. These problems result in challenging difficulties in dose assessment and associated radiation measurements. I would like to conduct a comprehensive study on !
the characteristics of prompt and residual radiation fields induced by the operation of the four accelerators. In addition to high-fidelity FLUKA simulations of radiation generation and transport, a high-efficiency neutron spectrometer will be established to measure neutron spectra in workplaces. Key items of my study include: (1) simulations and measurements of prompt radiation induced by accelerator operation, (2) residual activities and remnant doses caused by accelerator radiation induced material activation, (3) general guidelines or suggestions for accelerator radiation protection in Taiwan.
Simulation of the FERMI electron beam dump
The presentation covers a simulation of the radiation field around the 1.4-GeV electron beam dump of the FERMI free-electron laser. Electromagnetic and neutron dose rates are calculated and in good agreement with ionisation chamber and superheated drop detector measurements. The simulation uses magnetic fields, several types of biasing, and a few LATTICE elements.
Simulation of Bremsstrahlung spectra in general targets and its application to a model of a laser-driven irradiation source
A model for bremsstrahlung production in targets of variable length is being developed by means of FLUKA simulations. Laser-accelerated electron beams, which have recently been proved as an alternative for conventional particle accelerators in tumor irradiation, usually have a broad energy distribution, thus depriving thin and thick targets approximations of sense. Discussing technical aspects include a priori determination of appropriate length scale, the use of USERWEIG to substantially reduce the number of simulations of the naive approach, and a package in development for reading and plotting FLUKA-generated files with Mathematica.
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 beamdump and attenuated in a thick steel shielding. In their paper, they compared the results with the theoretical models available at the time. In order to compare their experimental results with present model calculations, we use the modern transport Monte Carlo codes to model the experimental setup and run simulations. The results will then be compared between the codes, and with the SLAC data.
Monte Carlo simulation of the 60Co Calliope irradiation facility with FLUKA
The Calliope irradiation facility, located in the ENEA Casaccia research center, is a large pool-type irradiation plant capable of processing different kind of samples, even biased electronics and detectors. The activity of the facility is focused on the radiation hardness measurement of materials and components for space and high-energy physics applications. The irradiation hall is 6x7 m2 wide and is 2 m high, the radioactive source is composed by several cylindrical 60Co bars arranged in a circular rack located at the center of the hall. The peculiar structure of this facility allows to use a variety of dose rates for the irradiation, starting from few kGy/h and down to few Gy/h. The complex structure of the irradiation hall, with support structures and lead shieldings, and the free-positioning of the samples, calls for a detailed simulation of the radiation field in order to build a dose rate map of the entire plant. Fluka can be used to simulate the entire f!
acility, including in the geometry the fixed and movable elements of the plant and the extended 60Co sources. A grid of dose rate values will be evaluated to build a map of the irradiation hall. This map will be validated with dosimetric measurements inside the hall, continuously updated to follow the source decay, and then will be used to locate the irradiation position with the desired dose rate.
Simulation of a high sensitivity neutron detector
Neutrons constitute an important component of the radiation environment. Their energy distribution may span from thermal up to hundreds of MeV. This paper describes the simulation of a high sensitivity Bonner Sphere neutron detector uses a 3He counter tube inside a polyethylene moderator which is a part of a scientific research project named distributed dynamic radioactive detection imaging system belongs to The Ministry of science and technology of the PRC major instrument development special. For the purpose of the characterization of the response, a detailed model of the detector was developed by FLUKA Monte Carlo simulations. Several combinations of materials and different sphere diameters was investigated also.
FLUKA simulations of the radiation environment at the CMS detector at the LHC
FLUKA is used in the Beam Radiation Instrumentation and Luminosity project (BRIL) of CMS to simulate the radiation levels due to proton-proton collisions. Results are used by the whole CMS collaboration for various applications: Comparison with detector hit rates, pile-up studies, predictions of radiation damage based on various models (Dose, NIEL, DPA), shielding design, estimations of residual dose environment etc.
For specific needs, additional programs were developed, of which some will be shown.
A python based web plotting framework was developed to share FLUKA results of common interest with collaborators. Users can select plotting options on a website and create 2D flux and dose maps. Binary USRBIN result files are loaded by the web server and visualized using Matplotlib. The plotting code is specialized for the needs of CMS, but the concept can be generalized and could be of interest for other collaborations, where FLUKA results are shared.
The built-in FLUKA one-step method for simulating residual dose environment due to activation is heavily used. However, this method does not allow a geometry modification in between the prompt and the decay step (except for the removal of elements). During interventions in the central parts of CMS, the detector is brought into an open configuration. A two-step simulation framework was developed, where in a prompt step the creation of radioactive isotopes are simulated in a closed scenario. A manipulation of the geometry can then be performed using a graphical user interface, where the list of isotopes is modified according to the geometry modifications. The modifications include the moving of elements, the removal of elements, and the installation of additional elements like shielding. In a second simulation step of the modified geometry, the decay radiation is simulated to obtain the residual dose environment in the opening scenario. The concepts of this method could be of !
interest for any simulations of residual dose environments, where elements are moved, or where shielding is installed after irradiation.
Parallelization of Fluka simulations in hadrotherapy
In the TOP-IMPLART project framework (a joint project between ENEA, ISS and IFO), several simulations have been carried out on the ENEA GRID infrastructure, in order to place the basis for the development of a fast Treatment Plan System (TPS) and in order to develop the accelerator beam monitor system. Fluka parallelization has been performed, allowing run on GRID infrastructure and reducing greatly the computing time.
FLUKA dose distribution simulations for TULIP, TUrning LInac for Protontherapy
Fluka simulations to optimize the distance between the isocenter and the position of the last scanning magnet in order to reduce the skin dose to the patient.
-Integration between FLUKA and TRAVEL, a multi-particle tracking software developed at CERN.
-Dose simulations in phantoms/patients performed using a simulated beam from a proton Linac for therapy, with an active scanning system and Bragg's Peak spot depth variations obtained varying the energy in the Linac.
-Implementation of the rotation of a gantry in FLUKA.
(TERA Foundation (IT))
Shielding design for the electron tunning beam Dump
The upcoming ARIEL facility at TRIUMF will have a new electron beam line, delivering a maximum of 500 kW beam (10 mA at 50 MeV) to one of the target stations in the newly built target hall for Rare Isotope Beam (RIB) production. In preparation for this, a tunning beam dump (BD) is designed and located upstream in the electron hall. This tunning beam dump will be in use until the completion of the electron beam transport line to the target station and the target itself.
Due to the limited availability of the space and accessibility to the BD through a hatch above the beam dump, the shielding needs to be compact and remote-handleable. The production version of FLUKA was utilized to determine an optimum solution in terms of shielding material and configuration, given the above constraints. The design of the shielding was divided into two stages: local shielding and upstream (EHDT) shielding. The beam dump will be operated under two different irradiation conditions: 1) 1.3 mA at 75 MeV and 2) 4 mA at 25 MeV. Since the first case results in higher radiation fields, it was used in the simulations for shielding design. Simulation results showed a layered design, consisting of low Z, high Z material, to be the most effective in reducing the dose rates. Taking into account the radiation hardness of the shielding material available (given the radiation fields outside the BD) and magnetic properties of the shielding material, the final design c!
onsisted of a lead enclosure around the BD, followed by slabs of concrete and carbon steel. Designing the upstream shielding required employing the two-step method where particles crossing the local upstream end of the shielding were written out in the first step and used as the source in the second step. This saved considerable time evaluating different configurations of shielding for the EHDT area, while the beam line components and their position along the beamline were still under design and changing.
FLUKA was also used to extract power deposition in the BD and the shielding immediately surrounding the dump. This information was used as input into ANSYS for thermal and stress analysis. The second beam conditions were used in these studies since due to the shorter range of electrons in the beam dump, it poses a worse case in terms of energy deposition in the dump. FLUKA was also used to determine activation of the BD components and the shielding and the residual dose rates from the activation of these components.
Since the BD insert may need to be moved for service, a casket is required for its transport to a hot cell or storage area. The development version of FLUKA was used to find the minimum thickness of carbon steel or lead required to satisfy the dose rate limit specified.
This talk will cover the procedures and steps involved in completing the above.
Accurate Monte Carlo modeling of biomedical cyclotrons: optimization of FLUKA physics and transport parameters for dosimetry, shielding and activation calculations
Knowledge of the radiation field around biomedical cyclotrons is necessary for the design of shieldings, the classification of areas and the protection of the workers, the public and the environment. In recent years, Monte Carlo simulations have been used to create models able to predict, with good approximation, the radiation field around these accelerators. Since the complexity of the physical phenomena involved in the transport of radiation, the validation of these models with experimental measurements is necessary to be able to predict accurate results. The availability of Monte Carlo (MC) codes with up to date and accurate libraries for transport and interactions of neutrons and charged particles at energies below 250 MeV, as well as continuously increasing power of recent computers, allow the systematic use of simulations with realistic geometries in order to obtain equipment and site specific evaluation of the source terms, shielding requirements and othe!
r quantities relevant to radiation protection. In this work FLUKA has been used in order to model two types of cyclotron for Positron Emission Tomography (PET) radionuclides production, the General Electric PETrace (16.5 MeV) and ACSI TR19 (19 MeV), including their targetry, and one type of proton therapy cyclotron, the Varian/Accel 250isc, including the energy selection system. Simulations allow for estimation of several relevant quantities, like the effective dose distribution around the equipment; the effective number of neutron produced per incident proton and neutron spectral distribution; the activation of the structure of the cyclotron, the energy degrader and the vault walls; the activation of the ambient air, in particular for the production of 41Ar; alternative mixtures of shielding materials have been simulated and tested. Moreover, Monte Carlo simulations have been extensively used to study the feasibility of the direct cyclotron production of non-standard radio!
nuclides such as 89Zr and 99mTc through, respectively, the 89Y!
r and the 100Mo(p,2n)99mTc reactions. Monte Carlo simulations have been validated against experimental measurements. Particular emphasis has been given to the choice of physics and transport parameters that allow to obtain results in agreement with the experimental measurements. Furthermore, critical aspects and problems encountered during the modelling will be discussed as well as the solutions that have been found.