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Mobile Shielding for Collider

#1463


Development of the Conceptual Design and Construction Technologies for the Mobile Shielding of the Highly Radiation Regions in the Future Collider Experiments

Tech Area / Field

  • PHY-PFA/Particles, Fields and Accelerator Physics/Physics

Status
8 Project completed

Registration date
16.02.1999

Completion date
10.10.2005

Senior Project Manager
Glazova M B

Leading Institute
Institute for High Energy Physics (IHEP), Russia, Moscow reg., Protvino

Supporting institutes

  • VNIPI Promtechnology, Russia, Moscow

Collaborators

  • CERN, Switzerland, Geneva

Project summary

It is proposed to use the scientific and technical expertise and unique experience accumulated in the fields of radiation and nuclear physics in order to create an optimal design as well as construction technologies of the mobile radiation shielding for the experiments at high energy accelerators and colliders. This shielding should protect underground experimental hall, detector component, access shafts and communication ways from the hard radiation generated by the high energy particle interactions with accelerator equipment. Space and weight constraints do not allow the use of traditional extensive solutions for design of this shielding. It should be an original development and engineering solution to guarantee the high efficiency of radiation attenuation and ability for fast removal or transformation of this shielding when access to the high precision internal parts of the typical ‘hermetic’ detector is required. The prime purpose of the project is development of the construction technologies development and the conceptual design of the rotation shielding system, including prototyping and tests of this unique equipment, as well as production of the engineering drawings and documentation. Optimal solution for this part of the experimental setup will allow to raise integral efficiency of the whole experiment.

At present the future studies of the fundamental properties of matter revealing in the interactions of high energy particles are related to construction at the very beginning of the next century of the Large Hadron Collider (LHC) at CERN with energy up to 14 TeV and luminocity up to 1034 cm-2s-1. The nominal luminosity of LHC together with the beam energy will create a very hostile radiation environment. There are several experimental facilities to be constructed in the underground halls. One of them, the Compact Muon Solenoid (CMS) detector has been designed to detect the persed signatures from new physics by identifying and precisely measuring muons, electrons and protons over a large energy range and at high luminosity. Muon detection is the most natural and powerful tool to detect interesting events over the background. Radiation damage and high radiation background rates have become a principal design parameters for the new generation large detectors.

Good performance and redundant muon system is one of the main design goals of the CMS project. At the LHC the neutral particle background is very intense. Neutrons and photons produce background hits in the muon chambers by secondary charged particle production. The radiation fields in the experimental hall are dominated by cascade development in the collimator regions. A prerequisite for protecting the muon system is that the collimator is heavily shielded to prevent high energy particles from escaping into the experimental hall. The way to reduce the background in most parts of the muon detectors is utilising a large amount of heavy shielding materials, but this would require massive support structures. Therefore shielding system should be designed that is light enough and still provides acceptable shielding. The shielding efficiency of materials depends on their chemical composition and may be influenced by impurities. For instance, pure iron is not a good neutron shielding material, since it is nearly transparent at some energies. Thus the choice of shielding materials needs to be carefully considered with respect to neutron transmission and energies of capture gamma.

A significant amount of electronics will be placed in the experimental hall outside the detector. In order to estimate the requirements to radiation tolerances of the electronic components, the absorbed dose and neutron flux in the hall has to be determined. Radiation environment in the underground hall will determine the radiation resistance and cost of the electronics.

Accessibility to all parts of the detector for its upgrade, repair or normal maintenance is an essential design criterion. Time available for personnel operation during shutdowns of the accelerator should be raised. To obtain access from the fully closed position of the detector this will require removal of some of the shielding and detectors. Removal of the shielding between the closest focusing quadrupole magnet and the high rapidity forward calorimeter is the first step to the detector opening and forward calorimeter moving. Therefore time for the rotating shielding moving or disassembling should be as short as possible.

For reason of personnel protection in radiation zones all detector parts or materials that may become radioactive have to be identified. Rotating shielding components, placed in the very high radiation environment, will be highly activated. Measures to minimize the levels of the induced radioactivity and to prevent personnel irradiation during access to the detector should be foreseen in the process of the design.

Participating in this Project, a large number of scientists and engineers experienced in the field of nuclear weapons tests and nuclear waste storage will obtain a good opportunity to use their scientific and engineering expertise in resolving the tasks related to the modern fundamental science. Successful realization of this project will open a possibility of wide and long-term participation of the highly qualified staff of ITI in the creation of the large accelerators and experimental facilities and in the radiation safety issues of the High Energy Physics as well as other civil applications. Their very first contract would be construction of Rotating Shielding for the CMS detector at the LHC, and their expertise will appear on the civil market already in the frameworks of commonly acceptable standards and safety requirements.


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