Project Overview

 

This design specification describes a new experimental facility and accelerator modifications required to take advantage of heavy-ion beams from the Brookhaven AGS Booster accelerator for radiation effects studies of importance for the Space Program.

Radiation fields encountered in space may cause deleterious effects in humans, and these effects are of special concern for prolonged space missions beyond the protective terrestrial magnetosphere.  Before such missions can be undertaken, a much more detailed under-standing of these effects is required to allow planning and implementation of protective countermeasures.

Of particular concern are the radiation effects due to the heavy ion components of the galactic cosmic ray spectrum.  Shielding of entire spacecraft against these very energetic and very penetrating particles is not practical and the expected dose rates are as high as 30 to 50 rad/year.  There is great uncertainty regarding the risks associated with such high dose rates.  The relative biological effectiveness (RBE) or the risk weighting of energetic heavy ions are not known, and there are even serious doubts about the validity of such concepts.  At the very least it is thought that such factors can be very different for different organs and for different biological effects such as mutagenesis, carcinogenesis and cell necrosis.  Many more studies with cells, tissue and animals are required to reach adequate estimates of radiation-associated risks to humans in space.  Such studies can best be conducted under controlled, ground-based conditions by utilizing energetic ion beams from accelerators.  Complementary studies are also being performed in space but these are much more difficult, complicated and expensive.  

The Brookhaven AGS Booster is an ideal accelerator for these studies due to the good overlap between the available ion masses and energies with those encountered in space.  A variety of high-z-energy (HZE) particles will be available with energies ranging from a maximum of 1.3 GeV/amu for the lightest ions, to approximately 1.1 GeV/amu for iron and approximately 300 MeV/amu for gold, to a minimum of less than 100 MeV/amu.

Heavy ions will originate in the Brookhaven MP-6 tandem accelerator and be transported to the Booster synchrotron for acceleration to the required energies.  Figure 1 is a schematic diagram of the accelerator complex at BNL, including existing and proposed facilities, and the heavy ion transfer lines connecting them.

Concurrent operation of the Booster for space radiation research and other kinds of research applications will be achieved by utilizing independent tandem injectors.  The beam species and energy for both applications will be independent.   Beams from either Tandem will be switched into the common injection line.  At the Booster a new slow extraction system will be implemented which will require extensive accelerator modifications and rearrangements.  A new beam line and tunnel enclosure will be built to transport the extracted beam to the experimental facility.  Uniform beam intensities will be provided over rectangular areas ranging in size from about 1 cm to about 20 cm.

The experimental facility will be housed in a well shielded irradiation area and in a support building containing ready-rooms, laboratories, and offices.  Other existing on-site facilities, such as the Medical Departmentís extensive animal handling installations will also be utilized.  Dosimetry and local access control will be provided through a local facility control room.



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