Radiation Measurements in a Labyrinth Penetration at a High-energy Proton Accelerator

Abstract

The efficient design of access penetrations at high-energy proton accelerators is desirable for both economic and personnel protection reasons. This paper reports on a series of measurements made in a personnel access labyrinth which viewed an A1 target bombarded by 400-GeV protons from the Fermilab Tevatron. Measurements of absorbed dose in the labyrinth using tissue-equivalent ion chambers were consistent with theoretical predictions of both the relative attenuation through the penetration and the absolute magnitude near the target. The multisphere technique was used to determine the neutron energy spectrum in one section of the labyrinth. A recombination chamber was used to measure the quality factor of the radiation field in two sections of the labyrinth. Good agreement with the quality factor deduced from the multisphere result was obtained at the same measurement location.

Investigation of Radiation Streaming and Maze Design for the Taiwan Photon Source

“…Farther into the labyrinth, thermal neutrons become gradually important and contribute a considerable amount to the total dose (up to 36% at the maze exit) despite their low fluence-to-dose conversion factors. Near the end of the second leg, about 70% of the total neutron fluence is within the thermal energy range that is consistent with the measurement using a multisphere technique by Cossairt et al (1985). Outside the lateral shielding wall without the maze, the contributions of the total neutron fluence from these three energy bands are roughly comparable to each other (35%, 41%, and 24%) and those high-energy neutrons contribute almost half the total neutron dose (46%) outside the bulk shielding.…”

“…For high-energy accelerators, several recipes and formulae to evaluate the radiation streaming and attenuation in labyrinths are available in literature (Goebel et al 1975;Tesch 1982;Cossairt et al 1985;Cossairt 1995). Thomas and Stevenson (1988) and Cossairt (2005) have reviewed and documented this subject in extensive detail.…”

Radiation physics for personnel and environmental protoection

“…One can see that, proceeding from the target outward in the passageway, beyond the abrupt jump that arises as the corner hides the target from view, the fast neutron components are attenuated more readily than is the thermal one. This phenomena associated with "turning the corner" was also verified by Cossairt et al (Co85b). Second and successive legs of such straight penetrations thus change the situation dramatically, principally by modifying the spectrum of the transmitted neutrons.…”

Neutron Dose Per Fluence and Weighting Factors for Use at High Energy Accelerators

“…The neutrons were produced by 400 GeV protons striking an aluminum target inside of a large pipe beneath the floor of the main enclosure (Cossairt et al 1985).…”