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Title: Shielding NSLS-II light source: Importance of geometry for calculating radiation levels from beam losses

We present that third generation high brightness light sources are designed to have low emittance and high current beams, which contribute to higher beam loss rates that will be compensated by Top-Off injection. Shielding for these higher loss rates will be critical to protect the projected higher occupancy factors for the users. Top-Off injection requires a full energy injector, which will demand greater consideration of the potential abnormal beam miss-steering and localized losses that could occur. The high energy electron injection beam produces significantly higher neutron component dose to the experimental floor than a lower energy beam injection and ramped operations. Minimizing this dose will require adequate knowledge of where the miss-steered beam can occur and sufficient EM shielding close to the loss point, in order to attenuate the energy of the particles in the EM shower below the neutron production threshold (<10 MeV), which will spread the incident energy on the bulk shield walls and thereby the dose penetrating the shield walls. Designing supplemental shielding near the loss point using the analytic shielding model is shown to be inadequate because of its lack of geometry specification for the EM shower process. To predict the dose rates outside the tunnelmore » requires detailed description of the geometry and materials that the beam losses will encounter inside the tunnel. Modern radiation shielding Monte-Carlo codes, like FLUKA, can handle this geometric description of the radiation transport process in sufficient detail, allowing accurate predictions of the dose rates expected and the ability to show weaknesses in the design before a high radiation incident occurs. The effort required to adequately define the accelerator geometry for these codes has been greatly reduced with the implementation of the graphical interface of FLAIR to FLUKA. In conclusion, this made the effective shielding process for NSLS-II quite accurate and reliable. The principles used to provide supplemental shielding to the NSLS-II accelerators and the lessons learned from this process are presented.« less
Authors:
 [1] ;  [2] ;  [2] ;  [2]
  1. Operations and Accelerator Design Consulting, Ridge, NY (United States)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). NSLS-II
Publication Date:
Report Number(s):
BNL-111851-2016-JA; BNL-111852-2016-JA
Journal ID: ISSN 0168-9002
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
Additional Journal Information:
Journal Volume: 835; Journal ID: ISSN 0168-9002
Publisher:
Elsevier
Research Org:
Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; top off injection; FLUKA; FLAIR; NSLS-II; National Synchrotron Light Source II; Radiation Shielding; Beam losses; Radiation Dose Estimation; top-off injection
OSTI Identifier:
1340338
Alternate Identifier(s):
OSTI ID: 1340337