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Title: Measured Radiation and Background Levels During Transmission of Megawatt Electron Beams Through Millimeter Apertures

We report measurements of photon and neutron radiation levels observed while transmitting a 0.43 MW electron beam through millimeter-sized apertures and during beam-off, but accelerating gradient RF-on, operation. These measurements were conducted at the Free-Electron Laser (FEL) facility of the Jefferson National Accelerator Laboratory (JLab) using a 100 MeV electron beam from an energy-recovery linear accelerator. The beam was directed successively through 6 mm, 4 mm, and 2 mm diameter apertures of length 127 mm in aluminum at a maximum current of 4.3 mA (430 kW beam power). This study was conducted to characterize radiation levels for experiments that need to operate in this environment, such as the proposed DarkLight Experiment. We find that sustained transmission of a 430 kW continuous-wave (CW) beam through a 2 mm aperture is feasible with manageable beam-related backgrounds. We also find that during beam-off, RF-on operation, multipactoring inside the niobium cavities of the accelerator cryomodules is the primary source of ambient radiation when the machine is tuned for 130 MeV operation.
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  1. Arizona State University, Glendale, AZ (United States)
  2. Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
  3. Massachusetts Institute of Technology, Cambridge, MA (United States)
  4. Hampton University, Hampton, VA (United States)
  5. William and Mary College, Williamsburg, VA (United States)
  6. University of New Hampshire, Durham, NH (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
JLAB-FEL--13-1741; DOE/OR/23177-2576; arXiv:1305.7215
TRN: US1300310
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nuclear Instruments & Methods in Physics Research, Section A; Journal Volume: 729
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC) (United States)
Country of Publication:
United States
43 PARTICLE ACCELERATORS background radiation; beam transmission; energy recovery linac; megawatt electron beam; millimeter aperture; multipactoring