Monte Carlo Studies for the Radiation Shielding Design of LCLS-II Page: 1 of 4
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Monte Carlo Studies for the Radiation Shielding Design of LCLS-II
Shanjie Xiao*, Stan X. Mao, Ludovic Nicolas, Sayed H. Rokni, Mario Santana Leitner
SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California, 94025, USA
Intensive Monte Carlo simulations performed with state-of-the-art computation codes are applied to the
radiation shielding design of LCLS-II, which will be the extension of Linac Coherent Light Source
(LCLS) at SLAC and will use the middle one-third of SLAC two-mile Linac. This paper describes the
Monte Carlo studies of the first and last system where electron beams are involved, namely the LCLS-II
Injector and the X-ray Transport and Diagnostics System (XTOD).
Keywords: Monte Carlo; radiation shielding; free electron laser; LCLS; FLUKA
LCLS-II will be the extension of Linac Coherent
Light Source (LCLS), which is the first hard X-ray free
electron laser facility, and will use the middle one-third
of SLAC two-mile Linac. Figure 1 shows the overall
scheme of the radiation safety system of LCLS-II .
This paper describes Monte Carlo studies of the first
and last systems where electron beams are involved,
namely the LCLS-II Injector and the X-ray Transport
and Diagnostics System (XTOD).
LCLS-I electron beam line
LCLS-Il hrd X-ray line
LCLS-II soft X-ry line
BSYD2 BTHWest HH BTH T
, -aE -a -- - D
D2b TD IK2 c TDK K- -
STC Gib HH ao r s s
sisal PPSsrcppers maw masze +
Vert aeon snag egress ntars S\DS U PIP; FEE2D2
--_~fler s sDms dms EH2
-- E EH aI
Undulator Hall2 -DumpHall2
Figure 1. Overall scheme of LCLS-JJ radiation safety system
2. Monte Carlo Studies for LCLS-II Radiation
2.1. LCLS-II injector
2.1.1 Sector-10 injector wall
The injector will be the first construction of LCLS-II.
It will be built in the Sector-10 vault, contemporarily to
the operation of FACET (Facility for Advanced
Accelerator Experimental Tests) at the Sector-10 in the
*Corresponding author. Email: firstname.lastname@example.org
Linac. Therefore, a shielding wall separating the S 10
vault and Linac area has been designed, with the help of
comprehensive FLUKA [2, 3] simulations, to protect
personnel in LCLS-I injector construction. FACET
has a chicane with two legs to compress electron and
position bunches beside the injector vault. The wall
design is based on the FACET beam loss scenarios and
the corresponding dose limitations listed in Table 1. The
dose limitation corresponds to normal 10 W losses when
chicane is "ON" is the most restricted one and thus
defines the wall design. This paper focuses on radiation
doses under normal loss scenarios.
Table 1. FACET beam loss scenarios and shield criteria.
Scenario Beam Loss Dose Limitation
Chicane 10 GeV, 10 W 10 mSv/year
ON (5 W on each leg) (5 Sv/h for 2000
Normal Chicane 10 GeV, 5 W on hours)
OFF straight line 0.5 pSv/h/W
Mis-steering 10 GeV, 10 W 4 mSv/h
Maximum credible 14 GeV, 62 kW 0.25 Sv/h
beam 4 ptSv/h/W
Figure 2 shows the top view of the shielding wall
with FACET chicane magnets and a 3D representation
of the wall. The wall consists of poured concrete and
steel embedded in concrete to fit into the limited space
defined by the injector design. Since beam losses may
happen at any location along the chicane, seven (7)
representative loss points were selected for simulations.
Figure 3 shows the radiation dose (using FLAIR ) at
beam height behind the designed S10 wall when 10 W
beam is lost on the straight section between chicane
magnets, where beam losses can deliver the largest dose
to the injector vault. Note that the dose is in the linear
scale of 1-10 pSv/h and the dimension is in the unit of
Work supported in part by US Department of Energy contract DE-AC02-76SF00515.
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Xiao, Shanjie; Mao, Stan X.; Nicolas, Ludovic; Rokni, Sayed H.; Leitner, Mario Santana & /SLAC. Monte Carlo Studies for the Radiation Shielding Design of LCLS-II, report, January 16, 2013; United States. (digital.library.unt.edu/ark:/67531/metadc844906/m1/1/: accessed February 15, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.