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RIS citation export for TUPMP033: Design of the Neutron Imaging Differential Pumping Line at LLNL

AU  - Caggiano, J.A.
AU  - Castronovo, D.
AU  - Fitsos, P.
AU  - Gibson, D.J.
AU  - Hall, J.
AU  - Johnson, M.S.
AU  - Marsh, R.A.
AU  - Rusnak, B.
ED  - Boland, Mark
ED  - Tanaka, Hitoshi
ED  - Button, David
ED  - Dowd, Rohan
ED  - Schaa, Volker RW
ED  - Tan, Eugene
TI  - Design of the Neutron Imaging Differential Pumping Line at LLNL
J2  - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019
CY  - Melbourne, Australia
T2  - International Particle Accelerator Conference
T3  - 10
LA  - english
AB  - The neutron imaging system at LLNL is a radiographic capability for imaging objects with fast, quasi-monoenergetic neutrons at ≤1mm spatial resolution. The neutron production source is a deuteron beam (4 or 7 MeV) incident upon a rotating, high-pressure, windowless, pure-deuterium gas target. The windowless nature of the target combined with the high pressure leads to significant gas leakage upstream of the neutron production target. This leakage degrades the imaging quality by (1) increasing the depth-of-field blurring and (2) increasing the beam diameter and divergence in the transverse direction via angular straggling in the residual gas. To mitigate these effects, and guided by bench tests and simulations, we designed a differential pumping line (DPL) to ensure the highest quality imaging system. The system consists of three primary stages (chambers), each separated by carefully shaped apertures. These apertures can be long and thin with low-angle tapers due to the high quality of the beam optics (convergence at the target < 5mrad) and low emittance of the beam (~5 pi mm-mrad). The primary cascaded roots pumps are sized to remove >99% of the incoming mass flow in each stage, ensuring that by the third stage furthest from the target, turbomolecular pumps are able to operate in a nominal ~mTorr range. We anticipate full system testing with helium in mid 2019.
PB  - JACoW Publishing
CP  - Geneva, Switzerland
SP  - 1312
EP  - 1314
KW  - neutron
KW  - target
KW  - vacuum
KW  - shielding
KW  - simulation
DA  - 2019/06
PY  - 2019
SN  - 978-3-95450-208-0
DO  - DOI: 10.18429/JACoW-IPAC2019-TUPMP033
UR  - http://jacow.org/ipac2019/papers/tupmp033.pdf
ER  -