The Applicability of NEG Coated Undulator Vessels for the CLARA FEL Test Facility

Malyshev, Oleg; Marinov, Kiril; Middleman, Keith; Thompson, Neil; Valizadeh, Reza; Williams, Peter

doi:10.18429/JACoW-IPAC2017-WEPIK100

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RIS citation export for WEPIK100: The Applicability of NEG Coated Undulator Vessels for the CLARA FEL Test Facility

TY - CONF
AU - Malyshev, O.B.
AU - Marinov, K.B.
AU - Middleman, K.J.
AU - Thompson, N.
AU - Valizadeh, R.
AU - Williams, P.H.
ED - Schaa, Volker RW
ED - Arduini, Gianluigi
ED - Pranke, Juliana
ED - Seidel, Mike
ED - Lindroos, Mats
TI - The Applicability of NEG Coated Undulator Vessels for the CLARA FEL Test Facility
J2 - Proc. of IPAC2017, Copenhagen, Denmark, 14â19 May, 2017
C1 - Copenhagen, Denmark
T2 - International Particle Accelerator Conference
T3 - 8
LA - english
AB - CLARA is a FEL test facility at Daresbury Laboratory (DL), UK. The undulator vacuum chamber is 20 m long with inner diameter 6 mm and its vacuum performance can benefit from a NEG coating. The thickness of the coating layer must be carefully optimised. A layer ~ 1 um would help the vacuum but a thinner layer would be partially transparent for the EM field reducing the resistive wall wakefields due to the NEG. A very thin layer, however, may not yield the necessary vacuum performance. Two types of NEG coatings produced at DL - dense and columnar - were considered. Their bulk conductivities were measured in a separate study. The resistive wall wakefield impedance was calculated following the standard approach for multilayer vessels. A 250 fs rms electron bunch was generated in ASTRA and its wakefield was obtained from the vessel impedance. The FEL performance was then studied through GENESIS simulations and the result compared to the case with no wakefields. It was found that NEG layers thicker than 100 nm give an unacceptable reduction of the FEL power and the vacuum performance of such thin coatings is unknown. Possible solutions to this problem are discussed.
PB - JACoW
CP - Geneva, Switzerland
SP - 3181
EP - 3183
KW - vacuum
KW - FEL
KW - wakefield
KW - undulator
KW - impedance
DA - 2017/05
PY - 2017
SN - 978-3-95450-182-3
DO - 10.18429/JACoW-IPAC2017-WEPIK100
UR - http://jacow.org/ipac2017/papers/wepik100.pdf
ER -