Beam position monitors (BPM) are critical for beam-based alignment and operation of the world’s first X-ray free electron laser, Linac Coherent Light Source (LCLS), being built at Stanford Linear Accelerator Center. Fabrication of the BPMs requires welding components made of copper alloy that is extremely difficult to weld due to its low absorptivity to laser light and a high thermal conductivity. This paper presents a laser welding technique for jointing the BPM components made of copper alloy. In this technique, a surface coating and a set of pulsed laser process parameters were developed to enhance the absorption to the laser beam and to produce sound cylindrical butt welds. Results from a welding monitor used to real-time monitor the process for weld quality control are also reported.

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R.
Lill
et al, “
Design and Performance of the LCLS Cavity BPM System
”, SLAC-PUB-13067,
Particle Accelerator Conference (PAC 2007)
,
June 25 – 29
,
2007
,
Albuquerque, NM, USA
.
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W.
Spawr
and
J.
Evanecky
, “Monitoring Laser Weld Quality”,
Industrial Laser Solutions
,
February
,
2004
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