The object of XFEL commissioning is to turn the efforts of about 50 work packages into a smoothly operating source of quality FEL beams delivered to multiple users. This task will be performed by a Commissioning Team consisting of experts in accelerator physics, photon systems, technical systems, and controls. The Commissioning Team is led by a small Coordinating Group whose expertise covers both the electron and photon systems. The size and composition of the Commissioning Team will vary in time as the different parts of the XFEL are sequentially commissioned. Operators working alongside the commissioning team to implement learn and help to define, the procedures that will be used during routine operation.
The overall strategy has two phases. First, separate beam line sections are sequentially commissioned using an initial set of performance goals (mainly: <100 bunches, 0.5 nC charge). Once beam line commissioning is complete and FEL beams can be delivered to experiments, a development period ensures in which part of the time is devoted to commissioning and part to delivering beam. During this phase the performance parameters are gradually brought up to their full design values.
Commissioning of each beam line section begins with "pre-beam checkout". This includes end-to-end checking of each control point, from the control room software to the item in the tunnel. After pre-beam checkout is complete and beam can be delivered, commissioning will entail three 8-hour shifts per day, seven days a week. It will involve turning on multiple system simultaneously and using the beam to debug, calibrate, and optimize the system parameters. It also will involve developing procedures and software for tuning up and changing beam parameters.
The first beam line section to be commissioned will be the Injector up to the injector dump I1D. Commissioning starts with the cool-down of the Injector cryo-modules (time TI). The laser beam line commissioning and the conditioning of the RF gun will have been performed beforehand. The injector should be commissioned up to the complete set of design values and a period of 12 month is foreseen. At TI+4month beam injection into the downstream beam line sections should be possible.
Closing of the tunnel and the start of the cool-down (time T0) marks the beginning of the linac commissioning up to the linac dump (TLD). This involves - among other things – the commissioning of the low-level rf system. Earliest at T0+3 month the beam can be sent to the linac dump and sub-sequentially through the SASE1 and SASE3 undulators and generate x-rays. After electron beam-based alignment, undulator gap and strength calibrations and commissioning of photon beam line diagnostics, first lasing should be observable at SASE1 at T0+6 month. Over the next two years, using the allocated time for machine development, the performance of the XFEL will be gradually increase to reach the full design goals.
Commissioning
Home Page
Last update Feb 11, 2013
Contact winfried.decking@desy.de