LCLS-II cryomodule alignment
2Wednesday meeting, 6/17/2015
LCLS-II cryomodule alignment
Topics
• Alignment of Components inside the CM
• Tunnel Network
• Tolerances
LCLS-II cryomodule alignment workshop
Friday May 22nd at FNAL
https://indico.fnal.gov/conferenceDisplay.py?confId=9994
3Wednesday meeting, 6/17/2015
Mechanical design – images from the CAD model (from Yuriy Orlov)
• 38” vacuum vessel with 8” vacuum releave valve.
• 2- cryomodule adjustment
supports
• Sliding interconnection Bellow.
• 8- coupler ports with power couplers and vacuum manifold.
• Instrumentation ports & magnet CL Flange.
4Wednesday meeting, 6/17/2015
Mechanical design – images from the CAD model (from Yuriy Orlov)
• Cryomodule length: ~12.3m
• 3 supports for cold mass (1-fix. and 2-sld.)
• 300 mm –ID, 12m long tube, as backbone for cavity string,
piping system and thermal shielding.
• 8- 9-cell dressed elliptical SRF cavities(with mag. Shielding) +
1-BPM +1- SC splitable quadrupole + 2 Gate valves. (one of the each
end of Cavity string)
• Piping system of Cryomodule.
• 50K aluminum shielding with 30 layers of MLI insulation around cold mass.
5Wednesday meeting, 6/17/2015
BPM & QUAD
6Wednesday meeting, 6/17/2015
Cavity alignment (from Virgil Bocean)
The RF group will provide the mechanical to electrical center offsets for
each cavity with respect to the cavity end flanges
Offsets of 300µm between electrical and mechanical centers have been
found.
Tolerance of individual
cell?
7Wednesday meeting, 6/17/2015
String Alignment
Alignment in warm conditions
Different offsets between
Cavities (x=0.24mm; y=1.97mm) and
Quad (x= 0.00mm; y=1.97mm)
Tolerance: 150µm, wavelength 13m
8Wednesday meeting, 6/17/2015
Cold vs. Warm repeatability
9Wednesday meeting, 6/17/2015
String Alignment: Cold vs. warm
Z position changes of up to 17mm depending on distance to main
support. Offsets are based on DESY numbers.
Tolerance: +/-0.175mm RMS, 3m pattern (the support posts seem to be
stable)
10Wednesday meeting, 6/17/2015
Cold mass vs. vacuum vessel
Support posts are removed during installation,
repeatability needs to be determined
No possibility to check movements after
insertion into vacuum Vessel.
11Wednesday meeting, 6/17/2015
Cold mass vs. vacuum vessel
Fiducial on gate valve
and support posts will
be transferred to
vacuum vessel
fiducials
Tolerance: <100µm
(picture curtesy Tom Peterson)
12Wednesday meeting, 6/17/2015
QC at SLAC after transport
Same measurements as cold mass vs. vacuum vessel, gate valve
fiducials and support posts relative to vacuum vessel fiducials.
DESY reported up to 300µm discrepancies.
Acceptance tolerances have to be specified.
Tolerance: 0.3mm RMS, 3m pattern (I assume that the support posts
don’t move)
13Wednesday meeting, 6/17/2015
Tunnel Alignment
Local alignment of CM: 0.05mm RMS, every 15m
Alignment network: 0.3mm RMS at 100m distance.
Tunnel is narrow -> refraction will affect measurements.
Position [m]
Co
ord
ina
te
cha
ng
e [
µm
]
14Wednesday meeting, 6/17/2015
Summary of Alignment Tolerances
Different aspects of error budget stack up:
Relative alignment of cavities to string: +/-0.075mm RMS; every 1.3m
Cold/warm uncertainty: +/-0.175mm RMS, 3m pattern (the support
posts seem to be stable)
Transport shifts: 0.3mm RMS, 3m pattern (I assume that the support
posts don’t move)
Single cavity to cavity assembly: 0.3mm RMS?, every ~0.15m
Alignment of components in the tunnel: 0.05mm RMS, every 13m
Alignment network: 0.3mm RMS, ~100m wavelength