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