ArcHalfCellMock-up Meeting - VSC MSC Interfaces #1

Friday 16 Sept 2022, 15:00 → 17:00 Europe/Zurich

Notes of Meeting Arc Half Cell Mockup VSC MSC Interfaces #1

16^th September 2022

List of people attending the meeting: 

J. Bauche, L. Baudin, F. Carra, C.Erikson, C.Garion, R. Kersevan, S. Rorison, C. Tetrault, M. Timmins.

1. Status of System Interfaces Design Work (C. Tetrault) 

Slides of the presentations are available in the Indico page related to the Arc Half Cell Mockup meeting #4  (https://indico.cern.ch/event/1196689/)

1)

 

 

Callum presented is work about the interfaces between Magnet and Vacuum systems at various location of the arc cell: Dipole, Quadrupole, Sextupole (preliminary design), Dipole to Dipole interconnection (D2D) and Dipole to Quadrupole interconnection (D2Q)) 

Several areas of interferences have identified between components of the magnet system (yoke or busbars) and the SR absorbers and/or the insolation layer of the vacuum chamber.  

SR absorbers:
0.5 m long, must be installed every 6 m. 

An updated design of the SR absorbers is under investigation for vertical shift of the position of the cooling pipe out of the bending plan. Nevertheless, the space reservation in the horizontal direction can not be reduced as the mechanical connection between the cooling pipes and the absorbers and the weld of the absorbers to the vacuum chamber must be considered.

Consequently, the horizontal distance between the two beams must be increased from 300 mm to 350 mm. 

 

Insolation layer:

Hypothesis for the design f the insolation layer: 
NEG activation at 180 °C, 230/250 °C for bake out of the vacuum chamber 
Maximum temperature of 100 °C at the coils

That leads to a thickness between 10 and 15 mm. It can be reduced locally to 5 mm if the layer is compressed on the top and the bottom of the vacuum chamber.

In experimental chamber that thickness can be reduced to 2/3 mm using aerogel but that is not a solution economically scalable to FCC arcs.

A Kapton isolation layer needs to be added between the insolation layer and the coil.

The vertical distance between the coil is kept at 84 mm

Bake out:

The bakeout has to be done over one vacuum sector at once (500 m long in LEP)
The heat dissipation must be estimated to make sure that it can be handled by the ventilation system.

 

Space allocation for SMA flange Tooling

The size of the flanges used in Callum’s model correspond to flange using Shape Memory Alloy (SMA) technology and has been validated by TE-VSC colleagues. The space allocation needed for tooling during installation and desinstallation can be based on the prototype already realized on circular flanges, related documentation will be transmitted by Sam to Callum.

 

Girder or not Girder for QSS assembly:

One single common vacuum chamber going through the three magnets is the preferred option from the vacuum point of view. Bellows and flanges, which are needed otherwise, have a high cost both economic and machine performance (impedance)!

The welding assembly technic (stir welding) of the flange to the vacuum chamber must be done before NEG coating and can not be performed when the chamber is inserted in the magnets. The vacuum chamber can not the slide inside the magnets!

Consequently, the assembly of the vacuum chamber inside the Quadrupole and Sextupole require to “open” the magnet into two parts, as it is done in light source accelerators (ESRF for instance).

It seems to be challenging from the tolerances required for the assembly. Measurement must be done in the lab after the assembly of magnet. That may require the use of a girder to assemble the magnets and perform the measurement in the lab, before taking the assembled QSS structure in the tunnel.

 

Cost estimate must be done to evaluate two possibilities:

Cost (economic and impedance) of bellows if one chamber per magnet
vs
Cost of using girders to preassemble in the lab one common chamber for the 3 magnets.

 

Magnet / vacuum chamber assembly. Splitable magnets??

 

General:

The space reservation must be preserved for the disassembly of the vacuum chamber on the corridor side or on the wall side. 
Could be an issue in the horizontal configuration with the booster and the collider in the same.
In the vertical configuration, the support of the booster must account the maintenance of the vacuum system (i.e. the 1-m-long chambers!) 

 

Remarks: Hight voltage of the busbar (1 kV), a safety cover will be installed at the dipole-to-dipole interconnection (the vacuum system will be inside)