Status of vacuum & interconnections of the CLIC main linac modules C. Garion TE/VSC TBMWG, 9 th November 2009

Outline Vacuum system for the modules  vacuum chambers  pumping system Interconnections  drive beam  main beam Summary & conclusions

Vacuum system of the module Vacuum chambers PETS Accelerating structures Vacuum chambers are mainly PETS or AS Spec: EDMS ,  P MB ~ 10nTorr  Ri MB P 3 mm (now baseline is 4 mm)  material: copper (or Cu coated) Spec: EDMS  Ri DB P 11.5 mm

Vacuum chambers of the drive beam Drift tubeQuadrupole For both cases, precision tubes in stainless steel can be used (  23 *1 in 316L). The length is ~270mm or ~580 mm for long drift tubes. Vacuum chamber will be copper coated. Quadrupole chambers can be centered with 2 “soft” rings (PEHMW). Pipe Pole Ring Tolerances on quad poles are needed to fix the design.

Vacuum chambers of the main beam quad Design:  Stainless steel vacuum chamber, squeezed in the magnet  NEG strips sited in 2 antechambers  Copper coated (thickness to be defined) NEG strip 8-10 mm 50 mm Stainless steel Ceramic support Spacer Tooling has been done for Quad radius of 4 mm  to be redone for final aperture (  10 mm)  Final cross section is needed to check integration of the vacuum chamber in the magnet  Supporting or insulation of NEG strips have to be improved  Spacer have to be improved Probably not needed for module prototypes

Pumping system Vacuum equipment (version sealed disk):  manifolds around the accelerating structures linked to a common tube  Tanks around the PETS linked to a common tube  MB and DB vacuum coupled via the common manifold and the waveguides  pumping system: mobile turbomolecular station + holding ion and cartridge pumps Ion pump 2 NEG cartridges pumps Tank 4 linked Manifolds/AS

Pumping system performances: static vacuum  P 100h ~8.7E-9 mbar (for a link tank/manifold with a radius of 30mm) Assumptions: q~10-10mbar.l/s/cm2 (after 100 hours of pumping) Pumping speed for 1 accelerating structure= 300 l/s 4 manifolds 30 mm*30 mm At that time, a minimum radius of 30 mm has to be reserved for the tank/manifold link Model based on thermal/vacuum analogy 140mm

Assumptions: –10 12 H 2 molecules released during a breakdown –Gas is at room temperature (conservative) Dynamic vacuum in the accelerating structures MC model Thermal model Monte Carlo model and thermal study are in good agreement

Dynamic vacuum in the accelerating structures  Not a “big” difference between 1 or 4 manifolds Depending on the species, the local pressure doesn’t exceed the range mbar after 20 ms.  Only 1 manifold could be needed (to be confirmed) Other issues: other dynamic effects (RF, beams) to be considered

Pumping system Still to be done: -Link between the loads and the tank -Compensation and connections between the tank and the main and drive beams (for the prototypes, maybe a bellows with 2 standard flanges)

Interconnections - Drive beam PETS/BPM QUAD/PETS QUAD/PETS IC (or QUAD/drift tube IC) Free space: 20mm Free space: 30mm

Drive beam – QUAD/PETS intramodule interconnections Vacuum enclosure delimited by a bellows and knife flanges Electrical continuity done by a copper based flexible element Installation position Working position Flange integrated at the PETS extremity (to have same “free” plane as MB for tunnel installation). Is it acceptable?

Drive beam – QUAD/PETS intramodule interconnections Stainless steel flange brazed on the PETS Spring washers Stainless steel bellows: ID:45 mm, OD: 58 mm, 5 convolutions, 0.1mm thick, Pitch: 4 mm Flexible “tube” Copper rings Gasket/flange assembly (with screws) Schematic artistic view of the flexible element Thin foil (0.1mm) in copper based material Is there any requirement for the electrical conductivity?

Drive beam interconnections Design of drive beam interconnections exists. To be confirmed: Space available in the magnet extremities (outer diameter of the bellows) Number of cycles needed for the design of the flexible element To be done: Detailed design of the flexible element (geometry and material) PETS/drift tube connection: permanent or dismountable connection? Optimisation of the flange and knife (not mandatory neither for the module prototypes nor for the CDR) QUAD/PETS intermodule interconnections: same interconnection as QUAD/PETS Intramodule but with longer flexible element and bellows (6 convolutions) PETS/BPM intermodule interconnections: same interconnection as QUAD/PETS intermodule but with different flange on PETS

QUAD/AS AS/BPM IC (or AS/AS IC) AS/AS Free space: 30mm20 mm 15mm Interconnections - Main beam

Main beam – QUAD/AS intra & intermodule interconnections intramodule intermodule Damping material What is the maximum transverse displacement expected (1mm)? Copper tube Stainless steel bellows: ID:25 mm, OD: 36.5 mm, 4 or 9 convolutions, 0.1mm thick, Pitch: 2.7 mm Updated from Riccardo’s inputs

Main beam – AS/AS intermodule interconnections Gap 9 mm Copper tube Damping material Stainless steel bellows: ID:146 mm, OD: 166 mm, 4 convolutions, 0.1mm thick, Pitch: 4 mm Screws?

Main beam – AS/AS intramodule interconnections Copper “flexible” element Requirement for the electrical conductivity? Case 1: only 1 longitudinal fixed point for all AS on the module AS Precision of the longitudinal assembly?

Main beam – AS/AS intramodule interconnections Copper “flexible” element Requirement for the electrical conductivity? Case 2: 1 longitudinal fixed point on each AS on the module AS A bellows is needed

Main beam interconnections Design exists for main beam interconnections. To be confirmed: Space available in the magnet extremities (outer diameter of the bellows) Maximum misalignment to be compensated. Fixed point for the accelerating structures To be done: Interconnection AS/BPM: critical because tight space and transition with the quad vacuum chamber. Optimisation of the flange and knife (not mandatory neither for the module prototypes nor for the CDR)

Optimization has been done Prototypes have been manufactured and are being tested (to be sent to SLAC) Interconnections – inter beam waveguide flanges

Conclusion Concepts for the vacuum system and the interconnections exist. Distributed pumping for main beam quad Common tank equipped with pumps linked to AS, PETS and drift tubes Sealed technology of the vacuum interconnections (with electrical continuity for the drive beam and a gap for the main beam) Few questions are pending. Mainly related to: Interfaces with surrounding elements: Quad, AS, PETS, BPM, … Specifications for the interconnections: stroke and misalignment, fatigue life, electrical conductivity, Main parameters for most of the components have been determined. Detailed design can start after the green light.