Mechanical design of the Roman pots

Status report

M.Oriunno

In Collaboration with

L.Favre, G.Laurent and R.Perret EST Division

F. Haug AT Division

Welding on a flat foil and folding

Inconel 718

Inconel 600

SSTEEL 316

What must be done on the pot design:

Production of 5 pot prototypes to test under vacuum the welding technology of the thin window (June 2003)

1. Test on welding technology….Inconel loose ~30% of mech. strength

2. Electrochemical machining without welds.

Pot Prototype for RF Pick up test on electronics

1. Calculations

2. No problems found on other beams (Desy)…check the bunch structure

Pot

Lever Arm

Capacitive sensor

Compensation bellow

Racks

TAN

Collimator

BPMQLR

Cryogenic Cooling (F.Haug, AT/ECR)

Heat loads ~12 watt

(with vacuum ~10-4 torr)

130oK

< 230oK

fews mWatt

2 Watt

Two main options: local cooling (microchanneling) or passive elements

• Micropumps systems have low reliability, problems on manifolds.

• Passive system are preferable: Heatpipes, Peltier Cells

• Cold source at 80oK -> pulse-tube (no vibrations)

• Other systems as J-T are under investigation

Heatpipe ~ 1500mm

Pulse tube

80oK

T ~ 5oK

T ~ 20o K

Constraints from the LHC-Vacuum group :

The compensation of the forces must not be relied on a pick up of the primary vacuum

Since all the vacuum chamber in the LSS are NEG coated, the pot must be designed to stand a baked out up to 300oC

A risk analysis of the operation of the detector operation should be performed

A design pressure of at least 1.5 bar shall be considered in the design of the window

Roman Pots’ Chapter in the TDR

Pot Design : Integration study, Simulation and Prototype test results

Cooling System: Capillaries or Cold finger

Roman Pots Station design: precision, stability, vacuum and accessibility

Integration in the Tunnel: Space allocation, services and radiation environment

We are ready to write an exhaustive chapter !!

What must be done on the pot design:

Production of 5 pot prototypes to test under vacuum the welding technology of the thin window (June 2003)

Pot Prototype for RF Pick up test on electronics

Production of a mock-up of the pot with dummy detectors to have a full integration exercise with the services (June 2003)

Open issues:

Cryogenic Cooling System: Capillary local cooling, Cold fingers. Very unlikely we can spill cryogens from the machine or CMS. LHC/ECR group is working on that.

Electronic RF pickup shielding: are there special constraints on the window ?

Do we have to bake out the pot at 200oC ?

•Yes -> a thin window can not stand the thermal stress

•No -> a locally increased dynamic pressure of residual gases must be accepted

What has been done for the Roman pot system:

Two solutions have been designed:

Symmetric distribution of the loads but less favorable access for maintenance

Not symmetric loads but optimized access

For Both solutions

A compensation system linked to the primary vacuum allows for a fine regulation but an independent vacuum system can be still implemented

A capacitive system accounting the relative position of the top-bottom pots,

Integration of two Roman Pot stations between the TAN and D2