Considerations when introducing new
equipment into the LHC
M.Gallilee
CERN, CH-1211, Geneva 23, Switzerland
INTRODUCTION AND GOAL
This is a summary of the approval process required for the implementation of new vacuum chambers and equipment in the LHC. A rigorous approval process is required, with a final approval granted at the LHC
Machine Committee (LMC). Reduction in diameter of the central vacuum chambers will allow for better Physics data and detector accuracy. The requested changes need a full machine study in order to ensure
that they are compatible with both the current LHC and the future HL-LHC and that the most possible flexibility is given for future run conditions.
EXAMPLES OF PAST STUDIES
Pictures courtesy of ATLAS
Pictures courtesy of CMS
CMS reduction of central vacuum
chamber inner diameter from 58 mm to
43.4 mm and ATLAS reduction from
58 mm to 47 mm inner diameter. Figures
1 and 2 show simplified diagrams of the
changes.
7
Figure 1: New CMS Chamber—6.2 m in length, minimum inner diameter 43.4 mm, 0.8 mm wall
Figure 2: New ATLAS Chamber—7.3 m in length, inner diameter 47 mm,
0.8 mm wall
APPROVAL PROCESS
EXAMPLE OF CAVERN MOVEMENTS FOR STABILITY TOLERANCES
The approval process considers all areas where the new object may affect the
performance of the machine.
The experimental caverns have been measured at regular intervals.
Floor Stability
ATLAS Floor Stability Aug 03 – Dec 10 (graphique)
Machine
Protection
A23-7
Background
E-Cloud
A17-14
1.5
1
Aperture
approval
with LMC
Deep References
0.5
A11+5
MOVEMENTS IN MM
Impedance
Heating
Positioning
Tolerances
Stability
Tolerances
A22-15
A17+8
Collimation
A11-5
B0+8
B0+5
B0-5
B0-9
C23+10
C23+5
C23-7
(Sector layout
now defined)
10-Dec
Jun-09
Dec. 08
July 08
0
Febr 08
Aug 07
March 07
Aug 06
March 06
Nov-05
Oct 05
Aug 05
March 05
Oct-04
Sep-04
Dynamic Vacuum
June 04
Aperture for n1
value
March 04
C22-15
Aug 03
Mechanical
Tolerances
A23+5
2
Injection Optics &
Beam Dump
New
Diameter
Beam Pipe
A23+10
FLOOR STABILITY : CUMULATIVE MOVEMENTS AUGUST 03 - DEC 10
C17+8
C17-14
C12-5
-0.5
C12+5
Data courtesy of Dirk Mergelkuhl and Vitali Batusov: CERN
Static Vacuum
7
Data courtesy of Antje Behrens: CERN
EXAMPLE OF VACUUM ANALYSIS
EXAMPLE OF IMPEDANCE CALCULATION
EXAMPLE OF TOLERANCES OLD AND NEW
EXAMPLE OF APERTURE CALCULATION (N1 σ)
More accurate tolerances have lead to an increase in the available physical aperture for the beam.
2011 Design Value Tolerances
ATLAS CENTRAL CHAMBER
CMS CENTRAL CHAMBER
Composition of beampipe radius (mm)
Mechanical Construction and Assembly
1.95
1.15
Installation Survey
2.6 at 2 sigma (95.4%)
1.6 at 2 sigma (95.4%)
Cavern Stability
0.5/year
0.5/year
Stability Margin
0
2.3
Sum of Tolerances
7.05 (for 5 years between alignments) 6.55 (for 3 years between alignments)
Chamber Radius
23.5
21.7
Aperture (Radius-Tolerance Sum)
16.45
15.15
CONCLUSION
In conclusion it has been shown that the approval of a new LHC element is a non-trivial process and many items must be considered before the final go-ahead can be given for installation.
ACKNOWLEDGEMENTS
The author would like to thank the CERN LEB working group for the material which has been used to form the basis of this poster presentation.
Technology Department
28th October – 9th November 2012