Polyimide films
The superconducting cables of LHC magnets are insulated by three layers of polyimide film which are to be supplied in the form of tapes. The first two layers are made of plain polyimide film and the third layer is made of an all-polyimide film adhesive film. The insulation to ground is composed of plain polyimide film in sheet form and are of a type suitable for forming without formation of cracks. The detailed technical requirements of these films are specified in the technical specifications IT - 2679. The overview of film types for the main superconducting magnets of LHC , nominal thickness, dimensions and approximate mass is given in the table below :
|
Type of film
|
Denomination
|
Thickness ( micr )
|
Width (mm) |
Mass (t)
|
|
Plain Tape
|
P1
|
50.8 ± 3%
|
11 ± 0.1
|
39
|
|
P2
|
38.1 ± 5%
|
11.0 ± 0.1
|
1.5
|
|
|
P3
|
25.4 ± 5%
|
8.0 ± 0.1
|
0.5
|
|
|
Adhesive Tape
|
A1
|
68.6 ± 3 %
|
9.0 ± 0.1
|
20
|
|
A2
|
55.9 ± 5 %
|
9.0 ± 0.1
|
2
|
|
|
Ground Insulation
|
Sheet
|
125 % ± 3 %
|
250 ± 1
|
16
|
In addition to the test foreseen by the film manufacturer to meet the specified requirements and writing up the certificates of conformity, CERN will carry out a number of additional acceptance test which are described in the project note XXX
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