Aperture Studies for the Phase 1 Upgrade

1
Aperture Studies for the Phase 1 Upgrade

• a) Comparison of Octagonal and Rectellipse
  screens in MQX
• b) TANC (IR5), TANAL/R (IR1)

2

• Octagonal Rectellipse Beam Screens

3

• The octagonal beam screen dimensions are derived
  using an accredited recipe (EDMS 350449,
  N. Kos).
• Wall thickness (ss) is 1.5mm (S.F J.M).
• The shielding in Q1 is 9mm thick.
• A corresponding rectellipse is derived from the
  octagon.
• Implemented in MADX

4
Collision Optics at 7TeV (30cm)
5
Nominal Half-Crossing 0.5mm, 205 µrad
6
Tilted Crossing _at_ -75o
7
Simple Strategy IR5

• For each screen, tilt the separation bumps at
  angles of -90o to 90o in steps of 15o and
  extract the minimum n1 in each of the insertion
  triplets
• beam 1 and beam2
• ignore spurious dispersion
• IR5 nominally H crossing (f 0o ).
• Verify results using Bernard Jeannerets program.

8

9

10

• Example Halo Plot (rectellipse screen, IR5)

11
Exhaustive Strategy IR1 IR5

• For each screen, tilt the separation bumps in
  both IR1 and IR5 at angles of -90o to 90o in
  steps of 15o and extract the minimum n1 in each
  of the insertion triplets of IR5 for beams 1 and
  2, including the effect of spurious dispersion
• IR1 nominally V crossing (f 90o)
• Grid of 13 x 13 169 points for each screen
• Plot worst case configurations and compare

12

13

14

15

Rectellipse
Octagon
16

• TANC (IR5)

17
TANC

• Circular aperture, 52mm ID
• Geometry optimised for current LHC layout,
  especially w.r.t D1 D2
• Strategy is exhaustive, as above
• Screen in MQX not relevant
• Set parallel separation bump polarity to -1, 0,
  1
• Grid of 13 x 13 169 points for each polarity
• Plot worst case configurations and compare

18

7.5s
5.5s

19

20
Conclusion

• Optimised octagonal beam screen gives greater
  flexibility to the separation scheme for
  negligible loss of aperture compared to the
  rectellipse.
• Operational aperture margin will be gained by
  correction spurious dispersion.
• Preliminary results suggest changing the TAN

21
T.B.D

• Complete the study for the TANC, TANAL/R (all
  polarities separations).
• Declare final conclusions.