Update on TCTP heating
H. Day, B. Salvant
Acknowledgments: L. Gentini and the EN-MME team
Context
• Presentation at the collimation working group in March 2012
• Long-standing action for the impedance team, needed to wait
for:
– the eigenmode solver with dispersive material
– Indication that the simulations are relevant (very important for a
complicated geometry such as the TCTP)
PhD thesis of Hugo Day (2013)
Ferrite considered was 8C11 at the time
Simulations of longitudinal impedance
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Very heavy simplifications from the initial CATIA file from Luca Gentini
In particular, RF fingers at entry and exit needed to be replaced by a sheet, and
was anyway badly meshed.
Angle of the RF fingers adapted to the jaw position in order to keep contact,
however can be different for the real collimator
1.7 M mesh cells
All materials perfect conductors, except the ferrite, in order to get rid of the
resistive wall losses from the jaw
Of course, there is uncertainty on
ferrite parameters
Half gap scanned between 1mm and 10 mm
Additional assumptions
• Impedance which will heat the ferrite should be broadband
• Need to suppress the losses from the resistive wall  use
perfect conductor everywhere except for ferrite and assume
that superposition is possible.
Simulations of longitudinal impedance
Longitudinal Impedance in Ohm
Half gap= 10mm
Frequency in GHz
 Opening the gap leads to an increase
of the amplitude of broad modes
 More heating to ferrrite with gap open
 Of course, this is not true for resistive wall
heating to the jaws
Longitudinal Impedance in Ohm
Half gap= 1mm
10 mm
1 mm
Frequency in GHz
Power contribution in W
Superposition of beam spectrum with
impedance (50 ns beam)
Frequency in Hz
 Main contribution from the broad peaks around 500 MHz, peaks beyond 1 GHz
only significant for the Gaussian distribution
Power contribution in W
Superposition of beam spectrum with
impedance (25 ns beam)
Frequency in Hz
Power loss
(post-LS1, 25 ns, bunch length = 7.5 cm)
 50% to 100% of this heat load goes to the two lines of ferrite
Power loss
(post-LS1, 25 ns, bunch length = 9 cm)
 50% to 100% of this heat load goes to the two lines of ferrite
Power loss vs gap (post-LS1, 50 ns)
 50% to 100% of this heat load goes to the two lines of ferrite
Power loss vs gap (HL-LHC, 50 ns)
 50% to 100% of this heat load goes to the two lines of ferrite
Power loss vs gap (HL-LHC, 25 ns)
 50% to 100% of this heat load goes to the two lines of ferrite
Summary
• Heat load to the ferrite can reach of the order
of 5 W per side
• Opening the gap increases the heat load
• After LS1, with standard bunch length of 9 cm,
we expect on the order of 1 W in the ferrite
per side