mkp-i: impedance considerations

MKP-I: Impedance considerations

C. Zannini, H. Bartosik, G. Rumolo, B. Salvant

M. Barnes, T. Kramer, L. Sermeus

Overview• Simulation model

• Simulation results– Proposed options

• Beam coupling impedance considerations– Transverse impedance– Longitudinal impedance– Shielding

• Beam induced power loss and transverse stability– Beam induced power loss– Transverse stability considerations– Beam coupling impedance with beam out

3D simulation model of the MKP-I

Proposed options

Main Parameters

Option 1 Option 2 Option 3 Option 4

Number of magnet cells

5 5 5 7

Magnet cell length

36 mm 45 mm 45 mm 32 mm

Number of magnets

10 8 10 10

Vertical gap 45 mm 45 mm 56 mm 56 mm

Total magnetic length

1.8 1.8 2.25 2.25

X_beam 50 mm 50 mm 50 mm 50 mm

sd 100 mm 100 mm 100 mm 100 mm

sdxbeam

Beam coupling impedance of the proposed options

Beam coupling impedance of the proposed options

Option 3 and Option4 result the more convenient solutions

SPS transverse impedance budget

Vertical impedance: Comparison between present MKPs and MKP-I system

The new MKP-I system has a slightly larger vertical impedance per meter length

Smaller vertical aperture and shorter magnet length


MKP-I system would significantly increase the vertical impedance of SPS kickers


Case Zyeff kickers [MΩ/m] Zyeff SPS [MΩ/m]

Present model 7.57 18.51

With MKPI option 1 8.25 (≈+9%) 19.19 (≈+4%)

With MKPI option 3 8.09 (≈+7%) 19.03 (≈+3%)

SPS longitudinal impedance Comparison between present MKPs and MKP-I system



SPS longitudinal impedance

MKP-I system would significantly increase the longitudinal impedance of SPS kickers

SPS longitudinal impedanceComparison between present SPS kickers and MKP-I system

MKP-I system would significantly increase the longitudinal impedance of SPS kickers

Shielding: proposed options

Shielding proposed options

“beam screen like” shielding with wires (solution to be developed)Ceramic plate with titanium coating

M. Barnes, T. Kramer, L. Sermeus

For electron cloud mitigation it is strongly recommended that the beam does not see the ceramic (see MKIs in LHC)

G. Iadarola, G. Rumolo

Ceramic plate with titanium coating: preliminary simulations

shielding1 shielding2

Ceramic plate with 30 nm titanium coating Ceramic plate with 10 μm titanium coating

shielding1 shielding2

Ceramic plate with 30 nm titanium coating Ceramic plate with 10 μm titanium coating

Ceramic plate with titanium coating: preliminary simulations

Beam induced power loss

Beam induced heating

The calculations for MKEs have been successfully benchmarked against beam induced heating observations during 2012



Present MKPs could strongly suffer of beam induced heating with high intensity beam




Even worst for MKP-I



The shielding option (ceramic plate with titanium coating is not very efficient to reduce the beam induced power loss)

Transverse stability: Q20HEADTAILsimulation

MKP-I option3 wake model

Transverse stability

HEADTAIL simulations from H. Bartosik

Present wake model reproduces the instability behavior (PhD thesis of H. Bartosik, to be published)

The new MKP-I kicker system would reduce the transverse vertical instability threshold of ≈ 5%

Longitudinal impedance: beam out

Having the circulating beam out of the magnet would dramatically reduce the impedance

xout

Transverse impedance: beam out

xout

Having the circulating beam out of the magnet would dramatically reduce the impedance

Info from Benoit : very preliminary studies for the septum

• Preliminary design provided by Bruno Balhan last week• Coarse approximations had to be made due to the complexity of the device,

and lack of available information:• Laminations replaced by ferrites 4A4• Longitudinal segmentation ignored

Magnetic laminations are partially shielded by steel holders Several significant undamped longitudinal modes from 50 MHz onwards (i.e. fully in the beam spectrum) Very large upstream and downstream aperture (frequencies above 500 MHz will escape in the beam pipe) The impedance of this septum should be fully checked and it is likely that it should be optimized

Summary and conclusions• The unshielded MKP-I would significantly contribute both to

the longitudinal and transverse SPS beam coupling impedance.• A reduction of about 5% of the transverse instability threshold

has been estimated.• The MKP-I with the present design could limit future operation

with 25 ns beams due to the beam induced heating (similarly to the non-serigraphed MKE in 2012).

• Circulating beam out would dramatically reduce both longitudinal and transverse impedance solving both heating and stability issues.

• Preliminary simulations seems to indicate that the shielding option (ceramic plate with titanium coating) is not very efficient to reduce the beam induced heating.

Thank you for your attention

Appendix

SPS longitudinal impedance Comparison between present MKPs and MKP-I system

SPS longitudinal impedance: normalized impedance

Effect of magnet length

For a given cell length and total magnetic length in terms of beam coupling impedance a smaller number of magnets is more convenient

Effect of the beam position

The peak due to the TEM mode increases as the beam get closer to the inner conductor

The broadband peak due to the ferrite decreases as the beam get closer to the inner conductor

[mm]


xbeam

[mm]


The transverse impedance decreases as the beam get closer to the inner conductor

xbeam

Effect of the screen distance

Effect almost negligible for the longitudinal impedance

sd

Effect of the screen distance

Shift to lower frequency and reduction of the broadband peak of the ferrite loaded structure on the vertical dipolar impedance

sd



The calculations for MKEs have been successfully benchmarked against beam induced heating observations during 2012




Even worst for MKP-I



The shielding option (ceramic plate with titanium coating is not very efficient to reduce the beam induced power loss)

mkp-i: impedance considerations

Documents

impedance considerationsc

larger vertical impedance

proposed options option

serigraphy mkp

systemthe new mkp

present mkps

mkpi option

d simulation model