Low frequency noise and resonant excitation MD - PowerPoint Presentation

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Low frequency noiseand resonant excitation MD

M. Fitterer

, S.

Papadopoulou

, Y.  

Papaphilippou

, G.

Papotti

, D. Pellegrini, S.

Redaelli

,

G.

Stancari

, G

. Valentino,

A.

Valishev

, D

.

Valuch

, J. Wagner, C. Xu

Acknowledgements:

E.

Bravin

, R. Bruce,

W.

Hofle

, G

.

Trad

, R. De Maria, R. Tomas, S.

Fartoukh

Timeline

finding collisions at injection for low frequency noise MD

resonant excitation MD (fill 5242+5243)

low frequency noise MD

Resonant excitation MD

simulations showed that largest effect is expected for pulsing every 7

th

and 10

th

turn, small effect for every 3

rd turn and no effect for every 8th turn. No effect was seen for a kick amplitude in H and V of 12 nrad, losses were observed for 120nrad kick amplitude in H and Vas ADT H and V kick are not synchronized, excitation was only applied in one plane.

Resonant excitation MDduring fill 5242 we wanted to get a scaling of losses and emittance growth for pulsing every 7

th

turn and try different pulsing patterns.

Explicity

we tried:

7

th turn H (7Qx resonance) -> losses + emittance growth8th turn H -> no effect3rd turn H and V -> small effect10th turn V to get a feeling for the kick amplitudeduring fill 5243 we wanted to get the scaling with amplitude for 10th turn pulsing, V:scaling of losses with excitation amplitudeemittance growth in vertical plane

Resonant excitation MDFilling scheme

Resonant excitation MDfill 5242, 7th turn pulsing H

clear scaling of losses with amplitude

no emittance growth

Resonant excitation MDfill 5243, 10th

turn pulsing V

losses scale with amplitude

emittance growth in V

Resonant excitation MDConclusion:

losses observed for pulsing every 7

th

H and 10

th

turn V as predicted by simulations + small emittance growth in V for pulsing every 10

th turn Vno losses for pulsing every 8th H and 3rd H and V, no effect on emittancesensitivity to pulsing patterns predicted correctly by simulationsbema more sensitive than predicted in simulations

Low frequency noise MDweak-strong scenario + octupoles for long-range bb simulation (chorma=+7,IMOF=+6A)

only

beam 1 excited, beam2 with transverse

damper

excitation with 2urad

, f(hor.)=11.245Hz, f(vert.)=

20.49Hzfill 5243 with two injections:injection 1: switch excitation on/off onceinjection 2: switch excitation on/off twice

Low frequency noise MDFilling scheme

strong bunch, transverse damper on

weak bunch

hor

.+vert. excitation

without damper

hor

.+vert. excitation

with damper

with

beam-beam

+

without

beam-beam

witness bunch

without damper

hor

.+vert excitation

without damper

hor. excitation

without damper

vert. excitation

without damper

Low frequency noise MDrelative losses from BSRT b1 (= beam with excitation)

Low frequency noise MDrelative losses from BSRT b2 (= strong beam, no excitation, damper)

-> coupling between both beams even with damper and orbit feedback

Low frequency noise MDemittance change due to filamentation

Resonant excitation MDConclusion: similar results for both injections

:

increase of losses, possibly due to orbit movement at collimators (it is not distinguishable if the increased losses are due to an increased diffusion rate or simply due to the closed orbit distortion or a combination of both)

jump in emittance when switching the

excitation

on/off due to

filamentation (note that the closed orbit distortion is large for a 2urad kick from the ADT)change in slope of emittance observed in 2015 could not be reproducedMD 2015