Few slides from J. Fox’ talk in last November’s LARP meeting LARP CM15 02.11.2010.

LARP CM15 02.11.2010

Few slides from J. Fox’ talk in last November’s LARP meeting

LARP CM15 02.11.2010 2Wolfgang Hofle BE/RF

LARP CM15 02.11.2010 6

Constraints for design of new pick-ups and kickers for the wide band ecloud feedback

current tapered stripline pick-up has limitation in frequency dueto TE11 cut-off around 1.6 GHz goal: extend bandwidth with future new pick-up

W. Hofle, CERN

Wolfgang Hofle BE/RF

Example of “TMC” instability

milder losses (10 to 20 % of the bunch is lost before the first BCT measurement point) losses also correlated to max of vertical signal oscillation profile is rather similar before losses oscillations are quickly decaying after the intensity decrease

B. Salvant et al.

signals from pick-up not corrected for transfer functions

LARP CM15 02.11.2010 8

Motivation for new pick-up

extend transverse diagnostics to beyond 1.6 GHz

non-linear phase response of existing wide band pick-ups (BPWs) not optimal for feedback with time domain sampling

Wolfgang Hofle BE/RF

TMCI: extends beyond 1.6 GHz ecloud: spurious signals at 1.6 GHz

Wolfgang Hofle BE/RF LARP CM15 02.11.2010 9

LBeam

t = 2 L/c

t

^

|ZT (w)|

w

…

ZT

Frequency Domain

ZT (w) = ZT j sin( /2wt ) e -jwt/2^

f=1/(2t)

load or short

gating on 1st pulse

Proposed long strip line as new pick-up

sampling only the first pulse results in flat frequency responsemaximum bunch length 5 ns L > 0.75 m for separation of pulsesseveral striplines can be arranged in vacuum chamber (circumference)


SPS aperture


Pick-up close to QDinstalling pick-up at QD with circular aperturehigh vertical beta function (~100 m)frequency reach: 83 mm diameter: cut-off: 2.1 GHzcan make aperture smaller than current BPW pick-ups

Pick-up close to bendsMBB: flat more rectangular chamber:cut-off frequency of relevant TE mode (132 mm width): 1.2 GHznot good for pick-up, but possibly for kicker if bandwidth < 1 GHz

Scenario under discussion:- new pick-up as CERN project, use high power feed throughs in order to also be able to use it as a kicker for prototype tests- design study / construction of a kicker as a joint LARP/CERN effortpick-up for installation in shutdown 2012-2013 ready for feed back demonstrator in 2013

Included in LIU project proposal at CERN

RF, low radiation

special instrumentationno RF infrastructure

extraction CNGS/LHCinjection

slow extractionradiation highcurrent transverse FB

extraction LHC

current layout SPS LSS3

space available for transverse feedbacks

3

4

2

2 3

4

800 MHz

800 MHz

future layout (option 1) SPS LSS3

QDPU BPW

PU BPW

PU BPW

PU BPW

space available for transverse feedbacks

QD


Travelling wave cavity in SPS LSS3


Current location of device used as kicker


Short straight section at QF’s: flat chamber


Free space in dispersion suppressor


Issues: Layout in SPS LSS3

Option 1: 200 MHz TWC: 2x2, 2x3, 2x4space for pick-ups close to QD’s preserved

study needed if all pick-ups & kickers for the future systemcan be put into dispersion suppressor; combine with study formovement of current damper from LSS2 to LSS3 and TWC upgrade

location fixes aperture !

Option 2: TWC’s have more sections, no space left for pick-ups

Current: 200 MHz TWC: 2x4, 2x5space in LSS3 (straight section) used for pick-upsspace in dispersion suppressor for kickers


Study items for new pick-up and kicker

kick strength / bandwidth must come from simulationsaperture, where are we going to install itequipment we want to put in the tunnel for final systemis physical centering of the beam in the pick-up required ?is “electronic” centering possible ?

kicker: what are we going to use, set of short strip lines ?

LARP CM15 02.11.2010

Few slides from J. Fox’ talk in last November’s LARP meeting LARP CM15 02.11.2010.

Documents

Transcript of Few slides from J. Fox’ talk in last November’s LARP meeting LARP CM15 02.11.2010.