few slides from j. fox’ talk in last november’s larp meeting
Post on 09-Jan-2016
21 Views
Preview:
DESCRIPTION
TRANSCRIPT
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 3Wolfgang Hofle BE/RF
LARP CM15 02.11.2010 4Wolfgang Hofle BE/RF
LARP CM15 02.11.2010 5Wolfgang 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)
Wolfgang Hofle BE/RF LARP CM15 02.11.2010 10
SPS aperture
Wolfgang Hofle BE/RF LARP CM15 02.11.2010 11
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
Wolfgang Hofle BE/RF LARP CM15 02.11.2010 16
Travelling wave cavity in SPS LSS3
Wolfgang Hofle BE/RF LARP CM15 02.11.2010 17
Current location of device used as kicker
Wolfgang Hofle BE/RF LARP CM15 02.11.2010 18
Current location of device used as kicker
Wolfgang Hofle BE/RF LARP CM15 02.11.2010 19
Short straight section at QF’s: flat chamber
Wolfgang Hofle BE/RF LARP CM15 02.11.2010 20
Free space in dispersion suppressor
Wolfgang Hofle BE/RF LARP CM15 02.11.2010 21
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
Wolfgang Hofle BE/RF LARP CM15 02.11.2010 22
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
top related