BI/TB on ELENA and Wire-scanner Impedance

866 2-D05 (CERN)

866 2-D05


Notes combined from Rhodri and L. Jensen

1) New Fast WS - Impedance Results

  • Can we install the mechanism in the SPS (no effect on beam?)
  • Will the wire survive in the parking position & when scanning?


  • Wakefield solver cannot model small details (only ACE3P but poor on materials)
  • Many unknowns concerning device
  • Large error bars & low confidence in simulations

Conclusions from measurements

  • Detected possibly harmful modes at 250 and 330 MHz with Q~100/150.
  • Detected considerable number of modes induced by the wire-fork system.
  • Ferrite and tungsten wire give little improvement.
  • Ferrite position: can be optimized with the help of CST simulations.
  • All-mode-coupler: probably bad location/coupling, to be optimized.
  • All-mode-coupler: could we put it in the space the fork does not go?
  • Closing the gap helps in reducing the beam modes, not the wire ones. A sheet with a slot where the fork can pass might be helpful (design already proposed in the past)
  • Not clear understand of the location of the wire modes, probably close to the fork.
  • Other ideas?


  • With the information we have, there is no showstopper for installation of the new prototype tank in the SPS for the 2015 run (conclusion from impedance meeting on Monday).
  • Agreement between simulations and measurements is not yet satisfactory to be confident on the wire heating. Many modes in both measurements and simulations. We can therefore not guarantee that the wire will survive in parking position, and more studies (in particular with beam) are needed.


  • Instrument the wire -  VNA?
  • Can the wire be directly connected to forks?
  • Can we put a coax instead of simple wire?

2) ELENA BI Update

  • GEM & BTV
    • Re-use of 2 GEM & relocation of one BTV
    • New BTV to measure beam at injection
      • Magnetically coupled push-pull validated
      • Integration & design complete
      • Construction early 2015 for installation end 2015
  • BPM
    • 20 circular "shoebox" with vacuum dielectric
    • Mounted in quads
    • Proto built & tested - electrode capacitance as foreseen (good for Schottky)
      • Manufacturing to start early 2015
    • E-cooler BPM
      • Simplified - with long cables
      • Is linearity a problem for large e-beam?
    • Electronics
      • Analogue OK - Brescia
      • Digital to be tested in AD by end 2014
    • Software
      • Specifications and planning to be discussed (PI/SW)
  • Tune
    • Stripline as kicker & PU
    • Electronics prototyped in AD
  • Scraper for beam profile measurements
    • Blade position as a function of time
      • Scraper and electronics/software provided by EN-STI
    • Circulating beam intensity vs. time, or secondary particles on a scintillator vs. time.
      • Currently not fast enough intensity measurement
      • Scintillator OK for antiprotons - what about H-?
      • Can a slowish wire-scanner be used instead?
    • Combine the two measurements to reconstruct the beam amplitude distribution.
    • Possible to reconstruct transverse profiles for non-zero dispersion using scraper?
  • H-, Proton (+ve & -ve magnet polarity)
    • Check possible issues with intensity & polarity for instrumentation
  • Main missing component for baseline
    • Scraper signal for H- & protons where scintillator signal is too small (annihilation for antiprotons gives large signal)
  • IPM
    • Look at possibility of gas curtain to reduce pressure?
  • In kind contribution for extraction lines
    • Micro-wire chambers from Japan need BI help for integration
There are minutes attached to this event. Show them.
    • 9:30 AM 10:00 AM
      Wire-scanner impedance measurements 30m
      The presentation will cover the following points: 1) Measurement techniques 2) Main issues seen during the different iterations 3) Wire heating reduction methods 4) Proposals for new solution allowing for SPS installation during next XMAS stop 5) Further simulations and measurements
      Speaker: Benoit Salvant (CERN)
    • 10:00 AM 10:30 AM
      Discussion 30m
    • 10:30 AM 11:00 AM
      Status and plans for ELENA instrumentation 30m
      Speaker: Dr Gerard Tranquille (CERN)
    • 11:00 AM 11:30 AM
      Discussion 30m