Rf considerations for fhc
This presentation is the property of its rightful owner.
Sponsored Links
1 / 10

RF considerations for FHC PowerPoint PPT Presentation


  • 107 Views
  • Uploaded on
  • Presentation posted in: General

RF considerations for FHC. E. Shaposhnikova 23.01.2014. Questions. Input data Bunch spacing(s) Bunch length during physics Bunch intensity Output data Optimum RF frequency Minimum RF voltage Longitudinal emittance Double RF system?. I nput data (Table 1). Ring parameters:

Download Presentation

RF considerations for FHC

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Rf considerations for fhc

RF considerations for FHC

E. Shaposhnikova

23.01.2014


Questions

Questions

  • Input data

    • Bunch spacing(s)

    • Bunch length during physics

    • Bunch intensity

  • Output data

    • Optimum RF frequency

    • Minimum RF voltage

    • Longitudinal emittance

    • Double RF system?


I nput data table 1

Input data (Table 1)

  • Ringparameters:

    • Circumference: ~99.7 km

    • Energy loss per turn @50 TeV: U0=4.6 MeV

    • Transition energy: γt=120 (Frank Z.)

  • Beam parameters:

    • Bunch spacing(s): 5 ns, 25 ns

    • Bunch length during physics: 8 cm

    • Bunch intensity: 1.x1011


Criteria used

Criteria used

  • Filling of the RF bucket

    • maximum momentum filling factor of 0.8 (losses)

    • minimum filling factor is also important for stability

      • threshold ImZ/n ~ (filling factor)5/2 (for φs = π)

  • Single bunch longitudinal stability

    • Threshold for the loss of Landau damping

    • Longitudinal impedance budget (inductive part ImZ/n)

      => assumed to be similar to the LHC ImZ/n = 0.1 Ohm (calculated and measured).

      Factor 2 is taken as a margin (formfactor for particle distribution,…)


Rf frequency

RF frequency

  • 5 ns spacing => n x 200 MHz => 200, 400, 800,… MHz with bucket length = 5, 2.5, 1.25 ns

  • Bucket length in the presence of synchrotron radiation is reduced by Δφ ~ 2(πU0/V)1/2

  • Bunch length of 8 cm => τ4σ = 1.07 ns (Table 1)

    => 200 MHz or 400 MHz


400 mhz rf

400 MHz RF

Loss of Landau damping

Filling factor in momentum


400 mhz or 200 mhz

400 MHz or 200 MHz?

Longitudinal emittance

400 MHz RF

Bunch length and stability

200 MHz RF


2 00 mhz rf

200 MHz RF

Loss of Landau damping

Filling factor in momentum


Additional considerations ring size and harmonic number

Additional considerations:ring size and harmonic number

  • 400.79 MHz and bunch spacings of 5 ns, 25 ns

    hLHC = 35640 = 2x5x4x9x9x11

    hSPS = 4620x2= 2x5x4x3x7x11

    hFHC = 132930 = 2x5x7x9x211 => C=99.4 km

  • For rings synchronisation:

    hSPS/hLHC=7/27 => 7 Trev (LHC)

    hLHC/hFHC = 9x48/(7x211) => Tsync is 211 times longer

    hSPS/hFHC= 4x3x11/(9x211) => 132 Trev FCC

    => replace 211 by 216=12x18 (C=101.75 km)?? Or 204?

    For spacing of 125 ns (FHeC): 211=> 5x(4x11?) => 5% longer ring (103.7 km) or 0.5% shorter for 210=5x2x3x7


Summary

Summary

400 MHz

  • The RF system similar to the LHC (frf=400.8 MHz with Vmax=16 MV/beam) is able to provide at 50 TeVbunches with length of 8 cm (rms) for emittanceof 7.0 eVs (2 σ). In this case bucket area is 13.1eVs (qp= 0.77) andImZ/n for the loss of Landau damping is 0.2 Ohm.

  • With Vmax=16 MV injected emittance (at 1.7 TeV) should be less than 3 eVs.

  • Due to the synchrotron radiation damping a controlled longitudinal emittance blow-up (by band-limited RF phase noise) will be required not only during the acceleration ramp but also in the coast.

    200 MHz

  • The 200 MHz RF system has certain advantages, however the design of the SC version doesn't yet exist.

  • In this RF system for short bunch lengths the longitudinal beam stability will be at the limit and with RF voltage of 10 MV can be recovered (same margin as for in the 400 MHz RF) only for bunches longer than 12 cm (rms).

  • Another possibility to stabilise the beam is to use a double harmonic RF system (the 400 MHz RF system in addition).


  • Login