ps-to-sps beam transfer studies
DESCRIPTION
PS-to-SPS Beam Transfer Studies. Helga Timkó BE-RF-BR in collaboration with Theodoros Argyropoulos , Thomas Bohl, Heiko Damerau , Steven Hancock, Juan Esteban Müller, Elena Shaposhnikova. Outline. Motivation for the beam transfer studies Earlier Today Measurement results - PowerPoint PPT PresentationTRANSCRIPT
PS-to-SPSBeam Transfer Studies
Helga Timkó BE-RF-BR
in collaboration withTheodoros Argyropoulos, Thomas Bohl, Heiko
Damerau, Steven Hancock, Juan Esteban Müller, Elena Shaposhnikova
LIU-SPS WG on Beam loss… 2
Outline
Motivation for the beam transfer studies Earlier Today
Measurement results Why we did not understand them
A few highlights of our simulation results Explaining past observations New ideas for optimisation
On-going work
16th May 2012
MOTIVATIONPS-TO-SPS TRANSFER:
Motivation for the transfer studies – Earlier…
A few years ago still, losses were very high Typically around 10-20 %
Þ The currently operational SPS flat-bottom (FB) scheme and many other settings were optimised through these studies
2004
E. Shaposhnikova et al.: Capture loss of the LHC beam in the CERN SPS
Nominal LHC intensity (~1.1-1.3 1011 ppb), 25 ns
LIU-SPS WG on Beam loss… 5
…as a function of intensity…
Losses increase significantly with intensity Þ will be a problem in future
Why do losses increase with intensity? Higher intensity εL more
losses Beam loading deformation
of bucket more losses
16th May 2012
J. Esteban Müller
Losses increase with bunch intensity
…and today
Today, losses are down to ~5 % for nominal intensity (due to scrubbing) When we’ll increase intensity, losses will be significant again The SPS bucket is already very full at injection
Would like to use a larger εL, which is good for Stability in the PS & SPS Higher intensity beam – planned for future LHC operation
The PS has been upgraded many times over the past 50 years and will be pushed to its limits with the future intensity requirements Minimising the losses in the injector chain is essential in order
to deliver the required intensity to the LHC!
PREVIOUS MEASUREMENTS
PS-TO-SPS TRANSFER:
LIU-SPS WG on Beam loss… 8
MDs: 25 ns and 50 ns beam
50 ns: 4th July 2011 25 ns: 7th November 2011
Transmission didn’t improve using 900 kV for the bunch rotation in the PS
16th May 2012
SIMULATION HIGHLIGHTSPS-TO-SPS TRANSFER:
Our model
In our simulations, we use Real, averaged phase-space distributions of the bunches
• From tomography measurements at the PS FT Real voltage programmes in PS and SPS Single bunch simulations, no intensity effects have been taken
into account
LIU-SPS WG on Beam loss… 11
Emittance blow-up
There is an emittance blow-up (due to the synchronisation loop) in the PS included also in the simulations
16th May 2012
LIU-SPS WG on Beam loss… 12
Simulating the 50 ns case
Transmission measured at SPS FB, before the acceleration V200 MHz = 2 MV, V800 MHz = 0.34 MV in bunch-shortening mode
Reproduce exp. results when emittance blow-up is added
16th May 2012
LIU-SPS WG on Beam loss… 13
So, why is the transmission not improved?
There is no improvement with larger voltage, because Bunches have a particular shape and Buckets are very full;
To improve the transmission, need to improve the shape
16th May 2012
LIU-SPS WG on Beam loss… 14
PS rotation timing However, in the MDs
above we adjusted only t80 MHz
t40 MHz = 150 μs was kept the same for both 600 kV and 900 kV cases
16th May 2012
SPS
OPTIMISATION STUDIESPS-TO-SPS TRANSFER:
LIU-SPS WG on Beam loss… 16
Optimising the bunch rotation
For 1+2 cavities, optimal timing reduces losses: 4.4 % 3.5 %
Using 2+3 cavities instead of 1+2:
3.5 % 1.3 % N.B. only t40 MHz is
optimised based on transmission, t80 MHz is optimised based on bunch length
16th May 2012
LIU-SPS WG on Beam loss… 17
Optimised bunch shapes
… now improved:tails less populated
16th May 2012
LIU-SPS WG on Beam loss… 18
Effect on transmission
With optimised timing and 900 kV in the PS: Losses are reduced, despite having longer bunches
16th May 2012
LIU-SPS WG on Beam loss… 19
SPS capture voltage
Using the SPS voltage & momentum programme for the acceleration ramp, we simulated injection & acceleration:
16th May 2012
23 MV has 3-4 % better transmission than 3 MV No difference between 2 MV and 23 MV is seen in our sims 23 MV stands for: 2 MV at batch injections, 3 MV in-between injections
ONGOING MDSPS-TO-SPS TRANSFER:
Verification of our results
2012-03-29 MD: optimising the PS bunch rotation timing Preliminary results, need further measurements (beam
conditions were changing)
LIU-SPS WG on Beam loss… 22
Conclusions & outlook
Earlier, transmission was not improved with V80 MHz,PS = 900 kV, due to the ‘S-shape’ of the bunch and a full SPS bucket
Bunch shape has to be optimised during the PS rotation Simulations predict a gain of a few % by optimising the PS
bunch rotation timing First MD results are encouraging
The SPS FB voltage influences the losses in the beginning of the acceleration ramp
We can expect significant increase in losses for higher emittances (intensities) Simulations including intensity effects are planned
16th May 2012