An Overview of BLonD Konstantinos Iliakis, Helga Timko BLonD - - PowerPoint PPT Presentation

An Overview of BLonD

Konstantinos Iliakis, Helga Timko

BLonD Overview July 28, 2017 1

Why do we need beam modeling?

• Better machine design
• Control and manipulate the beam (splitting, shaping etc)

− PSB 1 bunch, LHC: 2808 bunches

• To ensure beam quality and safe operation
• Beam instabilities can lead to

− Deterioration of beam quality, loss of luminosity − Beam losses that result in radiation and safety issues

• Older machines operate outside of originally designed

specifications

BLonD Overview July 28, 2017 2

Motivation for a Beam Dynamics Code

• Existing codes are not well maintained or reliable
• CERNs increasing need for more accurate predictions

− Simple models do not fit the observations due to the

increased bunch intensity

− Precise bunch distribution, impedance modeling, beam

control

BLonD Overview July 28, 2017 3

• Beam Longitudinal Dynamics simulator 1
• A simulation is composed of a pipeline of physics modules.
• BLonD is written in Python with C/C++ extensions for the

computational kernels.

• Important conclusions drawn using BLonD can be found in the

literature234.

1http://blond.web.cerh.ch, https://github.com/blond-admin/BLonD 2Helga Timko et al. “Studies on Controlled RF Noise for the LHC”. In: 54th ICFA Advanced Beam Dynamics Workshop on High-Intensity, High Brightness and High Power Hadron beams, East-Lansing, USA (2015). 3Helga Timko et al. “Benchmarking the Beam Longitudinal Dynamics Code BLonD”. In: 7th International Particle Accelerator Conference, Busan, Korea (2016). 4Alexandre Lasheen et al. “Synchrotron frequency shift as a probe of the CERN SPS reactive impedance”. In: 54th ICFA Advanced Beam Dynamics Workshop on High-Intensity, High Brightness and High Power Hadron beams, East-Lansing, USA (2015).

BLonD Overview July 28, 2017 4

Synchrotron Model

• RF stations
• Magnetic arcs
• Intensity effects

BLonD Overview July 28, 2017 5

Features and Usability of BLonD

Features

• Single/ Multi-bunch options
• Acceleration, Multiple RF

systems and RF stations

• Collective effects
• Beam based/ cavity based

feedbacks

• Multi-turn effects
• Monitoring, plotting, data

analysis

Usability

• Match / explain experimental
• bservations
• Make accurate predictions/

cross-check with measurements

• Trace down the source of

limitations/ instabilities

• Guide decisions for machine

upgrades and predict beam behavior

BLonD Overview July 28, 2017 6

A Typical BLonD Simulation

Particle tracking

• Vector-vector operations
• Transformations applied to all

particles

• Up to 100M currently
• x10 increase is foreseen
• Multi-bunch simulations
• Up to 72 bunches for SPS

but 288 are needed

• 1000s of bunches for the

LHC

Sliced tracking

• Modeling interactions between

particles and machine (impedance, feedbacks)

• Well know algorithms used:
• Histogram
• FFT
• Convolution
• Impedance dictates frequency

resolution which defines #bins

• Future machines (FCCee) will

increase radically the #bins

BLonD Overview July 28, 2017 7

Present Computational Challenges

• Large number of particles is required to provide sufficient

frequency resolution for impedance calculation and avoid numerical noise in space charge simulations

• Three different types of time consuming simulations:
• SPS ramp with 72 bunches and intensity effects (1 day)
• LHC ramp with feedbacks, emittance blow-up, few

bunches (1 week)

• PSB ramp with intensity effects, multi-turn wake,

feedbacks, emittance blow-up and periodicity

• Parameter scans: thousands of small/medium sized

simulations

BLonD Overview July 28, 2017 8

Thank you for your attention

BLonD Overview July 28, 2017 9