This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871.

Comprehensive simulations of distortions and their mitigations related to measurements with ionisation profile monitors

1st ARIES Annual Meeting

Riga Tech. Univ., Latvia

May 24th, 2018

Dominik Vilsmeier / GSI

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Preface

M. Sapinski et al 2012 "The first experience with LHC Beam Gas Ionization Monitor" Proc. IBIC2012

Beam Gas Ionization Monitor installed at LHC (CERN)

Profile broadening compared to Wire Scanner data

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Profile broadening - why?

  • Distortion of electron trajectories due to beam space charge
  • Distortion due to electron gyroradius
  • Effects related to MCP
  • Optical point-spread function

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Simulations

PyECLOUD

(electron cloud studies)

PyECLOUD-BGI

(electron movement in IPM)

Available

Adaption for IPM

Upgrade

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Workshop @ CERN | 2016

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Workshop @ CERN | 2016

  • Design of electrodes for new devices
  • Simulation of field configuration for removing electron cloud from the device volume
  • Simulation of profile distortion
  • Simulation code involving ionization and transport of electrons in realistic fields
  • Code base with core developers
  • Infrastructure for code maintenance and user support

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Simulation codes

Various programs / scripts:

  • different applications    (LINAC, Synchrotron, ...)
  • different solutions

Combine the effort and create a common tool

→ suitable for all different use cases

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Code modularity

Simulation

Initial

velocities

Beam

fields

Guiding

fields

Particle

tracking

Single and double

ionization cross sections

Gas jet velocity

Uniform fields

Two and three dim.

CST field maps

Analytic formulations

Numerical solvers

Both two and three dim.

Varying in computational

complexity as well as

numerical accuracy

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Workshop @ GSI | 2017

33 participants

 

13 institues

 

9 countries

BINP

Sponsored by

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Workshop @ GSI | 2017

Compilation of IPM realization

Operational issues

Simulation code innovation

Present the new simulation tool

Collect feedback from the community

Benchmark simulation against each other

Perform measurements for comparison with data

Discuss new use cases and applications

Investigate corresponding models

Sponsored by

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Virtual-IPM

https://pypi.org/project/virtual-ipm

https://gitlab.com/IPMsim/Virtual-IPM

  • Emphasis on flexibility and extensibility
  • Covers a broad range of use cases
  • Acts as framework as well as stand-alone application
  • Suitable for developers and users
$ pip install virtual-ipm  # Easy installation

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Graphical User Interface 

<?xml version="1.0" ?>
<Virtual-IPM version="1.2.2">
  <Beams>
    <Beam>
      <Parameters>
        <Energy unit="TeV">6.5</Energy>
        <BunchPopulation>2.1e+11</BunchPopulation>
        <ParticleType>
          <ChargeNumber>1</ChargeNumber>
          <RestEnergy unit="MeV">
            %(proton mass energy equivalent in MeV)
          </RestEnergy>
        </ParticleType>
      </Parameters>

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Graphical User Interface

XML configuration format

  • Descriptive and clear
  • Easy in-file modifications

Command Line Interface

  • Straightforward access to simulations
  • Provides feedback about status

Graphical User Interface

  • Adaptive - Enhancements to the code are readily reflected in the GUI

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Use cases

IPM Profile distortion

  • Guiding field non-uniformities
  • Beam space-charge interaction
  • Influence of ionization momenta
  • IPM Profile "rectification", e.g. through device upgrades or software based solutions

IPM Design

  • Field cage design
  • Magnetic field strength required for suppressing distortions

BIF space-charge effects

  • Excited ions move under the influence of beam fields
  • Gas jet velocity is retained by ions

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

PS IPM Design

Profile distortion cannot be sufficiently suppressed by electric field

Confirming the requirement for a magnetic guiding field

Energy 25 GeV
Bunch pop. 1.33e11
Bunch size 3.7 x 1.4 mm
  - length (4σ) 3.0 ns

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

IPM & Beam parameters

Beam Parameter Value
Particle type Protons
Energy 25 GeV
Bunch pop. 1.33e11
Bunch width (1σ) 3.7 mm
Bunch height (1σ) 1.4 mm
Bunch length (4σ) 3.0 ns
IPM Parameter Value
Electrode distance 70 mm
Applied voltage 11 kV
Applied magnetic field 0.2 T

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

LHC Profile distortion

Beam
Energy 6.5 TeV
Bunch pop. 2.1e11
Bunch size 270 x 360 μm
  - length (4σ) 0.9 ns
IPM
Electrode dist. 85 mm
Applied voltage 4 kV
Magnetic field 0.2 T

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

IPM & Beam parameters

Beam Parameter Value
Particle type Protons
Energy 6.5 TeV
Bunch pop. 2.1e11
Bunch width (1σ) 270 μm
Bunch height (1σ) 360 μm
Bunch length (4σ) 0.9 ns
IPM Parameter Value
Electrode distance 85 mm
Applied voltage 4 kV
Applied magnetic field 0.2 T

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

LHC Profile distortion

Gyro-velocity oscillates due to ExB-drift

Electrons end up with increased velocity

Displacement due to ...

... ionization (Δx1)

... space-charge (Δx2)

... gyro-motion (Δx3)

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

SPS Profile distortion

Measurement at 16 mT

Convoluted with 520 μm point-spread function

Energy 450 GeV
Bunch pop. 2.86e11
Bunch size 835 x 451 μm
  - length (4σ) 1.6 ns

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

IPM & Beam parameters

Beam Parameter Value
Particle type Protons
Energy 450 GeV
Bunch pop. 2.86e11
Bunch width (1σ) 835 μm
Bunch height (1σ) 451 μm
Bunch length (4σ) 1.6 ns
IPM Parameter Value
Electrode distance 70 mm
Applied voltage 4 kV
Applied magnetic field 16 mT

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

BIF for e-Lens @ HL-LHC

Vacuum gauge

N2 fluorescent gas

Beam

Viewport

Lens, Image-Intensifier, Camera

BIF schematic

N2 gas jet

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

BIF for e-Lens @ HL-LHC

Simulation of complex setup for diagnostics based on BIF with supersonic gas jet

Excited ions interact with beam fields and suffer from a displacement until they decay

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

BIF & Beam parameters

p-Beam Parameter Value
Particle type Protons
Energy 7 TeV
Bunch pop. 2.2e11
Bunch width (1σ) 1.02 mm
Bunch height (1σ) 1.02 mm
Bunch length (4σ) 1.25 ns
BIF Parameter Value
Gas jet 800 m/s, 30 K
N2+* lifetime (391 nm) 60 ns
e-Beam Parameter Value
Particle type Electrons
Type DC beam
Energy 10 keV
Beam current 4 A
Inner radius 1.2 mm
Outer radius 1.8 mm

e-Lens: Additional 4 T long. magn. field

Preliminary parameters; S. Udrea et al "Preparatory work for a fluorescence based profile monitor for an electron lens" Proc. IBIC2016

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Profile reconstruction

Machine Learning

... can be used for establishing a relationship between measured profiles and beam profiles.

E.g. deep learning

Measured profile

Beam profile

Beam pars.

This relationship is inferred using data obtained from IPM simulations.

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

IPM & Beam parameters

Beam Parameter Value
Particle type Protons
Energy 6.5 TeV
Bunch pop. [1e11] 1.1 – 2.1 ppb
Bunch width (1σ) 270 – 370 μm
Bunch height (1σ) 360 – 600 μm
Bunch length (4σ) 0.9 – 1.2 ns
IPM Parameter Value
Electrode distance 70 mm
Applied voltage 4 kV
Applied magnetic field 0.2 T

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Profile reconstruction

Application of Machine Learning for deducing the relation between measured (distorted) and original beam profiles

Sweep the relevant parameter space and use simulation data for training

Parameter Range
Bunch pop. [1e11] 1.1 – 2.1 ppb
Bunch width (1σ) 270 – 370 μm
Bunch height (1σ) 360 – 600 μm
Bunch length (4σ) 0.9 – 1.2 ns

Very good results for testing with simulation data → first tests with measurement data are planned

1st ARIES Annual Meeting, May 24th 2018, D. Vilsmeier

Conclusions

https://ipmsim.gitlab.io/IPMSim

Lots of advancement in the field of IPM simulations

The efforts were combined into a common and generic simulation tool

Allows for simulating a broad range of cases, including LINACs, Synchrotrons and other beam instruments such as BIF monitors

Simulations are not only useful concerning IPM design but can also be used for software-based profile reconstruction (work in progress)

The community efforts have led to an established collaboration concerned about topics related to simulations of IPMs and similar beam instruments

Realization of the various tasks was possible thanks to the active participation of:

Peter Forck (1)

Mariusz Sapinski (1)

Kenichirou Satou (2)

Rahul Singh (1)

James Storey (3)

Serban Udrea (1)

(1) GSI     (2) J-PARC/KEK     (3) CERN

Thank you

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