SpaceCharge 15,Trinity College, Oxford International Institute for Accelerator Applications Space charge studies of cyclotron 26th March 2015 Anna Kolano Dr Andreas Adelmann (PSI) Dr Christian Baumgarten (PSI) Prof Roger Barlow (University of Huddersfield)
In this presentation Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 2
4 separate sector isochronous cyclotron 72 MeV Beam current ~ 11 ma DC/2.7 ma CW Accelerator Frequency 50.63 MHz Quasi-stationary distribution formed due to space charge forces and strong transverse-longitudinal coupling Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 3
What do we do? 3D beam dynamics model of with space charge Estimate controlled and uncontrolled beam losses Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 4
Why do we do it? What are the true intensity limits of? To understand the machine after the upgrade Can an Injector 2-type machine be used for future projects e.g. IsoDAR What do we do? 3D beam dynamics model of with space charge Estimate controlled and uncontrolled beam losses Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 5
Why do we do it? What are the true intensity limits of Injector 2? To understand the machine after the upgrade Can an Injector 2-type machine be used for future projects e.g. IsoDAR What do we do? 3D beam dynamics model of Injector 2 with space charge Estimate controlled and uncontrolled beam losses How do we do it? Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 6
How do we do it? The Goal: minimize halo at the extraction minimize losses in HIPA OPAL (Object Oriented Particle Accelerator Library) C++ framework for general particle accelerator simulations Open source 3D Space charge Massively parallel Particle-matter interaction Multi-objective optimisation. OPAL Initial conditions (matched distribution linear space-charge model) Accelerated bunch for 0.5 10 ma (non-linear model) We consider 2 configurations: Production and Upgraded Ref:C. Baumgarten, A Symplectic Method to Generate Multi- variate Normal Distributions, arxiv:1205.3601v. Ref: C. Baumgarten, Transverse-Longitudinal coupling by Space charge in Cyclotrons, Phys. Rev. ST Accel. Beams 14, 114201, 2011. Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 7
Courtesy: Richard Kan, PSI Anna Kolano (PSI, IIAA) 8
Courtesy: Richard Kan, PSI Anna Kolano (PSI, IIAA) 9
Courtesy: Richard Kan, PSI Central region at energies between 0.87 and 2.5 MeV. Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 10
The approach Lattice Production set-up Upgraded set-up Anna Kolano (PSI, IIAA) 11
The approach Lattice Collimation Initial parameters Initial distribution Production set-up 4σ cut 2 MeV orbit Optimization Matched Distribution Upgraded set-up Verify with measurements Anna Kolano (PSI, IIAA) 12
Approach Lattice Collimation Initial parameters Initial distribution Production set-up 4σ cut 2 MeV orbit Optimization Matched Distribution Upgraded set-up Collimators 870 KeV orbit Optimization to match measurements 9mA matched Distribution Verify with measurements Anna Kolano (PSI, IIAA) 13
Approach Lattice Collimation Initial parameters Initial distribution Production set-up 4σ cut 2 MeV orbit Initial Param Optimization Matched Distribution Upgraded set-up Collimators 870 KeV orbit Optimization to match measurements Large scale optimization of 9mA matched Distribution Injection line + buncher Verify with measurements Anna Kolano (PSI, IIAA) 14
Production set-up Start at 2 MeV orbit 72 MeV in 76 turns 2 single gap 3 rd harm cav 2 double gap resonators Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 15
Planned upgrade Motivation I max turn# -3 72 MeV in 54 turns 2 double gap resonators 2 single gap resonators Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 16
Comparison Turn separation @ 2 ma 20 turns less ~ 40% increase in turn separation Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 17
Full bunch simulations Artificial collimation: 4 sigma cut in x & y Production Set-up In reality > 60% of original intensity lost at, followed by minimal extraction losses Upgraded Set-up 2 ma 4 ma 6 ma Injector 2 I max = 2.7 ma Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 18
Halo formation Quantifying halo Halo profile parameter Peakedness of the distribution Kurtosis normalized so h=1 is a Gauss-like distribution h>1 halo formation Oscillates when nonlinearities are present hx Halo parameter Ref: Allen, C K Wangler, T. et al, "Beam-Halo Measurements in High-Current Proton Beams, Physical Review Letters, 2002. Anna Kolano (PSI, IIAA) 19
Halo formation - intensity scans Y Coordinate system Z Beam direction X Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 20
bunch charge [C] Does the halo re-form? 4σ No cut Cutting continuously cut 6.5 ma 2.5 ma Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 21
RMS X (m) Does the halo re-form? 4σ No cut 6.5 ma cut cut 2.5 ma Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 22
Does the halo re-form? halo parameter Continuous 4σ cut - reasonable temporary approximation giving stationary beam Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 23
Does the halo re-form? halo parameter 2.5 ma beam: 4σ cut for the first 5 turns Continuous 4σ cut - reasonable temporary approximation giving stationary beam Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 24
[mm] Measurements: last turn bunch shape 6.00 5.00 4.00 3.00 2.00 1.00 0.00 length sigma [mm] width sigma [mm] correlation [ ] results RIZ1 in 2009 & 2010 (& 2001) approx. length sigma [mm] in year 2001 approx. width sigma [mm] in year 2001 0 500 1000 1500 2000 2500 current [ua] Ref: Rudolf Do lling, Memorandum from 23. Dezember 2010, Overview on Transport bunch parameters measured in 2009 and 2010 with the time-structure measurements" Measurements 870 kev orbit 0.5-2.3 ma Collimators vs The model: 2MeV orbit Matched distribution 4σ cut Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 25
[mm] Measurements: last turn bunch shape Continuous 4σ cut 6.00 length sigma [mm] results RIZ1 in 2009 & 2010 (& 2001) 5.00 4.00 3.00 width sigma [mm] correlation [ ] approx. length sigma [mm] in year 2001 approx. width sigma [mm] in year 2001 simulation width sigma mm simulation length Length sigma sim mm Width sim 2.00 1.00 0.00 0 500 1000 1500 2000 2500 current [ua] Vertically around 1 mm (1σ ) for both Comparable Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 26
Measurements: last turns radial profile Orbit pattern changes with intensity in Injector 2 KIP2 collimator cuts away large parts of the beam changing the betatron oscillations Trim coils are also used to force pattern that keeps the last valley in the same place What is the main pattern contributor? 72 MeV in 83 turns RIE1 probe used larger current range, last several turns Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 27
Measurements: last turns radial profile Orbit pattern changes with intensity in Injector 2 KIP2 collimator cuts away large parts of the beam changing the betatron oscillations (?) Trim coils are also used to force a pattern that keeps the last valley in the same place What is the main pattern contributor? Not KIP2 extraction septum Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 28
Intensity (a.u.) Small Scale Optimization Problem First, optimize initial conditions to match the orbit pattern with the measurements Objectives Fixed peak position at extraction Min Δ peaks Parameters P R ~2 ~2 Radius Design Variables Anna Kolano (PSI, IIAA) 29 R (mm)
I (μa) Collimator readings Measured data KIP2 KIP1 RIL2I4 KIL1 & 2 KIG3 KIG2 KIG1 KIV KIR1 KIR3 KIP4 KIV5 Anna Kolano (PSI, IIAA) 30
I (μa) Collimator readings Measured data KIP2 Intensity inversely related KIP1 RIL2I4 KIL1 & 2 KIG3 KIG2 KIG1 KIV KIR1 KIR3 KIP4 KIV5 Error on measurements ~2% (excl SEE) Some read very small currents and could be ignored Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 31
Towards a precise model RIL1 RIE1 72 MeV in 76 turns RIE2 Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 32
Towards a precise model Collimators rectangular boxes RIL1 KIP4 RIE1 KIG3 KIR3 KIP2 KIG1 KIV KIP3 KIR1 72 MeV in 76 turns RIE2 Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 33
Space charge is not all that bad! 9mA bunch going through Anna Kolano (PSI, IIAA) 34
Space charge is not all that bad! Last turn Anna Kolano (PSI, IIAA) 35
High resolution simulations How to quantify halo in such case? Anna Kolano (PSI, IIAA) 36
Large and Small Scale Optimization Problem Use large scale optimization to tune the set-up of the accelerator minimizing the losses with the real collimation set-up Continue collaboration with IBM + Objectives Max ΔR at septum Min losses at (5-7) Min ΔE at extraction Min ε at extraction Parameters Design Variables σ of the distribution {x, p x, <x p x >, y, p y, <y p y >} Collimator positions (5-7) P R, φ RF Radius ~10 ~18 Anna Kolano (PSI, IIAA) 37
Summary In Space charge forces combined with transverse-longitudinal coupling balanced appropriately can give a matched compact bunch We are entering the phase of more realistic model Some properties observed will require more in-depth understanding Data produced until now gives some idea of how the machine works under different modes and is converging to the measured data Next: Collimation model finish up and optimize Use large scale optimization to tune the set-up of the accelerator minimizing the losses with the real collimation set-up (IBM) Simulations starting from the injection line/buncher Repeat the process for upgraded Injector 2 model Anna Kolano (PSI, IIAA) Space charge studies of Injector 2 (29 August 2014, IBM Zürich) 38
Summary NGA CDT THANK YOU FOR YOUR ATTENTION International Institute for Accelerator Applications Anna Kolano (PSI, IIAA) Space charge studies of Injector 2 (29 August 2014, IBM Zürich) 39
Joho s scaling law Scaling Law Halo Parameter - Is the motivation of improving the RF to get higher intensities - at PSI the maximum attainable current indeed scales with the third power of the turn number - maximum energy gain per turn is of utmost importance in this type of high intensity cyclotron - with constant losses at the extraction electrode the maximum attainable current scales as: I max turn# -3 Loss turn# 3 Ref: W. Joho, in Proc. 9th Int. Conf. on Cyclotrons and their Applications (Caen, 1981), p. 337. Anna Kolano (PSI, IIAA) 40
Scaling Law Halo Parameter Anna Kolano (PSI, IIAA) 41
Scaling Law Halo Parameter RIZ1 probe Ref: Rudolf Do lling, First results of the new time-structure measurements at a few beam currents Anna Kolano (PSI, IIAA) 42
4 ma 4 sigma cut Anna Kolano (PSI, IIAA) IBM Zürich 29 August 2014 43