Linac 3 modelling Giulia Bellodi for the Linac

Linac 3 modelling Giulia Bellodi for the Linac 3 team, present and past • • • Current status of modelling What could be improved What could be used operationally Applications of ML? Future plans ABP Injectors Working Group meeting, 20/11/2020

• Current status of modelling • • What could be improved What could be used operationally Applications of ML? Future plans ABP Injectors Working Group meeting, 20/11/2020

Linac 3 sketch ABP Injectors Working Group meeting, 20/11/2020

Linac 3 operation (Pb beams) 5 m. A, 250 A of Pb 29+ ? ECRIS source, 2. 5 ke. V/u Stripper: Pb 29+ Pb 54+ ITF filter 32 -35 m. A Pb 54+ IH linac 4. 2 Me. V/u RFQ, 250 ke. V/u 180190 m. A Pb 29+ 190 -200 m. A In times of good performance: Source to slit ~ 75% transmission of Pb 29+ Slit to IH ~ 60% transmission of Pb 29+ Source to IH ~ 40% transmission of Pb 29+ LEBT filter

Several computer codes used for modelling Linac 3 sections: • IBSIMU @source (T Kalvas, Jyväskylä , Finland) • PATH @ITL, ITM, IH, ITF • PARMteq @RFQ (from LANL, this can be skipped if we get RFQ field map) ABP Injectors Working Group meeting, 20/11/2020

IBSIMU parameters Predictions vs observations • 3 D model of extraction geometry • 3 D magnetic field calculated with Opera (solenoids and hexapole) • Measured CSD during afterglow • Cold ion population • High plasma potential • Full space charge (low Pext, E fields, pulsed) Plasma electrode Intermediate electrode Grounded electrode V Toivanen Pumping chamber Beam pipe ABP Injectors Working Group meeting, 20/11/2020

PATH-Travel • Originally developed at LANL, heavily modified at CERN, under the responsibility of A. Lombardi • Can simulate linear accelerators and transfer lines • Important features : • • • 2 D and 3 D space charge (SCHEFF+ point-to-point) Integration in 2 d and 3 d field maps (static and RF) Simulation of up to 10 different ions Possibility of statistical error studies (machine and beam errors) Steering modules Input-output compatible with PARMILA, PARMTEQM, TRACE 3 d and TRACEWIN Can run up to 1 M particles Cross-checked with TRACEWIN on LINAC 4 and SPL simulations Included in the GSI code comparison started at HB 2004 ( A. Franchi) ABP Injectors Working Group meeting, 20/11/2020 A. Lombardi

IBSIMU extraction simulations Studied cases for which we have extracted beam particle distributions: • Pb 29 operational case • Ar 11 • Xe 21 V Toivanen ABP Injectors Working Group meeting, 20/11/2020

Pb 29+ extracted beam Triangular hollow shape ECRIS fingerprint All charge states Q=29 X-X' Emit [rms] = 0. 1544 Pi. mm. mrad Emit [95%] = 0. 7726 Pi. mm. mrad Beta = 2. 56 mm/Pi. mrad Alpha = -8. 7 0. 14 0. 12 Frequency 0. 1 0. 08 0. 06 O Pb 29+ is 5% of total 0. 04 0. 02 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 charge x = y=~12 mm

Linac 3 LEBT solenoid Complicated beam dynamics in a black box! 135 deg ABP Injectors Working Group meeting, 20/11/2020 Quad triplet

Solenoid 1 Bending 1 CSD gymnastics Bending 2 At slit-02 ABP Injectors Working Group meeting, 20/11/2020

Bending magnets: OPERA field map developed in 2016 by C Valerio Matrix dipole model vs field map Similar trends, but some differences in the vertical plane ABP Injectors Working Group meeting, 20/11/2020

Linac 3 LEBT and diagnostics synoptic slits FC SEM BCT No diagnostics installed until after the bend (and charge state selection). Very difficult (not possible? ) to benchmark simulations results starting point of simulations @ ITL triplet ABP Injectors Working Group meeting, 20/11/2020

ITL quad scans Xenon beam, ITL reconstructed Emittance/profile measurements and tomographic reconstruction to get initial beam distribution for Linac 3 modelling ABP Injectors Working Group meeting, 20/11/2020

Simulation of the RFQ: Parmteq ABP Injectors Working Group meeting, 20/11/2020

Beam dynamics restudy carried out in 2017/2018 (GB+S Benedetti) Benchmark of simulations and measurements. • Start-to-end* simulation from ITL triplet to ITF SEM grid • At the operating conditions, the simulated transmission matches the measured one • Model further validated by parameters variation, i. e. cavity voltages and solenoid fields • Phase space reconstruction in good agreement with the simulations, especially in ITF and ITM H plane S Benedetti Paper published The 2017 Xe run at CERN Linac 3: Measurements and beam dynamics simulations Review of Scientific Instruments 89, 123301 (2018) ABP Injectors Working Group meeting, 20/11/2020

ITM to ITF, PATH simulations 0. 10 pi. mm. mrad 1. 56 0. 22 mm/pi. mrad 0. 09 pi. mm. mrad -1. 45 0. 19 mm/pi. mrad RFQ output – actual design S Benedetti • RFQ output beam considered as input for this part of the line • In this section, losses occur mostly in the first part IH cavity IH 1 IH 2 IH 3 buncher Comparison of simulated and reconstructed ABP Injectors Working Group meeting, 20/11/2020 phase space at the IH linac output

ITFS Ion Electrical Intensity (arb) Pb 54+ 250 Pb 52+ ITFS. BSG 10 HV 200 150 slit 100 Stripper foils ITF. SLH 02 slit v 50 4. 2 Me. V/u Ion Electrical. Intensity (arb) Ion Electrical (arb) 300 Intensity (arbitrary units) BC After chicane r ~15% of particles in 54+ => 6. 5 108 Pb 54+ 300 ITF T 25 ITF. BSG 03 HV BCT 15 BSG = SEM grid SL = slit BCT = beam current transformer From Tank 3 * single charge state * 200 s 100 A => 4. 3 109 Pb 29+ ITF. SLH 01 Stripping foil Ramping cavity F Wenander After stripper foil * charge state distribution * 190 A on BCT 15 Pb 53+ Pb 52+ Pb 54+ 250 200 Pb 51+ Pb 55+ 150 Pb 50+ 100 Pb 56+ 50 0 0 215 225 235 245 Current BHZ 11 (A) 255 265 215 225 235 245 Current BHZ 11 (A) ABP Injectors Working Group meeting, 20/11/2020 255 265

F Wenander Physics through the foil 1. 2 <E> = 42. 9 ke. V/u for 75 g/cm 2 a. C 2. CSD shifts to lower charges 3. Increased straggling -> 1 4. 25 0. 8 Pb 54+ 0. 6 Exit energy 0. 4 0. 2 CSD nonequilibrium 0 E = 0. 95 ke. V/u (1 ) for 75 g/cm 2 (SRIM calculated – to be verified) b. Larger transverse emittance Δε/ε = (6 ± 2) % for the 100 g/cm 2 (measured during Linac 3 commissioning [5]) 4. 15 4. 1 0 a. Larger longitudinal energy spread 4. 2 4. 05 CSD equilibrium 100 200 300 Foil thickness (�g/cm 2) 4 400 No script/code is presently available to model beam passage through the stripping foil, just manual manipulations of beam distributions to account for these effects. ABP Injectors Working Group meeting, 20/11/2020 Exit energy (Me. V/u) (SRIM calculated – to be verified) Pb 54+ (normalized) 1. Lower exit energy 4. 3

Linac 3 Ramping and Debuncher Simulator (L 3 RDS) • • R Scrivens Simulation of the longitudinal dynamics only (no collective effects). Simple transport and energy change calculation. Works on time and momentum, not synchronous phase. Aims to accept control room settings (referenced to calibrations internally). Stripper included (characterized only by thickness ug/cm 2 – linear energy loss). Start with an input bunch (with Gaussian distribution) Loop multiple simulations of different phase settings to simulate energy ramp. 2. 15 m Phase slippage factors b=0. 094, f=101 MHz, d. T/T=-dv/v=-d. P/P => 11. 2 m dq = 27. 7 deg/ (%d. P/P) for RC dq = 144. 3 deg/ (%d. P/P) for DB

Exit of Accelerating Structure Entrance Ramping Cavity Entrance Debuncher Cavity Exit Ramping Cavity Ramping/debunching R Scrivens 2019 ABP Injectors Working Group meeting, 20/11/2020

C Valerio Transport studies through ITF, ITH, ITE -50 98 96 Pb 54 94 92 -30 90 -10 10 Phi (Degrees) 20 18 16 14 12 10 8 6 4 2 0 Slit Transmission (%) Ramping cavity effect in the Charge states Slit Transmission (%) 100 30 50 -35 ABP Injectors Working Group meeting, 20/11/2020 -15 5 Phi (Degrees) Pb 53 Pb 55 25

• Current status of modelling • What could be improved • What could be used operationally • Applications of ML? • Future plans ABP Injectors Working Group meeting, 20/11/2020

GB, Linac 3 meeting June 2020 Goal: build END-TO-END machine description file in PATH/TRAVEL format, from source extraction plane to the end of the ITF line. Tasks Resources Dates 1 produce RFQ field map description Tech End 2021 * 2 introduce stripping foil effects, not currently simulated (output CSD, added energy spread/transverse jitter) Tech End 2021 * 3 add element labels to output files Tech End 2021 * 4 tidy up existing files, baseline model of each section in gitlab GB End 2020 5 re-validate/cross-check with measurements (especially longitudinal plane calculations) GB End 2021 ** * Conditional on approval of a Tech student position for >8 months starting in 2021 at the latest ** Assume Linac 3 running in 2021 (at least for MDs) ABP Injectors Working Group meeting, 20/11/2020

• Current status of modelling • What could be improved • What could be used operationally • Applications of ML? • Future plans ABP Injectors Working Group meeting, 20/11/2020

CERN optics repository http: //acc-models. web. cern. ch/accmodels/linac 3/sections/ work ongoing, ITL/ITM sections started so far G Bellodi R Scrivens A Huschauer ABP Injectors Working Group meeting, 20/11/2020

Simulation tool available to predict ramping / debunching effect on beam. Coupled to machine (get/set), needs calibration during beam commissioning. R Scrivens ABP Injectors Working Group meeting, 20/11/2020

Tools for the source D Kuchler • GHOST – GTS-LHC operation support • Development started in 2017 using dedicated software • During LS 2 existing modules converted and integrated to the Linac 4 autopilot environment • To be debugged and improved during the next months • Two modules available • Oven power ramp-up after an oven refill • Extraction voltage tuning to maximise linac output • The development of further modules depends on the outcome of • optical plasma spectroscopy to gain knowledge about the lead content in the source • number crunching by ICS (presently studies with wavelet transform and Hilbert–Huang transform to detect early changes in the source behaviour) ABP Injectors Working Group meeting, 20/11/2020

Cluster analysis of the operational parameters of the GTS-LHC ion source by D. Ku chler, M. Mihailescu Analysis of operational data of the GTS-LHC ion source for the years 2015, 2016 and 2018 Aim: find patterns in the data that can be used for improvement of the source operation Method: clustering of the data with the Optigrid algorithm Results: No dedicated recurring patterns Many small clusters No significant difference between stable and unstable source operation (from the point of view of the clustering) Time dependencies play an important role Knowledge about the inside of the source is missing for further analysis => optical plasma spectroscopy may give hints about amount of lead vapour inside the source

Points for discussion • Tools (physics + models + working program) to describe beam dynamics in LINAC 3 exist. • They are still fairly specialist tools – some work is needed to make it easier to use for other. Who are the potential users? • They can be coupled with ML // diagnostics ABP Injectors Working Group meeting, 20/11/2020

Machine learning possibilities • Application for adiabatic optimisation of the LEBT and matching to the RFQ (first discussions between DK, RS and V Kain to try to use the Generic Optimization Framework) • Can be tried first with the code then on the machine ABP Injectors Working Group meeting, 20/11/2020

Linac 3 instrumentation upgrade proposal for O 4+ run FC BCT Screen RFA SEM Proposal to build a dedicated diagnostics spectrometer line downstream of the Linac 3 source in the ITL section. This would allow the possibility of permanent logging in operation and the implementation of feedback loops that could help achieve better performance stability (a gain going beyond the specific requirements for the O 4+ run). The exact list of diagnostics devices to be installed in the measurement line is still being discussed, as well as a feasible layout solution. The approximate total cost of this upgrade is currently calculated in the order of 1 Mchf. The budget request for 2020 is of 50 kchf to cover for instrumentation predesign phase (including integration studies). Manpower needs in 2020 are estimated at a total of 0. 5 FTE, to be shared between different groups. GB, December 2019 ABP Injectors Working Group meeting, 20/11/2020

Thank you for your attention ABP Injectors Working Group meeting, 20/11/2020