CERN’s Linac4 ion sources Status

RFQchopper lineDTLCCDTLPIMS

160 MeV 104 MeV 50 MeV 3 MeV86 m

H- source

2016 2015 2014 2013

M. Vretenar et.al., Progress in the Construction of Linac4 at CERN, 26th International Linear Accelerator Conference, LINAC12, Tel Aviv

IS-01 Volume, DESY PG

IS-02 Cs-surface

50 MeV P-source

2017-8

Connection to PSB

Reliability run

Linac4PS Booster

Linac2

PS50 MeV p

160 MeV H-

LEBT

Upgrade of the LHC injector chain:

From: 50 MeV p Linac2 To: 160 MeV H- Linac4 & striping at injection

In the PS-Booster

1

Test-stands

Simulation vs. measurements

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Linac4 IS Collaborations IPP Garching U. Fantz University of Jyvaskyla O. Tarvainen, T. Kalvas SNS M. Stockli KEIO University A. Hatayama 畑山明聖 IPGP Orsay T. Minea ISIS D. Faircloth BNL J. Alessi J-PARC A. Hueno CERN J.P. Corso, J. Coupard, M. Wilhelmsson, F. Fayet, D. Steyeart, E. Chaudet, Y. Coutron, A. Dallocchio, P. Moyret, S. Mathot, Y. Body, R. Guida, P. Carriè, A. Wasem, J. Rochez, D. Aguglia, D. Nisbet, C. Machado, N. David, S. Joffe, P. Thonet, J. Hansen, N. Thaus, P. Chigggiato, A. Michet, S. Blanchard, H. Vertergard, M. Paoluzzi, M. Haase, A. Butterworth, A. Grudiev, R. Scrivens, M. O'Neil, P. Andersson, S. Bertolo, C. Mastrostefano, E. Mahner, J. Sanchez, I. Koszar, U. Raich, F. Roncarlo, F. Zocca, D. Gerard, A. Foreste, J. Gulley, C. Rossi, G. Bellodi, J.B. Lallement, M. Vretenar, A. Lombardi

Matthias Kronberger SLHC-Fell.

CERN

Claus Schmitzer SLHC-PhD. Oystein Midttun PhD. Stefano Mattei Tech-Fell. Hugo Pereira Fell Jose Sanchez Dipl, Tech-Fell. Jaime Gil Flores Tech-Fell. Chiara Pasquino Tech-Fell. Cristhian Valerio PhD. Sylvia Izquierdo Tech-Fell. Mahel Devoldere Tech-Fell. Marco Garlasche Fell. Serhiy Mochalsky Fell. LPGP Orsay Taneli Kalvas PhD. Jyvaskyla Univ. Masatoshi Ohta 太田雅俊

Keio Univ. Masatoshi Yasumoto 安元雅俊 Kenjiro Nishida 西田健治朗

Takanori Shibata 柴田崇統

Takashi Yamamoto 山本尚史

Thank you all Students & Fellows

8+19+50=77

Linac4 tunnel Sept. 2013

3 MeV RFQ

45 kV LEBT

H2 distribution

2 MHz RF transformer

RF-Matching network

3

Installation of the LEBT, RFQ and Chopper line Commissioning with a 45 kV 20 mA class volume

source based on the DESY plasma Generator)

IS01: Volume 20 mA a) 60-100 kW plasma Generator b) DESY Plasma Generator IS02: Cesiated surface 40-50 mA IS03: BNL’s Magnetron (tbc.)

Sept. 2nd, 1st H- beam in the linac4 tunnel

Pulsed HVs FC-LEBT

Log RF

Plasma

H2-piezo valve 4

HV e-dump

Collar and plasma electrodes

Ferrites Magnets

Response of the Pulsed HV under dynamic load: 0.6 A electrons & 16 mA H-

5

Pulsed HV system: Beam energy fluctuation meets Specification, further improvement expected with

new controls electronics (end 2013) ± 0.5 kV stability throughout the beam pulse Detects over-currents and stops discharges. No traces of arcs on the electrodes Up to 3 A electron current successfully dumped at 10 keV on the e-dump, detailed

analysis in O. Midttun’s presentation

Pulsed Hydrogen delivery system

6

Faraday cage

-45kV

Ion source: Pulsed injection via piezo valve

LEBT: density regulation up to 1E-5 mbar at beam crossing.

Density stability <0.05%

Flow meters Interlock valves

P(t), Front end (2), Einzel lens and LEBT

RF-low level control:

7

Beams settings can now be saved and retrieved, via CERN control system RF – is phase locked to the initial trigger Huge improvement in tuning the RF pulse while seeing the plasma light, e-dump reflected RF and H- beam current Signal generation: 100 Msample/s arbitrary waveform generator, Waveforms calculated in software from freely programmable frequency and amplitude functions Signal acquisition: 100 Msample/s digitizer (ADC), Direct sampling of RF directional coupler signals. Quadrature demodulation in software to recover amplitudes and phases

Thanks to Andy & team : E. Roux, F. Dubouchet, M. Jaussi, G. Kruk

Continuous control of RF Power and Frequency over the pulse duration

VME crate

Function editor with RF amplitude function

IS02 prototype inspired from the SNS ion source

8

Cs-Oven

Cs-transfer line heating

Pulsed H2 injection piezo valve

Linac4 ion source front end

Einzel lens

Plasma Generator & Cesiated Mo-surface

Assembly completed last week, not tested !

Cesiated Mo-surface prototype inspired from the SNS-IS

9

Cs-Oven

Cs-transfer line heating

Linac4 ion source front end

Einzel lens

T-controlled Cesiated Mo-surface

IS02 Plasma generator

Puller e-dump

RF-solenoid 3-6 turns Multicusp octupole in offset Halbach

IS02 plasma Generator

10

Plasma view ports: on-axis, 19° & 26°

Permanent magnet Octupole cusp in

offset Halbach config. Cs-transfer line

T-regulated Cesiated

Mo-surface

Einzel lens electron dump

25 kV puller

3 to 6 turns solenoid antenna

Filter field

Temperature control of the Cesiated Mo-surface

11

Implementation of the on-axis, 19° & 26° Optical view ports

4 fibers (600μm core, 660μm clad, 710μm polyimide coating) inside of a SMA connector

Brazed sapphire + Quartz lens

3D-printing of the solenoid Epoxy mould

Cs-Oven

12

Heating Jackets

Cs-Oven 1-5 g

Cs-transfer line Co axial heating

Valves & collars

Two valves allow refilling without breaking the vacuum

13

Vertical actuator

Inficon Quartz sensor

Inert gas glove box & antechamber

Cs-test stand

Industrial washing system

• Cs-Oven filling • Flow and angular distribution of

the Cs-atomic beam • Cleaning of cesiated components

IS-test stand

14

Equipped identically to the first half of Linac4’s LEBT : Solenoid Faraday cup H-V grids Beam current transformer Gas-density regulation

Plasma and beam diagnostics : Optical photometry Spectrometer Emittance meter

FHR 1000, 2-Gratings 100 and 2400 lines/mm

3 Hamamatsu 10 MHz PMts

Optical Emission Spectrometry

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ICCD camera

Extraction port

Optical fibre light in

500

510

520

530

540

550

560

570

580

590

600

490 510 530 550 570 590 610 630 650

500

510

520

580 581 582 583 584

Hα Hβ

Operational & eagerly awaiting plasmas

100 lines/mm

2400 lines/mm grid

Plasma light & H- beam

LEBT FC intercepting the H- beam

16

LEBT BCT

Courtesy: U. Raich 27/3/13

2MHz ripple observed by M. Sordet, J. Tan BPM-ToF system

4 MHz fine structure observed in the plasma light emission,

O(10-15%) peak to peak .

2 MHz H- beam fine structure observed in the Volume source

equipped with the DESY PG: O(20%) peak to peak fluctuation

of the H- beam intensity (Av.: 16 mA) 0.2 µs/div

100 µs/div

Plasma ignition, stable beam region

I(RF) Hα Hγ Hβ

I(RF) Hα Hβ Hγ

Simulations vs. measurement

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H2-injection dynamics → 1) Neutrals at ignition ↔ P-meas. RF-field (Plasma conductivity) → 2) E and B fields

1+2 → PIC Plasma heating Keio → 3) e-density and EEDF 3 → CR-model → 4) H0 density … flux

5) Light emission ↔ OES-P observable 4 → Beam formation ONIX → 6) electron & H- beam, emittance 6 → Beam transport IBSimu → 7) emittance ↔ OES observable 7 → Beam neutralization

NIBS 2012 Jyvaskyla C. Pasquino, et.al., Vacuum simulation and characterisation for the LINAC4 H- source, AIP Conf. Proc. 1515 (2013) pp.401-408. S. Mochalskyy, et.al., Numerical modeling of the Linac4 negative ion source extraction region by 3D PIC-MCC code ONIX, AIP Conf. Proc. 1515 (2013) pp.31-40. ICIS 2013 Chiba , these proceedings. M. Ohta, et.al., Numerical Study of the Inductive RF-discharge Initiation for the Linac4 H- Ion Source. A. Grudiev, et.al., Numerical Simulation of Electromagnetic Fields and Impedance of CERN LINAC4 H- Source taking into Account the Effect of the Plasma. K. Nishida, et.al., Equivalent Circuit of RF-Plasma with The Transformer Model. S. Mattei, et.al., Plasma ignition and steady state simulations of the Linac4 H- Ion Source. T. Yamamoto, et.al., Modeling of Neutrals in the Linac4 H- Ion Source Plasma; Hydrogen Atom Production Density Profile and Hα Intensity by CR Model. Ø. Midttun, et.al., Measurements of Linac4 H- Ion Source Beam with a Magnetized Einzel Lens e-Dump. R. Scrivens, et.al., Linac4 Low Energy Beam Measurements with Negative Hydrogen Ions. C. A. Valerio-Lizarraga, et.al., Space Charge Compensation in the Linac4 LEBT with H- Ions.

CR-model prediction vs. Photometry (preliminary results)

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Many differences are identified between the simulation assumptions and the measurement conditions during plasma ignition transient, however; The effect of the solenoid induced E-field expected at low plasma density is visible in the on-axis View port. Hard work ahead … Experiment and simulation shall now focus on steady state plasma (suitable for H-

beam)

VP 30 deg. VP on-axis

Courtesy of Shibata-san, Yamamoto-san & Mattei san

Conclusion, Outlook Ion source, Cs and Piezo valve test stands operational An O(20 mA) intensity 45 kV H- beam is available in the linac4 tunnel The High density plasma of the Volume source upgraded to high RF power is not

suitable for H- beam The cesiated surface prototype is ready for the tests Impressive matching of the OEP time structure with the RF-Plasma CR simulation Volume and cesiated surface prototypes were designed and produced; Next steps: o Systematic testing under various plasma coupling. o Design and production of a new extraction; prerequisite is to solve the engineering

challenges of the main ceramic insulator. o Engineering of a Plasma Generator based on the RF-Plasma-beam-formation

simulation chain o From day 1, it seemed rather challenging to reach the 80 mA within the nominal

emittance of 0.25 mmmRad by end 2015; other options are: 1) 40 mA out of source are sufficient for all CERN beams + twice the present LHC intensity in 40 PSB

injection turns/ring. Higher intensity for the ISOLDE facility: Increase the number of PSB injection turns (600 µs

linac pulses) or reduce the chopping factor. 2) Build a BNL-Magnetron-type source, capable of higher currents. Address the engineering

modifications mandatory to operate at < 2Hz repetition rate and 45 keV beam energy 19