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
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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
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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-
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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
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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:
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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
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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
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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
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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
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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
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Heating Jackets
Cs-Oven 1-5 g
Cs-transfer line Co axial heating
Valves & collars
Two valves allow refilling without breaking the vacuum
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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
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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
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490 510 530 550 570 590 610 630 650
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510
520
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Hα Hβ
Operational & eagerly awaiting plasmas
100 lines/mm
2400 lines/mm grid
Plasma light & H- beam
LEBT FC intercepting the H- beam
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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