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LINAC4 Meeting

LINAC4 Meeting. Status of the future CERN H - RF ion source Th. Meinschad / AB-ABP-HSL. Contents. Introduction (volume source /H - production / optimisation ) Collaboration – STATUS The DESY source (information) CERN concept (possible designs / compensation / RF)

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LINAC4 Meeting

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  1. LINAC4 Meeting Status of the future CERN H- RF ion sourceTh. Meinschad / AB-ABP-HSL

  2. Contents • Introduction (volume source /H- production / optimisation ) • Collaboration – STATUS • The DESY source (information) • CERN concept (possible designs / compensation / RF) • LEBT (simulations / emittance growth: RS) • What do we have to expect ? • What has to be done ! • Time Schedule Linac4 Meeting, Th. Meinschad, 2nd May 2006

  3. RF driven volume source: plasma production rot E = - dB/dt describes a curling electrical field generated by a changing magnetic field in the absence of charge. Such a B-field can be produced with an alternating current i=i0cos(wt). Inductively coupled plasma generated by 2 MHz RF. The curling E-field is concentrated inside the solenoidal antenna loops with the highest ionizing field close to the antenna.Well suited for producing plasma in a large volume, which can be easily confined with a multicusp magnetic field. Other industrial applications: coating, etching … Linac4 Meeting, Th. Meinschad, 2nd May 2006

  4. RF driven volume source: H- formation H- destruction 2: dissociative attachment 1: ALSO surface processes in the DESY source: recombinative desorption: H* + H* + wall  H2(”) + wall D. Moehs: Proton Driver Requirements, May 2004 Linac4 Meeting, Th. Meinschad, 2nd May 2006

  5. RF driven volume source: E & M fields Cusp Field: ~ 2500 Gauss Permanent Magnets (SmCo, NdFeB) Cooling ! (50kW RF/50mA H-/ 1% df / 500Watts) Filter Field: ~ 200 Gauss Solution: Tandem Source separation: DTe-1/2 pressure ~ mTorr hydrogen flux ~ 1 - 10 sccm Plasma Parameters nH2 ~ 1014 – 1015 cm-3 ne ~ 1012 – 1013 cm-3 TH_ ~ 0. 35 -1.4eV / 0.03-0.11eV Te ~ 2eV / 15eV emittance ! Bacal et al.: IEEE Trans. on Plasma Science Vol. 33, No. 6 Linac4 Meeting, Th. Meinschad, 2nd May 2006

  6. RF driven volume source: external antenna In 2002 J. Peters (DESY) introduced the RF source with an external antenna to the H- community (Proc. EPAC 2002, p: 1727 – 1729). Sputtering problems on the Porcelain coated antenna  external antenna DESY and later SNS  longer lifetime SNS power upgrade (94mA, 1.23ms, 60Hz) similar to SPL requ. R. F. Welton, RSI 75, 2004 Linac4 Meeting, Th. Meinschad, 2nd May 2006

  7. H- Source Collaboration - STATUS Information – why a delay: • DESY wanted to develop the collaboration to a prime example for further collaborations (other research labs are also interested) • 1st proposal from DESY arrived, CERN sent a improved version back • if both partners agree upon the collaboration paper, the technical annex can be attacked (details of the collaboration) – maybe critical ! • Constant improvement of the source  new tech. drawings (e.g.: spectrometer, biased plasma electrode … ) Content of the Collaboration – what CERN gets ! • Technical drawings (up to date) in digitized version (IDEAS) • Equipment: Ignition Source & Piezo Gas Valve • Small (defined) amount of manpower • basically no other costs for CERN Linac4 Meeting, Th. Meinschad, 2nd May 2006  Expectation: drawings will arrive beginning of July !

  8. RF driven volume source: DESY type 10 cm COLL DESY RF source Current: 40 mA (54 mA!) Pulse length: 0.1 ms Repetition rate: 5 Hz Duty Factor: 0.05 % Extraction: 35 kV ε90%n,rms: 0.25 mm mrad Caesium:  free Lifetime: 25000 hours RF volume source with the best performance ! (surface & volume) Linac4 Meeting, Th. Meinschad, 2nd May 2006

  9. RF driven volume source: DESY type plasma chamber (Al2O3) VESPEL jacket with SmCo bars – multicusp configuration RF coil (water flushed) Linac4 Meeting, Th. Meinschad, 2nd May 2006

  10. RF driven volume source: DESY type spectrometer (steel) water cooled H- correction e- deflection space for e-dump steel boxes with NdFeB inside linings to shape the field Linac4 Meeting, Th. Meinschad, 2nd May 2006

  11. RF driven volume source: DESY setup piezo valve & ignition source pump HV cage (35kV), outside HV cage (35kV), inside source body RF input, from coupling box coupling box (matching, HV insulation) Linac4 Meeting, Th. Meinschad, 2nd May 2006

  12. RF driven volume source: CERN concept I wall DESY source bucket (1:1) HV insulation & vacuum on 60kV platform side view Main issues: cost – use what is available, pumping connections as close to the 1st LEBT solenoid as possible source bucket (modified) Linac4 Meeting, Th. Meinschad, 2nd May 2006

  13. RF driven volume source: CERN concepts II Pumps inside the HV cage Small corona ring (230mm) Pumps outside the HV cage 600mm insulator Pumps outside the HV cage Linac4 Meeting, Th. Meinschad, 2nd May 2006

  14. RF driven volume source: CERN concept (elec.) Preliminary ! • 2 HV platforms (post-acc) • active OR passive compensation • RF Generator (on ground) • Coupling box (matching & HV isolation • 2 CERN pumping stations (30 m3/h scroll & 500l/s TMP) on a 60kV platform • 2 (50Hz) isolation transformer • 2 racks on Teflon bars Base area: 3.0 x 2.8 m2 !! Schematics of the HV cage (passive compensation) Linac4 Meeting, Th. Meinschad, 2nd May 2006

  15. RF driven volume source: compensation Active / Passive compensation / Energy spread “unofficial” collaboration with SNS, FNAL: long pulse / emittance passive: voltage droop over 0.4ms: 720V / 2.6 F, 200F active: ~0V, 1.2F, 100F, complicated ! 38mA peak/ 3 ms H- pulse / measured at DESY ! 19.3kW forward / 1.2kW ref. Linac4 Meeting, Th. Meinschad, 2nd May 2006

  16. RF driven volume source: RF Amplifier A RF generator (~2MHz, 50, ~1-2kV ~20-30A peak) produces a RF signal, which is used to heat the Hydrogen plasma. The generator is coupled to the RF coil (L ~ H, some ohms at 2MHz) via an impedance matching network. The RF power is coupled into the plasma inductively (transformer model). Problem: RF isolation transformer 2 MHz for 100kV, df: 12% RF Generator (M. Paoluzzi): (SPL specs) 1.8-2.2MHz, rep. rate: 1-60Hz, pulsed, pulse length: 0.2-2ms, 1-100kW peak power, sine wave, low distortion level, high pulse stability Linac4 Meeting, Th. Meinschad, 2nd May 2006

  17. RF driven volume source: facts & problems What do we have to expect ? DESY RF source Current: 40 mA (54 mA!) Pulse length: 0.1 ms Repetition rate: 5 Hz Duty Factor: 0.05 % Extraction: 35 kV ε90%n,rms: 0.25 mm mrad Caesium:  free Lifetime: 25000 hours Linac4 Meeting, Th. Meinschad, 2nd May 2006

  18. RF driven volume source: facts & problems Emittance growth due to post-acceleration ! DESY RF source Current: 40 mA (54 mA!) Pulse length: 0.1 ms Repetition rate: 5 Hz Duty Factor: 0.05 % Extraction: 35 kV ε90%n,rms: 0.25 mm mrad Caesium:  free Lifetime: 25000 hours CERN RF source(3MeVTCC) Current: +40 mA Pulse length: 0.4 msRepetition rate: 1 HzDuty Factor: 0.04 % Extraction: 95 kVε90%n,rms: growth Caesium:  free Lifetime: Linac4 Meeting, Th. Meinschad, 2nd May 2006

  19. RF driven volume source: facts & problems Problems due to high current requirement ! DESY RF source Current: 40 mA (54 mA!) Pulse length: 0.1 ms Repetition rate: 5 Hz Duty Factor: 0.05 % Extraction: 35 kV ε90%n,rms: 0.25 mm mrad Caesium:  free Lifetime: 25000 hours CERN RF source(3MeVTCC) Current: +40 mA Pulse length: 0.4 ms Repetition rate: 1 Hz Duty Factor: 0.04 % Extraction: 95 kV ε90%n,rms: growth Caesium:  free Lifetime: CERN RF source(LINAC4) Current: 80mAPulse length: 0.4 msRepetition rate: 2 HzDuty Factor: 0.08 % Extraction: 95 kV ε90%n,rms: growth Caesium:  X Lifetime: Linac4 Meeting, Th. Meinschad, 2nd May 2006 Money ! Work !

  20. RF driven volume source: TASKS Technical drawings (DESY) Implementation (final design, CERN) Construction (company) RF Generator (RF) Equipment (CERN) LEBT (low cost) Installation (HSL) Pressure Test (end 2006) HV Test (HSL) Plasma Test (HSL) Commissioning (HSL) LEBT design (low growth) DESY RF source Current: 40 mA (54 mA!) Pulse length: 0.1 ms Repetition rate: 5 Hz Duty Factor: 0.05 % Extraction: 35 kV ε90%n,rms: 0.25 mm mrad Caesium:  free Lifetime: 25000 hours CERN RF source(3MeVTCC) Current: +40 mA Pulse length: 0.4 ms Repetition rate: 1 Hz Duty Factor: 0.04 % Extraction: 95 kV ε90%n,rms: growth (+33%)Caesium:  free Lifetime: CERN RF source(LINAC4) Current: 80mA Pulse length: 0.4 ms Repetition rate: 2 Hz Duty Factor: 0.08 % Extraction: 95 kV ε90%n,rms: growth (+6%)Caesium:  X Lifetime: Linac4 Meeting, Th. Meinschad, 2nd May 2006 at least: 2006

  21. RF driven volume source: Time schedule Linac4 Meeting, Th. Meinschad, 2nd May 2006

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