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Transcript of LINAC4 Meeting
LINAC4 Meeting
Status of the future CERN H- RF ion source
Th. Meinschad / AB-ABP-HSL
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
Contents
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: plasma production
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 …
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).
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: H- formation
D. Moehs: Proton Driver Requirements, May 2004
2: dissociative attachment
H- destruction
ALSO surface processes in the DESY source: recombinative desorption: H* + H* + wall H2(”) + wall
1:
Linac4 Meeting, Th. Meinschad, 2nd May 2006
Plasma ParametersnH2 ~ 1014 – 1015 cm-3
ne ~ 1012 – 1013 cm-3
TH_ ~ 0. 35 -1.4eV / 0.03-0.11eV
Te ~ 2eV / 15eV
RF driven volume source: E & M fields
Filter Field: ~ 200 Gauss
Cusp Field: ~ 2500 GaussPermanent Magnets (SmCo, NdFeB)Cooling ! (50kW RF/50mA H-/ 1% df / 500Watts)
Bacal et al.: IEEE Trans. on Plasma Science Vol. 33, No. 6
Solution: Tandem Source separation: DTe
-1/2
pressure ~ mTorrhydrogen flux ~ 1 - 10 sccm
emittance !
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: external antenna
Sputtering problems on the Porcelain coated antenna external antenna DESY and later SNS longer lifetime
R. F. Welton, RSI 75, 2004
In 2002 J. Peters (DESY) introduced the RF source with an external antenna to the H- community (Proc. EPAC 2002, p: 1727 – 1729).
SNS power upgrade (94mA, 1.23ms, 60Hz) similar to SPL requ.
Linac4 Meeting, Th. Meinschad, 2nd May 2006
H- Source Collaboration - STATUS
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 … )
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
Content of the Collaboration – what CERN gets !
Information – why a delay:
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: DESY type
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)
10 cm
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: DESY type
plasma chamber (Al2O3)
RF coil (water flushed)
VESPEL jacketwith SmCo bars – multicusp configuration
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: DESY type
H- correction
e- deflectionspace for e-dump
spectrometer (steel)water cooled
steel boxes with NdFeB insidelinings to shape the field
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: DESY setup
pump
HV cage (35kV), inside
HV cage (35kV), outside
source body
RF input, from coupling box
piezo valve & ignition source
coupling box (matching, HV insulation)
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: CERN concept I
source bucket (modified)
HV insulation & vacuumon 60kV platform
side view
DESY source bucket (1:1)
wall
Main issues:cost – use what is available, pumping connectionsas close to the 1st LEBT solenoid as possible
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: CERN concepts II
Pumps outside the HV cagePumps outside the HV cage600mm insulator
Pumps inside the HV cageSmall corona ring (230mm)
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: CERN concept (elec.)
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)
Preliminary !
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: compensation
H- pulse / measured at DESY !19.3kW forward / 1.2kW ref.
38mA peak/ 3 ms
Active / Passive compensation / Energy spread
passive: voltage droop over 0.4ms: 720V / 2.6 F, 200Factive: ~0V, 1.2F, 100F, complicated !
“unofficial” collaboration withSNS, FNAL: long pulse / emittance
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: RF Amplifier
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
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 transformer2 MHz for 100kV, df: 12%
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: facts & problems
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
What do we have to expect ?
Linac4 Meeting, Th. Meinschad, 2nd May 2006
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:
RF driven volume source: facts & problems
Emittance growth due to post-acceleration !
Linac4 Meeting, Th. Meinschad, 2nd May 2006
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: 80mA Pulse length: 0.4 ms Repetition rate: 2 Hz Duty Factor: 0.08 % Extraction: 95 kV ε90%n,rms: growth Caesium: X Lifetime:
RF driven volume source: facts & problems
Problems due to high current requirement !
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: TASKS
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:
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)
Linac4 Meeting, Th. Meinschad, 2nd May 2006
RF driven volume source: Time schedule