operational aspects 2008 run iscool isolde workshop 17-19 nov 2008 erwin siesling
TRANSCRIPT
Operational aspects
2008 run
ISCOOL
Isolde workshop 17-19 Nov 2008
Erwin Siesling
Isolde workshop 08: ISCOOL OP aspects E. Siesling 2
Overview
ISCOOL: RFQ cooler and buncher at Isolde
• Hardware• Functionality, principle and specs• Technical issues 2007/2008• Results 2008 run• Shutdown consolidation• Summary
Isolde workshop 08: ISCOOL OP aspects E. Siesling 3
ISCOOL hardware
Inj. Triplet Ej. TripletRFQ tank
Instrum.60 kV
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ISCOOL hardware
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HRS
GPS
Located right after the HRS separator magnets
RFQ Cooler and buncher
ISCOOL hardware
Isolde facility
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60keV HV platform & RF
ISCOOL hardware
Isolde facility
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ISCOOL functionality
• RFQ: Confines the beam and reduces energy spread for better transmission and higher mass spectroscopy efficiency
• Bunch mode: Bunches the beam for background supression
Continuous mode & Bunch mode
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Courtesy Dr. H. Franberg
ISCOOL principle
He buffer-gas:Interactions decelerate the particles to a few eV
RF power:4 transverse rods. Confines the beam
Mathieu equation 2
02
4
rm
Ueq
RF
RF
Electrodes:Potentials along the axis. 3 last and extraction plate can be pulsed
HV extraction voltage:60kV to extract and accelerate the beam out of the RFQ
RFQRF
Bunch mode
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• Emittance:• Transmission:• Cooling time:• Space charge:• Pulse width:
ISCOOL specs
from 35π.mm.mrad to 2.2 π.mm.mrad
better than 70% for A>39
TOF <1ms, one passage enough to cool the beam
up to 1E8/s !
depends on space charge and cooling time
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• The ISCOOL has been performing remarkably well during the 2008 run with only a few minor technical problems
• 2007/8 shutdown consolidation:- elements controllable from RFQ workingset & QP array - vacuum leaks fixed & interconnections improved- re-aligned
• 2008 operation issues:- Excessive use of He buffer gas- RF amplifier break down (due to abrupt HV switching)
ISCOOL tech issues
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• Workingset for all elements
2007/8 consolidation
• QP arrays: Archive to save and reproduce settings for different targets and users
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2007/8 consolidation
Vacuum leaks repaired & connections improved
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2007/8 consolidation
Re-alignment:
?
Aligned with respect to the faraday-cups: displacement of the beam with regard to the scanners of hor -10mm, vert +30mm stayed
With beam..
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2008 Operation issues
He
Buffergas pressure: ~1E-2 mbar 4HeEstimated: 10-2mbar l/s
But…
Helium ‘addiction’:
- Using 3x more
- Bottle needs changing ~6 weeks
- Filling-up Isolde gas-recuperation tanks faster
He buffergas
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2008 Operation issues
RF amplifier & synthesizer
High Voltage sensitive:
- Break down due to abrupt HV switching
- Will be replaced this shutdown (+ spare)
60kV
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ISCOOL 2008 results
• ISCOOL transmission• Beamline transmission• Bunch mode
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Inj. Triplet Ej. TripletRFQ tank
Instrum.
ISCOOL online transmission
0102030405060708090
0 50 100 150 200 250
Mass
tran
smis
sion
effi
ency
[%]
Continous mode Pulsed mode Slits
0
20
40
60
80
100
0 50 100 150 200 250
Mass
Tran
smis
sion
effi
cien
cy [%
]
Surface ion source plasma ion source MiniMono
Courtesy Dr. H. Franberg
Sources Modes
ISCOOL transmission >70% for A>39:- In general between 70-80% for plasma targets, somewhat higher for surface ion sources. Depends on the emittance coming from the ion source
- In pulsed mode some higher losses related to the trapping time
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Beamline transmission
HRS
GPS Merging switchyardlosses 50-70%
ISCOOL
~35π.mm.mrad
~2π.mm.mrad
Higher mass spectroscopy
efficiency
100% transmission
Beamline transmission:- low emittance beam after the cooler is easily tuned to the different experiments with a transmission efficiency of up to 100%
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Bunch mode
ISCOOLin bunch mode
Collaps
HRS
Background suppression of factor ~1E4 by gating on the beam pulse
46K beam 1E5 ions/s after the cooler.Collection time 20 min, with 300ms bunching, 12us gate and 2mW laser power
Ernesto Mane: ‘First results using the ISCOOL-COLLAPS apparatus’
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Bunch mode
ISCOOLin bunch mode
REXtrap
HRS
ISCOOL gated by trap timing
(10 units = 20us)
20uS
New 'tricks' for REX injection:
- Mass purification at REXtrap using RF excitation. - Direct pulsed injection into EBIS without use of the trap: The space-charge of the RFQ bunches is much higher than what can be achieved with the trap. Acceptance of EBIS would be large enough and it would increase beam intensity to the linac.
Anna Gustafsson: ‘The REX low-energy toolbox’
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• 2008/9 shutdown consolidation:- vacuum controls (Julien de Freitas)
- new RF amplifier (Pascal Fernier)
- MCP re-installed?
2008/9 shutdown
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• Reliable 2008 performance with very few issues- RF amplifier will be replaced + spare- Vacuum will be integrated in the Isolde controls
• ISCOOL transmission 70-80% depending on mass and ion source
• Easy tuning and beamline transmission improved to 100%
• Bunch mode working well with future potential:- background suppression- mass purification at REX TRAP- direct injection in to REX EBIS
• Details in the 2008 ISCOOL performance report by Dr. H. Franberg, Dr. Pierre Delahaye, et al.
• ISCOOL webpage: http://ab-div-op-iso-rfqcb.web.cern.ch/
Summary
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• Special thanks to Hanna, Pierre and Tim • The Isolde OP-team, AB/OP-PSB-iso
AB/ATB, AB/VAC, AB/PO, AB/CO and Alexandre Dorsival (SC/RP) for making the ISCOOL 2008 run a success
Thanks