A 4-rod CW RFQ for
protons and deuterons
P. Fischer
Institute of Applied Physics (IAP)
J.-W.-Goethe University
Max-von-Laue-Str. 1, 60438 Frankfurt, Germany
P.Fischer@iap.uni-frankfurt.de / +49 69 798 47434
Outline
•
•
•
•
•
Soreq Nuclear Research Center
Accelerator Facility SARAF at Soreq NRC
Research and Applications
The SARAF RFQ Accelerator
Actual state
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
slide 2/29
Accelerators in Israel
University of Tel Aviv
Weizmann Institute:
- Van-de-Graaff (3 MV)
- Pelletron (14 MV)
Soreq Nuclear Research Center:
- Zyklotron (10 MeV)
- Research Reactor IRR1 (5 MW)
- Isorad Ltd.
- SARAF
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
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SARAF
Soreq Applied Research Accelerator Facility
2.-6. Kryostat
40 SC HWR
176 MHz β0=0.15
1. Kryostat
6 SC HWR
176 MHz β0=0.09
RFQ
176 MHz M/q≤2
1.5 MeV/u
EZR Ionenquelle
20 keV/u 5 mA
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Philipp Fischer
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SARAF
Soreq Applied Research Accelerator Facility
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Philipp Fischer
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ECR Ion Source
Parameter
Value
maximum beam current H+, H2+, D+
5 mA
minimum beam current H+, H2+, D+
0.03 mA
Deviation at maximum current
6%
Deviation at minimum current
3%
Norm. 2σ emittance ε(n x,y)
< 0.2 π mm mrad
Norm. σ emittance ε(n x,y)
< 0.05 π mm mrad
Taylor, T. und J.F. Mouris:
“An advanced high-current
low-emittance DC
microwave proton source”,
Nuclear Instruments and
Methods, vol. A 336, p. 1-5,
1993.
AECL Research, Canada.
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
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RFQ-Accelerator
Injektion / Output energy
20 / 1500 keV/u
Mass / Charge M/q
≤2
Frequency (RF)
176 MHz
RFQ length
3.8 m
4-rod-RFQ for CW-Operation
250 kW power consumption
Operates „on switch“ in two modes:
• M/q = 2 (Deuterons) and
• M/q = 1 (Protons)
Picture of RFQ at Soreq NRC, September 2006
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
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HWR-Modules
PSM
Modul 2
Modul 3
Modul 4
Modul 5
Modul 6
- Prototype Superconducting Module
(PSM) consists of 6 HWR
- Half Wave Resonators (HWR) are
superconducting (Niobium)
- based on λ/2-Resonators developed at
INFN
HWR
Lacc
Lgap
- Tests of superconductivity and RFproperties at IAP / Frankfurt, 2004
Solenoid
Acceleration by 46 HWR-Module (2 Modi)
from 1,5 MeV/u to:
max. 40 MeV (Protons)
max. 20 MeV/u (Deuterons)
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Philipp Fischer
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Research and Applications
Multiple use of the beam from basic
research to industrial applications
- Research on RIBs (rare isotope beams)
- 6He synthesis from 2-stage reaction
- 14O and 15O synthesis
- Production of radiopharmaceutics
- markers for PET
- radiotherapy
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
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Synthesis of 6He (t
1/2=807
ms)
Synthesis of 6He with a 40 MeV 2 mA p/d-beam,
one-stage reaction:
7Li(p,2p)6He
yield: 0.05 x 1013 atoms/s
two- / more-stage reaction:
9Be(d,xn)
→ 9Be(n,α)6He
9Be(d,xn)
→ 9Be(n,2n) → 9Be(n,α)6He
yield: 2.4 x 1013 atoms/s
Extraction of 6He-gas by a Hegasjet, extraktion of the
instable isotopes is possible
with many losses, yield
decreases down to 3 x 1011
Atome/s.
Yield calculations of D.
Berkovits and M. Hass, 2006.
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
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Synthesis of a 14O- / 15O-beam
14O
Transmission
0.9
0.5
10-4
Synthesis of
14O
(t1/2=70.6s)
15O
(t1/2=122.2s)
With a 40 MeV 2 mA d-beam and
postacceleration of the radioactive
isotopes. Synthesis by:
14N(d2n)14O
yield: 2-3 x 1012
14N(d,n)15O
yield: 2-3 x 1013
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
slide 11/29
Radioaktive Markers
Use of radioactive Fluor for
PET-imageing to localize
special activities
Installation of a „Radiopharmacy“
at Soreq NRC
Production of radioactive
pharmaceutics for many imageing
processes
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
slide 12/29
SARAF-RFQ
Comparing duty cycle and power consumpt.:
Injektion / Output
20 / 1500 keV/u
Isotope
Deuterium
Frequency (RF)
176 MHz
Elektrode voltage
65 kV
RFQ Length
3.8 m
Cavity‘s inner dia.
280 mm
min. apertur
2.7 mm
max. modulation
2.7
Duty cycle
100%
Power consumption
250 kW
a/b
0.85 / 0.28 mm mrad-1
number of cells
199
number of stems
40
long. output emit.
75 π deg. keV/u
transm. 0 / 5mA
98 / 96 %
ENEN ITC 4, Mol SCK.CEN, May 2007
Duty cycle
Power cons.
CERN, DESY, BNL
10-3-10-4
100-500 W
GSI (HLI)
25%
35 kW
Comaring beam current of CW-facilities:
Tandem
100%
~ μA
SARAF
100%
5 mA
(CW)
Philipp Fischer
slide 13/29
SARAF-RFQ
•
•
•
•
RF-simulations
Thermo-mechanic simulations
Beam dynamics
Tuning of the resonant structure
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
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RF-simulations
RF-simulations of the structure
with CST Microwave Studio (39
cells model):
Q-value (unloaded):
3153
• Frequency of resonance
• higher order modes
• Q value / power consumption
• surface currents / losses
• field distribution (→tuning)
Current density distribution of π-0-mode
Modes:
168.7 MHz (π-0)
Verluste:
Loss calculation by the
magnetic field:
part
losses %
Base plate
10.2
187.6 MHz
Electrodes
27.9
P=
…
stems
61.9
conductivity σ=50 x 106 S/m
178.5 MHz
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
1 πμ f
σ
2
2
|
H
|
∂S
∫
slide 15/29
RF-simulations (2)
Adding some functionality to the
simulation model by a small tool:
• modulated electrodes
• closer to reality / more precise
results
• handling of the longitudinal
field distribution possible
120,00%
%
ohne Modulation
115,00%
110,00%
105,00%
100,00%
95,00%
90,00%
0
500
1000
1500
2000
2500
3000
3500
%
mm
350,00%
300,00%
mit Modulation
250,00%
200,00%
150,00%
100,00%
50,00%
0,00%
0
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
500
1000
1500
2000
2500
3000
3500
mm
slide 16/29
Thermo-mechanic simulations
R1
R2
R3
BP1
BP2
Anzahl
Bauteile
Kühlabschnitte
Zahl der Kühlkanäle
Leistung [kW]
Stütze Typ 1
28
1
2
108.5
Stütze Typ 2
12
Koaxialer
Bereich Elektroden
(R)
Bodenplatte (BP)
1
1
46.5
4
direkter
Zufluß 3
1
69.5
1
2
4
25.5
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
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Thermo-mechanic simulations (2)
A deforming of the
electrodes (total length) →
effect to the frequency of
resonance:
Simulations were done with
Ansys Multiphysics (@250kW)
• effect of water cooling
• localizing extreme
temperatures
1.1 MHz / 0.1 mm
Compensation by tuner
plungers: +/- 400 kHz
• mechanical deformations of
the electrodes
Ansys results:
• max. temp. 80°C
• water temperature
rises 2.5 °C (at a flow of
20 l/min)
(100-fach
überzeichnet)
• max. deforming:
152 μm
Surface temperature
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
deforming
slide 18/29
Beam dynamics
Partice losses are caused by unsufficient
quadrupole field strength
→ unsufficient compensation of space
charge
Quadrupole field strength is mainly given
by the electrode voltage
Unflat voltage distribution has the effect
of a „bottle-neck“:
Transmission is limited by the weakest
field (Texample=85%)
Compensation by rising the elect. voltage:
• more power needed
• bigger amplifier
• additional power needs additional cooling!
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
slide 19/29
Tuning of the resonant structure
voltage distribution
CE
L
I
•
•
•
•
→
coupled resonators
Each has ist own resonancy
Operation with one / the same frequency
Excitation of other modes
non-constant voltage distribution at CE
Overhanging ends
0-Mode
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
1/5-π-Mode
slide 20/29
Tuning of the resonant structure
Tuning plates
1,5
1,4
CE
tuned field
1,3
untuned field distribution
1,2
1,1
L
1
0,9
0,8
tuning
plate
0,7
0,6
plate
0,5
0
500
1000
1500
2000
2500
3000
3500
2500
3000
3500
0,5
• resonance of a single cell is a function of
the inductance L
• variable L by variing the plate‘s height
• plate acts as a short cut
• from the voltage distribution with and
without tuning plate, the effect curve can be
obtained:
UFT ( z ) = UFU ( z ) × (EC ( z ) + 1( z ) )
ENEN ITC 4, Mol SCK.CEN, May 2007
0,4
0,3
0,2
effect curve
0,1
0
-0,1 0
500
1000
1500
2000
-0,2
-0,3
-0,4
plate
-0,5
Philipp Fischer
slide 21/29
Tuning of the resonant structure
Tuning plates (2)
0,6
0,2
0,4
0,15
0,1
0,2
0,05
0
5 mm
10 mm
20 mm
30 mm
40 mm
50 mm
-0,2
-0,4
-0,6
-0,8
0
1
3
5
7
9
11
13
15
17
19
-0,05
-0,1
-0,15
-0,2
0
500
1000
1500
2000
2500
3000
different height
Field distribution UFTk with one
single tuning plate in cell no. k:
UFT k ( z , h) = UFU ( z ) × (h ⋅ ECk ( z ) + 1( z ) )
ENEN ITC 4, Mol SCK.CEN, May 2007
3500
0
500
1000
1500
2000
2500
3000
3500
plate in different cells
Combination of multiple tuning plates can
be calculated via superposition:
n
UFT ( z , n, h) = UFU ( z ) × ∏ (hk ⋅ ECk ( z ) + 1( z ) )
k =1
Philipp Fischer
slide 22/29
Tuning of the resonant structure
Tuning the SARAF-RFQ
• calculating the superposition with a small
computer tool
• use of data from simulations (MWS)
• use of measured values
Final RF tuning / Tuning plate position along the RFQ
(40=beam input, 0=output)
1,4
100,00
1,3
90,00
80,00
1,2
70,00
1,1
60,00
1
50,00
0,9
40,00
30,00
0,8
20,00
0,7
10,00
0,00
0,6
0
5
10
15
20
Tuning Plates Height [mm]
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
25
30
35
40
Normalized RF Field
slide 23/29
SARAF-RFQ
mechanical adjustment
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Philipp Fischer
slide 24/29
SARAF-RFQ
finishing at the IAP / Frankfurt
The SARAF-RFQ at the IAP after set-up,
adjusting and RF-Tuning, Juli 2005.
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
slide 25/29
Conditioning / actual state
Q-value (unloaded)
Rp x length
approx. power @ 65 kV
em-Energy
resonance
next mode
dev. electrode voltage
Measured values (left) of the SARAF-RFQ at
IAP, Juli 2005
actual state:
• conditioning in puls operation finished
(180 kW at 4% duty cycle) 11-2006
• conditioning in CW operation finished
(180 kW at 100% duty cycle) 04-2007
plunger’s effect
reflexion at coupler
pick-up tranmission
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Philipp Fischer
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CW-problems / conditioning
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
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SARAF-plunger
simulation model (MWS) of the tuner plunger
New plunger with smaller diameter
New plunger:
diamter Ø=50 mm
Frequency of resonance
210 - 260 MHz
“far away” from the
operation frequency of
RFQ (176 MHz)
melted
ENEN ITC 4, Mol SCK.CEN, May 2007
Philipp Fischer
slide 28/29
Conclusions
• design of a 4-rod-RFQ for CW-operation as
injector for SARAF
• acceleration of D+ to 3 MeV on 3.8 m length,
176 MHz 250 kW
• set-up, adjusting and RF-Tuning at IAP
• conditioning and installation at Soreq NRC /
Israel
• beam tests 2007
• set-up of the cryostates 2 – 6
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Philipp Fischer
slide 29/29