A 4-rod CW RFQ forprotons and deuterons
P. Fischer
Institute of Applied Physics (IAP)J.-W.-Goethe University
Max-von-Laue-Str. 1, 60438 Frankfurt, Germany
[email protected] / +49 69 798 47434
ENEN ITC 4, Mol SCK.CEN, May 2007 Philipp Fischer slide 2/29
Outline
• Soreq Nuclear Research Center• Accelerator Facility SARAF at Soreq NRC• Research and Applications• The SARAF RFQ Accelerator• Actual state
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Accelerators in Israel
University of Tel AvivWeizmann Institute:- Van-de-Graaff (3 MV)- Pelletron (14 MV)Soreq Nuclear Research Center:- Zyklotron (10 MeV)- Research Reactor IRR1 (5 MW)- Isorad Ltd.- SARAF
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SARAFSoreq Applied Research Accelerator Facility
RFQ 176 MHz M/q≤2
1.5 MeV/u
1. Kryostat6 SC HWR
176 MHz β0=0.09
2.-6. Kryostat40 SC HWR
176 MHz β0=0.15
EZR Ionenquelle20 keV/u 5 mA
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SARAFSoreq Applied Research Accelerator Facility
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ECR Ion Source
< 0.05 π mm mrad Norm. σ emittance ε(n x,y)
< 0.2 π mm mrad Norm. 2σ emittance ε(n x,y)
3%Deviation at minimum current
6%Deviation at maximum current
0.03 mA minimum beam current H+, H2+, D+
5 mA maximum beam current H+, H2+, D+
Value Parameter
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.
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RFQ-Accelerator
3.8 mRFQ length
176 MHz Frequency (RF)
≤ 2Mass / Charge M/q
20 / 1500 keV/u Injektion / Output energy
Picture of RFQ at Soreq NRC, September 2006
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)
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HWR-Modules
Acceleration by 46 HWR-Module (2 Modi) from 1,5 MeV/u to:
max. 40 MeV (Protons)
max. 20 MeV/u (Deuterons)
- Prototype Superconducting Module (PSM) consists of 6 HWR
- Half Wave Resonators (HWR) aresuperconducting (Niobium)
- based on λ/2-Resonators developed at INFN
- Tests of superconductivity and RF-properties at IAP / Frankfurt, 2004
PSM Modul 2 Modul 3 Modul 4 Modul 5 Modul 6
Lgap
Solenoid
HWR
Lacc
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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
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Synthesis of 6He (t1/2=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)6He9Be(d,xn) → 9Be(n,2n) → 9Be(n,α)6He
yield: 2.4 x 1013 atoms/s
Extraction of 6He-gas by a He-gasjet, extraktion of theinstable isotopes is possible with many losses, yield decreases down to 3 x 1011
Atome/s.
Yield calculations of D. Berkovits and M. Hass, 2006.
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0.90.510-4
Synthesis of a 14O- / 15O-beam
Synthesis of 14O (t1/2=70.6s)15O (t1/2=122.2s)
With a 40 MeV 2 mA d-beam and postacceleration of the radioactiveisotopes. Synthesis by:
14N(d2n)14O yield: 2-3 x 1012
14N(d,n)15O yield: 2-3 x 1013
14O Transmission
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Radioaktive Markers
Installation of a „Radiopharmacy“at Soreq NRC
Production of radioactive pharmaceutics for many imageing processes
Use of radioactive Fluor forPET-imageing to localize special activities
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SARAF-RFQ
100% (CW)Duty cycle
2.7max. modulation
DeuteriumIsotope
280 mmCavity‘s inner dia.
40number of stems
98 / 96 %transm. 0 / 5mA
65 kVElektrode voltage
3.8 mRFQ Length
2.7 mm min. apertur
250 kWPower consumption
0.85 / 0.28 mm mrad-1a / b
199number of cells
75 π deg. keV/ulong. output emit.
176 MHzFrequency (RF)
20 / 1500 keV/uInjektion / Output
35 kW
100-500 W
Power cons.
25%GSI (HLI)
10-3-10-4CERN, DESY, BNL
Duty cycle
Comparing duty cycle and power consumpt.:
5 mA
~ μA
100%SARAF
100%Tandem
Comaring beam current of CW-facilities:
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SARAF-RFQ
• RF-simulations• Thermo-mechanic simulations• Beam dynamics• Tuning of the resonant structure
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RF-simulations
61.9stems27.9Electrodes10.2Base platelosses %part
RF-simulations of the structurewith CST Microwave Studio (39 cells model):
• Frequency of resonance
• higher order modes
• Q value / power consumption
• surface currents / losses
• field distribution (→tuning)
Modes:
168.7 MHz (π-0)
178.5 MHz
187.6 MHz
…
∫ ∂= SHfP 2|| 21
σπμ
Loss calculation by themagnetic field:
Verluste:
Q-value (unloaded): 3153
Current density distribution of π-0-mode
conductivity σ=50 x 106 S/m
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RF-simulations (2)Adding some functionality to thesimulation model by a small tool:
• modulated electrodes
• closer to reality / more precise results
• handling of the longitudinal field distribution possible
90,00%
95,00%
100,00%
105,00%
110,00%
115,00%
120,00%
0 500 1000 1500 2000 2500 3000 3500
0,00%
50,00%
100,00%
150,00%
200,00%
250,00%
300,00%
350,00%
0 500 1000 1500 2000 2500 3000 3500
mm
mm
%
%
ohne Modulation
mit Modulation
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25.5421Bodenplatte (BP)
69.5134Elektroden (R)
46.51112Stütze Typ 2
108.52128Stütze Typ 1
Leistung [kW]Zahl der KühlkanäleKühlabschnitteAnzahlBauteile
KoaxialerBereich
direkterZufluß
Thermo-mechanic simulations
R1 R2 R3
BP1 BP2
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Thermo-mechanic simulations (2)Simulations were done with Ansys Multiphysics (@250kW)
• effect of water cooling
• localizing extreme temperatures
• mechanical deformations of the electrodes
A deforming of the electrodes (total length) →effect to the frequency of resonance:
1.1 MHz / 0.1 mm
Compensation by tunerplungers: +/- 400 kHz
(100-fach überzeichnet)
Surface temperature deforming
Ansys results:
• max. temp. 80°C
• water temperaturerises 2.5 °C (at a flow of 20 l/min)
• max. deforming: 152 μm
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Beam dynamicsPartice 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!
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Tuning of the resonant structurevoltage distribution
• coupled resonators• Each has ist own resonancy• Operation with one / the same frequency• Excitation of other modes → non-constant voltage distribution at CEI
CE
L
Overhanging ends
0-Mode 1/5-π-Mode
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Tuning of the resonant structure Tuning plates
CE
L
tuningplate
0,5
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
1,5
0 500 1000 1500 2000 2500 3000 3500
plate
tuned field
untuned field distribution
-0,5
-0,4
-0,3
-0,2
-0,1
0
0,1
0,2
0,3
0,4
0,5
0 500 1000 1500 2000 2500 3000 3500
effect curve
plate( ))(1)()()( zzECzUFzUF UT +×=
• 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:
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Tuning of the resonant structure Tuning plates (2)
-0,8
-0,6
-0,4
-0,2
0
0,2
0,4
0,6
0 500 1000 1500 2000 2500 3000 3500
5 mm
10 mm
20 mm
30 mm
40 mm
50 mm
-0,2
-0,15
-0,1
-0,05
0
0,05
0,1
0,15
0,2
0 500 1000 1500 2000 2500 3000 3500
1
3
5
7
9
11
13
15
17
19
different height plate in different cells
( ))(1)()(),( zzEChzUFhzUF kUkT +⋅×=
Field distribution UFTk with one single tuning plate in cell no. k:
( )∏=
+⋅×=n
kkkUT zzEChzUFhnzUF
1
)(1)()(),,(
Combination of multiple tuning plates can be calculated via superposition:
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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)
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
1,4
0 5 10 15 20 25 30 35 400,0010,0020,0030,0040,0050,0060,0070,0080,0090,00100,00
Tuning Plates Height [mm] Normalized RF Field
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SARAF-RFQmechanical adjustment
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The SARAF-RFQ at the IAP after set-up, adjusting and RF-Tuning, Juli 2005.
SARAF-RFQfinishing at the IAP / Frankfurt
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Conditioning / actual stateMeasured 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
pick-up tranmission
reflexion at coupler
plunger’s effect
dev. electrode voltage
next mode
resonance
em-Energy
approx. power @ 65 kV
Rp x length
Q-value (unloaded)
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CW-problems / conditioning
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melted
SARAF-plungersimulation model (MWS) of the tuner plunger
New plunger with smaller diameter
New plunger:diamter Ø=50 mmFrequency of resonance210 - 260 MHz“far away” from the operation frequency of RFQ (176 MHz)
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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