A 4-rod CW RFQ for protons and deuterons · A 4-rod CW RFQ for protons and deuterons P. Fischer ... SARAF-RFQ Duty cycle 100% ... Ansys Multiphysics (@250kW)

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


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


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


SARAFSoreq Applied Research Accelerator Facility


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.


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)


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


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


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.


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


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


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:


SARAF-RFQ

• RF-simulations• Thermo-mechanic simulations• Beam dynamics• Tuning of the resonant structure


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


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


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


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


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!


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


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:


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:


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


SARAF-RFQmechanical adjustment


The SARAF-RFQ at the IAP after set-up, adjusting and RF-Tuning, Juli 2005.

SARAF-RFQfinishing at the IAP / Frankfurt


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)


CW-problems / conditioning


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)


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

Documents

A 4-rod CW RFQ for protons and deuterons · A 4-rod CW RFQ for protons and deuterons P. Fischer ... SARAF-RFQ Duty cycle 100% ... Ansys Multiphysics (@250kW)