The Design Study of Superconducting Magnet System for a Advanced ECR Ion Source

*E-mail : bslee@kbsi.re.kr

ByoungSeob Lee*, MiSook Won*, JinYong Park*, DongJun Park*, JongPil Kim*, JangHee Yoon*, JongSeong Bae*, JungKeun Ahn*** Korea Basic Science Institute - Busan Center, **Pusan National University

Abstract

The Korea Basic Science Institute is developing a superconducting magnet

system for 28 GHz Electron Cyclotron Resonance Ion Source (ECRIS). We are

investigating in order to realize compact size, economic operation and generation

of high current beam. Although companies and researchers have valuable

experience, skill and ability in designing of superconducting magnet for ECRIS,

they did not exactly proposed a excellent superconducting magnet system for

ECRIS because many superconducting magnets were not required. Of course

they do if we required many magnets for the various application of ECRIS. In

this presentation, we have filed reports of former researcher and we have

discussed the realization of ECRIS over 35 GHz.

Chamber Diameter 150mmlength 500mm

Binj~4T,Bmin~0~1T,Bext~2TRF28GHz(10kWmax)

Chamber Diameter 126mmlength 1000mm

Binj~3.7T, Bext~2.2TRF28GHz(10kWmax)

Lanzhou (China)

Chamber Diameter 150mmlength 500mm

Binj~3.5T, Bmin~0.8T Bext~2TRF28GHz(10kWmax)

RIKEN RIBF (Japan)

FRIB (USA)

VENUS

SC-ECR

SECRAL

Chamber Diameter 180mmlength 650mm

Binj~4.5T,Bext~3.2TRF28GHz(10kWmax)

MS-ECRIS

INFN-LNS (Italy)

KBSI-Busan Center (Korea)

28 GHz ECRIS in The World

Chamber Diameter 150mmlength 500mm

Binj~3.5T,Bmin~0.4~0.8T,Bext~2TRF28GHz(10kWmax)

Large ECR Zone

Low X-ray Heat Load

Critical Problems of ECRIS Magnet

v X-ray Irradiation§ Large Heat Source of Magnet§ Degradation, Erosion

v Critical Current & Field of Superconducting Wire§ HTS Wire§ Nb3Sn LTS Wire§ Hybrid Magnet

v Reinforcement of Structural Strength for Hexapole Magnet§ Liquid Metal§ Special Structure

v Cooling Method§ Recondensed Cooling Method ;

Low Temperature§ Conduction Cooled Method ;

Simple

36GHz ECRIS

Required magnetic field strength

Binj ~5TBr ~2.7TBext ~2.7TBmin 0.8~1.2T

From material of Talks with Dr. Nakagawa

KBSI 28 GHz ECR Ion SourceBmin ; 0.4 ~ 0.8 × Becr T

Rev. Sci. Instrum. 79(2008)033302 D. Leitner et al,

0.55 Tesla

Heat Load & X-ray irradiation

TrapCAD simulation for electrons Calculation X-ray Energy

WWPP SUSAl

correctedSUSAl5

8

13

8,

1,, 1076.11016.1

1004.21016.1

--

-

- ´=´´

=´

=

2620mm

1,,

,872

2

1016.11063.8

1)2620(4

1

correctedSUSAl

SUSAl

PP

mmmm

=´=´

= -

p

Collimator block ; 1 mm2

(Leitner, 2008)

Ref. : First Results for the 28GHz Operation of the superconducting ECRIS VENUS (Leitner, 2004)

0 100 200 300 400 500 600

2.0x104

4.0x104

6.0x104

8.0x104

1.0x105

I (c

ounts

/600 s

eco

nds)

Photon Energy (keV)Energy (keV)

VENUS 28GHz ECRIS Bremsstrahlung Energy Rate

No attenuation

9.6 mm Aluminum4.8 mm Stainless Steel

9.6 mm Aluminum4.8 mm Stainless Steel1.0 mm Tungsten

Energy rate, PAl,SUS = 766000 keV/600s = 1277 keV/s= 1.277 x 106 eV/s= 2.04 x 10-13 J/s= 2.04 x 10-13 W

(∵ 1.6 x 10-19 J = 1 eV)

Bremsstrahlung heating rate = 2W

(Leitner, 2006)

140 mm

500 mm

17 mm 14 mm

Total surface area of plasma chamber:π(702-42)+π(702-7.52)+2π·70·500 = 250,470 (mm2)

Active surface area for bremsstrahlung: π(72-42) = 104 (mm2)

Active surface ratio:2,1,,

1,,41015.4250470

104

correctedcorrectedSUSAl

correctedSUSAl

PP

=´= -

WWPP correctedSUSAl

correctedcorrectedSUSAl2

4

5

41,,

2,1,, 1024.41015.4

1076.11015.4

--

-

- ´=´´

=´

=

0.2 deg

2. X-Ray Energy Rate from Bremsstrahlung spectrum of VENUS

1) Energy rate, PAl,SUS = 766000 keV/600s = 2.04 x 10-13 W2) Energy rate corrected by solid angle

3) Energy rate corrected by solid angle and surface area

WWPP correctedSUSAl

correctedcorrectedSUSAl2

4

5

41,,

2,1,, 1024.41015.4

1076.11015.4

--

-

- ´=´´

=´

=

1. Bremsstrahlung heating rate = 2W

%21022

1024.4 22

=´=´ -

-

3. Energy rate difference

WWPP SUSAl

correctedSUSAl5

8

13

8,

1,, 1076.11016.1

1004.21016.1

--

-

- ´=´´

=´

=

0 100 200 300 400 500 600 70010-2

10-1

100

101

102

103

104

105

10-2

10-1

100

101

102

103

104

105

I (co

unts

/600

sec

onds

)

Photon Energy (keV)

m/r

(cm

2 /g)

Al 2mmWater 2mmAl 2mmTa ?mm

X-ray

xo

meII m-=

Absorption equation

xoeI

)/( rm-=

water

Al

Ta

I0IAl,water,Al

IAl,water,Al, Ta 1mmIAl,water,Al, Ta 2mm

IAl,water,Al, Ta 3mm

Reducing factor

IIRF 0=

1.162683396663850

,, ==AlwaterAlRF

5.224934796268339

1, ==mmTaRF

5.413960186268339

2, ==mmTaRF

1.78797066268339

3, ==mmTaRF

Calculation Concept of X-ray ShieldCalculation Concept of X-ray Shield

Energy (keV)

Experimental data Theoretical data

No attenuation

9.6 mm Aluminum4.8 mm Stainless Steel

9.6 mm Aluminum4.8 mm Stainless Steel1.0 mm Tungsten

Reducing factor of W1mm = 4.5 Reducing factor of W1mm = 2.2

,9.135460316663580

, ==SUSAlRF 2.216216333546031

,, ==WSUSAlRF

0 100 200 300 400 500 600100

101

102

103

104

105

I (c

ounts

/600 s

eco

nds)

Photon Energy (keV)

Calculating the Thickness of X-ray shielding material for KBSI 28GHz ECRIS

1. When Bmin/Becr = 0.45 or 0.5,1) Bremsstrahlung heating from VENIUS data of Fig. 5 in Leitner et al. (2004)

~ 1W/kW of 28GHz rf at no attenuation~ 6W/6kW of 28GHz rf at no attenuation

2) Using 2-mm-thick Ta tube, reducing factor for x-ray, RF ~ 4.53) With 2-mm-thick Ta tube, the final bremsstrahlung heating

~ 0.2W/kW of 28GHz rf~ 1.3W/6kW of 28GHz rf

4) The limit of heat loading by bremsstrahlung for KBSI 28GHz ECRIS, ~ 3W5) Therefore, 2-mm-thick Ta tube is O.K. in operating 6kW of 28GHz rf.

2. When Bmin/Becr = 0.64,

1) Bremsstrahlung heating from VENIUS data of Fig. 11 in Leitner et al. (2008)~ 10W/kW of 28GHz rf at no attenuation~ 60W/6kW of 28GHz rf at no attenuation

2) Using 6.5/5.4-mm-thick Ta/W tube, reducing factor for x-ray, RFTa/W ~ 19Using 4-mm-thick Al tube, 2-mm-thick water and 6.5/5.4-mm-thick Ta/W tube,total reducing factor for x-ray, RFAl,water,Ta/W ~ 20

3) With 6.5/5.4-mm-thick Ta/W tube in our system, the final bremsstrahlung heating~ 0.5W/kW of 28GHz rf~ 3W/6kW of 28GHz rf

4) The limit of heat loading by bremsstrahlung for KBSI 28GHz ECRIS, ~ 3W5) Therefore, we need 6.5 or 5.4-mm-thick Ta or W tube in operating 6kW of 28GHz rf.

Theoretical data with W

No attenuation

4 mm Aluminum2 mm water

4 mm Aluminum2 mm water2 mm Tungsten

Reducing factor of W5.4mm = 18.9

,1.162683396663850

, ==waterAlRF 9.18332311

62683394.5, ==mmWRF

4 mm Aluminum2 mm water5.4 mm Tungsten

Theoretical data with Ta

No attenuation

4 mm Aluminum2 mm water

4 mm Aluminum2 mm water2 mm Tantalum

Reducing factor of Ta6.5mm = 19

,1.162683396663850

, ==waterAlRF 193302786268339

5.6, ==mmTaRF

4 mm Aluminum2 mm water6.5 mm Tantalum

0 100 200 300 400 500 600100

101

102

103

104

105

I (co

unts

/600 s

eco

nds)

Photon Energy (keV)0 100 200 300 400 500 600

100

101

102

103

104

105

I (co

unts

/600 s

eco

nds)

Photon Energy (keV)

LHe no Boil off Cryostat

Spec. Unit ValueWeight of Cryostat(without iron york) kg <1500

Vacuum Rate of Cryostat torr <~9x10-5He Leak Rate of Cryostat cc.atm/sec <~9x1-09

Volume of LHe Vessel liter <950

Cooler Capacity (4ea) First Stage (50K) W 200Second Stage (4.2K) W 6

Number of 4.2K Cooler Port ea 4Number of HTS 500A Current Lead pair 4

Shield Radiation 35Current Lead (4pair)

Conduction 80

Access Port Conduction 5Access Port Radiation 3

Support (8ea)Conduction 3

Total Heat Loss of Thermal Shield < 126 W

LHe Vessel Radiation 0.3HTS Current Lead(4pair) Conduction 0.5

Access Port Conduction 0.4Access Port Radiation 0.2

Support (8ea)Conduction 0.2

X-ray Heating 3 WTotal Heat at Loss of

LHe Vessel < 4.6 W

Reinforced Hexapole Coil Structure

ECR Ion SourceControl System

2.45 GHz ECR Ion Source

X-ray &Beam CurrentMeasurementSystem

ExchangeableECR Ion Source Chamber

X-rayDetector System

Prototype ECR Ion Source System

ECR plasma marks in Plasma chamber

Energy calibration

133Ba

137Cs

60Co

-80 -60 -40 -20 0 20 40 60 80 100

-14

-13

-12

-11

-10

-9

-8

-7

Iprobe-Isat

Te

esat

ModelNewFunction4 (User)

Equation y =m*x + b

Reduced Chi-Sqr

0.04769

Adj. R-Square 0.80732Value Standard Err

D m 0.11069 0.01173D b -9.7069 0.04656

ModelNewFunction4 (User)

Equation y =m*x + b

Reduced Chi-Sqr

1.30947E-5

Adj. R-Squa 0.99881Value Standard Er

D m 0.0116 2.84309E-4

D b -7.972 0.02024

curre

nt (l

nA)

voltage(V)

Electron Temperature = 9.09eV.

ECR Plasma Density 1.235*1011Cm-3

- Langmuir system & experimentation of Prototype

SIMS Depth Profiling of Ar implanted Si

0 50 100 150 200 2501018

1019

1020

1021

1022

1x1023 Ar

Conc

entra

tion(

atom

s/cc

)

Sputter Depth(nm)

100

101

102

103

104

105

106

107 Si O

In

tens

ity(c

ount

s/se

c)

0 50 100 150 200 2501018

1019

1020

1021

1022

1x1023 Ar

Conc

entra

tion(

atom

s/cc

)

Sputter Depth(nm)

100

101

102

103

104

105

106

107 Si O

In

tens

ity(c

ount

s/se

c)

Fig.1 Depth Profile of #0.5kV Sample Fig.2 Depth Profile of #1.5kV Sample

- Implantation of Ar in B-doped SiO2/Si silicon wafer

- The main heat load of superconducting magnet system for ECR ions source

generated by x-ray irradiation.

- The estimation method of x-ray was presented.

- The x-ray heat load for 28GHz ECR ion source was estimated.

- The heat load of magnet system was calculated and The conceptual cooling

system was designed.

- Also, we were trying the study about reinforced structural system and some

basic experiments were performed.

Concluding Remark

MOPOT15