Extraction efficiency and extraction times Extraction efficiency and extraction times of the SHIPTRAP gas stopping cellof the SHIPTRAP gas stopping cell

Gleb Vorobjev

for SHIPTRAP collaboration, GSI

SMI, 27. March 2006

2

OutlineOutline

Introduction:

Off-line experimental set-upInvestigation of the gas cell:

Summary

SHIPTRAP set-upSHIPTRAP gas stopping cell

Extraction timesExtraction efficienciesTotal efficiency ImpuritiesOn-line beam

3

Set-up layoutSet-up layout

PurificationTrap

MeasurementTrap

Detector

ExtractionRFQ

StoppingCell

fusion productsfrom SHIP

Buncher

1 2

4

56Purification

Trap

MeasurementTrap

Detector

ExtractionRFQ

StoppingCell

fusion productsfrom SHIP

Buncher

PurificationTrap

MeasurementTrap

Detector

ExtractionRFQ

StoppingCell

fusion productsfrom SHIP

Buncher

Nout/Nin= ?

50%

100%

100% 30%NNinin

NNoutout

4

ExtractionRFQ(18 cm)

Nozzle 0.6 mm

Electrode (DC)

Entrance Window (60 mm)58 cm

25 cm

Funnel (RF + DC)

Buncher

Lens

SHIPTRAP @ Munich

J.Neumayr; PhD-thesis

5

Experimental set-upExperimental set-up

Extraction RFQ

Lens

RF-DC FunnelDC CageMovable feedthrough

223Ra-ion source

Nozzle

Si-detector orOrtho-TOF MS

d 0

0 r

30 cm

9 cm

9 cm

215Po1.8 m s

223Ra11.4 d

219Rn3.9 s

211Pb

211Bi2.1m in

207TI4.7m in

207Pb

~ 10 d e c a ys/s4

Features of 223Ra source: • T1/2(223Ra)=11.4 d• max. activity ~10,000 decays/s • available recoil ions

219Rn+, (215Po+), 211Pb+, 207Tl+

• characteristic -decay for identification• point-like• determine (absolute) extraction efficiency

6

Experimental set-upExperimental set-up

Extraction RFQ

Lens

RF-DC FunnelDC CageMovable feedthrough

Nozzle

Si-detector orOrtho-TOF MS

d 0

0 r

30 cm

9 cm

9 cm

7

Extraction timeExtraction time

3 4 5 6 7 8 9 10 11 12 13 14 15 160

1

2

3

4

5

6

7

8

9

10

11

Ext

ract

ion

tim

e o

f 21

9 Rn

, m

s

axial position,cm (r=0)

PHe = 40 mbar

Axial E-field = 5 V/cm

linear trend described by mobility formalism

PHe : (40-100) mbar

Axial E-field 10 V/cm

Nuclides with T1/2>10 ms accessible at SHIPTRAP

ext

axd t

d

P

PKEKE 0

0

8

Extraction efficiencyExtraction efficiency

2 4 6 8 10 12 14 16 18 20 22 240,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

0 1 2 3 4 5 6 7

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

axial position,cm (r=0)

nu

mb

er

of

ion

s n

orm

aliz

ed

to

ma

xim

um

Helium pressure in the cell (10 V/cm): 40 mbar 65 mbar 90 mbar

radial position,cm (d=16cm)

Main losses are due to diffusion

Neutralisation < extraction time40 50 60 70 80 90 100

12

14

16

18

20

22

24

26

28

30

32

ext

ract

ion

eff

icie

ncy

, %

helium pressure, mbar

RF-funnel is less efficient

9

Stopping efficiencyStopping efficiency

76 78 80 82 84 86 88 90 92 9410

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

Sto

pp

ing

effi

cie

ncy

, %

Energy of the recoils, MeV

40 mbar 7 Ti 50 mbar 7 Ti 60 mbar 6.8 Ti 70 mbar 6.6 Ti 80 mbar 6.4 Ti 90 mbar 6.2 Ti

0 4 8 12 16 20 24 280

5

10

15

20

25

30

Co

un

ts

Stopping range of the ions in the gas-cell, cm

86 MeV 148Ho-recoils6.4 m Ti @ 80 mbar He

ions incide the cage

10

40 50 60 70 80 9035

40

45

50

55

60

65

70

75

80

Sto

pp

ing

eff

icie

ncy

, %

helium pressure, mbar

SRIM 2003 calculations

148HoE: 77 - 94 MeV

Total efficiencyTotal efficiency

40 50 60 70 80 90 100

12

14

16

18

20

22

24

26

28

30

32

ext

ract

ion

eff

icie

ncy

, %

helium pressure, mbar

measurement

40 50 60 70 80 90 100

2

4

6

8

10

12

14

16

18

tota

l effi

cien

cy, %

helium pressure, mbar

11

Total efficiency (measured on-line)Total efficiency (measured on-line)

place test candidate efficiency extraction fields

DC / funnel

extraction

angle

MLL 152Er

-emitter

8.4 % ± 1.5 % 10 V/cm 10 V/cm 0o

GSI 152Er

-emitter

4.8 % ± 0.7 % 10 V/cm 5 V/cm 90o

MLL 107Ag+

atomic ions

4.0 % ± 1.0 % 5 V/cm 10 V/cm 0o

Measured total efficiencies 4-8%

12

Influence of contaminants Influence of contaminants

100 120 140 160 180 200 220 240

101

102

103

104

Ab

un

da

nce

Mass / u

190 200 210 2200

20

40

60

Ab

un

da

nce

Mass / u

Xe+

100 120 140 160 180 200 220 240

101

102

103

104

Abu

ndan

ce

Mass / u

190 200 210 2200

500

1000

1500

Abu

ndan

ce

Mass / u

219Rn+

219Rn+

215Po+

211 P

b+ +

211 B

i+

207T

l+ +

207P

b+

Er+

Xe+

2112+

Before bake-out

After bake-out (24 hours, 1500)

13

On-line regimeOn-line regime

PurificationTrap

MeasurementTrap

Detector

ExtractionRFQ

StoppingCell

fusion productsfrom SHIP

Buncher

1 2

4

56Purification

Trap

MeasurementTrap

Detector

ExtractionRFQ

StoppingCell

fusion productsfrom SHIP

Buncher

PurificationTrap

MeasurementTrap

Detector

ExtractionRFQ

StoppingCell

fusion productsfrom SHIP

Buncher

0 50 100 150 200 250 300 3500

200

400

600

800

A2+

A~145-150

arbi

trary

units

Mass, u

219Rn+

TOF, 2m

58Ni + 92Mo -> 150Yb* 50Cr + 58Ni -> 108Te*

0 50 100 150 200 250 300 350 4000

40

80

120

160

200

240

280

320

360

400

440

Co

un

ts

Atomic number

Xe

Kr

A ~ 96

time-of-flight spectra

dipole cleaning on

14

ConclusionsConclusions

Gas cell is fast: nuclides with T1/2>10 ms are accessible

Extraction efficiency ~ 20 % at 40 mbar

Total efficiency ~ 13 % in the range of 70-80 mbar

Diffusion is crucial: higher pressure, stronger axial field needed

Neutralisation is slower than extraction

Scattered primary beam is not allowed to enter the gas cell

15

SHIPTRAP collaborationSHIPTRAP collaboration

GSI / SHIPTRAP

D. Ackermann

M. Block

D. Beck

M. Dworschak

S. Eliseev

F. Herfurth

F. P. Heßberger

S. Hofmann

H.-J. Kluge

A. Martín

M. Mazzocco

W. Quint

C. Rauth

G. Vorobjev

Greifswald

A. Chaudhuri

G. Marx

L. Schweikhard

Mainz

K. Blaum

R. Ferrer

C. Weber

H. Backe

P. Kunz

W. Lauth

Giessen

Z. Di

H. Geissel

C. Scheidenberger

M. Petrick

W. Plaß

Munich

D. Habs

V. Kolhinen

J. Neumayr

M. Sewtz

P. Thirolf

Former PhD students: G. Sikler, D. Rodríguez, M. Mukherjee, S.

Rahaman, ...

St. Petersburg

Y. Novikov