Cryogenic ion catchers using superfluid helium and noble gases Sivaji Purushothaman KVI, University of Groningen The Netherlands.

Cryogenic ion catchers using superfluid helium

and noble gases

Sivaji Purushothaman

KVI, University of Groningen

The Netherlands

Content

• Introduction

• Superfluid Helium

• Cryogenic gas catchers• Off-line • On-line

• Summary

• Future plans

(mg/cm3) (rel.)T (K)

1 bar He

gas

1 bar He gas

1 bar He gas

liquid He

superfluid He

et

Impurities get frozen out !!!

High density at low temperature

(mg/cm3) (rel.)T (K)

1-2 Kliquid

vapour

room Tvacuum

Cold RIBs from superfluid helium: concept

1. stop high-energy radioactive ions in superfluid helium

snowballs

2. transport to the surface by electric fields

3. extraction across the surface into the vapour regionel

ectr

odes

4. transport to a vacuum, room-temperature regiontri

vial

3. extraction across the surface into the vapour region

N. Takahashi e

t al.

-decay recoil ion source

ranges in LHe

recoil: 0.5 m: 500 m

ranges in LHe

recoil: 0.5 m: 500 m

223Ra source

-decaydetectio

n

€

rE He

gas

223Ra: source of 219Rn ions

1.8 ms

223Ra

219Rn

5-6 MeV

~ 100 keV

215Po

211Pb

211Bi

207Tl

207Pb

4.0 s

11.4 d

36 m

2.2 m

4.8 m

How to extract snowballs at low temperature ?

12

8

4

0

snowball efficiency (%)

2.01.61.2temperature (K)

25

20

15

10

5

0

extraction efficiency (%)

2.01.61.2temperature (K)

conflicting temperaturerequirements

conflicting temperaturerequirements

W.X. Huang et al., NIM B 204 (2003) 592N. Takahashi et al., Physica B 329 (2003) 1596

W.X. Huang et al., Europhys. Lett. 63 (2003) 687We

go for

low t

empera

ture

Electric-field assisted extraction

5 cm

43210

SourceBottom electrode

Guidingelectrodes

Focusing electrode

Collector foil

Detector holder LHe dewarLHe dewar

LN2 dewarLN2 dewar

1 K pot

SF Hecell

alphadetector

electrodes

foil

up to 1200 V/cm no enhanced extraction

up to 1200 V/cm no enhanced extraction

Evaporation by second sound

fixing holequartz

substrate

NiCr thin film(140 )

current pulse

heater designheater designSF helium cell configurationSF helium cell configuration

NiCrheater

alpha detector

Al foil-200 V

electrode520 V

223Ra540 V

Second sound - heat wave without a pressure wave

Release of ions by evaporation

219Rn trapped at the surface

square current pulse to the second sound heater

width: 50 speriod: 500 ms

0.20

0.15

0.10

0.05

0.00

219

Rn count rate (/s)

16012080400

peak pulse height (V)

1.05 K 219Rn released from the surfaceand transported to the foil

if thermal motion only: 0.04 %

7.2(6) % extractionefficiency

7.2(6) % extractionefficiency

few % overallefficiency

few % overallefficiency

1.05K

A cryogenic gas catcher

alpha detector

Al foil-200 V electrode

520 V223Ra540 V

1 bar at room temperature

heliumneonargon

transport of 219Rn

remove impurities

1) ultra-clean system• UHV compatible• bakeable• helium purification < ppb not trivial (esp. large cells)

2) freezing the impurities

impurities in noble gas ion catcherslimit the performance:

• neutralization of ions (near or at thermal velocities)

• formation of molecules/adducts

Efficiencies at low temperature

35 35

30 30

25 25

20 20

15 15

10 10

5 5

0 0

efficiency (%)

140 100 60 140 100 60180 140 100 60

temperature (K)

helium neon argon

28.7(1) %

22.1(2) %

17.0(2) %

P. Dendooven et al., NIM A 558 (2006) 580

Rutherford scattering beam monitor

Vac

uum

can

72 K

shi

eld

4 K

shi

eld

Beam line

Guiding electrodes

cell

Silicon detector

Bottom electrode

Al foil

1 K pot

Rasource

Plasma region15 MeV Proton beam

223

Cry

osta

t

Rutherford Scattering

beam monitor

Online experimental setup (JYFL)

Vac

uum

can

72 K

shi

eld

Cry

osta

t

4 K

shi

eld

cell

1 K pot

-240V

-220V

-350V

-200V

250V

250V

Guiding electrodes

Bottom electrode

Silicon detector

Al foil

Rasource

223

On-line measurements

0.01

0.10

1.00

10.00

100.00

1 10 100 1000

Electric field (V/cm)

Effeciency(%)

1.7 pA

5 pA

40 pA

14 pA

0.5 pA

50 pA

@

Higher electric field is needed to get

maximum efficiency

at high beam intensities

On-line measurements

0.01

0.10

1.00

10.00

100.00

1 10 100 1000

Electric field (V/cm)

Effeciency(%)

120 pA

185 pA

45 pA

1.5 pA

12 pA

210 pA

410 pA

615 pA

@ 1035

On-line measurements@ 10106

0.01

0.10

1.00

10.00

100.00

1 10 100 1000

Electric field (V/cm)

Efficiency (%)

660 pA

310 pA

10pA

1pA

30pA

100 pA

@

0.01

0.10

1.00

10.00

100.00

1 10 100 1000

Electric field (V/cm)

Effeciency(%)

120 pA

185 pA

45 pA

1.5 pA

12 pA

210 pA

410 pA

615 pA

0.01

0.10

1.00

10.00

100.00

1 10 100 1000

Electric field (V/cm)

Efficiency (%)

660 pA

310 pA

10pA

1pA

30pA

100 pA

0.01

0.10

1.00

10.00

100.00

1 10 100 1000

Electric field (V/cm)

Effeciency(%)

1.7 pA

5 pA

40 pA

14 pA

0.5 pA

50 pA

Different behavior of efficiency curve

may be due to the

high mobility of electrons and

low mobility of positive ions

at low temperature

&

Re-ionization by beam

@ 1035 @ 10635

Summary of the data

blue to red = low to high E/n

(log scale, 0.1-6 x 10-18

V cm2)

77 K, 280 mbar10 K, 35 mbar

10 K, 106 mbar

Recombination loss - f

Ramanan, G.; Freeman, Gordon R., Journal of Chemical Physics, 93, 1990, 3120

f∝ Q P

ET − T,n

M.Huyse et al., NIMB, 187, 2002, Pages 535-547

v = E

+ =oT

P−=− T,n

−Mobility cm V s−

E −Electricfield V cm−

T −TemperatureK

P−Pressure

n−Densitycm−

f =Q α d

2

6 v− v+

Q − ionizing rate cm− 3s− 1

α − recombination coefficient cm3s− 1

v − Drift velocity cm s− 1

Efficiency vs. Recombination loss

4

6

0.1

2

4

6

1

2

4

6

10

2

Efficiency (%)

104

105

106

107

108

Recombination loss (arbitrary unit)

10 K, 35 mbar

10 K, 106 mbar

77 K, 280 mbar

Off-line Measurements for different pressures and

temperatures

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0 50 100 150 200 250

Electric field (V/cm)

Efficiency (%)

30 K - 626 mbar

20 K - 420 mbar

10 K - 204 mbar

5 K - 104 mbar

5 K - 54 mbar

10 K - 104.5

20 K - 219 mbar

30 K - 325 mbar

30 K - 103 mbar

20 K - 69 mbar

10 K - 33 mbar

5 K - 17 mbar

Summary

• Evidence for 2nd sound assisted extraction from superfluid helium

• Cryogenic gas catchers work

• High beam intensities require high electric fields

Near future plans

• Off-line test of second sound assisted extraction from superfluid helium

• On-line test of cryogenic gas catcher using radioactive ion beams

• Transport of ions to high vacuum, room temperature region

Collaborators

• Juha Äysto (JYFL, Jyväskylä)• Peter Dendooven (KVI, Groningen)• Kurt Gloos (University of Turku)• Takahashi Noriaki (Osaka Gakuin University) • Heikki Penttilä (JYFL, Jyväskylä)• Kari Peräjävi (JYFL, Jyväskylä) • Sami Rinta-Antila (JYFL, Jyväskylä) • Perttu Ronkanen(JYFL, Jyväskylä) • Antti Saastamoinen (JYFL, Jyväskylä)• Tetsu Sonoda (JYFL, Jyväskylä)