Laser

Christopher Geppert ISOLDE Workshop and Users Meeting 2008

Technical Developments for

Precision Spectroscopy of light

Isotopes (Be)

in Collinear Laser

Spectroscopy (IS449)

Technical Developments for

Precision Spectroscopy of light

Isotopes (Be)

in Collinear Laser

Spectroscopy (IS449)Ch. Geppert, W. Nörtershäuser, M. L. Bissell, M. Kowalska, J. Krämer, A. Krieger, R. Neugart, R. Sanchez,

F. Schmidt-Kaler, D. Tiedemann, Ch. Weinheimer, D. T. Yordanov,

C. Zimmermann, M. Zakova,

GSI, GermanyUni. Mainz, Germany

MPI für Kernphysik, GermanyKatholieke Universiteit Leuven, Belgium

Uni. Tübingen, GermanyCERN, Physics Department, Switzerland

Uni. Münster, GermanyUni. Ulm, Germany


Isotope Shift

= Frequency difference in an electronic transition between two isotopes

Isotop 1

Isotop 2

IS = MS +|(0)|2 r2Z

3

FS

Mass Effect, nuclear motionField Shiftfinite size of the nucleus

theory theory


Isotope Shift Measurement

IS = MS + FS

laser spectroscopy on single ions in a two–

stage Paul trap

Method 1

high accuracy ~200 kHz laser system has been developed

requires long time for trap and beam line development

+

!

+

collinear laser spectros-copy on fast ion beam

Method 2

identical laser system

existing beam line COLLAPS

requires improvement in accuracy on spectroscopy of light isotopes

+

!

+

Addendum to IS449

IS449

calculations show: field shift coefficient for Be+ ~16 MHz/fm2

accuracy of ~2 MHz sufficient for testing rc on ~ 1 % level

…but


11Be – Technique: Frequency-Comb based Collinear Laser Spectroscopy

4

0

≈ 1.5 THz

a- fixed

applied voltageapplied voltage

c- fixed

≈ 1.5 THz

Photo multiplier

ion beamEkin~60 keV

collinear laser beamfixed frequency

+

anticollinear laser beamfixed frequency

10c

working principle

•fixed laser frequency•Doppler-tuning of ion velocity

large Doppler-coefficient for 11Be:30 MHz/Volt required voltage precision better than 0.1 V on ~60 kV ~ 1 ppm

!

! voltage cancellation by simultaneous collinear & anti-collinear laser spectroscopy

10a

20

20

22 1 a c


Shaping Optics

Retardation

Deflector

Frequency

Doubler

Frequency

Doubler

Laser Spectroscopy Setup

beamblocker

beamblocker

-1500 -1000 -500 0 500 1000 15000

10000

20000

30000

40000

50000

Y A

xis

Title

X Axis Title

B

Be+- Beam

PMT

COLLAPS

I2

Servo

Dye Laser

(Collinear)

FM-Iodine Lock

20 m fiber

ServoDye Laser

(Anticollinear)

Frequency

Comb

Photodiode

Rubidium

Clock

20 m fiber


Shaping Optics

Retardation

Deflector

Frequency

Doubler

Frequency

Doubler

beamblocker

beamblocker

Be+- Beam

PMT

COLLAPS

I2

Servo

Dye Laser

(Collinear)

FM-Iodine Lock

20 m fiber

ServoDye Laser

(Anticollinear)

Frequency

Comb

Photodiode

Rubidium

Clock

20 m fiber



Shaping Optics

Retardation

Deflector

Frequency

Doubler

Frequency

Doubler

beamblocker

beamblocker

Be+- Beam

PMT

COLLAPS

I2

Servo

Dye Laser

(Collinear)

FM-Iodine Lock

20 m fiber

ServoDye Laser

(Anticollinear)

Frequency

Comb

Photodiode

Rubidium

Clock

20 m fiber



Scanning Procedure

1.

choosing proper scanning range for deceleration voltage to scan over all resonance lines for collinear laser

2.

locking collinear laser frequency to feasible iodine line

3. adapt anti-collinear laser lock point on frequency comb such, that anti-collinear spectra can be observed in same voltage range


Off-line Results

Variation of the offset voltage between optical detection region and deceleration electrodes

systematic effects testing :

Measurement of the absolute transition frequency at different iodine lines

Power dependence of spectroscopy lasersno effect

Misalignment of collinear laser relative to the ion beam ≤ 500 kHz

Measurements at different acceleration voltages of 30 and 60 kV

no effect

no effect

no effect

0-Lit= 99.8 ± 0.9 MHz

off-line test shows feasibility of method 1.

2. 9Be absolute frequency deviation from literature

98,0 98,5 99,0 99,5 100,0 100,5 101,0 101,5 102,00

2

4

6

8

10

12

14

16

18

20

Fre

quen

cy d

istr

ibut

ion

0-

Lit

88 spectra(60 kV)

9Be absolute frequency distribution

0-Lit / MHz

Lit taken from: D. J. Wineland, J. J. Bollinger, and W. M. Itano, Phys. Rev. Lett. 50, 628 (1983).

Iodine Frequency Intensity Rotat. Vibr. HF Lock Frequency

Line # (cm-1) (arb. units) GHz

1 16.004,550544 2,13E-06 R( 62) ( 8- 3) a 1 959608,70142 16.005,174912 1,20E-06 R( 70) (10- 4) a 1 959646,13753 16.005,596425 1,24E-06 P( 64) (10- 4) a 1 959671,41084 16.006,740634 2,16E-06 R( 60) ( 8- 3) a 1 959740,01585 16.008,855569 2,19E-06 R( 58) ( 8- 3) a 1 959866,82426 16.010,895381 2,21E-06 R( 56) ( 8- 3) a 1 959989,12827 16.012,860102 2,22E-06 R( 54) ( 8- 3) a 1 960106,92998 16.014,749763 2,23E-06 R( 52) ( 8- 3) a 1 960220,2311

16.018,304026 2,23E-06 R( 48) ( 8- 3) a 1 960433,33949 16.019,968683 2,22E-06 R( 46) ( 8- 3) a 1 960533,1497

10 16.021,558394 2,20E-06 R( 44) ( 8- 3) a 1 960628,466411 16.023,073183 2,17E-06 R( 42) ( 8- 3) a 1 960719,290812 16.024,513075 2,13E-06 R( 40) ( 8- 3) a 1 960805,624613 16.025,878093 2,09E-06 R( 38) ( 8- 3) a 1 960887,469014 16.027,168260 2,04E-06 R( 36) ( 8- 3) a 1 960964,8255


On-Line Results

Collinear

Anti-Collinear

Cou

nts,

arb

. uni

ts

2 1 0 -1 -2

-cg, GHz

9Be

10Be

11Be

-2 -1 0 1 2

includes:

statistical standard deviation

laser-ion beam misalignment (~ 500 kHz)

additionals contributions:

rubidum clock uncertainty ~ 400 kHz

ion recoil correction ~ 100 kHz

W. Nörtershäuser et al.accepted for PRL

preliminary


Outlook Be-Laser Spectroscopy

Option:

Current status:

Addendum IS 449 completed

Re-measuring isotope shift of 7,9,10,11Be determined with ~ 200 kHz precision in linear Paul trap

depending on agreement with competitor’s results

Future:

Isotope shift measurement of 12Be using COLLAPSISCOOL

• test of required precision in off-line Ga-beam time• test of ISCOOL performance on very light isotopes

(buffer gas? transmission?)

in 1½ weeks from now???

Isotope shift measurement of 14Be (2- or 4-neutron Halo?)

find adequate technique (yield ISOLDE: 4 s-1, t ½=4 ms)

Isotope shift of 7,9,10,11Be determined with ~ 1MHz precision measurement of charge radii with ~1% uncertainty

continue with original proposal IS 449

new proposal 2009 (?)

but....

1

2


ISOLDE high voltage calibration

ASTEC-1

ASTEC-2

Situation:

Two high voltage power supplies for GPS and HRS with internal voltage divider measurement available:

ASTEC-1 and ASCTEC-2

specified relative precision 10-4

= 6 V @ 60 kV

HV potential determines the ion beam energy crucial for classical collinear laser spectroscopy

inconsistencies of ion energies observed at COLLAPS in between two runs in the past

alternative approach for precision voltage determination instead of rather complicated collinear/anti-collinear laser spectroscopy

Motivation for Voltage Calibration

1.

2.


Collaboration with the group of Prof. Weinheimer at University Münster and the KATRIN collaboration

High Precision Voltage Divider

http://www.uni-muenster.de/Physik.KP/AGWeinheimer/

Parameterscaling factor 1972,48016(61)relative. standard deviation 0,32 ppmtemperature dependence -0,81(6)ppm/Kvoltage dependence 0,032(6)ppm/kVvoltage regime -8 kV to -32 kVheating time (ppm regime) ~ 2 minutesheating time (sub-ppm regime) ~ 3 hoursreproducibility (1 month) ~0,3 ppmlong time stability 0,604ppm/month

access to high precision voltage divider build for voltage measurement in the sub-ppm regime


0 5000 10000 15000 20000 25000 30000 35000-10

-5

0

5

10

15

20

25

deviation ASTEC2: + (6.4±0.2)E-4

ASTEC1 (GPS)ASTEC2 (HRS)

De

via

ton

ISO

LD

E D

ivid

ers

/

Vo

lt

Voltage KATRIN Divider / Volt

deviation ASTEC1: - (2.5±0.2)E-4


0 5000 10000 15000 20000 25000 30000 35000-10

-5

0

5

10

15

20

25

60000-20

-10

0

10

20

30

40



De

via

ton

ISO

LD

E D

ivid

ers

/

Vo

lt




0 5000 10000 15000 20000 25000 30000 35000-10

-5

0

5

10

15

20

25

60000-20

-10

0

10

20

30

40



De

via

ton

ISO

LD

E D

ivid

ers

/

Vo

lt




= 54 V

Voltage Calibration ASTEC-1 & 2

0 5000 10000 15000 20000 25000 30000 35000-10

-5

0

5

10

15

20

25

60000-20

-10

0

10

20

30

40



De

via

ton

ISO

LD

E D

ivid

ers

/

Vo

lt



laser spectroscopydeviation ASTEC2:

+ (6.4±0.2)E-4

= 54 V


Voltage Calibration ASTEC 1 & 2

HV divider

acceleration voltage measurement

laser spectroscopy

ion energy measurement

Observations and Results:

total deviation in the order of 10-3 = one order worse than specified

low ripple (few mV at a ~ 5-10 s time base)

small discrepancy (< 3 eV) between ion energy and HV platform potential

provide (temporary) calibration of ASTEC 1 & 2

0 5000 10000 15000 20000 25000 30000 35000-10

-5

0

5

10

15

20

25

60000-20

-10

0

10

20

30

40



De

via

ton

ISO

LD

E D

ivid

ers

/

Vo

lt



laser spectroscopydeviation ASTEC2:

+ (6.4±0.2)E-4

= 54 V


Isotope Yield11Be 5.7 x 107 ions/pulse

Thanks...to the RILIS team and the

impressive performance of their new solid-state pump laser system

strong support from coordinatorand ISOLDE technical crew

(operators, vacuum support, Jan Schipper for HV

measurements, .....)


the Be+ laser crewthe Be+ laser crew

thank you for your attentionthank you for your attention


End


Radii of Halo Isotopes

Charge radius measurements of light (Z<18) radioactive isotopes:

2004: 6He at ANL, L.-B. Wang et al. PRL 93, 142501

2003 : 6,7,8,9Li at GSI G. Ewald et al., PRL 93, 113002

2004: 11Li at TRIUMF, R. Sanchez et al., PRL 96, 033002

2007: 8He at GANIL, P. Müller et al. PRL 99, 252501

Chronology:

3.7 fm}


Beryllium: Nuclear Charge Radii

20

7 8 9 10 112.3

2.4

2.5

2.6

2.7

2.8 Tanihata NCSM2005 COLLAPS GFMC FMD

Nuc

lear

Cha

rge

Rad

ius

(fm)

Be Isotope

References:

Thanks to R.Torabi, Th. Neff, H. Feldmeier and P. Navratil for providing unpublished data !

Electron Scattering: rc(9Be) = 2.519(12) fm, J.A. Jansen et al., Nucl.Phys.A 188, 337 (1972).Muonic Atoms: rc(9Be) = 2.39(17) fm, L.A. Schaller, Nucl.Phys.A 343, 333 (1980).

7 fm


Scan Overview

Isotop IsotopResolution low high low high low high low high low high Resolution low high low high low high low high low high

J2-Linie J2-Linie104 2287

600 1623 2013 145 495

600 850 600 200 300 300

630 250 100 75 142 356

201 50 137 25 445

300 300

low resolution: 401 steps for odd isotopes, 201 steps for 10Behigh resolution: 801 steps for odd isotopes, 401 steps for 10Be

470

356

300

0

300

14 0

15 0

10 100 217

0

8 145 495

D2-Linie

7Be 9Be 10Be 11Be 12Be

11 201 187

12 300 300

9 200

7

0

0

7

8

9

10

11

12

14

15

250

0

0

~600

630

0

0

3636600

600850

D1-Linie

104 2287

7Be 9Be 10Be 11Be 12Be


Level Schemes for Beryllium

11Be+7,9Be+

2s½F=1

F=2

2p½F=1

F=2

2s½F=0

F=1

2p½F=0

F=1

10Be+

2s½

2p½

~313,2 nm

= 8,1 (4) ns

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