study of the 40 ca( ) 44 ti reaction at stellar temperatures with dragon christof vockenhuber for...

Study of the 40Ca()44Ti reaction at stellar temperatures with DRAGON

Christof Vockenhuber for the DRAGON collaboration

Vancouver, B.C., Canada

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Collaboration

L. Buchmann, J. Caggiano, J.M. D’Auria, B. Davids, A. Hussein, D.A. Hutcheon, D. Ottewell, M.M. Pavan, C. Ruiz, G. Ruprecht, M. Trinczek, C. VockenhuberDRAGON collaboration at TRIUMF, Vancouver, BC, Canada

A. Chen, C. Ouellet, J. PearsonMcMaster University, Hamilton, ON, Canada

M. PaulHebrew University / Weizmann Institute, Israel

W. Kutschera, A. WallnerUniversity of Vienna, Austria

D. FrekersUniversity of Münster, Germany

A.M. Laird, R. LewisUniversity of York, England

H. Crawford, L. Fogarty, E. Ó’Conner, B. Wales, Summer students from Canada and Ireland

poster – No Number

B. Laxdal, M. Marchetto, K. Jayamana, ISAC operatorsTRIUMF staff, Vancouver, BC, Canada

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Role of 44Ti in Astrophysics

laboratory half-life of 60.0 +/- 1.0 years decay through electron capture, if ionized half-life becomes longer

detected in space by -ray satellites and in pre-solar grains

produced in supernova detection of relatively recent supernovae alpha-rich freeze-out just above the collapsing core observed quantity of 44Ti depends critically on ‘mass-cut’

understanding of production requires reliable reaction rates dominated by 4 reactions:

3 process 44Ti(,p)47V45V(p)46Cr 40Ca()44Ti

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Previous measurements of 40Ca()44Ti

prompt ray measurements in the 1970sE. L. Cooperman et al., Nucl. Phys. A 284 (1977) 163

W. R. Dixon et al., Phys. Rev. C 15 (1977) 1896; Can. J. Phys. 58 (1980) 1360

resonance strength of a few isolated resonances

recent AMS measurementH. Nassar et al., PRL 96 (2006) 041102

integral measurement of a large energy range

discrepancy by a factor of ~5

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Level scheme

H. Nassar et al., Nucl. Phys. A 758 (2005) 411c

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Astrophysical Reaction Rate

Reaction rate:

Resonance strength:

Measured Yield ( 44Ti / 40Ca ): Y( = 1 eV ) ~ 10 –11

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Experiment at DRAGON

alpha-rich freeze-out takes place at a large temperature regime

cover a large energy range ( Ecm ~ 2.0 – 4.2 MeV )

several narrow resonances contribute to the yield

‘thin’ target for sufficient resolution

’thick’ target to apply thick target yield

energy loss in the gas target Ecm ~ 10 keV / Torr

1 Torr: 220 energy steps

8 Torr: 30 energy steps

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Experiment at DRAGON

Advantage:

direct detection of recoils (44Ti) and rays measurement of single resonances high efficiency

windowless He gas target + BGO detector array acceptance: < 20 mrad (44Ti recoils ~ 6 mrad) high suppression of beam

recoil separator ~107

detector ~104

coincidence ~103

measurements of < meV possible

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Experiment at DRAGON

Challenges:

40Ca beam from Off-line Ion Source

2+ required for acceptance at RFQ accelerator (A/q < 30) 40Ar contamination (can be measured with ion chamber)

suppression of 40Ca depends on selected charge state ( ~106 – 1011 ) A/q ambiguities 44Ti11+ ↔ 40Ca10+

charge state distribution after the gas target acceptance of recoil spectrometer

identification of 44Ti ion chamber, TOF

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

What we measure

40Ca beam on target elastically scattered He atoms with collimated SB detectors beam contamination with ion chamber

produced 44Ti recoils 44Ti detected at the ion chamber charge state fraction after the target detection efficiencies

rays in coincidence with 44Ti energies and multiplicity z-position along the gas target

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

DRAGON windowless Gas Target

Target thickness

1 – 10 Torr H2 or He gas

~1018 atoms / cm2

Elastic monitor detectors:

detect scattered gas particles

Charge State Booster (CSB):

100 nm SiN foil (30 g/cm2)

increase mean charge state by ~2

charge state distribution independent of position along the path in the target

CSB

gas foil

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

30 BGO Gamma detectors surrounding gas target

geometrical efficiency of ~ 90 % effective efficiency depends on energy and

multiplicity determined from GEANT simulations and point source studies

DRAGON detector Array

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Recoil Mass Separator

Inverse Kinematics:

Energy spread a few percent achromatic system

Cone angle a few 10 mrad large gaps, large detectors

Energy of recoils < beam energy problem of energy loss tails

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Particle Identification

entrance window 130 µg/cm² Mylar, 50 µg/cm² PP, 15-30 µg/cm² SiNdiameter 5 cmenergy resolution: ~ 1 % for 1 MeV/u 40Ca

Cathode

Frisch Grid

Anode 1 Anode 2 Anode 3

Ionization chamber

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Beam Contamination

Hybrid-surface ion source

14

IC Anode 2

IC A

no

de

1

+

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

44Ti identification Ionization chamber

singles

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

44Ti identificationIonization chamber – ray coincidence

coincidences Y ~ 1 x 10-10

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

44Ti identificationTime-of-Flight through Spectrometer

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Beam Suppression

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44Ti

12 13 14 15 16 170.0

5.0x10-12

1.0x10-11

1.5x10-11

2.0x10-11

Ra

w Y

ield

N44

Ti /

N40

Ca

Charge State q

0%

10%

20%

30%Ti, 0.93 MeV/u

recoils 8 Torr

Ch

arg

e S

tate

Fra

ctio

n F

q

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44Ti

12 13 14 15 16 170.0

5.0x10-12

1.0x10-11

1.5x10-11

2.0x10-11

Ra

w Y

ield

N44

Ti /

N40

Ca

Charge State q

0%

10%

20%

30%Ti, 0.93 MeV/u

recoils 8 Torr Sayer Solid

Ch

arg

e S

tate

Fra

ctio

n F

q

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44Ti

12 13 14 15 16 170.0

5.0x10-12

1.0x10-11

1.5x10-11

2.0x10-11

Ra

w Y

ield

N44

Ti /

N40

Ca

Charge State q

0%

10%

20%

30%Ti, 0.93 MeV/u

recoils 8 Torr Sayer Solid beam CSB

Ch

arg

e S

tate

Fra

ctio

n F

q

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44Ti

12 13 14 15 16 170.0

5.0x10-12

1.0x10-11

1.5x10-11

2.0x10-11

Ra

w Y

ield

N44

Ti /

N40

Ca

Charge State q

0%

10%

20%

30%Ti, 0.93 MeV/u

recoils 8 Torr Sayer Solid beam CSB beam 2 Torr

Ch

arg

e S

tate

Fra

ctio

n F

q

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44Ti

12 13 14 15 16 170.0

5.0x10-12

1.0x10-11

1.5x10-11

2.0x10-11

Ra

w Y

ield

N44

Ti /

N40

Ca

Charge State q

0%

10%

20%

30%Ti, 0.93 MeV/u

recoils 8 Torr Sayer Solid beam CSB beam 2 Torr beam 4 Torr

Ch

arg

e S

tate

Fra

ctio

n F

q

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44Ti

12 13 14 15 16 170.0

5.0x10-12

1.0x10-11

1.5x10-11

2.0x10-11

Ra

w Y

ield

N44

Ti /

N40

Ca

Charge State q

0%

10%

20%

30%Ti, 0.93 MeV/u

recoils 8 Torr Sayer Solid beam CSB beam 2 Torr beam 4 Torr beam 8 Torr

Ch

arg

e S

tate

Fra

ctio

n F

q

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Excitation function 40Ca()44Ti

1.0 T9 temperature regime 2.8 T9

preliminary !

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

BGO ray spectrum

1.130 MeV 40Ca

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

coincidence

measured ray data will be used to estimate BGO efficiency

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Summary

We measured the 40Ca()44Ti reaction at the recoil mass spectrometer DRAGON in the energy regime of supernova nucleosynthesis (T9 ~ 1 – 2.8)

A first preliminary analysis gives a total 44Ti yield between prompt ray and AMS data, a detailed analysis including ray data and GEANT simulation for BGO efficiency will follow

Additionally, we learned a lot:

could demonstrate to measure resonance strength for astrophysics in mass 40 region

measure an excitation function over a large energy range

important for reactions with radioactive beams

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

R. Diehl et al. (2005)

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

IC spectra 44Ti10+

singles

44Ti 10+

40Ca7+ 850 keV/u 8 Torr He

Y ~ 4 x 10-12

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

IC spectra 44Ti10+

44Ti 10+

coincidences

40Ca7+ 850 keV/u 8 Torr He

Y ~ 4 x 10-12

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

IC spectra 44Ti9+

44Ti 9+

singles

40Ca7+ 716 keV/u 8 Torr He

Y ~ 2 x 10-13

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

IC spectra 44Ti9+

44Ti 9+

coincidences

40Ca7+ 716 keV/u 8 Torr He

Y ~ 2 x 10-13

Christof Vockenhuber 40Ca()44Ti at DRAGON NIC-IX June 27 2006

Charge State Distribution of 44Ti

without charge state booster foil