Science Program Upgrade Plans

1

Science Program Upgrade Plans

• Scientific accomplishments

• Opportunities

Witold Nazarewicz

Ganil, June’07

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Recoil Mass Spectrometer (RMS)

Injector for Radioactive Ion Species 1 (IRIS1) 25MV Tandem

Electrostatic Accelerator

Daresbury Recoil Separator (DRS)

Oak Ridge Isochronous Cyclotron (ORIC)

On-Line Test Facility (OLTF) High Power Target

Laboratory (HPTL) Stable Ion

Injector (ISIS)

Enge Spectrograph

HRIBF in 2006

3

The first transfer measurements on N~82 nuclei on / near r-process path

130Sn(d,p)¹³¹Sn - R. Kozub et al.

132Sn(d,p)¹³³Sn - K.L. Jones et al.

134Te(d,p)¹³⁵Te - S.D. Pain et al.

• yields, angular distributions of low-lying states measured

• first observation of p_1/2 state in ¹³³Sn

• three other states in ¹³³Sn measured, calibrated with ¹³⁰Te(d,p)

• evidence for numerous states in ¹³¹Sn never seen before

• evidence that the f_5/2 level in ¹³⁵Te is at a significantly higher energy

132Sn(d,p)¹³³Sn

K. Jones

Superallowed -decay

Xe →

Te →

Sn

(5/2

)

(5/2

)

E

= 4.703 keV

620 620   70 ns 70 ns

1.9 s

l=0

105

Te

52

101

Sn

50



(

Te)/

(

Po)

=2.4(3)

100Sn +ⁿ+



105Te



Sn +n

101Sn

208Pb +ⁿ+

 

213Po



S. Liddick et al., PRL 97,082501(2006)

 Old

standard

(different shell structure for neutrons and protons)

New

standard

(the same shell structure for neutrons and protons)

Identification at HRIBF of fastest known alpha decays:

• rp-process termination

• en route to

Te →

Sn

5

The evolution of shell structure in very neutron-rich nuclei beyond the N=50 shell closure

beam T_1/2 (s) main results

⁷⁹Cu 0.19 ndecay observed first time

83Ga 0.30 n,, s_1/2 in N=51 ⁸³Ge ⁸⁴Ga 0.08 2⁺ in N=52 ⁸⁴Ge

85Ga ??? rate of 0.1pps…

-decay studies around ⁷⁸Ni with postaccelerated (3 MeV/u) pure neutron-rich RIBs

• t_1/2 & n rates for many r

process nuclei are accessible

• Energy levels test evolving nuclear structure

• Range out unwanted high-Z contamination with high pressure & tape transport

• Absolute beta-delayed neutron

branching ratios for ^76-79Cu and ^83-84Ga

• Identification of new excited states in

77Zn, ⁷⁸Zn, ⁸²Ge, ⁸³Ge, and ⁸⁴Ge

• Systematics of single particle levels (e.g. neutron s_1/2) near doubly magic

78Ni

Winger et al.

Observation of fusion enhancement at sub-barrier energies in ^132,134Sn+⁶⁴Ni

• Probing the influence of neutron excess on fusion at and below the Coulomb barrier

• Large sub-barrier fusion enhancement has been observed

• Inelastic excitation and neutron transfer play an important role in the observed fusion enhancement

• Important for superheavy element synthesis

• ERs made with ^132,134Sn cannot be made with stable Sn

Shapira et al., Eur. Phys. J. A 25, s01, 241 (2005)

Liang et al., PRL 91, 15271 (2003); PRC 75, 054607 (2007)

rp-process termination 7

H.Schatz et al., PRL86 (2001) 109

I →

Sb →

Sn

• No observable proton emission from ¹⁰⁵Sb

• The rp-process termination cycle starts at ¹⁰⁵Sn

• If ¹⁰⁴

Sb

Sn !

Astrophysical relevance : C.Mazzocchi, …, H.Schatz,…PRL 98,212501 (2007) Astrophysical relevance : C.Mazzocchi, …, H.Schatz,…PRL 98,212501 (2007)

?

 p

search for

Cs weak  -decay : S

of

I and

Sb

~10

%

 -decay of

I and the rp-process

Q



=3918(21) keV Q

(

Sb)=356(22) keV ≠491(15) keV

Sn-Sb-Te cycle

Sn-Sb-Te cycle

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International Perspective (cont.) International Perspective (cont.)

76Cu (0.64 s) : 150 - 300 pps

77Cu (0.47 s) : 15-25 pps

78Cu (0.34 s) : 1.5-3 pps

79Cu (0.19 s) : 0.13-0.2 pps

83Ga (0.31 s) : 30-60 pps

84Ga (0.085 s) : 1.5 pps

85Ga ( ??? ) : 0.12 pps

Postaccelerated, separated with high-resolution and ranged-out beams

HRIBF Cu rates are about 30-50 times higher in comparison to ⁸⁶Kr fragmentation at NSCL (Ni,Co,Fe rates are better at NSCL)

HRIBF Ga rates are about 30-60 times higher in comparison to the non-accelerated ion rates at PARRNe (Orsay, France) EPJ A28, 307,2006

Example: -decay of ²³⁸U fission products (Rykaczewski)



HRIBF, ⁷⁸Cu ~ 1.5-3 pps: ~ 19 hours counting !

-energy

Leuven – ISOLDE PR C71,054307,2005

78

Cu :

Ga ~ 1:10 000

78Cu -decay

78

Cu :

Ga ~ 1 :10

Coulomb excitation in n-rich systems

Pioneering Coulomb excitation of beams of radioactive isotopes of Ge, Sn, Sb, Te

3000 ¹³⁴Sn/s

• Probing the evolution of

collective motion in neutron-rich nuclei

• Increasingly larger contributions of neutrons to B(E2) values

above ¹³²Sn

• Recoil-in-Vacuum technique used to measure the g-factor for the first 2⁺ state in ¹³²Te:

Stone et al., PRL 94, 192501 (2005)

Padilla-Rodal et al. Phys. Rev. Lett. 94, 122501 (2005) Yu et al., Eur. Phys. J. A 25, s01, 395 (2005)

Radford et al., Nucl. Phys. A752, 264c (2005) Varner et al., Eur. Phys. J. A 25, s01, 391 (2005) Baktash et al., to be published

Chae et al., PRC 74 (2006) 012801. 10 Bardayan et al., PRL 89 (2002) 262501.

Kozub et al., PRC 71 (2005) 032801

HRIBF measurements

reduced uncertainty in

18F(p,)¹⁵O rate reduced by ~30x 18

F(p,  )

O

18

F is

-potentially important source of -rays from novae -target of billion dollar orbiting telescopes

The understanding of ¹⁸F(p,)¹⁵O reaction crucial

Off resonance measurements

provided first constraints on interference in

the ¹⁸F+p system.

First Constraint on Very Low Temperature

F(p, ) 

O

reaction rate in Novae

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7Be(p,p₁)⁷Be*

5 10 15 20

0

E_cm (MeV)

_cm=124

7Be(p,p₀)⁷Be

d/d (mb/sr)

50 150

100 _cm=128

5⁺

ionization chamber

7Be

H₂ gas

Daresbury Recoil Separator

Solar Physics: Understanding

8

B and the solar thermonuclear

7

Be(p,)

B reaction

Measurements of ⁷Be+p elastic & inelastic scattering have improved our understanding of the ⁸Be level structure

First statistically significant direct

measurements of the ⁷Be(p,)⁸B cross section using a ⁷Be beam are testing

systematic uncertainties in the ⁷Be(p,)⁸B cross section

4⁺

8

B

12

“Best studied” deformed proton emitters

Ho and

Ho

~1.7%

7.4(3)s

Excited states in ¹⁴¹Ho from GS+FMA exp !

Both measured properties of ^141mHo decay, the decay rate (factor 2-3 too large) and fine structure (factor 5 too small) call for a change in our understanding of the ^141mHo (and ^141gsHo) wave function

• ¹⁴¹Ho is 20 neutrons away from stable ¹⁶¹Ho

• Tensor interaction plays a role in proton-rich systems

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Future Science Program

(details in the Strategic Plan!)

Future research at HRIBF includes studies of:

• Exotic nuclei near shell closures (such as ⁷⁸Ni, ⁸²Ge, ¹⁰⁰Sn, and ¹³²Sn), which have a direct bearing on the shell-model description of the nucleus and the origin of heavy elements.

• Properties of neutron-rich unstable nuclei and their reactions to find the way to synthesis of the heaviest nuclei and to improve our understanding of supernovae and red giant stars.

• Two-neutron transfer in neutron-rich nuclei: probing the particle-particle channel

• Superallowed alpha decays and cluster decays above ¹⁰⁰Sn

• Proton- and alpha-induced reactions on, and the properties of, proton-rich radioactive nuclei to understand element synthesis and energy generation in stellar explosions.

• Systematic studies of magnetic moments using RIV and transient field method

• Solar neutrino flux using radioactive ⁷Be beam

• Studies of molecular states in light nuclei with the ¹⁰Be beam

HRIBF’s science for the benefit of society (the opportunity for advances in other scientific fields and applied technologies)

• Accelerator Mass Spectrometry program centered around the 25-MV tandem

• Applications of ⁷Be in life sciences

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OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY

Vanderbilt – 6 April 2007

www.phys.utk.edu/JUSTIPEN Provides travel and local support

for U.S. participants to JUSTIPEN.

Fully funded in FY07….

(about 25 visits and 2-3 long term—

3 month -- visits).

Initial Steering Committee:

Takaharu Otsuka (Managing Director, U. Tokyo) David Dean (Associate Director, ORNL)

Tohru Motobayshi (Associate Director, RIKEN) Witek Nazarewicz (UT/ORNL)

Baha Balantekin (University of Wisconsin) Hiashi Horiuchi (Kyoto University)

Hideyuki Sakai (University of Tokyo) Richard Casten (Yale University)

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OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY

Vanderbilt – 6 April 2007

STATUS: FUNDED

• State of TN: $250,000

• University of TN: $ 37,500

• Vanderbilt Univ: $ 37,500

• ORNL $ 75,000

• TOTAL: $400,000

• Business model:

• Enable enhancement of RIB research at HRIBF through

theory visitors; enable international RIB theory program

Infrastructure supported by UT and ORNL Physics Division.

Three proposals sold the concept:

1. JUSTIPEN (closed the deal) 2. SciDAC (2005/6)

3. initial topical center idea (2003) Joe Hamilton, Carrol Bingham, Witek Nazarewicz, and DJD obtained funding.

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An Upgrade to HRIBF:

RIB production by photofission

 Can enhance HRIBF neutron-rich yields by a large factor very cost- effectively

 Implement a ~100kW turn key electron accelerator with energy in range 12 to 50 MeV

 Photofission Driver

 A minimum fission yield of 10¹³ f/s can be achieved with present target technology for E_e>20 MeV– larger with advanced target

 Factors well over 10³ for

enhancement of very neutron rich species

 A lower cost facility can be built with 100 kW, E_e~12 MeV driver.

 can achieve ~2x10¹² f/s with existing targets (5x reduction in yield compared to ≥ 25 MeV e)

^ph-f/s 10 A 40 MeV p

Improvement vs. HRIBF Yields

grey = stable

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Photofission Yields

Ge

Sn

Photofission is “cooler” than proton-induced fission, thus yield curve is more neutron-rich

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Science highlights with Photofission Driver

 Will test the evolution of nuclear structure to the extremes of isospin

 Will improve our understanding of the origins of the heavy elements

Decay properties of nuclei at the limits:

Decay properties of nuclei at the limits:

Crucial for understanding the formation Crucial for understanding the formation of elements from iron to uranium

of elements from iron to uranium

Reaction mechanisms for the formation of superheavy nuclei Collective properties in extended neutron radii:

Coulomb excitation near ⁹⁶Kr

Evolution of structure: Coulex, moment measurements, transfer at ¹³²Sn & beyond

Evolution of structure near ⁷⁸Ni: Transfer reactions, Coulex,

moment measurements

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IBA Rhodotron

Electron Accelerator

Willing to scale their 10 MeV, 20mA unit (shown) to 25 MeV



Over 17 units sold, including

ISOMEDIX (USA)

STUDER (SWITZERLAND) A.E.0.I.( IRAN)

ENUSA (SPAIN) ECI (BELGIUM)

RISTRON (GERMANY) HOSPAL (ITALY)

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Electron Beam Facility Elevation

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Coulex (1-step)

Accessible at HRIBF Accessible w e-machine

22

Multi-step Coulex

Accessible at HRIBF Accessible w e-machine

23

g-factor Measurements

Accessible at HRIBF Accessible w e-mach

24

Transfer reaction studies

Accessible at HRIBF

Accessible with e-machine

25

E-Machine Cost and Schedule



Two possibilities



Single (80 kW, 12.5 MeV)



Vs.



Dual Rhodatrons (60-100 kW, 25 MeV)

 5x more RIBs with two Rhodatrons



Classic case of capital cost vs yields of RIBs



Cost



$23M for 1-Rhodatron version



$34M for 2-Rhodatron version



Schedule



3-4 years required



CD-n sequence must be followed