O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY Status of RIB Development at the HRIBF...

OAK RIDGE NATIONAL LABORATORY

U.S. DEPARTMENT OF ENERGY

Status of RIB Development at the HRIBF

HRIBF Workshop –

Nuclear Measurements for Astrophysics

October 23-24, 2006

Oak Ridge, TN

Dan StracenerPhysics Division, ORNL


U.S. DEPARTMENT OF ENERGY2

RIB Development and Testing Facilities

Ion Source Test Facility I (ISTF-1) characterize ion sources (efficiency, longevity, emittance, energy spread,

effusion) photodetachment tests with gas-filled RFQ ion cooler

Ion Source Test Facility II (ISTF-2) laser ion source ion source lifetime tests (KENIS – used for 17,18F beams)

On-Line Test Facility (OLTF) low intensity tests of target and ion source performance (release from

target, transport time, ionization efficiency) compatible with the RIB Injector and results are scaleable

High Power Target Laboratory (HPTL) target tests with high power beams from ORIC release measurements with larger target geometries

Facility for preparing target/ion source modules for the RIB Injector (assembly and quality assurance)



Holifield Radioactive Ion Beam Facility

25 MV Tandem Electrostatic Accelerator

RIB production Target Oak Ridge

IsochronousCyclotron (ORIC)

On-Line Test Facility

High Power Target Laboratory

Enge Spectrometer

Recoil Mass Separator

Daresbury Recoil Separator



Proton-rich Radioactive Ion Beams

• Seven different targets used• Three different ion sources• 33 radioactive beams

2m

HfO2 for 17,18F beams

CeS on RVC matrix for 34Cl



On-line Tests using SiC targets at the OLTF(for the production of 25Al and 26Al beams)

15 m diameter SiC fibers 1 m diameter SiC powder SiC does not sinter Maximum operating temperature is 1650 C Can increase yield significantly (x10) by adding

fluorine to system and extract as AlF

AlpSi 2528 ),( AlndSi 2528 ),(

AlpnpSi 2628 )2,(

AldSi 2628 ),(



Performed tests of SiC fiber target with beams up to 8.5 A No obvious degradation of target material 25Al and 26mAl yields up to 106 pps as AlF+

Almost equal amounts of Al+ and AlF+ Also observed Mg+ and Na+ beams

but not as fluoride molecular ions Will look for AlCl+ molecular ions

Next test will be a Nb5Si3 target this eliminates the carbon atoms and, possibly, the formation

of AlC, which is very refractory In December, we plan to test a different type of SiC material

that can withstand significantly higher temperatures (up to 2000 C instead of 1650 C)

SiC Target Tests at the HPTL



Pure Ga and In beams

Tests at the OLTF observed GaCl+ and InCl+ beams from UC target Added chlorine to the system using CH3Cl gas Results of measurements

pure molecular beams of Ga and In isotopes were observed – isobars were below detection threshold

molecular beam intensity depended on the chlorine concentration – yields were 10% to 50% of the atomic beam intensities

The efficiency for XCl+ to Xˉ needs to be measured Need to investigate the chloride formation as a function of target

temperature Conclusion: contamination of Ga and In beams can be greatly reduced,

but at the moment the yields will be lower

Also observed SrCl+ and BaCl+

Sr beams can also be purified using SrF+ (no neighboring contaminants)



Proton-rich Se beams

Observed proton-rich Se isotopes (70-73, 75, 79) Positive-ion yields are on the order of 105 to 106 pps/A Target: liquid Ge at temperatures from 1000° - 1300° C Production beam: 66 MeV alphas from the Tandem The yields of the Se+ beams decreased with increasing target

temperature, which suggests a molecular transport mechanism SeCO+ has been observed at ISOLDE, but we did not see it using

this target/ion source combination Measured a relatively short holdup time at 1000° C – less than 10

minutes Need to test a thin-layer liquid Ge target at the HPTL



Laser Ion Source Experiments

Laser ion source set up and operated at HRIBF in collaboration with a group from Mainz

Three-step ionization of Sn, Ge, Ni, Cu, and Mn obtained Autoionization states found for Sn and Ge (higher ionization efficiency) Frequency quadrupling of the Ti:sapphire used successfully, for the

first time, to resonantly ionize Cu atoms Measured beam emittance of laser-ionized and surface-ionized beams Measured time profile of laser-ionized beams Overall LIS efficiencies:

22% for Sn (compared to 10% reported at ISOLDE) 3.3% for Ge 2.7% for Ni 2.4% for Cu < 1% for Mn

Y. Liu, et al., NIMB 243 (2006) 442.



Laser setup for the initial tests at the HRIBF

Nd:YAG Pump laser(60 W, 10 kHZ, 532 nm)

Ti:sapphire lasers(supplied by the Mainz group)

Laser beam into the hotcavity through the mass-analysis magnet



Sn Ionization Scheme

-1

2

5

8

11Io

n C

urr

en

t (n

A)

Laser Off

-5

20

45

70

95

120

110 115 120 125 130 135

Mass (amu)

Ion

Cu

rre

nt (

nA

) Laser On120

118

116

122124

112 114Cs

Cs

286,3317 nm /

3 x 11638,06 cm-1

3427,7 cm-1

IP

0 cm-1

34914,2 cm-1

59231,8 cm-1

59375,9 cm-1

AI

1691,8 cm-1

823,5 nm / 12143,29 cm-1

47235,2 cm-1

811,4 nm / 12324,37 cm-1



Beam purification by photodetachment in RFQ Ion CoolerBuffer gas

Ion beam

10-6 Torr 10-6 Torr

10-4 Torr

10-1 - 10-2 Torr

DecelerationRe-accelerationRF Quadrupole

Laser beam

Coˉ: 99.9% neutralized

0.0

2.0

4.0

6.0

0 20 40 60 80Time (s)

Ion

Cu

rre

nt

(nA

)

0.0

2.0

4.0

6.0

8.0

10.0

0 20 40 60 80

Time (s)

Ion

Cu

rren

t (n

A)

Niˉ: 22% neutralized

90% 56Coˉ10% 56Ni ˉ

1% 56Coˉ99% 56Ni ˉ

Y. Liu, J.R. Beene, C.C. Havener, and J.F. Liang, Appl. Phys. Lett. 87, 113504 (2005).



Elevation View of HPTL



RIB Analysis Beam Line at the HPTL

Object Slits& Diagnostics

Image Slits& Diagnostics

Target/Ion Source

Quad 2

Quad 1

Beam Diagnostics

90° Magnet

Diagnostic End Station



Plans for Target Development at the HPTL

New materials tests with high beam power deposition SiC and metal silicides (e.g. Zr5Si3, Ta5Si3, Nb5Si3) for 25,26Al beams CeS for 33,34Cl and 29,30P beams

New target geometries Small incident angle (8 deg.) Thin liquids (Ge for 69As and p-rich Se beams) Thin solids for use with 3,4He production beams

(Al2O3 → P, SiC → S, C → 15O)

Effect of rastering the production beam Increase intensity of 17,18F beams from HfO2 (production beam presently limited to 3 A due to

target damage) Increased target diameter by a factor of three should allow an increase in the production beam

intensity by a factor of ten without increasing the power density Important measurements to be made include 17F(p,)18Ne, 18F(p,)15O 17F Beam-on-target is 1 x 107 pps – need about a factor of ten improvement

We need to significantly enhance the quality (intensity and purity) of the available proton-rich radioactive beams at the HRIBF.



Plans for Target Development at the HPTL

UC target tests Proton-induced fission vs. deuteron-induced fission (direct) Investigate 2-step targets (larger volumes) Higher density UC targets

Measure release efficiency for short-lived isotopes Lifetime of high-density targets (e.g. pressed-powder targets)

Actinide target materials (e.g. UB4, ThCx, low-density ThO2) Ion sources

LaB6 ion source to make pure Br and I beams (investigate long-term poisoning with high intensity production beams)

Close-coupled target to reduce effusion times

Other R&D efforts will focus on improving the quality of the available n-rich beams from actinide targets.

O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY Status of RIB Development at the HRIBF...

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