Development of ORRUBA — an Array for Transfer

Development of ORRUBA - an Array for Transfer Measurements at the HRIBF for Nuclear Astrophysics Steven D. Pain Rutgers University • Motivation – N 82 (d, p) experiments • Development of ORRUBA • First RIB data with ORRUBA ORNL, October 2006

ORRUBA motivation HRIBF yields N=82 Neutron magic-number nuclei at waiting points

Requirements of ORRUBA Proton Angular Distribution Proton Energy-Angle Systematics 132 Sn(d, p) @ 4. 5 Me. V/A 25 20 • High Solid Angular Coverage 20 • Good energy and angular resolution • Large dynamic range Energy (Me. V) Yield 15 15 10 10 5 5 0 0 30 60 90 120 Laboratory Angle (deg) 150 180

Requirements of ORRUBA Elastically scattered carbon Elastically scattered deuterons Protons from (d, p) Elastically scattered protons

Oak Ridge Rutgers University Barrel Array (ORRUBA) Design • 2 rings – q < 90°: 12 telescopes (1000 mm R + 65 mm NR) – q > 90°: 12 detectors (500 mm R) • 324 channels in total (288 front side, 36 back side)

ORRUBA Detector Design 8 strip non 4 strip resistive detectors

Prototype ORRUBA Detectors Perform detectors in house: Have 1/3 tests to determine: • Correct operation of detector (measurement Thirteen 1000 mm detectors of • position and energy independently) • Several 65 mm detectors • Energy Resolution • One 500 mm detector • Position Resolution • Number of prototypes • Depletion Depth for thick detectors

1000 mm Detector Performance - Depletion Detector not fully depleted 5. 8 Me. V a-particles only penetrate 30 mm into detector Either increase energy, or use more penetrating particles a particles into back face a particles into junction face Regions of poor charge collection Energy (a. u. ) Full bias 140 V 100 V 80 60 20 Position (a. u. )

Proton Scattering Tests

Proton Scattering Tests 11. 5 Me. V Energy (a. u. ) 12. 0 Me. V Position (a. u. )

Depletion Depths Effect limited to back 10% of detector Effect results in < 7% limit in maximum energy

Detector Test Results 1000 mm Detector 0. 5 mm FWHM on 11. 5 Me. V protons 68 ke. V FWHM on 11. 5 Me. V protons 1000 mm Detector • Detectors perform well, with good energy and position resolution Energy (a. u. ) • Detectors deplete >90% of their volume Thinner Detectors • 65 mm non-resistive detectors for DE layer, with greater segmentation (8 strips) • Detectors at assembly stage Position (a. u. ) 500 mm detectors just out of implant stage

124 Sn(d, p)125 Sn ORRUBA Test Setup 550 Me. V 124 Sn

124 Sn(d, p)125 Sn ORRUBA Test Setup 300 mm 500 mm 100 mg CD 2 target @ 60° 1000 mm + 65 mm 1000 mm

124 Sn(d, p)125 Sn ORRUBA Test Data – 1000 mm detector Counts 10. 0 Energy (Me. V) 7. 5 Co. M resolution ~150 ke. V 5. 0 0 2. 5 80 90 100 110 120 Lab Angle (deg) 130 140 1 2 3 4 5 Excitation Energy (Me. V)

132 Sn(d, p) Total Resolution (qlab< ~ 220 ke. V Co. M Resolution 80°) ~ 175 E resolution ~ 65 ke. V 55 Pos resolution ~ 110 ke. V 80 ke. V Target ~ 155 ke. V 135 Simulations

ORRUBA Performance – on-line 132 Sn(d, p)133 Sn data

Summary • Measurement of (d, p) reactions on heavy fission fragments requires high-solid angular coverage around 90°, with high resolution in energy and angle • ORRUBA developed to meet these requirements, and be as flexible as possible • Over 1/3 of detectors in house – arriving currently • First (d, p) data taken with ORRUBA detectors. Co. M resolution of 150 ke. V achieved with a 100 mg/cm 2 target @ 60 degrees • Early implementation of ORRUBA currently employed in the 130, 132 Sn(d, p) experiments

Collaborators J. A. Cizewski, R. Hatarik, K. L. Jones, S. D. Pain, M. Sikora, J. S. Thomas Rutgers University M. S. Johnson Oak Ridge Associated Universities D. W. Bardayan, J. C. Blackmon, C. D. Nesaraja, M. S. Smith, D. Shapira, F. Liang Oak Ridge National Laboratory R. L. Kozub Tennessee Tech. University J. James, R. J. Livesay Colorado School of Mines A. Chae, Z. Ma, B. H. Moazen University of Tennessee W. N. Catford, T. Swan University of Surrey

Proton Scattering Tests

ORRUBA Mount Photos

Proton Scattering Tests

Angular Straggling Measurements • 1000 mm stopping at forward angles • 65 mm non-resistive d. E at forward angles 1. 2 mm FWHM on 5. 85 Me. V protons Energy Angular straggling negligible at ~5 Me. V Position

ORRUBA Vacuum Chamber Cut-away Target Manipulator Beam Preamplifiers Possible to mount SIDAR upstream, to cover more backward angles, via second preamplifier ring Detectors mounted from preamplifier ring, on linear bearings, to allow detector access, without un-cabling Preamplifier feedthroughs

Guard ring effect (appears around 50 V bias) independent of deposited energy 1. 2 Me. V Energy (a. u. ) 1000 mm Detector Performance – a particle tests Position (a. u. )

ORRUBA Comparison • ORRUBA gives ~80% f coverage over the range 47° → 132° • Pre-existing setup gives <30% coverage over the range 60° → 120° • Factor of ~4. 5 times the solid angular coverage • Can perform experiments with more exotic (weaker) beams for given beam-time • Gain improved statistics from similar intensities • Can perform experiments with similar beam intensities with less beam -time

ORRUBA Vacuum Chamber and Preamplifiers Small cross for diagnostic detector Large cross target chamber Preamplifier ring Preamplifier Rails

ORRUBA + SIDAR Arrangement Target plane Beam 48° - 89° 91° - 132° 149° - 168°

130, 132 Sn(d, p) Experiments Measure (d, p) either side of N=82, at Z=50 Measurements around N=82 more experimentally challenging Measurements of 130 Sn(d, p) and 132 Sn(d, p) due to be performed imminently 20 ds/d. W (mb/sr) 15 Forward qc-o-m ↔ back qlab 10 Want to measure around 90 o 5 0 30 60 90 qlab (deg) 120 150

Motivation for Developing ORRUBA • Experiments on fission fragments must be performed in inverse kinematics • Inverse kinematics results in forward peaks in the (Co. M) angular distributions being dispersed over large range of back angles in the lab frame • The effects of the strongly inverse kinematics are dominant → suggests a general purpose array design • Measure excitation energies of states populated in the final nucleus with good resolution (~200 ke. V due to target thickness effects) • Measure proton angular distributions (ℓ transfer + spectroscopic information)

130, 132 Sn(d, p) Setup ORRUBA telescopes

134 Te(d, p) Motivation Pre-solar diamond grains • Overabundance of light and heavy Xe isotopes • Heavy isotope anomaly: relative excesses of 134 Xe and 136 Xe do not correspond to average r-process abundances 134 Xe U. Ott, Planetary and Space Science 49 (2001) 763 Suggested explanations: • Formation in intermediate neutron flux environment 135 Xe 136 Xe 133 I 134 I 135 I 136 I 132 Te 133 Te 134 Te 135 Te 136 Te (between s & r process) • Rapid separation of Xe from its precursors (Te and I) in supernova ejecta • Low entropy r-process N=82 Effect of structure around N=82 shell closure

(d, p) on r-process Nuclei From (d, p) Q-values, Ex, ℓ-values, Spec Information Calculate (n, γ) cross section (e. g. TEDCA) Use to modify residual interactions in nuclear structure (shell) model Improve global masses for n-rich nuclei Input into Supernova Code

Si-36 Custom Preamplifier Unit Design Inputs

140 mm Detector Traces

Effect of Shaping Time – 140 mm detector Counts Position (a. u. ) 1. 5 ms Energy (a. u. ) 1. 0 ms Energy (a. u. ) 0. 5 ms Position (a. u. )

58 Ni(d, p)59 Ni Test @ 250 Me. V CD 2 (~150 mg/cm 2 eff. ) • First (d, p) data taken with ORRUBA detectors p • Stable beam 58 Ni 65 mm ORRUBA • 58 Ni selected for convenience of acceleration 1000 mm ORRUBA

58 Ni(d, p)59 Ni Test @ 250 Me. V 400 CD 2 (~150 mg/cm 2 eff. ) p 58 Ni 65 mm ORRUBA 1000 mm ORRUBA Energy Loss (a. u. ) 300 200 100 0 0 100 200 Residual Energy (a. u. ) 300 400

58 Ni(d, p)59 Ni Test @ 250 Me. V CD 2 (~150 mg/cm 2 eff. ) 12 58 Ni 65 mm ORRUBA 1000 mm ORRUBA Proton Energy (a. u. ) p 8 4 0 80 100 Angle (deg) 120 140

ASICs Wash. U (St Louis)/MSU ASICs system • Preamps, discriminators, logic and analog circuits all on one (16 channel) chip • 2 chips per chip board • 16 chip boards per motherboard • Multiplexed analog signals → single flash-ADC for entire system • Dramatic cost reduction per channel compared with conventional electronics • External preamps (need high gain) Designed for non-resistive, low capacitance Si detectors

ASICs

Fission Fragment Beam Production 3. Ionize atoms 2. Transport to ion source 4. Create Negative Ions 1. Create nucleus of interest