Measurements of Neutron Activation of 76Ge and 136Xe

Report
Measurements of Neutron
Activation of 76Ge and 136Xe
James Esterline
Megha Bhike, Josh Bradt, Brent
Fallin, Sean Finch, Matt Gooden,
Calvin Howell, John Kelley, Werner
Tornow
Measurements of Neutron
Activation of 76Ge and 136Xe
James Esterline
Megha Bhike, Josh Bradt, Brent
Fallin, Sean Finch, Matt Gooden,
Calvin Howell, John Kelley, Werner
Tornow
Neutron Activation
• Spallation from cosmic m
• Interest in contributions to background in ROI
for 0n2b decay
• Secondary interest as nuclear structure study
• Analysis ongoing: progress and partial results
here presented
Experimental Setup
• Neutrons generated by 2H(d,n)3He
–
–
–
–
Utilized deuteron beam from TUNL’s DENIS
Pulsed at 2.5 MHz to enable time correlations
Produced neutron at energies En = 8.0, 12.0 MeV
Only presenting at 8 MeV
• Ran in (presently disassembled) Shielded
Source Area
– Maximum suppression of background neutrons,
photons
DENIS
Beam pickoff
DENIS
NTOF
Experimental Setup
• Illuminate samples with collimated neutron
beam
– Germanium as thick foil (irregular shape for
enriched)
– Xenon in metal spheres
• Use Fe foils instead of direct neutron flux
measurement for normalization
Experimental Setup
• Illuminate samples with collimated neutron
beam
– Germanium as thick foil (irregular shape for
enriched)
– Xenon in metal spheres
• Use Fe foils – unfortunately, shares prominent
transition energy (847 keV) with germanium
– Uncertainty of metal composition for Xe
– Added Ni foils
Experimental Setup
• Initially used clover detectors
– One detector with only two of four segments
operational; other with all four
• Switched to 60% HPGe detectors
• Have small contributions from scattered
neutrons activating detectors
Data Acquisition and Analysis
• Time of flight between pickoff and detection
Data Acquisition and Analysis
• Time of flight between pickoff and detection
Desired neutron activation
[Source g]
[Walk]
Rescattered, breakup neutrons
Data Acquisition and Analysis
• Energy deposited in germanium detectors
Data Acquisition and Analysis
• Data processed in one- or two-hour runs
• Flight time gates determined in aggregate
– 5% of peak height on signal peak
– Focus on maximizing accidental gate width
Data Analysis
Data Analysis
Data Acquisition and Analysis
• Data processed in one- or two-hour runs
• Flight time gates determined in aggregate
– 5% of peak height on signal peak
– Focus on maximizing accidental gate width
• Energy calibrations determined individually
for each run using prominent peaks (both
signal and background)
Data Acquisition and Analysis
• Data processed in one- or two-hour runs
• Flight time gates determined in aggregate
– 5% of peak height on signal peak
– Focus on maximizing accidental gate width
• Energy calibrations determined individually
for each run using prominent peaks (562 keV
(Ge)/847 keV (Fe), 40K, n-p capture, 214Bi)
Data Acquisition and Analysis
Data Acquisition and Analysis
Data Acquisition and Analysis
Data Acquisition and Analysis
• Apply calibrations and time of flight cuts
Data Acquisition and Analysis
Data Acquisition and Analysis
• Shared energy between detectors
Data Acquisition and Analysis
• Shared energy between detectors
• Also look at coincidence spectra
Data Acquisition and Analysis
• Obtain (~ d.c.s.) values for various transitions
Results
• Transitions in the ROI for Ge, Xe
Ge Spectra
2040.7 keV (from
E*(1+,2+) = 3951 keV)
2035 keV
(74Ge)
Ge Spectra
2040.7 keV (from
E*(1+,2+) = 3951 keV)
2035 keV
(74Ge)
Ge Spectra
2040.7 keV (from
E*(1+,2+) = 3951 keV)
2035 keV
(74Ge)
Xe Spectra
J. Bradt et al., 2012
Future Work
• Obtain estimates of total cross sections
• Apply scheme in full to natGe and 136Xe

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