measurements of neutron activation of 76 ge and 136 xe james esterline megha bhike, josh bradt,...

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

NTOF

DENIS

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

[Source g]

Desired neutron activation

Rescattered, breakup neutrons

[Walk]

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

2035 keV(74Ge)

2040.7 keV (from E*(1+,2+) = 3951 keV)

Ge Spectra

2035 keV(74Ge)

2040.7 keV (from E*(1+,2+) = 3951 keV)

Ge Spectra

2035 keV(74Ge)

2040.7 keV (from E*(1+,2+) = 3951 keV)

Xe Spectra

J. Bradt et al., 2012

Future Work

• Obtain estimates of total cross sections• Apply scheme in full to natGe and 136Xe