PowerPoint Presentation

Embedding radioactive materials intolow-temperature microcalorimeters

Some preliminary ideas and results

Michael W. RabinLos Alamos National Laboratory

D.A. Bennett4, E. Birnbaum1, E.M. Bond1, R.C. Cantor5, M.P. Croce1, J.E. Engle1, F. Fowler4, R.D. Horansky2, K.D. Irwin, K.E. Koehler1,3, G.J. Kunde1, W.A. Moody1, F.M. Nortier1, D. Schmidt2, W.A. Taylor, J.N. Ullom2, L.R. Vale2, M. Zimmer, M.W. Rabin1

1Los Alamos National Laboratory, Los Alamos, NM, USA2National Institute of Standards and Technology, Boulder, CO, USA3Western Michigan University, Kalamazoo, MI, USA4University of Colorado, Boulder, CO, USA5Star Cryolectronics, Santa Fe, NM, USA

Revised Feb 6, 2013

3

Energy resolution for X- and g-ray spectroscopyFactor of ten better than conventional semiconductor technology4

241Pu/(98.95)(99.85)(102.98)(101.06)(104.23)(103.73)Close look at spectrum for X/g NDA of Pu Quantitative analysis of isotopic compositionPreliminary results from internal round robin 3 sensors X 4 samples

MicrocalorimeterConventional sensor

Mcal 0.132 0.006TIMS 0.133 0.003Atom ratio comparison for spectrum shownExternal source

Internal sourceExternal vs. internal for a-decaying isotopesDecay products are the alpha particle and the daughter atomExternal sourceInternal source

7

Energy(keV)BranchFractionQ55931a549954560.710.29g43.599.851 x 10-47 x 10-5

First high-resolution mixed actinide Q specShows 3X increase in separation between peak centers238Pu241Am88Large microcalorimeter arrays for spectroscopy+Embedded radionuclides+Isotope production facility

10Some radioactive decays of interesta, b, electron capture

11

Also work by Loidl (CEA)Some radioactive decays of interesta, b, electron capture12

The chemical form and physical microstructure of the combination of absorber and source affects energy thermalization.Key linking science issueSome radioactive decays of interesta, b, electron capture13Some possible surrogate isotopesUse for prototyping methods for isotope encapsulation and sensor designs

Isotopes that decay solely by electron capture to the nuclear ground state of a very long lived or stable product (child) isotope.High Q is OK for prototyping.Screening is incomplete and not yet detailed enough.

14Possible methods of deposition and encapsulationAssuming you start with liquid water-based solution of radioactive materialDrying of water-based solutionyou get everything that does not evaporatecoffee-ring effectmitigated by extremely very small volumes, ~10 picoliterElectrodepositionmore selectivecodeposition of major species (e.g. Cu, Au, Bi) and ultra trace (Fe, Ho)used for Cu vias in zillions of integrated circuitsMetalurgyunfavorable phase diagramsrapid freezing from melt common to quench nonequilibrium concentrationbonding and diffusion techniques based interface metalurgy (eutectics)Surface chemistrycontrolled atmosphere, temperature, time, substratechemical reduction of salts and oxides hardselective binding to surface with custom ligandsIncorporation of aqueous source and encapsulation

Techniques for analytical picoliter dispensing under development by LANL-HP collaborationPrecise control of dispensed volume, droplet position, and final spot sizeMitigates position-dependent response of sensorsAllows us to control activity per sensorControl of physical form and chemical composition will affect energy thermalization physics in the sensors16Examples from 55Fe electrodeposition

17Recent sensors for ECS of 55Fe

18Spectral results ECS of 55Fe

commercial 55FeTaylor-made 55Felarger absorberTaylor-made 55Fesmaller absorber~54 eV FWHM19Improved spectral results ECS of 55Fe

19 eVs = 5.25 eVl1 = 8.9 eV2.35 s = 12.4 eVl2 = 47 eVh = 0.3720New sensors designsNo membrane. Easier to make. More robust.

Concluding remarks21This is the era for wide-ranging experimentation in for embedding radioactive isotopes into sensors.

Long-range plans for calorimetric spectroscopy for neutrino mass call for DE = 1-2 eV FWHMA = 1-100 Bq per pixel

which have been not yet been shown for any EC-decaying isotope.

By prototyping with 55Fe, then 163Ho we mean to try.Large high-resolution arrays + embedded radioisotopes + isotope productionX g a Q b e-X g a Q b e-ECCalorimetric electron capture energy spectroscopy combines many of these.24END