Betavoltaics: An Innovative Power Source Enabling Next Generation Low-Power Sensor and Communication Devices

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Commanding Officer NSWC Crane

Betavoltaics: An Innovative Power Source Enabling Next Generation Low-Power Sensor and Communication Devices

Tom Adams, PhD

August 25, 2015

Dr. Adam Razavian, SES Technical Director NSWC Crane


Current Situation

  • Longevity of sensors & battery powered devices are severely limited by temperature, chemical instability and integrity issues associated with
  • High risks & cost in replacing device or battery.
  • Interfacing betavoltaics with electronics not well understood.
  • Betavoltaic powered devices have not been demonstrated.
  • Defense Science Board recommended the vigorous investment of $25M / year over 5 ARPA-e solicitation betavoltaic development.



  • Power sensors & devices with betavoltaic battery hybrid source
    • Ultra low power electronics
    • Long-operating lifetimes (>20 years)
    • Wide temperature range (-60°C to 150°C)
  • Many uses of radioisotopes
    • Smoke detectors, exit signs, watches, gun sights, space exploration, paint, . . .
  • Benefits
    • New capabilities & applications never imagined
    • Mitigate risks to Warfighter
    • Increased situational awareness
    • Significant cost savings


Ragone Plot




  • Meeting power budget
  • Betavoltaic manufacturers
  • Regulatory handling and licensing
    • Obtaining NRMP and approved facility
    • Defer risk to off-site NRC facility at Purdue University
  • Domestic radioisotope inventory
  • Power requirements specific to batteries
  • Perception of radioisotopes


Theory of Operation

 Similar to a solar cell

  • Radiation source
  • P-N junction
  • Charge collectors
  • Two modes of operation: constant current or constant voltage
  • Maximum Power, Vm & Im, is the optimal point of operation
  • As temperature increases, voltage and power decreases


Betavoltaic History

  •  1953: Paul Rappaport
    • First to develop betavoltaics
    • Sr90-Y90 radioactive beta sources
  • 1968-1974: Larry Olsen
    • Betacel Model 400
    • 400 µW, 4% efficient, 0.025 mW/cm3
    • Pm-147 source, 2.6 year half-life
    • No degradation
    • Successfully implanted pacemakers in over 285 patients, 60 in US
    • Lithium batteries eventually cornered
  • Present: Two manufacturers
    • Peter Cabauy, City Labs
    • Chris Thomas, Widetronix


Status of Betavoltaic Technology

  • Widetronix (
    • Firefli, Tritium and Nickel-63 versions
    • SiC semiconductor
    • Voc =2.0V
    • NRC specific license
    • No performance data available
  • City Labs (
    • NanoTritiumTM
    • III-V semiconductor
    • Voc = 8V
    • NRC general license
    • Some performance data available


Beta Source Considerations

  • Betas are emitted isotropically in a spectrum
    • The average is 30% of maximum
    • Peak shifted to lower energy due to drag from the attraction between the positively charged nucleus and negatively charged beta particle
    • Bremsstrahlung radiation
  • Beta energy greater than 300 keV can damage p-n junction
  • Tritium, 300 nm optimal in titanium
    • MC-SET (Monte Carlo Simulation of Electron Trajectories)


Radioisotope Availability and Selection 





Eavg (keV)

Specific Density Ci/g  

T1/2 (yrs)


Power in 1 Ci


Power, 10% efficiency










Tritium 5.7 keV/β 9,664 12.3 0.0338 mW 0.0034 mW $ 4 295,942 $1,183,768
Ni-63 17.1 keV/β 59.2 100.1 0.1014 mW 0.0101 mW $ 4,000 98,647 $394,589,414
Pm-147 65.0 keV/β 600 2.6 0.3853 mW 0.0385 mW $ 1,000 25,952 $25,951,842


  • Beta energy <300 keV to prevent semiconductor lattice damage
  • Tritium (H-3), Available from Canada and Potential US supply from SRNL
    • No gammas, low shielding requirements
    • Stored as a solid in metallic film (TiT2 and ScT2) on foil substrate
  • Nickel-63, Only available from Russia, but can be produced in HFIR at ORNL
    • Low flux and high gammas due to impurities and other nickel radioisotopes
    • NiCl or NiNO deposited on foil
  • Promethium-147, Only available from Russia
    • Byproduct of spent of nuclear fuel, does not occur naturally
    • Some high energy gammas from other Pm radioisotopes
    • Pm2O3 deposited on a titanium foil


Tritium Beta Emitting Source

  • Tritium is the only pure beta emitting isotope
  • Solid form as tritide is over 1000 times more concentrated than as a gas
  • Current loading process is limited and lacks control
    • Films tend to buckle and delaminate
    • Tritium pressure limited to 2 bar on actual system
    • Tritium concentrations vary film to film
  • Experiment using hydrogen and new loading system


Hydrogen Loading System (HLS)

  • Load materials with hydrogen with accurate control and high-resolution measurements
  • Resistivity measurements during loading


Hybrid Betavoltaic Design

  • Betavoltaic in parallel with Li-SS rechargeable battery or capacitor; e. betavoltaic trickle charges a battery
  • Battery
    • Li-SS for low self-discharge
  • Capacitor
    • Teflon, Tantalum polymer or aluminum polymer
  • Electrical coupling
    • Impedance on betavoltaics much higher
    • Betavoltaic voltage follows a diode I-V curve
    • Diode protection needed?


Low-Power Evaluation System

  • System designed for betavoltaic, Li-SS battery, and hybrid battery evaluations
  • Thermal Chamber
  • Digital Multimeter with Multiplexer 40-Ch, Differential
  • Source Measurement Unit
  • LabView test control console
  • Uninterruptible Power Source (UPS)



Temperature Effects

Individual performance versus temperature

Connected 6 betavoltaics in series





  • Recently, US Government agencies have identified betavoltaics as a disruptive technology that is needed and should be
    • Defense Science Board (DSB) issued its report on Technology and Innovation Enablers in 2030.  Project driven by DARPA
    • Advanced Research Projects Agency-Energy (ARPA-E) is wanting proposals for nuclear to electrical conversion in the form of betavoltaics
    • Defense Threat Reduction Agency (DTRA)and others want to investigate using betavoltaics to provide early warning of corona mass ejection events (CMEs) to protect satellites and space applications,
  • Using direct program support provides best chance of success for the technology and for the student



  • Successful operation of a betavoltaic / Li-SS hybrid battery will allow for significant extended operational mission life of existing platforms, as well as facilitate development of innovative applications not yet conceived.
  • Data acquired from betavoltaic development and evaluation represents a first and will provide designers and program managers with needed information to insert into
  • Compliance with regulations is a requirement and issue that will be investigated.
  • Public perception will change by technology demonstrations and education.
  • Technology is advancing by both Application specific funding is needed to maintain this momentum.



  • NSWC Crane
  • Purdue University, School of Nuclear Engineering and Burton D. Morgan Center for Entrepreneurship
  • City Labs, Inc
  • Widetronix
  • Savanna River National Labs


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