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Long Lifetime CW H- Ion Source for Project X

Long Lifetime CW H- Ion Source for Project X. Fermi National Laboratory July 11, 2013. Preston Barrows Daniel Swanson. Evan Sengbusch, PhD Joe Sherman, PhD . Project X Requirements and Proposed Solution. Microwave Ion Source + Cesium Converter. Magnetic Filter.

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Long Lifetime CW H- Ion Source for Project X

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  1. Long Lifetime CW H- Ion Source for Project X Fermi National Laboratory July 11, 2013 Preston Barrows Daniel Swanson Evan Sengbusch, PhD Joe Sherman, PhD

  2. Project X Requirements and Proposed Solution Microwave Ion Source + Cesium Converter Magnetic Filter • > 10 mA CW H- beam current • Beam emittance < 0.2 pi-mm-mrad at RFQ entrance • Extracted at 30 kV • Lifetime > 1 month (4-6 months preferred) • High gas efficiency • Hi power efficiency Cesium Converter Plasma Chamber Beam Extraction -30 kV Ground Ground Waveguide Break Faraday Cup/ Diagnostics Autotuner Waveguide Magnetron Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  3. Phoenix Nuclear Labs • Founded in 2005; 14,000 ft2 lab (including two shielded bunkers) located in Madison, WI • Multidisciplinary team of PhD scientists, engineers (nuclear, electrical, mechanical), and technicians • PNL core mission is to design, build, and commercialize high flux neutron generators • PNL has demonstrated neutron production of 3x1011 n/s (D-D) CW and anticipates a 5x1011 n/s demonstration in 6-12 months • Funded primarily by VC’s/angels and several DoD /DoE contracts: • $50M NNSA cooperative agreement - isotope production • 4 DoD Contracts – Neutron radiography, IED detection, nuclear survivability, and neutron diffraction • DoE – Ion source development for high energy physics • JIEDDO – Pending contract to study stand-off detection of IED’s Confidentiality statement: This document is the joint property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as jointly authorized by PNL.

  4. PNL High-Flux Neutron Generator • Technology base: 300 kV deuterium beam incident on deuterium or tritium gas target • Up to 5x1011 DD n/s or 5x1013 DT n/s emitted isotropically • Key innovations: • Gaseous target increases neutron yield and device lifetime • Very high current achieved by novel ion source and beam extraction design • 2 prototypes have been built and are operating • P-I: Radiography system (US Army) • P-II: Medical isotope production (Nat Nuclear Security Admin) • 2 in design phase • P-III: IED detection (US Army) • P-IV: Medical isotope production (Nat Nuclear Security Admin) Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  5. PNL Neutron Generator Methodology P-II Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  6. PNL Microwave Source Performance • 122 hour (99.99% uptime) CW operation demonstrated at 50 mA, 45 kV • > 90 mA deuterium extracted at 260 kV 60kV, 65mA Beam on calorimeter PNL Ion Source Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  7. Medical Isotope Production • PNL is a subcontractor on a $50M+ cooperative agreement with the National Nuclear Security Administration (NNSA) and SHINE Medical Technologies for domestic production of the medical isotope Moly-99 • Moly-99 is used by 55,000 patients each day in the US for nuclear medicine procedures • US Gov has made a non-HEU domestic source of Moly-99 a high priority • Eight subcritical fission assemblies, utilizing an aqueous solution of LEU, will each be driven by the PNL intense neutron generator to produce half of the total global demand for Moly-99 • Starting in 2016, 8 neutron sources per year (5x1013 DT n/s each) will be delivered to the SHINE isotope production facility and will be maintained and serviced by PNL Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  8. Neutron Radiography Neutrons • Orders-of-magnitude increase in neutron yield allows for practical implementation of non-reactor thermal neutron radiography for: • Artillery shells – system delivered to US Army • Critical aircraft and spacecraft components • Composite materials • Fast neutron radiography is of interest for cargo screening at sea- and airports • Requires high neutron yield to be practical • Provides elemental information complementary to X-rays • Dual X-ray/Neutron radiography systems being implemented in China, Australia (CSIRO/NuTech) • Rapiscan recently requested information about the PNL neutron source for fast neutron radiography X-Rays Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  9. Component Testing & Evaluation • Army Phase I SBIR has been awarded to PNL to evaluate using PNL neutron generator to irradiate critical components • Air and spacecraft operate in high-radiation environments and must be tested and hardened • Current testing done at HEU-based reactors – high cost and security/regulatory burden • PNL’s neutron source can simulate nuclear environments without HEU • Air Force Phase I SBIR has been awarded to PNL to evaluate aircraft components using neutron diffraction • Neutron diffraction is a proven technique for bulk residual stress analysis • Presently only available at reactors and spallation sources • PNL’s high neutron yield could allow this important measurement technique to take place in laboratory/factory settings Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  10. Neutron-Based IED/SNM Detection • Neutrons interact with explosive elemental constituents or fissile material • High energy gamma rays and/or neutrons are emitted and detected to signal the presence an IED or SNM • With very intense sources, detection is possible at operationally significant standoff distances; elemental composition information available also • PNL is being funded by the Army and JIEDDO to miniaturize its neutron generator for mobile and/or vehicle-mounted detection Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  11. Ion Source Overview • Technical - historical account of Stevens Institute (Hoboken, NJ), and their analysis of H- production by hyperthermal H0 on cesiated molybdenum surface (1993). • Review of LEDA (LANL) H+ injector performance (1993-2002) based on the microwave proton source (MWS), and why this source appears to be an excellent cw H0 driver for cesiated converter source. • Simulation for 10mA, 30keV H- beam extraction. Meets Project X requirements. • Practical realization of long lived H- source. • Uses experience from the Chalk River Lab and the Los Alamos LEDA MWS technology. • This H- source is based on the U.S. Spallation Neutron Source (SNS) Cs converter, the Lawrence Berkeley National Lab (LBNL) magnetic filter, and the Cs H- converter technology from Novosibirsk. • Third talk is on H- source design details. (Preston Barrows) • Confirmation of MWS plasma properties optimal for Cs converter H- production • High electron temperature (kTe) in the driver region, and effective kTe reduction in the H0 converter. • Observation of hyperthermal H0 (kTH0 > 1eV). • High H0 flux from MWS driver. • H- beam current and noise characteristics. • Fourth talk is on H- source diagnostics. (Dan Swanson) Confidentiality statement: This document is the joint property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as jointly authorized by PNL.

  12. Theoretical H- Yield from H0 on W(Cs) • Solid line is theory from H. L. Cui, J. Vac. Sci. Technol. A9, 1823 (1991). • H0 thermal energy measurements (solid dots) from S. T. Melnychuk and M. Seidel, J. Vac. Sci. Technol. A9(3), 1650 (1991). • kT is H0 temperature. • Work from Stevens Institute of Technology, Hoboken, NJ. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  13. Production of Hyperthermal H0 • Hyperthermal H0 defined as H0 energies > 1eV. • High electron temperature H2 plasmas leads to direct H2 dissociation to hyperthermal H0. • The electron energy threshold for direct dissociation of state II in the adjoining figure is 8.8eV. • The minimum dissociation energy of state II is 2.2eV. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  14. Cross Sections and Reaction Rates for Hyperthermal H0 Following discussion in Brian Lee’s thesis (Stevens Institute, 1993): Dissociation cross section Reaction rate Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  15. Microwave Proton Source (MWS) as Driver for Hyperthermal H0 • What do we know about the MWS from H+ production (CRL, LANL)? • kTe ~ 20eV (from Chalk River Lab Langmuir probe measurements) • J+ = 0.26A/cm2 • Ne = 1.2 X 1012 e/cm3 • N(H2) = 7.1 X 1013 H2/cm3 (molecular flow) • H+ fraction 90% at ~ 1 kW 2.45GHz microwave power • Continuity equation for H0 flux based on volume production (V) and surface (A) loss • NeN(H2)<sve>V = nHovHoA/(4a) • fH0 = nH0vH0/4 = 6.6 X 1018 H0/(cm2-s) (MWS) • *Interesting observation: Based on 4.1sccm H2 flow rate in LANL MWS the neutral flux density effusing from the MWS is 4.7 X 1018 neutrals/(cm2-s) -> all H2 dissociated to H0! • For 20% conversion efficiency (H0 -> H-), 15% solid angle efficiency, jH- = 24mA/cm2 • remis = 0.4cm, IH- = 12mA, erms,n = (remis/2)(kTH-/mc2)1/2 = .065 (pmm-mrad), kTH-= 1eV • No optimization of MWS for H0 production assumed, or, possible contribution to H- production from slow positive ions. Neutrons X-Rays Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  16. Proposed Driver – H- Production RegionsClassic Two Chamber H- Source • H0 generator is MWS • Dipole filter for reducing hot electrons • Cesiated molybdenum converter (H0 -> H-). Cone exit aperture radius = 0.5cm • Plasma electrode has • remis = 0.4cm Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  17. 30kV H- Extraction System • PBGUNS simulation using H- plasma meniscus option. 10mA extracted current. • Extraction gap = 27.2mm, emission aperture radius = 4mm, • extraction aperture radius = 3.2mm • kTH- = 1eV, erms,n (PBGUNS) = 0.10 (pmm-mrad) • Co-extracted electrons separated from H- beam after extraction electrode by a dipole separation magnet. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  18. Expected H- Source Lifetime • MWS discharge (2.45GHz, 875G ECR) can run very long time in cw mode (months). PNL has gained expertise in reducing EMI while developing 300keV positive ion accelerators. • The MWS is most gas and power efficient cw H+ source known. • PNL H- injector design will place most sensitive electronics at ground level, thus minimizing EMI problems (minimal equipment on 30kV deck). • Recent work at the U.S. Spallation Neutron Source (SNS) has indicated a single cesiation of the converter cone may last two weeks or more without detriment to H- production. For this reason, the PNL design follows the SNS converter developments as closely as possible. The Cs oven proposed here will contain enough Cs for many Cs applications. • There is good reason to suspect that the proposed source could operate at 10mA, 30keV in cw mode for several months. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  19. Ion Source Design Overview Plasma source Filter magnet Cesium converter Beam Extraction Beam diagnostics Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  20. Design Goals Stable ECR plasma driver capable of producing high density and high temperature plasma for long run times. Adjustable electron temperature in Cs conversion region by use of filtering magnets. Efficient conversion of high temperature H+ ions and neutrals into H- ions though surface reactions with low work function materials. Extraction and acceleration of high quality beam. Incorporation of diagnostic instruments. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  21. Magnetic Design - Driver Frequency of cyclotron motion given by For 2.45 GHz microwaves and electrons, resonance match when B = 875 G [2] Best performance when resonance zones located near front and rear of plasma chamber. Field leakage outside driver reduced with iron/steel shunts. Minimize B in waveguide to reduce unwanted ionization. Minimize axial B in conversion region to improve magnetic filtering. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  22. Ion Source Chemistry • Negative ions can be generated by surface ionization of hydrogen ions and atomic hydrogen. [3] • H+ + 2e- → H- • H+ e- → H- • Higher work function materials have lower conversion probability. • Mo: 4.36-4.95 eV • W: 4.32-5.22 eV • Cs: 1.8 - 2.14 eV • Cesium work function as low as 1.3 – 1.7 eV at thickness of about 0.6 monolayers. [1] • Low binding energy (0.75 eV) of additional electron is beneficial to neutralization, but also makes H- ions vulnerable. • Plasma parameters and background gas in conversion section are critical. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL 22

  23. Cesium Source • Commercially available alkali-metal dispenser. • Cesium is stored in a stable chemical compound. • Controlled release of pure Cs through decomposition reaction of compound and reducing agent. • SAES Cs dispenser contains cesium chromate (Cs2CrO4), zirconium and aluminum. • Production and release of pure Cs. Temperature driven rate above 625 oC • 4 Cs2CrO4 + 5 Zr→ 8 Cs(g) + 5 ZrO2 + 2 Cr2O3 • 6 Cs2CrO4 + 10 Al → 12 Cs(g) + 5 Al2O3 + 5 Cr2O3 • Impurity management critical due to high chemical reactivity of cesium with residual gas. • Cesiated surface electrically biased ~-100 V to promote deposition. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL 23

  24. H- Converter and Extraction Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL 24

  25. Magnetic Design - Filter A magnetic filter field cools the plasma before converter surface to reduce the destruction of negative ions by electron stripping. Electron temperature of ~10 eV in driver. Target electron temperature of 2 eV at converter surface. Difficulty: high-permeability plasma aperture plate to contain driver fields tends to shunt filter magnet away from desired location. Aperture chamfered to add distance between plate and filter while still containing driver fields. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  26. Magnetic Design - Filter Magnetic filter field lines Magnetic filter axial profile Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  27. Thermal Design 295-625 oC minimum temperature for cesium dispenser, depending on compound. Cesium dispensers driven by small cartridge heaters or direct current. Thermally isolated with stainless or ceramic standoff. Cesiated surface cooled to selectively enhance deposition rate, 20-200 oC. Heated/cooled by pressurized air loop with inline heater. H- ion production rate dependent on surface temperature, optimum around 150-200 oC. Plasma heating effects to be determined experimentally and adjusted for if necessary. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  28. Thermal Simulations 300 W cartridge heaters, 100oC air 500 W plasma heating, 100 oC air Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  29. Mechanical Design • Driver and converter floated to -30 kV. • Microwave hardware, diagnostics, and driver solenoids at ground. • Use proven and existing PNL technology when possible. • Modular design. • Simple dis/assembly. • Inclusion of diagnostics. • Flexibility for contingency plans. Cs converter Plasma chamber DC Waveguide break Magnetic filter Pumping stage -30kV Ground Ground Autotuner Circulator Faraday cup/ calorimeter Magnetron Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  30. Diagnostic Techniques Calorimeter Atomic Flux Measurements to confirm the flux from the Driver is high enough. Faraday Cup Beam Current and Noise Measurements for assisting in determining the necessary strength of the filter magnet. Video Camera Mounted on the conflat cross Used for Beam Profile Measurements to visually verify the cross section of the beam. Optical Spectroscopy Plasma Density and Temperature Measurements to further help understand the plasma source and possibly detect impurities. Langmuir Probe Plasma Velocity, Temperature, and Flux Measurements to further assist in determining the necessary filter magnet strength. Confidentiality statement: This document is the joint property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as jointly authorized by PNL. 30

  31. Faraday Cup • Background • Measure 30keV H- current; electron suppressor either electrostatic and/or magnetic (Electrostatic Shown) • Beam noise measurement; expect bandwidth ~ 10 MHz • Working with e/H- separation magnet (located immediately after 30kV extractor), deduce e/H- ratio • Faraday Cup entrance aperture diameter (molybdenum plate) designed on the basis of the PBGUNS predicted divergence, and known drift distance to the Faraday Cup entrance Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL 31

  32. H0 Calorimeter Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  33. H0 Calorimeter Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  34. Beam Profile Measurement • Design Concept • Mounting a Video Camera on the conflat cross for viewing the beam profile • There is a Window on the conflat cross for the Camera to view the beam through without being damaged • We can assume we have an axisymmetric beam, so one Video Camera is sufficient • If the coextracted electrons are seperated from the H- beam in the horizontal plane, it would be interesting to mount the camera in the vertical plane so the seperation of the two beams would be visible 34 Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  35. Optical Spectroscopy • Background • Used for Plasma Density and Temperature Measurements • Can also be used for detecting impurities and leaks in the system • The change in wavelength at fwhm of an emission peak is due to Doppler broadening • For the 656nm hydrogen line, this is about .15nm for 10eV and .05nm for 1eV. • The resolution of the monochromatorneeds to be below these values. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL 35

  36. Optical Spectroscopy • Light input options • Lenses • Potential exists for better performance • Can require more sophisticated mounting and alignment hardware • Needs transmission through a vacuum window and guarding against stray light • Monochromator needs to be physically located as close to the vacuum wall as possible • Fiber Optics • No need to set and maintain precise alignment of components • Vacuum feedthru is a stock part and creates no concern of external light noise 36 Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  37. Optical Spectroscopy Data Collection Classical Monochromator Has a single detector which measures the intensity of a single wavelength of light over time. Single wavelength is selected by mechanically shifting elements. This style is slower but has better resolution in .01 nm or better. Extra resolution provided here is not necessary for this application. Newly designed CCD collector Samples the entire available spectrum at once. Faster data collection is limited only by the required exposure time. Faster feedback allows for easier characterization of source plasma temperatures over a wide range of operating parameters. Neutrons X-Rays Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL 37

  38. Langmuir Probe • Types of Probes Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  39. Langmuir Probe Design Choice • Single Cylindrical Probe • Linear Feedthru • Glass Tube for the insulating material • Alumina for the main probe section • Tungsten Wire for data collection Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL 39

  40. Langmuir Probe • Theory • Single Cylindrical Probe • ] • » • can be found from the slope of vs. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL 40

  41. Diagnostics Summary • Multiple Diagnostic Tools being used • Calorimeter • Video Camera • Faraday Cup • Optical Spectroscopy • Langmuir Probe • Multiple Values to be obtained • Atomic Flux • Beam Current, Noise, and Profile Measurements • Plasma Density, Temperature, and Velocity 41 Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  42. Conclusions • PNL has demonstrated high current, long lifetime CW operation with a positive deuterium microwave ion source • There is a good reason to believe that coupling this source with a Cs conversion cone will result in a high performance CW H- source with a long lifetime • Preliminary designs have been completed • Next step is pursuit of Phase II SBIR funding to build and test the H- ion source Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  43. QUESTIONS? Evan Sengbusch, PhD, MBA (608) 210-3060 sengbusch@phoenixnuclearlabs.com

  44. References [1] Handbook of Ion Sources, Bernard Wolf, CRC Press, Inc., 1995 [2] NRL Plasma Formulary, Naval Research Laboratory, 2011 [3] Work function measurements during plasma exposition at conditions relevant in negative ion sources for the ITER neutral beam injection, R. Gutser, C. Wimmer, and U. Fantz, 2011 [4] Fusion Physics, IAEA, 2012 Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

  45. Contingency Planning – Identify Design Areas That Could Be Challenging • PM instead of electromagnet driver source. Better control of kTe in the converter region and Cs oven temperature control. May have complications of the electromagnet and dipole filter fields. • Modification to Cs oven, converter cone, and tube for: • Thermal loading surprises • Hyperthermal H0 incident angle on Cs converter cone • Coextracted electron dump options • Weak or strong dipole magnet after 30keV beam formation? Present design is for weak field so H- beam direction correction is minimal. Preferred option. • Dump coextracted electrons on electrode with intermediate potential. Seems unattractive for cw beam reliability to dump electrons in the extraction field. Confidentiality statement: This document is the property of Phoenix Nuclear Labs and may not be copied, used, or disclosed for any reason except as authorized by PNL

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