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

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Presentation on theme: "Long Lifetime CW H- Ion Source for Project X Fermi National Laboratory July 11, 2013 Evan Sengbusch, PhD Joe Sherman, PhD Preston Barrows Daniel Swanson."— Presentation transcript:

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

2 Project X Requirements and Proposed Solution > 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 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 2 Microwave Ion Source + Cesium Converter Magnetron Autotuner Waveguide Break Ground -30 kV Plasma Chamber Magnetic Filter Cesium Converter Beam Extraction Faraday Cup/ Diagnostics Ground

3 Phoenix Nuclear Labs Founded in 2005; 14,000 ft 2 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 3x10 11 n/s (D-D) CW and anticipates a 5x10 11 n/s demonstration in 6-12 months Funded primarily by VCs/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 IEDs 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. 3

4 PNL High-Flux Neutron Generator Technology base: 300 kV deuterium beam incident on deuterium or tritium gas target Up to 5x10 11 DD n/s or 5x10 13 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 4

5 PNL Neutron Generator Methodology 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 P-II

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 6 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 PNL Ion Source

7 Medical Isotope Production 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 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 (5x10 13 DT n/s each) will be delivered to the SHINE isotope production facility and will be maintained and serviced by PNL

8 Neutron Radiography 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 8 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 Neutrons X-Rays

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 – PNLs 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 – PNLs high neutron yield could allow this important measurement technique to take place in laboratory/factory settings 9 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 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 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

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 ( ) 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 (kT e ) in the driver region, and effective kT e reduction in the H0 converter. – Observation of hyperthermal H0 (kT H0 > 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. 11

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 12

13 Production of Hyperthermal H0 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 Hyperthermal H0 defined as H0 energies > 1eV. High electron temperature H 2 plasmas leads to direct H 2 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.

14 Cross Sections and Reaction Rates for Hyperthermal H0 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 Following discussion in Brian Lees thesis (Stevens Institute, 1993): Dissociation cross section Reaction rate

15 Microwave Proton Source (MWS) as Driver for Hyperthermal H0 15 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 Neutrons X-Rays What do we know about the MWS from H + production (CRL, LANL)? kT e ~ 20eV (from Chalk River Lab Langmuir probe measurements) J + = 0.26A/cm 2 N e = 1.2 X e/cm 3 N(H 2 ) = 7.1 X H 2 /cm 3 (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 N e N(H 2 ) V = n Ho v Ho A/(4 ) H0 = n H0 v H0 /4 = 6.6 X H0/(cm 2 -s) (MWS) *Interesting observation: Based on 4.1sccm H 2 flow rate in LANL MWS the neutral flux density effusing from the MWS is 4.7 X neutrals/(cm 2 -s) -> all H 2 dissociated to H0! For 20% conversion efficiency (H0 -> H - ), 15% solid angle efficiency, j H- = 24mA/cm 2 r emis = 0.4cm, I H- = 12mA, rms,n = (r emis /2)(kT H- /mc 2 ) 1/2 =.065 ( mm-mrad), kT H- = 1eV No optimization of MWS for H0 production assumed, or, possible contribution to H - production from slow positive ions.

16 Proposed Driver – H - Production Regions Classic Two Chamber H - 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 16 H0 generator is MWS Dipole filter for reducing hot electrons Cesiated molybdenum converter (H0 -> H - ). Cone exit aperture radius = 0.5cm Plasma electrode has r emis = 0.4cm

17 30kV H - Extraction System 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 PBGUNS simulation using H - plasma meniscus option. 10mA extracted current. Extraction gap = 27.2mm, emission aperture radius = 4mm, extraction aperture radius = 3.2mm kT H- = 1eV, rms,n (PBGUNS) = 0.10 ( mm-mrad) Co-extracted electrons separated from H - beam after extraction electrode by a dipole separation magnet.

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 18

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 19

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 20

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 21

22 Ion Source Chemistry Higher work function materials have lower conversion probability. Mo: eV W: eV Cs: 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. Negative ions can be generated by surface ionization of hydrogen ions and atomic hydrogen. [3] H + + 2e - H - H + e - H - 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 (Cs 2 CrO 4 ), zirconium and aluminum. Production and release of pure Cs. Temperature driven rate above 625 o C 4 Cs 2 CrO Zr 8 Cs(g) + 5 ZrO Cr 2 O 3 6 Cs 2 CrO Al 12 Cs(g) + 5 Al 2 O Cr 2 O 3 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 lter eld 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 25

26 Magnetic Design - Filter 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 filter axial profile Magnetic filter field lines

27 Thermal Design o C 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, o C. Heated/cooled by pressurized air loop with inline heater. H - ion production rate dependent on surface temperature, optimum around o C. 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 27

28 Thermal Simulations 300 W cartridge heaters, 100 o C air500 W plasma heating, 100 o C 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 28

29 Mechanical Design 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 Faraday cup/ calorimeter Pumping stage Cs converter Magnetic filter Plasma chamber DC Waveguide break Autotuner Circulator Magnetron Ground -30kV 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. Ground

30 Diagnostic Techniques 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 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.

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 31 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

32 H 0 Calorimeter 32 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 H 0 Calorimeter 33 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 34 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 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 35 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 monochromator needs 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

36 Optical Spectroscopy 36 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 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 37 Neutrons X-Rays 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. 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

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 39 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

40 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

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 42

43 QUESTIONS? Evan Sengbusch, PhD, MBA (608)

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 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 PM instead of electromagnet driver source. Better control of kT e 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.


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