Presentation on theme: "Large Area, Low Cost PMTs Neutrinos and Arms Control Workshop Paul Hink 6 February 2004 BURLE INDUSTRIES."— Presentation transcript:
Large Area, Low Cost PMTs Neutrinos and Arms Control Workshop Paul Hink 6 February 2004 BURLE INDUSTRIES
6 Feb 2004Neutrinos and Arms Control Workshop BURLE INDUSTRIES Overview BURLE INDUSTRIES, INC. Conversion Tubes Power Tubes Real Estate BURLE ELECTRO-OPTICS, INC. BURLE INDUSTRIES GmbH BURLE INDUSTRIES UK LIMITED BURLE deMexico
6 Feb 2004Neutrinos and Arms Control Workshop Core Competencies Conversion Tubes, Lancaster PA Conventional PMT design and fabrication Photocathode processing Image tube design and fabrication PMT packaging Electronics: VDN, Miniature HVPS, Front- end electronics Power Tubes, Lancaster PA Design and fabrication of vacuum tubes for power generation and switching Plating and environmental testing Ceramic-to-Metal joining techniques BEO, Sturbridge MA Microchannel plates Channel multipliers Fiber optics
6 Feb 2004Neutrinos and Arms Control Workshop PMT Construction/Processing Electron multiplier is supported by bulb spacers and leads to the stem Envelope is evacuated through an exhaust tubulation Cathode processed in-situ with Sb and alkali dispensers Tip-off of tubulation using flame or electric oven Sb bead Alkali Channels Stem Exhaust tubulation Bulb Dynode Structure Photocathode
6 Feb 2004Neutrinos and Arms Control Workshop Manufacturing Discrete multiplier fabrication is labor intensive Materials and processes are critical Sealing of bulb to stem assembly is semi- automated Multiple PMTs can be processed simultaneously on an exhaust system Post-exhaust processing can be done in large batches Testing is semi-automated
6 Feb 2004Neutrinos and Arms Control Workshop Planacon™ MCP-PMTs Two inch square flat PMT with dual MCP multiplier. Anodes, 2x2 and 8x8 configurations. Additional configurations available. Bi-alkali cathode on quartz faceplate or cryogenic bi-alkali. Intrinsically low radioactivity
6 Feb 2004Neutrinos and Arms Control Workshop MCP-PMT Operation Faceplate Photocathode Dual MCP Anode Gain ~ 10 6 Photoelectron V ~ 200V V ~ 2000V photon
6 Feb 2004Neutrinos and Arms Control Workshop MCP-PMT Construction Faceplate Anode & Pins Indium Seal Dual MCP MCP Retainer Ceramic Insulators Cathode is processed separate from multiplier and sealed to body under vacuum
6 Feb 2004Neutrinos and Arms Control Workshop Transfer Cathode Manufacturing Large UHV chambers required Parts and materials preparation critical Movement of parts inside vacuum chamber(s) difficult Only a few PMTs can be processed simultaneously Indium sealing is reliable but expensive material costs. Alternative sealing techniques available. Can become highly automated, but large capital investments required
6 Feb 2004Neutrinos and Arms Control Workshop Photo-electron bombarded electron detector Can use Silicon detector, APD, scintillator + light detector, … Excellent single pe resolution Typically requires very high accelerating voltage Hybrid Photodetectors Faceplate Photocathode Electron Detector Photoelectron V ~ 10,000V photon
6 Feb 2004Neutrinos and Arms Control Workshop Vacuum not required Low cost envelope Excellent single pe resolution Degradation of photocathode/gas in sealed devices needs to be addressed Solid cathode must be made under vacuum Gas Electron Multipliers Faceplate Photocathode Photoelectron photon
6 Feb 2004Neutrinos and Arms Control Workshop Large Area PMT Program Selected for a DOE SBIR to develop a large area PMT Phase I began in July 2003 and has proceeded well Focus is to design a low-cost bulb that can be manufactured using automated techniques and allows the use of simple electron-optics Also investigating low-cost processing techniques
6 Feb 2004Neutrinos and Arms Control Workshop Requirements ParameterValueUnitsComments Spectral Response nmResponse < 300nm not very useful due to attenuation length in water Cathode QE at 390nm20%Desire as high as possible Collection Efficiency75%Desire as high as possible Gain1 x 10 7 Dark Counts3 - 4kcps Transit Time Spread (FWHM)5.5nsDesire 3 ns Photocathode area, head-on1700cm 2 Sized to give lowest cost per unit area High Voltage+2000VCould be higher Pressure8atmTotal outside – inside pressure difference. Could use acrylic pressure vessel if needed. PackagingVDN + HV and signal cables, hermetically sealed Chemical resistancePure H 2 O
6 Feb 2004Neutrinos and Arms Control Workshop Arms Control PMT Assumptions 4km of water (~400 atmospheres) 40% coverage on a 10Megaton detector, or ~8 x 10 4 m 2 of photocathode area Requires ~ 400,000 PMTs having 2000 cm 2 of projected area (~20” diameter) Production of 40M PMTs for 1 array, $6B at $200 per PMT ($0.10 / cm 2 ) Maintain performance of existing PMTs, including QE, Dark Counts, and Timing
6 Feb 2004Neutrinos and Arms Control Workshop Traditional PMT Approach Vacuum Envelope is critical to the performance of the PMT Envelope must withstand 400 atmospheres unless a separate pressure vessel is used, which will add cost. Window must be made out of low cost glass, resistant to ultra-pure H 2 O, low strain (low expansion Borosilicate) Remainder of the vacuum envelope can be made of glass or appropriate metal or composite. Vacuum envelope requires electrical feed-throughs for bias, signal, and processing of photocathode.
6 Feb 2004Neutrinos and Arms Control Workshop Traditional PMT Sealing Vacuum Envelope can be sealed using a flame. However, annealing temperatures are too high to be done with the multiplier and cathode processing materials in the PMT. Vacuum envelope can be welded together if appropriate flanges have been attached to the glass sections. Residual strain a problem. Low temperature glass process yields high strength bonds, but tight flatness tolerance on seal surfaces. Vacuum feed-throughs must be inserted and annealed. Minimum number of feed-throughs is desired Exhaust tubulation typically has some residual strain and will be a weak point. Could use a metal tubulation
6 Feb 2004Neutrinos and Arms Control Workshop Multiplier Selection Standard discrete dynode structure is hard to automate and labor intensive. Spherical bulb, while strongest, is not ideal for good timing performance. Electron Optics design work required Silicon detector or APD has the fewest feed-throughs required Micro-channel plate multiplier is simple and also has fewer feed-throughs. In high volume may approach the cost of silicon detectors.
6 Feb 2004Neutrinos and Arms Control Workshop Example of Spherical PMT Schott produces hemispheres of size needed Sealed with low temperature process 18mm wall good to >4km depth Silicon electron detector preferred APD FocusElement Photoelectron Glass Hemisphere Tubulation Leads
6 Feb 2004Neutrinos and Arms Control Workshop Example Fabrication Flow Glass hemispheres are formed out of a melt Sealing surfaces are machined to high tolerance Feed-throughs are installed in one hemisphere Both hemispheres are annealed Multiplier/Detector, electron optics, and process materials are installed on rear hemisphere Low temperature glass-to-glass seal of two halves Tube is exhausted and processed Tubulation is tipped-off PMT is aged and tested
6 Feb 2004Neutrinos and Arms Control Workshop Design Challenges High precision machining of the hemisphere seal surfaces (few microns) Installation of electrical feed-throughs and tubulation Annealing the rear hemisphere to remove all strain Exhaust and processing of tube needs to be automated with no handling of PMTs between processes.
6 Feb 2004Neutrinos and Arms Control Workshop Feasibility of this Design Requires significant glass manufacturing capabilities. At 28kg per bulb, three 1Gton arrays, and 15 years to manufacture, ~8 large glass lines (100,000 kg/day/line) would be required. Raw glass cost could be ~$15 per bulb. Hemispheres could be pressed/molded out of the melt or vacuum formed out of float glass. Precision machining and grinding of seal surfaces would need to be highly automated All basic technologies are developed, but requires development of automated processing
6 Feb 2004Neutrinos and Arms Control Workshop Alternative Design Alternative designs could provide lower manufacturing costs, but have some technology developments associated with them. Transfer design could be lowest cost per unit, but may have higher capital requirements. The pressure requirement drives all designs.
6 Feb 2004Neutrinos and Arms Control Workshop Conclusions PMTs for < $0.10/cm 2 photocathode area are not limited by existing technology Manufacturing and processing techniques require significant R&D Can learn from picture tube and semiconductor industries Questions about business strategies in responding to this opportunity. Partnering opportunities Government involvement Concerns about limited lifetime of project