large area, low cost pmts

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Large Area, Low Cost PMTs Neutrinos and Arms Control Workshop Paul Hink 6 February 2004 BURLE INDUSTRIES BURLE INDUSTRIES

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Large Area, Low Cost PMTs. Neutrinos and Arms Control Workshop Paul Hink 6 February 2004. BURLE INDUSTRIES. BURLE INDUSTRIES Overview. BURLE INDUSTRIES, INC. Conversion Tubes Power Tubes Real Estate BURLE ELECTRO-OPTICS, INC. BURLE INDUSTRIES GmbH BURLE INDUSTRIES UK LIMITED - PowerPoint PPT Presentation

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Page 1: Large Area, Low Cost PMTs

Large Area, Low Cost PMTs

Neutrinos and Arms Control Workshop

Paul Hink

6 February 2004BURLE INDUSTRIESBURLE INDUSTRIES

Page 2: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos and Arms Control Workshop

BURLE INDUSTRIES Overview

BURLE INDUSTRIES, INC.Conversion TubesPower TubesReal Estate

BURLE ELECTRO-OPTICS, INC.BURLE INDUSTRIES GmbHBURLE INDUSTRIES UK LIMITEDBURLE deMexico

Page 3: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

Page 4: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

Page 5: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

Page 6: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

Page 7: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos and Arms Control Workshop

MCP-PMT Operation

Faceplate

Photocathode

Dual MCP

Anode

Gain ~ 106

Photoelectron V ~ 200V

V ~ 200V

V ~ 2000V

photon

Page 8: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

Page 9: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

Page 10: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

Page 11: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

Page 12: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

Page 13: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos and Arms Control Workshop

RequirementsParameter Value Units Comments

Spectral Response 300 - 650 nm Response < 300nm not very useful due to attenuation length in water

Cathode QE at 390nm 20 % Desire as high as possible

Collection Efficiency 75 % Desire as high as possible

Gain 1 x 107

Dark Counts 3 - 4 kcps

Transit Time Spread (FWHM) 5.5 ns Desire 3 ns

Photocathode area, head-on 1700 cm2 Sized to give lowest cost per unit area

High Voltage +2000 V Could be higher

Pressure 8 atm Total outside – inside pressure difference. Could use acrylic pressure vessel if needed.

Packaging VDN + HV and signal cables, hermetically sealed

Chemical resistance Pure H2O

Page 14: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos and Arms Control Workshop

Arms Control PMT Assumptions

4km of water (~400 atmospheres) 40% coverage on a 10Megaton detector, or ~8 x

104 m2 of photocathode area Requires ~ 400,000 PMTs having 2000 cm2 of

projected area (~20” diameter) Production of 40M PMTs for 1 array, $6B at $200 per

PMT ($0.10 / cm2) Maintain performance of existing PMTs, including

QE, Dark Counts, and Timing

Page 15: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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 H2O, 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.

Page 16: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

Page 17: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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.

Page 18: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

APDAPDFocusFocusElementElement

PhotoelectronPhotoelectron

Glass HemisphereGlass Hemisphere

TubulationTubulation

LeadsLeads

Page 19: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

Page 20: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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.

Page 21: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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

Page 22: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos 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.

Page 23: Large Area, Low Cost PMTs

6 Feb 2004 Neutrinos and Arms Control Workshop

Conclusions

PMTs for < $0.10/cm2 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