Recent content by DBO

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    Lightning Strikes and Conductive Sea Water: Exploring the Effects on Marine Life

    As a long time sailor who lives in FL and am frequently in thunderstorms, I am very careful about it. A lone sailboat under s t-storm has a pretty good chance of getting hit (I forget the numbers). A Dynaplate will not work. You need an actual copper plate. Mine is 2' X 2' X .025"connected...
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    I Raytracing Programs: Find Under $1000 | Fritz

    Try Beam 6, it is shareware. If you have money you could buy OptiCad for about $2850
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    B Why does a U-238 tamper increase nuclear yield of nuclear bomb?

    The tamper has sufficient inertia that it holds the core together for a tiny greater fraction of time allowing more neutron multiplication thus increasing yield.
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    Electron gun in a vacuum -- How hard of a vacuum is needed?

    My electron microscope will not turn the beam on till it hits 3 mTorr and it continues to pump till it reaches a several times XE-6 Torr. At 1E-6 Torr, it still "cracks" background hydrocarbons onto the sample making a black spot. The questioner should read about the Paschen Curve about...
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    What do the tick marks on closed contours indicate?

    Closed contours that represent depressions have tick marks on the downhill side. This is only true of closed contours. You can see such features on karst features such as sinkholes. Being a caver, I often peruse topo maps online for such features to find caves. You can find many such...
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    Free Falling powder in a vacuum

    I agree that you need a better vacuum. Charging of the dust particles is definitely an issue and you might consider using this to sort particles by size. You could even put in a UV lamp to increase the particle charging.
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    North Magnetic Pole wandering away

    Magnetic compass is my primary nav tool on my sailboat so I need to account for declination. Here in the Gulf of Mexico it isn't too much but in the Bahamas its over 10 degrees
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    Seeking Thermal Insulator & Electrical Insulator for Peltier Device

    Your epoxy is electrically conductive? That's weird. Try Torr-Seal, expensive but viscous and non-conductive and excellent in vacuum. You also might try that stuff advertised on late night that is a glue material that is cured with a UV LED. Put in on upside down, cure it and then right side up.
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    B Radiation shielding and redirecting

    OOOps, should have been 10E14 watts/cm2 incident then 10E12 watts/cm2 is absorbed. BTW, just out of interest, index of refraction for x and gammas is less than 1 and has a major imaginary part corsponding to absorption.
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    B Radiation shielding and redirecting

    Unfortunatly, the most x-ray and gamma ray reflective materials are high Z and high density materials such as gold or Tungsten, etc. Because the number of reflections to direct a beam around an object is so high, the total absorption is also very high. You are better of using normal lead...
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    B Radiation shielding and redirecting

    X-ray optics just happens to be my field and by extension, gamma ray optics. Short answer about redirecting very short wavelength radiation.....Its really hard but not impossible. For most such energies, reflectivities are so low that you effectively just absorb the radiation. You could do it...
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    Detect Single Electron: Fuji-Film & Kodak-Film?

    Somebody mentioned the Millikan oil drop experiment as being a standard for physics students and I bet few have done it. It is actually an extremely difficult experiment to do as it involves squinting thru a microscope for hours and finding just the right droplets and timing them with a...
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    Detect Single Electron: Fuji-Film & Kodak-Film?

    Instead of a channeltron, use the MCP followed by a scintillator followed by a cheap cooled amateur astronomy ccd camera. This will give very good position sensitivity and will actually work. Needs one 0-2 KV low noise power supply, an MCP, a scintillator, camera. All can be had for about $4000.
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    Detect Single Electron: Fuji-Film & Kodak-Film?

    A Channeltron or MCP would be best to use here. The channeltron gives huge gain and minimal complexity while the MCP followed by a phosphor and then CCD gives high gain and position sensitivity.
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    Ball Lightning Discussions/Anecdotes?

    While riding a bicycle after a T-storm, lightning hit the road right in front of me. I fell off the bike in surprise. There was a large circular dry spot but no fulgerites. Sitting by my computer at home during a T-storm, a large spark jumped from the computer to the outlet on the wall but...
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