# Tag Info

13

Yes. From the Voyager mission webpages: As of August 2010, Voyager 1 was at a distance of 17.1 Billion Kilometers (114.3 AU) from the sun and Voyager 2 at a distance of 13.9 Billion kilometers (92.9 AU). Voyager 1 is escaping the solar system at a speed of about 3.6 AU per year, 35 degrees out of the ecliptic plane to the north, in the general ...

5

A subtle problem you seem to overlook is that the proton-proton cross section is very small, about 0.07 barns (a barn is $10^{-28}$ square meters) at the LHC energies and not dramatically different at your lower "fusion energies". It means that at the LHC, much like at your dream machine, most of the protons simply don't hit their partners. It is not really ...

5

Yes, photomultipliers are in use in calorimeters which use Cerenkov light to detect the passage of particles. An example is in this preprint of the Castor detector at CMS in LHC. Charged particles penetrating the CASTOR calorimeter will generate showers in the tungsten absorber plates. These particle showers are sampled by using the Cherenkov effect. ...

4

What you are looking for is usually called a window, not a filter. You need to check different manufacturers to choose a material that fits your requirements, including not only light transmission but also the pressure differential, chemical inertness, temperature range, etc. Checking ARS' website, calcium fluoride (CaF2) might be what you are looking for.

3

From my experience: Single-Photon detectors: The real problem is not dark counts, but spurious counts. The shot-noise limit is $\frac{1}{\sqrt{N}}$ where N is the number of photons in the field for a coherent source (i.e a laser). Reaching the Heisenberg sensitivity of $\frac{1}{{N}}$ is very difficult to realize experimentally. Detector efficiency depends ...

3

I'll answer what I know Single-photon detectors: I've seen these referred to as "click-detectors". How accurate are they? Do they measure every single photon that eneters or only a significant fraction of them? Roughly 50 %, can be higher nowadays I believe. If I send a single photon through a fiber optic of some length, how much percentage of the ...

2

Actually, this has been done, but it's not sustainable. Wikipedia has a brief explanation: Accelerator-based light-ion fusion is a technique using particle accelerators to achieve particle kinetic energies sufficient to induce light-ion fusion reactions. Accelerating light ions is relatively easy, and can be done in an efficient manner—all it takes is a ...

1

I used an arc-welder to make thermocouples from wires like your starting materials. Your desired objective looks like some of my 'failures.' Try loading a wire in tension and then break it with an arc (i.e. heat and melt a short section.) The ends might draw to the fine diameters you're trying to achieve. I'd try using one of the welders that are designed ...

1

In fact, we already have imaged extraterrestrial planets. You can find a list here, with perhaps the most famous system being HR 8799. Of course, that quote was referring to Earth-like planets, and you can see from the list I linked that everything we've seen is more massive and further out than even Jupiter. The challenge that confronts direct imaging is ...

1

The success of the Standard model in organizing our particle data is also based on the strong interaction SU(3) color, which displays asymptotic freedom. In physics, asymptotic freedom is a property of some gauge theories that causes bonds between particles to become asymptotically weaker as energy increases and distances decrease. To get free quarks ...

1

Have a look at http://arxiv.org/abs/1009.1569. In this article Thomas Juffmann discusses some of the practical issues in doing these experiments. In principle these experiments aren't hard, but in practice there are lots of technical difficulties. For example the large molecules need to be all moving at the same velocity(i.e. the beam needs to be very cold) ...

1

Obviously if the coil linearly expands equally and uniformly in all three dimensions, the inductance has to scale in directly proportionality to the dimension. My understanding is that anything made of pure copper, no matter what you do with it, will expand equally and uniformly in all three dimensions. If you can incorporate materials with different ...

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