Questions tagged [experimental-technique]

filling in the unspecified details of elegant-sounding descriptions of experimental methods.

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35
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Double Slit Experiment: How do scientists ensure that there's only one photon?

Many documentaries regarding the double slit experiment state that they only send a single photon through the slit. How is that achieved and can it really be ensured that it is a single photon?
35
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2answers
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Are the fast axes on Thorlabs quarter-waveplates mislabeled?

Some members of my lab are performing a polarization-sensitive experiment where they need to use a quarter-waveplate (QWP) with the fast axis in a specific direction. In the process of carefully ...
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8answers
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Given fluids expand non-linearly, how were physicists able to make a linear temperature scale?

Materials expand with increase in temperature. As far as I know this property for fluids was put in use to make initial thermometers. We know that expansion of fluid is given by the following formula (...
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3answers
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How to fix a bad KF flange?

Here is an interesting question for those who are familiar with vacuum science techniques. In the attached picture we have a damaged surface of a KF flange, which comes from the turbo pump outlet and ...
23
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4answers
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How do astronomers measure the distance to a star or other celestial object?

How do scientists measure the distance between objects in space? For example, Alpha Centauri is 4.3 light years away.
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6answers
2k views

Which experiment gave scientists reason to believe nuclear fission/fusion produced energy?

Every piece of knowledge in science has a beginning lying in someone's experiment. I would like to know which experiment gave scientists the reason to believe nuclear fission/fusion existed and was ...
19
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3answers
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How should I clean a part before installing it in a vacuum system?

What are proven procedures for preparing a part that comes fresh out of the workshop for ultra-high vacuum (UHV) and extremely-high vacuum (XUV)?
18
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4answers
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How to prolong life of liquid nitrogen in hosehold vacuum flask?

I need to do some work with liquid nitrogen at home. The main question is how to store it without buying huge vacuum flask specifically for liquid nitrogen. I've tried to use usual steel household ...
16
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3answers
1k views

How can we 'see'/measure/detect particles during experiments?

I often read (high-level, conceptual) articles and news on the advances of particle physics. In these, statements are made along the lines of 'particle X splits into particles Y and Z which exist for ...
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5answers
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Is there any advantage in stacking multiple images vs a single long exposure?

Suppose I have a source object that is not time varying, to be concrete let's say it's a galaxy. Is there anything additional that can be learned or done with multiple short exposure images of exactly ...
15
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2answers
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Sun spectroscopy - Home experiment

We let the sun light run through a 5x3x3cm triangular glass prism and we examined the formed 'rainbow' in search of Fraunhofer lines. However, even though we looked close enough (even with a ...
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2answers
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Are there any inventions/applications in our world based on QFT?

Are there nowadays any actual devices or experimental applications which are based on the quantum field theory and if so, how are they related to QFT? I could not find any similar question besides ...
13
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2answers
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What's the problem with my Young slits experiment?

My Young's slits experiment doesn’t work. I mean I tried to see wave effect of light but I didn’t see any thing expect particles! I’ve sent you a pic of my laser and a short video of the experiment. ...
13
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3answers
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Measuring the effective mass

Intro: To avoid any terminology confusion, this is asked in the context of Solid State Physics and semiconductors. The canonical definition given for the effective mass is that it is related to the ...
13
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3answers
68 views

Why are binary objects so critical to astronomy?

There are a lot of astronomical objects out there to study but binary objects seem to get more attention. Why is this? What makes binary objects (stars, Kuiper Belt Objects, black holes, galaxies, ...
12
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1answer
307 views

Cleaning Already Mounted Microspheres on an AFM

I am running an experiment that uses a microsphere (Diameter ~ 50um) mounted onto the end of an AFM cantilever. I run several experiments in a row, but somewhere during a sequence, the microsphere ...
11
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2answers
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Multiple measurements of the same quantity - combining uncertainties

I have a number of measurements of the same quantity (in this case, the speed of sound in a material). Each of these measurements has their own uncertainty. $$ v_{1} \pm \Delta v_{1} $$ $$ v_{2} \pm \...
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1answer
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Laser beam alignment: best practices

I have to build a complex optical setup consisting of many mirrors, lenses, beam-splitters, multiple wavelengths lasers to be coupled, etc. I am looking for the "best practices" to efficiently (and ...
10
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2answers
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Methods to stabilize and maintain extremely low humidity in a lab environment

My atomic physics lab is in a building that experiences huge swings in humidity levels during the year due to the monsoon season Our building provides temperature, but not humidity control. Using ...
9
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1answer
613 views

Why squared mass difference between neutrino 3 and 2 is a absolute value?

why in the case of MINOS experiment (for neutrino mass detection) the squared mass difference of neutrino 3 and 2 is a absolute value(mod) compared with KamLand experiment?
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2answers
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Mechanical Equivalent of Heat

Recently I have been looking up James Joule's experiment regarding the mechanical equivalent of heat. After viewing some drawings of the apparatus, I assumed that the lines holding the weights would ...
9
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1answer
169 views

How is a standard unit divided into equally smaller or fractional units physically/experimentally?

Consider the standard unit of length: meter. How was it divided into decimeter, centimeter, millimeter, etc. when there were no shorter lengths than the standard? What is the physical/experimental ...
8
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4answers
761 views

experimental technique for measuring temperature of an ant

I am taking a course on thermodynamics. I have a question from my text(halliday & resnick,physics-1). They asked me to measure temperature of an ant or an insect or a small body,like a small robot....
8
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1answer
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How the bond angle of a water molecule is measured?

How the angle of a water molecule is measured? The bond angle for water was first determined by vibrational and rotational analysis of its infrared absorption spectra. How is bond angle extracted?
8
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1answer
932 views

How to distinguish high-energetic muons and electrons in the CMS and ATLAS muon detectors?

At a typical energy of about 100 GeV, a muon has a Lorentz factor of about 1000, an electron about 200.000. The flight time to the detector should be around 30 ns (assuming d= 10m from the collision ...
8
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2answers
262 views

How is the distance between Geneva detector and the Gran Sasso one measured?

Does anyone know how is the distance between detectors in the now famous neutrino experiment measured? Also, how was the time of flight measured?
8
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3answers
192 views

How to reproduce highway vibration?

I would like to test my hardware under vibration that can appear on a highway gantry. If someone has a model of such vibration. i.e period and amplitude. In my lab I have a motor that can be ...
7
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2answers
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How do I find the right lens for my laser?

I purchased this line laser recently and I'm running into a bit of an issue. The laser shoots out at a 120 degree angle which is perfect. However, once the laser spreads to about 4.25 inches, I need ...
7
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1answer
317 views

How would a physicist measure temperature of molten metals in 1850-1920s?

How would a physicist measure temperature of molten metals in 1850-1920s? What equipment would be used?
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3answers
820 views

Vector Boson Fusion

I have been reading about the production mechanisms for the Higgs at the LHC. It is always mentioned that for Vector Boson Fusion, the initial quarks cause jets that are back to back and with a higher ...
6
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1answer
569 views

How do we perform transverse measurements in a two level system?

In quantum mechanics any two level system can be mapped onto effective spin variables. If the system is defined by two energy levels, $|E_1\rangle$ and $|E_2\rangle$, the Hamiltonian is $$ H = \left(\...
6
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1answer
734 views

What are the “x” marks in a bubble chamber image?

Upon looking at a decent number of bubble chamber images I noticed an x shape . What particles are producing these trails?
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2answers
219 views

Why do we learn only two computations, cross sections and decay rates, in such a fundamental theory as QFT?

When I learned Newtonian mechanics I found a vast variety of computations that I could do and that was so interesting. And it was so when I learned Maxwell theory. When I started learning QFT I hoped ...
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2answers
314 views

Are there solid materials with controllable porosity?

In analogy to piezoelectric materials, where the application of an electrical field creates mechanical deformation in the material, I have the following question. Are there solid materials whose ...
6
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1answer
3k views

Liquid nitrogen and liquid helium

In cryogenics, liquid nitrogen and liquid helium are often used as coolants. Other than their low boiling point of 77K and 4.2K respectively, what properties make them suitable as coolants? Are there ...
6
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2answers
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How does one align a laser using two adjustable mirrors?

Suppose we would like to get a laser beam to pass through a particular point in space in a particular direction. At our disposal we have a laser, two adjustable mirrors (can rotate up/down and left/...
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2answers
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statistics for photon counts in photomultiplier

It seems that a common statistical model for the count numbers of a photomultiplier is a Poisson distribution whose parameter $\lambda$ equals to the square-root of the number of counts.(e.g. http://...
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0answers
225 views

How to cleave a perovskite single-crystal in vacuum?

I am trying to cleave the lead-halide perovskite in vacuum to study its intrinsic electronic properties using photoelectron spectroscopy, since it is difficult to remove surface adsorption without ...
5
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6answers
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Measuring air density - where is my huge error coming from?

I'm teaching a home-schooled 13 year old some physics and chemistry, and last night's experiment was an attempt to measure the density of air. Using an electronic balance that has proved pretty ...
5
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3answers
200 views

How are photons told apart by a PET scanner?

From what I've read, a radiopharmaceutical, such as FDG, enters a body and emits positrons that annihilate with electrons, emitting two equal gamma rays in opposite directions. Diametrically opposite ...
5
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2answers
218 views

What has been measured at the Higgs experiment and what do we know now?

Explained at the level of a 5$^{\text {th}}$ semester physics student (i.e. pre QFT, but far beyond the level of a news article for non-physicists, which avoids all details and only deals in analogies)...
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3answers
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High School Experiment : Effect of Temperature on Strength of Magnet

I am running an experiment for my school which investigates the effect of temperature on the magnetic field of a magnet, and I encountered a little problem. For the measurement of data, I have gotten ...
5
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2answers
2k views

Optics alignment of a confocal scanning microscope

I am facing a challenge in my project regarding optical alignment. See the figure: The challenge is with the vertical optical system alignment. I considered placing a mirror and check back if the ...
5
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1answer
277 views

How important is it, really, to clean vacuum parts?

In every lab I've seen, people are quite meticulous about cleaning parts that are to be used in ultrahigh vacuum, as well as the components of the chamber itself. The parts may be put in an ultrasonic ...
5
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1answer
96 views

Why does a CfBe neutron source not exist?

Sources such as AmBe take advantage of Beryllium's $(\alpha,n)$ process to produce high energy neutrons. Sources such as Cf utilize spontaneous fission. Why not combine the two? Such a source would ...
5
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1answer
488 views

How does the Double Slit Experiment work in detail?

What is the best detailed description/visualisation of the experiment available? Describing what is actually measured, how the data is analysed, correlated and interpreted when for example large ...
5
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1answer
874 views

Einstein's original papers predicting gravitational waves? [closed]

I came across the original handwritten papers in which Einstein predicted gravitational waves1: and since LIGO announced they've detected a signal confirming the predictions I was wondering if ...
5
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2answers
186 views

How to realize long-range interaction of colds atom in an optical lattice?

In the Bose-Hubbard model of cold atoms in an optical lattice, we consider only the short-range interaction or on-site interaction. Is it possible to realize long-range interaction similar to Coulomb ...
5
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1answer
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Atoms' excitation energies as derived from Frank-Hertz experiment data

I'm analyzing the experimental data obtained during Frank-Hertz experiment (conducted with Hg atoms): Accelerating voltage values were multiplied by 0.1 during measurement (i.e. the mean value of ...
5
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1answer
79 views

How do the LIGO team arrive at the number of round trips in the laser arm etalon?

The quoted number of laser beam round trips in the arm cavity for LIGO on the MIT site is 280 times. How did they arrive such a number? Since the laser frequency is stabilized to less than 1 Hz, the ...

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