32,131 reputation
343105
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 3 years, 8 months
seen 7 mins ago

Experimental nuclear and particle physicist. These days I'm teaching, but I've spent a lot of time on nucleon structure in fixed target electron scattering and neutrino oscillations using reactors and beam sources.


2d
revised Quantum Efficiency Estimation
edited tags
2d
answered Why aren't units with powers, like cm³, surrounded by parentheses?
2d
comment Quantum Efficiency Estimation
People who work with devices of that type can probably give you a rule-of-thumb value or range. For instance, I know that high-acceptance, visible-light PMTs typically run between 0.1 and 0.3 (depending on how much you paid for them) simply because I have had repeated encounters with them over the years.
Jul
28
comment Double slit experiment with slit material acting as a detector
It is not at all clear to me what you are asking. Recording particles that don't pass the slit is possible but not very enlightening.
Jul
27
comment Is this air cooling idea feasible?
@thyme Evaporative coolers are still used in some dry areas (I had one for a few years in southern New Mexico). They really do cool the air as well as moistening it as long as the air is dry enough. The air is forced through the fiberous pad continuosly so there are two competing effects: the pad is cooled by evaporation and warmed by contact with the air. The result is an output that is both cooler and moister than the outside air. When the humidity rises much above 30% they start to get a lot less efficient, but in that part of the world it is often 10-15%.
Jul
27
awarded  Enlightened
Jul
27
awarded  Nice Answer
Jul
27
comment How would an X-ray mirror work?
For what it is worth, a lot of the radiation worry on space voyages comes from massive particles of various sorts.
Jul
27
comment How would an X-ray scanner identify a mirror?
@JoeBlow At the "shipping container" scale x-ray back-scatter doesn't have the penetration. I believe they use neutron fluorecence in at least some applications.
Jul
27
revised How would an X-ray scanner identify a mirror?
Remove follow-up question which should be posted as a question in its own right
Jul
25
comment Mathematical derivation of interference pattern for electrons?
BTW--I agree with Daniel about the boundary conditions issue, but a numeric approach might be able to handle that.
Jul
25
comment Mathematical derivation of interference pattern for electrons?
"the Schrödinger equation (which we know is obeyed by electrons)" Er ... no. You can weld the spin onto the SE wave-function for non-relativistic electrons if you want to, or you can just neglect spin and use the plain 'ole SE, but again it must be for non-relativistic electrons. Fundamentally, electrons are Dirac particles.
Jul
25
comment Could Particles Really Spin in the Really Real World? The video in the link says they do
To be very clear, the "spin" of particles is definitely angular momentum and definitely does not arise from a $\mathbf{r} \times \mathbf{p}$ term the way angular momentum from macroscopic spinning objects does, but compound particles (such as baryons) can have orbital angular momentum in additional to any intrinsic angular momentum (i.e. spin) they may carry.
Jul
24
comment Is it possible to produce images of pair production in home-made cloud chamber?
@steveOw You can't just set $v=c$ and use the Newtonian formula. If you know the (total) energy and mass of a particle than $(m c^2)^2 = E^2 - (pc)^2$. If you only know the kinetic energy $T$ of a particle then $E = T + mc^2$ and proceed as above. Note that particle physicists and particle physics references normally set $c=1$ and quote energies, masses and momenta in multiples of electron-volts.
Jul
24
comment can we get electrical energy from gravitational energy?
NASA has even run a test flight on powering satellites from the motional EMF of their orbit through the Earth magnetic field. You have to run out a couple of long antennas, and as @Jim says it will eventually deorbit the bird, but it works.
Jul
24
comment Which experiment would be able to detect change in the speed of light?
Another one that is not exactly a duplicate but is highly relevant (because we actually do these experiments all the time): physics.stackexchange.com/questions/18149/…
Jul
24
comment Is it possible to produce images of pair production in home-made cloud chamber?
@DanS You can buy well sealed sources CoTS (in fact, there is more paperwork to get access to raw radio-isotopes than for the sealed sources). And the quantities needed are pretty low. That $\mu\mathrm{Ci}$ that Chris mentions is about $40000\,\mathrm{Bq}$ which is plenty for what the OP desires. The OP will want to store them in a source safe or something equivalent, but they pose no danger to someone outside the garage.
Jul
24
revised Is it possible to produce images of pair production in home-made cloud chamber?
added 241 characters in body
Jul
23
answered Is it possible to produce images of pair production in home-made cloud chamber?
Jul
23
comment If atoms never “physically” touch each others, then how does matter-antimatter annihilation happen?
It can be (and is) simultaneously true that electrons scatter like point-particles (down to $10^{-18}\,\mathrm{m}$ experimental precision) and that their bound wave-function gives significant probability to distances on order of $10^{-10}\,\mathrm{m}$.