Measured distribution of cloud chamber tracks from radioactive decay: a new empirical approach to investigating the quantum measurement problem

Using publicly available video of a diffusion cloud chamber with a very smallradioactive source, I measure the spatial distribution of where tracks start, and consider possibleimplications. This is directly relevant to the quantum measurement problem and its possibleresolution, and appears never to have been done before. The raw data are relatively uncontrolled,leading to caveats that should guide future, more tailored experiments. Results may suggest amodification to Born’s rule at very small wavefunction, with possibly profound implications forthe detection of extremely rare events such as proton decay. I introduce two candidate smallwavefunctionBorn rule modifications, a hard cutoff and an offset model; the data may favor theoffset model, which has a stronger underlying physical rationale. Track distributions from decaysin cloud chambers represent a previously unappreciated way to probe the foundations of quantummechanics, and a novel case of wavefunctions with macroscopic signatures.

Measured distribution of cloud chamber tracks from radioactive decay: a new empirical approach to investigating the quantum measurement problem

Using publically available video of a cloud chamber with a very small radioactive source, I measure the spatial distribution of where tracks start, and consider possible implications. This is directly relevant to the quantum measurement problem and its possible resolution, and appears never to have been done before. The raw data are relatively uncontrolled, leading to caveats that should guide future, more tailored experiments. Track distributions from decays in cloud chambers represent a previously unappreciated way to probe the foundations of quantum mechanics, and a novel case of wavefunctions with macroscopic signatures.

Measured distribution of cloud chamber tracks from radioactive decay

Using publically available video of a cloud chamber with a very small radioactive source, I measure the spatial distribution of where tracks start, and consider possible implications. This is directly relevant to the quantum measurement problem and its possible resolution, and appears never to have been done before. The raw data are relatively uncontrolled, leading to caveats that should guide future, more tailored experiments. Track distributions from decays in cloud chambers represent a previously unappreciated way to probe the foundations of quantum mechanics, and a novel case of wavefunctions with macroscopic signatures.

‘Seeing with one's own eyes’ and speaking to the mind: a history of the Wilson cloud chamber in the teaching of physics

In 1911 the Wilson cloud chamber opened new possibilities for physics pedagogy. The instrument, which visualized particles’ tracks as trails of condensed vapour, was adopted by physicists to pursue frontier research on the Compton effect, the positron and the transmutation of atomic nuclei. But as the present paper will show, Wilson's instrument did not just open up new research opportunities, but the possibility of developing a different kind of teaching. Equipped with a powerful visualization tool, some physicists–teachers employed Wilson's instrument to introduce their students to a wide range of phenomena and concepts, ranging from the behaviour of clouds to Einstein's photon, the wave–particle duality and the understanding of the nucleus. This paper uses the notes, books and prototypes of these pioneering physicists–teachers to compose a pedagogical history of the Wilson cloud chamber, documenting an episode of immense ingenuity, creativity and scientific imagination.

The First Droplet in a Cloud Chamber Track

In a cloud chamber, the quantum measurement problem amounts to explaining the first droplet in a charged-particle track; subsequent droplets are explained by Mott’s 1929 wave-theoretic argument about collision-induced wavefunction collimation. I formulate a mechanism for how the first droplet in a cloud chamber track arises, making no reference to quantum measurement axioms. I look specifically at tracks of charged particles emitted in the simplest slow decays, because I can reason about rather than guess the form that wave packets take. The first visible droplet occurs when a randomly occurring, barely-subcritical vapor droplet is pushed past criticality by ionization triggered by the faint wavefunction of the emitted charged particle. This is possible because potential energy incurred when an ionized vapor molecule polarizes the other molecules in a droplet can balance the excitation energy needed for the emitted charged particle to create the ion in the first place. This degeneracy is a singular condition for Coulombic scattering, leading to infinite or near-infinite ionization cross sections, and from there to an emergent Born rule in position space, but not an operator projection as in the projection postulate. Analogous mechanisms may explain canonical quantum measurement behavior in detectors such as ionization chambers, proportional counters, photomultiplier tubes or bubble chambers. This work is important because attempts to understand canonical quantum measurement behavior and its limitations have become urgent in view of worldwide investment in quantum computing and in searches for super-rare processes (e.g., proton decay).

Iodic acid formation and yield from iodine photolysis at the CERN CLOUD chamber

<p>Iodine oxoacids are key species involved in the cycling of iodine between the gas- and aerosol phases. Iodic acid (HIO<sub>3</sub>) nucleates particles more efficiently than sulfuric acid and ammonia at comparable concentrations, and grows them at comparable rates, but the formation mechanism of HIO<sub>3</sub> is essentially unknown. As a result, atmospheric models of iodine chemistry are currently incomplete. Proposed precursors for iodine oxoacids include iodine atoms and higher iodine oxides (e.g., I<sub>2</sub>O<sub>2</sub>, I<sub>2</sub>O<sub>3</sub>, I<sub>2</sub>O<sub>4</sub>), but theoretical predictions have not currently been assessed under experimental conditions that approximate the open ocean marine atmosphere. We present results from laboratory experiments at the CLOUD chamber that observe rapid oxoacid formation from photolysis of iodine (I<sub>2</sub>) at green wavelengths, in the presence of ozone and variable relative humidity (0-80%). Under these (soft) experimental conditions iodine oxide (IO) radical concentrations closely approximate those found in the remote marine boundary layer. A chemical box model is constrained by measurements of I<sub>2</sub>, ozone, RH, photolysis frequencies (i.e., I<sub>2</sub>, IO, OIO, HOI, I<sub>x</sub>O<sub>y</sub>) and known losses of gases to particles and the chamber walls, and evaluated using time resolved measurements of IO, OIO, and I<sub>x</sub>O<sub>y</sub> species in the chamber. Hypothesized mechanisms for HIO<sub>3</sub> formation - either proposed in the literature or motivated from our observations - are then discussed in terms of their ability to explain the observed amounts (yield), and the temporal evolution of HIO<sub>3</sub>. Finally, the atmospheric relevance of the laboratory findings is assessed in context of unique field measurements at the Maido Observatory, La Reunion, during spring 2018, where IO radicals and HIO<sub>3</sub> were measured simultaneously in the remote free troposphere.</p>