===> As a preliminary note, this sort of point to point reply is something I wanted to avoid as I do not have so much time to dedicate to forum activities, and also because the longer the reply is, the higher the chance of error gets.
Quote from Eric Walker
I’ll have to take your word on the scintillator not being there all the time. In Ref. 1 they talk about covering the detector with a lead plate, and they talk about other glass filters and filters of other materials, without mentioning that the scintillator is removed. In Ref. 3 Holmlid talks about the scintillator also being the vacuum window. Regardless, let's go with the assumption that the scintillator is taken away when the other materials are used.
More in detail, the scintillator-PMT assembly is detachable at the scintillator as this diagram exemplifies:
The detachable part is used for measurements at a few meters of distance from the reactor, regardless of whether converter materials are used or not. When the detector part is detached, the front window is fitted with a blind flange of a 3mm aluminium plate to prevent light from entering (as an additional measure against visible photons most experiments are also reported to be done in the dark) except in a few tests where it is replaced with a dark cloth.
Quote
Sounds like perhaps bremsstrahlung as an alternative (and far more likely) explanation?
Here Homlid is pressing a photomultiplier into service by allowing it to detect beta electrons directly, rather than using the photoelectric effect to generate electrons for incoming photons. Fine. But is this something that can be done without lots of calibrations and cross checks, to make sure you’re not creating unwanted artifacts? Perhaps it’s a straightforward thing to do. It seems like you could easily mess this up or misinterpret the results, especially if you’re a novice at using these things. What is the curve that describes the relationship between the output signal and the number (and energy) of the incident electrons? Is it the same curve as when photons are being detected? Is it linear? Does it have some shape that needs to be compensated for?
They report doing a calibration using a 137Cs source with and without the plastic scintillator (PS) with a Kurie plot. When the PS is used the intercept for Q=512 keV is at 765 channels, giving 0.67 keV/channel. Without the PS and the same electronics the intercept is at 170 channels, giving 3.0 keV/channel. A linear scale is assumed.
Quote
It’s exactly this kind of indirect reasoning that needs to be cross-checked and vetted by one or more experts in the field.
If only they would touch it! Not even the LENR experts are interested, it seems.
Quote
Would you agree that it is a red flag if there’s no clear way of calibrating the new approach to detecting muons against known sources of muons? But perhaps there's a way to thermalize accelerator muons so that they're lower energy, and then use other methods and the new method?
As tables for the stopping range of muons in different materials have been compiled I am sure that such methods exist. But I do not think there are many places where this can be done.
Quote
It looks like I inferred the wrong endpoint for the muon betas; for free muons there appears to be a sharp cutoff at 53 MeV rather than a tail out to 105 MeV. (Or is this an artifact of the detection method used?) You agree that if there are muons, it would be nice to have a beta spectrum giving evidence of them?
After looking at other sources it seems that that 53 MeV is the known maximum beta energy for free muon decay.
As for the beta spectrum for decay the capture probability of the the used materials in addition to detection energy range may be a factor here, but here I am just guessing. Holmlid suspects that the occasional appearance of a high energy tail to the signal may be due the the presence of positive muons (which do not form muonic atoms), which should be present in a muon flux formed by the decay of kaons and pions.
Anyway I also think that it would be great if other methods could be tested, for example a cloud chamber as others here suggested.
Quote
Understood. But I was talking precisely about the more conventional practice (as I understand it; I may be mixing up methods of detection) of using degraders before the scintillator, and letting the photons that are generated be detected in the usual way. My point was that you assume not muons, then place degraders of various thicknesses before the scintillator and see how much the intensity and structure of the photon signal changes. The whole metal shield/PMT thing is an unfamiliar mode of operation to me, and I’m not convinced that Holmlid understands/appreciates what subtleties there may be.
I suspect he would have to use a slightly different setup for these experiments.
I also think his reasoning here is showing that these unknown particles (that Holmlid believes are mainly muons) travel through the scintillator and the aluminium foil placed in front of it (mainly for protection against visible photons) without interacting significantly with them.
Perhaps most importantly (he remarks this in one of the papers), removing the scintillator also removes the background radiation signal.
Quote
Note that if there are energetic electrons producing bremsstrahlung, it stands to reason that the secondary photons would be stopped by the metal enclosure. But in a more typical setup, there would be the degrader (e.g., Al), the scintillator, and the PMT, without metal interposing between them, and the degraders would work as expected. It would seem to be the metal enclosure that is requiring placing the “filters” inside the apparatus.
The question is what would be the strength of this electron-produced bremsstrahlung compared to the incoming betas?
On a related note, H&O report also using other detectors, including this GM detector. Apparently it only gave a slightly higher signal where the PMT+converters gave an "enhanced" signal:
https://www.mirion.com/product…ntamination-survey-meter/
This was also used without any higher signal than background:
https://mirion.app.box.com/s/l46mg0ay1muv284dvmuj
Quote
More to the point: Homlid and Olafsson need to let some real experts in muon detection look at their setup. This should have been done years ago. I was hoping they would do this approx. 1 or 2 years ago? This is the kind of thing a scientist working outside of their field would do without a second thought. I'm not sure what's holding things up here. Perhaps the muon experts don't want anything to do with Holmlid? Or he doesn't want to consult them?
I think these results about muons have only been published since 2015. In earlier years it was mainly about the unusual emissions and observations from the ultra-dense hydrogen material produced in his experiments.
Quote
Let’s suppose for the sake of argument that there are not. All the more reason for Holmlid to engage outside expertise, to make sure he’s not just seeing what he wants to see.
I do not know what are his circumstances and it is not clear how much help he has from other people besides paper coauthors when present. But he is getting published on peer reviewed papers of not insignificant impact factor and I do not think this is simply because of his influence as a professor emeritus.
I think I recall reading on LENR-Forum that Olafsson wrote that with the current experimental setup even if one came in the laboratory to perform measurements personally he could not do anything but agree with the observations.
Maybe a different setup is needed (which is incidentally what Olafsson also suggested in a different message).