Mixed pre-meeting today, on the one hand I had to redo most of my calculations afterwards, on the other hand there is a good chance, that there will be a factor two higher fluence rate available than I expected. The engineer telling me that seemed to hope that this would mean, I would just need half the granted time. But au contraire , it just implies that I’ll get double the amount of data. Muhhahahah …
Alanine dosimeter
Maybe I should explain a little what I plan to do here in Jyvaeskylae. For an external observer I’ll just put some pellets -as the one to the left- in a particle beam and send them to some other places afterwards, which -hopefully- will send me some numbers some day. Of course this is not the whole story. The pellet seen in the picture is a dosimeter which is e.g. used to determine and compare the output of linear accelerators as used in radiotherapy departments. There are different flavours of this so-called solid state detectors besides of alanine, thermoluminescent detectors (TLDs), optical stimulated luminescent detectors (OSLs), even (almost) ordinary films as known from the pre-digital era of photography and a whole bunch more. All of them well established, working systems, as long as you are putting them in fields of X or gamma rays, which is no surprise having in mind that mankind uses this kind of radiation longer than a century. Now some of you may have heard that you also can use accelerator particles to treat cancer, as done in e.g. Heidelberg and also planned to do in Denmark. Why using particles, what’s the difference, how to do and more isn’t of interest at the moment (I’ll may add some links some day).. so FOCUS!!!
The important part for now is that we have to somehow measure the amount of radiation coming out of the machines and the energy the deposit in e.g. a human body. So we want to do dosimetry for particle beams.
The first and strategy to solve a problem is trying to apply methods we already know. Same here, people put known photon dosimeters in particle beams and look what is coming out. Unfortunately, if we put the same amount of energy in a detector once with photons, once with particles the odds are high we get two different readings. Sometimes lower for particles, sometimes higher.
No reason to despair, we should be able to calculate this difference, shouldn’t we? Yes, we should and that is basically what I’m trying to do most of my time. And now we’re back to the reason why I’m in Jyvaeskylae, I’ll try to collect data in order to proof or disproof my former calculations. They have a nice accelerator here, which by the way is mainly used test electronics for space, that provides beams of heavy particles (up to xenon) at energies (up to 9.3 MeV/u) where one expects the highest deviations to comparable photon measurements. Admitted, not the particles and energies you would use in therapy, here you would take protons or carbon ions and energies of 50-400 MeV/u . But the low energies you’ll find in the part of the particles trajectory which is actually in you target the tumour.
so far, just a little background information, or call it motivation
Here you see at least two hours of work. Not irradiating them, reading them out, or producing them, no, just putting this beastly little things in this holes, fixed with a piece of paper, without breaking them. This brings me to the point, that vinyl gloves, PMMA plates, a wool pullover and a cord trousers are not the perfectly combination for putting tiny paper pieces into place. Remember what happens after rubbing a cats skin on plastics stick and bringing this near some paper pieces?
