*rc3 prerol music*
Herald: All right, fellow creatures, to be honest, I never thought that I would be
introducing a talk on measuring radioactivity like ever in my life, but
then again, considering the world stage, current state at large, it might be not
such a bad idea to be prepared for these things. Right? And gladly, our next
speaker, Oliver Keller, is an expert in detecting radioactive stuff. Oliver is a
physicist and works at one of the most prominent nerd happy places. The CERN
since 2013 is also doing a PhD project about novel instruments and experiments on
natural radioactivity at the University of Geneva and to even more to add even more
C3 pizzazz. Oliver is active in the open science community and passionate about
everything open source. All that sounds really cool to me. So without further ado,
let's give a warm, virtual welcome to Oliver and let's hear what he has to say
about measuring radioactivity with using low cost silicon sensors. Oliver, the
stream is yours.
Oliver: Thanks. That was a very nice introduction. I'm really happy to have the
chance to present here. I'm a member since quite some years and this is my first CCC
talk, so I'm quite excited. Yeah, you can follow me on Twitter or I'm also on
Mastodon, not so active, and most of my stuff is on GitHub. OK, so what will we
talk about in this talk? I'll give you a short overview, also about the
radioactivity, because yeah, it's a topic with many different details and then we
will look at the detector more in detail and how that works in terms of the physics
behind it and the electronics. And then finally, we look at things that can be
measured, how the measurement actually works, what are interesting objects to
check and how this relates to silicon detectors being used at CERN. So the
project is on GitHub called DIY Particle Detector. It's an electronic design, which
is open hardware. There's a wiki with lots of further details for building and for
troubleshooting. There is a little web browser tool I will show later, briefly,
and there are scripts to record and nicely plot the measurements. Those scripts are
BSD-licensed and written in Python. There are two variants of this detector. One is
called electron detector, the other one alpha spectrometer. They use the same
circuit board, but one is using four diodes, the other one one photodiode...
There's a small difference between them, but in general it's pretty similar. But
the electron detector is much easier to build and much easier to get started
using. Then you have complete part lists and even a complete kit can be bought on
kitspace.org, which is an open hardware community repository, and I really
recommend you to check it out. It's a great community platform and everyone can
register their own GitHub project quite easily. Now, this is a particle detector
in a tin box, so you can use the famous Altoids tin box or something for Swiss
chocolate, for example. You can see it's rather small, the board about the size of
a nine volt block battery. And then you need, in addition, about 20 resistors,
capacitors and these silicon diodes plus an operational amplifier,
which is this little chip here, this little black chip here on the right side,
you can see is all old school large components. This is on purpose, so it's
easy to soldier for complete electronic beginners. And this by the way, this
picture is already one user of this project who posted their own build on
Twitter. OK, so natural radioactivity. So I would say it's a story of many
misconceptions. Let's imagine we are this little stick figure here on the ground.
Below us we have uranium and thorium. We also have Potassium-40 in the ground and
Potassium-40 is is pretty specific and peculiar. It actually makes all of us a
little bit radioactive. Every human has about 4000 to 5000 radioactive decays
every second because of the natural potassium and natural potassium comes with
a radioactive isotope, which is just everywhere, it's in bananas. But it's also
in us because we need it for our body chemistry. It's really important and even
some of those decays are even producing anti-matter. So how cool is
that? OK, so what would we be measuring on the on ground? Well, there could be some
gamma rays or electrons. Those are from beta-decays. Or from the Uranium, there is
one radionuclide appearing in the decay chain, which is called Radon, and Radon is
actually a gas. So from the ground the Radon can diffuse upwards and travel with
air and spread around. So it's a bit like a vehicle for radioactivity from
the ground to spread to other places. And that Radon would decay with alpha
particles producing electrons and beta- decays and also gamma radiation further
down in the decay chain. So just to recapitulate, I've said it already twice,
so alpha particles are actually helium nuclei, so it's just two protons and two
neutrons and the electrons are missing. And in beta decay basically one neutron is
transformed into a proton and an electron. And there's also an electron-anti-neutrino
generated. But this is super hard to measure. So we're not measuring those.
Mostly we will be measuring electrons from beta-decays. That's why you see all these
little e's indicating betadecays. Ok, if you would go to the hospital here on the
left side, we would probably find some x rays from checking our bones or something
like this, or even gamma rays or alpha particles being used in treatments or very
modern even proton beams are sometimes generated for medical applications. Now,
here on the right side, if you go close to a nuclear power plant, we probably measure
nothing unless there's a problem in this case, most likely we would find some gamma
radiation. But only if there is a problem. OK, and then actually that's not the whole
story. This is terrestrial radiation. But we also have radiation coming from
upwards, showering down on us every minute, and there's actually nothing we
can do against it. So protons are accelerated from in the universe.
Basically, the biggest particle accelerator nature has. And once they hit
our atmosphere they break apart into less energetic particles and it's many of them.
So in the first stage there's lots of pions generated and also neutrons. But neutrons
are really hard to measure, so I'll ignore them for most of the talk. Then those
pions can decay into gamma rays and then trigger a whole chain of positron electron
decays, which again create gamma rays and so forth. And this goes actually the whole
way down to the earth. We will have a little bit of that on the sea level.
And the other more known part of atmospheric radiation is actually muons.
So some pions decay into muons, which is kind of a heavy electron and also
neutrinos. But neutrinos are, again, very hard to measure. So I'll ignore them for
most of this talk. And if you look here on the right side on this altitude scale,
you'll see an airplane would be basically traveling where most of the atmospheric
radiation is produced. And this is why if you go on such an airplane, you have
actually several times more radiation in there than here on earth. And, of
course, on the ground, it also depends where you are. There are different amounts
of uranium and thorium in the ground and this is just naturally there. So but it
depends on the geology, of course. OK, so I've talked quite a bit about radiation,
and I'm saying I want to use silicon to detect it. So what radiation exactly?
Maybe. Let's let's take a step back and think about what we know maybe from
school. So we have this rainbow for visible light. Right. This is in terms of
wavelength. We have 800 to 400 nanometers spanning from the infrared/red area to all
the green to blue and into the violet. And lower down those wavelengths or let's say
bigger millimeter waves, meter waves and even kilometer, that would be radio waves,
radio frequencies for our digital communication systems, wi-fi, mobile
devices and so forth. But I want to look actually more towards the right because
that's what we are measuring with these detectors. It's shorter wavelength, which
actually means higher energy. So on the right side, we would be having ultraviolet
radiation, which is kind of at the border to what we can measure. And these 800 to
400nm translate into 1.5 to 3 eV, which is a unit that particle physicists really
prefer because it basically relates the energy of an electron after it has been
accelerated by 1 Volt and makes it much easier to work with nuclear
particle physics, because everything, all the energy is always related to an
electron. And this energy, this formula here is just a reminder that the
wavelengths can be always converted into energy and it's inversely proportional. So
wavelength increases to the left and the energy to right. And if you increase
energy more from from the visible range, so let's say thousands of electron volts,
then we arrive here. Millions - mega electron volts, even GeV. And there is now
a pretty important distinction between those two areas, and that is the right one
is ionizing radiation and the left one is non ionizing radiation. UV is a little bit
in the middle of that. So some parts of the UV spectrum can be ionizing. It also
depends a lot on the material that the radiation is interacting with. For these
detectors I'm talking about today and alpha, beta, gamma radiation, this is all
ionizing, so some examples, lowest energy on the lower spectrum would be x rays than
electrons, gamma rays from radioactive nuclides that already talked about in the
previous slide, alpha particles, and that muons from the atmosphere would be more on
the GeV range and so forth. And for these higher energies, of course, you need
something like the LHC to accelerate particles to really high energies. And
then you can even access the TeV regime. OK, silicon diodes. What kind of silicon
diodes? I'm using in this project, low local silicon pin diodes, one is called
BPW34 it's manufactured from Vishay or Osram, costs about 50 cents. So that's what
I mean with low cost. There's another one called BPX61 from Osram. It's quite a bit
more expensive. This is the lower one here on the right. It has a metal case, which
is the main reason why it's more expensive. But it's quite interesting
because that one we can use for the alpha detector. If you look closely, there is a
glass on top, but we can remove that. We have a sensitive area. So this chip is
roughly 7mm² large and it has a thickness, a sensitive thickness of about 50
micrometer, which is not a lot. So it's basically the half of the width of a human
hair. And in total, it's a really small, sensitive volume. But it's it's enough to
measure something. And just as a reminder, how much of gamma rays or X-rays we will
detect with this, not a lot because it's high, energetic photon radiation kind
doesn't interact very well in any kind of matter. And because a sensitive area is so
thin, it would basically permeate through it and most of the times not interact and
doesn't make a signal. OK, what's really important, since we don't want to measure
light, we have to shield light away. We need to block all of the light, that means
easiest way to do it is to put it in a metal case. There is electromagnetically
shielded and completely protected from light as well. Electromagnetic radiation
or radiowaves can also influence these detectors because they are super
sensitive. So this sould be a complete Faraday cage, complete metal structure
around it. There's a lot of hints and tips how to achieve that on the wiki on the on
the GitHub of this project. OK, let's think about one of those PIN diodes,
normally there is one part in the silicon which is n-doped
negatively doped, and the other part usually, which is positively dropped. And
then you arrive at a simple so called p-n- junction, which is a regular
semiconducting diode. Now, pin diodes add another layer of so-called intrinsic
layer, here shown with the i. And that actually is the main advantage. Why this
kind of detector works quite well and have a relatively large sensitive Sigma's. So
if you think about, let's say, a photon from an x ray or gamma-decay or an
electron hitting the sensor. So by the way, this is a cross-section view from the
side, but that doesn't really matter. But let's say they come here from the top into
the... into the diode and we're looking at the side then we have actually
ionization because this is ionizing radiation, so we get free charges in the
form of electron-hole pairs. So electrons, which here the blue ball and the red
circle would be the holes. And depending on the radiation kind, how this ionization
takes place is quite different, but the result is if you get a signal, it means
there was ionization. Now, if just this would happen, we could not measure
anything. Those charges would quickly recombine and on the outside of the diode,
it would be a little signal. But what we can do is we can apply actually a voltage
from the outside. So here we just put a battery. So we have a positive voltage
here, a couple of volts. And then what happens is that the electrons would be
attracted by the positive voltage and the holes will travel to the negative
potential. And we end up with a little net current or a small bunch of charges that
can be measured across the diode as a tiny, tiny current. The sensitive volume
is actually proportional to the voltage, so the more voltage we put, the more the
bigger is our volume and the more we can actually measure with certain limits, of
course, because the structure of the pin diode has a maximum thickness just
according how it is manufactured. And these properties can be estimated with
C-V-measurements. So here you see an example of a couple of diodes, a few of
the same type. The two that I've mentioned, they're different versions. One
has a transparent plastic case. One has a black plastic case. Doesn't really matter.
You see, basically in all the cases, more or less the same curve. And as you
increase the voltage, the capacitance goes down. So it's great and basically shows us
those silicon chips are very similar, if not exactly the same chip. Those
differences are easily explained by manufacturing variances. And then because
this actually, if you think about it, it looks a bit like a parallel plate
capacitor and actually you can treat it as one. And if you know the capacitance and
the size, the area, you can actually calculate the distance of these two plates
or basically width or the thickness of the diode. And then we arrive at about 50
micrometer, if you put something like 8 or 10 volts. OK, now we have a tiny charge
current, now we need to amplify it, so we have a couple of diodes, I'm explaining
now the electron detector, because it's easier. We have four diodes at the input
and this is the symbol for an operational amplifier. There are two of those in the
circuit. The first stage is really the special one. So if you have a particle
striking the diode, we get a little charge current hitting the amplifier. And then we
have here this important feedback circuit. So the output is fed back into
the input, which in this case makes a negative amplification. And the
amplification is defined actually by this capacitance here. The resistor has a
secondary role with the small capacitance. It is what makes the output voltage here
large. The smaller the capacitance, the larger the output and it's inverted. Then
in the next amplifier step, we just increase the voltage again to a level that
is useful for using it later. But all of the signal quality that has been
achieved in the first stage will stay like that. So signal to noise is defined by the
first stage. The second one is just to better adapt it to the input of the
measurement device that's connected. So here, this is a classic inverting
amplifier with just these two resistors define the amplification factor. It's very
simple. It's just a factor of hundred in this case. And so if you think again about
the charge pulse and this, the circuit here is sensitive, starting from about
1000 liberated charges in those diodes as a result from ionization. We get something
like 320 micro Volt at this first output, and this is a spike that quickly
decreases. Basically these capacitors are charged and quickly discharged with this
resistor and this is what we see here. And then that is amplified again by a factor
of 100. And then we arrive at something like at least 32 mV, which is conveniently
a voltage that is compatible with most microphone or headset inputs of computers
or mobile phones, so that the regular headset here has these four connectors and
the last ring actually connects the microphone. The other is ground and reft.
Left, right for the earbuds. OK, how do we record those pulses? This is an example of
1000 pulses overlayed and measured on an oscilloscope here. So it's a bit more
accurate. You see the deposits a bit better, kind of like the persistence mode
of an oscilloscope. And the size of the pulse is proportional to energy that was
absorbed. And the circuit is made in such a way that the width of the pulse is big
enough such that regular sampling frequency of a sound card can actually
catch it and measure it. Yeah, this is Potassium Salt. This is cut here. This is
called a low salt in the UK. There is also a german variance, you can also just buy
it in the pharmacy or in certain organic food stores as a replacement salt.
On the right side is an example from this small Columbite Stone, which has traces of
uranium on it. And this is measured with the alpha spectrometer. And you see those
pulses are quite a bit bigger here. We have 50 microseconds and here we have more
like one milliseconds of pulse width. Now there's a software on a browser. This is
something I wrote using the Web Audio API and it works on most browsers, best is
Chrome, on iOs, of course, you have to use Safari and that records once you plug the
detector, it records from the input at 48 or 44.1kHz the pulses. Here's an example
with the alpha spectrometer circuit, you get these nice large pulses. In case of
the electron detector the pulse is much shorter and you see it, you see the noise
much more amplified. This red line is kind of the minimum level that the pulse needs
to trigger. This would be better. And that's like the trigger level of an
oscilloscope. And you can set that with those buttons in the browser. You need to
find a good value. Of course, if you change your input volume settings, for
example, this will change. So you have to remember which, with which settings it
works well. And it is pulsed, for example, is even oscillating here. So for electron
detector, it's basically nice to count particles. For the alpha detector it's
really the case where the size of the pulse can be nicely evaluated and we can
actually do energy measurements. And these energy measurements can be also called
spectrometry. So if you look closer at these many pulses that have been recorded
and we find that there is really like much more intensity, which means many more same
pulses were detected, we can relate it to radium and radon. If we use a reference
alpha source and I have done this, I have measured the whole circuit with the reference
sources and provide the calibration on GitHub and you can reuse the GitHub
calibration if you use exactly the same sound settings that I have used for
recording. And for example, these two very weak lines here from two very distinctive
polonium isotopes from the uranium decay chain. The top part here which is really
dark, corresponds basically in the histogram view to this side on the left,
which is electrons. Most of these electrons will actually enter the chip and
leave it without being completely absorbed by it, but alpha particles
interact so strongly that they are completely absorbed within the 50
micrometers of sensitive volume of these diodes and OK here is a bit difficult to
see peaks. But the far end of the high energy spectrum, you see two really clear
peaks and those can only stem from polonium, actually. I mean, we know it's
uranium and that can only be polonium, which is that isotope that produces the
most energetic alpha particles and which is natural. And I said, if you use
the same setting like me, you can use it. So the best is if you use actually the
same soundcard because they're if you put it to hundred percent input sensitivity,
you will have exactly the same result, like in my calibration case. And this
soundcard is pretty cheap, but also pretty good. It costs just two dollars and has a
pretty range and resolves quite well, 16 bits and think, oh, you could do that with
Arduino as well, is actually a bit hard to do. A really well defined 16 bit
measurement, even at 48 kHz. It's not so easy and this keeps it cheap and kind of
straightforward. And you can have just some Python scripts on the computer to
read it out. And this is as a reminder, in order to measure alpha particles, we have
to remove the glass here on top of the diode. So I'm doing it just cutting into
the metal frame and then the glass breaks away easily. Is not a problem, there's
more on that on the wiki. Now we can kind of compare alpha and gamma
spectrometry. Here's an example. This is the uranium glazed ceramics. The red part
is uranium oxide that was used to create this nice red color in the 50s, 60s, 70s.
And in the spectrum we have two very distinctive peaks and nothing in the high
energy regime. Only this low energy range has a signal. And this corresponds
actually to uranium 238 and 234 because they use actually purified uranium. So all
of the high energy progeny or daughters of uranium, they're not present here because
it was purified uranium. And this measurement doesn't even need vacuum, I
put it just like this in a regular box. Of course, if you would have vacuum, you
would improve this peaks by a lot. So this widening here to the left, basically, that
this peak is almost below the other one. That is due to the natural air at regular
air pressure, which already interacts a lot with the particles and absorbs a lot
of energy before the particles hit the sensor. So in terms of pros and cons, I
would say the small sensor is quite interesting here in an alpha spectrometry
because it's enough to have a small sensor. So it's cheap and you can measure
very precisely on specific spots. And on the other hand, of course, the conditions
of the object influence the measurement a lot. So, for example, if there's some
additional paint on top, the alpha particles might not make it through. But
in most of these kind of samples, alpha radiation actually makes it through the
top, a transparent paint layer. In terms of gamma spectrometry, you would usually
have these huge and really expensive sensors. And then the advantage, of
course, is that you can measure, regardless of your object, you don't
really need to prepare the object a lot. You might want some lead shielding around
it. That's again, expensive, but you can do it. You can improve the measurement
like that. And it's basically costly because the sensor is quite expensive.
Vice versa in the set setup for 15 to 30 euro. You have everything you need and
here you're looking at several hundred to several thousand euros. OK, now measuring
I have to be a bit quicker now, I noticed. So I talked about the potassium
salt. There's also fertilizer based on potassium baking powder. Uranium glass is
quite nice. You can find that easily on flea markets. Often also old radium
watches. Here's another example of a uranium glaze, the kitchen tile in this
case, this was actually in the kitchen. So the chances are that you at home find
actually some of those things in the cupboards of your parents or your
grandparents. It is an example of thoriated glass, which has this
distinctive brownish color, which actually is from the radiation. And a nice little
experiment that I can really recommend you to look up is radioactive balloon
experiment. Here, you charge the balloon electrostaticly and then it would catch
polonium from the air. And it's really great. You basically get a radioactive
balloon after it was just left for 15 minutes in a normal regular room. OK, now
the last kind of context of all of this to end this presentation, I want to
quickly remind how important these silicon detectors are for places like CERN. It's a
cross-section of the ATLAS detector. And here you have basically the area where the
collisions happen in the ATLAS detector. So this is just a fraction of a meter. And
you have today 50 to 100 head on collisions of two protons happening every 25
nanoseconds. Not right now, but soon again, machines will be started again next
year. And you also can, by the way, build a similar project which has a slightly
different name. It's called Build Your Own Particle Detector. This is Atlas and made
out of LEGO. And on this website, you find a nice plan, how to build or ideas,
how to build it from LEGO to better visualize the size and interact more with
particle physics. In case of the CMS detector. This is the second biggest
detector at CERN. Here you see nicely that in the middle, at the core of the
collision, you have many, many pixel and microstrip detectors which are made of
silicon. And these are actually 16 m² of silicon pixel detectors and 200m² of
microstrip detectors also made of silicon. So without basically that silicon
technology modern detectors wouldn't work because this fine segmentation is really
required to distinguish all of these newly created particles as a result of the
collision. So to summarize the website is on GitHub, there is really this big wiki,
which you should have a look at, and there's a gallery of pictures from users.
There's some simulation software that I used as well. I didn't develop it, but I
wrote how to use it because the spectra can sometimes be difficult to interpret.
And there's a new discussion forum that I would really appreciate if some of you had
some discussions there on GitHub. And most of the things I saw today are actually
written in detail in a scientific article, which is open access, of course. And I
want to highlight two related citizen science projects on the one hand, as the
safecast, which is about a large, nice, sensitive Geiger-Müller based detector
that has the GPS and people upload their measurements there. This is quite nice.
And also opengeiger is another website, mostly German content, but also some of it
is English, that also uses diode detectors, showed many nice places. He
calls it Geiger caching, places around the world where you can measure something,
some old mines, things like this. And if you want updates, I would propose to
follow me on Twitter. I'm right now writing up two other articles with more
ideas for measurements and some of the things you have seen today. Thanks a lot.
Herald: Well, thanks a lot, Oliver. I hope everyone can hear me now again. Yes,
thanks for mentioning the citizen science project as well. It's really cool I think.
We do have a few minutes for the Q&A and also a lot of questions coming up in our
instance at the IRC. So the first question was, can you talk a bit more about the SNR
of the system? Did you pick particular resistor values and or Opamps to optimize
for noise? Was it a problem? Oliver: Yeah, so noise is the big
issue here. Basically, the amplifier is one I found that this around four, four
euros, trying to find the slide. Yeah, you have to look it up on GitHub to the
amplifier type, but this is the most important one. And then actually the
resistors, here, the resistance in the first stage, sorry, the capacitors is the
second important thing. They should be really small since I'm limited here with
hand soldarable capacitors. Basically I choose the one that were just still
available, let's say, and this is basically what is available is basically a
10 pF capacitor. If you put two of them, one after another, you half the
capacitance, so you get five. And this, by the way, is also then the capacitor. So I
kind of tried to keep the same resistor values as much as possible, and
here at the output, for example, this is to adjust the output signal for a
microphone input in the alpha spectrometer, I changed the values quite a
bit to make a large pulse. But, yeah, it's basically playing with the time
constants of this network and this network.
Herald: All right, I hope that answers for the person. Yeah, but people can get a
contact to you right after the show maybe as well. So there's another question. Have
you considered using an I²S Codec with a Raspberry Pi? radiation H80 should be
almost no set up and completely repeatable. So last ones are for comment.
Oliver: I don't know that component, but, yeah, as I said, using a sound card, it's
actually quite straightforward. But of course there's many ways to get fancy.
And this is really this should actually attract teachers and high school students
as well, this project. So this is one of the main reasons why certain technologies
have been chosen, rather simple than, let's say, fancy.
Herald: Yeah, so it should work with a lot of people, I guess, and one another
question was how consistent are the sound cards? Did you find the same calibration
worked the same with several of them? Oliver: So if you want to use my
calibration, you should really buy this two dollar card from eBay, CM108. I
haven't seen a big difference from card to card in this one. But of course, like from
one computer to the mobile phone, it's a huge difference in input, sensitivity and
noise. And it's very difficult to reuse the calibration in this case. But you
still can count particles and the electron detector is anyway, um, mostly it actually
just makes sense for counting because the electrons are not completely absorbed. So
you get an energy information, but it's not the complete energy of the electron.
So yeah, you could use it for x rays, but then you need an x ray machine. So yeah.
Herald: Who doesn't need an x ray machine, right? *laugs* So maybe one question I
have, because I'm not very familiar with the tech stuff, but what actually can be
done with it right in the field. So you mentioned some working with teachers with
these detectors? What have you done with that in the wild so to say?
Oliver: So what's quite nice is you can characterize stones with it, for example.
So since you can connect it to a smartphone this is completely mobile and
it goes quite well in combination with a Geiger counter in this case. So with a
Geiger counter, you just look around, where are some hot spots and then you can
go closer with the alpha spectrometer and actually be sure that there is some traces
of thorium or uranium on the stone, for example. Or in this type of ceramic, these
old ceramics, you can go to the flea market and just look for these very bright
red ceramics and measure them on the spot and then decide which one to buy.
Herald: OK, so that's what I'm going to do with it. Thanks for for highlighting a bit
the practical side, I think it's really cool to educate people about scientific
things as well. Another question from the IRC. Didn't you have problems with common
mode rejection by connecting the device through the sound card? If yes have you
tried to do a AD conversion digitization on the bord itself already? Transfer
transfer wire SP dif? Oliver: Yeah, so, of course, I mean, this
is the thing to do, if you want to make a like a super stable, rock solid
measurement device, but it is really expensive. I mean, we are looking here at
15 euros and yeah, that's the reason to have this separate soundcard just to
enable with some very low resources to do this. But I'm looking for these pulses. So
this common mode rejection is a problem. And also this is kind of Überschwinger -
I'm missing the English term. This is kind of oscillations here. If you design a
specific analog to digital conversion, of course, you would take all of that into
account and it wouldn't happen. But here this happens because the circuit can never
be exactly optimal for certain soundcard input. It will always be some mismatch of
impedances and. Herald: All right, so maybe these special
technical issues and details, this could be something you could discuss with Oliver
on Twitter of maybe Oliver or want to join the IRC room for your talk as well. People
were very engaged during your talk. So is this always a good sign. In that sense I'd
say thank you for being part of this first remote chaos experience. Thanks again for
for your talk and for taking the time and yeah, best for you and enjoy the rest of
the conference of the Congress and a warm round of virtual applause and big thank
you to you, Oliver. Oliver: Thanks, I will join the chat room
right now.
*rc3 postrol music*
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