Blog Image

A year in Japan

Why This

An adventure in a foreign land deserves constant updates for friends and family back home (Sweden and Europe).

Thor, God of…

Science stuff Posted on Fri, April 24, 2015 09:44:14

On Saturday the 18th of April there was an Open Campus day at Riken Wako. It was estimated that about 5 000 people visited the campus that day to learn more about science, research and the Riken Wako Campus. For us this luckily didn’t mean we had to clean the office. That would be a full time job for a couple of people for a long time. However, it did demand we each put together a quick presentation about our work and what we’re doing.

Since I’m now part of the JEM-EUSO collaboration and being Swedish I thought I would do a nice twist on the presentation. I was also told that the majority of the audience would be children. Given the popularity of the Marvel films I thought I could talk about the Norse God Thor.

Thor was the Viking God of Thunder and Lightning. He had a hammer which produced the lightning and when riding across the sky in his chariot it caused the rolling thunder.
(Copyright Marvel and all that stuff)

However, today we know that this might not really be the case. In 1749 Benjamin Frankling performed his experiment with the key tied to the string of a kite and in doing so proved that the lightning actually was electricity. Today we have quite a good grasp of how the actual lightning bolt works but there are, to many peoples surprise, still some mysteries regarding lightning. The main mystery is the we actually still have no confirmed understanding of how lightning actually can be created. Here’s some more physics…

In order for lightning, or a static discharge to occur the potential difference between two opposite charged objects have to exceed a certain threshold. If the electric field is higher a discharge can occur. This is exactly what happens when you reach for the door handle and just before you can grab it there’s a spark and your finger hurts. In order for this discharge to happen the electric field in air has to be higher than about 2 MV/m (Mega Volt per meter, i.e. 2 000 000 V/m). This implies that if the discharge occurring when you reach for the door handle happens when your fingertip is about 1 cm from it the lightning bolt will measure about 20 000 V.

Here’s the strange part, measurements which have been performed in thunder clouds show that the electric field is not even near being strong enough to support the lightning discharge that actually occurs.

One theory has been put forward which could explain the lightning even though the lack of electric field strength. The theory is referred to as the Runaway Breakdown, and is an effect of cosmic radiation hitting the atmosphere and creating an Air Shower (see earlier post).
The classical depiction of an air shower from an arriving cosmic ray

Studies of this phenomenon have so far not been able to disprove a connection between lightning strikes and the arrival of cosmic rays. In fact the results show rather the opposite, that there most likely is a connection between the two phenomena.

The JEM-EUSO collaboration will be studying this by observing lightning from the International Space Station and compare the lightning strikes with the detection of arriving cosmic rays.

So the JEM-EUSO collaboration will be able to answer the question if…

Thor was the God of lightning and thunder

or in fact

the god of cosmic rays…


Science stuff Posted on Tue, April 14, 2015 10:37:44

After having built a UV filter for my camera I was able to confirm that we should, without any problems, be able to see stars in the night sky. After some small adjustments to the telescope, the stars suddenly appeared and we were all very happy to see them.

Our hope is obviously to be so lucky that we will be able to observe an Air shower. However, in order to run, we first have to learn how to walk, and before we learn how to walk we need to learn how to crawl. Basically what we just had done was making an attempt to sit up.

Located about 20 km from our telescope was a powerful laser. This laser was aimed in the zenith direction and could fire multiple bursts of laser shots into the night sky. Given the inclination of our telescope we have a time frame of about 20 µs during which a laser pulse is within our field of view. 20 µs is the same as 0.00002 s, i.e. you can have 50 000 such time frames, back to back, in a single second. This might sound very fast, and it is, but it’s no problem for our detector. The timing resolution of the telescope is 2.5 µs i.e. we should be able to see a single laser pulse in about 8 frames.

At the moment our telescope has no internal trigger, this is actually what I’m working on at the moment. So in order to see the laser we needed the trigger from the TA-FD. A “trigger” is just a signal saying “it’s time to read out the detector”.

A very intense wait followed after we were ready to try to observe the laser shot until it actually was time for the laser to fire. The seconds ticked by slowly, really slowly. But suddenly the screen started showing output that the detector was triggering the readout and shortly thereafter we could start looking at the data…

And there it was, we could clearly see the laser pulse ascending to the night sky across our field of view!!

This might not seem as much of a thing, although being able to show that we can see the laser proves that the detector principle is correct and that we’ve built it correctly! An email with the data was soon sent to the collaboration and shortly thereafter congratulatory emails started dropping in from the PIs (PI is Principle Investigator i.e. Boss) from all over the world. Below you can see how the laser pulse ascends across our focal surface on the way into the night sky.

(For some reason the gif doesn’t play so click here on it to see the animation.)

The EUSO-TA March 2015 campaign at Telescope Array could be classified as a success.


Science stuff Posted on Wed, April 01, 2015 18:09:02

I thought I also should write a bit about the work we did in Utah. Yes, we actually had time to do some work between all the sight seeing.

As I wrote last week, the reason we went to Utah was that it has good conditions to view air showers and that’s why TA – Telescope Array – has set up shop there. We have built a small detector in front of one of their optical telescopes. The main objective of our detector, EUSO-TA – Extreme Universe Space Observatory at Telescope Array – is to first show that the detector works, take measurements of two separate lasers which will be firing into the sky to simulate an air shower, take measurements on the night sky back ground and ultimately hopefully be able to observe an actual event. Now the last point is extremely difficult given how rare these events are.

This trip was actually the second campaign to Utah. The first was two years ago, and I was obviously not part of it. Although, as far as I know there was little success at that time due to problems with the electronics.
Above: Me with (R->L) the Black Rock Mesa FD Telescope, the EUSO shed and the Electron Beam Facility in the background.

When we arrived our colleagues had already been in Delta for about 10 days. So basically everything was already up and running. Although no good observations had been made.

The TA Florescent Detector (FD) can only operate during “dark time” which is night time when the moon has not yet risen. We had planed to start our work before dark time so that we could run around outside the control room with flash lights without disturbing TA operations.

We started the observations by trying to see blinking diodes and a high powered hand held laser, see picture.
Yes, I know. It does look like a light sabre from Star Wars.

We also tried to observe stars but we had some difficulties in the beginning. Therefore Marco suggested I’d build a UV-filter using the same type of UV-filter we have in the detector for my camera. However, we only had UV filter pieces about 2×2 cm² and since the diameter of the lens is 77 mm I had to MacGyver together this:
And surprisingly enough it actually worked…
I did manage to see the stars when the filter was mounted on the camera. Unfortunately I do not have any good pictures of that at the moment. I’ll maybe update the post with such a picture later.

More to follow….

A nice Shower

Science stuff Posted on Wed, March 25, 2015 11:02:36

So, again it’s been aeons since I wrote something… One would think that I’m so busy that I don’t have time to write. Frankly I have no idea where time disappears to. Probably Netflix…

However, this time I actually do have some sort of reason for not having written, at least for a few of the weeks I’ve been absent. The reason is that we have been in the great metropolitan city of Delta in Utah. Delta is a city with a population of about 3 500 and is located 50 miles past nowhere, in the middle of the desert.

The reason for us being in Delta was that since it is located in the middle of the desert it poses great opportunities for astronomical observations. Therefore one of the larges air shower telescopes, TA – Telescope Array, is located about 30 minutes drive outside Delta.

An air shower is a cascade of particles created in the upper atmosphere when extremely energetic cosmic ray particles (mainly protons) collides with air molecules. The collision is so violent that the proton breaks into a very large number of pieces. As a result a light glow can be observed in the sky. Well… If you have a very expensive type of telescope.

The glow is mainly in the UV-range of the light spectrum (300-400 nm) and last for only a fraction of a second. Therefore you need the specialised telescopes to see them.

This type of telescope is actually what the project I’m currently working with is trying to develop. However, our telescope is not intended to sit on the ground looking up into the night sky. We want to place our telescope in the International Space Station, looking down onto the night sky. In doing so, we will be able to observe a very large area. This is needed because the interesting particles (the ones with the highest energies) are extremely rare. The arrival rate is about 1 cosmic ray particle per 1 square kilometre per 100 years.

That means, if you have a 1 km² detector, it will take you on average 100 years in between seeing the interesting events. In order to collect lots of data you can either measure for a very long time or build a very large detector. Actually, you would like to do both…

So, by going into space we can increase the size of our detector volume (the atmosphere -> detector area) and we also gain the additional benefit of not being stationary, only viewing either the north or the south sky. We get what we call full sky coverage.

Most of you have probably given up already so I’ll stop for now. But I’ll continue writing about our trip to the Utah desert.

JSPS Intro Day 1

Science stuff Posted on Wed, January 14, 2015 08:50:03

Yesterday was day one of the Orientation for the JSPS Postdoctoral Fellows. JSPS is the abbreviation for Japan Society for the Promotion of Science and can be boiled down to the guys who are paying me to be here.

This is a 3 day event which includes talks, Japanese lessons, dining, sight seeing, and also some fun. Or so they claim.

To start of, we are at a very nice hotel in central Tokyo and since I live about 500 m outside of the Tokyo 23 ward I get a room at the hotel.
We are about 30 fellows attending this meeting and the Nordic countries are well represented by two from Sweden and two from Finland. This is actually the second orientation I get invited to. I was unable to attend the first one which was in the end of November and I was told that I would not get a second chance, but here I am.

The program yesterday was filled with talks. I’ve listen to the history of the society, the JSPS Alumni project, and a talk by a second year JSPS fellow. They were all as one can expect. However, there were two great talks as well.

The fist was by Professor Richard Wilson entitled “Connecting in Japanese Culture, Words and Images”. Now I can admit that the title in combination with an 80 minute time slot for the lecture did not get my hopes up. However, Professor Wilson actually addressed this notion of the Japanese people and culture being very homogeneous society and showed that, both from a biological point and from a cultural point, this is not the case. This did turn out to be a very interesting talk and time flew by.

The second great talk was by a former JSPS fellow, Professor Richard Culleton. His talk was about working opportunities in Japan when the fellowship is over. This topic was perhaps not the most interesting one from my point of view. Although, Professor Cullenton is one of those people who can captivate an audience just by saying “Hello”.

After the talks were over there was a reception with some food and drinks. We had all been divided into different groups and after the dining was over there was a short quiz with ridiculous questions about Japan, but very funny. I now know that there are about 22 000 Onsens in Japan…

Obviously my team won and we even got a price. This nice combined ball point and mechanical pencil with JSPS printed on it
I am just about to head on down to start today’s schedule; Japanese class, group discussions and some touristy things in the afternoon and early evening.

Radioactive Rice

Science stuff Posted on Wed, November 26, 2014 11:22:36

So it’s been a while since
I’ve written something, sorry for that. This is mainly due to the fact that nothing of
interest has really happened. So being desperate I’ll tell you about Thursday two weeks ago (the 13th).

We were going to have a party at the department, a combination of
welcome party for me and a few others and a going away party for a guy
starting a new job on the 1st of December.

The idea was to have some food and drinks in the office. However, when
Marco realised that the rice we were going to have for dinner was from
Fukushima he suggested we test the levels of radiation, just for fun.

He prepared a small bag of rice and placed it in the detector we are currently developing here in the department.

After having measured the levels of radiation for a short while we saw
that it was about 150 Bq/kg. What we are measuring is the decay of
Cs-134 (Caesium) which comes from the Fukushima accident. Cs-134 has a
very short half-life, about 2 years (Which is short in comparison with
Cs-135 which has a half-life of about 2.3 million years).

150 Bq/kg is not a high number, the EU limits for consumables for adults
imported from non EU countries (except Japan) is 600 Bq/kg (For Japan
it’s 100 Bq/kg). Still 150 Bq/kg is higher than expected.

However, when we removed the rice from the detector. We realised we had
failed to remove one of the radioactive sources used for testing the
detector response… So when we removed the additional source, we got
much lower measurements, well below the 100 Bq/kg limits. And we could
start the party.

The radiation source which was already in the detector when we put the
rice in is not a dangerous source, unless you eat it or decide to keep
it in you underwear for a prolonged time. In addition the detector is
relatively shielded (to protect the measurement from background
radiation) so keeping the sample in the detector is not as careless as
it might sound. Although, not checking if the detector is empty before
starting a new measurement might whoever be considered sloppy.

There is also a big difference between a material being ‘radioactive’
and it being ‘irradiated’. Like the rice in the detector lots of every
day stuff have been irradiated, i.e. band-aids, and cotton swabs you use
to clean your ear (to name two). Just because something has been
irradiated does not mean it’s now radioactive. For instance, while the
light-bulb, hanging from the sealing in a room, is switched on, the room
is irradiated with light. But as soon as you turn of the light, the
room goes dark. It will not continue to glow by itself. In the same way,
the rice in the detector did not become hazardous due to it being in
the detector next to the radioactive source.

Happy birthday

Science stuff Posted on Tue, October 28, 2014 21:16:49

dear Riken, happy birthday to you!

Yes, on the 27th on October the Riken institute celebrated its birthday and in doing so gave all Riken employees a day of. So this past weekend was a nice three day week end for me.

How did I celebrate this you ask? Well not so much actually. During the weekend I met up with Björn, a former colleague of mine from the Particle and Astroparticle physics group at KTH in Stockholm. He was in Japan for a collaboration meeting and stayed a few days extra.

The majority of my celebrating Riken’s birthday was today, when I tried this Japanese version of KitKat. KitKat with flavour of wasabi.
I see now that the greenness of the bar itself is not as pronounced in the picture as it was. Not going to say what my verdict is, but I can say that I felt slightly nauseous after having eaten the first half. The second half is available if anyone wants it…