First muon detector "carpet" installed!


Today we received the first muon detector that we will fill with a liquid called "scintillator" next week. Next week we will also install the photomultiplier which will record the photons emitted by the passage of particles in the scintillator liquid.

Here some pictures from the delivery and installation, and a video from today, where we had not the best weather possible :)

Arrival of the aluminium tank at the ALTO prototype site can be seen in the following picture:


It was quite an easy installation of the muon detector, as it rolls on wheels:


And finally this picture shows the muon detector installed below the concrete layer at the ALTO prototype site.


First ALTO muon detector ready!


Finally the first muon detector is ready and we will receive it in the following weeks.

Here is a picture of the flat box, which is 10cm high and 3m in diameter, and which is quite a challenge to construct for the first time!

Now we are getting excited to receive and start operating this first muon detector that will take data with all the other existing channels!

Picture from Lars Tedehammar from TBS Yard AB in Torsås.


See some ALTO events in this video!


Here are some events seen in the prototype setup at Linnaeus University in Växjö. Thanks to Jean-Pierre we have a super event display!

We are still waiting for the final scintillator detectors, and as you may see, one Cherenkov tank is not active, as we need to replace the photomultiplier.

Most of the events are atmospheric muons, i.e. muons created in the atmosphere by the collisions of protons with the atomic nuclei composing the air.

On the right-hand side, one can see the detected charge given in milliVolt as a function of time and each colour corresponds to one detection channel.

The size of the spheres corresponds to the magnitude of the signal seen in each detector.

Have fun!

Muon detectors production started!


We are happy to announce that the muon detectors of the ALTO prototypes are currently under production in TBS Yard AB!

We look forward to receive them so that we can start testing them together with the water Cherenkov tanks at the prototype site.

Picture below from Lars Tedehammar.


Scintillators taking data together with the Cherenkov detectors


Waiting for the final large ALTO scintillator detectors which we now ordered, in order to do some tests, we equipped the prototype site with smaller plastic and liquid scintillators recycled from another older experiment in France.

Here below in the picture Jean-Pierre and Satyendra are installing a liquid scintillator box (in grey) at the top of of one water tank. Below the concrete structure you can see a second liquid scintillator box (still in grey).

This setup allows us, for example, to recognize the passage of a single muon from a particle cascade, so that we can check if the signals that we generate in our simulations agree with what we see in the real data. The other water tank is now equipped with small-size plastic scintillators.


Here below you can see two events hitting the prototype. The event on the left is an enormous particle cascade giving signals in all 6 channels (two water tanks, two liquid scintillators, two plastic scintillators) while the event on the right is a muon hitting vertically only the tank equipped with the liquid scintillators.


Data taking with ALTO water Cherenkov tanks ongoing since May the 25th


With a bit of delay, we are now updating the status of the ALTO prototype project on our Blog.

On May the 25th our two water tanks were completely filled with water and the data taking started at 17:00 the same day. So now we are smoothly taking data since more than three weeks.

This picture shows the moment at which the second water tank was completely filled; the way for us to know that the water had reached the top of the tank was to open the upper tap and see when the water started to come out.


And here is a water-Cherenkov coincidence event (a coincidence event is an signal seen in both tanks at the same time and therefore it is generated by a cosmic ray induced atmospheric shower) seen by the photo-multipliers inside the ALTO tanks: 


We already had some visits of the ALTO site on May the 31st, when 700 school kids visited the campus. They were of course all introduced to Astronomy and the ALTO project. :)


Filling of Cherenkov tanks with water started this morning!


This morning the city council employees helped us in setting up the water filling process. As usual, people are extremely professional here, and everything went perfectly fine. What we are doing now is a partial filling (of about 1m of depth), so that we can test a couple of different photomultiplier configurations. When we are finished with these first tests in water, we will complete the water filling of the tanks, and this will be on Wednesday next week. It will take about 4 hours to fill the two tanks in this first partial filling step.

The first picture shows the hose arriving at the top tap, as we are filling from the top in this first step.


This picture shows the water going inside the tanks, and (luckily) not hitting the photomultiplier.


First air-Cherenkov coincidence event between ALTO tanks with the full DAQ chain!


Today Jean-Pierre and Michael installed all the Data Acquisition System (DAQ) in our electronics box and the network has been connected by the IT at the University. So finally at about 18:00 CET we were able to see the first signals coming from the ALTO tanks in our control room.

These signals are generated from the passage of relativistic particles present in the atmospheric showers which enter inside the ALTO tanks. The passage of these particles in the air contained in the tanks generates Cherenkov light which is then detected by our photomultipliers positioned at the bottom.

Now we are able to control everything from the control room and next big step is the filling of the tanks with water!

The plot shows a coincident event, i.e. an event seen at the same time in both tanks, 0 and 1 being the preliminary names of our channels. The X axis is the time in nanoseconds and the Y axis represents the number of millivolts measured in the photomultipliers.