Andrey Ivanovich Panfilov passed away in his sleep yesterday. A legendary person. He was about to become a theoretician and to deal with superstring theory. However, once he got the task to develop a particular piece of equipment for the Baikal neutrino telescope. As a matter of fact, he invented the most part of devices being used here up to now. His untimely decease shocked all of us. He has always been a very creative man of inexhaustible energy. Everyone continues to speak about him as if he were still alive. May the blessed memory of this wonderful man and scientist stay with us forever…

Meanwhile, the camp life is going on. Rastislav’s winch is out-of-service after all. The handle has been broken off. The welder from land has already come, and now he is going to weld the handle. Rastislav has already explained him the task.

The handle is being welded.

A couple of minutes … the work is done!

Today, one of the strings of the third cluster is to be disassembled. It takes less than a day. Faulty main modules will be repaired and returned back. We will have a closer look at this process a bit later. New optical modules of the fourth cluster have to be deployed as well. Meanwhile, things are running along... There are a few newcomers from Moscow (INR). Surely, together we will perform our work even more efficient.

On the whole, our job is not complicated. Optical modules are spaced at regular intervals of 15 meters on the string. Every now and then, there is an acoustic module, which task is to detect its own location. If something is out-of-order, all the pieces are lifted one by one, taken apart, put into the boxes, repaired, and afterwards, placed on the string in the reverse order. In front of Maxim, you can see an acoustic EvoLogics module. It indicates optical module position with a centimeter accuracy.

Attaching points are marked. By reassembling all the pieces of equipment will find their fixed places again.

Now it is time to tell you more about optic modules of the Baikal GVD experiment. Each of them consists of two glass hemispheres. There is a photomultiplier tube (PMT) housed in clear gel that provides optical contact between the PMT and the glass surface of hemisphere. Next to the PMT, there is a high-voltage source, some electronics and many sensors monitoring both inside conditions (humidity, temperature) and module location.
The net made of special metal alloy surrounds the PMT in order to shield the Earth’s magnetic field. Otherwise, its correct functioning were almost impossible.
Moreover, there is a light-emitting diode inside the optical module, periodically flashing “upwards” to give a signal to the optical module above. It enables synchronized timing of these two particular modules, and therefore, of all the others. Besides, light detection sensitivity of the module is examined as well.

	This optical module has been “parked” in the depth for the whole year. Nevertheless, it looks like a brand-new one. In good condition, not damaged, not painted. In the past only weekly trips to the countryside. Second-hand dealers are asked not to disturb.
	Had we not made some arrangements beforehand, the ice were teeming with bloggers dreaming of taking the picture like this one. Fortunately, we have put flags around the campsite, and it keeps bloggers away.

Participants of the Baikal GVD experiments introduce every year some new ideas, improving technology, making it more effective and up-to-date.
Vladimir Rushai (DLNP) has developed an application that can scan QR code and store all the characteristics of optical modules in the database. Since QR code stickers have not been attached to every module yet, the application is being tested at the same time with the regular paper procedure of information input.
In this video, Vladimir and Maksim are scanning item numbers of optical modules’ elements and comparing them with those in the database. Everything is running smoothly. Maybe QR code would be replaced soon by a more advanced technology – RFID-tags. Then our life would be absolutely marvelous!

I feel deep pleasure having added to this “treasure chest” my own life hack. How to disassemble the optical module from the string? The device is perfectly round, 25 kg in weight, and it is very inconvenient to hold it. First, I held it by steel hoops with my fingertips. A rather uneasy task, I dare say: the module can slip out of the fingers, fall down, be smashed to pieces, and plunge into the lake… Moreover, we work all the time in the water: wet gloves, weary hands…
After a while, holding the third module, I started to ask myself and those around me why there are no convenient handles welded to the frame? Holding the fourth one, I had a brilliant idea: I formed two loops from the rope, passed them through small metal holes and got the safest way of holding wet modules. It works like this. All the other modules were disassembled only in this way. In the same way, we will hook them back.

Even the snow on the ice surface is outstanding. Let us have a closer look at it. These are snowflakes growing upwards like trees. What determines this particular shape of snowflake? The bright sun in the daytime, cold nights, low humidity. A matter of research!

We are going to lift up winches. Why? What for? Are you eager to know?

Our workday is over. We are sitting in an orange pick-up truck. The people are weary, but satisfied with their day. They had been able to do even more, they say.

To be continued…

P.S.: I am often asked what we do in our free time. Nothing special. Here lives a watchdog, called Rem. His favourite toy is a ring that usually helps to fix optical modules. Rem uses it in another way. He growls frightening, like a real wolf. However, beneath his surface, deep down, he is a good-natured lad. Writes poems in the evening. Plays guitar and sings. Thinks of eternity and …. of neutrino, of course.