1. Modernization of the TAIGA-IACT installation
In January 2020, a camera was installed on the mount of the second IACT of the TAIGA-IACT installation (Fig. 1.1), work was carried out on adjusting the mirrors and calibrating the telescope, after which it was included in the data set.
The second and third telescopes are equipped with hexagonal mirrors (Fig. 1.2), produced by the Italian company MediaLarioS. r. 1. The use of hexagonal mirrors allows you to increase the effective area of the mirror by almost 20%.
With the commissioning of the second IACT, the possibility of operation of two IACTs of the TAIGA-IACT installation in stereo mode was opened, among other things. Moreover, the distance between IACT1 and IACT2 is about 300 m (Fig. 1.3), which is about three times more than in the VERITAS, H. E. S. S., and MAGIC installations.
In May 2020, the assembly of the mount of the third IACT of the TAIGA-IACT installation made in the JINR nuclear power plant was carried out (Fig.1.4).
The following works were also carried out to prepare the third IACT of the TAIGA-IACT installation:
(1) a 2 x 220v power supply line and an optical line for control and data transmission were laid from the data collection center 4 of the TAIGA-HiSCORE cluster to IACT2;
(2) a switchboard for connecting optical and power trunk lines and metal cable channels along the telescope structures and up to the switchboard;
(3) end sensors and encoders for turning the telescope axes were installed, the alignment of the encoder axes was adjusted and a telescope;
(4) the lid of the detector container is manufactured;
(5) cable lines are installed on the telescope structures;
(6) the power supply and heating unit of the telescope detector is mounted and crossed in the electronics container, the power controller, the network switch, the thermal stabilization system are installed, the electronics container on the telescope plate is crossed and switched;
(7) fasteners were made and an electronics container was installed on the telescope fork, a motion controller, network equipment, and a heating controller were installed in it;
(8) the telescope mirrors were installed and adjusted, while a number of problems were solved due to the change in the design of the telescope dish and the fact that MediaLarioS.r.l. (Italy) made mirrors of a hexagonal shape, and not round as on the IACT1, made, mounted, and the system of protection of mirrors from freezing is configured;
(9) a thermally stabilized electronic unit is mounted on the telescope plate, which ensures the distribution of power supply to all nodes of the IACT2 (except for the drive motors of the telescope axes).;
(10) a traverse and slings are made for mounting the camera on the telescope;
(11) containers for balancing the telescope are made and installed; an adjustment screen with a movement mechanism is made.
The power supply of the TAIGA-IACT IACT3 is provided from the AC power supply. For this purpose, a 4x10sq.mm 520m VBSHV cable is laid from the data collection center. The cable is inserted into the container Fig. 1.5.
There are also optical data transmission lines from the data collection center 4 of the cluster of the TAIGA-HiSCORE installation. Further, communications are laid to the panel for connecting the flexible cable channel trunks (Fig. 1.6).
The flexible cable channel is designed for laying communications between the stationary and rotating parts of the telescope. The flexible cable channel is laid with:
- Power cable 4×2. 5sq. mm;
- Cable for connecting the stepper motor of the vertical axis of the telescope;
- 4-core single-mode fiber optic cable of special design, allowing bending at low temperatures;
- 4 4x-pair Ethernet-Patchcord;
It was planned to install a camera based on semiconductor photodetectors (SiMP) made at the University of Geneva, however, due to the covid-19 pandemic, this was not possible. Currently, the production of an upgraded camera based on the FEU XP 1911 for the IACT3 is being completed. During its manufacture, the following works were performed:
1. a sealed camera body with climate control and daylight protection systems was made;
2. a crate for the camera electronics was made;
3. a matrix for registering the Cherenkov image of the EAS was assembled on the basis of 560 XP1911 FEU equipped with Winston cones;
4. the camera’s read-out electronics were assembled on the basis of ASIC MAROC 3 chips;
5. the camera’s DAG electronics were assembled on the basis of DRS4 chips;
6. the system electronics were assembled control and power supply of the camera;
7. the camera has been debugged, configured, tested, and calibrated.
The camera matrix consists of 560 photomultipliers, which are grouped into clusters. The photomultipliers were pre-calibrated, their main parameters were measured: gain, photocurrent, dark current, etc. Photomultipliers are grouped by the product of their gain and photocurrent. For photomultipliers, the voltages are selected at which the product of the gain on the photocurrent is close to the average photocurrent for all camera photomultipliers multiplied by 10^5.
After all the work is completed, the camera will be installed on the third telescope TAIGA-IACT and the telescope will be switched to data set mode.
2. Modernization of the TAIGA-HiSCORE installation
In 2020, work was completed on the commissioning of 3 clusters and the full deployment of 4 clusters of the TAIGA-HiSCORE installation consisting of 32 optical stations. The installation of Cherenkov containers and containers for optical station electronics was carried out (Fig. 2.1), the platforms for the stations were filled with sand and gravel mixture, log cabins were assembled, frames were installed, the bodies of Cherenkov containers of optical stations with Winston light-collecting cones and containers for electronics were installed, and the stations were fully equipped with electronics. The 128 R5912 PMF manufactured by Hamamatsu were tested and installed in all 32 optical stations of 4 clusters.
The TAIGA-HiSCORE installation cable communications network was completed. To connect cluster 4 and the third IACT, a power supply line and an optical communication line were laid from the data collection center of the TAIGA gamma-ray observatory pilot complex to the local data collection center of Cluster 4 (red line in Fig. 2.2). The work included the following stages:
- Geodetic marking of the route. This type of work is necessary for the optimal location of the new power cable on the ground relative to the existing equipment, taking into account the minimum physical and financial costs of carrying out the work;
- Digging a trench with mechanized equipment. The work was carried out by a mini-excavator (Fig. 2.3). The equipment was operated by two people, replacing each other every 3-4 hours.
- In a swampy area, the bottom of the trench is filled with a thick layer of sand.
- Laying the power cable in the trench. This work was performed manually without the use of machinery (Fig. 2.3).
For the transmission of control commands and measurement data, a fiber-optic line is laid for communication over the Ethernet protocol between the center of the 4th cluster and the Central DAQ of the TAIGA Gamma Observatory. Fiber-optic and power cables are also laid from the data collection center of cluster 4 of the TAIGA-HiSCORE installation to all optical stations of this cluster and to the third atmospheric Cherenkov telescope of the TAIGA-IACT installation. All the work on welding of fiber-optic cables at optical stations has been completed.
To increase the sensitivity of the TAIGA-HiSCORE installation, when registering sources with different declinations, special mechanisms are installed at all optical stations 3 and 4 of the TAIGA-HiSCORE cluster (Fig. 2.4), which allow changing the inclination of the optical stations relative to the vertical axis. So, to observe the Crab Nebula, the optical stations turn 25 degrees to the south. The drive of the tilt mechanism of the optical station is implemented on a DC motor.
The end positions are limited by the sensors. The tilt system is controlled by the OM controller (Fig. 2.5).
To do this, the controller’s firmware has been modified accordingly. To implement this function, unify it with other programs, and improve the quality of information display, a new program for Linux OS was put into operation (Fig. 2.6). The OM management program for HiSCORE for Windows was created for debugging purposes. In 2021, the rotary mechanisms will be installed on all optical stations 1 and 2 of the TAIGA-HiSCORE cluster.
Thus, in 2020, the deployment of the TAIGA-HiSCORE wide-angle low-threshold Cherenkov installation has been fully completed, the number of its optical stations has reached 120, and the effective area has exceeded a square kilometer, which should more than double the statistics of recorded EAS generated by gamma quanta with an energy above 50 TeV.
3. Completion of the modernization of the Tunka-133 Cherenkov plant in order to increase its effective area to 5 sq. km
In 2020, the following works were completed. The electronics and cable communication lines of the optical detectors were repaired (Fig. 3.1). The main malfunctions are connected with breakages of signal (coaxial) cables, power and control cables, failure of control controllers, voltage dividers, and preamps. Heating controllers (~ 30% of the total number), radio modules (~ 20% of the total number), FADC boards (~ 15% of the total number) were also repaired and replaced on 6 external clusters of the installation.
During the summer period of 2020, the supports optical detector by 68% were replaced, 8 engine compartment covers and 7 metal structures were manufactured and installed to replace the faulty ones, in order to protect the optical detectors and cable communication lines from the negative impact from cattle (Fig. 3. 2).
In addition, work was carried out to repair all the boxes of the installation electronics, manufacture and install the covers of the transformer compartments inside these boxes. (Fig. 3.3).
Thus, as a result of the modernization of the Cherenkov Tunka-133 installation with 100% of the installation electronics and 100% of the optical detectors working properly, its effective area has been increased to 5 square kilometers. At the present time (season 2020-2021), measurement sessions are conducted on a regular basis in accordance with the observation schedules.
4. Completion of work on increasing the sensitivity of the MASTER robot telescope, through the creation of a new MASTER-600 robot telescope
The installation of the new MASTER-600 telescope was completed in October-November 2020 (Fig. 4.1). The diameter of the telescope is 600 mm, that is, one and a half times higher than the first domestic robot telescope MASTER-400. Aperture 2.1. The photometer is equipped with two QHY 6060 CMOS cameras.
Tests have shown that the domestic robot telescope MASTER-600 (Fig. 4.2), which was put into operation, significantly exceeds the capabilities of its predecessor MASTER-400, which formed the basis of the first-generation MASTER Global Network. Recall that the fully robotic high-power wide-field telescopes MASTER are designed to study the most powerful, fast-flowing explosive processes in astrophysics and physics. These objects are sources of hard gamma-ray radiation (gamma-ray bursts), high-energy neutrinos (supermassive black holes), gravitational waves (colliding black holes and neutron stars), and fast radio bursts (of as yet unknown origin). In addition, the unique software allows you to discover new objects of 10 astronomical types: from supernovae to comets and potentially dangerous asteroids. This mathematical software developed by MSU scientists under the guidance of Professor V. M. Lipunov allows almost all the work up to the publication to be carried out in automatic mode.
The sensitivity of the telescope increased by 6 times (approximately two stellar magnitudes). Thus, the available volume of the Universe has increased by 15 times, respectively, the efficiency of the Tunka Astrophysical Center for ultrafast optical observations has increased up to 15-20 times, depending on the type of objects. Fig. 4.3 shows the first image 5 of the Andromeda galaxy, taken by the new MASTER-600 robot telescope as part of the MSU-ISU Astrophysical Complex.