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Ego-Virgo Experience

Bernieri Giacomo

Dohotar Andreea

Raffaetà Asia

9ᵗʰ-13ᵗʰ of April 2018

Cascina (PI)

EGO-VIRGO EXPERIENCE

 

We are three students of “Liceo scientifico Michelangelo” in Forte dei Marmi; we had the opportunity to join a project of the European Gravitational Observatory (EGO) in Cascina (PI). It hosts the Advanced Virgo experiment which consists on detecting the gravitational waves.

Advanced Virgo is a laser interferometer made up of two perpendicular three kilometers long arms, oriented to the North and to the West. When the gravitational waves cause a change on the arms’ length the laser beam undergoes an interference detected by the interferometer.

The gravitational waves are ripples of the time-space fabric; we know for sure that they are generated by the coalescence of neutron stars and black holes and it is supposed that also the birth of supernovae and the rotation of pulsars can generate them. The existence of these waves verifies the “General relativity” theory of Albert Einstein.

In order to observe the gravitational waves phenomenon it is needed a “noise” cleaning, so the last year a group of students begun to search for a spot with low magnetic noise in which they could place a pair of magnetometers: they found it on the north-est of the central building (CEB) (LAT: 43°37’54,6’’ N LON: 10°30’20,5’’ E).

Thanks to these instruments they managed to observe the Schumann resonances which are low frequency magnetic waves that interfere with the detection of the gravitational waves.

During the week from the 9ᵗʰ to the 13ᵗʰ of April trough some steps we connected the magnetometers directly to the central building for real time data analysis.

Schumann resonances

7,8 Hz ; 14,8 Hz ; 20,8 Hz ; 27,3 Hz…

Gravitational waves

Day 1

We were introduced to the EGO structure, to the security necessary for the dangers of this place and to the gravitational waves studies.T

hen we started to work on the device to connect the magnetometers to the CEB: as the magnetometers’ cables can not be longer than 60 meters but we needed to put them further we started to build a repeater paired with a chargeable battery all placed in a box.

The box was projected to contain:

- two printed circuits that both transfer the magnetometers’ signal to the CEB and charge the magnetometers;

- a chargeable battery directly connected to the CEB’s power line to charge all the box;

- a “chopper switch” which allows to switch mode of data detection;

- 4 LEDs to verify the functioning of the box components.

 

Day 2

We visited the inside of the Central Building while the staff explained us the operating and the usage of machineries.

We also continued the construction of the box: we learned to use different tools like the drill and the welder.

 

Day 3

We finished the box and then we placed it inside the CEB: we verified that all pieces could

work in the correct way and we connected the battery to the power supply of the building

and the magnetometers’ signal cables to the Analog to Digital Converter (ADC). So, we left it

there active during the night.

 

Day 4

We placed the box and the two magnetometers in plastic bags in order to put them on the ground and to protect them from rain. We oriented them facing the North and the West, as the interferometers’ arms.

We returned to our work station where we checked the data and we observed the spectrograms.

 

Day 5

We controlled the system functioning: even if the night before had rained everything was ok.

We observed the spectrograms related to the data acquired during the night and this day and we made a report.

 

Schumann resonances con be clearly seen in the north (N)

magnetometer spectrogram as light blue horizontal bands.

The same resonances seen with a bi-dimensional graph.

Comparison between the external magnetometers we installed and the

internal magnetometers (first two graphs) and coherence graph (third graph).

Magnetometers position.

Repeater/charging device.

Installing the magnetometers.

 

 

Installed and oriented magnetometers.

In conclusion we had an amazing week here; we are glad to have joined this great experience because we had the opportunity to apply our theoretical knowledge, we worked in such an exciting environment with a kind, brilliant and helpful staff, we learned many new things about topics not fully developed yet, we learned something about “unique” machines (interferometer, magnetometers…).

It had increased our passion for science.

We are grateful for the hospitality and we hope we would have such an opportunity again.

 

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