Type of contract
Internship contract for a period of 5 months within the EGO Optics laboratory, funded by the EGO Consortium.
The activity may start on February, 2018.
The Virgo interferometer is the most sensitive gravitational-wave detector in Europe. It was realized in partnership between the French and Italian institutes CNRS and INFN. It involves a wide collaboration of almost 250 scientists and engineers. After a deep modification of the interferometer, to give birth to a new generation detector called Advanced Virgo (AdV), and after the successful science run together with the LIGO detectors, the instrument is now being commissioned to become fully operative for the second stage of sensitivity improvement.
The EGO consortium (European Gravitational Observatory), located in Cascina, near Pisa â€“Italy, hosts the Virgo detector and has been also deeply involved in the design and construction of Advanced Virgo. In particular, the Optics Group of EGO Interferometer Technology Department is in charge of the input optics (INJ) and scattered light control (SLC) system for AdV. The responsibilities of the Optics Group have now increased with the commissioning phase, including the coordination of the whole laser and injection system, the sensing and control of the interferometer and a major role in the optical characterization group of the interferometer.
One of the main conditions to be fulfilled in order to reach the design sensitivity is to have a perfectly destructive interference between the beams recombining at the detector output. This condition can be satisfied only if the wavefronts reflected by the two arms perfectly cancel with each other.
However, it can happen that residual mirror defects can enhance high order modes resonating in the cavity: this would increase the Fabry-Perot cavity losses on the one hand and spoil the symmetry between the reflected fields, eventually preventing a perfect destructive interference between the wavefronts at the output of the detector.
In order to limit this effect, it is possible to correct the residual mirror roughness using an adaptive optics system based on thermal compensation. The basic principle of thermal compensation consists of changing the mirror shape by heating it up in specific points, correcting the unwanted defects.
A new system of thermal compensation, which has been developed in collaboration between the Optics Group and the Virgo Pisa Group is the Central Heating Residual Aberration Correction (CHRAC).
The CHRAC system is made up of a matrix of pixels emitting thermal radiation with a black body spectrum: an optical telescope images the correction matrix on the mirror surface which, in turn, absorbs radiation and deforms accordingly, following the projected correction map (see schematics).
The CHRAC prototype currently realized has been sized for Advanced Virgo mirrors (350 mm diameter), and is made up of 61 1cm2 ceramic resistors.
The residual mirror roughness, or surface map, can be decomposed in a base of polynomials called â€œZernike polynomialsâ€. Therefore, the ability of reproducing each element of the Zernike base allows also inducing any deformation given by their linear combination.
In order to reproduce on the mirror surface a controlled deformation, a complete characterization of the system is needed. This consists of a first â€œcalibrationâ€ phase of each actuator (resistor) and then a following phase where more complex deformations are induced, from the Zernike polynomials to any kind of deformation maps.
The student will be in charge to set up the CHRAC and to carry some tests to validate its functioning. She/he will have the opportunity to work on various aspects of the fields: mainly optics, but also to collaborate with the electronics and mechanics groups at EGO.
Applicants should be in their last years of study in optics or physics. The work will be at a level of Master thesis (equivalent to thesis for â€œlaurea specialisticaâ€ in Italian).
English required. Good attitude to experimental work is mandatory, familiarity with control systems and related hardware/software will be an asset.
European citizenship, no criminal convictions.
Place of work
EGO - European Gravitational Observatory - via E. Amaldi n.5 cap 56021 Loc. S.Stefano a Macerata - Cascina (Pisa) ITALY.
This internship will be carried out in the Interferometer Technology Department in the Optics Area.
Considering the lack of public means of transport to reach the site, it is preferable having a car.
How to apply?
Interested candidates are invited to fill in the Internship Application Form
and send it, together with the CV, to email@example.com
For the whole duration of the internship, EGO will pay a gross monthly wage of 500,00 euro and offer the lunch service at its canteen during working days to the student.
Interested candidates can have a look at all of the conditions of the agreement here:
For the Italian Universities: Internship Agreement with project
For the Foreign Universities: Internship Agreement with project
Closing date for applications
Until position is filled
Eric Genin, Ph.D.
Phone: +39 050 752 369