In order for physicists at CERN to carry out their experiments for the understanding of matter, the large particle accelerator LHC must be operated with the utmost precision. Ensuring this precision both now and in the future was the overriding goal of a doctoral thesis that Claudia Tambasco recently completed at the EPFL in Lausanne. For this work, the young researcher was today (28.08.2018) awarded the prize of the Swiss Institute of Particle Physics (CHIPP) at a ceremony in Lausanne.
"I am honoured and very grateful to receive this prestigious award," says Dr. Claudia Tambasco. The 30-year-old Italian physicist received today the CHIPP Prize in Lausanne, which was awarded at the joint annual meeting of CHIPP and the Swiss Physical Society (SPS). Each year, the prize is awarded to a junior researcher for outstanding scientific achievement. It is the most prestigious award in the field of Swiss particle physics.
Claudia Tambasco receives the CHIPP Prize for her doctoral thesis, which she wrote between 2014 and 2017 under the direction of Prof. Leonid Rivkin, head of the Particle Accelerator Physics Laboratory (LPAP) at EPFL and Deputy Director of Paul Scherrer Institute (PSI). Dr. Tatiana Pieloni, researcher at CERN and a senior scientist at LPAP supervised Claudia Tambasco's doctoral thesis at the CERN site over the years and says of the researcher: "Claudia is curious and never gives up. This was also the case when the analysis looked almost impossible to address due to a missing calibration issue. Claudia is a team player, she always managed to bring experts from different groups together with a very good motivation." The CHIPP Prize jury honours the scientist „for her decisive contributions to the understanding of Landau damping and beam-beam effects at the LHC with Beam-Transfer-Function measurements that led to a substantial increase in luminosity", as it says in the laudation.
Favourite homework physics
Claudia Tambasco was born in 1988, daughter of a technician and an accountant in Rome. During high school, an experimenting teacher awakened her enthusiasm for the subject of physics: "When I did homework in high school, I always started with physics first, because that was what I enjoyed most. It was also clear to me which subject I would choose when I went to university," says Tambasco. She was the first member of her family to pursue an academic career. After five years she graduated from 'La Sapienza' university of Rome with a Master in Physics.
During her Master's thesis, the aspiring particle physicist spent six months at CERN working in the collimation team, a group of experts who watch over the quality of the proton beam circulating in the Large Hadron Collider (LHC), CERN's large particle accelerator, both clockwise and anticlockwise. The team takes care of the so-called collimator system made up of 108 mobile plates along the LHC beam - that shield the magnets and the other devices from the beam particles that deviate from the designed path and may cause damages. For her PhD thesis, Claudia Tambasco, decided to continue in the field of accelerator physics. She joined the Hadron Synchrotron Coherent effect section (HSC) in order to study the coherent motions of protons in the proton beam. Such coherent effects may result in a reduction of the desired performance of the present and future LHC and it is very important to understand and to keep them under control. While doing research at CERN, she also was a teaching assistant at EPFL for the course Introduction to Particle Accelerators. "Teaching was and is an activity that gives me a lot of satisfaction and makes me happy," says Claudia Tambasco.
Keep the proton beam stable
To understand the basic idea of Claudia Tambasco's dissertation, one has to realize that particle physicists use the LHC to shoot protons together to learn more about the structure of matter and the fundamental forces of the universe. Before the proton-proton collisions occur, two beams made of about 2500 packages of more than 100 billion protons each, circulate in the LHC at approximately the speed of light - one clockwise, the other counter clockwise. Whenever two packets meet in the collision point, which happens about 25 million times per second – typically 50 proton pairs collide. The particles emerging from these collisions are then examined by the physicists of the big experiments ALICE, ATLAS, CMS and LHCb at their relating collision points.
Claudia Tambasco is not directly involved in these experiments. As an accelerator physicist, Claudia Tambasco contributes to the improvement of the beam quality. "My job is to ensure the stability of the proton beam. This creates the conditions for the best possible results in the physical experiments." The stability of the particle beam is endangered when an electro-magnetic interaction occurs between the electrically positive charged protons and the metallic vacuum pipe in which they travel, that deflects the protons from their orbit and thus leading to beam losses. Landau damping, named after the Russian physicist and Nobel laureate Lew Landau, is a tool used to avoid these losses. Along the 27 km long accelerator ring, 168 special magnets ('Landau octopoles') are installed in order to suppress instabilities in the proton beam by means of Landau damping mechanisms.
Landau damping measured for the first time in the LHC
Landau damping has been used since the LHC went into operation in 2010. Nevertheless, not all the related phenomena are exactly understood. The thesis of Claudia Tambasco contributes to a better understanding of these phenomena. The physicist has examined the Landau damping in simulations. At the same time, the researcher and other scientists of the Beam Instrumentation group installed a device, called Beam Transfer Function system, that measured Landau damping for the first time in the proton beams of the LHC and thus compares the real data with the calculated values. Among other things, she was able to determine how the different configurations in the LHC impact on the Landau damping. The data acquired with the new device were used to measure the properties of colliding beams. Thanks to these measurements, new accelerator settings have been proposed to the Operations group, that led to significantly increase the luminosity (simplified: number of collisions per second) of the LHC.
The results of Claudia Tambasco are of particular importance for the planned 2026 upgrade of the LHC. With this upgrade, the accelerator's luminosity will jump upwards and it is important to ensure that the Landau damping of the proton beam also works under the new conditions of higher luminosity. Whether Claudia Tambasco will work at CERN, remains to be seen. Now, she is a postdoc at EPFL. As part of the EPFL team at CERN Claudia works closely with the Accelerator Beam Physics and Operations groups of the CERN’s Beams department. She lives in the Geneva area with her partner – an IT engineer – writing his doctoral thesis at the University of Geneva. Geneva – this is the spot where the action is in global particle physics...
Author: Benedikt Vogel
For her research Claudia Tambasco often worked in the LHC control room, which is located on French soil behind the Swiss-French border. In the following video Claudia Tambasco explains what she does there.
The CHIPP Prize is to reward annually the best PhD student in Experimental or Theoretical Particle Physics. In the evaluation, emphasis will be given to the quality of PhD scientific work and to its relevance within the student's research group, as well as to novel ideas brought up by the candidate.Image: CHIPP, Switzerland