[CMS Labs] My experience as a CMS PhD student at Ghent University

Guest post by Amrutha Samalan

I started working with particle detectors during my Master's at the Central University of Karnataka, India. Although I always wanted to continue working in the field of particle physics, I never thought that I would end up as a PhD student at the world’s largest particle collider.

I joined the elementary particle physics group of Ghent University (UGent) in Belgium for my PhD in October 2019. The primary goal of my PhD is the upgrade of the CMS Resistive Plate Chambers (RPCs) for the High Luminosity phase of the Large Hadron Collider (HL-LHC). For me, this was a new turning point in my life. Everything around me was new and different from what I had experienced or seen until then. I was in a new country with a totally different culture and lifestyle. I knew very few people here. I ate food which I had never heard of or seen before. It was a journey both exciting and scary that I had set off. I thought that the transition to this new environment would be really difficult. But, I had my supervisor, colleagues and friends here to support me with everything and it was indeed a cakewalk with them at my side. On my first day at the department, my supervisor gave me a tour of the UGent CMS-RPC lab which is currently the main assembly site for new CMS RPCs. The lab is equipped with all the necessary facilities for the development, assembly, and quality control (QC) of the RPC detectors. It also has experienced technicians and a well-established workshop where a particle detector can be developed from scratch. I was so happy to see the lab and for the opportunity to explore and utilize all these facilities for the next four years. At the same time, the fact that I will be in charge of the whole lab and that I will be responsible for its smooth functioning frightened me a little.

The UGent CMS-RPC lab (top) and detector assembly room (bottom).
The UGent CMS-RPC lab (top) and detector assembly room (bottom).

As part of my learning phase, I began working with the existing RPC chambers of the lab and conducted different performance studies with them. The RPCs are gaseous detectors which consist of two parallel plate electrodes coated with a resistive layer and separated by a narrow gas gap. They are used in the CMS experiment as triggering detectors for muon detection due to their excellent time and spatial resolution. The upgrade of the CMS muon system for the HL-LHC includes the development of an improved version of RPCs, referred to as iRPCs, compared to the currently installed system and the installation of these detectors in the forward region of the 3rd and 4th endcap disks. As part of this, we assembled in Ghent two prototypes of the iRPC chambers in January 2020 with our colleagues from Universidad Iberoamericana, Mexico and University of Lyon, France. That was my first experience of building a complete detector and it was not an easy task. We had to tweak and adjust several crucial and sensitive components of the detector with extreme care. However, this helped me to learn many minor details that must be taken care of in detector developments and that experience was a great motivation and confidence boost for the many tasks that followed.

iRPC demonstrator chamber assembly taking place at UGent (me and Patrick Sennesael).
iRPC demonstrator chamber assembly taking place at UGent (me and Patrick Sennesael).

After the successful validation of these chambers, we assembled in July 2021 eight more iRPC demonstrator chambers as part of the iRPC demonstrator project. After the assembly, we conducted different QC tests to verify the chamber performance. This was a very exciting and responsible task which made me feel so satisfied upon its successful completion. We shipped the chambers to the RPC lab at CERN where further performance studies were done. Two of those chambers were installed in the CMS endcap during the first week of December. I was really looking forward to taking part in that installation, but oh so unfortunately my trip to CERN had to be canceled at the very last moment due to some new Covid-19 travel restrictions. Although I was really disappointed about not being able to participate in the installation at CERN, I was really happy to see the post-installation pictures of the chambers which I had developed mounted into the large CMS detector.

iRPC prototype chamber assembled at UGent, with from left to right Dr. Konstantin Shchablo, Amrutha Samalan (me), Dr. Salvador Carrillo (with loving memories of him), Dr. Michael Tytgat, Dr. Ricardo Lopez Fernandez, Tu Thong Tran, Dr. Imad Laktineh, Dr. Cecilia Uribe.
iRPC prototype chamber assembled at UGent, with from left to right Dr. Konstantin Shchablo, Amrutha Samalan (me), Dr. Salvador Carrillo (with loving memories of him), Dr. Michael Tytgat, Dr. Ricardo Lopez Fernandez, Tu Thong Tran, Dr. Imad Laktineh, Dr. Cecilia Uribe.
Installation of the iRPC demonstrator chamber in the forward region of the 4th endcap disk of the CMS experiment (Credits: CERN | Traczyk, Piotr).
Installation of the iRPC demonstrator chamber in the forward region of the 4th endcap disk of the CMS experiment (Credits: CERN | Traczyk, Piotr).

Next to detector production I am also participating in the study that is looking for alternative, eco-friendly gas mixtures for the operation of RPCs. During the two years of my PhD, I also got the opportunity to visit CERN to participate in different RPC related activities. I still remember my first time at CERN. That was a moment I had dreamed of a lot, and while standing in front of the main gate I couldn’t believe myself. For some time, I was still skeptical if it was real! The time I had spent at CERN was so beneficial to gain expertise in different aspects of experimental particle physics from detector development to its operation and data collection. It also gave me the opportunity to interact with other scientists, engineers, technicians and students from all over the world. I participated in a test beam campaign in October 2021 during which we tested both the iRPC and the ecogas RPC chambers at the gamma irradiation facility of CERN. The duty shifts we take during the beam time are of course literally sleepless nights with an intense workload. However, it is indeed an unforgettable experience to take part in many crucial detector activities, with the wonderful RPC team of CMS. This year, I also presented two posters on CMS-RPC upgrades at the TIPP 2021 and iWoRiD 2021 conferences. 

The UGent RPC team with the iRPC demonstrator chamber, with from left to right Dr. Michael Tytgat (site manager), Yves Israel (technician), Amrutha Samalan (PhD student, me :-), and Patrick Sennesael (technician).
The UGent RPC team with the iRPC demonstrator chamber, with from left to right Dr. Michael Tytgat (site manager), Yves Israel (technician), Amrutha Samalan (PhD student, me :-), and Patrick Sennesael (technician).

I realize now that I am still in the beginning of this journey and that there is a lot more to learn and many more milestones to be covered. Nevertheless, as a budding researcher, I am really happy for all the opportunities I received and thankful for where and what I am doing today. Many thanks to my supervisor Dr. Michael Tytgat for his endless support in all my steps and also to Dr. Deepak Samuel for his support and guidance in getting this PhD position. A big thanks also to my parents and friends as well for their everlasting love and continued support.


 

Moments with RPC colleagues during our test beam at CERN in October 2021 (Credits: Mehar Ali Shah, Ece Asilar and Irakli Lomidze).
Moments with RPC colleagues during our test beam at CERN in October 2021 (Credits: Mehar Ali Shah, Ece Asilar and Irakli Lomidze).