We work among extraordinary people doing extraordinary things; get to know some of them by reading these quick-fire interviews.
Name: Sparshita Dey
Job title: DPhil Particle Physics
What are you currently working on?
The LUX-ZEPLIN (LZ) experiment is an experiment where we use direct detection techniques in the pursuit of ultimately ‘observing’ and constraining dark matter models. Situated deep underground (4850ft) in the same gold mine as the historic Homestake experiment, lives the heart of LZ, a dual-phase xenon time projection chamber. It is an intricate piece of technology which is sensitive to collisions of external particles be it neutrons, electrons or dark matter for example, with the bulk liquid xenon in the active volume of the detector. The TPC is broken up into volumes characterised by strong electric fields, producing two signals: a prompt scintillation signal (S1) and a secondary ionisation-induced scintillation signal (S2). This occurs when ionisation electrons drift up in the chamber to a gaseous phase with a much higher electric field, incurring collisions and releasing more light. The light is then ‘collected’ by PMTs, providing us with the means to reconstruct events inside the detector and giving us a direct snapshot of particle interactions occurring within. My research is centred around the study of the electric fields in the TPC. As with many rare event/particle searches, accounting for and understanding background sources is vital in order to be able to have confidence in what constitutes a ‘signal’. The fields affect the appearance of the waveforms of the S1, S2 signals we rely on and the ratio of S1/S2 signal areas is how we usually determine whether we have a background-like particle (electronic recoils) or a signal-like particle (nuclear recoils). Further, high voltage systems and electrodes is in itself a very interesting area to explore; riddled with practical challenges and theoretical unknowns, the study of field and electron emission mechanisms have applications, beyond just background studies for dark matter searches and time projection chambers, in nanotechnology or even medicine. Fields and backgrounds characterisation then provide a great opportunity to explore elements of theory but also test these predictions via simulations and extensive data analysis methods using real data.
I am also involved in another experiment, Hydrox, which looks at doping liquid xenon dual phase time projection chambers (like the technology used in LZ) with hydrogen to increase sensitivity to low-mass dark matter models. This experiment is based in SLAC, Stanford, and it has been a great opportunity to be able to work with the group there and get involved with more active hardware/experimental design-related work, again incorporating knowledge on fields, background mitigation techniques and materials.
Describe a typical day
Few mornings start without a hot cup of chai. I usually have most of my meetings in the afternoon/early evening so the rest of the day is spent in getting things done from a general ongoing list of things I want to work on; this is usually a combination of mainly data analysis/ simulation-related tasks. We have to present updates to various groups quite often so most days I am also trying to compile my work into a presentation as I produce various plots. I aim to start around 10 am, beginning my day by checking and responding to any important emails and Slack messages. As a lot of my work is computer-based, I can work remotely if I want to. In a typical week, I’ll be in and out of the office as a result. Sometimes I like to work in cafes, sometimes at home (especially if I have a presentation later in the day), sometimes in a library (I really like the Rad Cam when my attention span permits me to effectively get work done) but my favourite is probably St Johns’ Kendrew Cafe, which is again perhaps more due to the nostalgia of the many all-nighters pulled with good friends in the past, which made them much more bearable. If I am in the office, often the whole group takes lunch and coffee breaks together. We usually use this time to talk about interesting physics or just have general life conversations. After afternoon meetings, I’ll continue working on my analysis tasks until around 5pm and head home. Usually I may have an hour or two of tutoring lined up or marking/solving tutorial problem sheets in preparation for any tutorials I may have to deliver in the coming days. Other than that, I occasionally take a break and go to the gym for an hour or so or spend some time with friends just chatting, drinking tea before going back home and working until around midnight/1am. Sometimes I like to take a walk before I go to bed, but my day often ends with watching some Netflix (right now I’m back to my animé phase) and calling my family members which works out great because of time zones.
If you had an entire day at your disposal (not at work), what would be your ideal way to spend it?
I would probably spend it making music. I love making trapsoul-type beats in my free time but whenever I do, it takes up a good chunk of the day so would be one of my go-tos if I had the time. I enjoy baking, especially experimenting with desserts; currently I like putting taro in everything so I’d probably try and make something involved like a taro and coconut babka which has been on my radar for a while. I also really enjoy ballets, operas, classical music concerts and plays, so ideally I would end the day by catching a show with a few friends and just catching up afterwards.
What is your favourite place in Oxford?
This is a very tough question! I have a few favourite places for different things. My favourite coffee place/chill zone is a tucked away cafe called 101 Coffee/Edge in Jericho; it’s cute and small and the coffee is great. For walks, I love the whole Cornmarket-Street-High-Street-Westgate round especially in the winters and in the evenings when the city is decorated with lights and Christmas decorations. Otherwise, in general it would probably be Cowley. One key reason is because whenever I get a kunafa craving (which is more often that you’d expect), I can find it at Zaatar Bake. Other than that, the area is just really lively and slightly different from central Oxford. It reminds me a bit of home in Birmingham and I have a lot of fond memories from when I used to spend vacs in undergrad with my close friends who used to live there.
What discovery would you like to see in your lifetime?
Perhaps it would be too obvious to say dark matter but this would truly be an amazing discovery, opening up so many new avenues and doors for the further exploration of physics.