Laser-cooled Be+ for improved antihydrogen trapping and magnetometry.
Lead Research Organisation:
Swansea University
Department Name: College of Science
Abstract
We will laser-cool Be+ ions in a Penning trap adapted for antihydrogen formation and trapping. The laser-cooled Be+ will be used for two separate purposes to assist in the studies of antihydrogen. The first part of the project will focus on using the cold Be+ to sympathetically cool positrons, and thereby produce colder antihydrogen. This will allow increased antihydrogen production and the production of colder antihydrogen. This should also allow for the use of more positrons than were hitherto possible. With this assistance we expect to learn more about the formation process and ultimately increase the trapping rates of antihydrogen into a magnetic trap by at least an order of magnitude, something that will greatly accelerate precision measurements allowing for increased precision. Additionally cold Be+ will be used for in-situe magnetometry of the magnetic fields in our antihydrogen traps. Particularly for antimatter gravity measurements this is of great importance, but as the precision on the spectroscopy measurements increase knowledge of the magnetic field will ultimately limit the precision. A particular problem currently not addressed is measuring low magnetic fields, where the currently applied technique fails.
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509553/1 | 01/10/2016 | 30/06/2022 | |||
| 2224433 | Studentship | EP/N509553/1 | 01/04/2019 | 30/09/2022 | Joanna Peszka |
| EP/R51312X/1 | 01/10/2018 | 31/07/2024 | |||
| 2224433 | Studentship | EP/R51312X/1 | 01/04/2019 | 30/09/2022 | Joanna Peszka |
| Description | The objective of the project was to improve Be+ laser-cooling technique used in the ALPHA Experiment. Laser-cooling is an interaction of light with an atom or ion, which causes the atoms/ions to lose kinetic energy, which is associated with lowering their temperature. The primary motivation for laser-cooling Be+ is to reduce the temperature of positron plasma via interactions with cold Be+, which could be applied to an antihydrogen production scheme to improve cold antihydrogen trapping. Trapped hydrogen is s subject of fundamental study, in which we are trying to answer the question of why antimatter is so abundant in the observed universe. Measurements of antihydrogen are performed with high precision and it is necessary to well characterise the environment in which the experiments are performed. For the spectroscopy or gravity measurements with antihydrogen, we need to know the external magnetic field strength with high precision and accuracy. We proposed a new method for magnetic field measurement in ALPHA antihydrogen trap by measurement of the electron spin-flip transition frequency in Be+, which depends on the magnetic field strength. The electron spin-flip is induced by a microwave pulse at frequencies, which energies are close enough to the energy difference between two electron spin states in Be+. The initial state of beryllium ions corresponds to "spin-up" and it is also referred to as a "bright state" since this state is used for laser-cooling and ions in this state can be detected via fluorescence signal while interrogated with the UV laser used for cooling. When Be+ ions change their state to "spin-down", they stop interacting with the cooling laser and stop emitting photons - they are in a "dark state". By observing the fluorescence signal, we can detect the electron spin-flip during the microwave exposure and relate the signal drop to the frequency of microwaves that causes the transition to extract the value of the external magnetic field. The outcome of the work was the observation of the electron spin-flip transition in the ALPHA-2 trap, which allowed us to obtain the value of an external magnetic field in agreement and on a comparable precision level as the technique of Electron Cyclotron Resonance used so far in ALPHA Experiment. Within this project, I work on multiple technical upgrades to the 313 nm laser system used for laser-cooling beryllium ions. Among many, I investigated using the UV-fibres for delivery of the 313nm laser from the laser lab to the ALPHA trap (around 10 m long fibre). These UV fibres were custom-made by loading the hydrogen gas inside the core to prevent the fibre glass to degrade from UV light exposure. This technique is used by other ion trapping groups, but they use significantly shorter fibres (up to 1m) and fibres are bare without a jacketing. I used jacketed and significantly longer fibres and I found the transmission to be highly unstable. I find this work with UV fibres to be the most significant contribution to the research community that resulted from my project. |
| Exploitation Route | The work I performed and the hardware upgrades I implemented will allow ALPHA Collaboration to apply the Be+ laser-cooling to sympathetically cool positron plasma in a way that could be integrated with the antihydrogen production sequence. I designed the experimental procedure and demonstrated a feasibility of using laser-cooled Be+ as an in-situ magnetometer to measure the external magnetic field in the ALPHA Penning trap. The proof-of-principle experiment let us to obtain the values of external magnetic field with precision comparable with Electron Cyclotron Resonance technique used so far. This technique could be developed further to greatly improve the precision of magnetic field measurements and to characterise the strength of the magnetic field component of microwaves in the ALPHA Penning trap, which could improve measurements of the antihydrogen hyperfine structure. The particular contribution to general physics community is the work I performed with fibres for UV lasers. These fibres are not commercially available and they need to be custom made by experimental teams themselves. I studied the transmission of hydrogen-loaded LMA-PM-10 fibres with jacketing that were 10m long. The transmission was very unstable, but I developed ideas how this could be improved that could be tested in the future. |
| Sectors | Other |
| Description | Guide multiple tours in the Antimatter Factory |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Public/other audiences |
| Results and Impact | I was an official CERN guide for the Antimatter Factory and other locations at CERN: Syncrocyclotron, Magnet Test Facility, ALICE, ATLAS. |
| Year(s) Of Engagement Activity | 2019,2020,2021,2022 |
| Description | Outreach YouTube interview |
| Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Public/other audiences |
| Results and Impact | I was interviewed by a YouTube channel about my Ph.D. This has been viewed over 250,000 times. |
| Year(s) Of Engagement Activity | 2020 |
| URL | https://www.youtube.com/watch?v=Tw1Ef-dzU4w |
| Description | Outreach talk during iaps2CERN event |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Undergraduate students |
| Results and Impact | Outreach talk about ALPHA related research given to undergraduate students who came to CERN. This event was organised by the International Association of Physics Students. |
| Year(s) Of Engagement Activity | 2019 |
| URL | https://cern.iaps.info/ |
| Description | Outreach talks for Institute of Physics |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Undergraduate students |
| Results and Impact | An outreach talk on career paths to CERN. This was an online seminar for undergraduate students organised by the Institute of Physics. |
| Year(s) Of Engagement Activity | 2021 |
| Description | Podcast |
| Form Of Engagement Activity | A broadcast e.g. TV/radio/film/podcast (other than news/press) |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Public/other audiences |
| Results and Impact | This podcast was a result of being involved in guiding the Polish media representatives that were invited to CERN. The podcast was created by a host of a Polish radio show. |
| Year(s) Of Engagement Activity | 2020 |
| URL | https://open.spotify.com/episode/1R4oLRzbImsFBAE27Q4ruZ |
| Description | Radio interview |
| Form Of Engagement Activity | A broadcast e.g. TV/radio/film/podcast (other than news/press) |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Public/other audiences |
| Results and Impact | I was interviewed by a Polish radio station. This was a discussion about the then recent ALPHA laser cooling publication. |
| Year(s) Of Engagement Activity | 2021 |