Physics with Trapped Antihydrogen

Lead Research Organisation: Swansea University
Department Name: College of Science

Abstract

Understanding the origin and evolution of our Universe has been at the heart of scientific endeavour for centuries. Recent decades have seen major advances, as physics and cosmology have combined to produce the beginnings of a coherent picture. Our Universe seems to have been born in a cataclysmic event called the Big Bang, and has continuously evolved over the 13-14 billion years since then. Though much of the visible Universe can be explained, there are still many profound mysteries, including the existence of antimatter, and its fate.

Simply put, antimatter is an enigma. Whilst the symmetry of the laws of physics, and in particular quantum mechanics, predict its existence on a more-or-less equal footing to matter, the Universe appears to be composed only of the latter. Addressing this conundrum is one of the great challenges of basic science. As the Universe cooled after the Big Bang it appears that all the antimatter vanished, but leaving a tiny excess (one part in a billion) of matter from which the entire material Universe is created. The problem is we don't understand how this came to be. There are asymmetries in the behaviour of matter and antimatter, but they are too small by many orders of magnitude to account for the existence of matter in the Universe.

One way to address this problem, and the way we have chosen, is to study antihydrogen - an atom that the Universe never got the chance to make - and compare its properties with those of hydrogen. Recently, we have made great progress. We are now able to gently mix antiprotons and positrons to create some antihydrogen atoms with low enough kinetic energies to be held in a magnetic minimum neutral atom trap that is only 0.54 K deep. This trap is formed by magnetic fields from a complicated coil arrangement that forms the field minimum in the centre of the antihydrogen production region. Antihydrogen, like hydrogen, has a tiny magnetic moment - think of the orbiting positron as a tiny current loop - such that the energy levels shift in an applied magnetic field. Those atoms whose potential energy increases in the field will prefer to sit at the magnetic field minimum, and may be trapped. We have been able to confine anti-atoms for 15 minutes or more if required, so we are sure that they are in their ground state.

In a landmark experiment we have performed the first ever study of an anti-atom by bombarding the trapped antihydrogen with microwave radiation. The frequency of the microwaves was tuned to a resonant transition that forced the anti-atoms into a quantum state that could not be held in the trap. The result was that the trap was emptied of the antihydrogen - but only when the microwave frequency was set appropriately. We were able to tell that our trap had been emptied, and also spot the annihilations as the antihydrogen hit the trap walls. We are currently re-building our apparatus to improve this experiment, and also to use lasers to address the spectrum of antihydrogen.

Although this capability has great opportunities, there is much work to be done before the properties of hydrogen and antihydrogen can be compared with precision. In this project we will start in this direction. If any differences are found, we will have discovered new physics, and perhaps come some way along the road to discovering the fate of antimatter in the early Universe.

Planned Impact

Impact comes in the form of beneficiaries of the work. Direct academic beneficiaries have been covered elsewhere. Others include the stakeholders in the research, the students and staff who participate in the research, those who benefit from the output of trained personnel and the wider public.

Important UK stakeholders are the (now) three Universities involved and the EPSRC itself, and internationally, CERN. During the last few years, together with the press/marketing offices of the respective universities, we have coordinated the release of publicity concerning our progress with the EPSRC. This was a stated aim in the last grant proposal, and we believe it to be beneficial in raising the profile and role of the organisations involved, and in promoting science to a wider community. We will continue this activity, as appropriate.

Direct benefits accrue from the personnel who are trained via participation in our research programme. At the postgraduate level, students have a unique opportunity to interact with physicists from a range of sub-disciplines and to work for extended periods at CERN, the world's flagship physics laboratory. The demanding scheduling and attention to detail required for the beamtime shift work gives these students an edge to their repertoire of skills. They are entrusted with the charge of sub-tasks, the results of which are used by the entire collaboration, and in so doing develop leadership skills at this early stage of their careers. Postdoctoral workers have similar opportunities. Significant sub-tasks are delegated to them, and they are required to lead individual shifts and eventually to assume a temporary run coordinator position, where they are responsible for delivering the agreed scientific/technical milestones of the collaboration over a period of typically 1-2 weeks. Our young researchers have all gone on to successful careers in academia and industry.

We are fortunate that public interest in antimatter continues to be buoyant. Given that societal aims are to raise the public awareness of what scientists do, and why, and to promote science to youngsters, our work is potentially beneficial in this context. We are working (with EPSRC "Pathways to Impact" support) to develop a software suite in which users can perform simulated antihydrogen formation and trapping experiments, as well as (eventually) find educational material on antimatter. We have successfully trialed this software in June 2013 in master-classes (Swansea holds regular particle physics master-classes), and we intend to develop the package for wider use, hopefully to include schools and colleges.

Members of the team are active in outreach in the UK, and beyond. Talks on antimatter are frequently given to local scientific and astronomical societies as well as to organisations such as IOP Branches and University Physics Societies. Van der Werf continues in his role as a STEM Ambassador. CERN-based colleagues frequently host tours of the Antiproton Decelerator complex (more than 10% of the visitors are from the UK) where the display of the original antihydrogen apparatus always attracts attention. We will continue to undertake such activities, which we consider to be an integral part of our work.

Publications

10 25 50
 
Description We successfully observed the 1S-2S transition in antihydrogen for the first time. We have also measured the ground state hyperfine spectrum.
We have also developed novel methods to investigate the effect of gravity on antimatter and to investigate whether antihydroen has a residual charge.
Exploitation Route The current research involving precision measurements on antihydrogen and antimatter in general is of great importance to the antimatter field and can lead to better understanding of the basic questions about CPT symmetry and the fate of antimatter in the universe.
Sectors Culture, Heritage, Museums and Collections,Other

URL http://cern.ch/alpha
 
Description During the course of this project, we have contributed to a publication of significant academic importance which will inform the long-term work in this project and in general the field of antimatter studies. The measurements have had a profound influence on the field and are influencing other groups outside our immediate area of research. Significant outreach opportunities have ensued.
First Year Of Impact 2017
Sector Other
Impact Types Cultural

 
Description CERN teachers programme for welsh teachers
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Influenced training of practitioners or researchers
Impact The welsh teachers programme at CERN, spear headed by Swansea in collaboration with Lynn Evans (former head of the LHC programme) highlighted the need to enthuse physics teachers in Wales. Funding for this programme and others has now been granted by the Welsh government under the NNEST umbrella.
URL http://gov.wales/newsroom/educationandskills/2017/welsh-teachers-return-from-cern-to-teach-what-matt...
 
Description Published Book " Trapped Charged Particles - A Graduate Textbook with Problems and Solutions"
Geographic Reach Multiple continents/international 
Policy Influence Type Influenced training of practitioners or researchers
Impact The book is used as reference material at the winter schools on "Physics with Trapped Charged Particles", the next of which will be hosted in january 2018 (the previous one was in 2015). These schools reach primarily European level post-graduates (Ph.D. students and young researchers), with a few intercontinental participants (US / Asia / Brazil). We have received good feedback on this. No further quantitative feedback available at this time.
 
Description EPSRC Standard Grant (Responsive Mode)
Amount £3,824,192 (GBP)
Funding ID EP/P024734/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 03/2017 
End 03/2021
 
Title SDR-EVC 
Description We have successfully combined the known techniques of Strong Drive Rotating (SDR) wall and Evaporative Cooling (EVC) to develop a new technique that we have dubbed SDR-EVC. The technique allows tailoring non-neutral plasmas held in Penning traps on all their parameters except their temperature (i.e. you can tailor their number, density and size). The technique is particularly useful in connection with use of positrons, as it allows one to stabilize the number of particles for experiments with positrons, that are often accumulated in a fashion that cause some fluctuation in the number, density and size of what's accumulated. 
Type Of Material Improvements to research infrastructure 
Year Produced 2018 
Provided To Others? Yes  
Impact This new tool has assisted in the development of new techniques for trapping antihydrogen that has allowed an order of magnitude increase in the rate at which we can trap antihydrogen. It has also been of great use for allowing us to accumulate antihydrogen a trap and thus reaching much larger numbers than hitherto possible. Finally the stability it engenders has made the experiments on antihydrogen more reliable and reproducible facilitating a number of recent breakthroughs in antihydrogen physics. 
 
Description ALPHA CERN Cryogenics 
Organisation European Organization for Nuclear Research (CERN)
Department CERN - Other
Country Switzerland 
Sector Academic/University 
PI Contribution We have developed a cryogenics control system for an 8-magnet superconducting magnetic trap, as well as a control and monitoring system for the magnets.
Collaborator Contribution CERN has provided 16 LHC High Temperature Superconducting leads for the realization of a magnetic antimatter trap, as well as providing cryogenics consultation and design support.
Impact Ongoing
Start Year 2012
 
Description ALPHA Collaboration 
Organisation European Organization for Nuclear Research (CERN)
Department ALPHA Experiment
Country Switzerland 
Sector Public 
PI Contribution As co-founders of the collaboration, we have provided funding and expertise in multiple areas of key importance to this experiment : Super conducting magnets, Lasers, Plasma physics, Trap physics, Antiproton physics, Antitrapping, Positrons, Positron accumulation, Cryogenics.
Collaborator Contribution Partners and expertise (in parenthesis) are come from Brazil (Lasers), Canada (Detectors/DAQ), Denmark (Lasers, Antihydrogen), UK (Detectors, Plasma physics plus the above), US (plasma physics, Simulation). The contributations are estimated based on 10 year running of the experiment with 30 academics contributing cash for running and maintenance and about 20 FTE's per year of running plus 3M of contributions of kit.
Impact This is an enormously successful collaboration having resulted in 4 Nature papers and a large volume of other papers as well as heavy representation in the media. It is physics-multidisciplinary in that the collaboration spans several normally separate areas of physics : cryogenics, plasma physics, atomic physics, particle physics, fundamental physics, laser physics, positron physics, and spectroscopy
Start Year 2006
 
Description CERN 
Organisation European Organization for Nuclear Research (CERN)
Country Switzerland 
Sector Public 
Start Year 2006
 
Description Antimatter Lectures and Tours at CERN 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Schools
Results and Impact I give antimatter related lectures on a regular basis for school groups from Wales, UK, Denmark and Finland. Typically I entertain a about 300 pupils per year this way. The lectures are followed by guided visits to the experiments, in particular the ALPHA experiment where UK is a lead contributor.
I have many repeat visits (same teacher, new students) - and both teachers and students give very enthusiastic feedback from these visits.
Year(s) Of Engagement Activity Pre-2006,2006,2007,2008,
 
Description Antimatter Matters exhibition at the Gravity Fields Festival in Grantham 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact The Antimatter Matters Royal Society Exhibition was moved to the thirds gravity fields festival and participated in the activities in the Guildhall.
Year(s) Of Engagement Activity 2016
URL https://www.gravityfields.co.uk/CHttpHandler.ashx?id=17942&p=0
 
Description Article in Advances Wales (Welsh Government) 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact I participated in an article in Advances Wales showcasing our antihydrogen research.
Year(s) Of Engagement Activity 2016
URL https://businesswales.gov.wales/sites/business-wales/files/documents/Advances%2079%20final.pdf
 
Description Christmas lecture in Aberystwyth 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact I was invited to give a "fun and educational" Christmas lecture of a group of local schools (sixt form / A-levels) at Aberytswyth University.
Year(s) Of Engagement Activity 2018
 
Description Hosting schools at the Antimatter Factory (both for visits and presentations) 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Schools
Results and Impact We should around about 30 school classes per year with about 30 students in each in the experiment. Many of them also enjoy an introductory presentation about our experiments. The feedback is always very positive to the likes of "the antimatter visit was the best part", and the teachers report really positively about it. We therefore have a number of Schools who return annually or bi-annually and pre-emptively contact us to exactly get the "antimatter experience".
Year(s) Of Engagement Activity 2012,2013,2014,2015,2016
 
Description Manchester Science Festival 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact As part of the Manchester Science Festival the royal society invited us to present our Antimatter Matters exhibit. This was a great opportunity to reach further audiences with this activity that we had already tuned for schools and the general public.
Year(s) Of Engagement Activity 2016
URL https://royalsociety.org/science-events-and-lectures/science-exhibition-manchester/exhibits/
 
Description Royal Society Summer Science Exhibition : Antimatter Matters 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact In collaboration with about 10 other UK institutions members of the LHCb collaboration at CERN the UK ALPHA members (Swansea, Liverpool and Manchester) organised (Responsible organisers Prof. N. Madsen (Swansea), C. Lazzaroni (Birmingham), T. Shears (Liverpool) and C. Parkes (Manchester)) a stand/exhibit at the annual Royal Society Summer Science Exhibition. This is a competition based invitees-only exhibition (i.e. you compete to get invited to exhibit) and it's very professional (in both presentation and organisation).
A great number of schools visit the exhibit and also many members of the general public. A number of special events were also hosted,with MEP's as wells FRS.
The RS and well as ourselves collected feedback from participants who greatly appreciated and reported increased interest in science thanks to our exhibit.

We continue to tour the exhibit at various UK science events - so more events will be reported here.
Year(s) Of Engagement Activity 2016
URL https://royalsociety.org/science-events-and-lectures/summer-science-exhibition/exhibits/antimatter-m...
 
Description Royal society summer exhibition 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Exhibition about physics at CERN
Year(s) Of Engagement Activity 2016
 
Description Welsh and UK teachers programmes @ CERN 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact In collaboration with CERN's teachers programmes I deliver presentations and discussions on the subjects of our research (Antimatter) to UK high school teachers. Each year there are currently three teachers programmes (one week each, with about 25 participants) of which one has been focussed on physics teachers in Welsh Schools (A and AS levels).
These programmes help enthuse teachers to bring modern and contemporary physics into the class room as well as show them how they can bring their own students to CERN in an effort to highten their interest in STEM subjects.
In collaboration with CERN we have received very very positive feedback on this.
Year(s) Of Engagement Activity 2016,2017,2018,2019
URL https://home.cern/students-educators/teacher-programmes
 
Description Winter School on Physics with Trapped Charged Particles 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact In collaboration with Profs. Richard Thompson and Martina Knoop of Imperial College London and Aix-Marseille Universities respectively I have organised and chaired a winter school on physics with trapped charge particles in January 2012, 2015 and 2018. Each school is 10 days long with presentations and workshops by internationally recognized leaders in the field give to about 55 participants who are mainly Ph.D. students and some PDRAs. The school has been a great success each time and we will repeat it in January 2021. So far only limited external support has been received for this but we're organising it that L'ecole de Physique des Houches, which is a sort of charitable organisation for physics events.
Year(s) Of Engagement Activity 2012,2015,2018
URL http://indico.cern.ch/event/315947/