Efforts to test gravity, and more specifically, General Relativity, look in every corner and keep trying to push precision. A recent article in the Wired magazine focuses on a recent test of General Relativity in space, but puts those tests into a larger context of Lorentz invariance tests, in which also AEgIS gets a small mention.
AEgIS (and many other experiments at CERN) sometimes also host high school students, involving them in projects at the forefront of research, and for two weeks, giving them a first taste of what research really entails.
In the first-ever event for Austrian students, twenty four students selected among many applicants from high schools all around Austria participated during the last two weeks of October in the high school student internship program at CERN, working on a range of research projects (here's the list of projects). Two of them chose to work on the small side experiment Borealis with its source of C2- molecular ions, trapped in a Paul trap, continuing the work started by the summer students that had come a few months earlier to verify that these ions are in the ground state, a necessary precondition to being able to laser-cool them. The laser light of just the right color (energy) needed to excite them from the ground state to the neutral state is now at the point where the stability of that laser became the next important issue, and these two students spent a lot of their time here being involved in efforts to laser-lock the crucial laser (and being exposed to the sometimes frustrating challenges involved in doing research).
The students took it into their hands to define some further activities in addition to their work and visits of several experiments, and decided to talk with researchers to ask them about all the often very deep and difficult questions that they had about physics, research, and what it is like to work as a scientist. What was initially foreseen as a 1/2 hour discussion with our students Anja Schwab and Alexis Treitler turned into six of the students piling into my office for 2 hours, and then a second two hour question and answer session with all the students two days later. Their thirst for information, their enthusiasm and the level of their knowledge is amazing, and we look forward to next year's groups of students from Belgium, Denmark, Greece, Italy, Romania and Switzerland (2020 HSSIP countries).
Every year, the AEgIS experiment (and many other experiments at CERN) hosts several CERN summer students, involving them in projects at the forefront of research, and giving them a first taste of what research really entails. In contrast to university studies, generally, the problems being looked at by them don't have ready-made solutions. Instead, the students themselves have to use their knowledge, creativity and their ability to learn new tools quickly to come up with ways of completing their projects in only a few months.
This year, we are hosting two students, Kanako Narita and Ravindi Sannasgala Mudiyanselage, both of whom are working on projects surrounding our attempt at laser cooling an anionic system. The goal is to be able to cool antiprotons indirectly, by laser-cooling a negatively charged system. To date, no anionic systems have been laser-cooled, although of course atoms, positively charged ions, and a very small number of (neutral) molecules have been cooled to very low temperatures. Among elements, only La- apprears to be a possible candidate, although working with it in a magnetic field would entail many difficulties. That is why we have looked into alternatives, and here negatively charged molecules seem very promising.
A small side experiment to AEgIS (called Borealis) has built up a source of C2- molecular ions, and has trapped them in a Paul trap. The next step is to verify that they are in the ground state, a necessary precondition to being able to laser-cool them. In order to check for this, we will shine laser light of just the right color (energy) to excite them from the ground state to the neutral state; detecting the liberated electron will prove that indeed, they are in the ground state. This is where the students come in: both of them are deeply involved in setting up the measurement, calibrating the lasers and electron detectors, and preparing the attempt that will take place before the end of their time at CERN.
As part of their time at CERN, in addition to working in experiments and hearing lectures about physics and technology given by world experts, the students also have the occasion to present their work to others students and researchers, either through poster sessions or through public presentations; the photo above shows Kanako Narita presenting her research work within Borealis in CERN's Council Chamber.
at the London Science gallery on dark matter features work by the artist duo Semiconductor
based on photographic plates produced in AEgIS, and provided to them by us.
Here's the tweet from the Science gallery:
Our #ArtOfTheDay today is this “space-time lapse” in #DARKMATTER by @semiconducting. Using data from the #AEGIS experiment @cern, these delicate lines are actually collisions between matter and antimatter!#DARKMATTER #Physics #KingsCulturalCommunity
An animation can be seen here.
Although dark matter and antimatter are very different things (antimatter can be produced and studied in the lab, while nobody knows what dark matter actually is), both concepts are equally attractive to artists. The artist couple Semiconductor that spent several months at CERN as resident artists in the Arts at CERN program interacted with many groups and individuals, among them the AEgIS experiment. They were particularly drawn to the photographic plates that were recorded in the framework of a study on detecting antihydrogen atoms with the highest possible spatial resolution, that was carried out in AEgIS in 2014 and 2015. The plates had been scanned by the collaborating group at the University of Bern in tiny squares of 200 x 200 micron, stepping through the exposed and developed emulsion that had been exposed to very low energy antiprotons (that thus annihilated at the surface of the plates). The resulting annihilation fragments flew through the photographic plates, and allow detecting the point at which the annihilation between antiprotons and nuclei in the emulsion took place. The particular poetry of these spectacular disappearances are made visible in the (artificially grainy) movie that Semiconductor constructed from the numerous images supplied to them by us.
Antimatter exterts a pull on a wide range of visitors that pass by the AEgIS experiment, but it is
upon artists that the attraction is greatest. The most recent artist to pass by is Dustin Bates,
who founded the band Starset
and is also the band's lead singer, songwriter, and keyboardist.
Given his long-standing interest in astronomy and physics, it was only a question of time before he passed through CERN, and we were able to show him around the antimatter experiments, and AEgIS in particular.
Dustin Bates in front of the AEgIS experiment
A completely novel and fascinating call for breakthrough technology projects by the EU in the framework of the Horizon 2020 program was launched last year, and recently, the 170 winning projects (out of around 1500 submissions) were announced. The full list of fascinating and often revolutionary projects can be found here but for us, the most important aspect is that one of our submissions, called O-possum II (for "ortho-positronium surface scanning microscope") was funded!
Our project is built on the idea of using lasers to cool a very short-lived atom, positronium, which consists of an electron and an anti-electron. This atom, which only lives for 142 ns (about a tenth of a millionth of a second) is produced by shooting positrons into a custom-made nanostructured material (which is one of the key technologies of the AEgIS experiment), and comes out into a hemisphere at speeds of around 100 km/s. We want to use special lasers to bundle this wide cone and transform it into a narrow cone, ultimately a beam, with which material surfaces can perhaps one day be scanned. Laser-cooling of atoms usually takes many tens of thousands of photon-atom interactions, and thus takes time; luckily, positronium is very light, so although there is only very little time available for photon-positronium interactions, around 50 to 100 such interactions should be sufficient. By selecting a laser wavelength of 205 nm corresponding to a transition between the ground state and the 2P state, whose lifetime is around 1.5 ns, it might just be possible to sufficiently cool the positronium atom before it annihilates. Once it is cold enough, its lifetime can be extended by exciting it into a longer-lived metastable state.
Contrary to charged particle-based microscopy, a positronium microscope would be insensitive to electric fields in proximity to the surfaces to be probed/scanned. It can thus be used to study metallic as well as isolating surfaces. Furthermore, due to the very low mass of positronium, perturbations in the probed surface are not to be expected during the acquisition of an image. Most importantly, the presence of a positron in positronium, which will annihilate with any electrons present at the surface being probed/scanned, strongly suggests that a positronium microscope has the potential to sensitively map the distribution of electrons at the surface being investigated through detection of the annihilation rate as a function of the position of the focus of the positronium beam. This is a completely novel tool that should allow new insights into static and dynamic processes at intentionally patterned material surfaces, e.g. solid-state devices, nano-patterned assemblies, etc.
Come back here for regular updates on our progress over the course of the year during which this project will run (until May 2020)
To be useful for antimatter gravity experiments, a source of positronium atoms needs to produce long-lived atoms in large numbers, and with known velocities that can be controlled and are unaffected by disturbances such as electric and magnetic fields. The new AEgIS source ticks all of these boxes, producing some 80 000 positronium atoms per minute that last 1140 nanoseconds each and have a known velocity (between 70 and 120 kilometres per second) that can be controlled with a high precision (10 kilometres per second).
The trick? Using a special positron-to-positronium converter to produce the atoms and a single flash of ultraviolet laser light that kills two birds with one stone. The laser brings the atoms from the lowest-energy electronic state to a long-lived higher-energy state and can select among all of the atoms only those with a certain velocity.
This is not the first time that researchers have produced a source of long-lived positronium atoms. There are other techniques that do so, including one that involves bringing the atoms to electronic states called Rydberg states, and which could also be used to perform gravity experiments with positronium. But all of these are very sensitive to electric and magnetic fields, which influence the atoms’ velocity and would need to be factored into future gravity measurements. The new method devised by AEgIS is “cleaner”, in that it is almost insensitive to these fields.
This summer, AVA Fellow, PhD candidate and former technical student of the AEgIS experiment Milena Vujanovic, now based at the University of Liverpool, was invited to give an overview talk about her Marie Curie Fellowship and the MSCA ITNs in general at an event organized by the Ministry of Science in Montenegro.
Milena was asked to help organise an “Info day” as well as give a talk about Marie Curie ITNs to a group of students. She related her own experience as AVA Fellow with the wider targets of the MSCA ITN programme, and also explained how students can apply for early career stage positions) at institutions across Europe.
More information on the event can be found here.
Milena also writes a very well followed blog on her life as a scientist and providing career advice.
Our article ‘Producing long lived 2S positronium via 3P laser excitation in magnetic and electric fields’ was just published in Physical Review A.
Positronium is a metastable bound state between a positron and an electron. Positronium has two ground states, the single state (1S/p-Ps) and the triple state (3P/o-Ps). Both states have short lifetimes of around 0.125 ns and 142 ns, respectively and they decay rapidly. The ground states are purely leptonic two-body systems and their short life time makes them a very useful tool for high precision studies of Quantum Electrodynamics (QED). They are also a key ingredient to AEgIS' production mechanism for antihydrogen atoms.
All these experiments can highly benefit from an efficient and clean production of the 2S meta-stable state of Positronium. The experiment outlined in this new paper uses UV laser pulses in an experimental vacuum chamber in the presence of both, a strong magnetic field and a modest electric field, to produce long-lived 2S Positronium. The UV laser pulses excite the Positronium into the 3P/o-Ps level which then deexcites partially in the magnetic and electric field.
The paper also explores the three main de-excitation paths and discusses stark mixing due the presence of the electric field. It uses a novel analysis technique of the single short positronium annihilation lifetime spectra (SSPALS) to successfully detect evidence for the production of the metastable state.
Further information can be found at:
S. Aghion et al. (AEgIS Collaboration), ‘Producing long lived 2s positronium via 3p laser excitation in magnetic and electronics fields’, Phys. Rev. A 98, 013402 (2018).
The project AVA (Accelerators Validating Antimatter physics) is an Innovative Training Network within the H2020 Marie Skłodowska-Curie actions. The project was established to enable an interdisciplinary and cross-sector program on antimatter research, and was successfully launched today)
A complete overview of the project and the partners is here.
This training project will run over somewhat more than three years (until mid 2020); one of the AVA fellows, Mattia Fani, is
carrying out his research (that will lead to a PhD) in the AEgIS experiment, working on a number of cutting-edge technologies: advanced cold charged plasma manipulations, novel
scintillating detectors, and developments surrounding a beam line for ultra-low energy antiprotons (with energies of
less than 10 keV), allowing inter alia to test various highly sensitive detectors, among them diamond detectors.
Together Cheltenham Festivals and the British Council co-produce the FameLab International Grand Final held at the Cheltenham Science Festival each June. The 2015 FameLab International Final featured the winners of FameLab competitions held in twentysix countries (and one organization) across five continents. Nine of these international finalists were shortlisted in the semi-finals and went on to compete in the International Grand Final on Thursday 4th June in the EDF Energy Arena. The 2015 edition saw competitors from Australia, Cyprus, Czech Republic, Egypt, France, Germany, Greece, Hong Kong, Ireland, Italy, Poland, Portugal, Romania, South Africa, South Korea, Spain, Switzerland and the United Kingdom competing to be FameLab International Winner 2015.
The CERN winner Lillian Smestad, member of the AEgIS collaboration from the Norwegian Research Council, shared second place with François-Xavier Joly from France, who also was among the trainees at the FameLab Master Classes organised by CERN in April. Oskari Vinko, from ETH Zurich, who won the Swiss finals organised at CERN last May, is the winner of the 2015 FameLab competition. See the finalist video of Lillian here.
On 8 May, the joint CERN and Swiss FameLab final took place at CERN. The jury selected Oskari Vinko, a Master’s student in synthetic biology at ETH Zurich, as the winner of the Swiss final while Lillian Smestad, a physicist in the AEgIS collaboration, will be the first CERN finalist to go to the international final at the Cheltenham Science Festival. In addition, CMS physicist Christos Lazaridis was awarded the audience prize.
Lillian's talk about antimatter can be seen here.
A few weeks ago, the video artist Jeff Frost came to CERN to collect material for the video he was shooting the the world tour of U2 (starting on May 15). Among the several places he shot material from was the heart of the AEgIS experiment, fortuitously open during the days he was at CERN. His preparation in filming the experiment can be seen here and here. Jeff had a great time at CERN, and sent us the following kind words:
"I just wanted to say how amazing my week at CERN was. It was something that I’ll remember forever. I could have spent months on end shooting and learning about every experiment. The incredible initiative and effort that every each team displayed along the way was more than just nice. In a place where everything is a special exception, it was absolutely essential. It was also thrilling! Your contributions made the artwork better. MUCH BETTER! Even the places I couldn’t make it to contributed options, test shots and valuable knowledge which was crucial, especially since we didn’t know if we’d have ANY access to the underground areas! I’m sorry I couldn’t make it to every single site; I wish I had had more time."
"During my visit there were many discussions about “making science cool.” On that subject all I can do is share my own perspective: CERN is poised right on the bleeding edge of human knowledge. It represents the very best of human nature, and to me that is inherently cool. It’s inherently fascinating. The new discoveries you are making are the mile markers of human progress, and that makes all of you trail blazing rock stars."
"Michael & Ruggero Caravita (AEgIS) – thank you to you and your entire team. Their presence made shots I didn’t even have in mind possible! At one point while figuring out how to light the experiment Alex (my producer) turned to me and asked incredulously, “Did they just make lasers for us?” Yes. Ruggero made lasers for us and also stayed late along with the [master student Ola Forslund who side-lines as AEgIS] crane operator so we could block the overhead lights with it! I wish you the best on your kickstarter, please keep us updated."
We'll post an update when the video goes live...
The kickstarter event took place at the ITP of the NYU Tisch School of the Arts over the weekend, and was brilliant... so many interesting projects, such a supportive organization, so many brilliant volunteers, who over the course of an intense weekend transformed the ugly ducklings (the submitted projects) into swans.
Our project is actually a side-line for AEgIS (so it's not an official AEgIS project, since it will take a few years before it could be implemented into AEgIS, but it may well come to play a central role then). The project itself (initially called Ice Drop, since the goal of AEgIs is to drop some very cold antihydrogen) got lots of support, critical ideas, re-design, re-naming and re-branding thanks to the enthusiastic efforts of Ela Madej, Seth Bannon, Jon Laxmi, Max Lawrence, Dana Gilliann Lee, Hellyn Teng and Brendan Reilly.
With a new name (ProjectAntimatter), new design, new video, and some major reworking (taking place), we're now busily preparing to launch on June 15.
Kickstarter is well known for crowd-funding technological projects, but physicists are not yet among their success stories. To change this, and to encourage scientists to formulate their projects in ways that could be attractive to potential supporters, and to explore new ways in which to involve the public in the day-to-day workings of science, kickstarter, together with the Citizen Cyberscience Center and ITP of the NYU Tisch School of the Arts, and supported by the Alfred P. Sloan foundation, are organizing a hackathon at the end of the month of February, 2015, and called for scientists to submit projects.
We submitted a project (called Ice Drop, since the goal of AEgIs is to drop some very cold antihydrogen) on building a set-up to test the idea of laser-cooling of negative ions, in order to later use this technique to cool antiprotons to very low temperatures, and to better measure gravity with antihydrogn atoms. This project is not an official AEgIS project, but rather a long term idea that might at csome point allow AEgIs to take a step to ever colder antiprotons.
Today, we found out that we are among the 15 science projects that will participate in the hackathon! The event page is here.
An article [in Norwegian] by our PhD student Helga Margrete Holmestad on the AEgIS experiment at CERN. Aftenposten is one of the largest newpapers in Norway.
Today, the Swiss radio RSR broadcast a program called "Crowdcrafting... ou la science citoyenne" on their science program CQFD, during which our project was covered together with a project by UNOSAT, also at CERN.
To listen to the corresponding segment of the program, here is the link.
The whole program can be listened to here.
The work by the programmers made possible by Socientize a few months ago has now converged, and we now are ready for a beta release. Today, a preview of this release has been sent out to high school teachers from around the world (from Japan , China, Iran, Israel, different countries in Europe to Canada and the USA) in 30 different schools.
This pre-release is geared first to the high school teachers (we've also added links to other educational resources talking about high energy physics) so that they can incorporate the background information and challenges in their teaching activities, perhaps bring their students to work on the data and help us discover it and understand it better, and help us improve the overall project. A sneak preview of the portal is here.
The timing of this release (by chance) coincides with the second round of antiproton annihilation data taking: just last week, we exposed a new set of emulsions with different target materials, and of course, a first look into the data shows that we have no annihilations. We're hard at work trying to figure out what went wrong, and have scheduled a second attempt in 2 weeks time to try again; last night, we did a full scan of the amount of material that our antiproton beam goes through in 2 micron steps, to see exactly how much material we have to leave in their path to slow them down enough to stop just in the top one or two micron of the photographic plate, but not too much that they don't reach it any more. Tricky ;)
Our new data sets with thinned entrance foil now show annihilations in the emulsions! Adding just a few micron of gold foil in front of the emulsion moves the point of annihilation into the metal foil. We're now taking data with a whole range of different foils, from Aluminum to Lead, in which the antiprotons will thus annihilate in the metal foils, just a few microns away from the emulsion tracker. A first look show that we have around 1000 annihilations per foil type to work with.
Today, we have just published the successful outcome of a test of a method to measure a very small deflection (smaller than the thickness of a human hair) of a beam of antiprotons, the antimatter counterpart of the proton. This is achieved by putting arrays of fine slits in the path of the beam (leftmost figure below), allowing only certain trajectories to pass these obstacles and to hit a detector. The arrival point of the surviving antiprotons is recorded with an emulsion detector that, like a photographic film, takes snap-shots of the antiprotons’ annihilation – the process in which antimatter and matter meet and subsequently reform into other particles. An example of such an “annihilation star” can be seen in the figure in the center, below. These arrival positions are then compared to fringes of light produced by the same slits (rightmost figure below) – making it possible to determine the force that deflected the antiprotons. It is interesting that this method, called morié deflectometry, only needs very few particles to work and is therefore ideal for rare particles such as antimatter.
This demonstration results from the effort of an interdisciplinary and multinational group of physicists, combining techniques from different fields of physics. In future experiments, we hope to employ this method to measure the effect of Earth's gravity on antihydrogen, a force that is much smaller that the electromagnetic force measured here.
After the successful web fest [see the blog entry below this one], and the large interest that our ideas garnered, we decided to put in a funding request to Socientize, which works for Citizen Science in Europe, to pay consultants (programmers, communication specialists) to improve on the alpha release, and include the modifications that were suggested to us by the volunteers and the participants in the web fest project.
Today, the happy news is in: we have received funding to take the next step, improve the functionality of the project, ensure that the resulting data can be used directly in producing publishable results, work on the interactivity and provide tools to allow two-way communication between the scientists and the volunteers looking at the data, to keep everybody up to date and involved.
How do you pitch a crowd-crafting idea to a bunch of enthusiastic and expert summer students who have a smorgasboard of possible projects to choose from? With 3 minutes to explain the background, the technique, the idea and make an appeal for volunteers to spend the next 48 hours (from Friday to Sunday) in putting together a prototype, prepare a presentation and compete for an award by Sunday evening at CERN's 2013 web-fest?
In the end, quite a few students, a range of programmers, communicators and physicists, caught the spark and worked really hard to set up a draft design and interface, write a tutorial and make a jab at adding the required functionality, and completed the job in time to present the finished project to all the participants and an international jury! It's all here
It turns out that the project was really succesful, since it was discovered by the social networks and the media, and led to several hundred volunteers immediately exhausting the small data sample that we could provide for these first tests. But this confirmed us in the interest that the public has in participating in analyzing our data, so we are looking into transforming this first test into a full-fledged portal that our emulsion data will be uploaded to.