ALPHA is an international collaboration based at CERN, and whose aim is stable trapping of antihydrogen atoms, the antimatter counterpart of the simplest atom, hydrogen. By precise comparisons of hydrogen and antihydrogen, the experiment hopes to study fundamental symmetries between matter and antimatter.
Members of the ALPHA Collaboration from Canada were recently awarded the NSERC John C. Polanyi Award for their contributions to ALPHA's sucesses in trapping and measuring antihydrogen atoms. The award honours an individual or team whose Canadian-based research has led to a recent outstanding advance in the natural sciences or engineering.
|Some members of the Canadian group at ALPHA|
The Canadian group contributes accross the spectrum of ALPHA's work, but particularly in the areas of electronics and analysis for the annihilation detector, and the development of the microwave system for measuring antihydrogen's ground-state structure. The design and construction of ALPHA-2's atom-trap cryostat was also led by Canadian institutes.
The full Canadian team at ALPHA is Nathan Evetts, Andrea Gutierrez, Prof. Walter Hardy, Mario Michan, Prof. Takamasa Momose, Sarah Seif El Nasr (University of British Columbia), Dr. Timothy Friesen, Dr. Richard Hydomako, Prof. Robert Thompson (University of Calgary), Mohammad Ashkezari, Ryan Dunlop, Prof. Mike Hayden (Simon Fraser University), Dr. Makoto C. Fujiwara, Dr. David Gill, Leonid Kurchaninov, Konstantin Olchanski, Prof. Art Olin, Dr. James Storey, Dr. Simone Stracka (TRIUMF), Chanpreet Amole, Andrea Capra, Prof. Scott Menary (York University).
Prof. John C. Polyani, the Nobel-prize winning chemist for whom the prize is named, welcomed the award, saying
‘’Throughout my career colleagues have assured me that the universe should not exist. Creation produced equal amounts of matter and anti-matter; they should have annihilated one another. Today's prizewinners give us hope that the universe may yet be saved. They have kept anti-matter away from matter for a full 15 minutes. The universe is older than that, so our prizewinners will be back on this stage. Meanwhile we congratulate NSERC for bravely recognizing the best and most basic research, and we applaud our prizewinners for adding an important milestone to the history of science.’’
Physicists have long wondered if the gravitational interaction between antimatter and matter might be different than that between matter and itself. Do atoms made of antimatter, like antihydrogen, fall at a different rate to those made of matter, or might they even fall up -- antigravity? There are many arguments that make the case that the interaction must be the same, but no-one has ever observed what an anti-atom does in a gravitational field - until now.
Today, the ALPHA Collaboration has published results in Nature Communications placing the first experimental limits on the ratio of the graviational and inertial masses of antihydrogen (the ratio is very close to one for hydrogen). We observed the times and positions at which 434 trapped antihydrogen atoms escaped our magnetic trap, and searched for the influence of a gravitational force. Based on our data, we can exclude the possibility that the gravitiational mass of antihydrogen is more than 110 times its inertial mass, or that it falls upwards with a gravitational mass more than 65 times its inertial mass.
Our results far from settle the question of antimatter gravity. But they open the way towards higher-precision measurments in the future, using the same technique, but more, and colder trapped antihydrogen atoms, and a better understanding of the systematic effects in our apparatus.
Read the paper on Nature Communications at http://dx.doi.org/10.1038/ncomms2787
Right now everyone at ALPHA is busy assembly the ALPHA-2 apparatust, the sucessor to ALPHA. The most recent parts to arrive have been the atom-trap cryostat built in TRIUMF in Vancouver, and the new superconducting solenoid, built by Oxford Instruments in the UK and financed by the Danish Carlsberg Foundation. They join the catching trap, designed by the Cockcroft Institute and the existing positron accumulator from ALPHA to make up the complete chain of apparatus being used in ALPHA-2.
The first antiprotons were caught last night in the new ALPHA2 catching trap, the first component of the next generation of the ALPHA experiment to be installed. This is the representation of the first 'hot dump' -- where we release the captured antiprotons, allowing them to annihilate on the surrounding apparatus. The annihilation converts the antiprotons into high-energy charged particles, which are counted by detectors surrounding the apparatus. Because we detect the annihilations at the same time as we release the trap, we can be sure that the antiprotons have been captured in the trap. Read more about the Penning trap in How ALPHA works.
The catching trap, designed in collaboration with staff at the Daresbury Laboratory and the Cockcroft Institute in the UK, will be responsible for cooling 5MeV antiprotons from the AD, and supplying them on demand to the ALPHA2 atom trap, which will be installed later this year. Construction has been taking place at the AD for the last month, and even though there's a long way to go before the apparatus achieves its full potential, this is a big milestone for us at ALPHA.
The construction team at CERN