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Register a new userTowards Measuring the Ground State Hyperfine Splitting of Antihydrogen -- A Progress Report
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We report the successful commissioning and testing of a dedicated field-ioniser chamber for measuring principal quantum number distributions in antihydrogen as part of the ASACUSA hyperfine spectroscopy apparatus. The new chamber is combined with a beam normalisation detector that consists of plastic scintillators and a retractable passivated implanted planar silicon (PIPS) detector.
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The high precision measurement of the hyperfine splitting of the muonic-hydrogen atom ground state with pulsed and intense muon beam requires careful technological choices both in the construction of a gas target and of the detectors. In June 2014, the pressurized gas target of the FAMU experiment was exposed to the low energy pulsed muon beam at the RIKEN RAL muon facility. The objectives of the test were the characterization of the target, the hodoscope and the X-ray detectors. The apparatus consisted of a beam hodoscope and X-rays detectors made with high purity Germanium and Lanthanum Bromide crystals. In this paper the experimental setup is described and the results of the detector characterization are presented.
Antihydrogen, the lightest atom consisting purely of antimatter, is an ideal laboratory to study the CPT symmetry by comparison to hydrogen. With respect to absolute precision, transitions within the ground-state hyperfine structure (GS-HFS) are most appealing by virtue of their small energy separation. ASACUSA proposed employing a beam of cold antihydrogen atoms in a Rabi-type experiment to determine the GS-HFS in a field-free region. Here we present a measurement of the zero-field hydrogen GS-HFS using the spectroscopy apparatus of ASACUSAs antihydrogen experiment. The measured value of $ u_mathrm{HF}$=$1~420~405~748.4(3.4)(1.6)~textrm{Hz}$ with a relative precision of $Delta$$ u_mathrm{HF}$/$ u_mathrm{HF}$=$2.7times10^{-9}$ constitutes the most precise determination of this quantity in a beam and verifies the developed spectroscopy methods for the antihydrogen HFS experiment to the ppb level. Together with the recently presented observation of antihydrogen atoms $2.7~textrm{m}$ downstream of the production region, the prerequisites for a measurement with antihydrogen are now available within the ASACUSA collaboration.
MOSARIX is a collaborative project between three research group in Sorbonne University to build a x-ray spectrometer (2-5 keV) portable to large scale facilities with high efficiency and good resolution. X-ray spectroscopy and coincidences experiment are planned. A prototype with a single HADP crystal with von Hamos geometry has been tested (resolution and efficiency). A fast time and position detector has been realized (patent and publication).We plan to build the spectrometer with 8 HADP (or 4) crystals under Helium atmosphere using a TimePix3 or a CCD camera. MOSARIX is a project of an x-ray spectrometer in the tender x-ray domain (2-5 keV) with high efficiency, allowing performing x-ray emission and coincidences (or covariance mapping) experiments using synchrotron radiation, XFEL, the future installation SPIRAL2/GANIL or CRYRING/FAIR. It involves 2 groups at LCPMR (Francis PENENT and Marc SIMON) and one group at INSP (Dominique VERNHET). The coincidences/covariance measurements will be between x-ray photons and ions or electrons. It would be the first time for such coincidences with energy-resolved photons. The spectrometer will be portable and will be brought to the different large-scale facilities. MOSARIX is a multi-crystal HAPG von Hamos spectrometer optimized for the 2-5 keV photon energy range. Its resolving power E/DE will be 4000. It will be equipped with a fast time and position sensitive detection system, allowing performing coincidences, or with a CCD camera. I. Scientific case and some possible experiments The accelerated development of x-ray sources, as 3 rd generation synchrotrons (and recent upgrades) or free-electron lasers, has opened new opportunities to investigate new phenomena by means of photoelectron and Auger spectroscopy, electron-ion coincidence techniques and x-ray emission. However, several processes of high scientific interests are still hard to measure; some of them require the measurement of photons with high efficiency, high resolution and even sometimes in coincidence mode. This is the purpose of MOSARIX development. As an example, we propose to revisit Resonance-Enhanced X-ray Multiple Ionization (REXMI) 1 with a significant amelioration of the detection of photons, i.e. measuring the photons not only with high efficiency and high resolution but also in coincidence with ions or electrons. This will allow accessing the involved intermediate states and obtaining a clearer image of the dynamic of the multiple ionization process. MOSARIX can also be used for the investigation of very low cross-section phenomena such as attosecond electron dynamics 2 and High-Energy Resolution Off-Resonant Spectroscopy (HEROS) 3,4. X-ray spectroscopy has also proved to be a very powerful tool to investigate quantum dynamics in heavy ions collisions with matter of whatever nature, dilute or condensed 5-7. A
The ASACUSA CUSP collaboration at the Antiproton Decelerator (AD) of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic spectroscopy beamline. We describe here the latest developments on the spectroscopy apparatus developed to be coupled to the antihydrogen production setup (CUSP).
The gravitational acceleration of antimatter, $bar g$, has yet to be directly measured but could change our understanding of gravity, the Universe, and the possibility of a fifth force. Three avenues are apparent for such a measurement: antihydrogen, positronium, and muonium, the last requiring a precision atom interferometer and benefiting from a novel muonium beam under development. The interferometer and its few-picometer alignment and calibration systems appear to be feasible. With 100 nm grating pitch, measurements of $bar g$ to 10%, 1%, or better can be envisioned. This could constitute the first gravitational measurement of leptonic matter, of second-generation matter and, possibly, the first measurement of the gravitational acceleration of antimatter.
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